INDEX 60th Conference on Chemical Research Program ................................................................................................. 1 Welch Conference on Chemical Research 1957-2016 .......................................................................................... 3 Welch Award Recipients 1972-2016 .................................................................................................................... 5 Hackerman Award Recipients 2002-2016 ............................................................................................................ 6 Principal Investigators Listed Alphabetically ....................................................................................................... 7 Abstracts of Current Investigations..................................................................................................................... 12 Publications Reported During 2014-2016 ......................................................................................................... 129
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INDEX
60th Conference on Chemical Research Program ................................................................................................. 1
Welch Conference on Chemical Research 1957-2016 .......................................................................................... 3
Welch Award Recipients 1972-2016 .................................................................................................................... 5
Hackerman Award Recipients 2002-2016 ............................................................................................................ 6
Principal Investigators Listed Alphabetically ....................................................................................................... 7
Abstracts of Current Investigations..................................................................................................................... 12
Publications Reported During 2014-2016 ......................................................................................................... 129
1
THE ROBERT A. WELCH FOUNDATION 60TH CONFERENCE ON CHEMICAL RESEARCH
“FRONTIERS OF IMAGING”
Visualization of Matter through Electrons and Photons
Monday, October 24, 2016 8:30 CHARLES W. TATE, Chair of the Board of Directors 8:35 PETER B. DERVAN, California Institute of Technology, Chair, Scientific Advisory Board 8:40 TRIBUTE TO AHMED H. ZEWAIL SESSION I – VISUALIZING THROUGH ELECTRONS
8:50 GRANT J. JENSEN, California Institute of Technology, Session Leader
9:00 MAJED CHERGUI, Ecole Polytechnique Fédérale de Lausanne “Core-Level Photoelectrons to Visualize Structural Dynamics?”
9:40 Q&A led by Session Leader
9:50 PAUL A. MIDGLEY, University of Cambridge “Visualization Through Electrons in Solid-State and Materials Chemistry”
10:30 Q&A led by Session Leader
10:40 Break
10:55 RICHARD HENDERSON, University of Cambridge ”Single Particle Electron Cryomicroscopy of Biological Macromolecules”
11:35 Q&A led by Session Leader
11:45 LUNCH
SESSION II – VISUALIZING THROUGH PHOTONS
1:15 BENGT NORDÉN, Chalmers University of Technology, Session Leader
1:25 XIAOWEI ZHUANG, Harvard University “Illuminating and Uncovering Cellular Structures Using Single-Molecule and Super-Resolution Imaging”
2:05 Q&A led by Session Leader
2:15 WILLIAM E. MOERNER, Stanford University “Single Molecules as Nanoscale Light Sources for Imaging and as Sentinels for 3D Dynamics”
2:55 Q&A led by Session Leader
3:05 Adjourn
2
Tuesday, October 25, 2016 SESSION III – MATERIALS, BIO-MACHINES AND CELLS
8:00 WAH CHIU, Baylor College of Medicine, Session Leader
8:10 VENKI RAMAKRISHNAN, University of Cambridge “The Use of Recent Advances in Electron Microscopy to Study Ribosome Structure”
8:50 Q&A led by Session Leader
9:00 WOLFGANG BAUMEISTER, Max Planck Institute of Biochemistry “The Challenge of Doing Structural Biology in situ”
9:40 Q&A led by Session Leader
9:50 Break
10:00 XIAOLIANG SUNNEY XIE, Harvard University “Precision Genomics at the Single Molecule Level”
10:40 Q&A led by Session Leader
2016 Welch Awardee Lectures
10:50 RICHARD H. HOLM, Harvard University “Peregrinations in Inorganic Chemistry”
11:20 STEPHEN J. LIPPARD, Massachusetts Institute of Technology “Metal-Mediated Biological Chemistry: Pt, Fe, and Zn”
11:50 LUNCH
SESSION IV – PRIONS, AMYLOIDS AND THE BRAIN
1:00 DONGPING ZHONG, Ohio State University, Session Leader
1:10 CHRISTOPHER M. DOBSON, University of Cambridge “The Amyloid State of Proteins and its Significance in Biology and Medicine”
1:50 Q&A led by Session Leader
2:00 RICHARD A. ANDERSEN, California Institute of Technology “Imaging and Recording Imagined Movements from the Human Brain”
2:40 Q&A led by Session Leader
2:50 Adjourn
3
THE ROBERT A. WELCH FOUNDATION CONFERENCES ON CHEMICAL RESEARCH
1957 – 2016
YEAR PRESIDING CHAIR CONF. NO. CONFERENCE TITLE
1957 P. J. W. Debye 1 The Structure of the Nucleus
1958 P. J. W. Debye 2 Atomic Structure
1959 Henry Eyring 3 Molecular Structure
1960 Roger Adams 4 Molecular Structure and Organic Reactions
1961 C. Glen King 5 Molecular Structure and Biochemical Reactions
1962 Glenn T. Seaborg 6 Topics in Modern Inorganic Chemistry
1963 Henry Eyring 7 Modern Developments in Analytical Chemistry
1964 Wendell M. Stanley 8 Selected Topics in Modern Biochemistry
1965 Arthur C. Cope 9 Organometallic Compounds
1966 P. J. W. Debye 10 Polymers
1967 Henry Eyring 11 Radiation and the Structure of Matter
1968 Roger Adams 12 Organic Synthesis
1969 Glenn T. Seaborg 13 The Transuranium Elements – The Mendeleev Centennial
1970 W. O. Baker 14 Solid State Chemistry
1971 E. J. Corey 15 Bio-Organic Chemistry and Mechanisms
1972 Henry Eyring 16 Theoretical Chemistry
1973 C. S. Marvel 17 Organic-Inorganic Reagents in Synthetic Chemistry
1974 George W. Beadle 18 Immunochemistry
1975 W. O. Baker 19 Photon Chemistry
1976 Glenn T. Seaborg 20 American Chemistry – Bicentennial
1977 Glenn T. Seaborg 21 Cosmochemistry
1978 Henry Eyring 22 Chemistry of Future Energy Resources
1979 W. O. Baker 23 Modern Structural Methods
1980 Henry Eyring 24 The Synthesis, Structure and Function of Biochemical Molecules
1981 W. O. Milligan 25 Heterogeneous Catalysis
1982 C. S. Marvel 26 Synthetic Polymers
1983 E. J. Corey 27 Stereospecificity in Chemistry and Biochemistry
1984 William N. Lipscomb, Jr. 28 Chemistry in Texas: The 30th Year of The Welch Foundation
1985 Paul Berg 29 Genetic Chemistry: The Molecular Basis of Heredity
1986 Norman Hackerman 30 Advances in Electrochemistry
4
YEAR PRESIDING CHAIR CONF. NO. CONFERENCE TITLE
1987 Emil T. Kaiser 31 Design of Enzymes and Enzyme Models
1988 W. O. Baker 32 Valency
1989 Joseph Goldstein 33 Membrane Proteins: Targeting and Transduction
1990 Glenn T. Seaborg 34 Fifty Years with Transuranium Elements
1991 E. J. Corey 35 Chemistry at the Frontiers of Medicine
1992 William N. Lipscomb, Jr. 36 Regulation of Proteins by Ligands
1993 Peter B. Dervan 37 40 Years of the DNA Double Helix
1994 Yuan T. Lee 38 Chemical Dynamics of Transient Species
1995 W. O. Baker Robert A. Laudise
39 Nanophase Chemistry
1996 Norman Hackerman Richard E. Smalley
40 Chemistry on the Nanometer Scale
1997 Glenn T. Seaborg Darleane C. Hoffman
41 The Transactinide Elements
1998 Joseph L. Goldstein 42 The New Biochemistry: Macromolecular Machines
1999 E. J. Corey 43 Synthetic and Biological Chemistry
2000 William N. Lipscomb, Jr. 44 Macromolecular Structures and Function
2001 Peter B. Dervan 45 Chemistry for the 21st Century
2002 Yuan T. Lee 46 Advances in Quantum Chemistry
2003 Norman Hackerman 47 Chemistry in Texas: Fifty Years of The Welch Foundation
2004 Marye Anne Fox 48 Chemistry of Self-Organized and Hybrid Materials
2005 Norman Hackerman Allan J. Bard
49 Charge Transfer at Electrodes and Biological Interfaces
2006 Joseph L. Goldstein 50 Exploring the complexity of Signaling Pathways
2007 Ahmed H. Zewail 51 Physical Biology – From Atoms to Cells
2008 William N. Lipscomb, Jr. 52 Biological Macromolecules: From Structure to Function
2009 Peter B. Dervan 53 Advances in Synthetic Chemistry
2010 Yuan T. Lee 54 Green Chemistry and Sustainable Energy
2011 Peter G. Schultz 55 From Molecules to Medicine
2012 Richard R. Schrock 56 Advances in Transition Metal Catalyzed Reactions
2013 Roger D. Kornberg 57 Large Problems in Life Chemistry
2014 Marye Anne Fox 58 Chemical Education
2015 Joseph L. Goldstein 59 Next Generation Medicine
2016 Ahmed H. Zewail 60 Frontiers of Imaging
5
WELCH AWARD RECIPIENTS 1972 - 2016
1972 Karl Folkers
1974 Albert Eschenmoser
1976 Neil Bartlett
1978 E. Bright Wilson
1980 Karl Sune D. Bergstrom
1981 Paul D. Bartlett
1982 Frank H. Westheimer
1983 Henry Taube
1984 Kenneth S. Pitzer
1985 Duilio Arigoni
1986 George C. Pimentel
1987 Harry G. Drickamer
1988 Richard B. Bernstein
1989 Norman R. Davidson
1990 William von Eggers Doering John D. Roberts
1991 Edwin G. Krebs Earl R. Stadtman
1992 Richard E. Smalley
1993 Gilbert Stork
1994 F. Albert Cotton Jack Halpern
1995 Robert H. Abeles Jeremy R. Knowles
1996 Koji Nakanishi
1997 Ahmed H. Zewail
1998 Pierre Chambon
1999 Richard N. Zare
2000 Sir Alan R. Battersby A. Ian Scott
2001 Roger D. Kornberg
2002 Harden M. McConnell
2003 Ronald Breslow
2004 Allen J. Bard
2005 George M. Whitesides
2006 Daniel E. Koshland, Jr.
2007 Noel S. Hush William H. Miller
2008 Alexander Rich
2009 Harry B. Gray
2010 JoAnne Stubbe Christopher T. Walsh
2011 John S. Waugh
2012 David E. Evans
2013 Louis E. Brus
2014 Robert G. Bergman
2015 Stephen C. Harrison
2016 Richard H. Holm Stephen J. Lippard
6
HACKERMAN AWARD RECIPIENTS
2002 - 2016
2002 Andrew R. Barron
2003 Xiaodong Wang
2004 Jianpeng Ma
2005 Zhijian J. Chen
2006 Paul S. Cremer
2007 Patrick G. Harran
2008 Francis T. F. Tsai
2009 Cecilia Clementi
2010 Kimberly A. Orth-Taussing
2011 Jason H. Hafner
2012 Oleg V. Ozerov
2013 Olafs Daugulis
2014 Benjamin P. Tu
2015 Stephan Link
2016 Christopher J. Ellison
PRINCIPAL INVESTIGATORS 2015 - 2016
7
Abrams John I-1865
Addo-Mensha Alfred K. BS-1779
Ahn Jung-Mo AT-1595
Aiden Erez Lieberman Q-1866
Ally, Jr. William R. AX-1835
Alper Hal S. F-1753
Alto Neal M. I-1704
Alù Andrea F-1802
An Zhiqiang AU-0042
Anslyn Eric V. F-0046
Armstrong Daniel W. Y-0026
Atassi M. Zouhair Q-0007
Bahadur Vaibhav F-1867
Baker Aaron B. F-1836
Balkus, Jr. Kenneth J. AT-1153
Ball Zachary T. C-1680
Bankaitis Vytas A. BE-0017
Bao Jiming E-1728
Bard Allen J. F-0021
Barondeau David P. A-1647
Barrick Jeffrey E. F-1780
Barron Andrew R. C-0002
Bartel Bonnie C-1309
Baughman Ray H. AT-0029
Begley Tadhg P. A-0034
Belkin Mikahil A. F-1705
Benedek Nicole A. F-1803
Bennett Matthew R. C-1729
Bergbreiter David E. A-0639
Bernal Ricardo A. AH-1649
Bevan John W. A-0747
Billups W. E. C-0490
Bittner Eric R. E-1337
Blount Paul I-1420
Borden Weston T. B-0027
Brodbelt Jennifer S. F-1155
Bruick Richard K. I-1568
Burgess Kevin A-1121
Burgess Shawn C. I-1804
Chapman Walter G. C-1241
Chelikowsky James R. F-1837
Chen Banglin AX-1730
Chen Chuo I-1596
Chen Zheng AU-1731
Chen Zhijian J. I-1389
Chiang Cheng-Ming I-1805
Chiu Wah Q-1242
Chook Yuh Min I-1532
Chuang David T. I-1286
Clearfield Abraham A-0673
Clementi Cecilia C-1570
Cobb Melanie H. I-1243
Coffer Jeffery L. P-1212
Coltart Don M. E-1806
Conrad Jacinta C. E-1869
Conrad Nicholas K. I-1732
Contreras Lydia M. F-1756
Corey David R. I-1244
Cowley Alan H. F-0003
Cozzolino Anthony D-1838
Crooks Richard M. F-0032
Cuello Luis G. BI-1757
Dai Pengcheng C-1839
Dalby Kevin N. F-1390
Danuser Gaudenz I-1840
Darensbourg Donald J. A-0923
Darensbourg Marcetta Y. A-0924
Daugulis Olafs E-0044
Davies Bryan W. F-1870
De Brabander Jef K. I-1422
Deberardinis Ralph J. I-1733
DeMartino George N. I-1500
Dias H. V. Rasika Y-1289
Diehl Michael R. C-1625
Dong Guangbin F-1781
D'Orso Ivan I-1782
Downer Michael F-1038
Doyle Michael P. AX-1871
Du Rui-Rui C-1682
Dunbar Kim R. A-1449
Dunning F. Barry C-0734
Echegoyen Luis AH-0033
Ellington Andrew D. F-1654
Ellison Christopher J. F-1709
PRINCIPAL INVESTIGATORS 2015 - 2016
8
Falck J. Russell I-0011
Fan Donglei L. F-1734
Fast Walter F-1572
Findlater Michael D-1807
Finkelstein Ilya J. F-1808
Fitzpatrick Paul F. A-1245
Foster Matthew S. C-1809
France Charles P. AQ-0039
Frantz Doug E. AX-1735
Futreal Andrew G-0040
Gabbaï François P. A-1423
Ganapathy Vadivel BI-0028
Ganesan Venkat F-1599
Gladysz John A. A-1656
Gohil Vishal M. A-1810
Golding Ido Q-1758
Goldsmith Elizabeth J. I-1128
Goodenough John B. F-1066
Gorenstein David G. AU-1296
Grigolini Paolo B-1577
Grishin Nick V. I-1505
Guloy Arnold M. E-1297
Gurha Priyatansh L-AU-0002
Gustafsson Jan-Åke E-0004
Hafner Jason H. C-1761
Halas Naomi J. C-1220
Halasyamani P. Shiv E-1457
Hall Michael B. A-0648
Hardy John C. A-1397
Harshey Raskia M. F-1811
Hart P. John AQ-1399
Hartgerink Jeffrey D. C-1557
Hase William L. D-0005
Hazzard Kaden C-1872
Heller Adam F-1131
Henkelman Graeme F-1841
Henne W. Mike I-1873
Hibbs Ryan E. I-1812
Hilty Christian B. A-1658
Hinck Andrew P. AQ-1842
Hoffman David M. E-1206
Hooper Lora V. I-1874
Hsieh Jenny I-1660
Hsu Julia W.P. AT-1843
Huang Huey W. C-0991
Hulet Randall G. C-1133
Humphery Simon B. F-1738
Hwang Gyeong S. F-1535
Igumenova Tatyana I. A-1784
Iverson Brent L. F-1188
Jacobson Allan J. E-0024
Jayaram Makkuni F-1274
Jiang Jean X. AQ-1507
Jiang Jin I-1603
Jiang Ning F-1785
Jiang Qui-Xing I-1684
Jiang Youxing I-1578
Jianping Jin AU-1711
Johnson Kenneth A. F-1604
Johnston Keith P. F-1319
Jones Richard A. F-0816
Kadish Karl M. E-0680
Kaplan Craig D. A-1763
Keatinge-Clay Adrian T. F-1712
Kerwin Sean M. A-1298
Kiang Ching-Hwa C-1632
Killian Thomas C. C-1844
Kim Nayun AU-1875
Klein Douglas J. BD-0894
Kliewer Steven I-1558
Ko Che Ming A-1358
Kohler Jennifer J. I-1686
Kolomeisky Anatoly B. C-1559
Kono Junichiro C-1509
Korgel Brian A. F-1464
Kouri Donald J. E-0608
Krische Michael J. F-0038
Kürti László I-1764
Laane Jaan A-0396
Lai Keji F-1814
Lambert David L. F-0634
Lambowitz Alan M. F-1607
Landes Christy F. C-1787
PRINCIPAL INVESTIGATORS 2015 - 2016
9
Larionov Oleg V. AX-1788
Latham Michael D-1876
Lee James C. H-0013
Lee Seongmin F-1741
Lee T. Randall E-1320
Lei Xiangyang V-1815
Li Bing I-1713
Li Guigen D-1361
Li Pingwei A-1816
Li Wei C-1845
Li Xiaoqin (Elaine) F-1662
Lichti Roger L. D-1321
Lindahl Paul A. A-1170
Link Stephan C-1664
Liou Jen I-1789
Liu Hung-wen F-1511
Liu Jun AU-1714
Liu Qinghau I-1608
Liu Wenshe A-1715
Liu Xin I-1790
Liu Yi I-1560
Lockless Steve W. A-1742
Lou Jun C-1716
Lovely Carl J. Y-1362
Lubchenko Vassiliy E-1765
Lucchese Robert R. A-1020
Lum Lawrence I-1665
Lumata Lloyd L. AT-1877
Lutkenhaus Jodie L. A-1766
Ma Jianpeng Q-1512
MacDonnell Frederick M. Y-1301
MacMillian John B. I-1689
Makarov Dmitrii E. F-1514
Mangelsdorf David J. I-1275
Manthiram Arumugam F-1254
Marcotte Edward M. F-1515
Marshall Paul B-1174
Marti-Arbona Angel A. C-1743
Martin Caleb D. AA-1846
Martin Stephen F. F-0652
Martinez Elisabeth D. I-1878
Masters Bettie Sue AQ-0012
Matouschek Andreas F-1817
Matsuda Seiichi P.T. C-1323
May Jeremy A. E-1744
Maynard Jennifer A. F-1767
McBride Kevin G-1847
Miljaníc Ognjen Š. E-1768
Milliron Delia J. F-1848
Mills Nancy S. W-0794
Mirzaei Hamid I-1849
Moore David D. Q-0022
Mullins Charles B. F-1436
Musser Siegfried BE-1541
Nam Yunsun I-1851
Narkar Vihang L-AU-0002
Natelson Douglas C-1636
Natowitz Joseph B. A-0330
Naugle Donald G. A-0514
Neumann Oara L-C-0004
Nevidomskyy Andriy C-1818
Nicolaou Kyriacos C. C-1819
Nijhawan Deepak I-1879
Nippe Michael A-1880
Niu Qian F-1255
Nordlander Peter J.A. C-1222
Norgard Michael V. I-1852
North Simon W. A-1405
O'Donnell Kathryn A. I-1881
Olson Eric N. I-0025
Olson John S. C-0612
Omary Mohammad A. B-1542
Onuchic José C-1792
Orth Kim I-1561
Ozerov Oleg V. A-1717
Palmer Jeremy C. E-1882
Pannell Keith H. AH-0546
Pasare Chandrashekhar I-1820
Pasquali Matteo C-1668
Pettitt B. Montgomery H-0037
Phillips Margaret A. I-1257
Poirier Lionel W. D-1523
PRINCIPAL INVESTIGATORS 2015 - 2016
10
Potts Patrick Ryan I-1821
Prasad B. V. Venkataram Q-1279
Prokai Laszlo BK-0031
Pu Han C-1669
Que Emily L. F-1883
Quiocho Florante A. Q-0581
Radhakrishnan Arun I-1793
Raizen Mark G. F-1258
Ranganathan Raman I-1366
Rao Hai AQ-1747
Raushel Frank M. A-0840
Ready Joseph M. I-1612
Reichl Linda E. F-1051
Ren Pengyu F-1691
Rentzepis Peter M. A-1884
Richmond Michael G. B-1093
Rimer Jeffrey D. E-1794
Rizo-Rey Jose I-1304
Roberts Sean T. F-1885
Robertus Jon D. F-1225
Rogachev Grigory A-1853
Romo Daniel A-1280
Rose Michael J. F-1822
Rosen Michael K. I-1544
Rosenbaum Daniel M. I-1770
Ross, Jr. Joseph H. A-1526
Russell Rick F-1563
Sacchettini James C. A-0015
Schmid Sandra L. I-1823
Schuessler Hans A. A-1546
Scully Marlan O. A-1261
Scuseria Gustavo E. C-0036
Segatori Laura C-1824
Serwer Philip AQ-0764
Sessler Jonathan L. F-1018
Shan Libo A-1795
Shaw Bryan F. AA-1854
Shear Jason B. F-1331
Sheldon Matthew A-1886
Sherry A. Dean AT-0584
Shi Xioabing G-1719
Shih Chih-Kang F-1672
Si Qimiao C-1411
Siegwart Daniel J. I-1855
Simanek Eric E. P-0008
Sokolov Alexei V. A-1547
Son Dong Hee A-1639
Songyang Zhou Q-1673
Spudich John L. AU-0009
Stanton John F. F-1283
Stefan Mihaela C. AT-1740
Stender Anthony L-C-0004
Stevenson Keith J. F-1529
Straight Paul D. A-1796
Su Wu-Pei E-1070
Tabor Jeffrey J. C-1856
Tainer John A. G-0010
Tambar Uttam K. I-1748
Tao Yizhi Jane C-1565
Teets Thomas S. E-1887
Terman Jonathan R. I-1749
Thomann Isabell C-1825
Thummel Randolph P. E-0621
Ting Chin-Sen E-1146
Tittel Frank K. C-0586
Tong Qingchun L-AU-0002
Tonzetich Zachary J. AX-1772
Truskett Thomas M. F-1696
Tsai Francis T.F. Q-1530
Tu Benjamin P. I-1797
Tumkur Thejaswi L-C-0004
Urbach Adam R. W-1640
Uyeda Kosaku I-1720
Verduzco Rafael C-1888
Wagner Eric J. H-1889
Walker Cheryl Lyn BE-0023
Wan Yihong I-1751
Wang Dachun L-AU00002
Wang Qinghua Q-1829
Wang Yuhong E-1721
Wang Zhigao I-1827
Watanabe Coran A-1828
PRINCIPAL INVESTIGATORS 2015 - 2016
11
Webb Lauren J. F-1722
Weinberg Steven F-0014
Weisman R. Bruce C-0807
Wensel Theodore G. Q-0035
Westover Kenneth D. I-1829
Wheeler Steven E. A-1775
Whetten Robert L. AX-1857
White Michael A. I-1414
Whitman Christian P. F-1334
Whitmire Kenton H. C-0976
Willson C. Grant F-1830
Wilson Lon J. C-0627
Winter Sebastian E. I-1858
Wolynes Peter G. C-0016
Wood John L. AA-0006
Wooley Karen L. A-0001
Xhemalce Blerta F-1859
Yacaman Miguel Jose AX-1615
Yakobson Boris I. C-1590
Yan Nan I-1831
Yang Ding-Shyue L-E-0001
Ye Jin I-1832
Yeager Danny L. A-0770
Yeh Hsin-Chih F-1833
Yennello Sherry J. A-1266
Yeo Hye-Jeong E-1616
Yu Guihua F-1861
Yu Hongtao I-1441
Yu Yonghao I-1800
Zakhidov Anvar A. AT-1617
Zhang Chengcheng I-1834
Zhang Chun-Li I-1724
Zhang David Yu C-1862
Zhang Junjie A-1863
Zhang Xiuren A-1777
Zhang Xuewu I-1702
Zhang Yan Jessie F-1778
Zhang Renyi A-1417
Zhao John C.-G. AX-1593
Zheltikov Aleksei M. A-1801
Zheng Junrong C-1752
Zho Hongcai A-0030
Zhong Qing I-1684
12
ABSTRACTS OF CURRENT INVESTIGATIONS
The following Abstracts, as supplied by the Principal Investigators in the Research Grant Program, Endowed Chair Program, Miscellaneous Grants, and Other Endowments, describe some of the current research work in chemistry being supported by the Foundation.
13
JOHN M. ABRAMS, I-1865, The University of Texas Southwestern Medical Center. APOPTOSOME CASPASE CONTROL BY Tango7. We screened for substrates that are cleaved by remodeling apoptosomes. One compelling candidate was purified and subsequently identified by mass spectrometry. This candidate corresponds to Glutamine:fructose-6-phosphate aminotransferase (GFAT), the rate-limiting enzyme in glucosamine synthesis. Using validated antibodies, we confirmed that apoptosome-dependent cleavage of GFAT occurs in vivo. Importantly, cleavage of this substrate occurred only in cells that were remodeling and did not occur in apoptotic cells, demonstrating that distinct substrate profiles are indeed coupled to distinct cell fates. We also found that cleavage of GFAT required Tango7 and was observed in precisely the same cells where the apoptosome is known to promote remodeling. To our knowledge, GFAT is the first known substrate to be specifically cleaved by remodeling apoptosomes. In related studies, we cloned and produced recombinant proteins corresponding to the known Drosophila procaspases. These are currently being tested as substrates for reconstituted apoptosomes, using in vitro cleavage of the effector procaspase Drice as a positive control. ALFRED K. ADDO-MENSHA, BS-1779, Texas A&M International University. THE DESIGN, SYNTHESIS, CHARACTERIZATION AND BINDING STUDIES OF MULTIVALENT POLYPRIDINE BASED MACROCYCLIC CARBOHYDRATE RECEPTORS IN AQUEOUS SOLUTIOINS. Synthesized receptors were purified, fully characterized and titrated against selected sugars. The association constants of the interaction between the receptors and monosaccharides determined was in the millimolar range (stronger than that which is observed in nature). Results of these findings will be presented in August at ACS meeting in Boston and the source of funding duly acknowledged. No graduate student was hired during this grant year so the work did not move as quick/efficient as anticipated. A graduate student is currently working on the immunochemical assays with a team of undergraduate students. The interaction with normal and cancerous cells and the ability to discriminate between cells overexpressed with tumor associated carbohydrate antigens is currently underway. A manuscript which summarizes these findings has been drafted and will be submitted.FBE JUNG-MO AHN, AT-1595, The University of Texas at Dallas. TAILORING SMALL MOLECULES TO MIMIC PROTEIN HELICAL SURFACES. In the past year, we have designed and synthesized a number of tris-benzamide analogs as peptidomimetics of BH3 domains of various pro-apoptotic Bcl-2 proteins, and identified a number of potent compounds that showed high potency in inhibiting cell proliferation of prostate cancer cell lines. In the second grant year, we have designed and synthesized new analogs to improve their capability to interact with their targets, anti-apoptotic Bcl-2 proteins. We carried out this task by introducing additional functional groups to explore an auxiliary binding site near the canonical BH3 domain binding site. We have synthesized nearly fifty new compounds, and each of them were characterized by fluorescence polarization assays for determining protein binding affinity and MTT assays for cell growth inhibition. This approach led us to develop tris-benzamide compounds with improved binding affinity and selectivity, and they have demonstrated on-target effects on mitochondria by showing changes in outer mitochondrial membrane potential and activation of caspases. In addition, we have established a synthetic protocol for making the extended biphenyl helix mimetic scaffold and synthesized 16 biphenyl compounds as extended BH3 peptidomimetics. Preliminary biochemical studies of the new extended BH3 peptidomimetics showed that these longer helix mimetics can increase not only binding affinity but also selectivity to their target proteins. This demonstrates that small molecules can be successfully designed to inhibit protein-protein interactions and outcomes of this study may be useful to develop tool compounds to further study biochemical importance of specific protein-protein interactions. EREZ LIEBERMAN AIDEN, Q-1866, Baylor College of Medicine. MAPPING CHROMATIN LOOP DYNAMICS IN DIFFERENTIATING HEMATOPOEITIC CELLS. We have done initial loop mapping in hematopoietic cells and cancers. We have now generated loop resolution Hi-C data on six different hematopoletic cell types and cancers, identifying thousands of loops genome-wide. We have also focused on resolving many tech dev projects proposed by the grant. A. Call loops using Hi-C BLAST. Hi-C BLAST was noted as a "tech dev" project in our original proposal. This is on account of the fact that the use of Hi-C BLAST for hematopoietic cell types requires the ability to perform Hi-C BLAST on small numbers of cells derived from particular cell niches. This year we successfully implemented a Hi-C BLAST protocol that dramatically reduces input cell number requirements. This was achieved by performing all Hi-C steps after biotin pull-down on single stranded DNA vs. double-stranded. B. Call loops on each chromosomal homolog (tech dev). Calling loops in a homolog-specific fashion was noted as a tech dev project. This year designed Juicer, a fully-automated pipeline that allows users with little to no computational background to transform raw sequencing data into genome-wide maps of looping with a single click. Juicer produces the Hi-C file with loops and contact domains automatically annotated, which facilitates the visualization and analysis of the map and its structural features. We published a paper describing Juicer in the journal Cell Systems. Crucially, Juicer can handle homolog-specific loop mapping, which we have confirmed by generating homolog-specific maps of looping in murine cells. C. Determine the anchors of each loop. We have identified the CTCF anchors for several of these samples, and are awaiting results of CTCF ChIP-Seq experiments which allow us to resolve loops in those that remain. D. Partition loops into chromatin hubs using COLA (tech dev). In earlier research, we demonstrated that the Barr body - the inactive X chromosome that is present in females – contains superloops, structures that span as many as 77 million DNA letters. This year, we used COLA to show that the superloops create a hub in which many distant pieces of the X chromosome come together. To do so, we introduced an approach called concatemer ligation assay, or
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COLA, a variant of Hi-C that allows us to track collisions between three or more positions in the genome. COLA made it clear that the superloops were bringing many pieces of the inactive X chromosome together, all at once. This work was published in the Proceedings of the National Academy of Sciences. WILLIAM R. ALLEY, JR., AX-1835, The University of Texas at San Antonio. SYNTHESIS OF LIQUID-CHROMATOGRAPHIC COLUMNS TO ISOLATE GLYCOPROTEINS AND GLYCOPEPTIDES WITH HIGHLY-BRANCHED GLYCANS. In the first year of this grant, we have successfully synthesized a poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolithic liquid-chromatographic column to which anti-human haptoglobin has been conjugated via reductive amination of the amino groups on the protein. The performance and characterization of this column was evaluated using commercially-available human haptoglobin for a column with dimension of 2.1 mm x 50 mm, approximately 10 µg of haptoglobin could be isolated, according to a bicinchoninic acid test (BCA) against bovine serum albumin. Using this column, haptoglobin from clinical serum samples (control, liver cancer, pancreatic cancer, and ovarian cancer, five samples for each cohort) was isolated and pooled according to their pathological condition. The samples were then digested with trypsin, subjected to chemical-charge enhancement to improve the electron-transfer dissociation efficiency of the glycopeptides, and further subjected to tandem mass tagging to allow direct quantitation of the different sample types in a single liquid-chromatographic-mass spectrometric experiment. Using this experimental approach, we can determine 1) determine the amino-acid sequence of a glycopeptide; 2) determine the overall monosaccharide composition of its glycan; 3) determine the site of glycosylation and site microheterogentity; and 4) quantitate glycopeptides in different sample cohorts. Using this approach, we have investigated the haptoglobin glycopeptide with a sequence of NLFLNHSENATAK, which has two sites of glycosylation. We have determined that there are no significant differences for this glycopeptides modified with two biantenarry/disialylated glycans. However, when decorated with one biantenarry/disialylated and one biantenarry/monosialylated, this glycan is elevated in its abundance levels in the pathological samples. Work continues to verify these results. HAL S. ALPER, F-1753, The University of Texas at Austin. DIVERSIFICATION OF BIOLOGICALLY-DERIVED OLEOCHEMICALS THROUGH A COMBINATORIAL APPROACH. This year, we have established new pathways for the discovery of novel biochemistry pathways for oleochemicals. Firstly, we have established a pathway for cyclopropane fatty acids (CPFAs) and products. Specifically, we were able to achieve CPFAs up to 26% of the cellular fatty acid pool, representing a 67% conversion of monounsaturated fatty acid substrates. We have demonstrated over 3 g/L of production in bioreactors which is the highest value ever reported for this type of product. Secondly, we have established pathways for thioesterase function to enable short chain alkanes and lipids. Specifically, we have functionally assembled strains that can produce Caprylic acid (C8:0), Capric Acid (C10:0), Lauric Acid (C12:0), and Myristic Acid (C14:0) products, representing the first time these have been produced in this type of fungal host. Thirdly, we have established an alkane production host that required the deletion of alk1 (YALI0E25982g), alk2 (YALI0F01320g), alk4 (YALI0B13816g) and alk6 (YALI0B01848g) to prevent product re-assimilation and consumption. This year, we have verified that this resulting strain cannot catabolize desired alkane products. Finally, we have finalized initial biochemical pathways to convert existing (and modified) fatty acid pools into respective alkanes, fatty aldehydes, α-olefins, and fatty alcohols. Additional pathway engineering has commenced this year to selectively transfer C16 into available lipid pools through the modulation of activity of native Sctl (YALI0C00209g) and CpFatB2 from Cuphea palustris. Molecular cloning strategies were designed to assemble these pathways combinatorially in the coming year. NEAL M. ALTO, I-1704, The University of Texas Southwestern Medical Center. POST TRANSLATIONAL MODIFICATION OF HOST ENZYMES BY BACTERIAL EFFECTOR PROTEINS. The Linear Ubiquitin chain Assembly Complex (LUBAC) has been the subject of intense investigation not only because it is the only human E3-ligase that catalyzes assembly of head-to-tail linear ubiquitin chains in vivo, but also due to its role in human diseases associated with deadly autoinflammation, combined immunodeficiency, and systemic infectious disease. Despite this knowledge however, the complexity of immune receptors controlled by ubiquitination has precluded detailed biochemical interrogation of the broad range of LUBAC functions. In addition, microbial inhibitors of LUBAC that could clarify these aspects of immunology and host defense against pathogens have not yet been discovered. In our work recently published in the Nature journal Nature Microbiology, we identify two homologous Shigella flexneri Type III Secretion System (T3SS) effector E3 ligases IpaH1.4 and IpaH2.5 that directly interact with LUBAC subunit HOIL-1L (RBCK1) and conjugate K48-linked ubiquitin chains to the catalytic RING-between-RING domain of HOIP (RNF31). Proteasomal degradation of HOIP leads to irreversible inactivation of linear ubiquitination and blunting of NF- κB nuclear translocation in response to TNF, IL-1β, and pathogen associated molecular patterns (PAMPs). These findings explain how Shigella evades a broad spectrum of immune surveillance systems by cooperative inhibition of receptor ubiquitination and reveal the critical importance of LUBAC in host defense against pathogens. In the next year, we plan to solve X-ray crystal structure of this exciting new E3-ligase complex, which will explain precisely how bacteria hijack the ubiquitin conjugation system of mammals and will reveal new leads for antibiotic development against a deadly human pathogen. ANDREA ALÙ, F-1802, The University of Texas at Austin. ENHANCED OPTICAL MAGNETISM AND CHIRALITY IN PLASMONIC METAMATERIALS: STRONG MOLECULAR SENSITIVITY AND BROADBAND, GIANT CIRCULAR DICHROISM. In the third and final year of this effort we have done new progress in advancing optical metasurfaces for chemical related applications, most specifically bio-sensing and optical wave manipulation. First, we have advanced our theoretical understanding of gradient metasurfaces, which is our proposed platform for wave manipulation and biomedical detection. We have applied these advances for metasurfaces for light management, second-harmonic generation and mixing, and to establish hyperbolic propagation on a surface, with exciting applications to enhance molecular emission and light-matter
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interactions. We are particularly excited by the impact of hyperbolic metasurfaces in the context of chemistry-related applications, since they enable unprecedented low-loss radiation and propagation control over a surface, as well as strong, localized light-matter interactions. We have also studied the impact of spatio-temporal modulation on the propagation properties along and across metasurfaces, which opens exciting directions for nanophotonic devices for isolation. Our results have appeared in several peer-reviewed publications, including high-profile papers in Nature and Science journals. We have also continued our work on low-loss materials for nanophotonic applications, including epitaxial materials and highly doped metal oxides. We have continued working on our twisted metamaterial platform for chirality sensing, a concept that has led to a patent application and to further enhanced chirality detection for single molecules. Finally, we have exhaustively explored passive metasurfaces, outlining the fundamental limits and exciting potentials of this technology for optical wavefront control and management. We are excited to continue this work, and steer it to new directions, in our upcoming Welch research proposal. VAIBHAV BAHADUR, F-1867, The University of Texas at Austin. ROLE OF SURFACE CHEMISTRY AND INTERFACIAL CHARGE ON METHANE HYDRATE NUCLEATION. The development of three experimental setups is almost complete. These setups include: 1. A high pressure chemical reactor (100 bar) to study methane hydrate nucleation kinetics. 2. An experimental setup to study nucleation of tetrahydrofuran hydrates. 3. An experimental setup to study influence of surface chemistry on nucleation and liquid-solid interactions. The following fundamental studies have been completed: 1. Electric field/charge-controlled nucleation of hydrates The concept of electro-nucleation' of hydrates was developed. It was demonstrated that electric charges and fields can control and accelerate hydrate nucleation. Experiments with tetrahydrofuran (THF) hydrates reveal that electro-nucleation can reduce the induction (wait) time for nucleation by 100X. The induction time rapidly decreases with increasing voltages, and is on the order of a few minutes at 100 V. Very low currents are sufficient for electra-nucleation. Nucleation promotion is due to bubble formation following chemical reactions at the electrodes. Overall, this work is the foundation for the control and promotion of hydrate nucleation by electric charges, and enables possibilities for instantaneous nucleation. 2. Role of surface chemistry on nucleation As a first step to studying the role of surface chemistry on hydrate nucleation and adhesion, experiments were conducted to study surface chemistry controlled heterogeneous nucleation of ice under static (stagnant water) and dynamic (liquid impact) conditions. These experiments provide insights into ice/hydrate adhesion, by measuring the utility of superhydrophobic surfaces for icephobicity. AARON B. BAKER, F-1836, The University of Texas at Austin. NANODISC-BASED DELIVERY OF MEMBRANE PROTEIN THERAPEUTICS. Creation of nanodiscs encapsulating the insulin receptor, tm-SCF, cKit and syndecan-1. Following extensive optimization studies, we were successful in producing and isolating the insulin receptor (INSR), tm-SCF, cKit and syndecan-1. In addition, we optimized the formation of lipid nanodiscs around these proteins and purified these nanodiscs. We confirmed the formation of the discs using transmission electron microscopy (TEM), dynamic light scattering (DLS) and cryo-electron microscopy. We are working to further purify the discs using size exclusion chromatography. In addition, we created liposomes with these protein embedded in the lipid membrane as an alternative/comparative delivery system. Enhanced angiogenesis using tm-SCF encapsulating nanodiscs and liposomes. We investigated the angiogenic potential of tm-SCF delivered using nanodiscs and liposomes. Endothelial cells were grown in vitro on matrigel and then treated with tm-SCF in solution, or encapsulated with nanodiscs or liposomes. We found that tm-SCF in liposomes had a five-fold increase in activity in inducing angiogenic differentiation in endothelial cells in comparison to tm-SCF alone. In addition, the nanodisc formulation had 2.5-fold more activity in inducing angiogenesis. We plan to extend these studies by mixing the tm-SCF with cKit and delivering these together to increase its activity in nanodisc and liposomes. Membrane protein therapeutics delivered in alginate-based hydrogels for enhanced angiogenesis and wound healing. We have optimized the delivery of transmembrane proteins including syndecan-4 and glypican-1 in liposomes using an alginate-based hydrogel for sustained release. These treatments were tested in a hind-limb ischemia model and a wound healing assay in diabetic mice. KENNETH J. BALKUS, JR., AT-1153, The University of Texas at Dallas. ZEOLITE ENCAPSULATED METAL COMPLEXES. During the most recent funding period we made progress on the synthesis and modification of zeolitic materials including metal organic frameworks (MOFs) and mesoporous silica based molecular sieves. We have employed solvent assisted linker exchange (SALE) to prepare host-guest complexes as well as thin films. This includes small molecules, metal complexes and enzymes. We have also explored the synthesis of nanoscale wrinkled mesoporous silica (WMS) and organosilicas (PMO). The unique pore structure enables fast diffusion which we have exploited in both catalysis and drug delivery applications. The WMS particles have been functionalized with metal ions, metal complexes and small molecule binding moieties. The WMS materials have also been coated on magnetic nanoparticles creating core shell composites. The WMS nanoparticles have also been incorporated into polymers as films and nanofibers prepared by electrospinning. Layered metal oxide nanofibers were also intercalated with quantum dots, imparting unique electronic properties.
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ZACHARY T. BALL, C-1680, Rice University. NEW STRATEGIES FOR CATALYTIC BOND FORMATION. Our laboratory continues efforts to merge synthetic chemistry with biological tools to create fundamentally new solutions to chemical problems. During this period, the group reported (J. Am. Chem. Soc.) a new research direction: a histidine-directed method for direct modification of the backbone amide bonds of peptides and proteins. The method uses simple boronic-acid reagents and copper catalysis under mild conditions. While many methods for side-chain modification exist, this is the first report of backbone amide modification in such complex polypeptides. Current efforts include mechanistic studies into the reactivity, as well as the design of reagents that enable photocontrol over protein folding and/or splicing. Continuing applications of rhodium-catalyzed protein modification developed in previous grant periods, we used (Angew. Chem. Int. Ed.) proximity-driven modification to identify an unknown small-molecule binding site on STAT3. This novel binding site has medicinal relevance, as a lead compound that we designed and synthesized to target this binding site exhibits anti-leukemia activity in mouse models of human disease. In the course of these efforts, we developed and published new methods to visualize chemical protein modifications as well as a new class of time-gated turn-on dyes for protein imaging. Recently, rhodium-catalysis studies led to the development of fluorescence methods to quantify the in vivo stability of rhodium complexes (under review). The stability of transition-metal complexes in living cells has traditionally been challenging to assess, but insights gleaned from this fundamental study have now allowed the design of more stable complexes with 10-fold better anti-leukemia potency, compared to our published first-generation inhibitors. JIMING BAO, E-1728, University of Houston. UNDERSTANDING NANOCRYSTALLINE CoO AS AN EFFICIENT PHOTOCATALYST FOR SOLAR WATER SPLITTING. • Developed optical spectroscopic techniques to identify cobalt oxides. Specifically, we used Raman scattering and Fourier transform infrared spectroscopy (FTIR) to systematically measure the vibration spectra of CoO and Co3O4. Our results show that optical spectroscopy is more sensitive than X-ray, and the results help establish Raman and FTIR standards that can be used by the community to precisely identify and distinguish the types of cobalt oxides. This work is published in J. Phys. Chem. C. • Measured electron affinity and Fermi level of CoO using Kelvin probe and ultraviolet photoemission spectroscopy (UPS), found that two methods give us different answers. We are investigating this discrepancy. The goal of this measurement is to determine the positions of conduction and valence band edge positions of CoO with respect to water redox potentials. This information is essential to the understanding of photocatalytic water splitting. • In collaboration with Rice colleagues, we identified an efficient electrocatalyst FeMnPO. It can do both hydrogen and oxygen evolutions with very low overpotentials. We also demonstrated photoelectrochemical oxygen evolution by coating it on TiO2 nanorods. We are currently performing additional measurements and try to finish it in a few weeks. • In collaboration with Rice colleagues, we demonstrated highly efficient hydrogen evolution electrochemical catalysts. The work on VS2 is now published in Advanced Materials. The work on Co decorated graphene is published in Nature Communications. DAVID P. BARONDEAU, A-1647, Texas A&M University. FLUORESCENT PROBES FOR INTERROGATING Fe-S CLUSTER TRANSFER CHEMISTRY. Fe-S clusters are essential protein cofactors that are required for hundreds of proteins or enzymes that have critical cellular functions. A conserved biosynthetic pathway is responsible for synthesizing and delivering [2Fe-2S] and [4Fe-4S] clusters to apo target proteins. We developed a fluorophore labeling approach that allows the cluster content of a labeled Fe-S protein to be specifically monitored in the presence of additional chromophores and Fe-S proteins. Using this approach, we were able to determine the monothiol glutaredoxin functions as an obligate intermediate [2Fe-2S] cluster carrier between the assembly complex and multiple classes of terminal target proteins. This manuscript has been submitted to ACS Chemical Biology. In addition, we were able to show that the dithiol glutaredoxin does not function as an intermediate carrier protein and, instead, may serve a Fe-S cluster storage role. We have prepared a manuscript describing these results for Biochemistry. We have also determined the first crystal structure of the structural core of the eukaryotic Fe-S assembly complex. The structure reveals a shocking new architecture that provides a framework for understanding interactions with other Fe-S assembly components, elucidating mechanistic details of eukaryotic Fe-S cluster biosynthesis, and clarifying how defects in Fe-S cluster assembly lead to human disease. This manuscript is being prepared for Nature. JEFFREY E. BARRICK, F-1780, The University of Texas at Austin. COMPARING THE CHEMICAL UTILITY OF ALTERNATIVE GENETIC CODES. With respect to Objective 1, deeper characterization of the TEM-1 amber scanning library by Sanger sequencing revealed systematic synthesis errors (insertion of duplicated sequences in ~30% of clones), making complete TAG-scanning mutagenesis of TEM-1 unfeasible. In lieu of examining every nonstandard amino acid (nsAA) substitution, we now plan to systematically construct and examine a subset of substitutions that are most likely to be chemically interesting. For this goal, we have developed in silico protocols using the molecular modeling package Rosetta to predict the energetic effects of nsAA substitutions in TEM-1. Sets of non-destabilizing nsAA substitutions will be constructed to test our hypothesis about how new post-translational modifications (PTMs) evolve for protein regulation. With respect to Objective 2, we have completed the parallel evolution of 576 T7 phage populations in the presence of 6 different expanded genetic codes for a total of 1000 hours on solid media. Final metagenomes of these populations revealed hundreds of substitutions per population across all six treatments, including >1000 mutations to TAG leading to nsAA incorporation. Initial analysis of these data revealed significant differences in how each nsAA
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evolved to permeate the T7 proteome. We are currently characterizing the phenotypic effects of many of these nsAA mutations and using Rosetta modeling to examine their molecular consequences with respect to protein stability and structure. In addition, we completed work examining the ability of nsAA substitutions in E. coli RNA polymerase to generate resistance to the antibiotic rifampicin. We identified mutants with nsAA substitutions at known resistance-generating residues, as well as other mutants only accessible with the new genetic paths and side chains in expanded genetic codes. Finally, we have taken advantage of our involvement in an Associating Growth Conditions with Cellular Composition project to examine the biology of post-translational modifications across growth stages in E. coli, and our involvement with the UT Austin iGEM team to develop a standardized plasmid toolkit to inexpensively test nsAA incorporation efficiency. Both of these techniques will be useful for the objectives of this study in years two through three. BONNIE BARTEL, C-1309, Rice University. NOVEL PEROXISOMAL PROCESSES IN PLANTS. Peroxisomes are organelles that sequester various oxidative reactions, thereby protecting cytosolic constituents from oxidative damage. Peroxisomes are essential in plants and humans, but small molecules that specifically modulate peroxisome biogenesis, protein import, or maintenance are lacking. We have developed positive screens for both decreased peroxisome function in wild type and increased peroxisome function in peroxisome-defective mutants. We are exploiting these screens to identify compounds that impair peroxisome functions in wild type or enhance peroxisome functions in various mutant backgrounds. We are screening chemical libraries from the John. S. Dunn Gulf Coast Consortium for Chemical Genomics. We are using the smaller Microsource Spectrum Collection (2000 compounds) for pilot studies and the larger Maybridge HitFinder Collection (14,400 compounds selected for structural diversity) for scale-up. We have identified several peroxisome inhibitors as well as compounds that appear to restore peroxisome function to a peroxisome-defective mutant. We also initiated a related seedling-based screen to identify compounds that impair autophagy, the process by which cells degrade large cellular constituents, including peroxisomes. We are conducting structure-activity assays on lead compounds and exploring candidate target proteins. We expect to uncover new molecular tools with which to elucidate and modulate the biogenesis, function, and turnover of these essential organelles. MIKHAIL A. BELKIN, F-1705, The University of Texas at Austin. MID-INFRARED VIBRATIONAL NANOSPECTROSCOPY IN LIQUID ENVIRONMENT. The Year 1 objectives have been exceeded. We have modified our original proposed approach and focused on operating a standard soft atomic force microscope (AFM) cantilever in a very high bending mode (4th or higher) that can maintain a reasonably high oscillation quality factor in liquid (~10). We have also used a high-index Ge prism for evanescent sample illumination. High refractive index of the prism allowed strong (~2500-times) field enhancement at the prism-sample interface. As a result, we have demonstrated, for the first time, infrared nanospectroscopy of a patterned polymer sample (specifically, PMMA) immersed in D2O in the Amide I and II spectral regions (1500-1700 cm-1). The carbonyl peak of PMMA was clearly observed from samples as thin as 50 nm and nanoimaging with better than 30 nm spatial resolution was demonstrated in D2O. These results are now being prepared in publication. We are also working on the transferring of this technology to Analysis Instruments (Santa Barbara, CA) with the support of a DOE STTR Phase IIb grant. The PI has presented the latest project results in two invited and one plenary talk. In addition, we have extended the functionality of the photoexpansion microscopy to image the distribution of Ohmic heating in infrared metamaterials. Our work has recently been accepted for publication in Nature Communications. Moreover, based on these findings, we developed a novel class of chiral infrared detectors that are sensitive exclusively to circularly polarized light. This work is currently under review in Nature Communications. We have also investigated approaches to build external infrared light modulators using graphene-based metasurfaces (infrared light modulation is a key component of the photoexpansion microscopy technique). The results were published in Nano Letters earlier this year. NICOLE A. BENEDEK, F-1803, The University of Texas at Austin. UNDERSTANDING THE CRYSTAL CHEMISTRY OF Bi-BASED PEROVSKITES. In the final few months of this project, we worked with our experimental collaborators on a joint study involving the layered perovskite Dion-Jacobson phases that were the subject of our first publication from this grant. In that work, we showed that although Bi enhances the polarization in the materials which contain it, the Bi atom is not the ultimate driver of ferroelectricity/acentricity in these Dion-Jacobson materials. We also predicted that several compounds that have previously been synthesized and characterized as being non-polar may actually undergo structural phase transitions to polar structures. Our collaborators were able to synthesize these materials and through careful characterization show that, consistent with our predictions, they actually adopt polar structures. A manuscript reporting these results is currently revision at Advanced Functional Materials. Our work has contributed significantly to the understanding of the crystal chemistry of Dion-Jacobson materials, which have been not been as extensively investigated as other classes of layered perovskites. We are aware of several experimental groups that have begun working on Dion-Jacobson phases in response to our theoretical studies. Overall, in the two years that this grant was active, three papers acknowledging Welch Foundation support were published (including a cover article) and one is in revision. The PI expects an additional one or two publications from students that will also acknowledge Welch support.
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MATTHEW R. BENNETT, C-1729, Rice University. DYNAMICAL CONSEQUENCES OF PROTEIN CHEMISTRY IN SYNTHETIC GENE CIRCUITS. In the past year we have completed a study on how the binding affinity between DNA and sigma factors influence gene network dynamics. We have found that small mutations affecting sigma factor binding can determine how ligand-inducible transcription factors affect transcriptional initiation. Further, we showed that these molecular-level changes can have drastic population-level effects in microbial consortia. This work was published in Science. A second paper on this topic will soon be submitted to Nature Methods. In addition, we have analyzed how different sources of noise influence the dynamics of synthetic gene oscillators. We found that both intrinsic noise (caused by thermal fluctuations of molecules in the cell) and extrinsic noise (caused by macro-scale changes in the environment) influence the frequency and amplitude of genetic clocks. This combined experimental and theoretical work was published in PLOS Computational Biology, and will inform the design of more accurate synthetic genetic clocks for the coordination of gene activity in large-scale cellular populations. In other papers, we further characterized chimeric LacI/GaIR transcription regulators (published in Journal of Molecular Biology), examined computational models of molecular noise in gene networks (published in BMC Systems Biology), determined the how the activation of metabolic genes in yeast depends on the rate of environmental change (published in PLOS Computational Biology). We have also submitted papers on studies that examine how transcriptional timing and periodic fluctuations in temperature influence the regulation and periodicity of genetic clocks (one accepted and one resubmitted in SIAM Journal on Applied Dynamical Systems, one submitted to PLoS Computational Biology). DAVID E. BERGBREITER, A-0639, Texas A&M University. MULTIPHASE MULTICOMPONENT SYSTEMS FOR SYNTHESIS AND CATALYSIS. We published five papers this past year with support from the Robert A. Welch foundation. These five papers included four papers discussing original research and one review. The research papers described results for three topics relating to the use of macromolecules and their phase behavior in synthesis. One was a paper that is the subject of a May 2016 undergraduate honors thesis and describes the use of phase selectively soluble silyl protecting groups and shows that we can use the same hydrocarbon soluble phase handles we use for catalysts to prepare recyclable silyl protecting groups. These groups further act as purification handles for intermediates in synthesis. A second paper highlights the significant solubility gains we can achieve with hydrocarbon oligomers - in this case using these oligomers to make metallophthalocyanines highly soluble in organic solvents where they serve as hydrogen-transfer catalysts for nitroarene reduction. Studies of photo-redox catalysts were reported in two different papers. In the first paper, we described the application of soluble and recyclable polymer-bound organometallic photoredox catalysts to organic synthesis detailing their advantages in terms of recyclability and separation as well as their disadvantages in terms of their limited solubility in the polar solvents commonly used in photoredox chemistry. In the second, we published the first examples of soluble polymer-supported photoredox polymerization catalysts that are easily separated from polymer products. Finally, a review has been accepted and published online that discusses our past work on soluble recyclable Ru metathesis catalysts, placing our results in context, discussing advantages and disadvantages of our approach and of other approaches for immobilizing Schrock or Grubbs' catalysts to either recycle them or to separate catalyst residues from metathesis products. RICARDO A. BERNAL, AH-1649, The University of Texas at El Paso. DECIPHERING THE STRUCTURAL AND FUNCTIONAL BASIS FOR RING SEPARATION IN CHAPERONINS. The failure to properly fold nascent polypeptides in their respective tertiary or quaternary structures leads to impaired physiological functions and can lead to numerous disease conditions. The importance of chaperonins is best exemplified by knock-out experiments revealing that the deletion of the host chaperonin gene is lethal in both bacteria and yeast. Our lab has been able to describe a novel chaperonin protein folding mechanism in a bacteriophage encoded chaperonin that involves ring separation which allows the folding of exceedingly large proteins. A bioinformatics analysis of homologous proteins revealed that the human mitochondrial chaperonin (hsp60/10) also has the capacity to form single ring intermediates and so we have initiated studies to investigate the hsp60/10 protein folding mechanism. Hsp60/10 is a ubiquitous molecular chaperonin that plays a central role in protein folding in addition to a number of moonlighting cellular functions. In spite of its importance, not much is known structurally about the molecular architecture of the human hsp60/10 complex. We are working describe the assembly of the fully functional hsp60/10 multimeric protein complex in multiple conformational states. Three-dimensional reconstructions of individual hsp60/10 particles captured by negative stain electron microscopy have revealed a double-ring tetradecameric hsp60 structure with and without the heptameric hsp10 co-chaperonin. In addition, we identified a single-ring heptameric hsp60 structure bound to an hsp10 heptamer. Collectively these results provide insight into the architecture of hsp60 binding with the hsp10 co-chaperonin from a mixture of conformational states that includes ring separation. Ultimately these results will serve as a foundation for subsequent structural and functional studies to gain a greater understanding of the protein folding mechanism of the human hsp60/10 chaperonin. More importantly, we will better understand the molecular basis for diseases that result from hsp60/10 genetic mutations.
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JOHN W. BEVAN, A-0747, Texas A&M University. STRUCTURE AND DYNAMICS OF PROTOTYPICAL HYDROGEN BONDED AND RELATED INTERACTIONS. A supersonic slit jet, quantum cascade laser spectrometer in two configurations were constructed for the generation of precise experimental data for morphing potentials and for revealing fundamentally new characteristics in isolated prototypical hydrogen bonded and related interactions. A broadband investigation of Ar-NO over ~30 cm-1 was undertaken and successfully completed with 154 transitions recorded of the complex on the continuous wave spectrometer. This investigation was expanded to include the atmospherically relevant H2O-NO species, of which ~20 transitions were observed. The spectrometer was then transitioned to include the components needed for Faraday Rotation Spectroscopy in order to take advantage of the open-shell nature of NO complexes. This new spectrometer proceeded successfully through the initial proof of concept stage for the design. In parallel efforts, the second spectrometer, a pulsed supersonic slit jet, quantum cascade laser spectrometer, was prepared for the initiation of an investigation of OC-DBr. Recently, we introduced the concept of a pairwise canonical potential defined, for a class of molecules, as a dimensionless function obtained from each molecule by a readily invertible algebraic transformation. Differing categories (covalent, ionic, etc.) of representative interatomic interactions with binding energies ranging from 1.01 to 1072.03 kJ/mol were accurately modeled canonically to give a unified perspective in the nature of bonding for the pairwise interactions studied. Explicit generalizations to all pairwise interactions studied, even at the asymptotic limit and extremely accurate strictly Born-Oppenheimer calculations have now been referenced to the simplest molecule, H2
+. Functions associated with the diatomic Virial Theorem were also shown recently to be individually canonical giving further perspectives into the nature of chemical bonding. The corresponding canonical transformations have been shown to have a basis in fundamental molecular quantum mechanics rooted to the Hellmann-Feynman Theorem. Current efforts are underway to extend the canonical transformations to a higher dimensionality. W. E. BILLUPS, C-0490, Rice University. CHEMISTRY OF CARBON NANOMATERIALS. As part of our interest in the functionalization of graphene, we have explored the Birch reduction as a route to the hydrographenes, materials that offer potential applications in numerous areas. The syntheses were carried out using lithium/ammonia as the reducing agent and tert-butyl alcohol as a proton source. A commercial graphite powder was used as the starting material for this study. Defects associated with the starting graphite were removed by heating to 1200 °C. Birch reduction of the resulting graphite gave an unexpected material (hydrographene) that was shown by high-resolution transmission electron microscopy to be replete with dislocations. The starting graphite was regenerated when the hydrographene was heated to 1200 °C. These results are illustrated in the scheme presented below. NMR Analysis by solid-state 13C NMR spectroscopy indicates that after three reductions of the same material, the remaining aromatic rings appear to be interior benzene rings. NMR spectroscopy also offers strong evidence for the presence of small amounts of tert-butyl alcohol and ethanol (workup solvent) that could not be removed in vacuo from the samples. These compounds could be observed to move freely between the layers of the hydrographenes. ERIC R. BITTNER, E-1337, University of Houston. THEORETICAL STUDIES OF ULTRAFAST AND COHERENT CHARGE-SEPARATION DYNAMICS IN ORGANIC PHOTOVOLTAIC SYSTEMS. Our work continues to focus upon the role of electronic coherence in the photodissociation process of molecular excitons into polaron pairs in organic photovoltaic systems. We developed a scattering model for studying the effect of dephasing and relaxation in the electron transfer process through an intermediate bridging system. We showed how non-equilibrium quantum phase-transitions of exciton/polaritons can occur in nanostructure arrays of Ag nano rods can occur under conditions of strong coupling to both the photon field of a driving laser and surface-plasmon modes of the underlying substrate. We show that under precise conditions and nano-rod alignments excitons can undergo spontaneous symmetry breaking to form a quantum fluid with specific radiative signature. We developed a mixed quantum/classical method for simulating the excited state dynamics in organic polymer photovoltaic systems. We show how morphological fluctuations can lead to the ultrafast breakup of photo excitations in to charge-separated electron/hole pairs that are delocalized over multiple molecular units the electron transfer timescales and electronic dephasing rates predicted by the simulations are consistent with those observed in working OPV cells as studied by ultrafast 4-wave mixing methods. We consider how vibrionic cooling affects the formation of polariton BECs in organic cavity devices.
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We gratefully acknowledge the long-term support of our work provided by the Welch Foundation. PAUL BLOUNT, I-1420, The University of Texas Southwestern Medical Center. DETERMINING LIPID PROTEIN INTERACTIONS FOR A CHANNEL GATED BY MEMBRANE TENSION. The MscL and MscS bacterial mechanosensitive channels directly sense and respond to membrane tension. We are in the process of designing experiments that allow us to determine the dynamics of these sensors within the membrane bilayer. We have made advances in determining the influence of specific lipids and protein-lipid interactions on the gating of both MscL and MscS. Dr. Hannah Malcolm, who was directly supported by this grant, generated and screened by patch clamp mutations at several sites within the lipid interface regions from residues 114 to 127, which appear to play a large role in determining channel kinetics and the propensity of attaining an inactive state, suggesting protein-protein and protein-lipid headgroup interactions. This has led to a recently published manuscript in PLoS One. Dr. Malcolm was quite successful and recently secured and initiated a tenure-track position in the Chemistry Department at the University of North Florida. This funding now supports another postdoc, Dr. Jinfeng Teng, who is advancing the studies of protein-lipid interactions to TRPV4, an apparent eukaryotic mechanosensitive channel. Jinfeng is in the process of reconstituting this channel into synthesized lipids. This study will allow the dissection of how lipids interact with this channel and influence its mechano-response. This will allow us to compare and contrast these results with those obtained for the MscL and MscS channels. JENNIFER S. BRODBELT, F-1155, The University of Texas at Austin. FUNDAMENTALS OF PHOTO- AND ELECTRON-BASED ACTIVATION OF IONS IN THE GAS PHASE. The influence of four key factors on the fragmentation patterns of peptides and proteins were examined: i) location of a basic arginine residue site, ii) impact of a fixed charge, iii) conversion of conventional even electron peptides to odd electron peptides by electron transfer, and iv) activation method (collisional versus photoactivation). Two charge tags appended to the N-terminus of peptides modulated the fragmentation pathways in different ways, with one leading to dominant and exclusive formation of N-terminal fragment ions, whereas a quaternary amine charge tag caused cleavage from the peptide terminus to release a mobile proton. The fragmentation patterns of charge-reduced species resulted in exclusive production of c and z ions upon secondary activation of CAD, HCD, or UVPD. Although UVPD is well known to create rich fragmentation patterns for protonated peptides, this was not the case for UVPD of odd electron peptides, and instead the resulting spectra were much simpler and nearly identical to the spectra produced by electron activation (c/z ions). The dominance of the radical-mediated fragmentation pathways underscored the overwhelming impact of the radical site, more-so than the presence of a fixed charge or the type of activation method used. 193 nm UVPD of proteins produced fragment ions in charge states that were consistent with the original protonation sites of the intact protein. Non-basic amino acids such as glutamine, proline, tyrosine, and serine were frequently found as protonation sites. Diverse protein conformations discovered for different protonation schemes via molecular dynamic simulations highlighted the role that charge location played on local structure. The location of positive charge sites was also found to depend on the presence or absence of stabilizing salt-bridges in the gas phase. RICHARD K. BRUICK, I-1568, The University of Texas Southwestern Medical Center. ANALYTICAL APPROACHES TO CHARACTERIZE IRON- AND OXYGEN-SENSING MEHCANISMS GOVERNING CELLULAR IRON HOMEOSTASIS. Following O2 deprivation, mammalian cells employ a hypoxic response pathway to initiate adaptive changes in gene expression. This response is mediated by Hypoxia Inducible Factors 1 and 2 (HIF-1 and HIF-2), heterodimeric transcription factors that affect the expression of hundreds of downstream target genes including several involved in iron metabolism. We have previously identified small molecules that bind directly to a preformed cavity within the HIF-2α PAS-B domain, potently and specifically antagonizing its ability to heterodimerize in vivo. While the fruits of that effort have led to the development of drug candidates currently in clinical trials for the treatment of clear cell renal cell carcinoma, we hypothesized that a natural ligand(s) selectively regulates HIF-2 function in vivo. This grant year, we generated data indicating: (1) HIF-2 can respond to metabolic perturbations in the isoprenoid biosynthetic pathway in an isoform selective manner and (2) that these responses are dependent upon the integrity of the ligand-binding site within the HIF-2α PAS-B domain. A candidate HIF-2α-associated protein has been identified that interacts with HIF-2α in a prenylation-dependent manner. We are now investigating whether this modified protein partner occupies the HIF-2 cavity, thus serving as an endogenous ligand. These studies are essential to our understanding of the HIF pathway and strongly compliment our efforts to identify endogenous metabolites that bind within this pocket. We propose to utilize a variety of biochemical, analytical, and chemical approaches in this effort, as the subject of our recently approved renewal application. KEVIN BURGESS, A-1121, Texas A&M University. LADDER-RUNG MIMICS FOR PERTURBING PROTEIN-PROTEIN INTERACTIONS. To initiate this new effort we are in the process of design and optimization of solution and solid phase syntheses of a series of new chemotypes that may perturb protein-protein interactions in general, and uPAuPAR in particular. An interesting accidental discovery was made in the course of that work, relating to cyclic peptides and cyclic peptide-mimics. Cyclic peptidomimetics are valuable compounds for our purposes and others, for several reasons. Two characteristics of these molecules are particularly desirable: ease of synthesis and conformational rigidity. Lack of flexibility is favored because solution structures may be related to bound structures if the compound is relatively rigid, and because when the compounds bind biomolecules they do so with minimal loss of entropy. Ease of synthesis is enhanced for rings larger than 12-atoms (cyclic tetrapeptides), but conformational rigidity decreases. Consequently, we set out to establish a design sweet-spot representing cyclic peptidomimetics that could be made conveniently, yet retained conformational rigidity. The sweet-spot appears to be 13-ring cyclic
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peptidomimetics like the one shown here. The surprise is that two systems like this, and, contrary to the literature, cyclic tetrapeptides (lacking Pro and Gly) appear to be conformationally homogenous in aqueous solution, and their shapes are easily rationalized via a simple model applicable to all stereoisomers. Full details will be revealed soon. Easier to prepare than cyclic tri- and tetra-peptides, more ridged than 13-membered rings containing other β-amino acids, and adopts stereochemically- tunable homogeneous conformations SHAWN C. BURGESS, I-1804, The University of Texas Southwestern Medical Center. DYSREGULATION OF INTRACELLULAR LIPID SYNTHESIS DURING DISEASE. In the last year we began examining the role of cell signaling pathways in the regulation of hepatic lipid metabolism. mTORC1 is a signaling kinase that is downstream of insulin action and has been proposed to propagate many effects of insulin resistance. We reported that mTORC1 activation suppressed oxidative metabolism in the liver, leading to reduced gluconeogenesis during fasting (Kucejova et al. Cell Report, In Revision). This was opposite to the effect of loss of the insulin receptor and is generally consistent with the putative role of mTORC1 in lipid synthesis. However. mTORC1 activation did not increase liver fat and paradoxically suppressed lipogenesis. Last year at this time we had just generated liver specific raptor LKO (mTORC1 loss of function) mice and crossed them with Pten LKO mice. We examined these mice under high fat and high sucrose diets. In both cases, Pten loss massively induced hepatic steatosis and hepatomegaly. However, double KO mice were protected, indicating that while mTORC1 is not sufficient, it is required for insulin mediated fatty liver. We have now injected these mice with D2O tracer, isolated liver triglycerides and performed 2H NMR on the samples. Analysis is underway and will report rates of lipogenesis, esterification, elongation and desaturation. This data will be the first of its kind to characterize the in viva role of mTOR1C in mediating lipid synthesis by insulin action WALTER G. CHAPMAN, C-1241, Rice University. STRUCTURE AND PROPERTIES OF COMPLEX FLUIDS IN THE BULK AND INTERFACIAL REGIONS. Our molecular density functional theory (DFT) will predict how molecular architecture controls nanoscale structure and therefore macroscopic properties of functional soft materials. The approach describes self-assembly of microscopic building blocks (molecules, colloids, etc.) while offering distinct advantages in considering explicit solvent, trace components, and short-ranged, directional association sites. Research this year has focused on providing insight to challenging systems including properties of hydrogen bonding mixtures, structure of confined patchy colloids, multibody correlations in mixtures of patchy and spherically symmetric colloids, and the effect of surfactant architecture on micellar structure. For mixtures containing water and alcohols, our results bring some consistency between theory / simulation and phase behavior / spectroscopic experiments, but we have identified significant flaws in many simulation water models and are currently using quantum calculations to justify our new model. To allow for more complex associated structures (e.g., hyperbranched polymers), we have developed a new approach to incorporate multibody correlations in statistical mechanics based theory. Extensions to incorporate complex associated structures based on Welch Foundation funding such as multibody correlations, and non-additive interactions are described in the invited review in Advances in Chemical Physics volume 160 (2016) that is included in this report. Research for next year will include models for associating colloids and hydration of electrolytes based on the new approach for multibody correlations, models for swollen micelles, reverse micelles and partitioning of components in block copolymer micelles as well as dendrimers with potential application in drug delivery. JAMES R. CHELIKOWSKY, F-1837, The University of Texas at Austin. SIMULATING DIRECT IMAGES OF THE COVALENT BOND FROM ATOMIC FORCE MICROSCOPY. Our work has focused on computing simulated images of the covalent bond obtained from noncontact atomic force microscopy (nc-AFM). The most difficult problem is that such simulations are computationally intensive and not able to provide a detailed image. We developed an efficient first-principles method for simulating nc-AFM images using a "frozen density" embedding theory. This method reduces the extensive computational load of first
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principles AFM simulations by avoiding consideration of the entire tip–sample system and focusing on the tip alone. We demonstrate that our simulation with frozen density embedding theory accurately reproduces full density functional theory simulations of free-standing hydrocarbon molecules while the computational time is significantly reduced. Our approach is applicable for theoretical imaging applications on large molecules, two-dimensional materials, and materials surfaces. We have used this and related approaches to address some outstanding issues with nc-AFM. For example, nc-AFM employing a CO-functionalized tip displays dramatically enhanced subatomic resolution wherein covalent bonds of polycyclic aromatic hydrocarbons can be imaged. By modeling systems with and without CO functionalization, we proposed a new mechanism to explain the enhanced resolution. In addition, we examined some image anomalies that have been interpreted as a direct image of a hydrogen bond. We demonstrated that such interpretations are incorrect. We find that contrast for the observed "hydrogen bond" feature comes not from the electrostatic character of the bonds themselves, but rather from repulsive tip tilting induced by neighboring electron-rich atoms. While most of our work has centered on molecular imaging, we have also considered nc-AFM images of two dimensional materials such as graphene with and without adsorbates. BANGLIN CHEN, AX-1730, The University of Texas at San Antonio. FUNCTIONAL POROUS METAL-ORGANIC FRAMEWORKS FOR RECOGNITION OF SMALL MOLECULES. With the support of the Welch Foundation, in this grant year we published twenty-three papers in Science, Acc. Chem. Res., Nature Commun., J. Am. Chem. Soc., Prog. Polym. Sci., Energy Environ. Sci., Chem. Commun. and J. Mater. Chem. A etc together with three accepted articles. The most important progress is the realization of a unique microporous metal-organic framework with optimized pores and very specific pore surfaces for highly selective separation of C2H2/C2H4 (Science, 2016. 353. 141). This is a breakthrough in this very important industrial separation through our rational design and control of the pore chemistry and function within porous metal-organic frameworks. We have also realized a flexible microporous hydrogen-bonded organic framework for gas sorption and separation (J. Am. Chem. Soc. 2015, 137, 9963), further paving ways of making of this type of new porous material for energy and environmental science. Through a judicial choice of organic linkers, we have been able to further target porous MOFs with extremely high methane storage and delivery capacities (Energy Environ. Sci, 2015, 8, 2504). We have also realized the first example of polarized three-photon pumped laser in single MOF microcrystal (Nature Communications, 2016. 7, 11087). UTSA-74 is the first structurally characterized porous MOF in which one open metal site can bind two gas molecules, leading to its unique gas separation performance for C2H2/CO2 (J. Am. Chem. Soc. 2016, 138, 5678). Because of our leading status in this very active research field, we have been invited to write a series of review and perspective articles which have been published in (Acc. Chem. Res. 2016, 49. 483), and (Prog. Polym. Sci .2015, 48, 40). I would like to take this opportunity to thank Welch Foundation for the generous and continuous support for my ongoing research. CHUO CHEN, I-1868, The University of Texas Southwestern Medical Center. DEVELOPMENT OF ANTICANCER IMMUNOTHERAPEUTIC AGENTS. We have prepared a series of DMXAA derivatives and tested their ability to active STING. We first found that the claimed activity of 8-MeXAA toward human cells is likely independent of the STING pathway. We next confirmed that, at high concentrations, DMXAA could activate mouse STING but not human STING. Additionally, S162A mutation indeed rendered human STING responsive to DMXAA, but the effect was weak. Based on the crystal structure of DMXAA/mSTING, incorporation of a polar functional group to the 2-position of DMXAA should help establish a polar-polar interaction with S162 of hSTING and thus restore activity. However, we found that rather than altering species selectivity, such modification resulted in attenuated activity toward mSTING. Controlling experiments suggest that the loss of activity originated from an unfavorable polar-polar interaction, illustrating the importance of installation of a proper functional group at this position. Given that DMXAA is only active toward mSTING and genetically engineered hSTING at micromolar concentrations, we set out to explore the potential of improving its potency through dimerization. As part of the studies to identify the strategy to link the DMXAA fragments, we investigated the effects of installation of an ct-substituent group onto DMXAA. Although an early literature report suggested that methylation at this position can be tolerated, we found that α-methyl-DMXAA is significantly less active than DMXAA. We further created a diastereomeric mixture of DMXAA dimers but found it inactive toward both mSTING and hSTING. Because of the poor correlation between the predicted structure–activity relationship based on DMXAA/mSTING co-crystal structures and our data, we suspect that the immunostimulatory activity of DMXAA is not STING-specific. We will thus turn our attention to improving potency and pathway selectivity in the next grant year. Future work will include combinatorial structural modification strategies. ZHENG CHEN, AU-1731, The University of Texas Health Science Center at Houston. MOLECULAR MECHANISMS OF ACTION OF CLOCK-MODULATING SMALL MOLECULES. In a breakthrough study, we successfully identified protein targets of Nobiletin/CEM5 (NOB), a clock-enhancing polymethoxylated flavonoid showing robust clock-dependent metabolic efficacy (He et al.. Cell Metabolism. 2016). Several lines of evidence identified a family of nuclear hormone receptors RORs are direct targets of NOB. Most importantly, we conducted saturation binding experiments and measured Kd by Scatchard plots. Using competitive filter binding assays, we showed that RORs directly interact with NOB, with Kd values in the range of 10-7 – 10-9, depending on isoforms. RORs play important roles in immunity, circadian rhythms and metabolism, and our studies reveals a natural agonist for this multifunctional protein family. The landmark finding received much media attention, and opens up exciting venues for further biochemical and functional studies. The Welch renewal proposal has been approved. Many thanks. Two other studies are being completed. First, using both biochemical and next-generation sequencing approaches, we identified
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the mitochondrial electron transport chain (ETC) as a key cellular target of NOB in skeletal muscle of aged mice. Corresponding to elevated O2 consumption and energy expenditure, we showed that ATP formation was greatly increased as a result. Interestingly, in a collaborative effort. we also demonstrated induction of ETC supercomplex formation in response to NOB, suggesting a novel molecular mechanism of NOB-mediated metabolic protection. Second, in a collaborative effort, another natural flavonoid Myricetin was found to also enhance endurance capacity and mitochondrial function. Biochemical mechanistic studies suggested that the key mediators for Myricetin function are SIRT1 and PGC-1alpha. ZHIJIAN J. CHEN, I-1389, The University of Texas Southwestern Medical Center. BIOCHEMICAL MECHANISM OF MAVS ACTIVATION BY PRION-LIKE POLYMERIZATION. MAVS is a mitochondrial outer membrane protein essential for innate immune defense against RNA virus infection. MAVS forms self-perpetuating prion-like filaments in cells infected with RNA viruses, which activate the RIG-I family of receptors. The N-terminus of RIG-I contains tandem CARD domains, which interact with the CARD domain of MAVS, triggering the rapid formation of a helical filament of MAVS CARD. MAVS filaments recruit the TRAF family of ubiquitin E3 ligases, which catalyze K63 polyubiquitination that activates the kinases IKK and TBK1, which in turn activate the transcription factors NF-κB and IRF3, respectively, to induce typed interferons and other inflammatory cytokines. MAVS is also phosphorylated by IKK and TBK1, and this phosphorylation is important for the recruitment of IRF3 to the MAVS filament, thereby 'licensing' IRF3 for phosphorylation by TBK1. The mitochondrial membrane localization of MAVS is essential for its polymerization and activation. We have established an in vitro system in which MAVS in isolated mitochondria can be activated by RIG-I and K63 polyubiquitin chains. We are now using this reconstituted system to dissect the role of mitochondria in MAVS activation. After MAVS activates the downstream signaling cascade, the MAVS aggregates are cleared through an unknown mechanism. Our recent studies suggest that autophagy plays an important role in the clearance of MAVS aggregates. Recent studies also show that recognition of self RNA and DNA by the RIG-I – MAVS and cGAS-STING pathways, respectively, causes autoimmune diseases such as Aicardi-Gourtieres syndrome (AGS) and systemic lupus erythematosus (SLE). Through understanding the mechanisms that regulate the assembly and clearance of the MAVS filaments in response to infectious agents and endogenous danger signals, we hope to develop new strategies to prevent and treat infections and autoimmune diseases. CHENG-MING CHIANG, I-1805, The University of Texas Southwestern Medical Center. MECHANISTIC ACTION OF BET COMPOUND INHIBITORS IN CANCER THERAPEUTICS. For Objective I, we showed that Brd4 binding to global acetylated chromatin is phosphorylation-dependent and requires its bromodomains. Moreover, Brd4 binding to acetylated chromatin also occurs in a gene-specific manner, as illustrated by our analysis of p53, c-Myc, and c-Fos gene loci. Importantly, binding of Brd4 to acetylated chromatin globally and locus-specifically is both inhibited by Hit-G and Hit-I compounds in a dose-dependent manner. At a specific window of compound concentrations, we detected pathway-specific inhibition by Hit-G and Hit-I compounds in different human cell lines, highlighting the potential for developing drug inhibitors targeting specifically the phospho region of Brd4 in cancer therapeutics. For Objective II, we extended our previous studies of p53 target gene transcription to human papillomavirus (HPV) E2-regulated viral and cellular gene transcription and found that addition of Hit-G compound in keratinocyte culture medium significantly inhibits differentiation-induced MMP-9 gene expression potentiated by the cancer-associated HPV E2 protein. Concurrent analysis of MMP-9 gene regulation using chromatin immunoprecipitation (ChIP) for factor binding, quantitative RT-PCR for RNA level, and Western blotting for protein expression, we also uncovered the molecular mechanism for regulating MMP-9 gene transcription by switching the JunB and JunD members of the AP-1 family proteins by c-Jun and also by relocalization of NFkB from the cytoplasm to the nucleus for binding to their respective cognate sequences upon differentiation. Binding of viral and cellular factors to the MMP-9 promoter-proximal region depends on Brd4 and is selectively regulated by compounds targeting phosphorylation of Brd4. WAH CHIU, Q-1242, Baylor College of Medicine. STRUCTURAL STUDIES OF VIRUS BY Cryo-EM. We have made exciting progress in using cryoEM for structural determination of virus particles. First, we developed a rigorous modeling protocol, which meets simultaneously the constraints of fitting to the cryoEM map density and optimizing to the stereo-chemistry of the protein components. This algorithm was implemented in Phenix, a popular X-ray crystallography software package, so that our procedure can be adopted readily by other investigators in structural biochemistry. This procedure is applied to the new 3.3Å resolution cryoEM structure of P22 bacteriophage with full atomic details. Second, we evaluated the use of cryo-electron tomography to determine virus structures beyond the current resolution limit. Such an approach is useful to study virus particles, which have variable conformations of protein components within and/or among virus particles. However, if the defocus of each micrograph in the tilt series is not accurately determined and properly corrected, the resolution will be limited. We implemented a new algorithm for the image defocus detection and correction for tilted specimen images within the EMAN2 software, which is publicly accessible. Applying this procedure to the cryo-electron tomograms of enveloped virus VEEV, we are able to demonstrate the structure resolution improvement up to the 4/5 Nyquist frequency limit of the direct electron detector used for the image data acquisition. Third, we have been interested to study structures of viruses inside their host cells, and their interactions with the subcellular components, in cryo-electron tomograms of virus infected cells. A challenge is to annotate the crowded subcellular components in the cell tomograms correctly. So far, it is done manually and subjectively. We carried out an analysis and demonstrated the statistical uncertainty using manual annotation. We suggest the necessity of multiple manual annotations or development of automatic feature identification algorithms to assure accuracy and reproducibility for identifying subcellular features before and after virus infection.
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YUH MIN CHOOK, I-1532, The University of Texas Southwestern Medical Center. MECHANISMS OF NUCLEAR EXPORT CARGO DISSOCIATION. Results from previous years of the grant show that Msn5 does not use RanBP1 for cargo dissociation. The exportin uses an entirely different mechanism of cargo dissociation than other known exportins, possibly nucleoporins for dissociating cargos. While we express multiple fragments of the large nucleoporins to probe for interactions with Msn5, we also started studying the release of nuclear export signals (NESs) or cargos from the general nuclear exporter CRM1. We have quantified nuclear export activities of more than twenty diverse NESs in HT1080 cells and measured dissociation constants (KDs) of the same NESs by differential bleaching monitored by on a microscale thermophoresis instrument. We observed a linear relationship of CRM1-NES binding strengths and nuclear export activities when NESs binds CRM1 in the KD range of 2 nM to 20 µM. NESs that bind weaker shows no nuclear export activity in cells. Interestingly, NESs that bind CRM1 at the very high affinity range (KD < 7 nM) have poor nuclear export capability in cells. One of the super high affinity NESs, the NES of protein NS2 of the minute virus of mice (MVM-NS2NES; KD 2 nM), is able to dissociate NESs that bind CRM1 in the physiologically linear range. We hypothesize that the severe decrease in nuclear export activity of the super-tight NES sequences are due to low dissociation rates that prevent multiple rounds of nuclear export by CRM1. We will measure koff of CRM1-NESs by SPR. DAVID T. CHUANG, I-1286, The University of Texas Southwestern Medical Center. MITOCHONDRIAL SIGNALING BY REVERSIBLE PHOSPHORYLATION. The long-term goal of his investigation is to test the central hypothesis that mitochondrail branched-chain α-keto acid dehydrogenase kinase (BDK) is a drug target to restore branched-chain amino acid (BCAA) degradation in metabolic disorders. During this grant year, we isolated a novel BDK inhibitor BT2 (3.6-dichlorobenzo[b]thiophene-2-carboxylic acid) with excellent metabolic stability (t1/2 = 720 mm). Oral dosing of BT2 at 40 mg/kg/day significantly reduced BCAA concentrations and improved glucose tolerance and insulin sensitivity in Zucker obese rats and diet-induced obese mice. Moreover, the lean mass is elevated in these animals with drastically reduced hepatic steatosis. These findings strongly support the therapeutic potential of BDK inhibitors for the treatment of obesity and type 2 diabetes. In collaboration with with Dr. Yibin Wang at UCLA, we also found that the BCAA catabolic pathway is impaired in the mouse failing heart. The suppression of BCAA flux is regulated by Kruppel-like factor 15. The resultant accumulation of branched-chain α-keto acids (BCKA) in the failing heart leads to elevated superoxide production, oxidative injury and other aberrant metabolic changes. Treatment of the mouse model during heart failure with the BDK inhibitor BT2 significantly preserves the cardiac function. This study is the first demonstration that the BCAA/BCKA accumulation contributes to the progression of heart failure and that mitochondrial BDK can serve as a potential therapeutic target for the disease. ABRAHAM CLEARFIELD, A-0673, Texas A&M University. METAL PHOSPHONATES AS CRYSTAL ENGINEERED SOLIDS AND PLATFORMS FOR DRUG DELIVERY. We have previously shown that many compounds such as silanes, epoxides, isocyanates and phosphates can bond to the surface of the Zr and tin phosphates. In drug delivery for cancer treatment the drug is placed between the ZrP or SnP layers but the surface needs to be treated to prevent the drug from prematurely existing. This is done by placing high carbon PEGs on the surface. In carrying out this reaction it was determined by extremely searching nuclear magnetic resonance (NMR) studies, that the PEGs were bonded to the surface but the tails were able to enter between the layers. Further studies showed that if the interlayer space were filled with the drug, the PEG tails could not enter between the layers. This required about 35% by weight to be the drug. This is a very large dosage that was found to exit over a two week period within the cancer with high level of destruction of the tumor. A second development is that we were able to create a MOF (Metal Organic Framework) onto the surface of zirconium phosphate. These compounds exhibit ultra-high porosity with enormous surface areas. These compounds have potential as storage media for gases, for gas separations, catalysis, drug delivery and many other projected uses. The MOF can be placed on these surfaces in a layer by layer procedure. This permits us to prepare MOFs that cannot be prepared by solution methods. Because we can change the metal or the ligand each layer may be different than the preceding one. Thus a whole new chemistry may result. This first MOF that was built on the zirconium phosphate layers by us was known by previous solution preparations. However, we were able to show that our mounted MOF provided a higher yield of product in a catalysis reaction, together with higher rates of conversion and the catalyst was easily recovered for reuse nine (9) times. A paper on this subject was accepted in the ACS journal Inorganic Chemistry. CECILIA CLEMENTI, C-1570, Rice University. MAPPING THE FREE ENERGY LANDSCAPE OF PROTEINS BY COMBINING THEORY AND EXPERIMENT. 1) Adaptive sampling for the efficient exploration of the configurational space of complex biomolecules. We have used recently proposed mathematical techniques, in combination with ideas previously developed in our group, to define optimal strategies to extract the slowest directions of motion on-the-fly from a set of short, non-equilibrium molecular dynamics simulations, and use this information iteratively to estimate the equilibrium distribution and kinetics properties of the system. One paper is published and several are in preparation. 2) Methodologies to rigorously incorporate experimental data and fine resolution simulation results into the definition of coarse-grained model for biomolecular systems. We are using Bayesian inference and statistical mechanics to establish a theoretical framework to integrate all the available information for a given macromolecular process over a multiple range of time- and length-scales, to obtain a global and quantitative understanding of the process. We are currently
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testing the procedure on simple systems, but also already applying it to the characterization of the thermodynamics and kinetics of large complexes that cannot be studied by any single experimental or computational technique alone. Several papers are in preparation. MELANIE H. COBB, I-1243, The University of Texas Southwestern Medical Center. REGULATORY AND CATALYTIC PROPERTIES OF MAP KINASE CASCADES. The structure of an ERK2 mutant, E322K, associated with human cancers has revealed and promises even more insight into ERK biochemistry than we anticipated. The mutation disrupts the docking site on ERK2 for protein substrates. We have now shown by mass spectrometry and in cell assays that the protein kinase Rsk2, among the most significant of ERK2 substrates, is no longer recognized by this mutant, in spite of the fact that many other proteins that are thought to use that docking site are activated normally. The MAPK insert region is more flexible in the mutant and results in enhanced interactions with certain substrates. The activation loop is no longer bound to the C-terminal domain, as it is in the low activity wild type structure. This observation supports the conclusion that the docking site and the activation loop are energetically coupled. We have now shown that the activity of the protein is increased in cells and that it is localized differently. We are collaborating with a group at Princeton to examine the effects of this mutation in a developmental system. These findings cement the concept that communication from the substrate docking site affects ERK2 activation, ERK2 autoactivation, the ERK2 active site, and ERK2 dimerization. We also evaluated ERK2 activation loop plasticity by studying the effect of phosphorylation of T188 of ERK2 on its activity and DNA binding. This study has been published. We have used overlapping arrays of peptides encompassing the WNK1 N-terminal domain to identify two peptides that bind p85 both of which contain Akt phosphorylation sequences. We are determining which of these two peptides binds more tightly for structural analysis. JEFFERY L. COFFER, P-1212, Texas Christian University. PROBING NEW CONFINED NANOSTRUCTURES AND ASSOCIATED INTERFACES WITHIN TUNABLE SILICON NANOTUBES. In this first year of our most recent project, we have made significant progress in the demonstration of nanostructure size control for organometal perovskite phases composed of methylammonium lead iodide (CH3NH3PbI3) formed inside porous silicon nanotubes with a Si wall thickness of 10 nm and possessing inner diameters of either 30 nm, 70 nm, or 200 nm. After structural characterization, the photophysical properties of these perovskite nanostructures, in terms of optical absorption and photoluminescence as a function of temperature, were evaluated. Spectroscopic comparisons with more bulk-like one-dimensional microwires of the same composition were also carried out. Multiple interesting new phenomena were observed for these nanostructures. First, both photoluminescence (PL) and optical absorption spectra clearly indicate a strong correlation between the emission spectra (PL) and the onset of the absorption for a given nanostructure. The spectra (both PL and absorption) of the 200 nm perovskite loaded SiNTs are similar to that of the bulk-like perovskite microwires, with a slight shift toward the blue of about 5-10 meV, and an additional blue shift of about 10-15 meV for the 70 nm perovskite loaded SiNTs. These results can be attributed to quantum size effects in these 1 D perovskite nanorods, but can also be influenced by the large stress at the silicon-perovskite interface and a larger surface-to-volume ratio for CH3NH3PbI3 formed within the smaller SiNTs. Second, in the temperature-dependent PL spectra for the 70 nm and 30 nm size perovskite nanostructures, there is clear evidence for a size-dependent suppression of the tetragonal to orthorhombic phase transition of the CH3NH3PbI3 with decreasing temperature. The mechanistic origins of these unique size dependent phenomena are currently under detailed examination in our laboratories. DON M. COLTART, E-1806, University of Houston. NEW CATALYTIC ASYMMETRIC CARBON-CARBON BOND FORMING METHODS. The focus of the grant proposal in question is the development of new catalytic asymmetric methods using aza- and nitrosoalkene substrates. We have found that the simple combination of Grignard reagents – the most readily available and common of all organometallic reagents - and α-epoxy N-sulfonyl hydrazones results in the highly (up to >25:1) syn-selective formation of β-hydroxy N-sulfonyl hydrazones having up to all-carbon α-quaternary centers. This transformation is remarkable in its ability to incorporate an unprecedented range of carbon-based substituents, including 1°, 2°, and 3° alkyl, alkenyl, aryl, allenyl, and alkynyl. This has not previously been possible via a single method in the context of α-carbonyl-based functionalization. Subsequent hydrolysis of the β-hydroxy N-sulfonyl hydrazone products produces the corresponding β-hydroxy ketones. In addition to hydrolysis, the (β-hydroxy N-sulfonyl hydrazone products are poised to undergo numerous different known synthetic transformations via well-established chemistry, giving rise to a wide array of useful structures that are of considerable value in the synthesis of natural products. A manuscript describing our preliminary data on this project has been published in Nature Chemistry. We extended the chemistry in our recent report on the diastereoselective addition of Grignard reagents to 3-alkoxy-1-N-sulfonyl azopropenes to the use of 3-amido-1-N-sulfonyl azopropenes derived in situ from α-aziridino-N-sulfonyl hydrazones. This transformation provides an novel and highly flexible approach to the synthesis of α-alkylβ-amino ketones and related compounds. To our knowledge, this is the first report of the 3-amido-1-N-sulfonyl azopropene reactive intermediate in any context, which is a species that has the potential to engage with a wide range of nucleophiles leading to various new bond-forming methods. Indeed, a manuscript describing one such transformation is in the final editorial stages and will be submitted for publication shortly.
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JACINTA C. CONRAD, E-1869, University of Houston. STRUCTURE AND DYNAMICS OF ATTRACTIVE NANOPARTICLE GLASSES. (1) Nanoparticle glasses. We are currently mapping the location of the attractive glass transition in a poly(methyl methacrylate) (PMMA) model system as a function of nanoparticle volume fraction and concentration of a non-adsorbing depletant polymer. To characterize interaction potentials, we implemented a "force-matching" approach, applied it to molecular simulation models, and are validating it against the iterative Boltzmann method used to derive coarse-grained potentials. (2) Controlling and characterizing the depletion interaction. We explored the extent to which attractive solidification can be tuned via particle or polymer disparity in PMMA depletion systems. In Phys. Rev. E (2016), we reported that the evolution of structure, dynamics, and phase behavior of bidisperse particle mixtures was asymmetric in particle size and concentration. Conversely, we found that metrics for structure and for dynamics of particles in unary and binary solutions of polymers could be collapsed onto universal diagrams using a modified total polymer volume fraction. (In preparation.) (3) Confined dynamics. We explored the analogy between crowding, confinement, dynamic arrest, and verification in complex fluids. In Soft Matter (2015), we showed the slowing of diffusive nanoparticle dynamics and the broadening of the distribution of relaxation times with increasingly strong confinement were consistent with the onset of dynamical heterogeneity expected in the approach to verification. We characterized the quiescent diffusion of nanoparticles in geometrically disordered porous media with and without polymer depletants (acting as crowders). We identified distinct dynamical signatures of depletion-mediated (crowding) and hydrodynamically-mediated (confined) arrest and showed that the dynamics recovered to free diffusion when arrested particles were removed. (In preparation.) The long-time driven transport of nanoparticles through disordered porous media, however, was unaffected by the presence of polymer depletants (Soft Matter, 2016). NICHOLAS K. CONRAD, I-1732, The University of Texas Southwestern Medical Center. BIOCHEMICAL ANALYSIS OF A NUCLEAR POLY(A)-DEPENDENT RNA DECAY PATHWAY. In the nucleus of mammalian cells, RNAs are subject to degradation at nearly every step of gene expression. Despite their impact on gene expression, the mechanisms and regulation of nuclear RNAs decay pathways remain poorly defined. During this funding period we published a paper in PLoS Genetics that defines the cellular targets of a novel pathway for nuclear RNA decay described in our lab. Using molecular and biochemical techniques, the report further solidifies the role of the canonical poly(A) polymerases, PAPα and PAPγ, in this decay pathway, which we dubbed PPD, for PABPN1 and PAPα/γ-mediated RNA decay. Nuclear RNAs are hyperadenylated by the combined action of PABPN1 and PAPα/γ and this activity is further linked to decay by the nuclear exosome. In addition, we have now begun to examine the role of PPD in mRNA decay in the Kaposi's sarcoma-associated herpesvirus. Interestingly, our data show that nuclear viral transcripts are targeted by both PPD and an independent pathway involving the nuclear cap-binding complex (CBC). We are currently defining the role of PPD and CBC in nuclear decay using biochemical and molecular analyses. We hope to submit a paper on this work by the end of the year. LYDIA M. CONTRERAS, F-1756, The University of Texas at Austin. IN VIVO STRUCTURE CHARACTERIZATION OF CATALYTIC RNAs BY FLUORESCENCE. (1) Extended use of our fluorescence-based assay to characterize twenty other important RNA regulators: the 6S sRNA important for transcription control, the carbon storage system regulator that is critical for bacterial pathogenesis (CsrB), and eighteen other regulatory RNAs conserved throughout bacteria. Given the structural complexity of these RNAs, we have determined differential accessibility for local regions to indicate highly active regions. (2) Demonstration that genomic libraries of factors that affect RNA folding can be screened using fluorescence oligonucleotide hybridization. We have constructed and screened a genome-wide transposon library in the context of our model group I intron and have shown the utility of our fluorescence-based structural profiling approach to identify genes that affect in vivo transcription and other in vivo RNA processing steps (folding, degradation etc). Ten new factors have been identified; we are in the process of further characterizing their effect on in vivo RNA chemistry. (3) Demonstration of the ability to capture structural changes that result from posttranscriptional modifications and to assay these in the context of native levels of RNA expression. We have now successfully adapted our system to study RNAs at the native level (without need for in trans plasmid expression systems). (4) Adapted structural profiling for high-throughput use by exploiting control of transcriptional elongation as a measure of structural accessibility. We have now shown this capability (coupled with RNA-seq) in the context of a single experiment that tested ~700 different RNA regions, in ~60 targeted regulatory/catalytic RNAs of interest. (5) Contributed fundamental understanding to principles of the role of structural accessibility in RNA targeting. We derived a biophysical model for this work (re-submitted for publication after first revision to NAR). DAVID R. COREY, I-1244, The University of Texas Southwestern Medical Center. RECOGNITION OF DNA BY SYNTHETIC OLIGOMERS. Friedreich's Ataxia (FRDA) is an incurable genetic disorder caused by a mutant expansion of the trinucleotide GAA within an intronic FXN RNA. This expansion leads to reduced expression of frataxin (FXN) protein and evidence suggests that transcriptional repression is caused by an R-loop that forms between the expanded repeat RNA and complementary genomic DNA. Synthetic agents that increase levels of FXN protein might alleviate the disease. During 2015-2016 we demonstrated that introducing anti-GAA duplex RNAs or single-stranded locked nucleic acids (LNAs) into patient-derived cells increases FXN protein expression to levels similar to analogous wild-type cells. 2) MicroRNAs (miRNAs) are small non-coding transcripts that regulate gene expression. Synthetic miRNA mimics can modulate gene expression and offer an approach to therapy. Inside cells, mature miRNAs are produced as double-stranded RNAs and miRNA mimics typically retain both strands. This need for two strands has the potential to complicate drug development. Recently, synthetic chemically modified single-stranded silencing RNAs (ss-siRNA) have been shown to function through the RNAi pathway. We demonstrated that ss-miRNAs can act as miRNA mimics to silence the expression of target
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genes. Chemically modified ss-miRNAs function effectively inside cells through endogenous RNAi pathways and broaden the options for miRNA-based oligonucleotide drug development. 3)A GGGGCC expansion within an intronic region of the C9orf72 gene forms RNA foci that are associated with one third of familial amyotrophic lateral sclerosis (ALS) and one quarter of front temporal dementia (FTD). Synthetic agents that bind these hexanucleotide repeats and block foci would be leads for therapeutic discovery. We have engineered duplex RNAs to enable them to recognize difficult C/G targets. Recognition inhibits foci formed by both GGGGCC and CCCCGG RNA. ANTHONY COZZOLINO, D-1838, Texas Tech University. PHOTOISOMERIZABLE LIGANDS FOR LIGHT HARVESTING BY TRANSITION METAL COMPLEXES. We have completed a full photophysical and computational study of two photoswitchable ligands and have found significant electronic communication between ligating groups and the photoswitch, as anticipated. A manuscript on this is in preparation. We have used these results to assist in the design of photoswitchable ligands with superior properties and two new photoswitchable ligands have been prepared. Metallation studies are under way. Two new research directions are also being explored. The first new direction is sustainable catalysis focusing on transfer hydrogenation reactions in MOFs. We determined that the incorporation of aluminum into Zr-terephthalate frameworks makes a viable catalyst that is significantly more stable to wet conditions than a molecular analogue, can be used at higher temperatures and is reusable. A manuscript is in preparation based upon this work. The molecular recognition and self-assembly of Sb(III) compounds is the second new direction. To this end, an anion receptor has been designed de novo using a computational-assisted approach and a subsequent experimental study has validated this approach. A manuscript has been submitted and another is in preparation regarding these studies. We have also designed tripodal Sb(III) compounds to self-assemble into unique architectures through secondary bonding interactions. We have found that we can control the supramolecular structure through straight-forward manipulation of appended groups. We have isolated a 3D network and a 2D bilayer. The ability to rationally use sterics to control the self-assembly process in a predictable way is the subject of another manuscript in preparation. LUIS G. CUELLO, BI-1757, Texas Tech University Health Science Center. CRYSTALLOGRAPHIC AND FUNCTIONAL STUDIES IN KcsA-Kv CHANNEL CHIMERAS THAT DIFFER IN C-TYPE INACTIVATION PROPERTIES. During this grant year (2015-2016), we were able to move forward in several fronts in our attempt to elucidate the structure-function correlations of the selectivity filter of K+ channels. As a continuation of our research from last year, we have crystallized two key KcsA mutants that made KcsA pore helix and extracellular vestibule more similar to the Shaker channel (the archetypal pore domain of voltage gated K+ channels). We have crystallized the closed state for the KcsA mutants W67F and E71V, both positions are extremely important in regulating the C-type inactivation process in the pore domain of potassium channels. Currently, we are pursuing actively the structure of the double mutant, since in the archetypal Shaker channel seem to produce a constitutively C-type inactivated channel. W434F in the Shaker channel (equivalent to the W67F in the KcsA channel) not only is "frozen" in the C-type inactivated conformation but also is permeable to sodium ions. As a starting point, we have crystallized the W67F mutant, which it has been shown before to be recalcitrant to crytallize. To achieve this goal, we have revisited and improved the expression and purification of KcsA using new E. coli strains, new growth medias, less expensive detergent for protein solubilization and the addition of high-salt for the extraction and stabilization of KcsA. Additionally, we have also crystallize the E71V mutant of KcsA in its closed and open states. On the neuronal Kv channels, a Valine resides at the position equivalent for E71 in KcsA, which it has been shown is a crucial paper of C-type inactivation. We aim to dissect the contribution of these amino acid residues individually from a structural point of view on C-type inactivation. In regard to a chimera channel that combine the mutations E71V, Y82T, L81M and F103l, which make it almost identical to the pore region of the Shaker potassium channel, we have also crystallized it in the presence of 147 mM NaCl and 3 mM KCl. This is important since it is known that neuronal Kv channels undergo C-type inactivation and this crystal structures can give us structural insights about the conformational changes at the pore region of these channels underlying C-type inactivation. For the next and last funding year, we are planning to evaluate the function of these chimera channels and crystallize them in sodium and other permeant ions i.e. Rubidium, Cesium and Thallium. Additionally, we are pursuing actively the crystallization of these chimera channels with mutations known to affect C-type inactivation in Kv channels, the well-known mutations at position T449 within the Shaker channels structure are known to modulate C-type inactivation so we are exploring the structural determinants of this functional phenotype using our KcsA-Shaker channels chimera as a scaffold structure. PENGCHENG DAI, C-1839, Rice University. SPIN DYNAMICS IN SINGLE MOLECULAR MAGNETS. During the current grant year, our group published eleven papers describing our progress in studying spin dynamics in iron and copper based high-temperature superconductors. This include the discovery of spin nematic phase in Ni-doped BaFe2As2 iron pnictides published in PRL, and a comprehensive review article published in Reviews of Modern Physics. In the following, we list the entire published paper with Welch support acknowledged. We also published a book chapter where works in both copper and iron based superconductors are reviewed.
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KEVIN N. DALBY, F-1390, The University of Texas at Austin. TARGETING MELK FOR CANCER THERAPY. Despite recent advances in molecularly directed therapy, triple negative breast cancer (TNBC) remains one of the most aggressive forms of breast cancer still without a suitable target for specific inhibitors. Maternal embryonic leucine zipper kinase (MELK) is highly expressed in TNBC, where level of overexpression correlates with poor prognosis and an aggressive disease course. Through targeted kinase inhibitor library screening, and structure-guided design of a series of ATP-competitive indolinone derivatives, we identified potent inhibitors of MELK. Our lead inhibitor inhibits the phosphorylation of SMAD2/3 in TNBC cells and inhibits TNBC cell growth both in vitro and in vivo. To embark on a chemical genetics approach to identify MELK substrates we have shown that MELK L86G is active, able to utilize ATP-γS, and is best inhibited by specific ATP analogs with large substituents at the C3 position. We are now prepared to conduct substrate labeling experiments in cells to identify MELK substrates. GAUDENZ DANUSER, I-1840, The University of Texas Southwestern Medical Center. PROBING ONCOGENIC FUNCTIONS OF VIMENTIN FILAMENTS BY SMALL MOLECULE SCREENS. As reported last year we have developed an image-based, multi-parametric screen to assess the effects of small molecules on Vimentin integrity and architecture. A confounding factor in cell treatment with cytoskeleton-targeting drugs is the cross-talk and rapid adaptation between cytoskeleton sub-systems. We hope to find a compound that affects only Vimentin for at least fifteen minutes after drug administration. For ~9 months of the past funding period, Dr. Zhengweng Zhang worked with Dr. Posner's team in the HTS facility to further optimize the actual drug incubation protocols. To give but one example of trouble-shooting, we noticed that the available liquid handling robots have an intolerable level of irreproducibility in administering small amounts of compounds for short incubation times. We redesigned the entire screen to achieve robust results, for now at the two hour incubation time scale, including the implementation of a novel data post-processing approach that integrates information from seven image derived parameters in a robust ranking of compound effects, despite significant variation in individual parameters. In April/May we then conducted a full screen on a 2K natural compound library. We identified five potent compounds, one of which (F10) is exclusively affecting Vimentin. We are currently optimizing concentration and conditions for reduced incubation time. Moreover, we have started to run a screen on an 8K synthetic compound library and to apply chemoinformatics to identify additional, structurally comparable compounds in UTSW's 200K library. We anticipate concluding the screening phase by December and initiate target identification assays early in 2017. In case we are invited to submit for renewal, we will focus our application on these procedures and physiological tests. DONALD J. DARENSBOURG, A-0923, Texas A&M University. DESIGN AND REACTIVITY STUDIES OF METAL CATALYSTS FOR THE PRODUCTION OF POLYCARBONATES FROM NOVEL OXIRANES AND CARBON DIOXIDE. Some of our most recent efforts have been directed at synthesizing amphiphilic polycarbonates via epoxide/CO2 coupling. These materials can self-assemble in water to provide functional nanostructures which provide a platform for biomedical applications, e.g., drug delivery. Described below is our most recent successful venture into this area of chemistry involving the synthesis of a biocompatible polymer as a platinum drug delivery carrier. (S)-3,4-dihydroxybutyric acid, an endogenous straight chain fatty acid, is a normal human urinary metabolite and can be obtained as a valuable chiral biomass for synthesizing statin-class drugs. Hence, its epoxide derivatives should serve as promising monomers for producing biocompatible polymers via alternating copolymerization with carbon dioxide. In this report, we demonstrated the production of poly(tert-butyl 3,4-dihydroxybutanoate carbonate) from racemic-tert-butyl 3,4-epoxybutanoate and CO2 using bifunctional cobalt(III) salen catalysts. The copolymer exhibited greater than 99% carbonate linkages, 100% head-to-tail regioselectivity, and a glass-transition temperature (Tg) of 37°C. By way of comparison, the similarly derived polycarbonate from the sterically less congested monomer, methyl 3,4-epoxybutanoate, displayed 91.8% head-to-tail content and a lower Tg of 18°C. The tert-butyl protecting group of the pendant carboxylate group was removed using trifluoroacetic acid to afford poly(3,4-dihydroxybutyric acid carbonate). Depolymerization of poly(tert-butyl 3,4-dihydroxybutanoate carbonate) in the presence of strong base results in a stepwise unzipping of the polymer chain to yield the corresponding cyclic carbonate. Furthermore, the full degradation of the acetyl-capped poly(potassium 3,4-dihydroxybutyrate carbonate) resulted in formation of the biomasses, β-hydroxy-γ-butyrolacetone and 3,4-dihydroxybutyrate, in water (pH = 8) at 37°C. In addition, water-soluble platinum-polymer conjugates were synthesized with platinum loading of 21.3–29.5%, suggesting poly(3,4-dihydroxybutyric acid carbonate) and related derivatives may serve as platinum drug delivery carriers. MARCETTA Y. DARENSBOURG, A-0924, Texas A&M University. SYNTHETIC ANALOGUES AND REACTIVITY STUDIES OF IRON, NICKEL, AND ZINC BIOMIMETIC COMPLEXES CONTAINING HISTIDINE, CYSTEINE, AND NITRIC OXIDE AS LIGANDS. The Cys-X-Cys tripeptide motif provides a contiguous N2S2 binding site for metals in proteins and can be the focus of further metal aggregation. Studies of metal exchange into such tight binding sites found the effect of S-acetylation followed a ligand unwrapping/rewrapping pathway, effectively demonstrating that S-"protection" by acetylation cleanly leads to exchange(M246). Intrigued by the synthesis of "biohybrids" of the [FeFe]-H2ase, we have explored biomimetics of the 3-iron arrangement that suggested linkage isomerism of cyanide as it connects the preformed 2-Fe subsite into 4Fe4S clusters (M248). We prepared and characterized four CN-bridged analogues of such 3-Fe systems, finding that the orientation of the cyanide bridge is solely determined by the precursor reagents; no CN flipping was observed, due to a high barrier (DFT-calculated) for such linkage isomerization. These results highlight further roles for cyanide as an unusual ligand in biology; it stabilizes low spin, low valent iron, and also acts as a docking agent via linear ON bridges. Our understanding of the NO diatomic ligand (M244) and the possibilities of MN2S2 dithiotates as ligands (M243, 249) has led to development of a
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unique set of heterobimetallics as proton reduction electrocatalysts. A series of homo- and heterobimetallics derived from aggregation of ( η5-C5H5)Fe(CO)+ or (η5-C5H5)Fe(CO)2
+ with dithiolato complexes N2S2M, (N2S2 = bismercaptoethane diazacycloheptane; M = Ni or Fe(NO)) serve as paradigms for electrocatalysis suitable for computation-assisted, structure-function analysis. The analysis affirms an electron storage ability of the Fe(NO) unit; the hemi-lability of the bridging thiolate by reductive Fe-S bond cleavage, creates a Lewis pair as proton and hydride buffers (M250). BRYAN W. DAVIES, F-1870, The University of Texas at Austin. HIGH THROUGHPUT SCREENING FOR DISCOVERY AND DEVELOPMENT OF ANTIMICROBIAL PEPTIDES. We have made considerable progress for each objective of the proposed research. We have continued to characterize and develop our screening procedure. This has increased our screening abilities to include screening of cyclic peptides and screening inside an animal host at the site of infection. Cyclic peptides are recognized as promising drugs because of their stability and bioavailability. Our ability to screen peptides in vivo allows us for the first time to determine how factors inside the body influence the activity of antimicrobial compounds. We have completed the largest unbiased screen of 800,000 unique peptides in two bacteria with different surface charge chemistry. While only part of the complete screen we are conducting, our early results have substantiated our hypothesis that there are large areas of unexplored peptide chemical space with antimicrobial activity. The surface charge of a bacterium does appear to alter the profile of antimicrobial peptides returned from our screens, but we have identified many antimicrobial sequences that do not appear to rely on surface charge interactions for their activity. This is in stark contrast to all currently known antimicrobial peptides. We have synthesized several of these new sequences and validated their activity. We are continuing our exploration of antimicrobial peptide space against a set of bacteria with diverse surface chemistry. Our work is supporting our patent application by UT Austin and has generated significant industry interest. We are writing our first manuscript describing our method and results. JEF K. DE BRABANDER, I-1422, The University of Texas Southwestern Medical Center. NOVEL HETEROCYCLIZATIONS FOR NATURAL PRODUCT SYNTHESIS. During the past grant year, we made significant progress resulting in seven published and two submitted manuscripts. In the area of natural product synthesis, we accomplished the total synthesis of the novel marine natural products rifsaliniketal and the structurally related variants salinisporamycin and saliniketal, diverted marine metabolites from the rifamycin biosynthetic pathway with potential antitumor and chemopreventive activity. Our synthetic strategy hinged upon our Pt(II)-catalyzed cycloisomerization methodology, and a fragmentation of an intermediate dihydropyranone to forge a stereochemically defined E,Z-dienamide unit. Multiple routes were explored to assemble fragments with high stereocontrol, an exercise that provided additional insights into acyclic stereocontrol during stereochemically complex fragment-assembly processes. We also continued with Structure-Activity studies of the marine natural product derived V-ATPase inhibitor Saliphenylhalamide and simplified analogs with antiviral activity and promising activity against human lung cancer cell lines with a KRASmut/LKB1mut oncogenotype. In the area of discovery biology (collaboration with the Brown/Goldstein lab at UTSW) we developed probe reagents of U18666A, a derivative of androstenolone, which was shown to inhibit the exit of cholesterol from lysosomes and thus represents a powerful tool for the study of lysosomal cholesterol transport. A photoreactive derivative led to the specific cross-linking and pull-down of a specific binding protein characterized as NPC-1 (Niemann-Pick disease, type C1). Interestingly, the U-compound binds to the sterol-sensing domain and not
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the N-terminal domain that accepts the cholesterol from NPC-2 during the hydrophobic handoff. RALPH J. DEBERARDINIS, I-1733, The University of Texas Southwestern Medical Center. GLUTAMINE-DEPENDENT REDUCTIVE CARBOXYLATION: A METABOLIC ACHILLES' HEEL IN CANCER. Aim 1: We completed our study of a GDRC-dependent pathway that supports anchorage-independent growth of cancer cells (Jiang et al. Nature, 2016). In this pathway, loss of attachment to an extracellular matrix induces a burst of mitochondrial reactive oxygen species (ROS) caused by abrupt changes in rates of oxidative metabolism. This ROS burst is counteracted by delivery of NADPH using a pathway involving GDRC. The pathway is initiated by isocitrate dehydrogenase-1 (IDH1)-mediated reductive carboxylation to produce isocitrate/citrate in the cytosol. This reaction consumes NADPH produced by the pentose phosphate pathway, transferring the reducing equivalents to isocitrate/citrate. These metabolites are then transferred into the mitochondria and oxidized, releasing NADPH to mitigate ROS damage. Genetic silencing of several molecular components of this pathway reduced cancer cell growth during matrix-detached conditions without affecting growth of matrix-attached cells. Preliminary observations made after publication of the article suggest that inhibiting this pathway suppresses metastasis in mice. Aim 2: We identified two IDH1 inhibitors from Glaxo-SmithKline that inhibit wild-type IDH1 and eliminate GDRC in matrix-detached cells. We are currently testing whether these compounds are potent enough to use in mouse models of metastasis. We also used an integrative approach in genomics/metabolomics to identify additional metabolic vulnerabilities in cancer cells. One such vulnerability related to glutamine metabolism was observed in lung cancer cells containing concurrent mutations in KRAS and STK11, which together specify oncologically aggressive disease. In these cells, nitrogen from the amide position of glutamine is transferred via the mitochondrial enzyme carbamoylphosphate synthetase-1 into the pathway of de novo pyrimidine biosynthesis. Inhibiting this unconventional pathway of pyrimidine metabolism leads to a severe imbalance of nucleotide pools, DNA damage and cell death. A manuscript describing this pathway was submitted in June, 2016 (Kim et al). GEORGE N. DEMARTINO, I-1500, The University of Texas Southwestern Medical Center. REGULATION OF PROTEASOME FUNCTION BY REVERSIBLE SUMOYLATION. In the previous progress report we described the successful in vitro modification of 26S proteasome by SUMOylation and characterization of the corresponding inhibitory effects of this modification on proteasome activity. During the past year, we have demonstrated that SENP1 deSUMOylates the proteasome by removing SUMO from the Rpt2 subunit of the PA700 regulatory complex. This action restores proteasome activity to normal levels, as measured by the hydrolysis of short model peptides and by the hydrolysis of a model polyubiquitylated protein, (Ub)n-Sic. SENP1 also restores the SUMO-inhibited ATPase activity of 26S to normal levels. These findings are consistent with and support our hypothesis that SUMOylation negatively regulates proteasome function and that SENP1 reverses this effect. During the past year we have also characterized the action of 26S proteasome on mixed SUMOylated/polyubiqutiylated protein substrates, as required for analysis of the effects of SENP1 on these substrates. Although the in vitro production of these substrates in amounts and purity required for biochemical analysis has been technically challenging we have successfully produced these substrate forms. First, we have engineered a SUMO consensus site into the C-terminus of Sic and have used SUMO E1, Ubc9, and SUMO to achieve in vitro modification of Sic. As expected, this substrate is not degraded by 26S. We have subjected this protein to in vitro ubiquityation reactions to create mixed SUMO/ubiquitin-modified Sic for use in proteasome degradation assays. We have shown that these substrates are degraded in vitro by purified 26S proteasome and are testing the main hypothesis of the proposal and the role of SENP1 in this process. As reported last year, we made the unexpected discovery that P131 (PSMF-l) blocks proteasome SUMOylation. We have used CRISPR/Cas9 to create a HAP1 cell line that lacks PI31. We will use these cells to test the physiologic significance of this effect and as a possible alternative method of manipulating proteasomal SUMOylation. These studies will provide additional insight for the role of SUMOylation on proteasome function and on the currently uncertain physiologic functions of PI31. H. V. RASIKA DIAS, Y-1289, The University of Texas at Arlington. METAL COMPLEXES OF FLUORINATED LIGANDS. Metal adducts of poly-fluorinated ligands and anions show unusually high thermal and air stability and very interesting chemical reactivity not usually seen with the related non-fluorinated analogs. During this project period, we reported the isolation of cationic zinc(II) complexes supported by fluorinated tris(pyrazolyborates and their utility in hydrocarbon C-H bond activation process via carbene insertion. We have also stabilized a closely related series of copper, silver and gold ethylene complexes and investigated metal-ligand bonding and group 11 family trends. The gold forms the strongest metal-ethylene bond in this series. Fluorinated triazapentadienyl ligands afforded zinc(II) alkyl compounds with very Lewis acidic metal sites. They react with oxygen and afforded isolable zinc(II) peroxides and alkoxides. The zinc alkyl complexes catalyze the dimerization of aldehydes very effectively. Finally, we also uncovered an interesting gold mediated skeletal rearrangement of cyclooctyne to produce ring-fused, alkenes. We have also isolated and structurally characterized all the gold bound precursor alkyne and product alkene molecules. Such gold-alkyne and gold-alkene complexes are rare.
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GUANGBIN DONG, F-1781, The University of Texas at Austin. SITE-SELECTIVE C–H BOND FUNCTIONALIZATION. (A) Developed a novel method for C-H arylation of cyclopentanones. Direct arylation of cyclopentanones has been a long-standing challenge because of competitive self-aldol condensation and multiple arylations. We developed a direct mono-α-C–H arylation of cyclopentanones with aryl bromides which is enabled by palladium/amine cooperative catalysis. This method is scalable and chemoselective with broad functional-group tolerance. Application to controlled sequential arylation of cyclopentanones has been also demonstrated. (B) Developed a new hydrazone-based exo-directing g roup (DG) strategy for the functionalization of unactivated primary β C–H bonds of aliphatic amines. Conveniently synthesized from protected primary amines, the hydrazone DGs are shown to site-selectively promote the β-acetoxylation and tosyloxylation via five-membered exo-palladacycles. Amines with a wide scope of skeletons and functional groups are tolerated. Moreover, the hydrazone DG can be readily removed, and a one-pot C–H acetoxylation/DG removal protocol was also discovered. IVÁN D'ORSO, I-1782, The University of Texas Southwestern Medical Center. COOPERATIVE ASSEMBLY OF HIV TRANSCRIPTION ELONGATION COMPLEXES. The transcriptional program of HIV is controlled at the elongation step by an RNA polymerase II (Pol II) complex that pauses at the viral promoter shortly after transcription initiation. Pol II pause release and productive elongation is mediated by the positive elongation factor P-TEFb which phosphorylates Pol II in response to inducible cellular Transcription Factors (TF) and the viral encoded TF Tat. Previous paradigm-shifting discoveries from my lab have led us to propose a model whereby P-TEFb is recruited to the viral promoter early in the transcription cycle as part of the 7SK complex, in which the kinase remains catalytically inactive. Using a combination of genetic and biochemical approaches we now discovered that the transcriptional regulator KAP1/TRIM28 bridge the 7SK complex to the promoter containing paused Pol II to facilitate "on-site" kinase activation and transcriptional pause release. During the current grant year of The Welch Foundation award we have made remarkable progress towards achieving the Specific Aims of this proposal. For Specific Aim 1, we discovered that KAP1 uses its bromodomain to assemble on the first nucleosome downstream the viral promoter by contacting a new histone tail post-translational modification. For Specific Aim 2, we demonstrated that while KAP1 is needed for gene activation by inducible TFs, it is dispensable for Tat activation, thus indicating unique evolutionary strategies by which HIV robustly activates its genome (bypassing a host cell regulatory mechanism). Ongoing studies are in progress to fully determine the mechanisms of assembly using a biochemical-biophysical approach. In the next 2 years of this research grant program we will complete these studies to fully elucidate how assembly of the KAP1-7SK complex on chromatin enables Pol II pause release and transcription activation at the viral promoter.
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MICHAEL DOWNER, F-1038, The University of Texas at Austin. FEMTOSECOND OPTICAL PROBES OF NANO-INTERFACE CHEMISTRY. Our Welch-sponsored research employs a diverse suite of optical methods to probe the chemistry of micro-and nano-interfaces noninvasively. This year we continued two collaborations with colleagues in UT's College of Engineering. In collaboration with Prof. A. Bhasin, we discovered a near-infrared transparency window in pavement-grade bitumen that opens its rich interior bulk microstructure to scientific view over a wide range of temperatures, chemical compositions and stresses for the first time. Variations in microstructure volume fraction with temperature, tracked by dark-field microscopy, were found to correlate closely with variation in shear strength, tracked by dynamic shear rheometry [Ramm, .J. Microscopy 262(3), 216 (2016)]. In collaboration with Prof. P. Ho, we continued an optical study of 3-D strain in Si-Si bonds surrounding copper through-silicon-vias (TSVs), critical components of 3D integrated circuits. We published a general theoretical model of optical second-harmonic generation (SHG) induced by strain fields with up to three spatial coordinates. This model demonstrated, in principle, the capability of SHG to isolate and measure individual components of the 6-component strain tensor, thus significantly complementing Raman spectroscopy [Mendoza, Phys. Stat. Sol. B 253, 218 (2016)]. We demonstrated this capability through a laboratory SHG microscopy study of thermally cycled silicon pervaded by TSVs. The results isolated and quantified axial shear strain components that were invisible to Raman spectroscopy [Cho, Appl. Phys. Lett. 108, 151602 (2016)]. MICHAEL P. DOYLE, AX-1871, The University of Texas at San Antonio. SELECTIVE CHEMICAL OXIDATIONS. Research during this grant year has developed an efficient two-step protocol for the catalytic asymmetric synthesis of 1H-pyrrol-3(2H)-one derivatives in 99% ee from conveniently accessed 2,3-diketoesters (published in Chemical Communications). These structures are widely represented in natural products. Their synthesis occurs in two steps from readily available 2,3-diketoester hydrates that are formed by oxidation of diazoketoesters and are sufficiently reactive so that their anhydrous form is not required. The essential first step is asymmetric aldol condensation with the 2,3-diketoester hydrates that occurs at room temperature using L-proline as the organocatalyst. The methodology for the oxidation of diazoketoesters is currently under investigation to replace the aqueous conditions previously used that form 2,3-diketoester hydrates that have limited reactivity, and catalytic conditions using oxygen atom transfer from dimethylsulfoxide is optimal. With the aid of this grant we have also completed the research that reports a truly unusual rearrangement reaction of an allene-1-yl phenyldiazoacetate that involves a major structural reorganization (submitted for publication). The allene initiates a complex transformation in which the terminal nitrogen of the diazo functional group undergoes intramolecular electrophilic addition onto the central carbon of the allene to initiate a sequence of bond forming reactions resulting in the production of 1,5-dihydro-4H-pyrazol-4-ones in good yields. The original ester is converted to a diketone (an unexpected and unique redox reaction) through a process that does not involve a catalyst. 1,5-Dihydro-4H-pyrazol-4-ones that are previously inaccessible acyl transfer agents are the products, and their synthesis shows generality. They are currently being investigated for highly selective acyl transfer reagents for di- and poly-amines and –alcohols. Investigations have begun on C=C bond cleavage reactions of organic compounds, extended beyond the simple cleavage reactions of 1,1-diphenylethylene and alpha-methylstyrene. The oxidation of cinnamyl alcohol to benzaldehyde has been instructive, producing cinnamaldehyde on the pathway to cleavage and indicating that Michael addition may precede carbon-carbon bond cleavage. In the course of these investigations we have also uncovered a most unusual oxidative vinyl group cleavage of N-allylanilines that is reproducible through the use of multiple oxidants and trapping agents, but we do not yet know the fate of the vinyl group. These systems are currently receiving intense scrutiny. The use of amines capable of forming nitrogen radical cationic intermediates is another outlet for our investigations of selective chemical oxidations. One example of this selectivity is the conversion of a N,N-dimethyl hydrazones to the corresponding N-methylformamides using dirhodium(lI) carboxamidate catalyzed oxidations by tert-butyl hydroperoxide. RUI-RUI DU, C-1682, Rice University. MICROWAVE AND INFRARED SPECTROSCOPY OF 2D ATOMIC CRYSTALS AND TOPOLOGICAL INSULATORS. 1. Determining the effective spin g-factors of electrons in the InAs layer and that of holes in the GaSb layer in the InAs/GaSb 20 topological insulators. By means of coincidence method utilizing a tilted magnetic field, Landau level (LL) spectra of electron and hole carriers are systematically studied at different carrier densities tuned by gate voltages. When Fermi level stays in the conduction band, LL crossing and anti-crossing behaviors were observed at odd and even filling factors, respectively, with a corresponding g-factor of 11.5. It remains nearly constant for varying filling factors and electron densities. On the contrary, for GaSb holes, only a small Zeeman splitting is observed even at large tilt angles, indicating a g-factor of less than 3. These results are significant in understanding the spin degree of freedom and spin-orbital interactions in this important 20 topological insulator, and have been published. 2. We construct an apparatus for measuring cyclotron resonance in 20 electron gases using a refection configuration. In contrast to traditional transmission spectroscopy, this method does not require sample preparation and allows for application of gate to tune the Fermi energy. This instrumentation will be applied to measure cyclotron and spin resonances in 20 atomic crystals and topological insulators.
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KIM R. DUNBAR, A-1449, Texas A&M University. MAGNETIC AND ELECTRONIC PROPERTIES OF MOLECULAR MATERIALS: INVESTIGATION OF FACTORS THAT EFFECT BISTABILITY. In the current funding period, we continue to work on the highly promising anion [Mo(CN)7]4-. Incorporating this anion into new compounds is challenging due to the air sensitive nature of the anion, as well as lability of one cyanide ligand under some conditions. In the past, we have highlighted both of these traits by publishing pentanuclear, trigonal bipyramidal molecules (TBPs) and linear, trinuclear molecules. One of- the TBPs, with the formula [V(tmphen)2]3(Mo(CN)6]2 (tmphen = 3,4,7,8-tetramethyt-1,10-phenanthroline), holds the record for the largest coupling constant in a cyanide bridged compound. The trinuclear molecule, which contains one MoII center and two MnII centers, holds the record for the highest blocking temperature in a cyanide bridged compound, and the MoIII coordination sphere still contains all seven CN- ligands. We have also successfully demonstrated a facile synthetic method for bifunctional magnetically bistable and electrical conducting materials and that the bifunctional salt (Co(terpy)2](TCNQ)3⋅CH3CN (terpy = 2,2';6',2"-terpyridine, TCNQ = 7,7,8,8-tetracyanoquino-dimethane) exhibits a high room temperature conductivity of 0.13 S cm-1 and an anomaly in conductivity at 190 K. As a continuation, we have employed Coll-based SCO complexes with an expanded aromatic system and found that the incorporation of TCNQ radicals as counterions for the spin-crossover material [Co(pyterpy)2](TCNQ)2-solvent (pyterpy = 4'-(4"'-pyridyl)-2,2':6',2"-terpyridine) leads to structural distortions of the [Co(pyterpy)2]2+ spin-crossover cation as compared to [Co(pyterpy)2](PF6)2. Strong intermolecular interactions between the SCO centers have been realized by taking advantage of the supramolecutar π-stacking interactions between the terminal pyridyl groups of the pyterpy ligands and TCNQ radicals. In comparison to the high symmetry of the parent compound, in which the HS to LS transition is incomplete even at 5 K, the radical-pyridyl π-stacking interaction in the pyterpy compound distorts the Cell coordination geometry and helps to stabilize the LS 2E state. The design of multifunctional SCO materials with improved cooperativity will greatly benefit from this new strategy of employing organic radicals to enhance intermolecular interactions. F. BARRY DUNNING, C-0734, Rice University. STUDIES INVOLVING MOLECULES IN HIGH RYDBERG STATES. Cold strontium gases held in a dipole trap have been used to study the formation and properties of ultra long-range Rydberg molecules in which scattering of the excited electron in the Rydberg atom from neighboring ground state atom(s) produces a novel chemical bond that binds them together. Initial studies focused on the vibrational structure of such molecules and on their lifetimes. Measurements were then extended to very high density thermal gas samples and Bose-Einstein condensates to explore formation of Rydberg molecules that comprise several bound ground state atoms. This work has revealed an interesting "shell-like" structure in which the different bound ground state atoms each occupy one of several specific vibrational levels. This work is also providing new insights into the behavior of such systems when immersed in a quantum-degenerate "fluid." In a separate series of experiments electron transfer in collisions between potassium atoms in high Rydberg states and targets that attach low-energy electrons are being exploited to create molecules comprising a positive-negative ion pair that orbit at large separation weakly bound by their weak Coulomb attraction. Such states are also termed heavy-Rydberg ion-pair states because many of their properties mirror those of Rydberg atoms. The dynamics involved in the formation of such species have been explored through measurements of the velocity and angular distributions of the product ion-pair states. These studies have provided new insights into the lifetimes and decay modes of long-range ion-pair molecules and a new tool to explore the dynamics of dissociative electron capture reactions. ANDREW D. ELLINGTON, F-1654, The University of Texas at Austin. KINETIC AND STRUCTURAL CHARACTERIZATION OF THE FIRST ERROR-CORRECTING REVERSE TRANSCRIPTASE. In finishing the previous Welch grant, we largely achieved our aims. Using our directed evolution platform known as compartmentalized partnered replication (CPR), we selected T7 RNA polymerase variants (T7 RNAP) that could orthogonally recognize different promoters This work was published in ACS Synthetic Biology We were then able to introduce mutations into the polymerase to increase both its thermostability and its substrate range. allowing the incorporation of highly modified nucleotides. This work was published in Nucleic Acids Research. Since then we have carried out additional selections to improve the processivity of T7 RNAP, and have begun collaborations with Dr. James Eberwine at the University of Pennsylvania on adapting these processivity variants to improve RNA-based amplification methods, especially for the analysis of single cell transcriptomes. Initial results with enzymes transferred to the Eberwine lab appear to give greater transcriptome coverage, and as was the case with previous RNA polymerase variants, we anticipate both patenting and publishing this work. It should be noted that the suite of RNA polymerase variants that we have developed with Welch Foundation funding continue to be of commercial interest for the biosynthesis of therapauetics (i.e., modified antisense, siRNAs, aptamers, and potentially longer mRNA vaccines). As previously noted, we have expanded our directed evolution program from RNA polymerases to DNA polymerases, in particular evolving the thermostable, strand-displacing Bst polymerase to operate more robustly in isothermal amplification assays such as rolling circle amplification (RCA). We now have several candidate enzymes that we are focusing on, and anticipate that these new Bst variants will greatly assist in our ongoing attempts to adapt loop-mediated isothermal amplification (LAMP) to point-of-care challenges, in that we will be able to directly lyse cells in biological samples by boiling (something the current generation of commercial Bst polymerases are incapable of). Finally, and as previously noted, we have used directed evolution to adapt the KOD DNA polymerase to functioning as a thermostable, error-correcting reverse transcriptase. This work was recently published in Science, and is now the focus of the new, continuing Welch Foundation research grant. As anticipated, there is great interest in this result, and we have provided enzyme samples to numerous labs and companies.
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CHRISTOPHER J. ELLISON, F-1709, The University of Texas at Austin. PHOTOCHEMICAL APPROACH FOR PROGRAMMING AND DIRECTING SURFACE ENERGY DRIVEN MARANGONI CONVECTION TO GENERATE TOPOGRAPHIC PATTERNS IN POLYMER THIN FILMS. The Marangoni effect causes liquids to flow toward localized regions of higher surface tension. In thin polymer films, this effect may be harnessed for manufacturing topographically patterned surfaces. Our previous theoretical model revealed that maximum feature heights are favored by large surface tension gradients, low diffusivities, and low viscosities; low viscosities also promote rapid feature formation. However, low viscosity generally results in high diffusivity which dissipates the prescribed surface tension patterns. To address this issue, we have developed a strategy to decouple film diffusivity and viscosity with a large surface tension gradient. This was achieved by blending a low molecular weight polystyrene (PS) with a higher molecular weight photopolymer that is miscible with PS. The selected photopolymer was a random copolymer of tert-butoxy styrene and styrene synthesized by anionic polymerization, while the low molecular weight PS was synthesized by ARGET ATRP. These polymers were co-cast with a photo-acid generator and exposed through a mask, yielding a significantly larger surface tension gradient between light exposed and unexposed regions compared with our previous all PS work. As the figure shows, this strategy enabled the formation of 500 nm high features (double the initial film thickness) within only 30 mins of thermal annealing. Furthermore, the formed features were stable upon extensive thermal annealing up to one month. DONGLEI L. FAN, F-1734, The University of Texas at Austin. INVESTIGATION OF A GENERAL MECHANISM FOR RATIONAL SYNTHESIS OF THREE-DIMENSIONAL SEMICONDUCTOR NANOSUPERSTRUCTURES BY DESIGNED CHEMICAL CATALYSTS. Three dimensional nanosuperstructures have received consideration research interest due to its critical roles in the development of the next-generation energy devices with high capacity, efficiency, and safety. Following last year's success in the systematic investigation of the conditions for obtaining 3-D multilevel porous Ni-Cu nanocatalysts and the fabrication of porous graphite with tunable pore sizes from 1.9 to 8.3 µm, in this project year, we investigated the growth of Mn3O4 nanocrystals, a pseudo-capacitive oxide material, on the multilevel porous graphite with various pore sizes by hydrothermal reaction. The obtained graphite/Mn3O4 superstructures are free-standing and applied as electrodes of supercapacitors without the use of any binders, conductive additives or metal-based current collectors, which dramatically decrease the resistance and mass of the electrode. As a result, a remarkable specific capacitance can be obtained as 782 F/g and 260 F/g at 1 mV/s based the net mass of the active materials Mn3O4 and the total mass of the entire electrode, respectively, which are among the highest reported in literature. It is also found that the higher the mass load of the active Mn3O4 nanocrystals, the higher specific capacitance of the graphite/ Mn3O4 composite supercapacitors. The Mn3O4-graphite supercapacitors also demonstrate excellent electrochemical stability and cycle life with a capacitance-retention of 90% after 10,000 charge-discharge cycles at 10 A/g. In the second part of this project period, we initiated the investigation of an innovative paradigm in growing dendritically porous Ni/Cu alloys on commercially available Ni foams via a one-step electrodeposition process for designed nanosuperstructures. High density dendritic micro/nanobranches can be facilely synthesized to fill the empty voids (250 -100 βm) of the the Ni foams. This process can substantially increase the total area and reduce the feature size of the Ni foams from ~100 µm to less than 1 µm. These results are one of the first discoveries in the Cu/Ni system. WALTER L. FAST, F-1572, The University of Texas at Austin. CHEMICAL PROBES FOR BIOLOGICAL CATALYSTS. For this grant period, we report publications that focus on small molecule interactions with a family of dinuclear zinc hydrolases including metallo-beta-lactamases and quorum-quenching metallo-gamma-lactonases. We have extended our characterization of ligand interactions with this superfamily of proteins using some of our previously described n-alkylboronate probes and this year have identified new two probes for these dinuclear sites through screening of a chelator fragment library - optimization of these ligands is ongoing work. While characterizing the interactions of these ligands and the dizinc center, we discovered that a clinically-occurring mutation in one antibiotic resistance enzyme (NDM4) results in altering zinc affinity and has a zinc concentration-dependent impact on both catalysis and the resulting resistance - work that is currently being prepared for submission. We previously described the design of a circularly permuted variant of the siderophore biosynthetic enzyme PvdQ and this year have succeeded in designing an inactive double mutant that traps the siderophore precursor substrate, and have obtained a X-ray crystal structure of this complex revealing for the first time a binding pocket for the precursor's phenol substituent. This work is currently being prepared for submission. In other work on chemical probes, we deepened our study of 2- and 4-halopyridines as selective covalent protein modifiers and systematically studied the effects of protonation state and electron donating or withdrawing groups on inactivation rates of the enzyme dimethylarginine dimethylaminohydrolase (DDAH) and on the rates of nonenzymic reaction with thiols. We found that
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protonation, in this case catalyzed by the enzyme, can afford up to an approximate 4000-fold rate enhancement that leads to site-selective modification. Development of covalent probes for biological catalysts continues to be a fruitful area of study and will continue in the following grant period. MICHAEL FINDLATER, D-1807, Texas Tech University. BASE-METAL CATALYZED OLEFIN METHATHESIS REACTIONS. The last year has seen significant progress in a number of areas: 1) hydrosilylation catalyzed by iron and cobalt complexes and, 2) catalysis of carbon-carbon bond formation employing simple iron salts. Hydrosilylation is the formal addition of H and Si across a multiple bond, this is a valuable transformation and represents one of the largest scale homogeneous catalytic processes carried out industrially. Platinum complexes are the current state of the art in olefin hydrosilylation yet most of the metal is abandoned in the polymeric products obtained - at a substantial cost. Our initial publications in this field, supported by the Welch Foundation, demonstrated the hydrosilylation of carbonyl-containing molecules catalyzed by both iron and cobalt complexes (A and B). While the emphasis in our work is to understand the fundamental chemistry at play in non-precious metal catalysis, it is exciting to envision the potential economic benefits of moving from platinum to iron. In an unexpected result, we also discovered that the cheap and commercially available FeCl3 is capable of catalyzing the formation of carbon-carbon bonds in a process, which results in the dimerization of cycloolefins. We are actively exploring this chemistry and its potential application in the preparation of biofuels. ILYA J. FINKELSTEIN, F-1808, The University of Texas at Austin. MOLECULAR MECHANISMS OF REPLICATING THROUGH DNA LESIONS. A. We recently developed a method for organizing hundreds of thousands of DNA molecules on the surfaces of passivated microscope flowcells (published in Langmuir, 31: 10310-7 (2016)). We have recently extended this method to include very long single-stranded DNA molecules (~100,000 nt). These will be used as substrates for single-molecule imaging of DNA replication. B. We submitted a manuscript describing a toolkit for efficiently engineering DNA structures within long homoduplex DNA substrates (Sci Rep, 2016, submitted; Methods in Enzymology, 2016, submitted). Using this methodology, we have begun studying PCNA, the eukaryotic DNA polymerase processivity clamp (Sci Rep, 2016, submitted). This lays the foundation for understanding the functions of processivity clamps in DNA replication and repair. C. In parallel, we applied the tools developed in connection with this work to other DNA processing enzymes. We published a manuscript describing how the first steps of eukaryotic DNA mismatch repair occur on a nucleosome-coated DNA (Nature Communications, 7 : 10607 (2016)). We also published a manuscript describing the mechanisms of DNA processing by EXO1, a critical enzyme in restarting stalled replication forks and repairing DNA double strand breaks (PNAS, 113 : E1170-9 (2016)).
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PAUL F. FITZPATRICK, AQ-1245, The University of Texas Health Science Center at San Antonio. MECHANISMS OF OXIDATIVE ENZYMES. Liver phenylalanine hydroxylase (PheH) is allosterically regulated by its substrate phenylalanine. We have used NMR spectroscopy to determine the structure of the dimer formed when phenylalanine binds to the isolated regulatory domain. NOESY experiments utilizing unlabled phenylalanine and 15N-labeled deuterated protein have allowed us to identify the allosteric site for phenylalanine in the regulatory domain for the first time. We have used X-ray crystallography to determine the structures of the resting form of the enzyme and of a mutant in which phenylalanine binding in the active site has been abrogated by mutagenesis. SAXS analyses of the wild-type and mutant proteins were used to validate a model for the activated enzyme in which the regulatory domains from subunits on the opposite side of the dimer-dimer interface interact in the presence of phenylalanine; this has allowed us to identify the structural change that accompanies activation. Bacterial PheHs lack regulatory domains, making them simpler models for probing catalysis. We have now determined the complete kinetic mechanism and the intrinsic rate constants for the reaction of Chromobacterium violaceum PheH with tetrabiopterin and 6-methyltetrahydropterin (Figure) as the pteriri substrate. MATTHEW S. FOSTER, C-1809, Rice University. TOPOLOGICAL MATTER PHASES UNDER EXTREME DURESS: DYNAMICS AND DISORDER. All objectives were successfully accomplished, leading to five publications, including three in PRL. Our work on Coulomb drag between 1D topological edge states demonstrated that one can measure the Luttinger parameter via dc transport, using a novel Coulomb drag geometry in which edge loops rotate as interlocking "quantum gears." This could pave the way for gear-based quantum devices. Our work on Floquet topological superconductors crystallized the distinction between observables that are or are not sensitive to the out-of-equilibrium distribution function, and provided detailed predictions using the integrable dynamics of the underlying BCS model. Our first PRL of 2016 dealt with the interplay of Rashba spin-orbit coupling (RSOC), disorder, and interactions in a single edge state of a 2D topological insulator. While it was known that RSOC and disorder alone should not affect dc transport, there were claims in the literature that the interplay of these with Luttinger interactions could lead to finite temperature conductance corrections, or even Anderson localization of the edge states. We proved that these claims were false by solving exactly the edge model with all three ingredients, revealing a hidden integrability in the problem that takes the form of a spin-1/2 moment evolving in a randomly fluctuating (but special) magnetic field. Finally, our work on thermoelectric transport coefficients in graphene in the hydrodynamic regime gave quantitative agreement with thermopower measurements performed in Philip Kim's group at Harvard. DOUG E. FRANTZ, AX-1735, The University of Texas at San Antonio. DEVELOPMENT OF NON-TRADITIONAL CATALYTIC PATHWAYS OF STEREODEFINED ENOL TRIFLATES. We made significant progress towards developing a new approach into asymmetric allylic alkylations via a mechanistically distinct Pd-catalyzed pathway involving stereodefined enol trifiates during the previous funding period. However, despite our best efforts, we were never able to achieve isolated yields higher than ~50% across a broad range of enol triflates and/or nucleophiles in a timely fashion. While we believe that this reaction still has the potential to be developed into a useful synthetic methodology, we decided to use our last year of funding to pursue more productive methods. We are pleased to report that we were able to discover and develop the first Fe-catalyzed stereoselective cross-coupling reaction between stereodefined enol carbamates and Grignard reagents to yield tri- and tetrasubstituted olefins. The methodology represents one of the only Fe-catalyzed cross-coupling reactions that can access highly substituted acyclic olefins with complete control of stereochemistry. Furthermore. during the course of our work, we developed a new approach to the starting (E)- and (Z)-enol carbmates from a single acetoacetate precursor that we believe will find general use in the synthetic community as well.
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FRANÇOIS P. GABBAÏ, A-1423, Texas A&M University. COORDINATION NON-INNOCENCE OF ANTIMONY AND TELLURIUM LIGANDS. In the second year of this award, we have exploited the coordination non-innocence of antimony ligands in the context of sensing and catalysis. The coordination non-innocence of antimony species is illustrated by the ability of stibonium cations to convert into the corresponding stiboranes by coordination of an anion. Capitalizing on this characteristic, we have shown that stibonium ions such as the 3-perylenyltriphenylstibonium cation can be used for the fluorescence turn-on sensing of fluoride in water at ppm concentrations (Organometallics 2016, 35, 1854). We have extended this concept to the area of Lewis acidcatalysis with the bifunctional stibonium derivative, which can be used to promote the hydrosilylation of benzaldhyde (Chem. Eur. J. 2016, 22, 6537). A comparison with simple monofunctional analogs suggests that the unique catalytic properties of this dication originate from the ability of the two stibonium ions to concomitantly coordinate to the carbonyl substrate. In another illustration of the non-innocence of antimony ligands, we have shown that the antimony center of ((o-(Ph2P)C6H4)2SbCl)AuCl can be oxidized by PhlCl2 affording, after a series of anion exchange reactions, [((o-(Ph2P)C6H4)2SbF3)Au]+. This complex is unusual in that the gold atom is flanked by a highly acidic Ar2SbF3 unit (Ar = aryl), resulting in a strong Au→Sb interaction. As a result, the gold center becomes electron poor, making it a very potent catalytic center for the hydroamination of alkynes (J. Am. Chem, Soc. 2015, 137, 13425). Finally, in an effort to complete a study from a previous cycle, we have investigated the reduction of the α-phosphonio-carbocation and found that it proceeds in two steps to afford the corresponding radical and ylide (Chem. Eur. J. 2016, 22, 2882). Last, we have written two important reviews (Acc. Chem. Res. 2016, 49, 857 and Chem. Lett. 2016, 45, 376) that summarize some of the work directly supported by this grant.
VENKAT GANESAN, F-1599, The University of Texas at Austin. FUNDAMENTAL STUDIES OF SELF-ASSEMBLY IN MIXTURES OF ORGANIC AND INORGANIC MOLECULES. In this period of reporting, our work explored many aspects of ion transport and structure in mixtures organic and inorganic materials. Specifically, our work explored the mechanisms underlying ion transport in polymeric electrolytes containing dispersed inorganic particles. In such a context, we varied the surface chemistry of the particles by studying different polymers of A12O3, and established the polymer-surface and ion-surface interactions play a critical role in modulating the ion transport phenomena. We extended such findings to probe the specific surface chemistries most amenable for enhanced ion transport. In a different line of work, we examined the structure in binary mixtures of electron donors-acceptors containing a third block copolymeric component. In such a context, we demonstrated that such additives can be used to facilitate novel self-assembled morphologies which may possess desirable characteristics for charge transfer. In addition, we demonstrated the concept of "energy cascade" which can arise for appropriate values of the energy levels of molecular orbitals of the different component. Finally, we also considered self-assembled morphologies arising in block copolymer systems and elucidated the mechanisms underlying ion transport in such media. JOHN A. GLADYSZ, A-1656, Texas A&M University. WERNER COMPLEXES AS “ORGANOCATALYSTS”. This year, all of the publications deal with novel metal containing hydrogen bond donors that serve as (enantioselective) catalysts for carbon-carbon bond forming reactions. The last one listed applies a catalyst that was reported in a paper last year, ∆-[Co((S,S)-dpen)3]3+ 2ClˉB(C6F5)4ˉ, in which dpen is 1,2-diphenylethylenediamine. This species (5 mol%) effected additions of 1 ,3-dicarbonyl compounds to di-t-butyl azodicarboxylate in the presence of N-methylmorpholine (1.0:1.0:0.10) in CH3CN at 0 °C, as illustrated with educts derived from five- or six-membered ring ketones (99-88% yields, >99-91% ee) and cycloheptanone (94%, 72% ee), as well as 2-cyanocyclopentanone (92%, 45% ee) and an acyclic system (98%, >99% ee). All of these are easily elaborated to amino acids. The yields/ee values compare well with the best existing catalysts. Hence, this catalyst performs well in numerous types of organic reactions. Ligands H2NCH((CH2)nNMe2)CH2NH2 (n = 1-4; a-d) are efficiently synthesized in enantiopure form from the inexpensive commercial starting materials (L)-asparag in (S)-5-hydroxymethyl-2-pyr-rolidinone, and (S)-6-(((benzyloxy)carbonyl)-amino)-2-((tert-butoxycarbonyl)amino) hexanoic acid in six to nine standard steps (26% average overall yield). These are elaborated to the cobalt complexes [Co(en)2((S)-H2NCH((CH2)nNHMe2)CH2NH2)}4+ 4Cˉ (3a-d⋅H4+ 4Clˉ). The cobalt diastereomers ( ˄/∆) are separated and the anions exchanged to give lipophilic ˄- and ∆-3a-d3+ 3BArfˉ, which are screened as catalysts (10 mol%) for additions of dialkyl malonates to nitroalkenes. ˄-3b-d3+ 3BArfˉ give appreciable enantioselectivities, with optimal conditions involving ˄-3c3+ 3BArfˉ in dichloromethane at –35 °C. For dimethyl malonate, isolated yields and enantioselectivities range from 98-82% and 99-93% ee (six β-arylnitroethenes) and 82-72% and 94-90% ee (two β-alkylnitroethenes). Overall, these are the best values reported for any catalyst to date.
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VISHAL M GOHIL, A-1810, Texas A&M University. PHOPHOLIPID-PROTEIN INTERACTIONS IN ENERGY TRANSFORMATION REACTIONS. One of the aims of the proposed research plan was to determine the role of most abundant bilayer and non-bilayer forming mitochondrial phospholipids, phoshatidylcholine (PC) and phosphatidylethanolamine (PE) respectively, in the function and formation of electron transport chain (ETC) complexes. Using yeast mutants of PE and PC biosynthetic pathways we have shown that: 1) Mitochondrial PE is required for ETC complex III and IV enzyme activities, whereas PC is redundant. 2) Mitochondrial PE deficiency can be compensated by stimulating non-mitochondrial PE biosynthetic pathway by ethanolamine supplementation. 3) Membrane contact sites formed by the endoplasmic reticulum mitochondrial encounter structure (ERMES) facilitate ethanolamine-mediated rescue of mitochondrial PE deficiency. 4) The loss of PE or PC does not alter overall phospholipid levels suggesting an existence of a homeostatic mechanism that maintains total phospholipid levels. 5) The loss of PE or PC does not disrupt overall mitochondrial morphology, though a decrease in PE results in diminished cristae length. We recently published these findings. In addition to these findings, we also elucidated roles of the conserved mitochondrial proteins COA6 and MCUR1 in the ETC function and formation. Specifically, we showed that COA6 acts in concert with other mitochondrial proteins, COX12 and SCO2, in delivering copper to ETC complex IV (Ghosh et al, 2016;). In collaboration with Dr. Madesh's group, we showed that Mitochondrial Calcium Uptake Regulator 1, MCUR1, regulates mitochondrial bioenergetics by controlling biogenesis of the mitochondrial calcium channel and not the ETC complexes directly. IDO GOLDING, Q-1759, Baylor College of Medicine. GENE REGULATION BY TRANSCRIPTION FACTORS: SINGLE-MOLECULE CHEMISTRY IN THE CELL. (i) We used single-cell microscopy, followed by automated image analysis, to simultaneously measure the cellular concentration of the Cl transcription factor and the resulting number of mRNAs produced from the PRM promoter it regulates. The result was a direct measurement of transcriptional regulation in individual bacterial cells. We next used theoretical modeling to map the relation between Cl binding configurations and the stochastic activity of PRM. This work was recently published (Sepulveda et al., Science 2016). (ii) Using a similar approach, we measured the transcriptional activity of two genes, Oct4 and Nanog, in individual mouse embryonic stem cells. Simultaneously, we measured the cell-cycle phase of each cell. Theoretical modeling of the single-cell data allowed us to reveal how the stochastic activity of each gene varied along the cell cycle, and how the activity of an individual copy of the gene depended on the presence of additional gene copies within the same cell. This work was recently published (Skinner et al., eLife 2016; a collaboration with T. Zwaka). (iii) As in previous reporting periods, work on the project has led to the development of novel tools for the manipulation, imaging and analysis of individual cells. These tools were then used in collaborative projects with other labs. ELIZABETH J. GOLDSMITH, I-1128, The University of Texas Southwestern Medical Center. DOCKING INTERACTIONS BETWEEN THE MAP3Ks, ASK1/TAO2 AND B-Raf WITH THEIR COGNATE MAP2Ks MEK6 AND MEK1. Last year we published on the order of phosphorylation events in the p38 MAP kinase pathway, as reported last year. To determine whether the activity is associated with the first or second phosphorylation, we had to turn to the MEK1-ERK2 pathway, where we were able to make a partially phosphorylated MEK1 using a mutant B-RAF. Using the partially phosphorylated MEK1, we determined that the intermediate in MEK1 phosphorylation, MEK1/SS*, is not active. This was a major prediction of our model, and we will publish this in conjunction with other work being carried out in collaboration with Stanislav Shvartsman. Second, we have initiated projects that will refine our understanding of MAP kinase modules. One concept is to reconstitute the cascade. We have tried this with both ASK1-MEK6-p38 (a MAP3K, MAP2K and MAPK), and BRAF-MEK1-ERK2. In both cases, the phosphorylation of the MAPK stalls, and we are presently using mass spectrometry to find the cause of the stall out. Third, the full action of the cascades is done in the presence of phosphatases, and in preparation for analyzing these effects, we have cloned out full length MKP3 and MKP5, the phosphatases for ERK2 and p38 MAP kinase, and the kinase binding domain of MKP3. JOHN B. GOODENOUGH, F-1066, The University of Texas at Austin. INFLUENCE OF COUNTER CATION IN MIXED-METAL OXIDES. We have filed four patents on new battery materials. Additives that reduce capacity loss from formation of a passivation layer on a lithium or a sodium anode are described in current publications. A principal discovery this year has been the development of a unique solid glass electrolyte that is wet by, and therefore plates/strips safely, a metallic lithium or sodium anode and has a Li or Na conductivity equivalent to that of the flammable organic-liquid electrolyte used in today's Li-ion batteries. This discovery opens the door to a new generation of high-energy-density, safe rechargeable batteries. This glass is discussed in a recent publication. A cathode for sodium-ion batteries are discussed a recent publication, cathode morphologies for sulfur cathodes in other recent publications, and catalysts for rechargeable air cathodes provides a current publication review of perspectives for flow-through redox molecules for stationary-battery cathodes of large capacity. A published study by electron microscopy of the surface phase that forms on a manganese-spinel cathode during a charge and also published is a review of solid electrolytes under development for all-solid-state rechargeable batteries. A current publication is a study of a polymer-gel electrolyte for a lithium or sodium battery.
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Our fundamental studies of d-electron properties of transition-metal compounds have included IrTe2, in which the large orbital angular momentum on the Ir(IV) plays a critical role, and the perovskite CaCrO4 in which the 3d electrons of the Cr(IV) are at the crossover from localized to itinerant. A publication provides a discussion of the electric double layer that forms at the crystal/grain-boundary interface of doped ceria, and a publication presents a catalytic reduction at room temperature of CO2 to formic acid in high yield. DAVID G. GORENSTEIN, AU-1296, The University of Texas Health Science Center at Houston. COMBINATORIAL SELECTION, STRUCTURE AND DESIGN OF NEXT GENERATION X-APTAMERS. A bead-based DNA X-aptamer combinatorial library was synthesized with permonothioated backbones and allylamino substitutions (1,048,576 sequences). The bead-based library was screened with CD44 and the best binding sequences were identified after PCR, sub-cloning. By combining our random bead-based aptamer library development methods with conjugation chemistry techniques, we have created a next-generation of aptamers, X-aptamers (XAs). A 2-color FACS sorting of our X-aptamer bead library as well as a laser microdissection of tissues has been used to demonstrate the utility of the library for identifying novel proteomic biomarkers in cancer. PAOLO GRIGOLINI, B-1577, University of North Texas. ERGODICITY BREAKING IN CHEMICAL, BIOLOGICAL AND COOPERATIVE SYSTEMS. The tracking of single molecules diffusing in biological cells invalidates the traditional assumption that time and ensemble averages coincide, ergodic condition, and the authors of this field of investigation base their theoretical arguments on the popular Continuous Time Random Wall (CTRW). The average over infinite many copies of the same trajectory is mimicked by a window of a given time size moving along the sequence. This procedure yields a scaling different from the ensemble scaling, with a decreasing intensity proportional to the inverse of the length of the time series to a power smaller than one. If the scaling approach is operated scaling the length of the time series as well as the size of the moving window, self-contained scaling procedure, time average yields the same result as ensemble average. We have proposed a theory explaining the origin of the ergodic breaking of molecules diffusing in biological cells, as an effect of self-organization under the influence of a complex environment. This theory suggests also the prescription to adopt to study the response of a non-ergodic network to an external stimulus, a result that is expected to be useful to establish the correlation between two times series of biological origin This prescription has been turned into a rigorous approach. This theoretical perspective has been extended from the dynamics of biological cells to sociology. Finally a published article explores the joint action of ergodic and non-ergodic processes by extending the CTRW to the case where the random walker in its operational time perceives a correlated noise, and illustrates two different approximations, yielding the same scaling as the ensemble scaling, when the self contained scaling procedure is adopted. There exists, however, an infinite memory threshold value that makes the approximation advocated in either depart from the ensemble average when the self contained scaling procedure is adopted or yield localization when only the size of the moving window is scaled. In conclusion a published article affords the striking evidence of the fact that the joint action of ergodic and non-ergodic processes yields a strong ergodicity breaking rather than the weak form observed by using CTRW. NICK V. GRISHIN, I-1505, The University of Texas Southwestern Medical Center. STRUCTURE MECHANISM OF CIRCADIAN CLOCK-MEDIATED TRANSCRIPTION ACTIVATION. We completed the goals set in the proposal and are at the final stages of the manuscript preparation for publication. Most significantly, we expressed, purified and crystallized a complex between CLOCK Exon19 and CIPC repressor protein and determined its X-ray structure in two different crystal forms, at 2.7Å and 1.81Å resolution. This fully refined structure has Rfactor of 21% and Rfree of 26% for the better resolution form. In solution, CIPC repressor has been shown to bind to the region of CLOCK protein encoded by exon 19. CLOCK Exon19 domain was suggested to participate in recruiting co-activators. Therefore, binding of CIPS to Exon19 may block the co-activator binding sites and thus inhibit CLOCK function. The most unexpected finding was the stoichiometry of the Exon19-CIPC complex. In both crystal forms, we find the same structure with two Exon10 domains bound to one CIPC molecule. The three molecules form a three helical coiled-coil bundle. The bundle holds together by hydrophobic residues, but three very conserved polar residues, one from each molecule, form hydrogen-bond interactions with each other. We confirmed the 2:1 stoichiometry of the complex in solution is confirmed by analytical ultracentrifugation and NMR spectrum suggests that the complex is well-ordered in solution. Such unexpected stoichiometry has important biological implications. It suggests that CIPC simultaneously inhibits 2 CLOCK:BMALI complexes. Exonl9 domain connects to other domains though a long disordered region. This flexible loop allows the two CLOCK:BMALI inhibited complexes to be separated by variable distance. It is possible that CIPC can only inhibit CLOCK:BMAL1 when there are at least two activator complexes binding at the adjacent promoter/enhancer regions. Thus, our crystal structures opened new research directions to further understanding of CLOCK:BMALI function and calls for additional experiments to study cooperativity in binding of CLOCK:BMAL1 to CIPC and DNA.
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ARNOLD M. GULOY, E-1297, University of Houston. CHEMICAL BONDING AND PROPERTIES OF "ELECTRON-POOR" INTERMETALLICS ALONG THE ZINTL BORDER. The highlight of this year's accomplishments is the discovery of an unprecedented magnetic/electronic behavior in the reduced niobium oxyfluoride, Nb2O2F3. The compound was characterized as a new Nb oxyfluoride that features Nb2 dimers with very short Nb-Nb bonds (bond order: 1.5). Nb2O2F3 represents a unique example of a reduced niobium oxyfluoride derived from ligand (F/O) substitution in a simple binary oxide, ζNb2O5. It undergoes an unusual "spin-gap" formation (T ~90 K) arising from the disproportionation of paramagnetic metal–metal bonded Nb2 dimers: (2[Nb2]7 –> [Nb2]6+ + [Nb2]8+). Further studies on the unusual transition, including neutron scattering experiments at ONRL, indicated that the compound exhibits two competing transitions that can be tuned by the rate of cooling. The first transition at 90K is a CDW or disproportionation transition that was found to be kinetically slow, and competes with a rapid antiferromagnetic (AFM) transition that occurs at ~50K. Thus, rapid cooling leads to the AFM phase as the majority phase. Slow cooling results in the CDW phase as the majority phase. We also continued our investigations on the chemistry of complex polar (salt-like) intermetallic compounds containing active metals (e.g. alkali metals and alkaline earth metals), transition metal (Ni), and carbon or intermetallic carbornetallates. Initial results have resulted in the synthesis of two novel TM carbides (carbometallates) with unique TM-carbon anions: a linear [Ni(C2)2]6- anion in Li2Ca2NiC4; and a triangular planar [Ni(C2)3]8- in Li2Sr3NiC6. Manuscripts reporting these new compounds will be submitted soon. A Welch summer scholar was mentored in summer 2015. Our Welch-funded research work was also recognized with the John and Rebecca Moores Professorship to Prof. Arnold M. Guloy. JASON H. HAFNER, C-1761, Rice University. SURFACE ENHANCED SPECTROSCOPY FOR MEMBRANE STRUCTURAL BIOLOGY. Efforts in previous years have supplied reproducible SERS spectra of surfactants, lipids, and membrane-inserted peptides on gold nanorods. Certain aspects of the spectra can be interpreted in terms of a distance dependent enhancement, but a more rigorous process to determine molecular structure is needed. To accomplish this, the EM near field at the surface of the nanorod was calculated by the finite element method to determine the EM enhancement and how it depends on separation from the gold surface. The Raman tensor (derivative of the polarizability) for each normal mode of the molecule of interest was calculated by time dependence density functional theory (TD-DFT). By assuming an electric field normal to the nanorod surface, a theoretical SERS spectrum was calculated from (1) the tensor elements, (2) the relative orientation of the field and molecule, and (3) the distance dependent enhancement. While TD-DFT is not sufficiently accurate to yield Raman spectra that closely matched experimental spectra, only the variation with position and orientation is needed. Therefore, ratios between well-defined spectral peak amplitudes and their unenhanced counterparts (both experimental and theoretical) were compared. A fitting parameter was defined and tested at varying theoretical positions and orientations. These fitting maps were used to determine molecular structure from SERS spectra. For the surfactant cetyltrimethylammonium bromide, this new method of SERS analysis predicts that the alkane chain sits at 12 degrees from the surface normal, similar to what is found by other methods. It is being applied to lipid membranes and tryptophan residues in membranes. Ultraviolet spectral analysis was also explored as a source of molecular information, leading to some insights into the UV properties of gold particles. NAOMI J. HALAS, C-1220, Rice University. CHEMICAL AND PHOTOPHYSICAL PROPERTIES ON COMPLEX NANOPARTICLES AND NANOPARTICLE COMPLEXES. In the past year we have developed Fano resonant aluminum clusters with specific chromaticitics in the green-blue region of the spectrum that exhibit remarkable sensitivity to local changes in the dielectric environment and provide a colorimetric LSPR sensor. Another electrically switchable material are molecular plasmons in ionized polycyclic aromatic hydrocarbons (PAH). We have demonstrated that molecular plasmons are supported in PAHs and can be designed into a device geometry to provide a low voltage electrochromic device. Another direction of research with Aluminum antennas was the design of cross asymmetric antenna substrates for surface enhanced infrared absorption (SEIRA). The design allows for simultaneous detection of multiple IR absorption resonances over a broad spectral region. The aluminum oxide layer on the aluminum antennas provides a useful oxide molecule whose Al-O stretch mode can be used a self calibrating standard to quantify the number of analyte molecules being measured. We have also demonstrated the use of Aluminum nanocrystals as plasmonic photocatalysts for hydrogen dissociation at room temperature and atmospheric pressure. The concepts from solar steam generation using nanoparticles were applied to separation of binary liquids- ethanol and water. The mole fraction of ethanol obtained from the nanoparticle —resonant laser irradiation process is substantially higher, essentially removing the ethanol-H2O azeotrope. P. SHIV HALASYAMANI, E-1457, University of Houston. ADVANCED SECOND-HARMONIC GENERATING MATERIALS.
We have synthesized, grown crystals, characterized, developed structure-property relationships, and investigated theoretically several new oxide materials that exhibit second-harmonic generation (SHG). One of our aims to synthesize new SHG materials that have nonlinear optical (NLO) capabilities in the UV (200-400nm) and deep-UV (< 200nm) regimes. A notable discovery this grant year is the synthesis, crystal growth, and characterization of SHG active Ba3(ZnB5O10)PO4 (BZBP). This material has a very short absorption edge of 180nm and is thus capable of UV and deep-UV NLO applications. We were also able to grow large (centimeter) size crystals - a necessary requirement for NLO applications. In addition, we discovered a SHG active family A3B3CD2O14 (A = Sr, Ba or Pb; B = Mg or Zn; C = Te or W, and D = P or V). Additional results include the large crystal growth of two birefringent materials, Na6Te4W6O29 and Na2TeW2O9, and three SHG active polymorphs - α-, β-, and γ- Pb2Ba4Zn4B14O31. A number of collaborative papers were also published Additional results are given in section 3. We have expanded our non-linear optical characterization to include Maker Fringe measurements, our crystal growth capabilities with a Bridgman Furnace, and our SHG measurements with a dual 532nm and 1064nm laser. We are continuing our synthetic efforts on the discovery of new materials, their full characterization, and the development of structure-property relationships.
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MICHAEL B. HALL, A-0648, Texas A&M University. COMPUTATIONAL CHEMISTRY OF TRANSITION METAL SYSTEMS.
The main focus of this year's contributions was on density functional theory (DFT) calculations on the electronic structures, geometric structures, and mechanisms of reactions related to transition-metal hydrides and the catalytic transformations involving hydrogen, especially the reversible reduction of carbon dioxide to methanol. In crystal structures of the molybdenum complexes: [(1,2,4-C5H2iBu3)Mo(PMe3)2H3] (Cp'Bu3) and [(C5HiPr4)Mo(PMe3)2H3] (CpiPr4), the Mo-bound H positions were resolved for (CpBu3), but not for (CpiPr4). NMR experiments revealed the existence of an unknown mechanism for H-atom exchange. DFT calculations show that the (CpiPr4) complex's Hs are unresloved because of their disorder, which does not occur for (CpiBu3). A corresponding examination of H-atom exchange paths shows that the Hs rearrange by motion parallel to the Cp ring in a single step. DFT calculations predict that the catalytic production of H2 and CO2 from CH3OH and H2O by [K(dme)2][Ru(H)(trop2dad)] begins with the dehydrogenation of methanol to formaldehyde through a new ligand-ligand bifunctional mechanism, where two hydrogen atoms of CH3OH eliminate to the ligand's N and C atoms. The key initiator of this first step is formed by migration of the hydride from the ruthenium to the meta-carbon atom, which a frustrated Lewis pair (FLP) in the ring between N and C. Hydroxide, formed when the FLP cleaves H2O, reacts rapidly with CH2O to give H2C(OH)O-, which subsequently donates a hydride to the complex to generate HCOOH. HCOOH then loses both a proton and hydride to the complex to give formate then CO2. The fully-hydrogenated complex is first deprotonated by OH- and then releases hydrogen to regenerate the catalyst. In this mechanism, which explains the experimental observations, the whole reaction occurs on the chemically non-innocent ligand with the ruthenium atom appearing as a spectator. JOHN C. HARDY, A-1397, Texas A&M University. NUCLEAR DECAY STUDIES. This past year, we have continued our measurements and analysis of mirror pairs of superallowed f3-decay transitions, which are aimed at constraining the calculated isospin-symmetry-breaking corrections required in testing the universality of the weak interaction. The analysis of 26Si decay has continued as the Ph.D. thesis project of M. Bencomo, while we mounted a new measurement of the half-life of 34Ar to sort out a lingering inconsistency. With a successful result, we are now ready to prepare manuscripts on the half-life and the branching ratio for 34Ar decay. Work also continues on the decay of 42Ti. These three decays, of 26Si, 34Ar and 42Ti, together with that of 38Ca, which we have already published, are mirrors to already well-studied superallowed decays. In addition, we also completed and published an addendum ‒ encompassing four more transitions ‒ to our recent critical survey and theoretical analysis of world data on superallowed β decay. In the second component of our program, we have completed the analyses of a new measurement, on 125Te, and have published the results of an earlier measurement on 111Cd. We will also perform another measurement, on 103Rh, this summer. These measurements serve to increase the range and depth of our tests of calculated internal conversion coefficients. RASKIA M. HARSHEY, F-1811, The University of Texas at Austin. STRUCTURAL CHARACTERIZATION OF A NOVEL REGULATOR OF H+ FLOW ACROSS THE BACTERIAL MEMBRANE: A POTENTIAL ANTI-MICROBIAL DRUG TARGET. Mutagenesis studies were carried out on conserved residues. It was demonstrated that the disulfide bond was not necessary for FlhE structure of function; however, the C-terminal residues N112, Y113 and R114 were important. Expression and purification tests were performed with GST, GST-FlhE and GST-FlhE ∆112-114. Low recovery of the mutant FlhE protein suggests that the conserved C-terminal resides are important for FlhE structural stability.
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P. JOHN HART, AQ-1399, The University of Texas Health Science Center at San Antonio. STRUCTURE AND ACTION OF A SCHISTOSOMA MANSONI SULFORTRANSFERASE IMPLICATED IN DRUG RESISTANCE. During the first year of the award, we determined the structure of S. mansoni sulfotransferase (SmSULT) in complex with the antischistosomal drug oxamniquine (OXA), revealing the molecular basis for its action. Last year the new structure guided the synthesis of several OXA derivatives, some of which were effective on both S. mansoni and S. haematobium. OXA possesses a single chiral center but is given therapeutically as a 50:50 racemic mixture. We noted that despite being present in equal amounts, only S-OXA was found in the crystal structure, suggesting it binds with higher affinity than its R-OXA counterpart. During this reporting period, we separated the enantiomers, determined the structures of the enzyme in complex with both purified enantiomeric forms, and tested the efficacy of the purified enantiomers in worm killing assays (see Taylor et. al, 2016). S-OXA was approximately 3-fold more toxic to S. mansoni than R-OXA and the enantiomers were found to bind in significantly different ways. These findings profoundly impact the strategies for OXA analog syntheses that will be effective against both S. mansoni and S. haematobium, the cause of 99% of all schistosomiasis cases. JEFFREY D. HARTGERINK, C-1557, Rice University. SYNTHESIS OF NANOSTRUCTURED ORGANIC MATERIALS VIA SELF-ASSEMBLY.
During this funding year we published five peer reviewed papers. The first, published in Biomacromolecules, describes the first molecular level investigation of a composition and register specific triple helical mimic of the collagen based disease Osteogenesis Imperfecta. The second paper, published in The Journal of Dental Research, utilizes our self-assembling MDPs as a material for tooth pulp and dentin regeneration. The third paper, published in ACS Biomaterials Science and Engineering, uses our MDPs to deliver snake venom to bleeding wounds. This composite material has the remarkable property of being able to clot blood even in animals taking blood thinners such as heparin. The fourth paper, also published in ACS BSE, describes the use of our MDPs to trigger a strong angiogenic response in vivo when they contain and deliver the proper growth factors. The fifth paper, published in Biomaterials, describes the use of our angiogenic MDPs in a clinically relevant model of peripheral arterial disease (PAD). While the work published during this grant year had a strong biomedical focus, it builds directly from, and is the fruition of, the fundamental nanostructural and materials properties that have been developed by us with
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Welch funding over the past decade. KADEN HAZZARD, C-187, Rice University. ULTRACOLDE NONREACTIVE MOLECULES: FROM COLLISION COMPLEXES TO COMPLEX MATERIALS.
After the first year, our research is ahead of schedule. We calculated the effective lattice model not only for a single site, but in the more challenging case that includes tunneling between many sites [PRL 116, 135301 (2016)]. This calculation was originally planned for year two. In the limit of a deep lattice, we found that the effective lattice model is a "multichannel Hubbard model".
One remarkable consequence of this model that we discovered is that experiments can determine properties of the bimolecular collision complexes with drastically improved resolution: Lattice modulation spectroscopy can potentially resolve sub-nanoKelvin features. Ultracold NRMs without a lattice already offer extraordinary spectral resolution, but the lattice improves this more than a thousand-fold. We have been discussing possibilities for proof-of-principle experiments with various experimental groups in this rapidly growing field.
We are about to submit two papers answering questions that were planned to be studied in year two. First, what are the consequences for the effective model of various common chemical approximations to the bimolecular complex dissociation kinetics, and how can these be distinguished in experiment? Second, what many-body phenomena emerge from this novel model? For example, can it harbor new phases of matter? Additionally, we have been laying the foundation for the remainder of years two-three, in which we aim to apply collision models calculated from more microscopic theories, and to calculate the effects when three or more molecules occupy a site of a lattice. We have begun developing both new qualitative ideas and numerical codes that will allow us to tackle these questions. ADAM HELLER, F-1131, The University of Texas at Austin. ELECTROCHEMICAL APPLICATIONS OF METAL OXIDE TEMPLATED CARBON ELECTRODES.
We have synthesized ~10 atom % nitrogen-doped electronically conductive templated carbons with 4 nm pores, large enough for rapid permeation of electrolytes and reactants. The carbons are made by pyrolizing nitrilotriacetate (NTA) salts of La3+, Mg2+ and Sn4+ at 650-710°C and acid-extraction of the formed templating La2O3 or MgO. Examples include (a) A MgO-templated N-doped carbon, of a specific surface area 2/3rd that of graphene, made by pyrolyzing MgHNTA. It catalyzes the 4-electron electroreduction of O2 to water in 1 M KOH about as well as the best platinum-based oxygen electroreduction catalyst (20 weight % Pt on C) (Eisenberg D, et a/. (2016). (b) A La2O3-templated carbon. Substituting half of the widely used commercial Super P-Li carbon, it provides high-rate Li-ion battery anodes by reducing their resistance to Li+ transport and improving their heat transfer (Youn DH, et al. (2016). (c) A tin nanocrystallite (3.5 nm tin particle size) N-doped carbon composite, made by low temperature pyrolysis of SnCl4 with NTA, providing non-aggregating tin nanoparticles perfectly dispersed in the carbon. Li battery anodes made with the N-doped carbon-tin nanocomposite retain after 200 cycles at 0.2 A/g specific current a specific capacity of 660 mAh/g; then after 400 cycles 630 mAh/g. At the high specific current of 1 Ng the specific capacity remains as high as 435 mAh/g (Youn DH et al. (2016) GRAEME HENKELMAN, F-1841, The University of Texas at Austin. DESIGN OF MATERIALS FOR ENERGY CONVERSION AND STORAGE.
Computational methods: Two new methods were developed this year to find the reactive events which govern the function of batteries and catalysts. First, we derived a ridge-based bias potential to accelerate molecular dynamics within the hyperdynamics approach that scales much better than existing potentials for large systems. Second, we developed an analytic correction to harmonic transition state theory that allows for fast and more accurate calculations of reaction rates at elevated temperatures. Additionally, one project from this year which made extensive use of our methods was to elucidate a complex phase transition in Mo; this work was recently published in Phys. Rev. Lett. Catalysis: Our largest effort this year was related to surface chemistry and catalysis. We have collaborated with the Mullins group to understand oxygen interaction with alloy Pd/Au surfaces; the Crooks group to understand the structure and function of alloy nanoparticles for CO oxidation; the Humphrey group to model hydrogenation reactions on Rh alloy nanoparticles; and the Kovar group to understand the binding of ethylene to Au/Cu alloys. On our own, my group used computations to model catalytic surface chemistry for systems including the reactivity of vanadia clusters supported on TiO2, the unusual association of NH3 to a water layer supported on Pt, CO oxidation at the interface of Pd-alloy supported nanoparticles on ceria, and the mechanism of nano-oxidation on low index Cu surfaces. Included are some clear examples of theoretical catalysts design. Batteries and Intercalation Compounds: Our work on battery materials continued by looking, this year, at a promising cathode Li2MnSiO4, where we show that limitations are not in fact due to a structural change, as previous thought, but rather the evolution of oxygen at low Li concentrations. Then, perhaps the more exciting result from this area is a new collaboration with the Milliron group to understand the structure of amorphous and flexible metal oxides which can be used as electrochromics. Our work in this area is in the final states of review at Nature Mat.
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W. MIKE HENNE, I-1873, The University of Texas Southwestern Medical Center. NOVAL PATHWAYS OF ER-ENDOLYSOSOMAL INTER-ORGANELLE COMMUNICATION. This Welch Fellowship funds general research on PXA domain proteins through my postdoctoral fellow Dr. Lydia (Yang) Liu. Dr. Liu and I have worked closely together since she joined my lab in January 2015. We have successfully characterized yeast Mdm1 and Nvj3 as bone fide residents of the ER-vacuole/lysosome membrane contact site (MCS), and demonstrated that Mdm1 functions as an inter-organelle "tether" connecting the ER and vacuole/lysosome (published in first corresponding author paper Henne, JCB, 2015). To determine whether the Mdm1 PXA domain binds to lipids (Aim 1), we have expressed and purified PXA domain from E.coli and developed in vitro lipid binding assays. These assays reveal that the PXA domain binds to a variety of lipids with preference for mono-acyl fatty acids, diacyl neutral lipids like DAG, and sterols. We have also established a collaboration with Dr. Jeff McDonald (UTSW, Mole Genetics) to conduct lipidomics. For Aim 2, we conducted Mdm1 immunoprecipitation and proteomics via the UTSW Proteomics Core facility. (Aim 3) We have also shown that Mdm1 regulates lipid droplet biogenesis in yeast together with Dr Joel Goodman's lab (UTSW, Dept Pharmacology). Further studies will further define how Mdm1/Nvj3 function in lipid droplet biogenesis. RYAN E. HIBBS, I-1812, The University of Texas Southwestern Medical Center. STRUCTURAL BASIS OF CHEMICAL TRANSMITTER RECOGNITION BY PENTAMERIC LIGAND-GATED ION CHANNELS. In this grant year (year 3), we made progress in our cryo-electron microscopy studies of the a7 nicotinic receptor structure and published our first study using methods developed for the a7 receptor project. This new publication (listed below) describes development of a new viral expression system for recombinant production of heteromeric mammalian membrane proteins. The problem, in brief, is that mammalian membrane proteins typically express at very low levels and are profoundly unstable when removed from their native membrane environment. We developed two new methods, one for rapid viral titration and another for counting subunits in an oligomer, that when coupled, allowed us to efficiently produce milligram quantities of heteromeric nicotinic receptors. In this paper we showed how simple modification of existing baculovirus expression systems achieves high level expression in mammalian cells, with reproducible titers measured in 48 hr, rather than the typical two to three weeks for classical viral titration procedures. Next we showed how, by labeling different subunits in the heteromer with different colored fluorescent proteins, we could rapidly screen conditions on a small scale that would bias expression toward a distinct subunit stoichiometry. This overall approach, followed by purification of the receptor, allowed us to produce the first diffraction quality crystals of a nicotinic acetylcholine receptor. We have already shared this new expression system with several other labs in Texas as well as nationally. For our own efforts, we find this expression system is broadly successful in achieving high level expression of the human membrane proteins we are studying. On the cryo-EM research efforts, we use this approach to make our protein, and are now transitioning to doing all data collection analysis locally as our new FEI Titan Krios comes online this summer. CHRISTIAN B. HILTY, A-1658, Texas A&M University. STRUCTURE AND FOLDING OF MEMBRANE TARGETED PEPTIDES. Lipid bound paramagnetic agents were used to determine peptide insertion into micelles. Using these agents, magainin-2 was confirmed to interact with DPC micelles, which supports the dependence of thermal denaturation on lipid type as observed by NOE and by CD spectroscopy. Secondly, previously developed nuclear spin relaxation based methods to determine the structural stability and mobility in peptides were expanded to allow for the determination of relaxation parameters in polypeptides undergoing structural change in real time. Real time observation is arguably the most direct way to characterize changes in polypeptide structure, without the need to use changes in external parameters such as temperature in order to change equilibrium configuration. Resolved NMR spectra can be acquired above the Nyquist limit (> 10 ms time scale). We have now for the first time applied a relaxation based analysis of signal changes to NMR data from an intrinsically unfolded protein, p27, which undergoes a structural change upon binding to a target. Using NMR spectra from this protein acquired with hyperpolarization to yield a sufficiently strong signal, it was possible to determine signal decay rates during the folding process. These rates were correlated to spin-lattice relaxation calculated based on relaxation theory, which provided evidence for the existence of a partially folded, less mobile form of the polypeptide. ANDREW P. HINCK, AQ-1842, The University of Texas Health Science Center at San Antonio. STRUCTURAL AND MECHANISTIC STUDIES OF TGF-BETA SUPERFAMILY SIGNALING PROTEINS. We have performed an extensive series of surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) binding studies with the full-length betaglycan ectodomain, as well as its two component binding domains, BGO and BGZP-C. We have found that BGO and BGZP-C bind at independent sites and that they are positioned so that a single site for TβRII is still accessible. We are currently working to generate paramagnetically tagged betaglycan, TβRII, TβRI, and TGF-β to assess intermolecular distances between the individual domains of betaglycan and TGF-β to test our model that betaglycan potentiates TGF-β receptor complex assembly by enhancing the kinetics of TGF-β:TβRII complex formation using pulsed double electron-electron resonance (DEER) EPR measurements. We are also working to determine the structure of BGO bound to TGF-beta using crystallography by forming and isolating the 1:1:1 TGF-beta:TβRII:BGO complex and screening this for crystal formation. We obtained moderately diffracting crystals of the protein ternary complex (ca. 6 Å diffraction) after limited digestion with trypsin and PEG as the precipitant at neutral pH. We have identified the trypsin cleavage sites (there are three) and we have shown that only one of them is required to enable crystal formation. We are currently working to improve the diffraction limit by optimizing the crystallization of a protein complex with only one trypsin cleavage site (the other two have been eliminated by substituting the targeted arginine residues with histidine).
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DAVID M. HOFFMAN, E-1206, University of Houston. SYNTHESIS OF METAL COMPLEXES WITH STERICALLY ENCUMBERED KETIMIDE LIGANDS.
We have synthesized iron(III) complexes having a new di-anionic tridentate pincer ligand. Dimethyl 2,6-pyridinedicarboxylate was reacted with four equivalents of o-tolylmagnesium chloride to give the pincer- ligand precursor 2,6-(HOC-o-tolyl2)2pyridine in moderate yield. Iron(III) FeCl(N(SiMe3)2)2(THF), synthesized following a slightly modified literature preparation from anhydrous FeC13 and NaN(SiMe3)2 in THF, reacted with 2,6-(HOC-o-toly12)2pyridine in toluene to give HN(SiMe3)2 and the red iron(III) dimer [Fe(ONO)Cl]2 (ONO = 2,640C-o-toly12)2pyridine). A single-crystal X-ray crystal structure revealed that the dimer consists of two fused square-pyramidal iron centers with apical chloride ligands. One alkoxide arm of each of the two pincer ligands bridges between the iron atoms, resulting in a Fe‒Fe distance of 3.10 Å, and there is a cis-[C1FeFeCl] configuration. In contrast to the results of the reaction carried out in toluene, the reaction of FeC1(N(SiMe3)2)2(THF) with 2,6-(HOC-o-toly12)2Pyridine in THF resulted in the isolation of orange FeCl(ONO)(py) crystals from toluene/pyridine, presumably resulting from displacement of THF from FeC1(ONO)(THF) by pyridine. Attempts to isolate FeC1(ONO)(THF) failed. The X-ray structure of FeCl(ON0)(py) reveals a pseudo square-pyramidal geometry in which the pyridine ligand is coordinated in the apical position. Surprisingly, attempts to produce FeC1(ONO)(py) by reacting the dimer [Fe(ONO)C1]2 with pyridine failed. Magnetic studies of FeCl(ONO)(py) and [Fe(ONO)Cl]2 are in progress. BRADLEY J. HOLLIDAY, F-1631, The University of Texas at Austin. LUMINESCENT IR(III) COMPLEXES AND COVALENTLY FUNCTIONALIZED GRAPHENE FOR ADANCED MATERIALS.
Organic light-emitting diodes (OLEDs) are currently a viable technology for display applications and have numerous advantages over alternative technologies, including high efficiencies, tunable emission color, and compatibility with glass and flexible plastic substrates. However, OLEDs often require complex and expensive fabrication methods. LEECs are a promising approach to decrease these fabrication costs. We have synthesized and characterized several highly luminescent ionic iridium(III) complexes based on the parent complex, [Ir(ppy)2(bpy)]+, as use as emitters for LEECs. Photophysical and electrochemical properties of these luminescent complexes have been determined; additionally, these materials have been incorporated into working LEEC devices for analyses regarding practical emitter performance in collaboration with the Slinker research group at UT- Dallas. Graphene has shown impressive physical and chemical properties, including high electron mobility, broadband optical transparency, excellent thermal conductivity, and a high elastic modulus. As a result, graphene has been investigated for use in a wide array of promising applications, ranging from supercapacitors to sensors. Further tuning of the chemical and electronic properties of graphene is desirable to enhance its usefulness in specific applications. We have shown that spontaneous functionalization in the covalent electrochemical modification of graphene can be avoided by using diaryliodonium salts, in lieu of the more commonly-used diazonium salts. This can be used to precisely tune the work function and doping levels in graphene for the potential use as an electrode for energy devices such as batteries and photovoltaics. The mechanism of the electrochemical covalent grafting of diaryliodonium salts to single layer graphene has also been investigated. LORA V. HOOPER, I-1874, The University of Texas Southwestern Medical Center. ENGINEERING ANTIBACTERIAL LECTINS FOR SPECIFIC TARGETING OF ANTIBIOTIC-RESISTANT BACTERIA. During the past year we have made good progress on our goal of engineering RegIIIα variants with novel antibacterial specificities. A key accomplishment was establishing that a variety of chimeric RegIIIα proteins can be successfully expressed, purified, and refolded to their native conformations. We have expressed each of our chimeric RegIIIα proteins in E. coil, and have purified each of them to homogeneity. In E. coil, RegIIIα is expressed as misfolded protein that is isolated as inclusion bodies, and must then be refolded to its native conformation. We screened for appropriate refolding conditions for each of our RegIIIα variants and then confirmed proper refolding using circular dichroism. The spectra showed maximal negative ellipticity in the range of 205-215 nm, gave evidence of extensive β-strand structures, and were similar overall to the spectra of wild-type RegIIIα. Together, these results indicate that chimeric RegIIIα proteins can be refolded to native conformations that resemble that of the wild-type protein. We have made two additional discoveries. First, we have found that we can engineer the RegIIIα carbohydrate-binding domain to recognize peptide epitopes, thus expanding the possible specific targets on antibiotic-resistant bacteria. Second, we have identified a new family of small membrane-toxic proteins that bind to bacterial antigens that can serve as platforms for further engineering of novel antibacterial proteins. This is the resistin-like protein (RELM) family, members of which are related to resistin, a cytokine that plays a role in glucose homeostasis. We have shown that RELMβ is toxic to membrane bilayers in a manner similar to RegIIIα. We propose to re-engineer the bacterial binding function of RELMO to recognize antibiotic resistant bacteria and are working toward pinpointing which regions of the protein are responsible for bacterial recognition. Once we have accomplished this, we will work to re-engineer the RELMβ binding function using the approaches that we have devised for engineering RegIIIα. JENNY HSIEH, I-1660, The University of Texas Southwestern Medical Center. CHEMICAL REGULATION OF ADULT HIPPOCAMPAL NEUROGENESIS AND MEMORY.
This is the final progress report for the grant year June 1 2015 through May 31 2016. This past year, we shifted directions to explore the role of neurogenic small molecules Isx-9 and valproic acid in seizure-induced neurogenesis and epilepsy. We established a mouse model of chronic temporal lobe epilepsy using the chemical convulsant pilocarpine. In pilocarpine treated mice, there is robust proliferation and maturation of newborn neurons in the hippocampus. Recent work in our lab has shown that this seizure-induced neurogenesis is aberrant and pro-epileptic, and suppression of aberrant neurogenesis using a genetic ablation approach can lead to a reduction in chronic seizures and behavioral improvement (Cho et al., 2015, Nat Commun). Since genetic
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ablation of aberrant neurogenesis is not a feasible approach in human patients, it is worthwhile to explore the effects of small molecule intervention of seizure-induced neurogenesis. We performed two studies this past year. In study #1, we treated wild type C57BI6 mice with pilocarpine to induce acute seizures and aberrant neurogenesis. Beginning the day after pilocarpine, we injected mice with 20 mg/kg Isx-9 (IP) once a day for 14 days. Video-EEG was performed between 5 and 7 weeks post pilocarpine and mice were sacked for brain histology. In study #2, we repeated the experiments in study #1, except treated the mice with 30 mg/kg valproic acid (IP) once a day for 30 days. In both studies, we observed no change in spontaneous recurrent seizures between drug treated and vehicle treated control mice. However, valproic acid treated mice showed reduced levels of aberrant neurogenesis compared to vehicle treated control mice. In contrast, Isx-9 treated mice did not show significant differences in neurogenesis compared to vehicle treated control mice. JULIA W.P. HSU, AT-1843, The University of Texas at Dallas. SULFUR POISONING OF COMPLEX OXIDE CATALYSTS FOR NITRIC OXIDE (NO) OXIDATION: EFFECT OF CRYSTAL STRUCTURE AND STOICHIOMETRY.
Combined experimental studies and DFT calculation of lattice constants and decomposition temperatures for pure-phase AMn2O5 (A = Sm, Gd, Pr, Bi, and Y) compounds have been published this year. In addition, we varied the crystallization temperature and precipitation pH to vary the phase purity and surface area of SmMn2O5, in order to study the critical factor(s) that determine NO adsorption properties on these materials. We found that surface area is the primary factor, but surface Mn/Sm ratio also plays an important role in determining NO uptake. This study has also been published this year. In addition, we have been investigating the identity and stability of intermediate species on the surface of Mn-containing oxide compounds upon NO adsorption using Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and DFT modeling. Results from SmMn2O5 mullite are compared with those from a-MnO2, Mn2O3, Mn3O4, and SmMnO3 perovskite. In situ heating in the FTIR and XPS chambers is necessary for these studies. DFT calculation found that the MnO5 pyramids that bridge two Mn-Mn chains lower the energy barrier for NO2 desorption, enabling mullite surfaces to recover its catalytic activity. To verify the DFT findings, we have synthesize pure-phase compounds for experimental studies. Since there is no resource for constructing catalytic activity testing at UTD, we have initiated collaboration with two groups (Prof. W. Epling at Univ. of Houston and Dr. Ka Xiong at Dongguan Innovative New Materials) to peroform catalytic activity measurements. We have also started the synthesis of Fe containing mullite compounds. In the next year, we expect to submit these results for publication. The extreme corrosiveness of NO causes severe damages to our instrument (see damaged valves in picture) and mechanical pump that took several months to repair, resulting in delays in the experimental progress. Since SO2 is even more corrosive than NO, we will focus on theoretical studies of sulfur poisoning. HUEY W. HUANG, C-0991, Rice University. MOLECULAR MECHANISM OF MEMBRANE-ACTING ANTIBIOTIC DAPTOMYCIN.
We have published a study on the interaction of daptomycin with lipid bilayers using giant unilamellar vesicles (GUVs) and discovered a lipid extracting effect. We observed that as the concentration of daptomycin bound to the membrane exceeded a critical value, extramembranous peptide-lipid aggregates appeared to desorb from the GUV surface while the GUV remained intact. How can we reconcile this lipid extraction effect observed in GUVs with the reported ion leakage effect by daptomycin or the proposed formation of ionic pores? During the last grant year, we used small angle X-ray scattering to detect the monomeric and oligomeric daptomycin in calcium ion solutions. We were able to determine that in our experimental conditions daptomycin was monomer before interaction with membranes. We also used the CD spectra of daptomycin to determine the binding stoichiometry of Ca2+ to daptomycin. These two measurements clarify the molecular state of daptomycin before its interaction with lipid bilayers. We then performed calcium and potassium ion leakage experiments induced by daptomycin. In order to understand the nature of daptomycin induced ion leakage, we compared its effect with that of ion channel gramicidin, potassium ionophore valinomycin, calcium ionophore ionomycin and penetratin. The results show that the ion leakage behavior of daptomycin is unlike that of ion channels or ionophores. It induces transient ion leakage only when it initially binds to the lipid bilayer. This result indicates that the daptomycin-induced ion leakage is correlated with the lipid extracting effect observed in the GUV experiment; there are no ion channels formed by daptomycin. RANDALL G. HULET, C-1133, Rice University. UNIVERSAL TRIATOMIC MOLECULES BY ASSOCIATION OF ULTRACOLD ATOMS.
We have made substantial progress on several fronts this year. We continue to study the temperature dependence of the formation of tri-atomic Efimov molecules. We find an unexpected linear dependence and are collaborating with a theorist on understanding this result. A graduate student, Henry Luo, spent one week in Knoxville, TN developing the theoretical tools needed to understand this result. We also have made a major advance in our work on matter-wave solitons. These solitons are non-dispersing wavepackets that are formed from Bose-Einstein condensates of ultracold atoms confined in one-dimension. We had previously discovered that a modulational instability (the exponential growth of a single frequency) was responsible for the formation of trains of multiple solitons. The details of the instability were revealed by our time-resolved measurements on
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the "birth and death" of these soliton trains. We are now able to explain the origins of their remarkable alternating phase structure. The preparation of a major manuscript reporting these results is underway. Finally, we have continued to model electronic materials, such as high-temperature superconductors, using ultracold atoms confined to an optical lattice. Our focus is cooling the atoms below the Neel transition temperature to an antiferromagnet. In our system that temperature is approximately 10 nano-Kelvin. Several theoretical collaborations are helping to develop of new cooling schemes that we are exploring in the laboratory. SIMON B. HUMPHREY, F-1738, The University of Texas at Austin. DESIGN AND SYNTHESIS OF NEW METALLOLIGANDS FOR THE CONSTRUCTION OF PHOSPHINE COORDINATION MATERIALS WITH ADVANCED SOLID-STATE PROPERTIES.
(i) New Catalytically-Active PCMs Inspired by Organometallic Chemistry. We have used a rational design approach to prepare a new series of PCMs based on so-called PCP-pincer complexes. The latter are highly popular in homogeneous catalysis, but had not previously been incorporated into MOF-type materials. This project presents a number of significant synthetic challenges because the desired PCP building blocks were previously unreported. A synthetic study that has taken over 2 years finally came to fruition in this grant year, as we were able to prepare a tetra(carboxylated) PCP-pincer ligand in high yield from a new multi-step route. The pincer was subsequently cyclometallated with Pd(II)Cl and used to grow a series of PCMs with 1-, 2- and 3-D connectivities. The most interesting material, denoted PCM-36, was able to mimic reaction chemistry known to molecular complexes but in the solid-state, within the micro-pores of the material. Specifically, we demonstrated CO2 insertion into Pd-CHs bonds, which is a compelling discovery in the MOF field. This work was accepted for publication in Angewandte Chemie and is presently online as an early view article. In the next grant year, we will exploit this breakthrough result to synthesize further PCP-pincer PCMs, especially those that incorporate Rh(I) and Ir(I) catalytic centers. (ii) Studying H2 sorption in PCMs by Inelastic Neutron Scattering Studies. Some of our lanthanide-based PCMs that have already been published with Welch Foundation support were shown to have unusually high uptake capacities of certain small molecule adsorbates. The Dy(III)-based material PCM-21 is a good example of this. In the last grant year, we were able to obtain beamtime at a European Research Council synchrotron facility in Switzerland, to study this material using inelastic neutron spectroscopy (INS). This advanced high-energy technique is useful for studying the actual positions of H2 molecules loaded inside materials. The information gleaned from this type of study is intrinsically important in elucidating the most important gas binding sites in the pores of PCM-type materials by providing detailed structure-function relationships. This information informs us on how to better tailor future materials for improved performance. In collaboration with colleagues who are expert in INS, we published a paper in Chemistry of Materials. On the back of this publication, we were awarded an improved allotment of a further 96 h of beamtime this coming September. (iii) MOFs and PCMs as Chemical Sensors. Our interest in the underlying properties of ordered crystalline PCM solids for chemical sensing has continued in the past grant year. In addition to previously published work in this arena, we uncovered a new material named PCM-22, which can be prepared in isostructural form with a broad range of mixtures of Ln(III) ions. The beauty of this unusual property is that we have been able to prepare sensors that provide rapid, visual (color-change) responses that can also be spectroscopically quantified to obtain low limits of detection. The PCM-22 family of materials can be tailored to specific trace chemical sensing problems. One good example of this is the sensing of trace H2O in D2O, acetonitrile, and a number of other solvents for which there is no current reliable fast detection method. We have recently submitted a new manuscript on this work. In addition, and in follow-up to our previous work in this area, we were invited to write a book chapter on 'MOFs as Chemical Sensors,' for the Royal Society of Chemistry. This book was published in the past grant year. GYEONG S. HWANG, F-1535, The University of Texas at Austin. FIRST-PRINCIPLES INVESTIGATION OF THE STRUCTURE, CHEMISTRY AND PROPERTIES OF GRAPHENE-BASED NANOMATERIALS. Recent experimental evidence of capacitance enhancement using nanoporous carbons (NPC) has encouraged significant efforts for their use in electrochemical double layer capacitors (or supercapacitors). The current paradigm for materials design is based on theories which attribute this improved capacitance largely to average pore sizes comparable to that of a single electrolyte ion. We have alternatively proposed that the capacitance is related to the dispersity of shapes that describe the pore structure, which has been concluded based on a systematic study of NPC electrodes (with broad pore size distributions) immersed in ionic liquid using extensive molecular dynamics simulations that emulate voltammetry. Our analysis clearly demonstrates that the capacitance strongly depends upon the kinetics of ion reorganization during charge/discharge cycles, especially around highly-confining pores. Efficient ion migration is found to be facilitated by pores that vary in shape (e.g., from cylindrical to slit-like) along their channels. Based on this understanding, we have demonstrated that a new structural descriptor, coined as the pore shape factor, can unify experimental results which were previously uncorrelated with respect to average pore size. Our findings provide a new avenue for materials optimization and also highlight the importance of ion migration kinetics in understanding and evaluating the performance of NPC-based supercapacitors. TATYANA I. IGUMENOVA, A-1784, Texas A&M University. PIN1 "BITES" THE TAIL: REGULATORY ROLE OF THE C-TERMINAL DOMAIN OF PROTEIN KINASE C.
Significant progress has been made towards Objective 1 of the proposal. Full-length Pin1 and its individual domains WW and PPlase were cloned into a bacterial expression vector and purified in natural-abundance and isotopically-enriched forms, for further characterization by nuclear magnetic resonance (NMR) spectroscopy. The NMR resonances of the backbone atoms were fully assigned in all three domains using triple-resonance NMR methods. All three proteins were folded and fully functional. Three segments of the C-terminal domain were synthesized using solid-phase peptide synthesis. The segments contained either one conserved phosphorylation site (hydrophobic or turn motif), or both on the same polypeptide.
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With respect to binding studies, out of a total possible 9 binding experiments (3 Pin1 constructs × 3 functional motifs from the C-terminal PKC region), we conducted six that proved to be sufficient to unambiguously identify the interaction mode between Pin1 and C-terminal domain of PKC. We also carried out experiments to assay the catalytic activity of Pint with the C-terminal domain as a substrate. We are now ready to initiate structural studies described on Objectives 1 and 2. We will pursue parallel approaches with solution NMR and X-ray crystallography. The intra-molecular interaction between the C-terminal and Ca2+-binding C2 domains of PKC is an important regulatory mechanism that may control the accessibility of the C-terminus to Pin1. We have completed characterization of the C2 domain dynamics by NMR. This work is currently under review (Biophysical Journal). BRENT L. IVERSON, F-1188, The University of Texas at Austin. UNDERSTANDING A NEW FAMILY OF REPORTING MOLECULES. Solids that Change Colors We expanded studies of monoalkoxynaphthalene-naphthaimide donor-acceptor dyads by generating a series of new derivatives with systematically altered side-chains. The goal is to determine the extent to which side chain differences influence dynamic behavior in the solid state in order to gain a predictive understanding of how structural parameters control behavior. A series of crystal structures have now confirmed that the dramatic color changes observed in the solid state are derived from a novel 180° rotation of the dyads from a head-to-head stacking geometry (orange solid) to a head-to-tail geometry (yellow solid). The crystal structures also revealed that substantially altered side-chain repacking occurs during the orange-to-yellow solid-state transition along with the 180° dyad rotation. A new series of derivatives are being investigated in order to pinpoint the key parameters involved, and we are happy to report that a third color form (green) has recently been identified!
RoboDNA In parallel, we have continued to look into the remarkable behavior we initially reported in 2014 in which naphthalene diimide (NDI,
blue in the figure T to the right) and dialkoxy naphthalene (DAN, red in the figure to the right) can be used to stabilize DNA duplexes. Thus, electrostatic complementarity of stacked aromatic units (no hydrogen bonds) can replace complementary hydrogen bonding patterns in the context of DNA. When placed in the middle of a duplex, an increase in duplex stability was seen to be comparable to three A-T base- pairs, but now we have discovered that when placed on both ends, the NDI-DAN-NDI stack stabilizes the resulting duplex by a remarkable 38° C, significantly more than an equivalent number of either A-T or G-C base-pairs. MAKKUNI JAYARAM, F-1274, The University of Texas at Austin. COMPLEX ACTIVE SITES FOR PHOSPHORYL TRANSFER: CONTINUED CHEMICAL, BIOCHEMICAL, BIOPHYSICAL AND STRUCTURAL ANALYSES. A. We have continued to exploit single molecule tethered particle motion (TPM) to examine the thermodynamic and kinetic features of the pre-chemical and chemical steps of site-specific recombination. In the last report, we summarized the progress made with the tyrosine recombinases Flp and Cre. We are now extending this single molecule approach to the analysis of serine site-specific recombinases. Our studies with the phage φC-31 integrase provide a step-by-step picture of the recombination reaction from start to finish. They reveal how the recombination directionality factor regulates the compatibility between target DNA sites. In vivo, this regulation acts as a switch between the integration and excision of the phage genome into, and from, the bacterial
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chromosome. The observations also suggest that the cleaved state of the DNA within the recombination complex is short-lived and that the DNA rotation prior to strand-joining is gated. B. The Flp site-specific recombinase, which we have studied for several years now, is coded for by the yeast 2 micron plasmid. Flp is crucial for plasmid copy number control in vivo, and is regulated by the host post-translational SUMO-modification system. We constructed a Flp-SUMO hybrid, which faithfully mimics the native in vivo regulation. We are utilizing the hybrid protein for in vitro assays to understand how the SUMO-modification affects the DNA-binding and strand cleavage/joining activities of Flp. C. We are interested in the segregation mechanisms of the 2 micron plasmid, a highly optimized selfish genome. Our analysis using fluorescence-tagged reporter plasmids and partitioning proteins suggest that replicated plasmid molecules are evenly distributed between mother and daughter cells by hitchhiking on chromosomes. We have utilized site-specific recombination as a tool for excising single copy reporter plasmids from their chromosomally integrated states, so that the segregation of the replicated sister copies can be followed with quantitative precision. Chromosome and plasmid dynamics followed by fluorescence tagging and in vivo video-microscopy are consistent with the hitchhiking model for plasmid segregation. JEAN X. JIANG, AQ-1507, The University of Texas Health Science Center at San Antonio. IDENTIFICATION OF SODIUM AND GLUTAMINE BINDING OF SNAT1 AMINO ACID TRANSPORTER USING MATAGENSIS SCANNING APPROACH. SNAT1 is a member of system N/A amino acid transport family that primarily expresses in retina and neuron, and mediates the transport of L-glutamine. We show that SNAT1 is an N-glycoprotein expressed in neurons. Here we use N-glycosylation as guidance to determine the localization of amino acid residues and domains. We identified three glycosylation sites at asparagine residues 251, 257 and 310 in SNAT1 protein, and that the first two are the primary sites. The biotinylation and confocal immunofluorescence analysis showed that the glycosylation-impaired mutants as well as de-glycosylated SNAT1 were equally capable of expressing on the cell surface. However, L-glutamine and MeAIB transport was significantly compromised in N-glycosylation impaired mutants and de-glycosylated SNAT1 as compared to the wild-type control. Together, these results suggest that SNAT1 is an N-glycosylated protein with three glycosylation sites at 251, 257 and 310 and these three residues are localized at the extracellular domains of SNAT1. JIN JIANG, I-1603, The University of Texas Southwestern Medical Center. STUDY OF CHEMICAL MODIFICATION IN CELL SIGNALING. Cell-cell signaling occurs in specialized subcellular compartments. One such cell-signaling center is the primary cilium, a microtubule-based plasma membrane protrusion found in most mammalian cells. Primary cilia regulate many essential cellular processes and their malfunction attributes to numerous human disorders collectively called ciliopathy. Recently, the primary cilium has been implicated in transducing extracellular signals, most notably, the Hedgehog (Hh) signal. Hh family of secreted proteins plays pivotal roles in both embryonic development and adult tissue homeostasis. Deregulation of Hh signaling activity has been linked to numerous human diseases including birth defects and cancer. Most of the Hh signaling components including the Gli family of Zn-finger transcription factors are localized at the primary cilium in order to transduce the Hh signal; however, the mechanisms by which these proteins are targeted to the primary cilium have remained poorly understood. We have identified a novel nuclear localization signal (NLS) called PY-NLS located in the N-terminal region of all three Gli proteins as well as their Drosophila counterpart Ci. Mutating the PY-NLS motif in G1i2 diminished its ciliary localization, which can be rescued by replacing with the PY-NLS from Ci. RNAi knockdown of importin-β2, which interacts with PY-NLS, also affected ciliary localization of G1i2 but not Smo, suggesting that the PY-NLS/importin-β2 nuclear import mechanism is responsible for Gli ciliary targeting. In addition to the PY-NLS motif, a C-terminal region in G1i2 is also required for its ciliary localization. We are in the process of reconstitution of ciliary localization signals sufficient to target a heterologous protein to the primary cilium. We are also testing the effect of importin-β2 inactivation on Hh signaling both in cultured cells and in vivo. NING JIANG, F-1785, The University of Texas at Austin. IDENTIFY THERAPEUTIC ANTIBODIES AND VACCINE CANDIDATES BY MINING HUMAN ANTIBODY REPERTOIRE IN MALARIA.
During the first year of the award, we have continued our study of using error-free antibody repertoire sequencing method, MIDCIRS, to examine the antibody repertoire development in young children from malaria endemic region. We have submitted the manuscript to Nature Medicine and is working on the revision and revised manuscript will be submitted before the end of July. In addition to this study and we have developed a method to directly measure T cell receptor affinity on primary human T cells in a high-throughput fashion. This method will revolutionize the way people study T cell biology and will have a profound impact on T cell based immunological disease therapies. This study was published in Science Translational Medicine in 2016. QIU-XING JIANG, I-1684, The University of Texas Southwestern Medical Center. CryoEM STUDIES OF IP3R IN NEW CHEMICALLY ENGINEERED MEMBRANES. We made three major discoveries. 1) We found that the interacting-partner of IP3R in the secretory granules, chromogranin B (CHGB), by itself is sufficient to insert into the membrane and form an anion channel. In INS-1 cells, the CHGB anion conductance is required for luminal acidification of secretory granules and for maturation of proinsulin into insulin. Our cell-based studies also found that the role of CHGB in the biogenesis of secretory granules and its function in the acidification are separated, paving a new avenue to study these two functions independently. Our studies suggest that there is no need of another CLC type chloride channel (or H+/CI- exchanger) in the granules. The conservation of CHGB from protists to human suggests that its channel function probably is fundamentally important for the intracellular membrane systems. We are working on defining the molecular determinants of the anion selectivity
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and the pore-lining residues that are important for ion conduction. 2) Using chemically engineered ChemiC films, we were able to select CHGB dimers onto the grids and collected a high-resolution dataset to calculate a 3D reconstruction at ~9.5Å. The secondary structure prediction of CHGB is largely coiled-coils, making it necessary to collect a large dataset to reach near atomic resolution. Our study found that CHGB forms a parallel dimer in solution and probably has to oligomerize in order to insert into the membrane and form an anion channel. 3) We successfully inserted IP3R into bead-supported small vesicles. Polystyrene beads were used to anchor the receptors and reconstitute membranes around them. We used a Titan-Krios scope at Holland and successfully performed 3D classification and obtained a 3D reconstruction of the IP3R at 10.5 Å, a map showing clear features for the 6TM pore domain as well as the S1-S4 helical bundles similar to the RyR. The structure takes the same shape as what we obtained in the past, making it possible to move onto the structure determination at a subnanometer resolution. These progresses set the stage for us to study the IP3R and its interaction with the CHGB in chemically engineered membranes. YOUXING JIANG, I-1578, The University of Texas Southwestern Medical Center. STRUCTURAL AND FUNCTIONAL STUDIES OF RCK-REGULATED POTASSIUM CHANNEL. Over the past year, we have performed structural studies on a novel plant nucleolus membrane channel DMII (also named Castor or Pullux) that plays an essential role in the symbiosis between legumes and bacteria (rhizobium) or fungi (arbuscular mycorrhizal) for nitrogen fixation. We have demonstrated that the channel functions as a tetramer and its C-terminal ligand binding domain of each subunit contains two tandem RCK domains just like the other RCK-regulated K+ channels. Interestingly, this channel is unlikely to be K+ selective. Our structural study reveals multiple Ca2+ binding sites on each subunit, suggesting that the channel is regulated by Ca2+. We are now taking multiple approaches to characterize the ion selectivity and gating properties of this dual RCK-containing, ligand gated channel. Part of Welch funding was diverted to support the study of the ion selectivity mechanism of K+ channels using non-selective NaK channel and its mutants as the model systems. We have structurally characterized the binding profile of Rb+, Cs+ and Ba2+ in NaK2K, a K+ selective NaK mutant, and provided structural insights into the so-called Ba2+ lock-in phenomenon in K+ channel. Over the past several years, we have also been using CNG-mimicking NaK2CNG mutants to recapitulate the ion selectivity properties of cyclic nucleotide gated (CNG) channels. Recently, we have determined the structural basis of the weak Ca2+ block observed in the Drosophila CNG channel by constructing a NaK chimera, which we called NaK2CNG-Dm, that contained the Drosophila selectivity filter sequence. We have demonstrated both structurally and functionally that a simple replacement of a threonine for a proline in Drosophila CNG channel has likely given rise to a distinct selectivity filter conformation that results in weak Ca2+ block. This study was recently published on Nature structural and Molecular Biology. JIN JIANPING, AU-1711, The University of Texas Health Science Center at Houston. DISSECTION OF MECHANISMS FOR POLYUBIQUITIN CHAIN SYNTHESIS. Protein ubiquitination plays pivotal roles in many important biological processes. However, ubiquitin signal is very complicated, because the ubiquitination machinery could synthesize different polyubiquitin chains on protein substrates and different polyubiquitin chains could lead to different destination of ubiquitinated proteins. They could provide as a protein degradation signal in certain circumstances, however, it also could serve as a non-degradation signal. Recently, we identified SidC, an effector protein of human pathogenic bacteria, Legionella pneumophila, as a novel ubiquitin ligase with no structural or sequence homolog in any existing family of ubiquitin ligases. Our data indicated that SidC mainly synthesizes K11 and K33 polyubiquitin chains. However, the mechanisms for SidC to make K11 and K33 polyubiquitin chains are still unclear. Our research proposal intents to study the mechanism. During the first year of the research, we mainly focused on the task of Aim 1, that is, to determine which ubiquitin surface residues are important for K11 and K33 polyubiquitin chain synthesis by SidC. Our hypothesis is that surrounding amino acids of lysine-11 and lysine-33 play important roles in chain specificity determination. Therefore, we have constructed ubiquitin mutants that surround both lysine-11 and lysine-33 of ubiquitin. We have successfully expressed and purified these mutant proteins in bacteria. Therefore, we are ready to do in vitro assay to determine their roles in polyubiquitin chain synthesis in the second year of our research. KENNETH A. JOHNSON, F-1604, The University of Texas at Austin. KINETICS OF HEPATITIS C VIRAL RNA-DEPENDENT RNA REPLICATION. In the past year we published two papers describing the effect of non-nucleoside inhibitors on the HCV RNA-dependent RNA polymerase. This enzyme catalyzes de novo initiation of RNA synthesis and then must transition to rapid and processive elongation to complete the replication of the viral RNA. We discovered that nonnucleoside inhibitors binding to the outside of the thumb domain do not block initiation or elongation; rather, they inhibit the transition from initiation to elongation. The transition is thought to occur with an expansion of the active site and a movement of a beta-loop out of the active site. We proposed that the inhibitor acts allosterically by blocking this conformational transition in the HCV polymerase structure. This proposal was tested using hydrogen/deuterium exchange kinetics where we showed that the binding of the inhibitors to the surface of the protein cause a general rigidification of the protein structure, extending to the active site, thus supporting our hypothesis and providing direct evidence to define the polypeptide segments showing the largest changes in mobility. Interestingly, the magnitude of the effect on the hydrogen/deuterium exchange correlated with the potency of the inhibitors. Finally, in unpublished work, we have performed molecular dynamics simulations in order to predict the nature of the structural changes. These studies have suggested new features of the enzyme structure in each state, initiation, transition, and elongation mode, where the beta loop is required in the active site for
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the initiation reaction, but then swings out of the active site and may interact with the growing RNA duplex. We are just starting to test proposals by single amino acid substitutions, particularly examining residues in the beta loop domain. KEITH P. JOHNSTON, F-1319, The University of Texas at Austin. TUNING INORGANIC AND ORGANIC NANOCLUSTERS ASSEMBLED FROM PRIMARY NANOPARTICLES. A fundamental understanding has been developed for assembling various types of plasmonic Au nanoclusters composed of 5 nm primary particles by manipulating the colloidal interactions as a function of the ligands on the particle surfaces. The morphology and near infrared extinction of Au nanochains has been controlled by varying the surface chemistry and modifying the thickness of the double layers on the particle surfaces. Furthermore, the size of spherical nanoclusters was tuned reversibly by balancing short-ranged attraction with long ranged repulsion, as guided by a statistical mechanical model. For magnetite nanoclusters, primary particles with the ideal size and high crystallinity were synthesized to achieve unprecedented high values of the magnetic susceptibility. For both magnetite and silica nanoclusters, novel ligands and polymers were designed to achieve colloidal stabilization at extremely high salinities and high temperatures. In our work on colloidal synthesis of electrocatalyst nanoclusters, we have designed a series of high surface area Lai-xSrxCoO3-
δ perovskites by reverse phase hydrolysis for alkaline electrolysis of water and the oxygen reduction reaction. We have rationalized exceptionally high activities in terms of a mechanism that addresses oxygen vacancies, metal-oxygen bond covalency and redox activity of lattice oxygen sites. Finally, for organic colloids, we have related the rheological properties of monoclonal antibody dispersions to the structure of protein clusters as characterized by light and small angle X-ray scattering and explained the behavior in terms of the relevant intermolecular forces. RICHARD A. JONES, F-0816, The University of Texas at Austin. MOLECULAR PRECURSORS TO NEW FUNCTIONAL MATERIALS. We have continued to make progress in the two main areas focused on the study of molecular precursors to functional materials. Studies on the design and synthesis of mononuclear precursors for the chemical vapor deposition (CVD) of thin films rhodium and nickel using the novel monodentate ligand 3,4-bis(trifluoromethyl)pyrrolyl have now been published. We have also published details of an alkaline flow battery based on the coordination chemistry of iron and cobalt. This work was done in collaboration with the group of Professor A. J. Bard of this department. Our work on the chemistry of the lanthanides has progressed in two main areas. Firstly, we have continued to explore the design and synthesis of large cluster assemblies, which are stabilized by long-chain Schiff base ligands. In a significant number of cases the materials self-assemble into drum-like clusters which we have used the term "nano-drums" to describe. We have isolated, characterized and published examples of nano-drums with 30, 32 and 56 metals and many of them exhibit enhanced near-infra-red luminescence properties. We have also begun to explore the use of these materials as molecular nanoparticles for optical imaging applications in biological systems and have published two papers describing our work. Lastly, we have published studies describing near-infra-red (NIR) luminescent Zn-Ln Wolf type II metallopolymer hybrid materials. KARL M. KADISH, E-0680, University of Houston. ELECTROCHEMISTRY AND SPECTROELECTROCHEMISTRY OF COMPOUNDS WITH MULTIPLE REDOX CENTERS. One goal of our research is to unify descriptions of porphyrin, corrole and phthaiocyanine electrochemistry with that of related hybrid macrocycles while also improving our ability to predict and tulle redox activity of the compounds for applications in a variety of areas. To help accomplish these goals we have continued to elucidate the electrochemistry. spectroelectrochemistry and electrocatalytic activity for different series of compounds having multiple redox centers. Selected examples of compounds characterized over the last twelve months include (i) pentametallic derivatives of porphyrazines, (ii) porphyrins, corroles and phorphyrazines with both π-extended and π-linked systems, (iii) core expanded porphyrins, (iv) porphyrins and corroles with covalently linked ferrocene or pilosphoryl groups. (v) N-confused tetraarylporphyrins and (vi) new heteroleptic triple decker complexes having mixed corrole and phthalocyanine macrocycles, compounds which had never before been synthesized. We also continued to examine the redox properties of (vii) new dirhodium and diruthenium complexes, some of which were linked with porphyrins or corroles and (viii) we demonstrated how electrosynthesis could he used to generate novel corroles and porphyrins with fused π-ring systems whose preparation was difficult or not possible using standard synthetic techniques. Other ongoing projects initiated during the last year include detailed studies of: (ix) free base porphyrins with an emphasis on how solvent, supporting electrolyte and structure influence the redox and acid-base properties of these compounds, (x) water soluble porphyrins with sulfonate or carboxylate groups, (xi) cationic porphyrins N-alkyl pyridyl groups and (xii) mixtures of associated anionic and cationic porphyrins, one example being given by tetra anionic and tetra cationic derivatives of Man(III) complexes. These studies and others will be continued during the coming year. CRAIG D. KAPLAN, A-1763, Texas A&M University. BIOCHEMISTRY OF THE RNA POLYMERASE II ACTIVE SITE. We have published two papers, and a third paper (in collaboration with the Calero lab at the University of Pittsburgh) has been accepted at Molecular Cell. This latter work illustrates the first time the architecture of the complete Pol II transcription bubble while revealing a native structure of the Pol II trigger loop –the key domain for substrate recognition and catalysis– in the absence of substrate. The architecture of this stabilized, NTP-unbound state indicates how trigger loop states might communicate to other parts of the Pol II enzyme, and allows rationalization of a wealth of known trigger loop mutants. This is an important structure that will influence how we think about transcription mechanisms. We have pursued immediate experiments regarding function of SsI2 subunit of TFIIH in directing promoter scanning by the Pol II initiation complex. We remain interested in TFIIF as stated in our proposal, however our recent work has indicated that SsI2 studies are likely to be of high impact and high intellectual value. Our preliminary data point to Pol II scanning being a possibly universally conserved initiation mechanism, where previously it had been
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assumed to be limited to yeast or fungi. Because of this, we are now generating biochemical reagents to dissect SsI2 function and analyze how it controls initiation behavior. We have succeeding in identifying a number of classes of SsI2 alleles that confer different initiation phenotypes. We believe these phenotypes are underlain by distinct biochemical defects in SsI2 activity (a DNA translocase required for promoter opening). ADRIAN T. KEATINGE-CLAY, F-1712, The University of Texas at Austin. PREPARATIVE BIOCATALYTIC SYNTHESIS OF COMPLEX POLYKETIDES. My group has made progress on several fronts this grant year. We have continued to understand and employ polyketide synthase (PKS) enzymes towards the synthesis of stereocomplex polyketides. A substrate-activity study provided us the knowledge of how to mutate ketoreductases to yield new stereochemical combinations (Bailey et al., 2016). A related study showed that the epimerization catalyzed by many ketoreductases is catalyzed in the same active site as the reduction reaction (Xie et al., 2016). Work on methyltransferases isolated from both cis-acyltransferase and trans-acyltransferase PKSs has enabled us to utilize these enzymes to form carbon-carbon bonds through either mono-or dimethylation of β-ketoacyl thioesters (Stevens et al, submitted; Wagner et al., submitted). We have also been employing non-PKS enzymes (mainly from polyhydroxyalkanoate pathways) such as β-ketoacyl thiolases and id-ketoacyl reductases in the synthesis of chirally-pure diketides (Fage et al., 2015 and unpublished results). I have written a review on the current state of our knowledge of how modular PKS enzymes set stereocenters (Keatinge-Clay, 2016). We have been able to generate triketides using a chemoenzymatic approach that we think will one day be developed into a general polyketide synthesis like that of oligonucleotide or polypeptide synthesis ‒ these exciting results will be published in the next grant year. On the structural biology front, we have been able to show how most trans-acyltransferase PKSs self-assemble into at least two-dimensional arrays via protein-protein interactions (Gay et al., 2016; Zeng et al., submitted). Understanding the higher-order structure of PKS assembly lines will greatly aid us in genetically engineering them to produce designer polyketides. SEAN M. KERWIN, F-1298, The University of Texas at Austin. REARRANGEMENTS OF ALKYNYLAZOLES. We continue our investigation of N-alkynylazole chemistry by further explorations of the synthetic utility of N-alkynylpyrrole cyclizations. In our previous work, we focused on employing N-alkynyipyrroles in the synthesis of naturally occurring spiroketals, such as the natural product pollenopyrroside A. During this most recent period, we focused on the cyclization of N-alkynylpyrrole-2-carboxylate esters. We have developed a two-step synthesis of pyrrolo[2,1-c]oxazin-1-ones 1 from N-unsubstituted 2-(trimethylsilyl)ethyl pyrrole-2-carboxylates (Scheme 1), and have employed this transformation in the formal total synthesis of the natural product insect antifeedant peramine. CHING-HWA KIANG, C-1632, Rice University. SINGLE MOLECULE STUDIES OF MOLECULAR INTERACTIONS OF BIOLOGICAL MACROMOLECULES. Understanding the thermodynamics and mechanics of biological macromolecules through single molecule and single cell force studies has allowed us to model the nanoscale materials and molecules. Using atomic force microscope force studies, we found that recombinant dimeric von Willebrand factor (RDVWF) unfolding force is not altered by high shear stress and they do not self-associate into a conformation analogous to that attained by sheared large VWF multimers. We have also found that the perlecan protein core has a mean elastic constant of 890 pN and a corresponding Young's modulus of 71 MPa, and that perlecan has physical properties that would allow it to act as a strong but elastic tether in the LCS. We have also performed experimental studies of the solution-based mechanical properties of GNR and their parent products, graphene oxide nanoribbons (GONR). We used atomic force microscopy (AFM) to study their mechanical properties in solution and showed that GNR and GONR have similar force-extension behavior as in biopolymers such as proteins and DNA. The rigidity increases with reducing chemical functionalities. The similarities in rigidity and tunability between nanoribbons and biomolecules might enable the design and fabrication of GNR-biomimetic interfaces.
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THOMAS C. KILLIAN, C-1844, Rice University. CREATION OF HALO MOLECULES WITH AN OPTICAL FESHBACH RESONANCE. We constructed the laser trap for the ultracold molecules, which is based on an optical-lattice configuration formed by the interference of six laser beams. This creates a three-dimensional array of micro-traps that will allow us to isolate individual molecules and study their properties in the absence of molecule-molecule collisions that would greatly shorten the molecular lifetime. During initial experiments, we found that the atoms heat significantly, most likely due to vibrations of mirrors sending lattice light to our vacuum chamber. After a great deal of effort, we have reduced the heating to a tolerable level. We have now loaded the appropriate strontium isotope (Sr-86) into the lattice and started experiments applying the optical Feshbach resonance laser. In the course of our work, we discovered that the ultracold strontium system is ideal for studying a new class of molecules, referred to as ultralong-range Rydberg molecules, in which bond lengths can approach a micron in size and bonding is caused by very weak scattering of a highly excited Rydberg electron with one or more ground-state atoms. Studying the properties of these molecules, such as lifetime and collision rate, has proved very fruitful, yielding six publications during the last year, including two that earned the Editor's Distinction from Physical Review. NAYUN KIM, AU-1875, The University of Texas Health Science Center at Houston. LOCUS-SPECIFIC QUANTITATION OF URACIL ASSOCIATED WITH UNSCHEDULED DAN SYNTHESIS.
The model summarized above explains the correlation between active transcription and elevated uracil since single strand DNA in actively transcribed regions are known to be susceptible to spontaneous or oxidation-mediated chemical modification thereby locally elevating repair-dependent DNA synthesis. It also has an important implication for the chemotherapy regimens where multiple DNA damaging drugs with distinct mechanisms of action are used in combination. This year, using the AP reactive chemical aldehyde reactive probe (ARP), we acquired a strong support for this model by showing that treatment with DNA damaging chemicals induce Uracil incorporation into DNA in a dose-dependent manner. We also made a significant step in refining the uracil-quantitation method. We began collaborating with Dr. A. Bhagwat at Wayne State University, who is a preeminent expert in the study of uracil in DNA and recently developed a novel chemical probe AA3. AA3 uses click chemistry to specifically tag apurinic/apyrmidinic (AP) sites, obligate repair-intermediates of uracil in DNA, and allow affinity purification of AP-containing DNA fragments. Our investigation into the consequences of Uracil incorporation led us to postulate that the repair of Uracil-derived AP sites are also influenced by the genomic context, mostly on the level of transcription. We extended our previous work demonstrating how transcription-coupled nucleotide excision repair (TC-NER) is actively involved in removal of the Uracil-derived AP sites in a strand-specific way. We found transcription factors Deft and Dst1 to be involved in repair of AP sites in the transcribed regions and discovered that multiple repair pathways interact in repair of AP sites, particularly, in the highly transcribed regions. Manuscript describing this work is currently under review at Nucleic Acids Research (Owiti et al. 2016). DOUGLAS J. KLEIN, BD-0894, Texas A&M University at Galveston. CHEMICAL MODELS: CLASSICAL TO QUANTUM-THEORETIC.
The development and application of a diversity of models for molecules and nano-structures continues, with connection to classical chemical ideas. First, interest continues in different topologically arranged nano-structures, especially for conjugated-carbon pi-networks, including: ordinary benzenoids, fullerenes, pi-network polymers, buckytubes, defected graphenes, nano-cones, and "super-polyhedra". Some attention continues to be directed to resonating valence-bond (VB) theory, including foundations for the models and also for E. Claris "aromatic-sextet" ideas. Weak pairing of electrons (and consequent magnetic & electrical properties) for some novel nano-structures is being investigated, often utilizing our resonating VB ideas as well as conventional molecular orbital (MO) ideas. Fundamental topological-structural characterizations of dislocations & disclinations as decorations or defects in extended conjugated carbon-network species are being pursued, and developed, including in terms of both MO and VB theory. Further, progressive molecular reaction networks have been mathematically characterized as a type of partially ordered set, and associated theory has been and continues to be utilized, e.g., to enable selected isomer enumerations and to interpolate/extrapolate molecular properties. Study continues of some novel borane and carborane based moieties with icosahedral cores, especially regarding nano-conglomerates of their monomers. Several related chemical graph-theoretic topics have been considered or are under consideration, especially involving novel chemistry or mathematics, which then is pursued. STEVEN A. KLIEWER, I-1558, The University of Texas Southwestern Medical Center. MECHANISMS UNDERLYING THE SECRETORY ACTIONS OF FGF21 IN EXOCRINE PANCREAS.
Fibroblast growth factor 21 (FGF21) is a hormone that regulates metabolism in response to stress, including starvation and ketogenic and high carbohydrate diets. FGF21 is most abundantly expressed in exocrine pancreas, where its expression is induced by feeding and chemically-induced pancreatitis. However, its function in this tissue was not known. We have now shown that FGF21 stimulates digestive enzyme secretion from the exocrine pancreas by acting directly on the pancreatic acinar cells in an autocrine/paracrine manner. Mice lacking FGF21 accumulate excessive zymogen granules in exocrine pancreas in response to a fasting/refeeding regimen, and this effect is reversed by administration of recombinant FGF21. FGF21 administration does not stimulate digestive enzyme secretion in mice selectively lacking the FGF21 co-receptor, β-Klotho, in exocrine pancreas. Like the classical exocrine pancreas secretagogue, cholecystokinin (CCK), FGF21 induces digestive enzyme secretion by stimulating intracellular calcium release via a phospholipase C-inositol triphosphate receptor signaling pathway. However, unlike CCK, FGF21 does not induce digestive enzyme synthesis. Thus, the ratio of FGF21 to CCK maintains pancreatic digestive enzyme concentrations at safe levels in the acinar cells. Importantly, our findings suggest that FGF21 may be used therapeutically to treat and possibly prevent pancreatitis, including endoscopic retrograde cholangiopancreatography-induced and somatostatin-induced forms of this condition. We have experiments ongoing to address this possibility.
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During the past year, we also made the unexpected finding that FGF21 administration markedly reduces sweet and alcohol preference in mice, and sweet preference in monkeys. In mice, these effects require that FGF21 act directly on the central nervous system and correlate with reductions in dopamine concentrations in the nucleus accumbens, a region of the brain that controls reward behavior. These findings raise the intriguing possibility that FGF21 can be used clinically to treat sweet and alcohol addiction in humans. CHE MING KO, A-1358, Texas A&M University. THEORETICAL STUDIES OF HEAVY ION COLLISIONS. For heavy ion collisions at intermediate energies, we have participated in a comprehensive study to understand transport simulations through the comparison of heavy-ion transport codes under controlled conditions. This has led to an improvement on the robustness of transport model predictions at incident energies where abundant amounts of data are available. For heavy ion collisions leading to the production of a baryon-rich matter, we have continued to study the mean-field effects on the elliptic flows of various hadrons and obtained important information on the properties of the baryon-rich quark matter. We have further used the linear response theory to study the spinodal instability of baryon-rich quark matter and found that the spinodal unstable region in the temperature and density plane shrinks with increasing wave number of the unstable mode and the growth rate of unstable modes initially increases with the wave number but is reduced when the wave number becomes large. For heavy ion collisions at relativistic energies, we have used the Boltzmann transport approach to study the effect of initial spatial and momentum correlations between a heavy quark pair on their collision rate in a partonic medium, which is relevant for their thermalization and the production of quarkonia from regeneration in these collisions. We have further proposed to model hadronization of parton showers in QCD jets through a hybrid approach involving quark recombination and string fragmentation. When applied to parton showers from the PYTHIA Monte Carlo event generator, the final hadron spectra from our calculation compare quite well to PYTHIA jets that have been hadronized with the default Lund string fragmentation. Furthermore, using the coalescence model based on the phase-space distributions of protons, neutrons, lambdas, and their antiparticles from a multiphase transport model, we have obtained a better understanding of how light nuclei and their anti-nuclei are produced in ultrarelativistic heavy ion collisions. JENNIFER J. KOHLER, I-1686, The University of Texas Southwestern Medical Center. DISCOVERING TOXIN RECEPTORS WITH PHOTOCROSSLINKING SUGARS.
We used the photocrosslinking sugar technology developed by my research group to define the dominant receptors of cholera toxin (CT) on human colonic epithelial cells. While the ganglioside GM1 has long been identified as the sole CT receptor, we found that fucosylated glycoproteins are more important contributors to host cell inoxication by CT (eLife 4: e09545). We are currently using the same approach to define receptors for pertussis toxin on the surface of respiratory epithelial cells. We also worked to improved our photocrosslinking sugar technology. We studied cell-type dependent metabolism of a photocrosslinking analog of N-acetylmannosamine (ManNAc), a precusor to photocrosslinking sialic acid, leading us to propose strategies to improve photocrosslinking sugar incorporation (Glyconconj. J. 32: 515). We showed that photocrosslinking yields could be improved by using a sialidase to remove normal sialic acids, leaving behind only diazirine-modified sialic acid (ACS Chem. Biol. 11: 185). To improve incorporation of a photocrosslinking N-acetylglucosamine (GIcNAc) analog, we identified a mutant of the O-GicNAc transferase (OGT) that preferentially transfers the photocrosslinking sugar (J. Biol. Chem. 290: 22638). We used chemoselective labeling of sialylated glycans to enable comparative proteomics experiments that allowed us to identify host cell surface molecules desialylated by pneumococcal sialidases (Bioconj. Chem. 27: 1013). We used the same labeling reaction on a glycan microarray to identify glycan structures desialylated by pneumococcal sialidases (Carb. Res. 428:31). Finally, we published two review articles that discuss photocrosslinking sugar technology (Trends in Glycoscience and Glycotechnology 27: El) and the used of metabolic labeling approaches to achieve incorporation of unnatural sugar analogs (Glycobiology, in press). ANATOLY B. KOLOMEISKY, C-1559, Rice University. THEORETICAL UNDERSTANDING OF CHEMICAL MECHANISMS OF SELECTIVITY IN TRANSPORT THROUGH CHANNELS.
We developed a theoretical approach to explain the origin of selectivity in molecular fluxes through channels. The method is based on discrete-state stochastic models that take into account all relevant chemical transitions, and it provides analytical solutions for all dynamic properties. We specifically analyzed channels with one or two binding sites employed for separating mixtures of two types of molecules. The effect of the symmetry of interactions and the role of entrance and diffusion rates were also analyzed. It is found that the selectivity is higher for repulsive interactions than for attractive interactions, and for large entrance rates into the channel, as well as when the interactions are stronger at the first site in the channel. We also investigated collective dynamics of biological molecular motors. It was done by analyzing non-equilibrium multi-particle asymmetric exclusion processes with interactions. Our method allowed us to estimate analytically all dynamic properties. It was shown that correlations play important role in dynamics of interacting motor proteins. We found that correlations for repulsions are weaker and more short-range, while for attractions they are stronger and more long-ranch. It is also argued that the symmetry of interaction potentials influences the dynamics of motors. In addition, we investigated the molecular mechanisms of the hydrolysis of guanosine triphosphate (GTP) by the Ras/Gap protein complex using high-level quantum-based calculations and the first-passage analysis. Our calculations confirm the initial stage as a phosphorus-oxygen bond cleavage, followed by the processes of enzyme regeneration. The energy profile for the overall reaction is calculated explicitly, and it is applied for analysis of the kinetics of the
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reaction. The first-passage method suggests that the overall reaction is a balance between relatively fast transitions and low probability of states from which these transitions are taking place. Our theoretical predictions are in excellent agreement with available experimental observations on GTP hydrolysis rates. JUNICHIO KONO, C-1509, Rice University. OPTICAL, INFRARED, AND TERAHERTZ DYNAMICS OF CARBON NANOMATERIALS. During the last year, we made progress in three different projects. First, we successfully generated and detected coherent bursts of polarized terahertz (THz) radiation using aligned SWCNTs through excitation by femtosecond pulses of near-infrared radiation, as a result of coherent 1D carrier dynamics. Second, we developed a simple and highly error-tolerant method for fabricating a freestanding THz polarizer with nearly ideal performance, reliant on the intrinsically 1D character of conduction electrons in well-aligned SWCNTs. The polarizer was constructed on a mechanical frame over which we manually wound acid-doped CNT fibers with ultrahigh electrical conductivity. Finally, we showed that large (>cm2) monodomain films of aligned SWCNTs can be prepared using vacuum filtration. The produced films were globally aligned within ±1.5° and highly packed. The method works for nanotubes synthesized by various methods, and film thickness is controllable from a few nanometres to ~100 nm. We used the approach to create ideal THz polarizers and, by combining the method with sorting techniques, aligned and chirality-enriched nanotube thin-film devices. BRIAN A. KORGEL, F-1464, The University of Texas at Austin. NANOMATERIALS ASSEMBLIES.
Highly uniform silicon nanocrystals with chemically passivated surfaces were synthesized colloidally and studied in superlattice and surfactant assemblies. Silicon nanocrystals were incorporated into surfactant assemblies of cetyl trimethilammounium bromide (CTAB) and cholesterol, called quatsomes. The quatsome-Si nanocrystal assemblies could be dispersed in water for weeks and retained their bright fluorescence. Cryogenic transmission electron microscopy (cryo-TEM) confirmed that the structures do not change over the course of several weeks. The long-term stability of the assemblies, their fluorescence and biocompatibility makes them attractive candidates for medical applications. Tuning the silicon nanocrystal synthesis conditions enabled very uniform, faceted particles with cuboctahedral shape to be obtained. These nanocrystals were assembled into superlattices and studied by transmission electron microscopy (TEM), electron diffraction and grazing incidence wide angle and small angle X-ray scattering (GISAXS and GIWAXS). The soft, ligand-capped cuboctahedra assemble into face-centered cubic (FCC) superlattices with orientational order. The preferred nanocrystal orientation varied with superlattice orientation on the substrate, indicating that the interactions with the substrate and assembly kinetics can influence the orientation of faceted nanocrystals in superlattices. These superlattices of cuboctahedral silicon nanocrystals were also studied under high pressure on a diamond anvil cell at a synchrotron by combined in situ SAXS and WAXS. It appears that a new crystal phase of silicon has been observed with a unique body-centered cubic (bcc) structure. The appearance of this new phase seems to be related to the organization of the nanocrystals and the preferred crystallographic direction in the assembly. DONALD J. KOURI, E-0608, University of Houston. FUNDAMENTAL THEORY OF INVERTING SCATTERING DATA: CHEMICAL INTERACTIONS. We have obtained new results for quantum inverse scattering by barrier potentials, described in a paper submitted to the Journal of Mathematical Physics. We are extending the study to potential well scattering, studying the effects of bound states on the method. In new SUSY-QM research, we have generalized the harmonic oscillator, obtaining uncertainty principles associated with powers of the momentum and position (each being minimized by the ground state of the corresponding generalized oscillator, with uncertainty product 1/2, just like the standard HUP). The exact, analytical eigenstates for each new oscillator have been obtained and provide new, complete orthonormal bases spanning Hilbert space. The new ground states allow construction of generalized "coherent states", which suggest new ideas for semi-classical dynamics, as well as new ideas in quantum optics. The generalized oscillator systems also define new SUSY-matrix "momentum operators" which are used to construct generalized "ladder operators", resulting in much richer spectra than that of the harmonic oscillator. The eigenstates of the generalized momentum constitute the "kernels" of generalizations of the Fourier transform (similar to Fourier analysis, exp(ikx) and the standard momentum operator). Other results include new ways to obtain Fokker-Planck equations (FPEs) describing sub-diffusion and super-diffusion processes (these were postulated some time ago by Procaccia but we also obtain new FPEs that have yet to be studied). All these equations are exactly soluble using our "generalized Fourier transforms. The fundamental breakthrough paper has been accepted and we are writing a number of papers dealing with numerous aspects of our results. We, anticipate that this opens up great numbers of new research avenues which we want to pursue. LÁSZLÓ KÜRTI, I-1764, The University of Texas Southwestern Medical Center. NOVEL METHODS AND REAGENTS FOR C-C AND C-N BOND FORMATION. During the first year after grant renewal we have developed two types of green aminating agents that allow the direct introduction N atom into aromatic systems at low temperature with high chemoselectivity and in the absence of any transition-metal (TM) catalyst. Reagents of the first type are bench stable, sterically hindered NH-oxaziridines that is derived from naturally occurring and inexpensive hindered ketones on the decagram scale. The addition of aromatic Grignard reagents to these oxaziridines at subzero temperatures takes places rapidly and, upon simple (i.e., non-acidic) aqueous workup, afford the corresponding primary arylamines. The mildness of both the addition step and the workup is remarkable and allows the introduction of unprotected primary amino groups (NH2) into even complex and sensitive systems in a clean and straightforward fashion and with good to excellent chemical yield. The use of excess Grignard reagents is not required as the N-H deprotonation pathway is of high-energy (i.e., disfavored), thus the atom economy of the transformation is very good. The presence of oxidatively sensitive functionalities such as olefins, thioethers and dialkylamines is well-tolerated. Aminating agents of the second type are derived from sterically hindered dialkyl keto-malonates. Condensation of keto-malonates with primary arylamines affords N-aryl imino-malonates that feature highly electrophilic N atoms, while the carbon atom of their imino functionality is sterically not accessible for incoming C-nucleophiles. Thus, addition
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of aromatic Grignard reagents at low temperature results in facile N-arylation and, upon aqueous workup in an open flask, unsymmetrical diarylamines are obtained. When dialkyl ketomalonate oximes are O-sulfonated, novel and bench stable doubly electrophilic arninating agents (i.e., linchpins) are obtained. Addition of two equivalents of an aromatic Grignard reagent at low temperature affords symmetrical N,N-diarylamines. JAAN LAANE, A-0396, Texas A&M University. MOLECULAR STRUCTURES AND VIBRATIONAL POTENTIAL ENERGY SURFACES IN GROUND AND EXCITED ELECTRONIC STATES. The investigation of molecular structures and conformations, bonding interactions, and potential energy surfaces in ground and excited electronic states has continued utilizing both experimental and theoretical methods. Infrared and Raman spectroscopy have been used to study the electronic ground states while electronic spectroscopy in the ultraviolet region provides data on electronic excited state structures and vibrations. Ab initio and density functional theory (DFT) calculations complement the experimental work. Further results have been achieved on molecules with intramolecular pi-type hydrogen bonding. Both the infrared and Raman spectra of 2-cyclohexene-1-ol show the presence of six conformations which result from different ring twisting angles and different internal rotation angles. Theoretical computations confirm the magnitudes of the vibrational frequency differences between the different conformers. A potential energy surface has been generated which shows the relative energies of these conformations and the energy barriers between them. The Raman spectra of the two conformations of 1,3-butadiene have been further analyzed using a full quartic potential energy surface in rectilinear coordinates and second order operator Van Vleck perturbation theory. The experimental and theoretical results are in excellent agreement. The internal rotations of methylcyclopropane and seven related molecules have also been investigated and potential energy functions have been determined for each molecule. The theoretical calculations agree very well with results from infrared and Raman spectroscopic data. Studies are also underway on the ring inversion vibration of perfluorcyclopentane and on the intramolecular pi-type hydrogen bonding of 3-cyclopentene-1-amine. KEJI LAI, F-1814, The University of Texas at Austin. ELECTRICAL IMAGING OF CHEMICALLY INTERCALATED NANO-MATERIALS. Thanks to the support from the Welch Foundation, substantial progress has been made by the PI's group in the past grant year, as exemplified by the published and submitted papers below. A key component of the Welch program is to develop the synthesis capability of 2D materials for chemical intercalation. The two chemical-vapor deposition furnaces in the PI's lab are now fully up and running. We have successfully grown MoS2 monolayers and characterized the mesoscopic defects and grain boundaries. The results are published in Nano Letters with online media coverage. Another manuscript describing the synthesis of thin-film In2Se3 samples and their layer-dependent permittivity is currently under preparation. Due to the drastically different intralayer versus interlayer bonding strengths, most physical properties of 2D materials are highly anisotropic between the in-plane and out-of-plane directions, which would inevitably influence the chemical reactions involving these materials. Using the impedance imaging technique, we have shown that the electrical aging of black phosphors is dominated by the lateral diffusion of oxygen and water molecules, which is published in Scientific Reports. Secondly, by combining Raman microscopy, impedance imaging, and time-of-flight secondary-ion-mass spectroscopy, we discovered that the thermal oxidation of WSe2 nano-sheets starts from the edges and propagates laterally towards the center. The manuscript based on this result is now accepted in Nano Letters. Finally, by controlling the reaction time, we have obtained results to spatially resolve the intercalation process of Li ions into MoS2 flakes and the associated insulator-metal transition. A manuscript is in preparation to report this finding. Our results suggest that the edge-initiated chemical reaction is a common theme in 2D materials. DAVID L. LAMBERT, F-0634, The University of Texas at Austin. THE CHEMICAL COMPOSITION OF STARS. Atomic and molecular absorption lines in stellar spectra were analyzed to determine elemental and isotopic concentrations in stellar atmospheres and interstellar clouds to test theories about the production and destruction of nuclides by stars, the evolution of stars, and the formation of the galaxy. Pursuit of the chemical evolution of the Galaxy has continued with detailed analysis of the compositions of red giants in a large sample of open clusters. This sample supplemented by reanalysis of results in the literature provides a new determination of the variation of composition with distance from the center of the Galaxy. Examination of cluster-to-cluster differences in composition shows that clusters of the same concentration of iron-group elements have differing concentrations of heavy elements from barium to europium. This new discovery is attributed to differing levels of contamination of a cluster's natal cloud by ejecta from highly-evolved red giants. A similar range in heavy element concentrations is found among field stars, as expected because open clusters dissolve over time and their stars merge with the field star population. ALAN M. LAMBOWITZ, F-1607, The University of Texas at Austin. THERMOTARGETRON SYSTEM FOR GENOME ENGINEERING OF THERMOPHILES. (1) We are completing genetic analysis and determination of DNA targeting rules for thermotargetrons derived from the Tel3c/4c and Gsl-IIC mobile group II introns. (2) Increasing effort has focused on the thermostable group II intron reverse transcriptases (TGIRTs) encoded by the thermophilic mobile group II introns and their use in next-generation RNA sequencing (RNA-seq). In work published this year (Qin et al. 2016; and Nottingham et al., 2016), we developed a new method for using TGIRTs for RNA-seq and demonstrated its utility for the analysis of cell-free RNAs in human plasma and whole-cell transcriptome profiling, with many advantages over current methods documented in the publications. This new method exploits a novel template-switching activity of the TGIRT enzymes that enables attachment of RNA-seq adaptors to target RNAs without using RNA-ligase, thereby enabling construction of
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comprehensive RNA-seq libraries from very small amounts of starting material. This method has potentially wide applications in basic research and RNA-based diagnostics of human diseases. (3) Expanding our work on group II intron reverse transcriptases (RTs), we have begun to examine related RTs associated with bacterial CRISPR systems. In work done in collaboration with Dr. Andrew Fire's lab at Stanford and published in the journal Science (Silas et al. 2016), we found that certain CRISPR systems encode a novel reverse transcriptase-Cas1 fusion protein that incorporates RNA sequences into genomic CRISPR arrays, where they can then be used for subsequent targeting and destruction of invading RNA viruses or abundant transcripts encoded by DNA pathogens. In addition to it's biological significance, this work demonstrated a novel biochemical mechanism for incorporating RNA sequences into DNA genomes. CHRISTY F. LANDES, F-1787, Rice University. EXPLOITING MOLECULAR FLUORESCENCE TO PROBE LOCAL CHEMICAL DYNAMICS. We are very happy with significant progress in two directions over the past year of Welch support. The first direction is in algorithm development for understanding dynamics in single biomolecules at interfaces. The second direction is in the application of our advanced algorithms to quantify interfacial processes such as adsorption/desorption, hopping, hindered transport, and folding, all of which occur below the optical diffraction limit. Nanoscale porosity underpins a wide range of materials applications. These applications include modern lithium ion batteries, catalytic supports, and chemical and biological separations. Understanding the mechanistic details of how nanoscale porosity controls macroscale processes is very difficult because imaging nanoscale porous structure generally requires freeze drying and electron micrography. Such analysis hides what is likely to be complex surface chemistry and prevents measuring dynamic interfacial processes. This past year our highest impact work involved a broad collaboration to develop a new method called fcsSOFI (for Fluorescence Correlation Spectroscopy Super-Resolution Optical Fluctuation Imaging), which for the first time allows simultaneous in situ optical imaging of nanoscale porous interfaces and quantification of hindered diffusion of analyte molecules trapped within the pores (ACS Nano, 2015, 9, 9158-9166). A recently accepted manuscript expands our super-resolution imaging capacity to 3D, which we expect to provide exciting new insight within the next year's effort (Scientific Reports, 2016, in press). Biopolymer structure and dynamics at nanoscale interfaces is related to drug delivery but also disease inception. Another exciting result in the previous year involves the intriguing new demonstration that serum albumin, the most abundant protein in blood, has concentration-dependent conformational integrity when it binds to gold nanoparticle surfaces (ACS Nano, 2016, 10, 2103-2112). This collaborative project offers a new research direction for our lab, in which we are starting to probe the competition between thermodynamics and kinetics in protein-nanoparticle surface interactions and the resulting fate of both nanoparticles and proteins. Another study that benefitted from our algorithm development was work in which we identified conformational transitions hidden in a neurotransmitter receptor protein (Biophysical Journal, 2015, 109, 66-75). We expect such studies to mature in the next year's support. OLEG V. LARIONOV, AX-1788, The University of Texas at San Antonio. NEW CATALYTIC STRATEGIES FOR THE SYNTHESIS OF COMPLEX HETEROCYCLES. In this year we have focused on the development of novel reactions of nitroxy compounds and the discovery of new synthetic scope and synthetic utility of these compounds. We have investigated the reactions of heterocyclic N-oxides with strong bases, and discovered the highly C2-regioselective deoxygenative dimerization of heterocyclic N-oxides mediated by potassium tert-butoxide. In a departure from previous methods, the reaction proceeds in the absence of heavy metals. We have investigated the mechanism of the reaction and identified the N-oxide-based radical species as key intermediates in the reaction pathway. Following up on this new type of reactivity we have investigated the reaction of nitrogenous heterocycles with Grignard reagents and discovered a simple and transition metal-free method of dimerizing methylenation of N-heterocycles catalyzed by organic bases. The reaction is highly C2-regioselective and does not require expensive and toxic heavy metals and ligands. The mechanism of the reaction was investigated and crucial role of magnesium hydride species in the formation of the products was determined. In addition, we have investigated the copper-catalyzed inverse electron demand [4+2] cycloaddition of transient nitrosoalkenes and indoles and discovered the antileishmanial activity of some of the products of the reaction. The structure-activity relationship of the 1,2-oxazines was further investigated, and the key role of the 1,2-oxazine moiety was discovered. Further, we have developed a simple and efficient method of synthesis of aromatic boronic acids and esters that we required for our investigation of the reactions of heterocyclic N-oxides with various carbon-centered nucleophiles. We have found that aromatic boronic acids and esters can be readily formed from haloarenes (fluorides, chlorides, bromides and iodides), as well as quaternary ammonium salts in a photochemical reaction with diboron compounds. The reaction can be reliably performed on a gram scale in the absence of metals and additives and without deoxygenation of the reaction mixtures. The mechanism of the reaction was investigated and involvement of radical aryl species as well as triplet radical cations was established. Furthermore, the reaction was extended on C‒H/C‒X dual borylation of haloarenes. The mechanism of the reaction also involves aryl radical and triplet aryl species. All in all, the year has resulted in a highly productive expansion of our discoveries in the area of heterocyclic chemistry, and we are looking forward to accomplishing our research goals in the next year. MICHAEL LATHAM, D-1876, Texas Tech University. METHYL-BASED NMR INVESTIGATION OF A DNA DOUBLE STRAND BREAK REPAIR COMPLEX. The proposal for this grant outlined the following for 2015 ‒ 2018: 1) identification of a suitable model system for structural studies; 2) methyl group side chain NMR resonance assignments; 3) identification of a model DNA substrate; 4) determination of the solution state structure of the ATP-bound Mre11-Rad50-DNA complex; and 5) validation of this structure. To these ends, we have made impressive strides in our research plans. Firstly, we are now producing high quality highly deuterated, isoleucine(δ1), leucine(δ), valine(γ), and methionine( ε) 13CH3-labeled (ILVM-
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labeled) Rad50 and Mre11 from the thermophilic archaea Pyrococcus furiosus. Since Rad50 makes the majority of the contact with DNA in the ATP-bound MR-DNA complex, our efforts began there. As a result, ~85% of the ILVM-labeled methyl groups have been assigned for monomeric Rad50. Initial experiments suggest that the transfer of these Rad50 assignments to the ATP-free MR complex will be straightforward, and analogous experiments to transfer the methyl group assignments to ATP-bound dimeric Rad50 revealed an allosteric pathway coupling ATP-binding to distal sites within Rad50. Interestingly, and as a result of this Welch support, initial NMR data collected on a Rad50 mutation observed in a cancer patient may suggest a functional role for this allosteric pathway: a new line of research has begun to characterize the importance of this allostery, shed more light on the ATP-binding and -hydrolysis functions of Rad50, and reveal the carcinogenic nature of this mutation. We are also making strides in ILVM-labeled methyl group assignments for Mre11. These NMR data will be coupled with enzyme activity assays, which we are also adapting to our laboratory. In the past year, Welch Foundation support has been critical to the start-up of our laboratory and has allowed us to collect data that should be submitted for publication within the next year. SEONGMIN LEE, F-1741, The University of Texas at Austin. CHEMICAL, BIOCHEMICAL AND STRUCTURAL STUDIES OF INFLAMMATION-INDUCED DNA LESIONS.
Our study led to a synthesis of 8-oxoA-containing DNA. The 8-oxoA phosphoramidite was prepared in 6 synthetic steps from 2'-deoxyadenosine (Figure 1). Using the 8-oxoA-containing DNA, we determined crystal structure of human DNA polymerase beta in complex with 8-oxoA:dGTP (Figure 2). In the 2016-2017 grant period, we will prepare 2-oxoA and 8-CIG 2'-deoxy nucleoside, convert them into their corresponding phosphoramidites, and site-specifically incorporate the phosphoramidites into DNA via solid phase DNA synthesis (Figure 1). The resulting DNA will be purified by urea polyacrylamide gel electrophoresis and analyzed by MALDI-TOF mass spectrometry
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T. RANDALL LEE, E-1320, University of Houston. ALIPHATIC XANTHATES, AND ANALOGS FOR TAILORED SURFACES AND NANOPARTICLE COATINGS. We continued our efforts to generate CF3-terminated alkyl xanthates and dithiocarboxylic acids for the purpose of studying the effects of surface dipoles on wettability. Due to the extreme (and unexpected) base-sensitivity of these molecules, we were unable, despite several attempts the use of multiple strategies, to generate films with sufficient integrity to afford reproducible data, forcing us to seek alternative molecular precursors for preparing these dipole-terminated of films. In complementary work, we demonstrated the first example of fluorinated surfaces having inverted surfaces dipoles (Zenasni et al. Chem. Mater. 2015), and we summarized our long-term efforts to demonstrate the influence of surface dipoles on wettability (Lee et al. Acc. Chem. Res. 2015). We also described two innovative strategies for generating homogeneously mixed heterogeneous thin films that cannot undergo phase separation, leading to unprecedented chemically distinct interfaces (Chinwangso et al. Langmuir 2015 and Lee et al. Chem. Mater. 2016). Studies of custom-designed phenyl-based bidentate adsorbates led to the development of bionsensors (Radhakrishnan et al. J. Electrochem. Soc. 2016), robust tools for bioconjugation (Park et al. Langmuir 2016), and to the efficient growth of polymer films from surfaces (Park et al. ACS Appl. Mater. Interfaces 2016 and Lee et al. ACS Appl. Mater. Interfaces 2016). The synthesis of a new zwitterionic surface adsorbate led to the development of new antifouling surfaces (Huang et al. ACS Appl. Mater. Interfaces 2015) and to biocompatible plasmonic nanoshells for hyperthermia (Huang et al. Coll. Surf. B 2016). Separate efforts to use plasmonic nanoshells (Bryan et al. RSC Adv. 2016) to enhance the photocatalytic conversion of water to hydrogen were successful (Li et al. ACS Appl. Mater. Interfaces 2016), as were separate studies utilizing magnetic nanoparticles for biosensing (Chen et al. ACS Cent. Sci. 2016) and imaging (Rittikulsittichai et al. Nanoscale 2016). XIANGYANG LEI, V-1815, Lamar University. NEW NICKEL(II) σ-ARYL COMPLEXES AS CATALYSTS FOR SUZUKI CROSS-COUPLING REACTIONS. Nitrogen-based ligands are generally more air-stable and less toxic than phosphine-based ligands. It has been reported that metal complexes with a pincer ligand show high catalytic activity due to the rigid geometry imposed by the pincer ligand. In the grant year of 2015-2016 we synthesized several nitrogen-based pincer ligands (1) and investigated their application as ligands in nickel-catalyzed Suzuki cross-coupling reactions. The results show that these ligands are more efficient than 1,10-phenanthroline (2) and 2,2'-bipyridine (3), both of which are commonly used nitrogen-based ligands, as ligands in Suzuki cross-coupling reactions under the same reaction conditions. The new catalytic system works for both aryl iodides and aryl bromides as substrates. Under the optimal reaction conditions, the coupling reactions can be completed in a short time (less than 2 hours) in open air to give the coupling products in moderate to high yields. It is proposed that in the catalytic system new nickel(II) complexes (4) that involve N-heterocyclic carbenes and have a CNC motif are formed as the catalytically active species. The manuscript based on this research is in the final stage of preparation for publication. During this past grant year, the grant supported one postdoctoral fellow (Dr. Zhifo Guo), one graduate student (Manish Dnyaneshwa Basviskar), and four undergraduate students (Kenny Huynh, Jimmy Huynh, Jamie Stafford, and Kimanh Tsan).
BING LI, I-1713, The University of Texas Southwestern Medical Center. MECHANISMS FOR HISTONE H3 LYSINE-TO-METHIONINE MEDIATED CHROMATIN MIS-REGULATION. Recurrent lysine-to-methionine mutations (K-M) of histone H3.3 variants have been detected in several tumors and were speculated to be major driver mutations for tumorigenesis. These mutations inhibit enzymatic activities of the corresponding histone methyltransferases (HMTs) in vitro and reduce the global levels of methylation at the same residues in vivo. Since human histone H3 is encoded by a cluster of 13-15 histone genes, it was unclear how mutations on one histone gene could lead to catastrophic effects on the entire genome. Based on the results using histone peptides which do not reflect physiological condition, it was postulated that K-M mutants may trap HMTs to local regions and reduce the overall availability of HMTs. During the past grant period, using the unique chromatin reconstitution system that we have developed, we showed that in two cases, HMTs do not show higher affinity toward K-M mutated nucleosomes than wild type nucleosomes (yeast Set2-K36M and drosophila PRC2 complex-K27M). This result argues against the "trapping' model. We are currently setting up the designer nucleosome arrays to test if K-M nucleosomes will inhibit HMTs methylating adjacent nucleosomes. To dissect the K-M mediated HMT inhibition in vivo in Aim 2, we found that ectopically expressing histone K-M mutants at the level that was 30 fold lower than the endogenous histone H3 abolished the bulk levels of histone H3K36 trimethylation (K36me3) in yeast. We performed Ch1P-seq experiments to determine the distribution pattern of K-M mutants, and our preliminary analysis suggests that K-M mutated histones do not show uniform distribution pattern cross the genome. Interestingly, at many less-active genes, K36me3 is markedly reduced where there is no detectable K-M mutant at the region, suggesting that H-M either
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function as a "poisoner" at free histone levels, as we originally hypothesized based on our biochemical experiments, or K-M can inhibit Set2-mediated K36me3 in distance. We will follow our original plan aiming to distinguish these two not mutually exclusive models. GUIGEN LI, D-1361, Texas Tech University. GROUP-ASSISTED PURIFICATION (GAP) CHEMISTRY FOR ASYMMETRIC SYNTHESIS AND CATALYSIS. Aza-Morita-Baylis-Hillman adducts were synthesized by reacting chiral N-phosphonyl imines with acrylonitrile and acrylates excellent yields and diastereoselectivity. The synthesis followed GAP (group-assisted purification) chemistry/technology, in which pure chiral aza-MBH products can be readily obtained by washing the crude products with co-solvents of hexane and ethyl acetate. The Mannich reaction between chiral N-phosphonyl imines and a Ni(II)-complexed alanine Schiff base has been developed, in which single isomers of α-methyl-α,β-diamino acids containing chiral quaternary carbon centers were obtained via GAP chemistry. A novel catalytic domino spirocyclization of 1,7-enynes with simple cycloalkanes and cyclo-1,3-dicarbonyls has been discovered via multiple C-C bond formations from alkynyl/alkenyl functions and dual α,α-C(sp3)-H abstraction/insertion. The reaction involves addition, 6-exo-dig cyclization and radical coupling sequences under convenient catalytic conditions, and provides a concise access to Spiro cyclopenta[c]quinolones. The cobalt-catalyzed direct methylation of a C(sp2)‒H bond using dicumyl peroxide (DCP) as both the methylating reagent and hydrogen acceptor was studied. The reaction proceeded smoothly without using any additives, and was proven to be applicable to various amides bearing a 2-pyridinylisopropyl (PIP) directing group, providing an efficient access to o-methyl aryl amides with high functional-group tolerance. PINGWEI LI, A-1816, Texas A&M University. THE STRUCTURAL BASIS OF MICROBIAL DNA SENSING IN INNATE IMMUNITY. Our recent work focuses on dissecting the signaling mechanism of the cGAS-STING pathway. We have determined the crystal structure of a phosphorylated STING C-terminal peptide bound to the transcription factor IRF-3. This structure reveals the mechanism of IRF-3 recruitment by STING upon phosphorylation. We have generated a phosphomimetic mutant 5386/396E of IRF-3 and determined its structure in complex with a fragment of the CREB-binding protein (CBP). This structure provides critical insights into the mechanism of IRF-3 activation upon phosphorylation. Recently, we have made some progress towards determining the structure of phosphorylated IRF-3 in complex with CBP. We have obtained crystals of phosphorylated mouse and human IRF-3 bound to CBP. Structural analyses of these complexes are in progress. To understand how STING recruits the protein kinase TBK1 to the signaling complex, we have conducted mutagenesis and surface plasmon resonance (SPR) binding studies of STING and identified the structural motif of STING involved in TBK1 binding. Structural analysis of the STING-TBK1 complex is in progress. In collaboration with Dr. Xiangshi Tan from Fudan University in China, we have conducted antitumor studies of the cyclic dinucleotide cGAMP synthesized in my lab. We observed potent antitumor activity of cGAMP in mice model. In summary, during the last three years, we have determined the structures of cGAS and its complex with dsDNA, the structure of phosphorylated STING bound to IRF-3 and IRF-3/CBP complex. These structural studies provide critical insight into the mechanism of cytosolic DNA sensing through the cGAS-STING pathway. WEI LI, C-1845, Rice University. NUCLEAR CHEMISTRY AT TRILLION DEGREES. The Rice heavy-ion physics group continues the study of particle correlations and collective phenomena for a strongly interacting, fluid-like nuclear matter created in pp, pPb and PbPb collisions with the CMS experiment at the LHC. Over the past year, our group's activities have been focusing on understanding the chemical composition of particle production and correlations in the newly recorded pp and pPb data at a much higher energy, and also participating in the operation of CMS detector to take high-quality data. The PI, Li, continues playing a leadership role in the CMS collaboration at CERN as the convener of CMS heavy-ion group, consisting of about 200 scientists. Under Li's leadership, the group has accomplished a very successful data taking in 2015. A new Level-1 trigger system mainly developed and commissioned by graduate student, Michael Northup, has been in smooth operation throughout the year. The high-quality data recorded resulted in 66 published/submitted papers. Rice group members have led a number of high impact publications. Graduate student, Zhoudunming (Kong) Tu, performed detailed studies of the chemical composition of particle pi- spectra in pp, pPb and PbPb collisions for various event multiplicities. Tu's analysis revealed a common pattern of collective flow in all three systems with different sizes and energy density. Tu also proposed a novel idea of investigating the Chiral Magnetic Effect using identified particles in pPb collisions for the first time. Graduate student, Zhenyu Chen, developed a new correlation analysis, taking advantage of the wide acceptance coverage of the CMS detector. Chen studied polar angle dependence of long-range correlation phenomena in pPb and observed an asymmetry between p- and Pb-going sides. This new finding further supports the hydrodynamic origin of observed correlations. Rice group presented two oral talks and one poster in the Quark Matter 2015 conference, Japan, in September 2015. XIAOQIN (ELAINE) LI, F-1662, The University of Texas at Austin. SURFACE PLASMON ENHANCED SPECTROSCOPIC RULERS. We aim to apply a powerful spectroscopic method, surface plasmon enhanced spectroscopy to study properties of metallic and semiconductor nanostructures. These nanostructures can be considered as artificial molecules that consist of coupled semiconductor and metallic nanostructures which can be fabricated, assembled, and engineered on nanometer scales with precisely tailored properties. By studying these well-controlled model systems, one can learn how to interpret spectra obtained from more complicated nano-systems, bio-molecules, etc. In this grant year, we have published seven articles including one in Nature Physics, two in Nature Communication, one in PNAS, one in Nano Letters, and two in ACS Photonics. We reported experimental demonstration of a new type of plasmonic sensor consisting of a single metallic nanoparticle and a single semiconductor quantum dot. A quantum two-level system, i.e., the excitors resonance in a single semiconductor quantum dot interferes with a classical system, i.e., the plasmonic resonance in a gold nanoparticle, leading to a Fano resonance mediated by single photon scattering event. This result is highly counterintuitive because the scattering cross sections of the two nanoparticles
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differ by four orders of magnitude. Our work represents a critical step toward realizing quantum plasmonic nanostructures that are capable of producing scattered light, which dependig on its polarization state, obeys either quantum or classical statistics. Furthermore, our work enables a hybrid orientation sensor unaffected by photobleaching of quantum dots. A major research direction of our funded projects by the Welch Foundation in the next two to three years is to perform quantum statistical measurements and explore sensing and imaging in the quantum regime. ROGER L. LICHTI, D-1321, Texas Tech University. MUONIUM DEFECT CHEMISTRY IN FUNCTIONAL OXIDES. In continuing work on transparent conducting oxides, we implemented an analysis of trap-limited diffusion of Mu using a two-state trap and release model for cases where MuSR signals from a freely diffusing Mu+ ion could not be easily separated from the signal due to a trapped state, i.e. a Mu-Defect pair. This allows us to obtain the hop barrier related to diffusion as well as to determine the trapping and dissociation rates as a function of temperature. Initial results applying this model to In2O3 indicate a harrier of 0.75 eV for Mu site to site hops and an energy of 1.1 eV associated with release from the trap. In most TCO materials H/Mu forms an (OH)¯ radical and acts as a shallow effective mass donor which contributes to the naturally occurring n-type conductivity. However, in TiO2 we find that for the neutral Mu center, the electron resides on a nearby Ti ion reducing it from Ti4+ to Ti3+, confirming that Mu and H form identical localized states rather than a shallow donor. We characterized the mix of Mu ground state and first exited state sites which effects the Mu results compared to those for H (from EPR/ENDOR data) at the same temperature. The larger amplitude of Mu vibrations with respect to H slightly modifies the Mu hyperfine interaction from what is expected based on H results scaled for the magnetic moment ratio of the muon and proton. In undoped VO2 we observe an internal magnetic field below 35 K as sensed by the muon; however, this has a relatively short correlation length which suggests the an H/Mu impurity breaks up the V-V dimerization leading to local V4+ moments in its immediate vicinity. With a few atomic percent doping by Ti or W at the V-site this magnetic phase extends to 160 K with much longer correlation lengths and well determined local fields at the muon site. PAUL A. LINDAHL, A-1170, Texas A&M University. CHEMICAL CHARACTERIZATION OF LOW-MOLECULAR-MASS COMPLEXES IN MITOCHONDIRA AND BLOOD. We published three studies sponsored by the Welch Foundation this year. In the first, we reported that mitochondria contain approximately two dozen labile LMM metal complexes. We characterized these complexes in terms of molecular mass and concentration in the organelle. We employed a novel liquid chromatography system located in a refrigerated anaerobic glove box and interfaced to an inductively coupled plasma mass spectrometer (LC-ICP-MS). We prepared extracts of isolated mitochondria from yeast and human cells, and from mouse brain and liver. Extracts were passed through a 10 kDa cutoff membrane. Flow-through solutions were injected onto calibrated size-exclusion columns. Yeast mitochondria contain two major Fe species called Fe580 and Fe1100 (numbers refer to mass in Daltons), the collective concentration of which is ca. 100 µM. These LMM species are probably used as feedstock for heme and/or iron-sulfur-cluster biosynthesis. The two LMM species are interrelated, as Fe1100 converts into Fe580 after a five day incubation. Fe580 dominates in exponentially growing cells while Fe1100 dominates in post-exponential cells. Mammalian mitochondria contain the same species as well as a third species (Fe2000). Yeast mitochondria contain a single Mn species (Mn1100) at a concentration of ca. 2 µM. Mammalian mitochondria contain Mn1100 and a second species (Mn2000). Mn1100 might be used to install Mn into mitochondrial superoxide dismutase 2 while Mn2000 may be used to metallate apo-arginase in mammalian cells. LMM complexes of other metals were also detected, including a Cu species with a mass of ca. 5000 Da (16 µM in yeast mitos) and a Zn species with a mass of 1200 Da (110 µM). Cu5000 and Zn1200 are also probably involved in metallation of mitochondrial apo-proteins. LMM Co, Mo, P, and S species were also detected. This was the first study to systematically catalog labile LMM metal complexes in mitochondria, and it will serve as a foundation for probing the function of these species. In another Welch-sponsored study, we determined the kinetics of nutrient Fe import into major mouse organs including liver, brain, heart, kidney and spleen. We invented a novel method called "pup swapping" in which newborn mice from females enriched in one isotope of Fe (56Fe or 57Fe) were swapped with newborns from females enriched in the other isotope. Each week, the concentrations of each isotope were determined in organs and blood plasma. A mathematical model was developed to understand and interpret the results. We discovered that LMM non-transferrin-bound Fe, rather than transferrin, dominated the process of iron transfer from blood into organs. This improves our understanding of how nutrient Fe is absorbed and imported into mammalian organs, and it has implications for Fe-overload diseases. Finally, we investigated the Fe content of livers isolated from mice, ranging from newborn to elderly, using Mössbauer spectroscopy and other related spectroscopic methods. ICP-MS was used to quantify the Fe concentration in these tissues. We discovered that ferritin Fe in newborn livers is exported during the first few weeks of life. This Fe is passed into other organs. Although Mössbauer spectroscopy has been used previously to examine liver, this is the first report of spectral features from Fe/S clusters, heme centers, and nonheme high-spin Fe(II) centers in that organ. Major differences were observed in livers from Fe-deficient mice and from genetically altered and diseased mice. We are the only group world-wide to analyze mammalian organs using these advanced chemical and biophysical methods. STEPHAN LINK, C-1664, Rice University. CHEMISTRY MEETS SURFACE PLASMONS. We investigated the electron relaxation in single gold nanodisks after excitation with an ultrafast laser. Transfer of the excitation energy from the electrons to the phonons launches an acoustic breathing mode with its frequency governed by the adhesion strength of the nanodisk to the underlying substrate, as determined through thickness variations of a titanium adhesion layer. By examining single nanodisks we were also able to quantify the intrinsic damping time of the acoustic oscillations and found it to vary greatly among the nanodisks likely due to the heterogeneous nature of the glass-Ti-Au interface. As the ultrafast relaxation dynamics in plasmonic nanoparticles strongly depend on the initial degree of excitation, which is a function of laser power and absorption cross section, we developed a single-particle absorption spectrometer capable of measuring an absorption spectrum over a broad wavelength range of 500-1000 nm. Our setup is based on photothermal imaging where pure absorption is detected via heat generation after photoexcitation. Measuring absorption spectra
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only free from scattering is non-trivial, and revealed important differences between the absorption and scattering of single gold nanospheres and nanorods. Another approach to examine the energy relaxation of plasmonic nanostructures is to measure their photoluminescence, a process that is still only poorly understood. We fabricated gold nanosphere dimers and compared their quantum yield to individual nanospheres. We found that their quantum yields were the same despite the much larger electric field generated by the dimers, suggesting that the local electric field plays a minor rule. Finally, we implemented for the first time circular dichroism (CD) spectroscopy on a dark-field microscope and investigated the scattering CD spectra of novel, self-assembled nanostructures free from ensemble averaging, especially important for samples that contain both chiral enantiomers. JEN LIOU, I-1789, The University of Texas Southwestern Medical Center. NOVEL IMAGING PROBES FOR INVESTIGATING ER-PLASMA MEMBRANE JUNCTIONS. A). We have generated several new versions of probes to optimize the labeling of MCSs between the ER and endosomes/lysosomes. The best probe was identified. B.) We have confirmed that this probe can selectively label ER-endosome/lysosome MCSs. The validation was achieved by generating a fusion protein of the MCS probe with APEX2 and imaging APEX2-tagged ER-endosome/lysosome MCS probe-transfected cells using electron microscopy. APEX2 signals were observed specifically at the contact sites between the ER and endosomes or lysosomes in these cells. C.) We have determined that expression of the ER-endosome/lysosome MCS probe does not affect the association degree of either RAB5+ early endosomes or RAB7+ late endosomes/lysosomes to the ER in the human osteosarcoma U2OS cell line using fluorescence confocal microscopy. D.) We have further examined the co-localization of our MCS probe with NPC1, a lysosomal membrane protein important for cholesterol egression from lysosomes. We found that our MCS probe marks almost every single NPC1+ lysosome in CHO7 cells. HUNG-WEN LIU, F-1511, The University of Texas at Austin. MECHANISTIC STUDIES OF NOVEL ENZYMES. To study the biosynthesis of formycin, the genome of S. kaniharaensis was sequenced, and two sets of purA, purB, purC, and purH genes were identified. The Pur enzymes are known to catalyze construction of the pyrimidine ring in the imidazolopyrimidine moiety of purine nucleobases. Considering the close structural resemblance of formycin A to adenosine, proteins encoded by the second set of pur genes (forD, forR, forV and forC) may catalyze analogous transformations during assembly of the pyrazolo-pyrimidine unit in the biosynthesis of formycin A. To test this hypothesis, the putative intermediate in the pathway, formycin B 5'-phosphate, was synthesized and shown to be converted by ForD and ForR in the presence of L-aspartate to formycin A 5'-phosphate, which upon treatment with alkaline phosphatase led to formycin A. These results are consistent with the assigned functions of the Pur-like enzymes in S. kaniharaensis. Sequence analysis also implied an overall pathway for the formation of formycin A. This study highlights that biosynthetic pathways of secondary metabolites may evolve directly from those in primary metabolism. In collaboration with Prof. Jessie Zhang at UT Molecular Biosciences, the structure of ForC has recently been solved. Progress in studying the biosynthesis of nogalamycin has been slow due to challenges encountered in our chemical synthesis of the nogalamycin aglycone. An entirely new synthetic route that employs milder deprotection procedures is currently in development in an effort to surmount this difficulty. JUN LIU, AU-1714, The University of Texas Health Science Center at Houston. HIGH-RESOLUTION STRUCTURE DETERMINATION OF MOLECULAR MACHINES IN SITU BY CRYO ELECTRON TOMOGRAPHY. We significantly improve resolution and throughput of our cryo-electron tomography pipeline by implementing innovative methods and automation. This system has been effectively utilized to study one of the most complex molecular machines in bacterial pathogens: type Ill protein secretion machine. The type Ill secretion machine has specifically evolved to deliver multiple bacterially encoded proteins into target eukaryotic cells. We determine the high-resolution in situ structure of the entire machine and reveal the core elements: the bacterial envelope-associated needle complex, the inner membrane export apparatus, and the cytoplasmic sorting platform. Through molecular modeling and comparative analysis of the machines assembled with protein-tagged components or from different mutants we obtain a detailed molecular architecture for the first time. Furthermore, our structures provide direct evidence that the cytoplasmic sorting platform undergoes significant conformational changes required for a novel symmetry adaptation and the assembly of the entire secretion machine. Together, our studies provide major insight into the structure and assembly of the secretion machine and may provide the bases for the development of novel therapeutic strategies against several important bacterial pathogens. QINGHUA LIU, I-1608, The University of Texas Southwestern Medical Center. MECHANISTIC STUDIES OF THE DROSOPHILA RNA INTERFERENCE PATHWAY. Recent studies suggest that the Microprocessor (Drosha-DGCR8) complex can be recruited to chromatin to catalyze co-transcriptional processing of primary microRNAs (pri-miRNAs) in mammalian cells. However, the molecular mechanism of co-transcriptional miRNA processing is poorly understood. Here, we find that HP1BP3, a histone H1 -like chromatin protein, specifically associates with the Microprocessor and promotes global miRNA biogenesis in HeLa cells. Accordingly, chromatin immunoprecipitation (ChIP) studies reveal genome-wide co-localization of HP1BP3 & Drosha and HP1BP3-dependent Drosha binding to actively transcribed miRNA loci. Moreover, HP1BP3 exhibits a novel pri-miRNA binding activity and promotes the Drosha-pri-miRNA association in vivo. Knockdown of HP1BP3 compromised pri-miRNA processing by resulting in the premature release of pri-miRNA transcripts from the chromatin. Taken together, these studies suggest that HP promotes co-transcriptional miRNA processing via chromatin retention of nascent pri-miRNA
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transcripts. The work expands the functional repertoire of the H1 family of proteins and suggests a new concept of chromatin retention factor for widespread co-transcriptional miRNA processing. WENSHE LIU, A-1715, Texas A&M University. BIOSENSORS FOR SMALL MOLECULES AND ENZYMES. Previously we showed that ubiquitin activating enzyme El can directly catalyze the amidation reaction of the ubiquitin C-terminal carboxylate. Primary amines can be directly and covalently linked to ubiquitin for its functionalization. We have expanded this discovery to append ubiquitin with a C-terminal D-cysteine to afford Ub-D-Cys. We have demonstrated that Ub-D-Cys can serve as a substrate for several deubiquitinases to undergo hydrolysis and the released D-Cys can react with 2-cyano-6-hydrobenzothiazole to afford D-luciferin that can be chemiluminescently detected with the use of the firefly luciferase. This forms a new concept for the deubiquitinase activity detection and can be applied for the high throughput screening of deubiquitinase inhibitors. A manuscript describing this progress is under preparation. In order to synthesize triubiquitins with versatile isopeptide linkages, we have formulated a synthetic route that contains two consecutive photoclick reactions and streamlined the procedure. Now we are in the process to generate 64 triubiquitin variants that contain all possible isopeptide bond combinations. Meanwhile we have developed other strategies that based on the genetic noncanonical amino acid incorporation approach for the synthesis of diubiquitins. Azidonorleucine, an noncanonical amino acid with a side chain azide for its potential conjugation with a ubiquitin molecule which has a C-terminal phosphinolthioester, has been genetically incorporated into ubiquitin. Now we are in the process of synthesizing the C-terminally phosphinothioester-containing ubiquitin and testing its reaction with ubiquitin incorporated with azidonorleucine for the synthesis of diubiquitin. Alternatively, allysine, a noncanonical amino acid with a side chain aldehyde, has been incorporated into ubiquitin. The side chain aldehyde of allysine allows its potential conjugation with ubiquitin that has a C-terminal hydrazide. Now we are testing this potential reaction for the synthesis of diubiquitins. XIN LIU, I-1790, The University of Texas Southwestern Medical Center. STRUCTURAL BASIS AND CHEMICAL MODULATION OF GENE SILENCING BY POLYCOMB REPRESSIVE COMPLEX 2. Last year, we determined the crystal structure of an active polycomb repressive complex 2 (PRC2) from Chaetomium Thermophilum in both basal and H3K27me3-stimulated states. This active PRC2 contains Ezh2, Eed, and the VEFS domain of Suz12 (Suz12(VEFS)) and its molecular weight is about 170KDa. The structure of the stimulated PRC2 contains a stimulating H3K27me3 peptide. Eed is engulfed by a belt-like structure of Ezh2, and Suz12(VEFS) contacts both of these two subunits to confer an unusual split active SET domain for catalysis. Comparison of PRC2 in the basal and stimulated states reveals a mobile Ezh2 motif that responds to stimulation to allosterically regulate the active site. This work was published on Science in October 2015. In addition, we examined surface conservation and electrostatic potential distribution of this active fungal PRC2 to provide additional insights into functional similarity and divergence between the fungal and human PRC2 and for PRC2 binding by nucleic acids. Further structure comparison indicated a conformational change of the catalytic SET domain within PRC2 during transition from the inactive to active state. Such a conserved structural mechanism is also used by another histone methyltransferase family, COMPASS, associated with gene activation for enzyme regulation. This detailed structural analysis and comparison was published on Nucleus in May 2016. Moreover, we recently found by X-ray crystallography that PRC2 adopted a stable autoinhibited structural conformation in the absence of the cofactor and histone substrate binding. Disruption of the autoinhibition resulted in a vastly activated PRC2 in the basal state in solution. Both fungal and human PRC2 utilize an overall similar molecular mechanism to maintain the autoinhibited state by impeding interaction of the cofactor and histone substrate with the enzyme active site. We will submit this exciting new finding soon. YI LIU, I-1560, The University of Texas Southwestern Medical Center. BIOCHEMICAL ANALYSIS OF AN RNA INTERFERENCE PATHWAY. A significant portion of eukaryotic small RNAs are produced from repetitive DNA loci in fungi to animals. How small RNAs are specifically produced from repetitive DNA loci is not clear. Quelling is an RNAi-related phenomenon that post-transcriptionally silences repetitive DNA in Neurospora. We previously identified a type of DNA damage-induced small RNA called qiRNAs that originate from the repetitive ribosomal DNA. To understand how small RNAs are generated from repetitive DNA, we previously carried out a genetic screen to identify genes required for qiRNA biogenesis. We discovered that homologous recombination is an essential process for qiRNA production, which allows the repetitive DNA loci to be distinguished from the rest of the genome. In the past year, we showed that DNA tandem repeats and double-stranded breaks are necessary and, when both are present, sufficient for triggering gene silencing and siRNA production. Introduction of a site-specific double-stranded break or DNA fragile site resulted in homologous recombination of repetitive sequences, which is required for gene silencing. In addition to siRNA production, the quelling pathway also maintains tandem repeats by regulating homologous recombination. Our study identified the mechanistic trigger for siRNA production from repetitive DNA and established a role for siRNA in maintaining genome (Yang et al., 2015 Genes & Dev). In addition to our non-coding RNA study, we also carried out several studies concerning mechanisms of circadian rhythms and the role of codon usage in regulating protein translation and protein structures.
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STEVE W. LOCKLESS, A-1742, Texas A&M University. THE STRUCTURAL BASIS FOR LIPID REGULATION OF MEMBRANE PROTEIN FUNCTION. We have published two papers during the past year, and have made significant technical advances that will allow us to dissect the allosteric regulation of K+ channels by lipid molecules. Specifically, we found that the conformation of the intracellular gate of a K+ channel is different in detergent micelles and lipid membranes. Based on structural and biochemical assays, we found that the conformational change within the gate propagates to distant ion binding sites of the channel (2015 PNAS publication). This suggests that lipid molecules are allosteric regulators of ion binding to the channel. To test this hypothesis and determine the physical-chemical principles underlying this regulation, we have recently developed a new biochemical assay to measure ion binding to the K+ channel in the presence of lipid membrane mimics (2016 Anal Chem publication). We will now examine whether the equilibrium preferences for lipids binding to specific sites translate into functional changes in channel activity, which is important to tease apart their role in regulation. During the current grant period, we began developing a new system to study the integration of membrane signals with soluble signaling molecules using E.coli's K+ channel as a model. This channel contains both cytosolic regulatory domains and transmembrane helices that likely regulate the channel. We have expressed and purified this channel and found that adenosine nucleotides regulate its function. Intriguingly, deleting this channel leads to cells growing and swimming in concentrated concentric circles, which is also the phenotype observed when deleting some lipid synthesis genes, suggesting that lipid molecules regulate the channel. Ultimately, we will use this new system to study how the channel integrates information from its cytosolic regulatory domains and the lipid molecules surrounding it, which is not possible with the ion channels used in previous studies. JUN LOU, C-1716, Rice University. DEVELOPMENT OF NANOMATERIALS FOR LOW COST SOLAR ENERGY HARVESTING. In this grant year, we have made very good progress in developing carbon nanomaterials enabled DSCs. The cathode used in most DSCs is fluorine-doped tin oxide glass coated with a Pt film, which is both expensive and brittle and therefore limits the flexibility and large-scale implementation of this promising technology. We showed that flexible, seamlessly covalently bonded, three-dimensional vertically aligned few-walled carbon nanotubes (VAFWCNTs)/graphene on metal foil can act as a novel cathode free from transparent conducting oxide and Pt for application in DSCs. This cathode has a lower charge transfer resistance and lower contact resistance between the catalyst and the substrate than the conventional combination in a brittle Pt/fluorine-doped tin oxide cathode. The covalently bonded graphene and VAFWCNTs ensure excellent electron transport through the electrode and the large surface area of the hybrid carbon materials rivals the catalytic capability of the Pt analogue. DSCs utilizing this flexible VAFWCNTs/graphene hybrid cathode outperformed the Pt-based cells in both rigid (8.2% vs. 6.4%) and flexible (3.9% vs. 3.4%) assemblies. The VAFWCNTs/graphene on metal foil combination is a novel, inexpensive, high-performance, flexible cathode for application in solar cells. In another work, metal grids covered by graphene were used as transparent conductive electrodes in DSCs. Compared to the control group, in which the platinum grids were used as a transparent conductive layer; the efficiency of DSCs with graphene was more than two times better. To our knowledge, it is the most efficient dye sensitized solar cell to use a graphene-based transparent conductive electrode without a conductive oxide support such as fluorine-doped tin oxide or indium-doped tin oxide. The DSCs prepared by 150 °C as the low temperature processes, which are essential for fabricating flexible DSCs, were fabricated using a hybrid graphene on Ni grids transparent conductive electrode. The mechanical properties of the flexible hybrid transparent electrode are better than the oxide-based transparent conductive electrode in both bending and stretching tests. Therefore, the long-term stability of the flexible DSCs could be enhanced by using this new transparent conductive layer. CARL J. LOVELY, Y-1362, The University of Texas at Arlington. TOTAL SYNTHESIS OF SPIROCYCLIC MARINE SPONGE-DERIVED ALKALOIDS
We have made substantial progress in our studies towards spirocalcaridine A (1) and B through the discovery of a reaction that we initially have termed TOADS — tandem oxidative amination-dearomatizing spirocyclization. In the initial variant of this chemistry, phenol 2 was oxidized to serve as the electrophilic trigger, however, this led to the formation of the incorrect ring system 3 for our application and a poor yield. However, reversal of the direction of the chemistry using 5 resulted in formation of a single spirocyclic molecule 4 and a substantial increase in yield. Confirmation of the structure of 4 was secured by X-ray crystallography. It has been found that this chemistry works well with other protected guanidines (CBZ, TEOC) and with ureas 7 (X = 0), although in the latter case oxazoles 8 rather than the corresponding 2-imidazolones are obtained. Preliminary attempts to extend this chemistry to thioureas 7 (X = S) have not yet been successful. Initial attempts to isomerize the olefin or remove the BOC-protecting groups have been compromised by rearrangement of the spirocyclic framework to the corresponding naphthimidazole 6, but we have yet to investigate elaboration of other protected guanidines. In the course of developing approaches to propargyl guanidines via the corresponding cyanamides 10, it was discovered that these undergo electrophile-induced dearomatizing spirocyclization to afford cyclohexadienones 11.
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VASSILIY LUBCHENKO, E-1765, University of Houston. PREDICTING THE STRUCTURE OF COMPLEX INORGANIC SOLIDS. 1. We have developed a novel coarse-grained description of the fundamental chemical interactions, in which the covalent and secondary bond are viewed as symmetry-broken versions of the multi-center bond. The latter, in turn, is shown to be a hybrid of the metallic and ionic interactions. The distinction between the two becomes sharp at sufficiently high densities and can be traced to poor mutual miscibility of localized and delocalized electrons. These findings provide a way to rationalize and predict striped solid phases and other types of ordering on supra-atomic scales, propensity to displacive transitions, and the feasibility of specific stoichiometries. 2. We have discovered a density-driven, electronic localization transition that takes place even at fixed geometry in small molecules and bulk solids alike. Stable, covalently bonded materials can be identified as such even when the exact geometry is not known: Each covalent bond should house a two-center localized molecular orbital. Otherwise, a structural instability is present. This finding provides a foundation for efficient, automated screening of candidate stoichiometries and structures, by eliminating the computationally-costly step of geometric optimization. 3. As part of the effort to develop efficient pseudo-potentials that improve kinetic accessibility of the crystal state, we have made progress in implementing high-order interactions in molecular simulations. We have discovered a novel phase transition: A crystal will melt, if the stiffness of the bond, as opposed to the bond strength, is decreased below a certain threshold value. 4. We have developed a novel algorithm for generating high-density amorphous structures that exhibit directional bonding. We have established the origin of the puzzling first sharp diffraction peak in amorphous chalcogenides. 5. We have established that the size of mesoscopic clusters in solutions of complex molecules is independent of the ionic strength, which suggests complicated conformational dynamics of the molecules. ROBERT R. LUCCHESE, A-1020, Texas A&M University. REACTION DYNAMICS PROBED BY MOLECULAR-FRAME PHOTOIONIZATION. In our study of the photoionization of a sequence of alkyne molecules, we have found a case where channel coupling is very important. In an alkyne molecule, there is a C-C triple bond which contains two it bonds. When the molecule has enough symmetry so that these two orbitals are degenerate, e.g. in 2-butyne where the point group symmetry is D3 and the it orbitals are a degenerate pair, then a photoionization calculation done with the full symmetry of the molecule can correctly include the coupling between the two ionization channels using symmetry. This effect is especially prominent in the energy region near a shape resonance. When the molecule has lower symmetry, e.g. 1-butyne, then the two it orbitals are have similar energy, but are not degenerate. In such a case it is important to include the two strongly interacting ionization channels in a photoionization calculation to obtain the correct position of the shape resonance features. In a study on the recoil-frame photoelectron angular distributions (RFPADs) of the C (1s)-1 photoionization of CH4 we derived expression to include the effects of rotation between the time of the photoionization and the subsequent fragmentation of the molecule. Experiments on this system measured the RFPAD for the process where the core excited CH4 molecule decays by an Auger process leading to CH4
++ which then fragments into CH3++ H+. The two recoiling ion
fragments where measured in coincidence with the first photoelectron to yield the RFPAD. The experimental group found that for different fragment kinetic energy releases (KERs) the measured RFPADs were different. We found that computed RFPADs where rotation was included during a 0.5 ps delay between ionization and fragmentation lead to good agreement with the experimental RFPADs for low KER. Additionally, the high KER measured RFPADs could be explained using no time delay, suggesting that the different fragment KERs corresponded to different fragmentation pathways with different lifetimes.
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LAWRENCE LUM, I-1665, The University of Texas Southwestern Medical Center. MODULATION OF CANONICAL Wnt PATHWAY ACTIVITY USING SMALL MOLECULES. In the last funding period, we have achieved several milestones associated with the development of our compounds for regenerative medicine goals. Specifically, we have: a) demonstrated reproducible pro-regenerative effects of chemically mediated Wnt pathway suppression in homeostatic and injured heart and skeletal muscle tissue, b) elucidated the cellular processes that are compromised by suppression of Wnt signaling in muscle and that account for the pro-regenerative effects of IWR/IWP compounds, c) developed a playbook for promoting regeneration in adult animals premised upon transient suppression of Wnt signaling, and d) engineered a novel Porcn inhibitor molecule with picomolar activity against Wnt-mediated signaling as a candidate for clinical development. The adult heart is thought to consist primarily of post-mitotic cardiomyocytes that are resistant to replication. From an in vivo chemical screen to identify adult regenerative events dependent upon Wnt signaling, we observed heart and skeletal muscle health to improve following transient suppression of Wnt signaling. We demonstrated that Wnt inhibitors target fibroblasts to inhibit an atypical form of Wnt signaling in these tissues thereby decreasing the deposition of extracellular matrix proteins that suppress cardiomyocyte and skeletal muscle stem cell doubling. Transient exposure of infarcted heart tissue to a Porcn inhibitor one week after left coronary artery ligation resulted in a nearly 2-fold increase in ejection fraction compared to untreated animals. Although the anti-fibrotic responses seen with Wnt inhibitors are likely to be common to all tissues, the independence of some specialized tissues from Wnt signaling for maintenance such as muscle reveals a general framework for approaching chemically assisted regeneration in other tissues. LLOYD L. LUMATA, AT-1877, The University of Texas at Dallas. TRACKING AMINO ACID METABOLISM IN CANCER IN REAL-TIME HYPERPOLARIZED 13C MAGNETIC RESONANCE. It is my pleasure to report that we have successfully completed the objective for year one which is to optimize and get the highest "C NMR/MRI signal enhancements for each of the ten 13C amino acids that are potential biomarkers for cancer. These include the following 13C-enriched amino acids: [5-13C]glutamine, [1-13C]arginine, [1-13C]glycine, [1-13C]serine, [1-13C]proline, [1-13C]leucine, [1-13C]isoleucine, [1-13C]valine, [1-13C]alanine, and [1-13C]methionine. Using sample optimization methods and adjustments with our NMR/MRI signal-enhancing hyperpolarizer instrument, we were able to amplify the 13C NMR/MRI signal of these amino acids by a factor ranging from 20,000 to 50,000-fold! The hyperpolarization lifetimes of these enhanced signals, provided by T1 relaxation, were determined to be in the range of 20 s to 50 s‒these would translate to about one to four minutes of metabolic observation time window, which is at par or better than the clinically-proven hyperpolarized diagnostic tracer, [1-13C]pyruvate. Given these excellent optimization results, we believe that we are in a very strong position to materialize the next objective for year 2 which is to use these optimized hyperpolarized 13C amino acids in vitro and track real-time metabolism of cancer cells with unrivalled specificity and sensitivity. These optimization works in year one have resulted in published peer-reviewed papers which appeared in highly-respected journals Methods in Enzymology, RSC Advances, Magnetic Resonance in Chemistry, and Physical Chemistry Chemical Physics. Furthermore, our Welch grant has also enabled us to showcase our hyperpolarization research and presented a total of fourteen (14) talks and posters in local and international scientific conferences. Two Ph.D. students, Peter Niedbalski and Christopher Parish, were fully supported by the Welch grant in year one. In return, these two PhD students have mentored a Welch Summer Scholar in our lab, Arthi Kozhumam, a high school student from Austin, TX. In summary, the Welch grant has been a major source of support not only in research, but also in educational fronts. Given the superb NMR/MRI signal enhancements that we have obtained in year one, I believe that we are well-positioned to achieve the next successful and exciting results in year two. JODIE L. LUTKENHAUS, A-1766, Texas A&M University. DISCOVERING THE RICH ELECTROCHEMISTRY OF NITROXIDE RADICAL-MODIFIED CONJUGATED POLYMERS. This year's objective is vital in our whole project since charge transfer mechanisms in poly(4-(3-thienylalkyloxy)-2,2,6,6-tetramethylpiperidin-1-yloxy) (P3TAT) electrodes was not explored in literature. Whereas fundamental knowledge related to the charge transfer mechanism in such PTAT polymer electrodes could reshape our understanding on designing high-performance polymer electrodes for energy storage. To date, we have discovered a reliable way to electropolymerize the monomers of thiopenes bearing nitroxide radicals to prepare these P3TAT thin film electrodes in situ. The detailed synthesis of this special class of conjugated radical polymers was published in ACS Macro Letters, and a facile spray-on method of making polyaniline composite electrodes was reported in ACS Applied Materials & Interfaces. This year, we further investigated the energy storage and charge transfer activities on such PTAT electrodes in a standard three-electrode system employing lithium foil as counter and reference electrodes. During the galvaonstatic charge/discharge experiments, we discovered a two-step charging process from 3.0 V to 4.2 V in such PTAT electrodes. The first flat plateau is ranged from 3.5 V to 3.8 V, and the second starts from 3.8 V to 4.2 V with a steeper slope. This observation indicates both polythiophenes and nitroxide radicals were involved in the energy storage process. Further quantitative analysis revealed that nitroxide radical moieties contributed over 80% of its capacity when the PTAT cell is only charged up to 3.8 V. In addition, we discovered a possible internal charge transfer in such PTAT electrodes using a potentiostatic pulse technique. Currently, a manuscript regarding the electrochemistry is in preparation. This preliminary data provides fundamental understanding on designing novel radical polymer electrodes with different redox activities. Publications in Section 3 arise from the current Welch project.
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JIANPENG MA, Q-1512, Baylor College of Medicine. BIOCHEMICAL STUDY OF THE FUSOGENIC CONFORMATIONAL TRANSITION OF INFLUENZA HEMAGGLUTHININ. Influenza virus HA, a homotrimeric glycoprotein crucial for membrane fusion, undergoes a large-scale structural rearrangement during viral invasion. X-ray crystallography has shown that the pre- and post-fusion configurations of HA have disparate secondary, tertiary, and quaternary structures, where some regions are displaced by more than 100 Å. However, critical questions such as how the transition of this scale even takes place and what the driving forces are remains poorly addressed. There is strong evidence that the primary trigger for this rearrangement is the low pH environment of a late endosome. In the past year, to understand the structural basis and the dynamic consequences of the pH trigger, explicit-solvent molecular dynamics simulations were employed to investigate the initial stages of the HA transition. Our results indicate that lowered pH destabilizes HA and speeds up the dissociation of the fusion peptides (FPs). A buried salt-bridge locks the FPs and may act as one of the pH sensors. In line with recent observations from simplified protein models, we found that, after the dissociation of FPs, a structural order-disorder transition produces a highly mobile HA. This motion suggests the existence of a long-lived asymmetric, or "symmetry-broken" intermediate during the HA conformational change. This intermediate conformation is consistent with models of hemifusion, and its early formation during the conformational change has implications for the aggregation seen in HA activity. ALLAN H. MACDONALD, F-1473, The University of Texas at Austin. SPINTRONICS IN TWO-DIMENSIONAL MATERIALS. My Welch grant supports theoretical research that is directed toward advancing understanding of the electronic Properties of graphene sheets and other two-dimensional systems, including the surface states of topological insulators. I continue to work on the fundamental properties of atomically two-dimensional graphene. One important element of the physical properties of two-dimensional materials is related to the appearance of moire patterns when two-dimensional materials with different orientations or with different lattice constants are overlaid. This research includes work with a fundamental physics emphasis and work that has an eye toward applications. For example, moire patterns in graphene sheets enable new possibilities for electrical modulation of THz light. In the past year we have published a detailed analysis of THz features in the optical absorption by graphene sheets that are aligned with hexagonal boron nitride substrates. A new topic that has been added to my Welch program in the past couple of years is the study of topological matter, including topological insulators, and topological superconductors and the surface states that are associated with the topological properties of these materials. Topological materials are characterized by topological quantum numbers and sometimes, as in the case of the quantum Hall effect, to macroscopic properties that are very accurately quantized. In the past year I have investigated the fundamental issue of quantization of the macroscopic magneto-electric response that is associated with topological insulators, concluding that there are finite corrections to exact quantization. I continue to work with Welch support on bilayer-exciton condensation, and related phenomena in two-dimensional materials. A new and growing focus is on condensed states which mix quanta of light with quantized excitations of coherent matter. Finally, I have been devoting considerable attention to a long term project that is coming close to fruition which aims to provide a text book that educates the next generation of condensed matter physicists. This work is a joint effort with two long-term collaborators, and will be published within the next year by Cambridge University Press. The steady support for my program provided by the Welch foundation will be acknowledged in the preface to this textbook. FREDERICK M. MACDONNELL, Y-1301, The University of Texas at Arlington. PROTON-COUPLED ELECTRON TRANSFER MECHANISMS OF DNA CLEAVAGE BY PHOTOEXCITED AND GROUND-STATE RUTHENIUM POLYPYRIDYL COMPLEXES. We have previously demonstrated that the two Ru(II) complexes, [(phen)2RuII(tatpp)RuII(phen)2]4+ (P4+) are good inhibitors of tumor growth in vivo in a mouse model and cut DNA under hypoxic conditions in vitro. Past years' data have established that H-atom abstraction from the deoxyribose unit of DNA is induced by the monoreduced form of the complexes. In this report, we have begun to explore the mechanism by which P4+ induces apoptosis in malignant cultured human cell lines in order to establish if the DNA cleavage process is active in vivo. Ruthenium polypyridyl complexes (RPCs) similar in structure to P4+ but lacking the bioreducible tatpp ligand do not cleave DNA. These RPCs are cytotoxic at concentrations from 1 to 100 µM (IC50) and appear to function via depolarization of the mitochondrial potential, as evidenced by confocal fluorescent microscopy techniques. P4+ also has some basal level of mitochondrial poisoning but generally is more cytotoxic (1-10 µM IC50) than the other RPCs and more selective for malignant cells. For example, the IC50 for P4+ on non-malignant HUVEC and HAVSMC cell lines is ~100 µM, whereas the other non-redox active RPCs are equitoxic towards malignant and non-malignant cell lines. A combination of biochemical and chemical methods, including confocal fluorescent microscopy, cell fractionation and Ru content determination by ICP-MS, DNA fragmentation studies (Comet analysis), and assays for apoptosis are being used to determine the site of chemical action for P4+ in cells. If we can demonstrate that DNA cleavage is the event which initiates apoptosis, we can demonstrate that this unusual proton-coupled electron transfer reaction between DNA and P4+ is functional in vivo. JOHN B. MACMILLAN, I-1689, The University of Texas Southwestern Medical Center. ROLE OF NON-ENZYMATIC TRANSFORMATIONS IN NATURAL PRODUCT BIOSYSTHESIS. In previous years we had identified the ammosamides, discoipyrroles and bohemamines as families of natural products that involve one or more non-enzymatic steps in the formation of the final NP. We have continued to study these particular families of compounds to gain a better understanding of the mechanisms by which these reactions occur and understand the breadth of reactivity they can undergo. We have also identified new classes of NPs (compounds 1 ‒ 4) that are formed via non-enzymatic chemistry and have been exploiting this chemistry to study structure-activity relationships. In the case of complex polyketides 1 ‒ 4 (as well as the bohemamines) these dimeric NPs are formed via a non-enzymatic reaction between twoequivalents of a monomeric
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NP and an equivalent of formaldehyde. These molecules exhibit modest antibacterial activity against Gram-positive bacteria. By understanding the route of dimerization, we have been able to generate a library of analogs that incorporate a variety of aldehydes to improve biological features.
A key aspect of this research has been to utilize NMR active isotope labels (13C, 19F and 15N) to both study the mechanisms by which this chemistry occurs and identify new NP scaffolds. We were able to use 2D NMR coupled with 15N labeled substrates to elucidate the full mechanism of. A key aspect of this research has been to utilize NMR active isotope labels (13C, 19F and 15N) to both study the mechanisms by which this chemistry occurs and identify new NP scaffolds. We were able to use 2D NMR coupled with 15N labeled substrates to elucidate the full mechanism of formation of the discoipyrroles. DMITRII E. MAKAROV, F-1514, The University of Texas at Austin. THEORY AND SIMULATIONS OF FAST SINGLE-MOLECULE DYNAMICS. 1. Earlier work from the Makarov group, supported by the Welch foundation, has led to the prediction that, in the absence of high symmetry, mechanochemical transformations performed at low forces should predominantly exhibit the anti-Hammond effect, where the mechanical force pushes the transition state away from the reactant, resulting in superexponential increase of the reaction rate with the force. Experimental detection of this effect, however, has remained elusive because of inaccessibility of the low force regime. In collaboration with the group of A. Matouschek (UT), J. Marko (Northwestern U.) and H. Li (U. of British Columbia), which employed a combination of magnetic tweezers measurements, atomic force microscope single-molecule pulling, and theoretical analysis, it was now established that the mechanical unfolding of the protein spectrin exhibits anti-Hammond effect, as predicted. 2. In a related development, the Makarov group proposed a general theory of mechanochemical reaction paths. This theory, in particular, has rigorously answered the long-standing question of reducibility of the problem of mechanochemical process to a one-dimensional description: The answer depends on whether the process in question exhibits Hammond or anti-Hammond effect, with a one-dimensional model only possible in the former case. 3. Theoretical description of average transition paths was proposed, which enables obtaining such characteristic paths from single-molecule measurements and interpreting them in terms of simple diffusive models. 4. Distributions of forces in random polymer networks have been analyzed using coarse-grained computer simulations; The results provide experimentally testable predictions regarding the bulk mechanical response of polymeric materials that incorporate mechanophores whose mechanical behavior has been characterized at a single-molecule level. DAVID J. MANGELSDORF, I-1275, The University of Texas Southwestern Medical Center. LIGAND BINDING PROPERTIES OF NEMATODE ORPHAN NUCLEAR RECEPTORS. For Project 1 we have been investigating the role of the nuclear receptor DAF-12 in the life-cycle of nematodes. In the free-living nematode C. elegans, analogous determination between dauer arrest and reproductive growth is governed by dafachronic acids (DAs), a class of steroid hormones we discovered ligands for the nuclear hormone receptor DAF-12. Together with our collaborator on parasitic nematodes, Dr. Sparky Lok (U. Penn.), we tested the hypothesis that DAs also regulate development in Strongyloides stercoralis, a therapeutically intractable human parasite. We found that DA stimulated 100% of post-parasitic first-stage larvae (Li s) to develop to free-living adults instead of infectious (i)L3s, while 70% of post-parasitic L1 s developed to iL3 in controls. We also found that DA prevented post-free-living iL3 arrest and instead stimulated larvae to develop to free-living rhabditiform third- and fourth-stages, compared to 0% in the control. Overall, these data demonstrate that DAF-12 signaling regulates S. stercoralis development and further confirm our hypothesis that targeting DAF-12 may be an effective way to interrupt the parasitic lifecycle. For Project 2 we made the unexpected finding that FGF21, a hormone that regulates metabolic stress in response to starvation and ketogenic and high-carbohydrate diets, also governs taste preference. We found that FGF21 administration markedly reduces sweet and alcohol preference in mice and sweet preference in cynomolgus monkeys. In mice, these effects required the action of FGF21 in the central nervous system and were observed to correlate with reductions in dopamine concentrations in the nucleus accumbens, the reward center of the brain. Because FGF21 is in human clinical trials, these findings raise the possibility that FGF21administration could affect nutrient preference and other reward behaviors (e.g., drug addiction) in humans, which we are continuing to investigate.
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ARUMUGAM MANTHIRAM, F-1254, The University of Texas at Austin. SYNTHESIS AND PROPERTIES OF TRANSITION METAL OXIDES WITH UNUSUAL VALENCE STATES. In continuation of our work on the mixed ionic-electronic conducting oxides belonging to the Swedenborgite-type RBaCo4O7+δ (R = Y, In, and Ca) family, we have focused on the substitution of Ga3+ for Co2+/3+ in RBaCo4-xGaO7+δ to obtain good phase/chemical stability while keeping the thermal expansion coefficient (TEC) low (7.5 – 9.5 × 10-6 K-1) to be compatible with that of the electrolytes employed in solid oxide fuel cells (SOFC). We find the phase stability at the SOFC operating temperatures of 500 – 800 °C increases with increasing Ga content up to x = 0.5 with R = Y0.5In0.5, while still maintaining a high electrical conductivity of ~ 5 S cm-1 above 600 °C and offering good oxygen reduction reaction (ORR) activity in SOFC. Also, the oxygen storage capacity of these samples at low temperatures increases with increasing Y or Co content. We have established the sensitivity and intricacies of various cationic substitutions on the first charge-discharge cycle of the lithium-rich layered oxide cathodes Li[Li0.2Mn0.4Co0.4-xMx]O2 (M = Cr, Fe, and Ni) in lithium-ion cells. For instance, Fe substitution for Co dramatically decreases the reversible capacity due to the decreased metal-oxygen bond covalence, while Cr substitution for Co increases the capacity due to the multi-electron redox reaction involving the oxidation of Cr 3+ to Cr6+. On the other hand, the substitution of Ru4+ for Mn4+ in Li[Li02Mn0.6-xRuxNi0.2]O2 causes a decrease in cell voltage due to the shifts in the relative positions of the Ru4+/5+:4d and O2-:2p bands and the splitting of the Ru4+:t2g band into bonding/antibonding orbitals by the formation of Ru-Ru dimers. We have demonstrated that nanobean SnO2-embedded TiO2 hollow submicrospheres as a scattering layer in dye-sensitized solar cells (DSSC) promote simultaneously dye absorption, light harvesting, and electron transport, resulting in a significant improvement in conversion efficiency. We have also shown that the low-cost, carbonized egg-shell membranes exhibit conversion efficiency comparable to that of expensive Pt counter electrodes in DSSC. With a catalyst-selective strategy employing inexpensive electrocatalysts, we have developed a membraneless alkaline direct formate fuel cell concept, which avoids the necessity of practically unavailable alkaline anion-exchange membranes and overcomes the scalability limitations of traditional membraneless fuel cells. EDWARD M. MARCOTTE, F-1515, The University of Texas at Austin. A MASS-SPECTROMETRIC-BASED MAP OF UNIVERSALLY-SHARED ANIMAL PROTEIN COMPLEXES. We have now completed a draft map defining the core set of dominant, stable multiprotein complexes shared across the animal kingdom, and in the process, performed the deepest characterization of animal proteomes on record. With Welch funding (and collaborator Andrew Emili, Toronto), we previously developed a strategy based on deep biochemical fractionation of cells or tissues, analyzing each fraction by tandem mass spectrometry to identify reproducibly co-purifying (hence, likely interacting) proteins. Our initial efforts on the human proteome (published in Cell, 2012) surveyed ~5,500 proteins across ~2,000 fractions. For the current project, we analyzed >6,000 biochemical fractions from diverse cell, tissue, and whole animal samples from human, mouse, fly, frog, sea urchin, sea anemone, the nematode C. elegans, and, as an phylogenetic outgroup, the slime mold Dictystelium, These data span ~13,000 proteins (each shared evolutionarily between humans and other animals) across >6,000 native biochemical fractions, encompassing >70 million protein abundance measurements. Using automated analyses of our thousands of tandem mass spectrometry datasets on Texas Advanced Computing Center supercomputers, we derived a map of nearly 1,000 protein complexes shared across the animal kingdom, defining the biochemical "wiring diagrams" underlying most animal cells. Our large-scale approach to biochemical fractionation revealed entirely new, uncharacterized protein complexes. One in particular worth noting (which we named the "Commander" complex) is a 500 kDa, 15 subunit protein complex that we showed was required for proper animal head, eye, and brain development, and whose failures likely underpin a rare type of human congenital intellectual disabilities. This work is in press at Nature. PAUL MARSHALL, B-1174, University of North Texas. KINETIC AND PRODUCT STUDIES OF COMPLEX-FORMING REACTIONS IN THE GAS-PHASE. Following 266 nm pulsed photolysis of KCl vapor in the presence of O2/N2 mixtures at 1 atm, the concentration of K atoms was monitored via time-resolved laser absorption at 766.5 nm over ca. 750-1300 K. At the lower temperatures single exponential decays of [K] yielded the third-order rate constant for addition, kRI, while at higher temperatures equilibration was observed in the form of double exponential decays of [K], which yielded both kRI and the equilibrium constant for KO2 formation. km can be summarized as 1.07 × 10-30 (T/1000 K)-0.733 cm6 molecule-2 s-1. A van't Hoff analysis constrained to fit the computed ∆S298 yields a K-O2 bond dissociation enthalpy of 184.2 ± 4.0 kJ mol-1 at 298 K and ∆fH298(KO2) = -95.2 ± 4.1 kJ mol-1. The corresponding D0 is 181.5 ± 4.0 kJ mol-1. This value compares well with a CCSD(T) extrapolation to the complete basis set limit, with all electrons correlated, of 177.9 kJ mol-1. Relative rate measurements have been made using continuous UV photolysis of mixtures of Cl2 and two reactants, acetone and 1,2 dichloroethane, coupled with monitoring of reactant concentrations via FT-IR spectroscopy. Initial results are in accord with literature data. ANGEL A. MARTI-ARBONA, C-1743, Rice University. RUTHENIUM(II) PHOTOLUMINESCENT PROBES FOR SENSING AMYLOID-B OLIGOMERS IN REAL-TIME. Inspired in our previous Welch supported research (JACS 2011, 133, 11121; JACS 2012 134, 20776; JACS 2013 135, 10810) on ruthenium complexes for sensing amyloid-β aggregation, we discovered during this year of research that the rhenium complex [Re(CO)3(dppz)(py)]+ (dppz = dipyrido[3,2-a:2',3'-c]phenazine); Py = pyridine) display unconventional "light switching" properties when interacting with amyloid-β aggregates. Our studies indicate that [Re(CO)3(dppz)(py)]+ displays minimal photoluminescence in aqueous solution or in the presence of monomeric Aβ, however presents an increase in photoluminescence in the presence of fibrillar Aβ of 9.4 fold. Interestingly a second light-switching effect is seen after light irradiation with a photoluminescence increase of 100%. This second light switching is unprecedented and not seen in the previously investigated [Ru(bpy)2(dppz)]2+. We believe
this second light-switching process is related to protein oxidation, which could inhibit quenching of [Re(CO)3(dppz)(py)]+ by some amino acids. HPLC/MS studies confirm that upon illumination, a large proportion of Aβ peptides present an increase in mass, some of which are consistent with oxygen addition. We also found a dissociation constant of 2.8 ± 0.6 µM for the interaction of [Re(CO)3(dppz)(py)]+ with Aβ, with a binding stoichiometry of 2.8 Aβ peptides per every [Re(CO)3(dppz)(py)]+ derived from Job plots. The dual-light switching behavior of [Re(CO)3(dppz)(py)]+ presents a variety of advantages, among them it allows monitor Aβ aggregation in real-time with improved sensitivity. This manuscript will be submitted very soon for publication. We have also developed iridium probes for detecting histidine. These probes present long photoluminescence lifetimes. We found that the lifetime of the complex bound to the free histidine is 5 times shorter that bound to histidine containing proteins. This has allowed us to develop a methodology to quantify free histidine even in the presence of histidine containing proteins. When the iridium probe is added to a solution containing free histidine and proteins, the resulting luminescence decay contains components that belong to the protein and the free histidine. Deconvoluting the time-decay into the different exponential components allows to separate the contribution of free histidine. CALEB D. MARTIN, AA-1846, Baylor University. NEW POWERFUL LEWIS ACIDS AS METAL-FREE CATALYSTS. This past year has been productive accentuated by the publication of eight manuscripts. Two papers were on the synthesis of heteroarenes by the insertion of a phosphinidene unit or an oxygen atom into boroles. Three additional papers explored the ring expansion reactions of boroles with 1,2-dipolar substrates to generate unsaturated seven-membered rings. The reactivity of boroles with E-H substrates gave diverse results, which led to two publications. The eighth publication was a review on our efforts in the reactivity of boroles. Current efforts on this area of geared toward using boroles to make low band gap materials and generate unusual boracycles. In the preparation of new boron Lewis acids, we have been targeting species with T-shaped geometries. Thus far we have been able to prepare a borane featuring a tridentate ligand that bends the angle significantly to approximately 150 degrees. The ligand has N,N',N"-chelation that diminishes the Lewis acidity, however the compound has interesting fluorescence. We are close to publishing a paper on this work and current efforts are geared toward enhancing the Lewis acidity. STEPHEN F. MARTIN, F-0652, The University of Texas at Austin. SYNTHESIS OF BIOLOGICALLY RELEVANT MOLECULES. A series of important advances in synthesis and chemical biology were made during the past year. We finished the synthesis of a late stage precursor of the anticancer antibiotic citreamicin rl. We completed work involving the preparation of new compounds having skeletal substructures found in actinophyllic acid and assessing their anticancer activity. We continue to develop our modular approach to generating diverse nitrogen heterocycles that may be quickly transformed into novel compounds having an array of biological activities. In collaborations with several neurobiologists, compounds having potential for treating traumatic brain injury, pain, alcohol withdrawal, and Alzheimer's disease were identified, and studies to establish the utility of these compounds and their mechanism of action are ongoing. A project directed toward using optogenetics to map those neuronal circuits in mice that are involved in specific activities was initiated, and we designed novel caged molecules that will be used to control gene expression using visible light. We continued studies to assess how changes in the structures of small molecules that bind to the Grb2 SH2 domain and hepatitis C viral protease affect energetics and structure in their bimolecular associations. We continued our studies of inhibitors of the methionyl-tRNA synthetase of T. brucei, the parasite that causes African sleeping sickness, and these are nearing completion. ELISABETH D. MARTINEZ, I-1878, The University of Texas Southwestern Medical Center. SMALL MOLECULE INHIBITORS SELECTIVELY TARGETING MALARIA EPIGENETIC ENZYMES. Over the first grant period, we have been able to clone, express and purify PfJmjC3, a putative malarial enzyme with potential demethylase activity on histone substrates. We have preliminary results indicating that this enzyme may be active in removing methyl groups from histone 3 trimethylated at lysine 4. We have replicated these findings in multiple enzymatic preparations. We are now developing distinct assays to measure enzymatic activity through independent means to confirm/validated this enzyme activity on various substrates.
In addition, we have begun to evaluate potential Jumonji demethylase inhibitors for anti-malarial activity on the intact parasite. We have selected 10 candidate compounds with lowest EC50 against the parasite and no toxicity on uninfected human erythrocytes or normal human epithelial cells. These will be potential specific inhibitors. We plan to test these top candidates for their inhibitory activity against malaria enzymes and for their specificity in targeting the parasite vs. host Jumonji activities. Finally, we continue to characterize all of our epigenetic inhibitors for their effects against mammalian enzymes deregulated in disease to understand their action and selectivity in parallel with these efforts.
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Figure 1: Preliminary enzymatic activity of purified recombinant PfJmjC3 on H3K4me3 measured by ELISA. ANDREAS MATOUSCHEK, F-1817, The University of Texas at Austin. STRUCTURE AND FUNCTION OF A NANO-SCALE BIOLOGICAL MACHINE. 1) We were able to synthesize and characterize polyubiquitin chains consisting of 2 to 8 ubiquitin moieties linked through Lysine 48 or 63. In collaboration with Professor J. Brodbelt and her laboratory, we characterized these chains using a new mass spectrometry approach developed by the Brodbelt lab. We published the method in Analytical Chemistry. We are now adapting methods to make polyubiquitin chains linked through Lysine 11. 2) We were able to develop a method to attached the Lysine 48-linked polyubiquitin chains as well as the Lysine 63-linked polyubiquitin chains to fluorescent proteasome substrates. This was an important breakthrough we struggled with for more than a year. 3) We have adapted proteasome purification methods to allow us to purify proteasome complexes from yeast in which specific ubiquitin receptors have been attenuated by mutations. Three proteasome subunits are known to bind ubiquitin or ubiquitin-like domains Rpn1, Rpn10, and Rpn13. We are able to make and purify proteasome complexes in which any one, any combinations of two, or all three receptors are attenuated. 4) We have begun to use the kinetic proteasome degradation assays developed over a previous funding period with the defined proteasome substrates, unattached ubiquitin chains, and defined proteasome particles to dissect precisely how proteasome substrates are recognized by the proteasome. Over the next funding period we hope to obtain quantitative information on the interaction of each of the ubiquitin receptors with the different poly-ubiquitin chains to reveal how the proteasome deciphers the ubiquitin code. SEIICHI P.T. MATSUDA, C-1323, Rice University. TERPENE BIOSYNTHESIS. We investigated a wide variety of plants to look for the unusual triterpene alcohols y-amyrin and isoursenol. These compounds are almost never reported, but whether they are catalytically inaccessible or not advantageous to generate was unknown. We discovered that these "rare" compounds are actually nearly ubiquitous. y-Amyrin and isoursenol are so easily generated that they are frequently byproducts of enzymes that have undergone selective pressure to make other structures. The cationic rearrangements that generate oxidosqualene cyclase products are fundamentally prone to generate diversity, and they readily form y-amyrin and isoursenol. The likely reason these compounds are infrequently characterized is evolutionary rather than catalytic; plants seem to not find these compounds to be useful. The extraordinary control that lanosterol synthase exerts on cation rearrangement is well-known. It generates four rings and seven stereocenters in constructing the sterol nucleus. No minor lanosterol synthase products have been described. We recently identified twelve distinct lanosterol synthase minor products, which illuminate numerous aspects of the catalytic mechanism. We establish that energetic barriers to these minor structures are in the range of 4-5 kcal, high enough to minimize biological impact of minor products and substantially higher than are normally seen in cation rearrangement. JEREMY A. MAY, E-1744, University of Houston. THE TOTAL SYNTHESIS OF BIOACTIVE NATURAL PRODUCTS VIA NOVEL STRATEGIES. The report of our cascade involving hydrazone decomposition, dediazotization, cyclopropenation, carbene generation, and C-H bond insertion that is initiated using NaOSiMe3 was published (J. Am. Chem. Soc. 2015). This report has garnered enough interest from the community that we were asked to write a focus review on the topic, which will is submitted for publication (Asian J. Org. Chem. 2016). A review on the use of C-H bond insertion for the synthesis of bridged polycycles was compiled and published (Bell. J. Org. Chem. 2016). A novel ligand for dirhodium(II) complexes with a BINOL backbone has been synthesized and used to make a functional catalyst for carbene-based transformations. It's use for the hydrazone-initiated cascades has provided products in ~90% yield and 99:1 er. This work is submitted for publication (ACS Catal. 2016). A nitrene-initiated carbene cascade has also been developed that uses a reactive nitrogen species to initiate a cascade reaction that terminates in C-C bond formation via C-H bond insertion. A report of this work is under review (Chem. Sci. 2016).
We have completed an investigation on our initial strategy for the synthesis of Maoecrystal V that utilizes a bridgehead C-H bond insertion (Tetrahedron 2016). Extensive studies show the factors in bond selectivity, and we have devised a second-generation strategy that will provide complete selectivity and synthesize the target in fewer steps. A synthesis of flexinine, a natural product with selective anticancer activity, has been initiated. Progress to date has seen the incorporation of all of the carbons found in the target. One last intramolecular C-C bond and adjustment of oxygenation are needed to complete the synthesis. The target will be tested in collaboration with MD Anderson. The diol-catalyzed enantioselective conjugate addition of organoboron nucleophiles has progressed to include cyclopropyl ketones as substrates for homoconjugate addition reactions. A report of the use of Bu4NHSO4 as a mild and inexpensive catalyst for this transformation is under review (Org. Lett. 2016). We have also found that GaCI3 catalyzes the formation of all-carbon quaternary centers for this reaction, and we are exploring the substrate scope using that reagent. Lastly, preliminary enantioselectivity has been seen using our published BINOL-catalyzed conditions (Angew. Chem. Int. Ed. 2015). We have also developed alternative conditions for problematic substrates (2-indoles and pyrroles) that we will report by the end of the summer (Org. Lett. 2016). JENNIFER A. MAYNARD, F-1767, The University of Texas at Austin. CONTROL OF PROTEIN FOLDING QUALITY: PORTABLE SEQUENCE DETERMINANTS OF ANTIBODY STABILITY. Over the past year has been in three areas. We identified three amino acid residues changes that prevent aggregation in an antibody Fab fragment and showed that these could be transferred into other antibodies to increase their resistance to aggregation upon heating. Inspection of the Fab protein structure allowed us to speculate about the mechanism of stabilization, which affects the entire protein. We then used this knowledge to assist in de novo prediction of antibody sequences able to fold and bind a simple peptide ligand. Protein prediction of any kind remains a challenging task, yet four predicted sequences not only produced stably folded protein but bound ligand with low nanomolar affinity. Efforts to crystallize these antibodies are on-going. The knowledge has also been applied to understand folding of very small (-12 kDa), single domain antibodies. Since these binding faces are formed by a single domain, as opposed to the two domains that normally join to form a ligand-binding site, the rules for folding are different and currently unknown. We have generated large libraries of single-domain antibody variants and selected those fold stably in order to identify residues that determine folding. Finally, in unpublished work we have used two sets of proteins that vary in surface charge (antibodies and green fluorescent proteins) to explore the effect of protein surface charge on stability and aggregation and whether this behavior can be reduced by environmental factors, such as increasing ionic strength and other co-solutes. KEVIN MCBRIDE, G-1847, The University of Texas M. D. Anderson Cancer Center. SMALL MOLECULE INHIBITORS OF EPIGENETIC EFFECTOR PROTEINS. In collaboration with the Frye Laboratory at The University of North Carolina, improved probes were synthesized and analyzed. An improved candidate probe, UNC2170, has been identified and analyzed. We found UNC2170 functions as an antagonist in cells by suppressing immunoglobulin class switch recombination (CSR). Some of these results were previously published (Perfetti et al. ACS Chem Biol, 2015) and reported in the previous progress report. We have been further analyzing the characteristics of this compound on cell function and found some toxicity effects at higher concentrations necessary to completely inhibit CSR. Our goal was then to identify improved candidates based on the UNC2170 structure. Additional candidates have been identified that have >2 fold activity against 53BP1 methyl-lysine binding activity over UNC2170. We are analyzing the activity of UNC2170 and these further improved compounds in our cell culture and B cell CSR models, particularly in regards to genome stability. In the course of these studies we have also identified another FDA approved pharmacological that affects immunoglobulin recombination processes. We have followed up this unexpected finding regarding effect on CSR and genome stability. Lastly, we are preparing to analyze these compounds in our mouse model system. OGNJEN Š. MILJANIĆ, E-1768, University of Houston. CONJUGATED BENZOBISOXAZOLE CRUCIFORMS AS FLUORESCENT SENSORS IN SOLUTION AND SOLID STATE. 1. We have synthesized and exhaustively characterized first examples of cross-conjugated benzobisimidazole "cruciform" fluorophores. These amphoteric species are capable of responding to both protonation and deprotonation with a pronounced optical response. 2. Significant advances have been made in the supramolecular chemistry of the shape-persistent arylene ethynylene macrocycles (AEMs). Specifically, we have shown that (a) these species can be coordinated to transition metals to yield mesoporous solids, and that (b) they are capable of encapsulating small fluoroarenes in their central cavities. 3. Using extensively fluorinated aromatic pyrazoles, we have created porous and highly robust molecular crystals. These systems are capable of binding fluorocarbons to the tune of up to 225% by weight, and can be used to qualify and quantify that binding through changes in powder X-ray diffraction pattern and UV/Vis absorption. 4. We have developed a one-step procedure for the production of shape-persistent macrocycles through benzoin condensation-based cyclooligomerization of aromatic dialdehydes. 5. We have continued our work on self-sorting on complex dynamic libraries in the presence of irreversible external stimuli and have demonstrated that both adsorption on silica gel and acid-catalyzed dehydration can be used for this purpose. 6. In collaboration with Sessler and Arslyn groups (UT Austin), we developed a series of porphyrin-anion supramolecular assemblies, which act as sensors for organic solvents and anions.
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We have successfully performed the first single nanocrystal absorption measurements of IR active plasmonic materials. Single nanocrystal spectra were revealed to be considerably narrower in linewidth than those observed by ensemble measurements, which suggests that these materials are in fact less lossy than ensemble measurements would suggest. The nature of this broadening in ensemble measurements comes from particle to particle variations in the concentration of the dopants that cause metal oxides to become plasmonic. The degree of variation in dopant concentration was confirmed by a correlation between the observed shifts in peak maximum of single particle spectra with their peak asymmetry, which is diagnostic of dopant induced damping of electron oscillation during the lifetime of the plasmon. These results are currently being prepared for publication. Additional achievements on the grant center around advances made in the expected near field enhancement around plasmonic metal oxide nanocrystals through modeling with the discrete dipole approximation. Enhancements of electric field at the surface of In:CdO can exceed 100x which is promising for applications to coupling to infrared absorption of molecular vibrations. Additionally, control over the relative absorption and scattering of particles was investigated, and indicate that controlling these different light matter interactions is achievable in these materials which is important for their application of local heating and for generating contrast in the IR. DELIA J. MILLIRON, F-1848, The University of Texas at Austin. PLASMONIC TRANSPARENT CONDUCTING OXIDE NANOCRYSTALS: DPOANT CHEMISTRY AND HETEROGENEITY. We have perfected and published syntheses on two new materials exhibiting LSPR in metal oxides that are pushing the limits of light concentration applications. For example, cerium doped indium oxide is an improvement upon tin doped indium oxide because the electronic structure of cerium dopants ameliorates some deleterious effects of dopant ions on carrier mobility in metal oxides. Additionally, we have further expanded our technique for single nanocrystal characterization of LSPR phenomena to perform statistical analysis of heterogeneity within a single batch of nanocrystals. Notably we were able to demonstrate that within a sample the effective dopant concentration per nanocrystal varies over a wide enough range to cause ensemble measurements to be poor indicators of the potential high performance of the nanocrystals due to inhomogeneous spectral broadening. We have also made improvements in our understanding of the electrochromic properties of films made from nanocrystals. We have published about ion transport through the films to get to nanocrystal surfaces for efficient switching, as well as how they can intercalate into the nanocrystals to change the LSPR features. Finally, we have expanded upon our suite of modeling approaches for metal oxide LSPR to be able to account for anisotropic crystal structures while solving for the dielectric function of our nanocrystals, an important expansion upon the existing approaches for extracting materials properties from the optical spectra of plasmonic materials. HAMID MIRZAEI, I-1849, The University of Texas Southwestern Medical Center. DEVELOPMENT OF A FULLY AUTOMATED 3D SEPARATION PLATFORM FOR DEEP PROTEOME FRACTIONATION: NOVEL DRUG DISCOVERY TOWARDS DETECTION OF LOW ABUNDANCE TARGETS OF SMALL MOLECULES. This year we perfumed a 3D fractionation of SILAC lysates from cells treated with or without the drug. Cells grown in media supplied with light amino acids were treated with vehicle (DMS0) and cells grown in cell culture media supplied heavy isotope coded amino acids (lysine and arginine) were treated with compound. Lysates from these two conditions where then mixed in 1 to 1 ratio. 20 mg of this mixture was then separated on the 3D system and fractionated into a 728 fractions. We next performed a detailed analysis to find protein complexes disturbed by this drug. To identify and quantify proteins fractionated by the 3D system, the raw mass spectral data from 728 fractions were processed by the latest version of MaxQuant (v.1.5.3.30). The software reported a total of 3,737 proteins with their corresponding H/L ratios. To identify protein complexes, we mapped our data to the CORUM database. After identifying the potential matches between our enriched proteins per each fraction and the database, we examined the enriched proteins by two strategies to find true complexes based on the CORUM database. We identified 575 complexes which were matched to our enriched proteins by all fractions. Afterwards, we performed Protein correlation profiling‒stable isotope labeling by amino acids in cell culture (PCP-SILAC) method to identify novel complexes. A very detailed flowchart of the method can be found in supplementary material. A total of 211 novel complexes were identified using PCP-SILAC. Briefly, after filtering of data, de-convolution of chromatograms into components, Gaussian curves are estimated and the method fits Gaussian models on each chromatogram, afterwards, the algorithm corrects for shifting by the re-alignment method in which the fitted curves are re-aligned to the migration scale to ensure maximum consistency for further analysis. Then a comparison between all chromatograms is made by t-test. Afterwards, protein-protein interactions are estimated. By using the clustering with overlapping neighborhood expansion (ClusterOne) algorithm, the complexes are identified. We will next identify the complexes showing changes due to the drug treatment. CHARLES B. MULLINS, F-1436, The University of Texas at Austin. NANO-STRUCTURED MATERIALS FOR CHEMISTRY. Over the past year we have conducted experimental investigations of (1) the lithiation/de-lithiation and sodiation/de-sodiation of solid nanostructured thin films as well as slurry-cast nanoparticles, (2) the photoelectrochemistry of water reduction and oxidation by visible light using nanostructured metal-oxide semiconductors as the light absorber as well as studies of electrocatalysts that can be placed on the light absorbers, and (3) the catalytic surface chemistry of gold and gold-palladium alloys. Several studies of molecular transformations on gold and gold-palladium surfaces were conducted since these catalysts show great promise at low temperatures. Additionally, much work was published this year regarding photo-assisted water oxidation and reduction. These latter efforts involved the search for both stable semiconducting light-absorbers as well as electrocatalysts. In this same line of research we also studied the mechanisms for carrier transport in metal oxide semiconductors. We also conducted research on lithium and sodium anode materials and electrode architectures.
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SIEGFRIED MUSSER, BE-1541, Texas A&M University System Health Science Center. SIGNAL PEPTIDE INTERACTIONS DURING TRANSPORT BY THE BACTERIAL TAT MACHINERY. The twin-arginine translocation (Tat) machinery transports folded proteins across a membrane that maintains ion gradients. The Escherichia coli Tat machinery is comprised of three proteins, TatA, TatB, and TatC. Our recent work indicated that Tat signal peptides bind to TatBC receptor complexes in a hairpin configuration, and suggested a model in which protein translocation across the membrane occurs via unhinging of this hairpin. Much of the past year was spent writing an extensive manuscript describing this Hairpin-Hinge Model. Data analysis, final control experiments and prediction tests have taken longer than anticipated, but the manuscript is almost complete. Additionally, numerous reagents were generated and proof-of-concept experiments were performed with the goal of testing this model with a single molecule Tat transport assay. In this assay, single membrane vesicles will be attached to a microscope coverslip surface, and cargos will diffuse to the tethered vesicles for transport into the vesicle lumen. We have demonstrated that: i) Tat transport occurs at room temperature (instead of 37°C), greatly simplifying light microscopy experiments; ii) efficient transport occurs with ATP (instead of NADH), which produces a long-lived electric field gradient necessary for single molecule observation; and iii) vesicles can be modified with biotin and tethered to the coverslip via an avidin linkage. As a previous dual-labeling protocol did not work as well as expected, a collaboration with Wenshe Liu (Chemistry Dept) was initiated to generate cargo proteins with two dyes for FRET experiments using an artificial amino acid. A new single molecule fluorescence microscope was installed that is now dedicated to our single molecule Tat transport project. With this solid framework, we expect to perform real-time single molecule FRET experiments within the next grant period. YUNSUN NAM, I-1851, The University of Texas Southwestern Medical Center. STRUCTURE AND FUNCTION RELATIONSHIP OF MICRORNA PRECURSORS. Our first Aim was to define different classes of pri-miRs, those that need extra help (eg. by helicases) for processing and those that are innately good substrates of Microprocessor. We discovered that most pri-miRs are better processed in the presence of helicases. After monitoring the rate of processing for many pri-miRs in vitro, we were able to identify which pri-miRs are superior substrates. In the process of establishing quantitative processing assays and measuring enzyme kinetics, we were able to determine how HP1 BP3 affects miRNA processing in collaboration with Qinghua Liu's group (in press). As we tried to establish the dependence of pri-miR processing on DDX RNA helicases, we were also able to determine high-resolution structures of the helicase with and without RNA. Future investigation of the helicase mechanism will help us determine how they regulate processing kinetics. In order to relate RNA conformation to processing efficiency (Aim 2), we successfully established a robust SHAPE analysis workflow, and we are screening many pri-miRs to determine a correlation between RNA conformation and maturation kinetics. Because RNA methylation was recently discovered to affect processing kinetics, we also reconstituted in vitro methylation using purified Mettl3/Mettl14 (in press), which will be used to further investigate the structure-function relationship of pri-miRs and their cleavage by Microprocessor. To determine the conformation of pri-miR in complex with Microprocessor (Aim 3), we have identified suitable RNA and protein constructs to form homogenous complexes that are stable during gel-filtration. Using various truncations of protein constructs, we are in the process of mapping where each domain contacts pri-miRs. After applying these biochemical analyses to several different pri-miRs, we will synthesize a unifying model to describe the architecture of the active processing complex, including the RNA features important for efficient maturation. DOUGLAS NATELSON, C-1636, Rice University. NOVEL SINGLE- AND FEW-MOLECULE VIBRATIONAL SPECTROSCOPIES. We have continued making strong progress. We have completed our studies of molecular junctions based on PCBM, comparing the evolution of single-molecule Raman spectra under bias in these structures with analogous junctions incorporating C60. Thanks to the dipole moment present in PCBM, in that system we see linear-in-bias spectral shifts showing a contribution from the vibrational Stark effect, in addition to quadratic-in-bias shifts from metal-molecule charge transfer. This work has been published in Nano Lett. We also did a careful study of optical heating in these plasmonic structures, with a goal of understanding and mitigating this effect to enable cryogenic conditions for simultaneous electronic spectroscopies. We found that the strongly temperature dependent thermal boundary resistance between the plasmonic metal and the dielectric substrate is extremely important. These results have been published in ACS Nano. We have performed a systematic examination of the surface-enhancement of infrared absorption (SEIRA) in nanostructures designed to leverage our insights gained in the nanojunction geometry. We have fabricated and modeled individual nanowires, nanowire dimers separated longitudinally by a nanogap, and nanowire dimers separated laterally by a nanogap. We compared SEIRA of the native silicon oxide on the fabrication substrates, finding that the lateral nanogap structures benefit from the nanogap, an effect likely increased by broken symmetry in the real structures. This work is going to be submitted for publication within a month. We have also been creating alternative structures with "gate" electrodes, to examine gated charge transfer's effect on the Raman response of molecules and monolayer materials. JOSEPH B. NATOWITZ, A-0330, Texas A&M University. NUCLEAR REACTION STUDIES. Our search for alternative reaction paths for heavy element production continued. During the past year, we built a second generation active catcher array. It is composed of 40 YAP (Yttrium-Aluminum Perovskite) active base modules. These modules provide the pulse shape discrimination (PSD) necessary to differentiate alpha decay from alphas emitted during spontaneous fission or as the result of scattered beam reactions with the active catcher. The addition of active bases allows a factor of ~1,000 in increased beam intensity before gain shifting occurs. Additionally, we replaced the waveform digitizers used for the active catcher array. The new array employs Struck SIS3316 digitizers (FADCs). These FADCs have a minimum 4ns bucket size but appropriate experimental
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conditions can reduce the time resolution to ~1ns. These digitizers also offer new capabilities in triggering and the waveforms may be shifted to provide up to 64us of history prior to the trigger. Figure 1 depicts the PSD available in the proposed YAP/PMT/active base configuration.
This array has now just been used in a two week experiment with the TAMU K500 Cyclotron. The reactions of 7.5 MeV/nucleon 197Au and 238U with 232Th were studied. The beams were pulsed at different millisecond intervals in order to be able to identify species of different half-life. All coincident waveforms were recorded. Many "events of interest" were detected. A complete analysis is underway. DONALD G. NAUGLE, A-0514, Texas A&M University. THE INFLUENCE OF REDUCED DIMENSIONALITY, DISORDER, AND SURFACES ON THE PROPERTIES OF SOLIDS. We have fabricated very well ordered arrays of magnetic nanorods and nanostripes directly atop thin metal superconducting films by electron- beam lithography and electrodeposition. In these new experiments, however, the magnetic nanostructures were electrically insulated from the superconducting films by a thin amorphous germanium barrier. Some striking differences in vortex pinning by these insulated magnetic nanostructures compared to our previous studies where the nanostructures were in electrical contact with the superconducting film (embedded in or atop the films) were observed. These differences depend on the ratios of fundamental scales (coherence and penetration depth with the period of the magnetic structure. In collaboration with J. C. Nie (Beijing Normal Univ.), we have described techniques to generate graphene nanoribbons and superlattices by liquid assisted manipulation of highly oriented pyrolytic graphite with a scanning tunneling microscope tip. This includes detailed analysis of the tip/sample interactions which enable preparation of moire superlattices, which should have rich band structures based on the moire superlattice period, by this simple route. We also have imitated studies of the influence of doping graphene at low temperature with adatoms (initially with lithium) to drastically modify its electronic structure. ANDRIY NEVIDOMSKYY, C-1818, Rice University. MAGNETIC ANISOTROPY AND ORDERING IN MOLECULAR AND SOLID-STATE MAGNETS: FIRST-PRINCIPLES CALCULATIONS AND EFFECTIVE SPIN THEORY. All the aforementioned research objectives have been successfully attained. (i) The first task has been accomplished by the graduate student Vaideesh Loganathan, who has studied the magnetic anisotropy in the promising ferromagnet Fe1/4TaS2. It is a strongly correlated electron material and we have used the so-called DFT+U method to perform a detailed investigation of how the magnetic properties depend on the strength (U) of the on-site Coulomb interaction. The role of spin-orbit coupling was also investigated and the findings have been reported in the recently submitted article. (ii) Magnetic frustrations are the key to understanding the properties of the iron pnictides, and we have published and submitted a series of papers addressing this important issue. The main work has been performed by the graduate students Zhentao Wang and Patricia Bilbao Ergueta, who have investigated the theoretical spin models using a variety of sophisticated analytical and numerical techniques. One of the key issues is the so-called nematic order in the iron pnictides, which emerges as a result of the magnetic frustrations. The model predictions match very nicely with the results of the inelastic neutron scattering (work performed in collaboration with the Welch supported Rice colleague Prof. Pengcheng Dai). (iii) The third thrust of research focuses on the spin-quadrupolar ordering, which we proposed theoretically to explain the puzzling nature of the hotly debated iron selenide (FeSe). The proposed ordering breaks the spin symmetry in a subtle way, and is an example of a spin-multipolar order (of which conventional magnetism, understood as spin-dipolar order, is a special case). Our calculated spin response in FeSe is in excellent agreement with the inelastic neutron data, and our paper has just appeared in Physical Review Letters. This effort lays the foundation for future work on multipolar orders, a subject of the PI's recently awarded Welch grant (starting June 1, 2016).
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KYRIACOS C. NICOLAOU, C-1819, Rice University. SNYTHESIS OF BIOLOGICALLY ACTIVE MOLECULES. a. ∆l2-Prostaglandin J3 (∆12-PGJ3) and at least 40 analogs have been synthesized. Some of these compounds have been evaluated at the National Cancer Institute for their antitumor properties while the remaining are currently being tested at NCI and another (academic) laboratory. b. A number of large maitotoxin fragments have been synthesized. c. The total synthesis of trioxacarcin DC-45-A2 has been accomplished. d. Our work on the total synthesis of viridicatumtoxin B including biological investigations has been completed. e. Synthesis of myceliothermophins C, D and E has been completed. f. Synthesis and biological evaluation of dimeric furanoid antitumor agents has been completed. g. Synthesis and structural revision of antibiotic CJ-16, 264 has been completed. h. The total synthesis of the antitumor agent shishijimicin A has been completed. DEEPAK NIJHAWAN, I-1879, The University of Texas Southwestern Medical Center. EXPANDING THE DRUGGABLE GENOME. Discovery of Tumor-Specific Inhibitors of Stearoyl CoA Desaturase. From a screen of over 200,000 compounds, we identified two small molecule scaffolds that were selectively toxic to a subset of the lung cancer cell lines. Bioavailable derivatives had anti-cancer activity in mouse models of lung cancer. We discovered that these small molecules are pro-drugs that are de-methylated by members of the type IV cytochrome P450 into irreversible inhibitors of stearoyl CoA desaturase (SCD). The development of previously reported inhibitors of SCD have been stymied by mechanism related adverse events in a specific skin cell, sebocyte. We demonstrated that our compounds in comparison to canonical SCD inhibitors has an improved therapeutic index by virtue of its activation in cancer cells but not sebocytes. Discovery of the target of CD437, an anti-tumor toxin. CD437 is a retinoid like molecule which is selectively toxic to cancer but not normal cells. We developed a forward genetic system using a colorectal cancer cell line to identify compound resistant mutations in POLA1 that lead to CD437 resistance. We discovered that CD437 is toxic by virtue of its ability to bind and inhibit POLA1. MICHAEL NIPPE, A-1880, Texas A&M University. SYNTHETIC STRATEGIES FOR THE PREPARATION OF SUPRAMOLECULAR AND COVALENT CAGE STRUCTURES CONTAINING CARBORANE MOIETIES. The majority of our work was dedicated to developing preparative routes to carborane containing linkers which will be utilized for the preparation of two specific supramolecular structures: Tritopic ligand L1 and ditopic ligand L2 which will generate supramolecular tetrahedral cages and trigonal helices, respectively. Although the synthesis of L1P via Ullmann coupling of Cu-carborane moieties and tribromobenzene had been reported in 2015 with ~80% yields, we were unable to reproduce similar high yields. We tested various Pd-catalysts but yields exceeding 20% were not observed. We also attempted Kumada-type coupling which did not improve the yield of the reaction. This step is currently the bottleneck in the synthesis of L1. We are planning to recrystallize Cu(I) sources and modify solvent conditions to improve the yield. However, L1P does react with 1-fluoro-4-nitrobenzene in the presence of base via SNAr to yield tritopic nitrobenzene substituted moieties which are the direct precursors to L1 via reduction of the nitro groups to amines. We successfully established a synthetic route to bitopic ligand L2 which involves coupling of acetal-protected iodopyridine to carborane-copper species and subsequent acidic deprotection to yield L2. We already started investigating the reactivity of three equivalents of L2 with two equivalents of ferrous triflate and two equivalents of a capping tren ligand to form a supramolecular helix. We observe the immediate formation of a dark blue species which is indicative of the anticipated formation of low-spin Fe(II) pyridine-imine complexes. Characterization of this material is currently ongoing. Lastly, support from the Welch foundation has allowed us to obtain results for research not covered in the original proposal: We prepared the first structurally characterized iso-carbonyl complex of Dysprosium and investigated its magnetization dynamics. This work has been published.
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QIAN NIU, F-1255, The University of Texas at Austin. BAND ENGINEERING FOR TOPOLOGICAL PROPERTIES IN GRAPHENE LIKE SYSTEMS. We have continued investigation of electronic properties of graphene like hexagonal lattices. In some tailored graphene superlattices, we find that the Dirac cones can be folded into the same valley and transformed into a gapless structure with quadratic band touching. When MoTe2 is placed on a magnetic insulator, we find that the proximity-induced Zeeman coupling can induce a giant valley splitting, a trait much desired for optoelectronic applications. In hexagonal lattices with inversion syrnmetry breaking, we find that phonons also have unusual valley contrasting properties. Much of the unusual electronic and phononic properties originate from the Berry curvature and magnetic moment of the Bloch states in the band structure. Besides the above-mentioned 2D systems, we have also investigated non-colinear antiferromagnets, finding large magneto-optical Kerr effect along with a big anomalous Hall effect. In addition, we have systematically analyzed orbital magnetic susceptibility in crystalline solids by a rather difficult second-order extension of our semiclassical theory. We find various geometric effects due to the Berry curvature as well as the quantum metric of the Bloch states, explaining large diamagnetic susceptibilities in narrow gap semiconductors and zero gap semimetals. PETER J.A. NORDLANDER, C-1222, Rice University. THEORETICAL INVESTIGATIONS OF CHEMICAL PROPERTIES OF NANOSYSTEMS. We have continued our development of aluminum as a low-cost and abundant plasmonic material and demonstrated its potential for technological applications by developing a CMOS compatible photodetector as well as vivid full-color plasmonic pixels with chromaticities exceeding the RGB standard. We have also developed a robust bottom-up chemical approach for mass production of aluminum nanocrystals. We have made significant further progress in our understanding of how plasmon-induced hot carrier generation can be exploited in light harvesting and photocatalytic applications. In particular we have developed a microscopic quantum mechanical model for hot carrier generation and demonstrated that hot electrons generated in a plasmonic nanoparticle can be injected into an adjacent MoS2 monolayer and induce a structural phase transition. We have developed new types of plasmonic antennas with strong optical resonances in the mid infrared that can be exploited in surface enhanced infrared spectroscopy applications. We can also report major progress in the area of quantum plasmonics with the development of a theoretical approach for modeling plasmon resonances in doped semiconductor nanocrystals and a demonstration of strong quantum mechanical effects in narrow plasmonic gap structures. We have developed an accurate and efficient theoretical approach for the modeling of electron energy loss spectroscopy of plasmon modes in arbitrarily shaped nanostructures and applied this approach for plasmon imaging of strongly coupled nanoparticle dimers. We also report significant progress in our understanding of nanoparticle enhanced solar steam generation where we have shown that the effect is caused by light trapping as a result of multiple light scattering. Finally, we report that the vibrational modes of nanoparticles on substrates can be strongly influenced by their adhesion layer. MICHAEL V. NORGARD, I-1852, The University of Texas Soutwestern Medical Center. STRUCTURE AND FUNCTION OF A NOVEL BACTERIAL REGULATOR. Functionally active recombinant derivatives of BosR are required as a prelude to solving its three-dimensional structure. To this end, we have created a series of BosR expression constructs. bosR encoded within the Borrelia burgdorferi B31 genome was cloned into the pET-SUMO vector and was hyper-expressed in E. coli. After induction with 1 mM IPTG, the His6-SUMO-BosR fusion protein was purified on Ni-NTA agarose under native conditions. The His6-SUMO tag was then removed with SUMO protease and recombinant BosR (rBosR) was further purified by an Äkta fast performance liquid chromatography (FPLC) system. We also cloned bosR into the plasmids pASK-IBA7PIus and pQE30, respectively, to express rBosR fused with a Strep tag or a His tag. Bioinformatics analyses suggested that the first six residues at the N-terminal and the last 15 residues at the C-terminal ends of BosR do not form secondary structure. Rather, these residues may interfere with protein structural determinations via NMR- and/or crystallography-based approaches. Therefore, we have also created constructs to express truncated rBosR with the N-terminal six residues and/or the C-terminal 15 residues removed. We now have nine different expression constructs encoding various versions of rBosR including: rBosR without a fusion partner, rBosR-Strep, His6-rBosR, and six truncated versions of rBosR (rBosR with the N-terminal six residues removed, rBosR with the C-terminal 15 residues removed, and rBosR with the N-terminal six residues and the C-terminal 15 residues removed) fused with Strep or His6 tags. Via affinity chromatography and FPLC, we have obtained soluble proteins with ≥ 95% homogeneity for all of these nine versions of rBosR. In vitro electrophoretic mobility gel-shift (DNA-binding) assays (using B. burgdorferi rpoS promoter DNA as the target) have confirmed that all of the recombinant versions of rBosR, including full-length and truncated variants, remain functional. These developments have set the stage for further currently ongoing structural and functional determinations. SIMON W. NORTH, A-1405, Texas A&M University. FUNDAMENTAL IMAGING STUDIES OF CHEMICAL REACTIVITY. We have since made significant progress in demonstrating that product vector correlations can be observed in roaming systems, and therefore, provide a window into the stereodynamics of important bimolecular reactions. We are currently engaged in studying the photodissociation of benchmark systems CH2O, CH3CHO, and CH2CO using a newly acquired and modified ion imaging instrument. We have extended our method to extract speed-dependent vector correlations from sliced ion images to include multiphoton detection. This should enable a broader application of the technique, specifically to a wider range of chemical systems which will ultimately provide a stringent test for modern theoretical chemistry and increase of understanding of chemical reactivity. Our results on OCS and O3 photodissociation have validated our method and have provided new insights into the dynamics in these systems. Manuscripts on both systems are currently in preparation. In the case of O3 photodissociation we have identified the mechanism responsible for the interesting odd rotational state suppression in the O2 products first observed by Valentini and co-workers.
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KATHRYN A. O'DONNELL, I-1881, The University of Texas Southwestern Medical Center. DISSECTING NOVEL MECHANISMS OF LUNG CANCER PATHOGENESIS. We discovered that PCDH7 potentiates ERK signaling by facilitating interaction of Protein Phosphatase 2A (PP2A) with its potent inhibitor, the SET oncoprotein. We demonstrated that PCDH7 interacts with SET in HBECs and in human KRAS mutant NSCLC cells. Moreover, we found that PCDH7 interacts with PP2A-A (a structural subunit of the PP2A complex) and PP2A-C (a catalytic subunit). Consistent with an important role for SET function downstream of PCDH7, we showed that knockout of SET (using CRISPR/Cas9) significantly reduced phospho-ERK and transforming ability of HBEC-shp53-PCDH7-KRASG12V cells. We also observed a significant reduction of PP2A activity in cells expressing mutant KRASG12V and PCDH7 as compared to cells expressing KRASG12V alone, and this effect was reversed in SET knockout cells. Collectively, these studies demonstrate that PP2A and its inhibitor SET are critical for PCDH7-driven MAPK signaling. Thus, we have uncovered a new regulatory input that leads to activation of the MAPK pathway, a critical driver of lung tumorigenesis. Moreover, our finding that the intracellular domain of PCDH7 serves as a scaffold that facilitates assembly of a protein complex that activates MAPK signaling may provide a broadly applicable concept for understanding the functions of other PCDH family members in normal physiology and disease. These findings are described in a manuscript that is currently in revision. We are now initiating studies to develop/test the therapeutic efficacy of PCDH7 antibodies and we expect to complete Aim 2 in years two through three. JOHN S. OLSON, C-0612, Rice University. CHEMICAL MECHANISMS OF LIGAND BINDING TO HEME PROTEINS. We completed a collaborative study of water penetration into human HbA tetramers following photo-dissociation of bound CO. Spectrokinetic analysis was used to monitor heme hydration, which competes with ligand recombination. The results show a strong coupling between water penetration into the distal pockets of the Hb subunits and quaternary structure, with more water entering β subunits in the low affinity T quaternary state and reducing the rate of bimolecular CO rebinding from solvent than in α subunits. In other collaborative studies, we are: (a) helping to increase the time resolution of Hb and Mb X-ray crystallographic experiments using the X-ray free electron laser source at the Stanford LCLS facility; and (2) completing time resolved X-ray studies with Mb mutants that allow visualization of escape through the distal histidine gate. As part of our goal to determine the mechanisms involved in heme protein assembly, we developed and published a wheat germ extract-based translation assay to examine quantitatively the factors that govern expression of holoMb. Our results show that high-level expression of holoMb, and presumably all monomeric heme proteins, requires an ultra-high stable native apoglobin state that can rapidly bind hemin. Hemin affinity itself is not important. We are currently testing the applicability of these ideas to expression of tetrameric hemoglobin, which is complex and involves self-assembly of α and β subunits. In contrast to hologlobin assembly, the key factors in oxidative degradation of hemoglobins are the rate of autooxidation and hemin affinity. Apoglobin stability is much less important. In the case of adult human hemoglobin, quaternary structure plays a dominant role in inhibiting both autooxidation and hemin dissociation by limiting water penetration into the heme pocket. MOHAMMAD A. OMARY, B-1542, University of North Texas. GROUND- AND EXCITED-STATE BONDING ASSORTMENTS IN LUMINESCENT MOLECULES AND CORRESPONDING EXCITONS. Beyond-unity photoluminescence quantum yield materials: Au(I) isonitrile complexes and Zr(IV) metal-organic frameworks have been demonstrated to exhibit photoluminescence quantum yield (ᶲPL) > 100%. While D. L. Dexter described the pertinent photon-splitting phenomenon theoretically since 1957 (Phys. Rev. 108, 630), these findings represent its first experimental demonstration in molecular materials. The figure here shows the raw spectral data for solid ArNCAuCI (Ar = CF3-biphenyl) and a solution of the internal standard quinine sulfate, for which (ᶲPL) values of 167% and 54% were derived. "Carrot-inspired" design of colored coordination polymer from colorless constituents: Coordination polymers of Cu(I) with "back-to-back" diimine ligands with unsaturated or no bridging moieties entail infinite conjugation of colorless d10 ions and heterocyclic aromatic π units over 1D molecular wires, 2D nanosheets, or 3D frameworks. This produces deeply colored solids akin to those exhibited by carrot and other fruits and vegetables whereby C=C bonds are oligomerically conjugated. Besides the absorption (and emission) colors realized experimentally, DFT computations predict that one can also tune charge/polaron (electron or hole) and ion (proton, cation or anion) conductivity upon systematic metal/ligand variations.
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JOSÉ ONUCHIC, C-1792, Rice University. EXPANDING THE PROTEIN FOLDING LANDSCAPE TOWARD BIOMOLECULAR MACHINES. Using the DCA + SBM approach, a method was created to predict the structure of homodimers. DCA predicts intra and inter-protein contacts but the dimeric contacts can be sorted out when there is a known monomer structure. This approach successfully predicted protein dimer complexes with a resolution comparable to accurate experimental methods. These studies demonstrate that our lab has developed a framework for studying protein-protein interactions that combines traditional molecular dynamics simulations with genomic information. In addition to this dimer work, another new direction of research involves the use of DCA to construct sequence-dependent statistical potentials for proteins. We utilized DCA to infer a Potts model Hamiltonian governing the correlated mutations in a protein family. The inferred pairwise statistical couplings were used to generate the sequence-dependent heterogeneous interaction energies of a SBM. Considering the ribosomal S6 protein and its circular permutants as well as the SH3 protein, we demonstrated that these models quantitatively agree with experimental data on structure and folding mechanisms. This work serves as a new framework for generating coevolutionary data-enriched models that can potentially be used to engineer key functional motions and novel interactions in protein systems. KIM ORTH, I-1561, The University of Texas Southwestern Medical Center. ELUCIDATE THE BIOCHEMICAL MECHANISM USED BY Vibrio VopQ TO INDUCE AUTOPHAGY. We have continued our studies on the biochemical activity of VopQ over the last year. We previously demonstrated Vibrio parahaemolyticus uses the Type III effector. VopQ, to alter autophagic flux by manipulating the partitioning of small molecules and ions in the lysosome. We next demonstrated that the accumulation of autophagic vesicles is due the fact that VopQ is a potent inhibitor of vesicular membrane fusion based on an in vitro membrane fusion model. VopQ inhibits the final step of membrane fusion by inhibiting trans-SNARE complex formation. Future studies involve structural analysis of VopQ and we have initiated a collaboration with a Cryo-EM group to elucidate the 3D structure of the VopQ pore. Using yeast genetics, we plan to further characterize VopQ by identifying mutants of VopQ that either inhibit fusion or prevent dc-acidification of vacuoles. We have also established a protocol to identify chemical inhibitors of VopQ. OLEG V. OZEROV, A-1717, Texas A&M University. HIGHLY UNSATURATED CATIONIC GROUP 10 TRANSITION METAL PINCER COMPLEXES. Our approach to generation of highly reactive transition metal cations relies on using cationic main group reagents to abstract halides or pseudohalides from the coordination sphere of a neutral transition metal precursor. The cations involved need to be partnered with robust weakly coordinating anions to ensure reactivity and properties of an unsaturated cation. Our research thus covers exploration of weakly coordinating anions, cationic main group reagents, and transition metal complexes and supporting ligands. During last year, we completed work on a broad investigation of a series of amido-based pincer ligands, establishing both their redox properties and donor abilities. Based in part on this work, we identified carbazole-based NNN pincer ligands as promising for supporting highly reactive platinum cations because of its lower basicity and resistance to oxidation. Our initial attempts at generation of NNN-supported Pt cations resulted in a discovery of an unusual cyclometallation reaction. On the other hand, we explored Pt complexes of a very strongly donating silyl-based PSiP pincer ligand which does allow generation of unsaturated Pt cationic complexes, but the high donor ability of silyl renders these cationic complexes less reactive. In addition, partial support from the Welch Foundation grant has helped advance a few related projects over the last year. This especially pertains to the chemistry of pincer-supported Rh and Ir fragments that are isoelectronic to our target cationic complexes of group 10 metals. We discovered that certain pincer-supported Rh complexes can function as competitive C-S coupling catalysts, while with Ir we have been pursuing a genuinely novel reaction of dehydrogenative borylation of terminal alkynes.
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JEREMY C. PALMER, E-1882, University of Houston. METASTABLE LIQUID-LIQUID PHASE TRANSITIONS IN MOLECULAR MODELS OF TETRAHEDRAL FLUIDS. Supercooled water. (i) An alternative theory to the LLPT hypothesis suggests that water's unusual behaviors may be explained by a dynamic separation of relaxation time scales, in which density fluctuations in the supercooled liquid relax orders of magnitude faster than those associated with crystalline order. We have scrutinized this alternative theory in four different water models [Palmer et al., Mol. Phys., in press, 2016]. For each model, we observe that density fluctuations relax slower than fluctuations in crystalline order in the supercooled regime, thereby providing strong evidence against the central physical argument behind the alternative theory. (ii) In an extension of the supported project, we have performed the first fully atomistic molecular simulation study examining the stability of a small globular protein (Trp-cage mini-protein) in deeply supercooled water. It has been suggested that proteins denature under cold experimental conditions because their native structure becomes destabilized by increased hydration of residues in their hydrophobic core. Our simulation study shows, however, that cold denaturation of Trp-cage is driven by the favorable enthalpy change associated with hydration of polar residues, demonstrating that hydration of hydrophilic residues must be considered when interpreting protein folding behavior under cold conditions. This study has been submitted to PNAS for publication. Supercooled silica. We have recently demonstrated the existence of an LLPT in an ionic model of liquid silica using state of the art free energy calculation. Following the supported plan of work, we are now in the processes characterizing critical fluctuations and examining their influence on crystallization kinetics and mechanism. KEITH H. PANNELL, AH-0546, The University of Texas at El Paso. SILOXYMETHYLAMINES: MASKED AMINATION REAGENTS FOR NEW METAL LIGANDS. Using (triethylsiloxymethyl)dimethylamine, Et3SiO-CH2NMe2, 1, prepared from the metal-catalyzed reaction between Et3SiH and DMF, HC(O)NMe2, we have now demonstrated that 1 reacts with a range of main group element RnE-H compounds, E = O, S, N and P, to form (dimethylamino)methyl products, RnECH2NMe2. For the previously unreported diaminomethane products R2NCH2NMe2, R2= Et2, PhMe, we have observed for the first time their capacity to disproportionate to form a 1:2:1 equilibrium mixture of R2NCH2NR2 : R2NCH2NMe2 : Me2NCH2NMe2. Each of these diamines can be isolated, and completely characterized by spectroscopy and single crystal X-ray analysis, as their Mo(CO)4(diamine) complexes formed via reaction with norbornadieneMo(CO)4. The reaction of 1 with PhNH2 results in the formation of the new triamine (Me2NCH2)2NPh, which can also be isolated as its Mo(CO)4 complex, coordinating in a bidentate manner via the terminal NMe2 group. Each of the new diamine and triamine Mo complexes act as efficient catalysts for the silane reduction of amides to amines, proceeding via the formation of the siloxymethylamine title products. CHANDRASHEKHAR PASARE, I-1820, The University of Texas Southwestern Medical Center. BIOCHEMICAL ROLE OF IRAK-1 REGULATED CASPASE-1 ACIVATION AND CLEAVAGE. We have made very good progress in the past year in understanding the biochemical role of IRAK-1 in regulating rapid NLRP3 inflammasome activation. We have now discovered that IRAK-1 and its kinase activity are important for rapid inflammasome activation but not for priming induced inflammasome activation. More importantly, we find that absence of IRAK-1 and IRAK-2 completely abrogates priming induced inflammasome activation suggesting that lack of IRAK-1 is compensated by IRAK-2 and we are in the process of understanding the exact biochemical role of IRAK-2 in priming induced inflammasome activation. Further work has also led to the discovery that IRAK-1 regulates rapid NLRP3 inflammasome activation by recruiting TRAF-6, an E3 ligase. These new data suggest that IRAK-1 activates TRAF-6 which potentially ubiquitinates either NLRP3 or ASC, and we are in the process of testing this hypothesis. As previously reported, we have successfully generated truncated mutants of IRAK-1 that lack either the death domain or the C-terminal domains. Early experiments have suggested that reconstitution of IRAK-1 deficient macrophages with full length IRAK-1 but not the C-terminal lacking IRAK-1 rescues the ability of macrophages to induce rapid inflammasome activation. These experiments need to be confirmed and can lead to the potential possibility that the C-terminal domain of IRAK-1 is interacting directly or indirectly with either NLRP3 or ASC. Furthermore, we have initiated a collaboration with Dr. Ian Fraser and Dr. Aleksandra Nita- Lazar at Laboratory of Systems Biology, NIAID, NIH to systematically identify the substrates phosphorylated by IRAK-1. This collaboration will result in identification of new targets of IRAK-1 and further work will focus on understanding the biochemical mechanisms by which IRAK-1 and its target regulate caspase-1 cleavage. The collaborative work has led to some interesting findings on the role of human IRAK-1 in TLR activation and a manuscript with these findings is currently under consideration at the journal Science Signaling. MATTEO PASQUALI, C-1668, Rice University. PHYSICAL CHEMISTRY OF NANORODS AND NANOPLATES. We continue to study the fundamental behavior of solutions and colloidal dispersions of nanoparticles of tubular or plate-like shape and on their self-assembly into macroscopic functional materials. We published a comprehensive article on the relationship of phase transitions to aspect ratio in solutions of carbon nanotubes (CNTs). For this goal, we revisited a century-old method for measuring the molecular weight of polymers and colloids through solution shear viscosity, and showed that shear viscosity is increasingly ineffective for long, tubular structures, whereas extensional viscosity can be used to measure aspect ratio simply and effectively. We studied CNT samples synthesized with different methods by eight different sources and showed that the transition from isotropic to biphasic liquid crystal solution is controlled by CNT aspect ratio and polydispersity, irrespective of details on chirality, diameter, and number of walls, so long as the CNTs molecular structure is highly crystalline. We showed that CNT length polydispersity is surprisingly moderate compared to that of polymers synthesized by random polymerization.
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We used this understanding of solution phase behavior to directly assemble continuous films of CNTs onto insulating cylindrical substrates, so as to make coaxial cables. In collaboration with NIST, we tested the cables electrical and mechanical properties and showed that cable performance depends on CNT molecular perfection as well as the alignment and packing of the CNT layer. We showed that CNT cables could displace metal coaxial cables in certain applications. In collaboration with AFRL, we studied the field emission of solution-spun CNT fibers and showed that field emission performance is also controlled by CNT molecular structure as well as fiber alignment and packing. By using Neutron and X-ray scattering in conjunction with cryo-TEM and cryo-SEM, we are studying the morphology of CNT liquid crystalline phases and have strong initial evidence for an unusual columnar phase at low CNT concentration. We are studying the relationship of CNT architecture, phase behavior, and rheology of these fluids. We have developed a new method to purify Boron Nitride Nanotubes from impurities including BN flakes. MARGARET A. PHILLIPS, I-1257, The University of Texas Southwestern Medical Center. PURINE SALVAGE PATHWAYS AS POTENTIAL DRUG TARGETS IN Trypanosoma brucei. Human African trypanosomiasis (HAT) is a fatal vector borne disease of sub-Saharan Africa putting 70 million people at risk. Purine and pyrimidine biosynthetic enzymes are known drug targets, making them attractive targets to exploit for the development of new inhibitors against HAT. Salvage pathways that are used by Trypanosoma brucei for the formation of purine nucleotides are redundant so it was originally presumed that none of the enzymes in the pathway would be essential. Contrary to expectations we have demonstrated that GMP synthase (GMPS) is essential to sustain an infection in a mouse model. GMPS null cells are auxotrophic for guanine and host blood does not contain sufficient guanine to rescue the loss of GMPS. These studies validated GMPS as an essential enzyme for T. brucei growth and infectivity. We generated recombinant GMPS and developed an enzyme assay that is compatible with high throughput screening approaches, thus achieving our goals of validating a new target for a drug discovery project in T. brucei and of setting up the tools necessary to move the project from target validation to lead discovery. We are currently focused on characterizing inosine mono-phosphate dehydrogenase (IMPDH) and adenylosuccinate lyase (ADSL) to assess their potential as a drug targets for HAT. LIONEL W. POIRIER, D-1523, Texas Tech University. NEW METHODOLOGIES FOR ACCURATE QUANTUM CALCULATIONS OF THE DYNAMICS OF ATOMIC NUCLEI. The proposal for this grant outlined the following three areas for the 2013-2016 grant cycle: 1) symmetrized Gaussian (SG) basis set methods; 2) quantum trajectory methods (QTMs); 3) molecular applications. Although substantial strides continue in all three areas, this past year has been remarkable for the attention that the Welch-sponsored research has received in the popular press. 1) and 3) were mentioned in a recent Austin American Statesman article (7/25/15). However, it was 2) that led to well over 100 press articles (Nature News, Yahoo News, The Huffington Post, Science Daily, New Scientist, Phys.Org News, Cosmos, KPFT Houston public radio, etc.), as well as invitations to serve as a featured Huff Post blogger, and also speaker at a videographed event at UC Berkeley (for which there will also be a companion book). Regarding 1) and 3), last year's 120 acetonitrile project has now been published in CPL as a (new) Editor's Choice article; however, we have also now completed our calculation of 100,000 quantum states of benzene (30D), which will soon be submitted for publication. A practical user's guide was also published last year, in Applied Mathematics. Comprehensive rovibrational calculations were also performed for SO2, with forays now being made into the HOCO system. Over the last twelve months, Welch support has led to three new published articles and three new articles submitted or accepted. The Welch research projects have also led to twelve invited oral presentations within the same twelve month period, seven of which were international, one of which was a plenary talk (Aston University Workshop on Bohmian Mechanics and Hydrodynamics, Birmingham, UK), and one of which was a named memorial lecture (Eötvös Loránd University, Budapest, Hungary). PATRICK RYAN POTTS, I-1821, The University of Texas Southwestern Medical Center. THERAPEUTIC TARGETING OF MELANOMA ANTIGEN (MAGE) GENES. We have made the seminal discovery that MAGE-A3/6-TRIM28 ubiquitin ligase drives transformation and tumor growth of otherwise normal cells through ubiquitination and subsequent proteasomal degradation of the AMPK tumor suppressor. These findings validated MAGE-A3/6-TRIM28 as a therapeutic target and were recently published in Cell. We have worked to develop an in vitro high throughput alpha-screen assay to identify compounds that could inhibit binding of MAGE-A3/6 with TRIM28. However, we have recently encountered technical problems with this screen. As we try to sort these problems out, we have turned to screening for inhibitors of another oncogenic MAGE protein, MAGE-B2, that is even more potent that MAGE-A3/6. We have recently found and submitted for publication that the MAGE-B2 protein functions to drive tumorigenesis through regulating the stability of a select group of mRNAs sharing a common sequence in their 3'UTRs called AU-rich elements. Biochemical studies revealed that MAGE-B2 binds to two specific RNA binding proteins, AUF1 and HuR, and that this binding promotes their association with a new distinct set of mRNAs. Thus, MAGE-B2 can alter the spectrum of rnRNAs bound to and whose stability is regulated by AUF1 or HuR. Given this novel mechanism of action for MAGE-B2 and oncogenes in general, we are currently performing a cell based 200,000 compound screen to identify compounds that selectively target and decrease viability of cells expressing MAGE-B2, but not control cells. Our initial pilot screen results look promising and thus we are currently performing the larger screen. In the end, we hope to identify compounds that will selectively target MAGE-B2-expressing cancer cells, but not normal somatic cells that are typically MAGE-B2-negative.
B. V. VENKATARAM PRASAD, Q-1279, Baylor College of Medicine. X-RAY CRYSTALLOGRAPHIC STUDIES ON VIRUSES AND VIRAL PROTEINS. During 2015-2016, we have made exciting progress toward the proposed aims. Our structural studies are related to three medically important viruses: Rotaviruses, major pathogens of infantile gastroenteritis; Noroviruses, which cause epidemic diarrhea in humans; and influenza viruses, which cause seasonal and pandemic flu. In regard to rotaviruses, (1) we determined the glycan specificity of neonate-specific rotavirus strain and provided the structural basis for the unique glycan specificity exhibited by the this strain and its zoonotic partner with strong implications to host specificity, age restricted tropism and zoonosis (Hu et al, 2015, under review) (2) we successfully crystallized and determined the structure of the viral phosphodiesterase (PDE) domain of rotavirus VP3 that antagonizes cellular antiviral oligoadenylate synthetase (OAS)/RNase L pathway, this is the first structure of a viral PDE (Ogden et al., 2015); (3) we completed our studies on protein-protein interactions that regulate viroplasm formation (Viskovska et al) and our structural studies on NSP4 coiled-coil domain to provide a structural basis for unique structural transformation from tetramer to pentamer regulated by calcium and pH (Sastri et al., 2015). In regard to noroviruses, (1) we successfully determined the first structure of the norovirus P domain in complex with neutralizing antibody (Shanker et al., in preparation). In regard to influenza virus, we have carried out biophysical and biochemical characterization of NS1 protein with its cellular partners, CPSF 30 and PI34 kinase and crystallographic studies are in progress. We also provided our crystallographic expertise in a collaborative study with Dr. Palzkill on β-lactamase variants. HAN PU, C-1669, Rice University. EXOTIC MOLECULES FROM SPIN-ORBIT COUPLED ULTRACOLD ATOMS. Over the past year, we have focused our research on the properties of spin-orbit coupled ultracold atoms. Here spin-orbit coupling refers to a coupling between the internal states of the atom and its center-of-mass motion, induced by the action of properly arranged laser fields. In the work published in Physical Review Letters 115, 253902 (2016), we considered a three-dimensional Bose-Einstein condensate subject to spin-orbit coupling with attractive inter-atomic interaction. We found that, under proper conditions, the system forms as a stable self-trapped structure in free space. This is the first time that a stable soliton-like structure was ever discovered in the absence of any external trapping potential. While most works in spin-orbit coupled cold atoms concern with the coupling of atomic spin with its linear momentum, we investigated a situation where the atomic spin is coupled to its center-of-mass angular momentum. We show that this system can support novel quantum states. Finally, we also investigated the quantum magnetic properties of spin-1/2 fermions in the presence of both spin-orbit coupling and repulsive interatomic interaction and show that itinerant ferromagnetism can be found in such a system. EMILY L. QUE, F-1883, The University of Texas at Austin. EXPLORING THE USE OF Cu(II) IN 19F MAGNETIC RESONANCE CONTRAST AGENTS FOR IMAGING BIOLOGICAL REDOX. In the current grant year, our research focused on the following: A) determine the feasibility of using Cu(II) as a 19F MRI contrast agent B) explore the effects of ligand scaffold on 19F NMR properties and C) design and test sensor scaffolds that utilize metals including Cu(II) for detecting changes in redox environment in biological contexts. A) To determine the feasibility of using Cu(II), containing only one unpaired electron, as a relaxation agent for fluorine, we synthesized several copper chelates containing fluorinated tags. Partial to complete quenching of the 19F NMR signal was observed for all complexes, indicating Cu(II) effectively reduces the T2 relaxation times of ligated fluorines. This is significant as typically, highly paramagnetic ions such as Gd(III) (S=7/2) are used for MRI. B) Another advance has been our study of the effect of distance between paramagnetic center and fluorine tags on contrast agent properties. We have optimized a synthetic route for integrating different tags into copper chelates. This has allowed us to determine that even at extended distances (e.g. four ethylene glycol repeat units), significant relaxation effects are observed at the fluorine center when complexed to Cu(II) and other paramagnetic metal centers. This work is the subject of two manuscripts in preparation. C) We have expanded into designing sensing scaffolds that exploit change in metal oxidation state to detect different redox environments. Specifically, we have developed Cu(II) scaffolds that are reduced to Cu(I) within hypoxic cells, or cells experiencing below-normal oxygen tensions. This is relevant in cancer, where oxygen-deficient tumors are associated with aggressive malignancies. We have published a proof-of-concept of this in JACS, where we demonstrated selective in-cell reduction of a Cu(II) complex and subsequent 19F signal turn-on. Based on the positive results, over the next year we will continue to pursue new sensing scaffolds including Cu(II) hypoxia-sensing scaffolds with improved bio-compatibility to enable work in animal models, Cu(II)-based scaffolds for detecting biological reductants including cysteine, and systems that may enable the detection of biological oxidants. FLORANTE A. QUIOCHO, Q-0581, Baylor College of Medicine. STRUCTURE-FUNCTION RELATIONSHIPS IN PROTEINS. Inorganic phosphate (Pi) is probably the most important nutrient for cell life. In cell, Pi uptake is extremely specific. It is also limiting, which implies that transport of both monobasic and dibasic Pi would be advantageous. The Pi-binding protein (PBP), the initial or primary Pi receptor of bacterial ABC transport system remains the best system to investigate Pi specificity. We have collected at Oak Ridge National Lab a 1.99 A neutron diffraction data set from a large crystal of fully perdeuterated PBP obtained at pH 4.5 and refined the structure in Phenix as neutron data with an X-ray-derived reference structure. The current refinement model has an Rwork of 21.2%, an Rfree of 23.3%, and excellent geometry statistics. As was seen in a prior pH 4.5 hydrogen/deuterium (H/D) exchange neutron structure, there is clear neutron density for the single hydrogen attached to the phosphate in omit density map, verifying that the dibasic Pi is bound rather than the monobasic form which is the predominant specie at pH 4.5. This new finding has important ramification in atomic level understanding of Pi specificity in transport systems. The other primary purpose of determining the perdeuterated structure was to confirm the position of the Phe 10 and Thr 11 amide hydrogens, which make hydrogen bonds with the Pi, and ensure that all hydrogens were accounted for. The two amide hydrogens did
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not have any visible density, implying no exchange with deuterium in the H/D exchange structure. Notably, in the perdeuterated structure, there is clear density for Phe 10 and Thr 11 amide deuteriums, confirming their position. There was no additional positive density in the binding site; therefore, all deuteriums in the binding site have been placed correctly, which accounts for all 13 protons involved in hydrogen-bonding interactions between PBP and Pi. We will use this structure along with the H/D exchange neutron structure, subangstrom-resolution X-ray structure, and other biophysical data to draw novel conclusions about phosphate specificity of a protein associated with cellular uptake. ARUN RADHAKRISHNAN, I-1793, The University of Texas Southwestern Medical Center. FLUORESCENT SENSORS FOR MEASURING CHOLESTEROL IN LIVE CELLS. In the past year, we have made considerable progress in understanding how Scap, a polytopic membrane protein, senses cholesterol levels in cells and ensures that cells maintain an optimal concentration of cholesterol. Using biochemical and biophysical approaches, we have carried out a systematic dissection of the domains of Scap. In a recently published study, we showed that Scap's cholesterol sensing ability is critically governed by the interaction between two large loops that extend into the lumen of the endoplasmic reticulum (ER). Scap uses one of these loops to sense the levels of ER membrane cholesterol, and then relays this information through interaction with the second loop to eventually control the activation of transcription factors that increase cholesterol synthesis. We also created a soluble form of the cholesterol-sensing loop of Scap that should aid structural studies. In another published study, in collaboration with Dr. Nieng Yan from Tsinghua University, we used X-ray crystallography to determine the structure of a mycobacterial homolog of Insig, an ER resident protein that binds Scap when cholesterol levels are high. This interaction is crucial for Scap's ability to control the activity of transcription factors in a cholesterol-dependent manner. The structure of the bacterial Insig has provided us with a molecular framework to begin to understand how Insig and Scap interact in a cholesterol-dependent fashion in the ER membranes of human cells. In the coming year, we hope to extend these advances to gain the first pieces of structural information on Scap through a combination of crystallographic and cryo-electron microscopy approaches. MARK G. RAIZEN, F-1258, The University of Texas at Austin. MOLECULAR MICROSCOPY IN SPACE AND IN TIME. In the past year we completed a series of measurements of short-time Brownian motion in molecular fluids. We conducted a precise test of the energy equipartition theorem for a Brownian particle in liquid, and found excellent agreement with the added-mass model. We have extended our previous measurements of short-time Brownian motion to complex molecular fluids. These results, soon to be submitted for publication, will provide a much deeper understanding of microrheology of complex molecular fluids on fast timescales. In parallel work, we continued our development of a neutral atom microscope that has nanoscale resolution, is surface-specific and chemically-sensitive. We are now optimizing a pulsed hexapole magnetic lens to focus metastable neon atoms to the nanoscale. A surplus hemispherical electron analyzer was provided by a colleague, requiring a lot of work to bring it back to operation, but it is now functioning and is being tested with known surfaces to verify the spectral resolution. We are combining both capabilities in the same system to demonstrate this new microscope, which will use atoms to "see" atoms and molecules on surfaces. RAMA RANGANATHAN, I-1366, The University of Texas Southwestern Medical Center. STRUCTURAL PRINCIPLES OF PROTEIN ROBUSTNESS AND EVOLVABILITY. In prior work supported by the Welch Foundation, we discovered a general architecture for proteins in which the constraints that provide for folding and biochemical activities are localized in small networks of amino acids (called "sectors") built around and extending from protein active sites. The sparsity and location of sectors suggest a simple idea for how proteins can be both tolerant to mutation ("robustness") and able to make rapid functional changes ("evolvability") in response to fluctuating environments. Basically, the idea is that robustness comes from the mutability of regions outside the sector and that evolvability comes from mutations within the sector that can cooperatively cause large changes in protein function. We tested this sector hypothesis in context of three specific aims proposed, all of which are now complete. In Aim one, we developed very high-throughput next-generation sequencing based approaches for comprehensive mutagenesis and globally studied the pattern of amino acid importance to protein function in both PDZ protein interaction modules and the TEM-1 b-lactamase enzyme (conferring antibiotic resistance in bacteria). The data confirm our predictions and were published in two papers (McLaughlin et al., Nature 491:138 and Stiffler et al., Cell 160: 882). In aims two and three, we set out to look directly at the path of adaptation to new function using the PDZ domain as a model system using our newly developed tools for global mutagenesis, x-ray crystallography, and statistical analysis of protein sequences. The data reveal a new structural principle for adaptation in which mutations within the sector specifically permit the acquisition of new functions while retaining the existing function. This class of mutations (so-called "conditionally neutral") is thought to be critical for the evolvability of proteins, but there was no structural principle for their location and mechanism. This work completes the proposed specific aims, and is now under review for publication. In addition, we have written a comprehensive methods paper describing the elucidation of sectors in proteins (Rivoire et al, in review), and an associated software toolbox (pySCA) that should enable broad further testing of the concept of protein sectors.
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HAI RAO, AQ-1747, The University of Texas Health Science Center at San Antonio. THE LAST LEG OF p53’S JOURNEY TO DEATH CHAMBER. Recently, we identified XPC as a key player in p53 turnover. XPC was previously known as a key DNA repair factor. Our recent data revealed that XPC works with the Ub ligase Mdm2 to promote the degradation of p53 by the proteasome. Specifically, after MDM2 E3 ligase recognizes p53 and covalently attaches ubiquitin molecules, a protein complex composed of Rad23 and XPC is found to be required for getting p53 to the proteasome. As XPC plays dual roles in DNA repair and proteolysis, we have investigated whether XPC couples DNA repair with checkpoint recovery via p53 degradation. We examined specific binding defects associated with XPC mutations and found that XPC mutations alter p53-induced cellular events. In addition, we have begun to define the mechanism underlying XPC-mediated p53 turnover. We dissected the interaction between XPC and human MDM2 through domain mapping and found that mutations defective in the XPC-MDM2 binding affect p53 degradation. The components of the ubiquitin/proteasome system are attractive drug targets, as illustrated with the efficacy of proteasome inhibitors in blood cancer treatment albeit with some side effects. Since XPC regulates a subset of proteolysis and exhibits more substrate selectivity than the proteasome, XPC is likely a better drug target with less adverse side effects. Identification of XPC as a novel p53 regulator presents a means to manipulate p53 level and function. Our study would not only elucidate the mechanism of XPC-facilitated p53 turnover, but also aid the search for novel strategies to boost p53 activity in cancer therapy. FRANK M. RAUSHEL, A-0840, Texas A&M University. ENZYME REACTION MECHANISMS. TrpH or YciV (locus tag: b1266) from Escherichia coli is annotated as a protein of unknown function that belongs to the polymerase and histidinol phosphatase (PHP) family of proteins. Enzymes from the PHP family have been shown to hydrolyze organophosphoesters using divalent metal ion cofactors at the active site. We discovered that TrpH is capable of hydrolyzing the 3'-phosphate from 3',5'-bisphosphonucleotides. The enzyme will also sequentially hydrolyze 5'-phosphomononucleotides from 5'-phosphorylated RNA and DNA oligonucleotides, with no specificity towards the identity of the nucleotide base. The enzyme will not hydrolyze RNA or DNA oligonucleotides that are unphosphorylated at the 5'-end of the substrate but it makes no difference whether or not the 3'-end of the oligonucleotide is phosphorylated. These results are consistent with the sequential hydrolysis of 5'-phosphorylated mononucleotides from oligonucleotides in the 5' →3' direction. The catalytic efficiencies for hydrolysis of 3',5'-pAp, p(Ap)A, p(AP)4A, and p(dAp)4dA were determined to be 1.8 × 105 M-1 s-1, 9.0 × 104 M-1s-1, 4.6 × 104 M-1s-1 and 2.9 × 103 M-1 s-1 respectively. TrpH was found to be more efficient at hydrolyzing RNA oligonucleotides than DNA oligonucleotides. This enzyme can also hydrolyze annealed DNA duplexes, albeit at approximately 10-fold lower catalytic efficiency than the corresponding single-stranded oligonucleotides. TrpH is the first enzyme from E. coli that has been found to possess 5'→3' exoribonuclease activity. JOSEPH M. READY, I-1612, The University of Texas Southwestern Medical Center. CATALYTIC SYNTHESIS AND APPLICATION OF SUBSTITUTED YNOL ETHERS.. We discovered a method to access aryl ketenes through the coupling of tert-butoxy acetylene with aryl halides. This Pd-catalyzed reaction involves an aryl-ynol ether intermediate, which upon heating rearranges to the ketene. We have now found that tert-butoxy ynol ethers rearrange to ketenes, but adamantyl-ynol ethers do not. Thus, upon heating a mixture of the two ynol ethers, the ketene derived from the tert-butoxy ynol will react with the adamantyl ynol ether to form a cyclobutenone product containing two different substituents – i.e. a heterodimerization. Furthermore, these cyclobutenones will rearrange with further heating through an electrocyclic ring opening (4-pi)/electrocyclic ring closure (6-pi) to form naphthols and carbazoles. In detail, we have 1) Invented a Ni-catalyzed coupling of various ynol ethers with aryl halides. Compared to our previous method, this approach avoids isolation of reactive intermediates; 2) Discovered a method for hetero-[2+2] cycloadditions; and 3) Used the new cycloaddition towards the synthesis of a class of natural products called the dictyodendrins. When we use an iodo indole substrate for the Ni-catalyzed coupling/cycloaddition sequence, we form amino-carbazoles, which are the core structure of these natural products. In a second aspect of the chemistry of ynol ethers, we have developed [3+2] dipolar cycloadditions of ynols with azomethine ylides (Nˉ–N=C+). This reaction forms a new C-C bond, a new C-N bond, a new ring, and two new stereocenters. Moreover, the products, pyrazolidinones, display rigidity and polarity reminiscent of pharmaceuticals, and indeed several current drugs include this scaffold. We have discovered that lithium ynolates will react with azomethine ylides in high yield to form pyrazolidinones with diastereoselectivities around 10:1. Moreover, when an optically active azomethine ylide is used as the dipole, the cycloaddition proceeds with high stereocontrol. Removal of the chiral auxiliary generates the products in high enantiomeric purity. The reaction tolerates a wide range of aryl and alkyl substituents including electron withdrawing and releasing groups, heterocycles, protected alcohols and basic amines. X-ray crystallography has allowed us to assign the absolute and relative stereochemistry of the products. LINDA E. REICHL, F-1051, The University of Texas at Austin. RELAXATION PROCESSESS IN SMALL MOLECULES AND QUANTUM COHERENT SYSTEMS. We have computed the classical vibrational dynamics of the HOCl molecule for energies above the dissociation energy of the molecule. This dynamics determines the pathways for dissociation and recombination of the constituents of the molecule, but is not well understood because of the large number of degrees of freedom. Above dissociation, we find the classical dynamics is dominated by an Invariant Manifold that can stabilize two large stable periodic orbits at energies significantly above the dissociation energy. These periodic orbits emerge from a saddle-center bifurcation and are able to support significant quasibound states of the molecule.
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When matter, electromagnetic, or acoustic waves propagate through a spatially periodic medium, the allowed propagation energies form bands. For energies in band gaps, no wave propagation is possible. Our study of matter wave propagation in optical lattices, shows that the band structure is significantly influenced by the dynamics of the unit cell. As the unit cell dynamics becomes increasingly chaotic, the band structure changes and assumes behavior qualitatively similar to the "empty" BCC band structure observed in many BCC solids. This is a first indication that chaos in the unit cell of a periodic lattice can significantly influence the band structure of the lattice. PENGYU REN, F-1691, The University of Texas at Austin. MULTISCALE MODELING OF RNA 3D STRUCTURE. We have been developing a coarse-grained physical model for RNA, in which each nucleotide is represented by five pseudo-particles. This coarse-grained (CG) model is unique because 1) it explicitly incorporates electrostatic interactions and responds to ionic environment, 2) three particles are used to represent the base rings to accurately capture the base stacking and paring, 3) and it can be mapped to all-atom resolution with ease. Previously the parameters describing the particle interactions were mainly derived from PDB structural statistics. In the past year, we have further improved the CG potential by matching the experimental melting free energy of a large number of RNA duplexes. Excellent correlation between the CG model and experiment has been achieved for melting free energy (R2 > 0.7). The improvement has been implemented in the open-source modeling package TINKER so that other researchers can utilize it. We have also incorporated OpenMP based parallelization into MD simulations of RNA folding and are in process of integrating efficient conformational sampling algorithms such as the orthogonal space random walk. These improvements will allow the application of the CG model toward high-throughput prediction of RNA folding. Meanwhile, we continue to make progress in studying biomolecular interactions such as protein-protein and protein-ligand in general. We now have better understanding of the short-ranged charge penetration and polarization effect by using ab initio quantum mechanical methods to decompose the interactions between biomolecular fragments such as nucleotide bases. Such understanding will enable us to develop next-generation classical potential at both atomic and coarse-grained level for studying biomolecular structures and functions. PETER M. RENTZEPIS, A-1884, Texas A&M University. TIME AND SPACE RESOLVED CHEMICAL AND BIOLOGICAL REACTION INTERMEDIATES. A femtosecond laser system, was designed and constructed, capable of generating 50 femtosecond pulses in the 200 um ~ 1500 urn optical region and x-rays in the 1.3 keV to 10 keV range. This system was employed to study photon/ electron interaction, electron/phonon coupling and phonon to lattice energy transfer in single crystals. The pumping was provided a single 800 nm, 50 fs pulse and the time resolved x-ray diffraction was measured by single 50 fs,7,4 keV Cu Kα x-ray pulses. All processes were measured in real time, femtosecond time and sub-Angstrom space resolution. The electron/phonon interaction in Cu(III) single crystal was determined to occur within the pulse width of the laser pulse, 50 fs, while electron/phonon coupling time, including electron thermalization time was found to be 6 ps. We also observed and measured lattice contraction and expansion, "blast wave" propagation with the crystal bulk and observed in real time the melting phase transition as a function of atomic disorder with sub- Angstrom resolution. 2.Our biological studies revealed new and very important information on bacteria and other pathogens and resulted, to date, into three patents and four publications: In-situ identification of live and dead bacteria, by means of synchronous fluorescence. The importance of this research, in addition to its basic science value, is its use for the immediate and in-situ detection of bacteria in the emergency room and in the field. According to CDC over 74, 00 people dye per year from emergency room bacterial infections. Our method, to our knowledge is the only one that can detect and subsequently eliminate bacteria immediately in the emergency room and elsewhere. This is achieved by hand- held synchronous fluorescence spectrometer which we designed and patented. We developed a synergistic, two agents, AgNO3, and MB, system capable of killing as much as 2000 times more bacteria than the sum of these two agents reacting alone. Both items 2 and 3 have been considered for patents application. MICHAEL G. RICHMOND, B-1093, University of North Texas. SYNTHESIS AND REACTIVITY STUDIES OF POLYNUCLEAR CLUSTERS.
The hemilabile P,S-donors o-(diphenylphosphino)thioanisole (2-dppta) and o-(diphenylphosphino)thiotoluene (2-dpptt) have been investigated in ligand substitution reactions with different metal clusters. Treatment of [Os3(CO)10(NCMe)2] with these P,S-donors yields the corresponding ligand-bridged cluster 1,2-Os3(CO)10(2-dppta) and 1,2-Os3(CO)10(2-dpptt) as the kinetically controlled product below 273 K. The P,S-ligand quickly rearranges to furnish the chelating species 1,1-Os3(C0)10(PS). The solid-state structures of both P,S-chelated clusters have been established by X-ray crystallography. The kinetics for the ligand isomerization have been measured, and the activation parameters are consistent with an intramolecular process involving the migration of CO and the thiol groups about the cluster. A non-dissociative, multistep mechanism for the bridge-to-chelate isomerization of the PS-ligand in the two clusters has been verified by electronic structure calculations. The DFT calculations confirm the migratory preference of the thiol moiety over the phosphine moiety in these rearrangements. Thermolysis of 1,1-Os3(CO)10(2-dppta) leads to CO loss and regioselective ortho metalation of one of the aryl groups on the phosphine moiety, with the hydrido cluster HOs3(CO)94t2-1,2-S(Me)C6FIRPh(ri C6H4)] formed as the sole isolable product. The 2-dpptt-substituted derivative 1,1-Os3(CO)10(2-dpptt) undergoes loss of two CO ligands under identical conditions, followed by cleavage of the S-C bond to generate the benzyne-substituted cluster HOs3(CO)8(µ3-C6H3Me)[µ2-1,2-S(C6H4)PPh2)]. The kinetics and isotope effects on these and related ligand-activation reactions are currently under investigation.
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JEFFREY D. RIMER, E-1794, University of Houston. PHYSICOCHEMICAL FACTORS GOVERNING PROTEIN INHIBITION OF CALCIUM OXALATE MONOHYDRATE CRYSTALLIZATION. The past year of this project supported three graduate students and resulted in 6 published articles, two articles under revision, and one submitted manuscript. Research on calcium oxalate monohydrate (COM) crystallization has primarily focused on the identification of two organic acids that were found to exhibit unique modes of growth inhibition. Our findings revealed that these modifiers dissolve crystals at high supersaturation due to strain-induced binding to step sites on crystal surfaces. We collaborated with experts to perform DFT calculations to confirm the strain. Moreover, one of the compounds identified is an over-the-counter supplement. We partnered with a nephrologist to perform human trials and studies of COM growth in human urine and found that this new compound is more effective than the current treatment of human kidney stones. We submitted a manuscript that is now under revision in Nature. We extended this line of research to studies of β-hematin crystallization, which is a byproduct heme detoxification in malaria. We identified a biomimetic solution for hematin crystallization and have shown that different antimalarial drugs exhibit unique modes of binding to hematin crystals. The results of this study were submitted to Nature and the manuscript is currently being considered for publication. A major breakthrough in this Welch project was the design of a liquid AFM cell that permits time-resolved imaging of crystal growth under solvothermal conditions. Conventional AFM has been limited to low temperatures and short times. We have used this technique to explore the crystallization of a commercially relevant zeolite, SSZ-13 (this work was published in JACS). Our research on nonclassical crystallization also garnered two invited articles that were published in the last year. The first was a review article published in Science on "Particle-Mediate Crystallization". The second was a perspective article published in MRS Bulletin focused on the nucleation of open framework crystals. These projects are part of a broader initiative in our group to elucidate the growth mechanisms of zeolites, which predominantly grow by non-classical pathways. We published a Chem. Mater. Paper on this topic and the results of recent studies will be submitted for publication within the next year. JOSE RIZO-REY, I-1304, The University of Texas Southwestern Medical Center. NMR METHODS TO STUDY MEMBRANE PROTEINS IN LIPID BILAYERS. The extensive efforts that we have devoted to develop methods to study protein-protein interactions by nuclear magnetic resonance (NMR) spectroscopy have enabled us to determine the major binding mode in solution between the SNARE complex that forms the core of the neurotransmitter release machinery and synaptotagmin-1, the calcium sensor that triggers release, a goal that we have been pursuing for over fifteen years. The methodology that we used is based on the measurement of pseudocontact shifts caused by lanthanide ions attached to the SNARE complex on the NMR resonances of the synaptotagmin-1 C2 domains. Our data revealed a dynamic binding mode involving a highly basic region on the side of the synaptotagmin-1 C2B domain β-sandwich and a highly acidic region formed by syntaxin-1 and SNAP-25 on the surface of the SNARE complex. The effects of mutations in the basic region on disruption of synaptotagmin-1-SNARE complex binding correlate with the effects of the same mutations on impairment of synaptotagmin-1 function in neurons. The binding mode readily explains the finding that synaptotagmin-1 and complexins can binding simultaneously to the SNARE complex in solution but not on membranes and suggests a model whereby, upon calcium influx, simultaneous binding of synaptotagmin-1 to the synaptic vesicle and plasma membranes releases the inhibition of release caused by complexins and cooperates with the SNARE complex in bringing the two membrane together to induce membrane fusion. We also described the NMR structure in solution of the N-terminal domain of the mixed-lineage kinase domain-like protein MLKL and how a plug-release mechanism likely regulates its crucial function in necropotosis. We discussed our research in a review on the neurotransmitter release machinery. SEAN T. ROBERTS, F-1885, The University of Texas at Austin. MAPPING SINGLET EXCITON FISSION AND ENERGY TRANSPORT PATHWAYS IN PERYLENE DIIMIDE THIN FILMS AND CRYSTALS WITH FEMTOSECOND TIME-RESOLVED SPECTROSCOPY. SF is a process that occurs in organic thin films wherein a photoexcited spin-singlet excitation divides its energy to form a pair of lower energy spin-triplet excitons. The main objectives of our research work are to (1) characterize the electronic dynamics that govern SF in perylene diimide (PDI) thin films and (2) use SF to enhance energy collection by inorganic semiconductors used in photovoltaic cells. During this past year, we have made significant strides towards accomplishing both of these goals. First, we have prepared a series of polycrystalline thin films of PDIs with different chemical structures that systematically alter how these materials pack in the solid state. This allows us to control the degree of electronic coupling between PDI molecules and alter their SF rate by over an order of magnitude. Interestingly, we find that SF rates for many PDIs fall in the nanosecond range, roughly two to three orders of magnitude slower than that predicted by theory. While this is still fast enough to allow SF to efficiently compete with other singlet decay processes, it highlights the need for improved models to accurately describe SF. In addition, we have found that prior experimental studies that used transient absorption to follow electronic dynamics of PDI thin films have generally ignored contributions to the spectra from photoinduced heating, leading to spurious conclusions. We are preparing these results for submission to J. Phys. Chem. Lett. with an anticipated submission date of August 2016. We have also developed ESFG as a tool for probing the electronic structure of buried organic thin film interfaces. A report detailing this technique appeared in J. Phys. Chem. Lett. in February and we have used it to interrogate the interfacial structure of PDI films deposited on SiO2. We find that relaxation of crystalline strain at PDI film interfaces can shift the PDI singlet energy by as much as 200 meV! We are currently working to develop a time-resolved extension of this experiment to determine if triplet excitons experience a similar degree of interfacial relaxation as this will inform the choice of the semiconductor used to extract triplets from PDI films. Oral presentations acknowledging Welch Foundation support have been given by the PI at six international meetings and workshops.
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JON D. ROBERTUS, F-1225, The University of Texas at Austin. MECHANISM OF FOLATE-DEPENDENT METHYLATION. During the past year we were able to work out the molecular details of the mechanism of action of the cobalamin-independent methionine synthase. The cobalamin-independent methionine synthase enzyme catalyzes a challenging reaction; the direct transfer of a methyl from 5-methyl-tetrahydrofolate-glutamate3 (5-Me-THF-Glu3) to the L-homocysteine (Hcy) thiol. The enzyme has a dual (βα)8 TIM barrel structure that binds, activates and brings the reactants into reaction proximity by conformational movements. In the previously observed open structures the substrates bind too far apart to react, but we have captured a ternary complex with both substrates bound in a closed form of the enzyme. The closing is described in terms of a hinge between the N and C terminal TIM barrels, and a rearrangement of key loops within the C domain. The substrate specificity can now be rationalized and the structure reveals His707 as the acid that protonates the THF leaving group through a water molecule trapped in the closed active site. The substrates are correctly oriented for an in line attack by Hcy on the N5-methyl. GRIGORY ROGACHEV, A-1853, Texas A&M University. THE ORIGIN OF CHEMICAL ELEMENTS IN THE UNIVERSE. During this second year of the grant my group focused on two nuclear reactions that play a fundamental role in nuclear astrophysics. The first one is the 12C(α,γ) reaction. It is called the "holy grail" of nuclear astrophysics because of its paramount importance for stellar nucleosynthesis. It defines the oxygen/carbon abundance ratio in the Universe. The second is the 13C(α,n) reaction, which is the main source of neutrons for the slow neutron capture (s- process) that is responsible for half of all chemical elements beyond iron. The scientific outcome of the first year grant period is listed below: Powerful method for model independent determination of the α- asymptotic normalization coefficients for the near α-threshold states using the sub-Coulomb α-transfer reactions has been benchmarked using the known natural width of the 1- state at 5.79 MeV in 20Ne. It was shown that the method is accurate and model independent. This result paves the way for application of this method for the astrophysically important reactions. The uncertainties for the 12C(α,γ) reaction cross section at Gamow energy window (~300 keV) have been dramatically reduced by showing that the cascade transitions (transitions through the excited states of 16O) play only a minor role, contributing less than 4% to the total reaction cross section. This result is of major importance because it brings at a striking distance from reducing the uncertainty for this fundamental reaction to an astrophysically required 5% level, the goal that eluded us for 50+ years. The ANC of the 1/2+state at 6.356 MeV in 17O, which is dominating the 13C(α,n) reaction at 180 keV (Gamow energy for the AGB star nucleosynthesis), has been measured. Discrepancies between previous measurements have been resolved. The complete global A-matrix analysis is now in progress to provide the definitive constraint on the 13C(α,n) reaction rate that will be sufficiently accurate for stellar models. In addition to the results mentioned above my group started development of a new detector system, Texas Active Target (TexAT) that will allow us to perform unique experiments with rare isotope beams relevant for stellar nucleosynthesis. More details on this development will be provided in the next year Progress Report, after the successful commissioning of the detector system. DANIEL ROMO, A-1280, Texas A&M University. NOVEL STRATEGIES FOR BIOACTIVE NATURAL PRODUCT SYNTHESIS VIA β-LACTONE INTERMEDIATES AND NEW METHODOLOGY FOR ASYMMETRIC ALKYLATIONS. We developed further examples of a single-pot process for allylic carboxylation followed by bromolactonization of various simple allylbromides through reaction of derived allylzinc reagents with carbon dioxide leading to a single-pot route to β-lactones. We also developed a strategy for introduction of β- lactones into alkene-containing natural products via allylic bromination followed by the same single-pot process using carvone as a starting point. A flow reactor version of this process enabled high concentrations of dissolved CO2 in various solvents leading to improved yields for this overall process. β-Lactones were introduced into andrographolide and yohimbinic acid and these derivatives were tested against pathogenic bacteria and various cancer cell lines (collaborator: Prof. Stephan Sieber, TU MOnchen, Germany). Returning to a previous goal of our Welch project, we completed a 7-step total synthesis of the anticancer agent, hypercalin C, and this strategy will enable a SAR profile in collaboration with Asst. Prof. Joe Taube (Baylor Univ.). MICHAEL J. ROSE, F-1822, The University of Texas at Austin. IMPARTING PRECIOUS METAL PROPERTIES TO FIRST ROW TRANSITION METALS BY HEAVY ATOM LIGATION. Over the course of the last year, our research into the utility of first row metals for energy-related transformations has taken shape along multiple avenues: A) use of iron hydrogenase models for H2 activation and hydride transfer, B) the attachment of nickel complexes to semiconductors for H2 generation, C) the ligation of first row metals to heavy atom donors, and D) the C–H and B–F activation by cobalt oxo/peroxo complexes.
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A) In the application of iron to H2 catalysis, we have optimized synthetic conditions to isolate and characterize unique iron-hydride species derived from a bio-mimetic ligand set. These iron dicarbonyl species (supported by designed ligands) exhibit reactivity properties of a precious metal, owing to its rigorously low-spin Fe(lI) configuration. Such stability facilitates spectroscopic characterization and detection of otherwise short-lived intermediates, which are critical for understanding the proposed catalytic cycle of H2 activation and hydride transfer. B) Another major advance was the attachment of a nickel-phosphine complex to a silicon semiconductor for light-driven H2 generation. Previously, we had relied on expensive Pt for this purpose, so the improvement to using a molecular nickel species (1000× cheaper) is an important advance. We have also used a strategy of steric spacing to achieve the desired coverage of molecular species on planar, earth-abundant semiconductors (Si). C) Regarding the ligation of first row metals to heavy atom donors like antimony and bismuth (Sb, Bi), we have made substantial progress. We have prepared metal complexes of molybdenum and cobalt derived from tri-alkyl antimony (SbiPr3). Presently, their spectroscopic and magnetic properties are under investigation. We are also working to isolate the metal-stable tripod R(CH2Y(iPr)2)3 [R = CH3, Ph; Y = Sb, Bi] in order to fully stabilize transition metals for C–H activation catalysis. D) Lastly, building on our previous publication regarding the isolation of a cobalt-peroxo species, we have observed C–H activation and expanded the N4 donor set, observed C–H activation, and isolated a B–F bond activation product. All of these reports and discoveries are building a strong foundation of the PI's research program in inorganic chemistry. MICHAEL K. ROSEN, I-1544, The University of Texas Southwestern Medical Center. 2D PHASE SEPARATED PROTEIN POLYMERS: COMPOSITION, DYNAMICS AND LIPID INTERACTIONS. Research during this past year has shifted focus from the p-Nephrin/Nck/N-WASP system to a highly analogous system that utilizes identical types of modular protein interactions (SH2-phosphtyrosine, SH3-proline rich motif) to transmit signals in the immune system–pLAT/Grb2/SOS. This system will yield essentially identical general principles about the structure, function and regulation of membrane clusters, with the added advantage of ready translation to cellular experiments to test these principles in vivo. Work on both p-Nephrin/Nck/N-WASP and pLAT/Grb2/SOS will proceed in the future. We have shown that the pLAT/Grb2/SOS system forms clusters on supported lipid bilayers and determined the relative stoichiometries of the components. We can induce clustering by an upstream kinase cascade that phosphorylates LAT, and have reconstituted signaling downstream to actin regulatory proteins to produce membrane-bound actin filaments. These studies have revealed two important functional consequences of LAT clustering–protection of p-LAT from deactivation by phosphatases and enhancement of the specific activity of the molecules toward actin assembly at the membrane. DANIEL M. ROSENBAUM, I-1770, The University of Texas Southwestern Medical Center. STRUCTURAL STUDIES OF ACTIVE AND INACTIVE CONFORMATIONS OF G PROTEIN-COUPLED RECEPTORS. Over the past year of Welch Foundation support, my lab has made significant progress in our structural studies of GPCRs, and we used techniques derived from our GPCR work to make breakthroughs for other physiologically significant mammalian membrane proteins. Following on the previous year of Welch support, we used protein engineering and lipid-mediated crystallization to complete high-resolution structure determination of the human OX1, orexin receptor bound to dual-selective and subtype-selective antagonists. In addition, we carried out functional and computational studies to rationalize the binding selectivity of antagonists, and to uncover novel epitopes involved in neuropeptide recognition (published in NSMB). We have also made strides toward structure determination of the agonist(orexin)-bound active conformation of the OX2 orexin receptor. Using antibody engineering methods, we selected unique single-chain 'nanobodies' that bind the neuropeptide-occupied receptor. We are now screening these nanobodies to prove that they stabilize the active conformation, and we will follow up these experiments with large-scale LCP crystallization trials to obtain the first activated orexin receptor crystals. In addition to our studies on the orexin receptor, we obtained preliminary crystals of another physiologically significant neuropeptide receptor, and we applied an NMR labeling method published in the previous year to obtain quantitative dynamics information on several GPCRs bound to different ligands and effector proteins. We anticipate that these preliminary results will culminate in multiple high-impact publications during the remainder of this grant's funding period. Finally, we recently used methods that we previously developed for GPCRs to crystallize and solve the first atomic structure of a human sterol transporter, ABCG5/ABCG8 (published in Nature). JOSEPH H. ROSS, JR., A-1526, Texas A&M University. MAGNETISM AND ANHARMONIC LATTICE VIBRATIONS IN CLATHRATES AND RELATED MATERIALS. This year we provided a first report of physical properties of Ba-Co-Ge clathrates, showing from magnetization, transport, and specific heat that Co substitution in the chiral structure significantly reduces the electronic pseudogap, similar to role of pressure in arresting electronic changes, but with the structure transformations only modestly affected. Also in follow-up to work on BaCuGe clathrates, we used NMR with other techniques to identify the strongly nonlinear changes in electronic behavior across the composition range of Ba8Cu6Ge40-xSix. We also examined Yb, Ba, and In substituted CoSb3 cage-structured skutterudites. These have attracted great recent attention for thermoelectric behavior as well as other exotic phases such as topological insulators. In NMR studies we examined the local configuration of the substituents, identifying the Yb neighbor magnetic satellite as a measure of conduction electron hybridization with the rare earth, and also mapping the symmetry of the conduction bands away from the donor atoms. We also continued our work on Cu2Se-related phases, extending our work to effects of Ag substituents on the structure and Cu hopping/vibrational behavior in Cu2Se and Cu2Te. Our recently submitted work addresses the structure of the newly identified low-temperature phase, and demonstrates the impurity-band conduction characteristics due to disorder of static vacancies in this phase. Our work on magnetic-vibrational coupling in Ni-Mn-In Heusler-type materials continued, with a recent submission providing the first direct measure of the large vibrational contributions to the entropy change associated with the structure transformations. Follow-up crystallographic studies at a national lab are ongoing, as a probe of the corresponding structures.
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RICK RUSSELL, F-1563, The University of Texas at Austin. INVESTIGATION OF RNA MISFOLDING DURING TRANSCRIPTION. In the past year, we took advantage of our new understanding of the misfolded structure of the Tetrahymena ribozyme, gained over the last several years of this project, with two important papers that address how nature resolves misfolded RNAs. We found that an ATP-dependent RNA chaperone protein is able to unfold the misfolded Tetrahymena ribozyme structure, and with a series of mutations in the RNA we showed that the unfolding efficiency depends on the stability of the RNA. In this work we also showed that the RNA stability impacts the ability of the protein to engage productively with the RNA, as the rate of ATP hydrolysis also tracks with RNA stability. In the second publication we dissected the physical basis of this dependence by using single molecule fluorescence to show that the protein is unable to disrupt RNA tertiary structure and thus the dependence on global stability arises because the unfolding process is forced to start with spontaneous loss of RNA tertiary structure, which is faster for less stable RNAs. During this year we also extended our studies of nucleic acid folding to DNA, with a study of DNA junction dynamics that is currently in press at the Journal of Biological Chemistry. SANDRA L. SCHMID, I-1823, The University of Texas Southwestern Medical Center. CONFORMATIONAL DYNAMICS AND REGULATION OF DYNAMIN. This Welch Fellowship funded the work of a postdoctoral fellow, Dr. Saipraveen Srinivisan.. Dr. Srinivasan has completed and published his studies using hydrogen-deuterium exchange (in collabaoration with Pat Griffith and Venkat Dharmarajan at Scripps Florida) to identify long range conformational changes in dynamin in response to nucleotide and/or membrane binding (Srinivasan et al., EMBOJ, 2016). Importantly, we confirmed the existence of `open' and 'closed' states of dynamin based on large conformational changes of the membrane binding, pleckstrin homology domain (PHD) relative to the stalk that had been inferred from crystallography studies using site-specific fluorescence labeling and FRET-based assays. Using site-specific cysteine modification and crosslinking we tested the functional consequences of the different PHD conformational states and also showed that a human disease-causing point mutation dysregulates these conformational changes. In the past year we have also identified unexpected isoform-specific functions for dynamin-1 and dynamin-2 in regulating early stages of clathrin-mediated endocytosis (Reis et al., EMBOJ 2015). Dr. Srinivasan has been developing dynamin-1 and dynamin-2 knockout cells using CRISPR/cas9 for reconstitution experiments to dissect their isoform-specific functions. These findings and studies provide the basis for our successful competitive renewal of this grant. HANS A. SCHUESSLER, A-1546, Texas A&M University. OPTICAL STUDIES OF ULTRA COLD MOLECULAR IONS USING FEMTOSECOND AND XUV LASER RADIATION. We performed experiments on cooled molecules in ion traps. In ion trapping the quasi-equilibrium state of large mixed Coulomb crystals with over 103 ions is usually described based on an adiabatic approximation. We developed novel MD simulations which are more accurate and demonstrate this characterization method to determine the reaction-rate constant between slow acetonitrile molecules and sympathetically cooled Ne+ ions at a temperature lower than 10 K. The most fundamental candidates for precision spectroscopy are such systems as H2
+ and 4He+. For this purpose we store these ions in two separate ion traps. The used sympathetic cooling requires a similar charge-to-mass ratio of the coolant and cooled ion for reaching low temperatures. In this context we explored theoretically and experimentally the efficacy of Be+ and Mg+ as coolant ions to realize milli-Kelvin temperatures. At the same time we are developing a technique to shuffle single ions (one at a time) into the observation region. To take advantage of frequency comb lasers we also have initial results in tripling an infrared laser to the required UV wavelength for the two photon spectroscopy of H2
+. We experimentally reconstruct the laser-induced photo dissociation of H2
+ with laser pulses of central wavelength 800nm and duration of 50fs by employing a time-sliced 3D imaging technique (a measurement of all three momentum components). We have also explored impulsively aligned molecular systems for fragmentation (CO2, C2H2, CH3CN), high harmonic generation (HHG) (N2, CO2, C2H2, CH3CN) and ionization (N2, O2, CO2, CO, and C2H2). HHG was pressure optimized providing a tenfold improvement in the yield of XUV photons. MARLAN O. SCULLY, A-1261, Texas A&M University. QUANTUM COHERENCE EFFECTS IN CHEMICAL AND LASER PHYSICS. This past year, our group has made many discoveries and advancements as related to the foundations of quantum mechanics, novel applications of quantum coherence, development of new devices, etc Specifically, we: In a Physical Review Letters reference we showed that a collection of three-level atoms can form a tight-binding lattice in momentum space, called a superradiance lattice (SL). A SL can be extended to three (or more) dimensions where no analogous real space lattices exist, opening a door for exciting new physics. In another Physical Review Letters reference we also developed a superradiant metrology to achieve superresolving displacement measurement by encoding multiple light momenta into a three-level atomic ensemble, which dramatically increases sensitivity. In another Physical Review Letters reference we present a new quantum eraser experiment using randomly created photons from a thermal source. Experimental observations revealed a surprising nonlocal interference phenomenon. In a PNAS reference we experimentally demonstrated the single-shot remote identification of chemicals at kilometer-scale distances using random Raman lasing. This work was touted in Chemistry World, Nature, Science News, Scientific American, DieWelt, Sudduetsch, Spiegel, etc. In last year's report, we introduced the QASER. This past year, we further explored the implications of this exciting new discovery via analysis based on near-resonant QASER operation and on a multi-photon Hamiltonian obtained via a canonical transformation.
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The PI would like to thank the Robert A. Welch Foundation. He was recently named the C.N. Yang Visiting Professor by the Chinese University of Hong Kong and has been selected to present the inaugural P. Branch Distinguished Lecture at the University of Maryland. The Robert A. Welch Foundation goes a long way to make such accomplishments a reality. LAURA SEGATORI, C-1824, Rice University. PHYSICOCHEMICAL PROPERTIES OF NANOPARTICLES AT THE INTERFACE WITH BIOLOGICAL SYSTEMS. The research team continued investigating the impact of the physico-chemical properties of nanoparticles (NPs) on the autophagy system. Most nanoparticles (NPs) enter the cells through endocytosis and are found within endosomes and lysosomes. Subsequent routing to autophagosomes was observed for a range of NPs of different material and charge. Because the composition and surface chemistry of these NPs vary significantly, the nanoscale size seems to be the common denominator for accumulation into autophagosomes and induction of autophagy. The impact of NPs on downstream steps of the autophagy pathway, however, is likely to depend on other physicochemical properties, including material and charge. We investigated the impact of 2-hydroxypropyl-β-cyclodextrin (HPβCD) on the accumulation of autophagic cargo. We found HPβCD enhances the cellular autophagic clearance capacity, which results in reduced accumulation of protein aggregates (PLOS One. 2015). We also investigated the interface between cerium oxide NPs and the autophagy system. We focused on cerium oxide (a rare earth metal oxide with a cubic fluorite structure that contains ceria in two different oxidation states (cerium(III) and cerium(IV)) because of its interesting antioxidant properties. We tested a battery of ceria nanoparticles functionalized with different types of biocompatible coatings (N-acetylglucosamine, polyethylene glycol and polyvinylpyrrolidone) expected to have minimal effect on lysosomal integrity and function. We found that ceria nanoparticles function as autophagy activators and promote clearance of autophagic material (ACS Nano.). To further elucidate the impact of charge on markers of the autophagy systems, we also investigated the impact of polystyrene nanoparticles with positive, neutral, and negative surface charge on markers of autopahgy. Our preliminary data indicate that while all polystyrene nanoparticles activate the autophagic response, positively charged nanoparticles impair lysosomal function and block the autophagic flux. PHILIP SERWER, AQ-0764, The University of Texas Health Science Center at San Antonio. STRUCTURAL CHEMISTRY OF VIRUSES. Analysis of biological motors is limited by the following of their characteristics in some function-driving states: (1) obscurity caused by either short life or purification-instability and (2) structural dynamism caused by thermal motion. In a model study, we use phage genetics to reduce obscurity of incompletely packaged DNA (ipDNA)-containing capsids (ipDNA-capsids) generated by the phage T3 DNA packaging motor in vivo. The ipDNA had been cleaved from an external DNA segment. Some ipDNA-capsids have a Nycodenz-impermeability-caused low density during Nycodenz buoyant density centrifugation (NLD ipDNA-capsids) and, therefore, have unbroken shells. Native gel electrophoretic sieving, together with low density, reveals shell hyper-expansion for some NLD ipDNA-capsids. Electron microscopy (1) confirms hyper-expansion up to 2.2x, although conventionally sized ipDNA-capsids are also seen and (2) reveals that 3.0 mM magnesium ATP (physiological) contracts hyper-expanded ipDNA-capsids to a radius as small as 0.38x conventional radius. ADP has much less effect and reverses most ATP-induced contraction. DNase sensitivity reveals the left ipDNA end in the entry portal. These data confirm predictions of a hypothesis proposing a back-up (type 2) cycle driven by ATP-enhanced shell dynamism. JONATHAN L. SESSLER, F-1018, The University of Texas at Austin. MOLECULAR RECOGNITION VIA BASE-PAIRING. During this final funding period as a Welch Grant recipient (through Dec. 31, 2015) and since then as the Doherty-Welch Chair at The Univ. of Texas at Austin, emphasis was placed on the development of new self-assembled systems based on anion recognition. Manipulations in recognition were used to trigger association and decomplexation of aggregated ensembles. New and existing receptor systems were explored as part of this effort. Particular emphasis was placed on imidazolium macrocycles, expanded porphyrins, and modified calix[4]pyrroles. These anion binding subunits differ from one another in that they have, respectively, permanent cationic charge, a capability to become positively charged through protonation, and an ability to recognize anions through neutral NH-anion hydrogen bonding interactions. In the case of the expanded porphyrin systems, changes in the optical signature are seen. The report detailing these findings appeared in print early on in this funding period and was featured on the cover of the J. Am. Chem. Soc. A different approach to self-assembly involved the use of hydrazine linkages to create a catenated construct in water. Catenanes based on MOF structures involving calixpyrroles were also prepared during this funding period, as were new coordination frameworks built up from open chain oligopyrroles. A number of other supramolecular systems were also studied. LIBO SHAN, A-1795, Texas A&M University. BIOCHEMICAL AND REGULATORY CONSTRAINTS OF IMMUNE SENSORS. Proper control of immune-related gene expression is crucial for the host to launch an effective defense response. Perception of microbe-associated molecular patterns (MAMPs) induces rapid and profound transcriptional reprogramming via unclear mechanisms. Via genetic screens, we identified Arabidopsis RNA polymerase II C-terminal domain (CTD) phosphatase-like 3 (CPL3) as a negative regulator of immune gene expression. MAMP perception induced rapid and transient cyclin-dependent kinase C (CDKC)-mediated phosphorylation of Arabidopsis CTD. The CDKCs, which are in turn phosphorylated and activated by a canonical MAP kinase (MAPK) cascade. CPL3 directly dephosphorylated CTD to counteract MAPK-mediated CDKC regulation. In addition, we show that ASR3 (ARABIDOPSIS SH4-RELATED3), a plant-specific Trihelix transcription factor family, functions as a transcriptional repressor and plays a negative role in regulating pattern-triggered immunity (PTI). ASR3 possesses transcriptional repressor activity via its ERF-associated amphiphilic repression motifs and negatively regulates a large subset of PTI-induced genes. Phosphorylation of ASR3 by MPK4 enhances its DNA binding activity to
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suppress gene expression. Our studies provide evidence that ASR3 functions as a transcriptional repressor regulated by MAMP-activated MPK4 to fine-tune plant immune gene expression. BRYAN F. SHAW, AA-1854, Baylor University. ASPARAGINE DEAMIDATION IN MOTOR NEURONS: A MOLECULAR CLOCK OR A TICKING TIME BOMB. Summary: During the second year of this Welch award, we made a major breakthrough in our identification of properties of the SOD1 polypeptide that cause its toxicity in ALS. These findings were published in the Journal of the American Chemical Society and ACS Chemical Neuroscience. Also during 2016, my group's research received significant national and international press coverage including: PEOPLE Magazine (online and print); Upworthy; and ZDF News (Germany). This year, I was also invited to discuss our research on the Steve Harvey Show (T.V.) and before the U.S. House of Representatives (i.e., House subcommittee on Research and Technology). All of these items (including congressional testimony) can be found on our lab website: www.shawlaboratory.com. Our most significant accomplishment was the discovery of a biophysical predictor of lifespan in patients with SOD1-linked ALS. We have shown that the free energy of heterodimerization of mutant and WT SOD1 correlates linearly with the time of survival after the onset of ALS symptoms (J. Am. Chem. Soc. 138(16):5351-62). The co-expression of the WT SOD1 protein (along with ALS mutant SOD1) has been known for several years to be required for ALS pathogenesis in certain transgenic murine models of SOD1 that express mutant SOD1. In other models, the expression of the WT protein accelerates the onset and progression of ALS. The basis for this puzzling synergy between WT and mutant SOD1 toxicity remains unclear although it has been hypothesized that the WT protein might provide a template for prion-like conversion of mutant SOD1. The correlation we report suggests that the direct interaction between mutant and WT SOD1 is critical for disease progression. This correlation can also explain why certain "cryptic" mutations in SOD1‒mutations that do not affect protein stability or structure—result in more rapidly progressing forms of the disease compared to other mutations that do diminish stability and alter structure. We have also completely characterized the kinetic effects of ALS-linked SOD1 mutations on the fibrillization rate of SOD1. In the course of doing so we have optimized our fibrillization assays (i.e., found conditions that produce fibrils 10-fold faster than previous conditions). This work is laying the foundation for high throughput screens for compounds that inhibit the nucleation and propagation of fibrils originating from heterodimeric and homodimeric SOD1. JASON B. SHEAR, F-1331, The University of Texas at Austin. LASER-MEDIATED IMPRINTING OF BIOMATERIALS FOR REAL-TIME CONTROL OF CELLULAR ENVIRONMENTS. We have made substantial progress toward the goals of this grant in the first year of funding. A variety of protein pad compositions have been evaluated for the capacity to undergo laser-mediated imprinting, with effects of laser power, laser scan repetition number, and laser scan depth being examined. As a characteristic result, for example, we observed that BSA/gelatin hybrid pads scanned through their entire thickness with a focused titanium-sapphire laser beam undergoes ~30% decrease in thickness for one scan pass, ~45% total decrease for two scan passes, and negligible decrease for further scan passes. We have additionally examined changes in the Young's moduli for a range of protein pad compositions, and have found that depending on the conditions selected, we can either impose substantial increases in stiffness upon laser-mediated pad imprinting or avoid significant changes in stiffness. These fundamental results should be of particular value in studies of cells, such as those undergoing migration and/or differentiation, processes known to be affected by both topographical and elastic substrate cues. While continuing our systematic evaluation of fundamental points of control in laser-mediated imprinting, we have initiated studies to examine effects of in situ imprinting of grooves on the surface of protein-based pads on alignment and elongation of a cellular model, NIFH3T3 fibroblast cells, and have observed the ability to promote consistent and substantial changes in cell morphology that differ from responses of NIH3T3 cells plated on substrates already containing grooves. One paper is being prepared on this work with estimated submission July 2016. MATTHEW SHELDON, A-1886, Texas A&M University. HOT CARRIER UP-CONVERSION LUMINESCENCE IN NANOCRYSTAL HETEROSTRUCTURES. We have demonstrated controlled synthesis of chalcogenide NCs, with the ability to tune not only morphology, but also to create more sophisticated electronic level alignment, e.g. type I core/shell CdSe/CdS NCs, identified as ideal targets after recent theoretical analyses. Size-tunable Au deposition has also been demonstrated. Photoluminescence (PL) excitation spectroscopy indicates a 50% increase of UCL in core/shell NCs after Au deposition, suggesting hot electrons transfer from Au into the core CdSe quantum dot, where they radiatively emit with energy greater than the pump. This system serves as a promising NC platform for ongoing spectroscopic studies in the coming year. We have also begun exploring the use of cesium-based inorganic CsPbX (X = I, Br,Cl) perovskite NCs as a substrate for Au deposition. This is an especially intriguing material system due to the tunability of band-edge emission across the entire visible spectrum using straight-forward compositional modification during synthesis, as well as unusually high quantum yield over 90%, as prepared. We have also achieved well-controlled Au deposition on these NCs, with optical and structural characterization ongoing. Remarkably, the PL is more robust to metal deposition, in contrast with the dramatic loss of PL quantum yield observed for chalcogenide heterostructures, further suggesting advantages of perovskite NCs for our research aims.
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A. DEAN SHERRY, AT-0584, The University of Texas at Dallas. LANTHANIDE-BASED CEST AGENTS FOR MOLECULAR IMAGING. The long-term goal of this research is to develop a new class of paramagnetic lanthanide complex that acts as efficient paraCEST agents and to build platform technologies that will allow direct imaging of these various physiological parameters in vivo by MRI. The key to an efficient paraCEST agent is to either extend the lifetime of a bound water molecule in these complexes into the msec range or to identify other proton exchange sites in the paramagnetic complex that have inherently slower proton exchange kinetics. Over the past several years, we have learned how to slow the rate of water exchange in lanthanide complexes over six orders of magnitude and can now modulate the rate of water exchange to produce reliable MRI sensors. One of our main biological targets this year was to develop a technique that might allow direct imaging of lactate being produced by cancer cells. Conversion of excess glucose to lactate by cancer cells (the Warburg effect) is one of the hallmarks of cancer yet we have no simple way to quantify production of lactate by a tumor in vivo other than magnetic resonance spectroscopy (MRS). For this reason, we turned our attention to developing a simple CEST imaging method to image extracellular lactate produced by tumors using a standard clinical MRI scanner. The very small chemical shift difference between the lactate -OH proton resonance and water protons make CEST detection of lactate very challenging but we have discovered a relatively simple, direct way to alter the chemical shift of the lactate -OH proton resonance by addition of a paramagnetic shift reagent. Initial experiments show that this method allows CEST detection of extracellular lactate produced by cancer cells without interference from other endogenous biomolecules. XIAOBING SHI, G-1719, The University of Texas M. D. Anderson Cancer Center. MOLECULAR MECHANISMS OF JARID1B PHD FINGERS IN RECOGNITION OF HISTONE METHYLATION. We have previously reported the YEATS domain as a novel histone acetylation reader (Li. et al. Cell 2014). Recently, we found that the YEATS domain has an expanded acyl-lysine binding repertoire, with higher preference for crotonyl-lysine. Through collaboration, we have obtained crystal structures of AF9-YEATS in complex with crotonylated histone peptides. We have also biochemically characterized the AF9-crotonyl binding by several in vitro binding assays. We demonstrated that AF9 co-localizes with H3K18cr genome-wide and positively regulates gene expression in a YEATS-dependent manner. This work has been recently published (Mol. Cell, 2016). Considering the structural similarity between the acetyl group and the crotonyl group, we tested the binding affinity of four YEATS domain proteins (ENL, AF9, GAS41 and YEATS2) to modified histone H3K9 and H3K27 peptides by peptide pull down assays. We found that all YEATS domain proteins displayed a preference for the Kcr over Kac marks. Interestingly, the YEATS2 is the only YEATS protein that has a clear preference for the H3K27cr. The binding specificity of YEATS2 to H3K27cr is also obvious in the modified histone peptide array bearing 64 reported histone acylations. Through collaboration, we also obtained the complex structure of YEATS2 bound to H324-31K27cr peptide. Thus, our biochemical an structural data demonstrated that YEATS2 as a new histone crotonylation reader selective for H3K27cr. This work has recently been published in Cell Research, 2016. We have also obtained some preliminary biochemical and structural data showing that ENL YEATS domain also recognizes both acetylation and crotonylation of histone H3. We are currently working on the biological function of such a recognition in leukemia cells.
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CHIH-KANG SHIH, F-1672, The University of Texas at Austin. QUANTUM CONTROL OF LIGHT-MATTER INTERACTIONS IN METALLIC QUANTUM STRUCTURES. In this grant reporting period, our research work was focused on: Investigating how the surface roughness of metallic films influence the light emitting properties of semiconductor quantum dots. A paper is published in ACS Photonics. Detailed review of the current status of plasmonic nanolaser. The review paper is published in the Reports on Progress in Physics. Continue to investigate non-linear light generation using plamonic nanolaser. The investigation is near completion and we expect to submit a paper for publication within the next reporting period. Developing epitaxial Al as a plasmonic platform in the UV range. We have also completed work on probing the intrinsic optical constants of epitaxial thin Al films on Si(111). The work is now completed and a manuscript has been completed and ready for submission soon. In addition to these research activities directly relevant to the original research scope, the Welch supports further allow us to venture into other activities, in particular 2D materials beyond graphene, resulting in several publications, including one in Nano Letters and another one in Nature Communications. QIMIAO SI, C-1411, Rice University. THEORETICAL STUDIES OF ELECTRONIC DYNAMICS AND CORRELATIONS IN CARBON-BASED AND RELATED NANOSTRUCTURES. During this grant year, we made progresses on the following topics: Magnetic defects in graphene. The density of states of the conduction electrons in graphene is suppressed in a power-law way near the Fermi energy. We rigorously calculated the dynamical correlation functions of magnetic defects in such a host, particularly their dependences on frequency and temperature. One paper appears in PRB and one preprint is under review. Electronic dynamics and correlations in low dimensions. The topical two-dimensional materials motivated this direction. We initiated the study of theoretical models in two dimensions that are amenable to systematic theoretical studies, and identified novel phases with unusual magnetic properties pertinent to experiments. One paper appeared in PRL, and another is under review. Quantum criticality. Such correlation effects are characteristic of low-dimensional nanostructures. We studied several experimentally relevant systems, and determined their electronic properties in the quantum critical regime. Three papers were published, including one in Science. Superconductivity. As part of our work on the many-body electronic effects, which are key to the electronic properties of many low-dimensional structures, we completed several theoretical studies and collaborated with experimentalists to determine the unusual properties in several Fe-based superconductors. Six papers were published, including one in Nature Communications. DANIEL J. SIEGWART, I-1855, The University of Texas Southwestern Medical Center. SMART, LINEAR-DENDRITIC BLOCK COPOLYMERS TO INCREASE siRNA RELEASE IN RESPONSE TO pH. We succeeded in our synthetic attempts to synthesize a series of linear-dendritic copolymers. These "smart" copolymers were found to be pH-responsive. We completed pH titrations and determined the pKa transition of the polymers, where the pKa strongly correlated to the structure. The resulting copolymers possess a very low critical micelle concentration. They are therefore highly stable materials for drug and gene delivery with the promise to release drugs in response to small changes in pH. This result is highly relevant for studies on cancer and other diseases. We also anticipate utility in understanding the fundamental mechanism of intracellular release. In years two and three of the grant, we will publish the synthetic description of the new copolymers. We will also focus on 1) completing the synthesis and characterization of an expanded array of linear-dendritic block copolymers, 2) siRNA binding studies, 3) siRNA delivery studies, 4) examining the cytoplasmic release of siRNA, and 5) elucidation of the fundamental intracellular delivery mechanism. As a direct outcome of these studies, we have used the specific reaction methodology and/or core knowledge from this funded grant to publish nine articles, with two more currently under external review. ALEXEI V. SOKOLOV, A-1547, Texas A&M University. APPLICATIONS OF MOLECULAR COHERENCE IN ULTRAFAST OPTICS. We generate coherent Raman sidebands by crossing two femtosecond laser pulses in a Raman-active crystal, and control spectral phases of the resultant broadband light in a precise and stable manner. The sidebands and the driving pulses are refocused back to the same crystal, in a reflection scheme that utilizes movable spherical minors, and a nonlinear spectral interferogram is produced. Spectral phases are obtained from the recorded interferogram using a numerical simulation, thus enabling retrieval of the pulsed waveform. Furthermore, by using a deformable mirror to adjust the phases, we demonstrate that our setup is capable of synthesizing controlled ultrafast waveforms. In addition, we explore the role of spatial profile shaping in nonlinear interactions of ultrafast laser beams. We investigate coherent transfer of orbital angular momentum in a PbWO4 crystal by using two time-delayed linearly chirped pump pulses. In another set of experiments, we study applications of coherent Raman scattering to microspectroscopy of chemicals, and to ultrafast nanoscopy. We describe a technique, based on plasmonic nanostructure-enhanced coherent molecular spectroscopy that may be used to explore ultrafast energy and electron transfer dynamics with nanometer spatial resolution. Finally, we investigate the origin of complex line shapes that we have discovered in surface-enhanced coherent Raman spectroscopy, and propose a model based on plasmonic phase effects and quantum chemistry calculations. Observation and measurement of these line shapes can be used as a tool in nanoscale sensing and spectroscopy.
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DONG HEE SON, A-1639, Texas A&M University. DARK EXCITON IN THE ENERGY TRANSFER PROCESS OF SEMICONDUCTOR NANOCRYSTALS. In this project year, we investigated the competitive dynamics of exciton relaxation and exciton-dopant energy transfer processes influenced by the temperature, which modifies the energetics of the competing processes. Specifically, temperature dependence of the exciton and luminescence intensities in Mn-doped CdS/ZnS quantum dots (QDs) emitting both exciton and dopant luminescence simultaneously was studied in the temperature range of 77–320 K. With increasing temperature, exciton luminescence intensity decreased as a result of the increased charge carrier trapping, similar to the usual undoped QDs. In contrast, the sensitized Mn luminescence intensity increased with increasing temperature despite the decrease in the exciton population available for the sensitization. The observed opposite temperature dependence of the exciton and Mn luminescence indicates that the exciton–Mn energy transfer rate should increase with temperature significantly more rapidly than the charge carrier trapping. Temperature shift of the bandgap of the host QD and the energy of accepting d–d transition, resulting in the variation of the donor–acceptor spectral overlap, is considered responsible for the large temperature dependence of the energy transfer rate in Mn-doped QDs. The result of this research provides clear evidence that the variation of the temperature in doped semiconductor quantum dots can modify the spectral overlap of the donor and acceptor transitions significantly to the extent that the branching ratios of the competing dynamics processes are greatly altered. Such observation may also find useful application in optical temperature sensing. ZHOU SONGYANG, Q-1673, Baylor College of Medicine. NOVEL ACTIVITY OF THE TELOMERE REGULATOR TIN2 IN THE MITOCHONDRIA. Of the telomerase core subunits, the RNA template TERC/TR appears abundantly and ubiquitously expressed in human cells; however, the expression of the reverse transcriptase TERT is tightly regulated. For example, TERT appears low or undetectable in most somatic cells, but expressed highly in proliferative tissues and stem cells. While many human cancers exploit the telomerase by up-regulating TERT expression and telomerase activity, in 10~15% cancers, telomeres can also be extended via a homologous recombination-based pathway termed Alternative Lengthening of Telomeres (ALT). Genomic studies using cancer cells from differentiated pancreatic neuroendocrine tumors and pediatric glioblastoma have revealed strong correlation between the ALT phenotype and mutations in DAXX, ATRX, and histone H3.3, indicating a possible role for these proteins in repressing the ALT pathway. We compiled a list of naturally occurring DAXX mutant alleles that have been found in human cancers, and noted that DAXX mutations have been identified in both ALT and telomerase positive cancers. We have gone on to show that endogenous DAXX can localize to Cajal bodies, associate with the telomerase complex and facilitate telomerase assembly and targeting to telomeres. Furthermore, these activities of DAXX are differentially disrupted by disease mutations located in different regions of the DAXX protein. Inhibition of DAXX by RNAi led to reduced telomerase targeting to telomeres as well as telomere shortening. These findings have revealed a novel function of DAXX in telomerase-positive cells, and suggest that DAXX dysfunction may forestall telomerase-dependent telomere maintenance. This work was published in JCS. The structural maintenance of chromosomes hinge domain–containing protein 1 (SMCHD1) contains a GHKL (Gyrases, Hsp90, histidine kinase, and MutL) domain. Originally identified as an epigenetic modifier, it was later shown to localize to the inactive X chromosome and play a critical role in controlling CpG island methylation associated with X chromosome inactivation. Recent studies of human SMCHD1 as well as the Arabidopsis thaliana SMCHD1 homologue GMI1 found recruitment of SMCHD1 to laser micro-irradiated damage sites along with DNA repair factors such as Ku70 and RAD51, suggesting an important role for SMCHD1 in double strand break (DSB) repair. Of the different types of DNA damage, DNA double strand breaks (DSBs) are considered the most detrimental, because unrepaired DSBs will lead to genome changes such as chromosomal deletion, inversion, and translocation, and ultimately growth arrest and cell death. Using Hela cells individually knocked out (KO) for SMCHD1, 53BP1, and BRCA1 that were generated with the CRISPR/Cas9 technology, we found that the localization of human SMCHD1 to DNA DSB lesions was regulated by 53BP1 but not BRCA1. Upon DSB induction, formation of 53BP1 foci, not BRCA1 foci, was defective in SMCHD 1 KO cells, indicating dysregulated DNA damage response and repair in these cells. Furthermore, RNAi depletion of SMCHD1 decreased non-homologous end joining (NHEJ) but enhanced homologous recombination (HR) mediated DSB repair. Our data place SMCHD1 downstream of yH2AX foci formation, where it contributes to the adoption of DSB repair mechanisms (NHEJ vs. HR), adding further evidence to the complex nature of DNA damage response and repair pathways. Interestingly, SMCHD 1 has also been reported to be enriched at long telomeres, suggesting possible function in global chromatin structure maintenance in addition to X chromosome inactivation. In fact, telomeres are naturally occurring DSBs, and require the protection and capping by a network of factors. Our study highlights the novel function of a factor that may also participate in telomere maintenance. This work was reported in JBC. JOHN F. STANTON, F-1283, The University of Texas at Austin. STUDIES IN QUANTUM CHEMISTRY. Welch-supported research during the 2015-2016 funding period was carried out in many areas, ranging from fundamental investigations of molecular structure (that were, necessarily, carried out with the collaboration of experimental spectroscopists), molecular dynamics, fairly esoteric areas of atomic and molecular physics, molecular spectroscopy, and quantum chemical method development. We are particularly proud of our implementation of the so-called coupled cluster singles, doubles, triples and quadruples (CCSDTQ) method, which was articulated as one of the most important research goals of our Welch research in the last proposal. Together with its approximation known as CCSDT(Q), this method, which offers nearly quantitative solutions of the electronic Schroedinger equation for many (arguably most) molecules in the vicinity of their lowest-energy geometry, will eventually become the de facto standard for accurate calculations. The reason that it does not yet enjoy this status is simply due to computational cost. While exploitation of "Moore's Law"
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(advances in computer technology) will make the method more accessible, algorithmic improvements have sorely been needed. Our work that was published in late 2015 does much to address the latter; we have achieved speedups of roughly five to a hundredfold relative to existing implementations. In terms of applications of theory, we have worked on studies of several molecules that have received significant attention in recent years. For example, the so-called Criegee intermediate (H2COO) - believed to play an important role in organic chemistry and also to mediate climate effects through interactions with atmospheric aerosols - has been studied, particularly a process by which this curious species might be generated in the vicinity of lightning strikes. Other work has focused on carbenes - a class of molecules important to organic chemistry - and detailed "inner shell" processes in small molecules. MIHAELA C. STEFAN, AT-1740, The University of Texas at Dallas. POLYTHIOPHENE BLOCK COPOLYMERS: A SYSTEMATIC INVESTIGATION OF MORPHOLOGY – OPTOELECTRONIC PROPERTIES DEPENDENCE. During the 5th year of this proposal we have synthesized a novel liquid crystalline semiconducting block copolymer containing semiconducting polythiophene and a thermothropic methacrylate. An azobenzene liquid crystalline mesogen, 6-(4-((4-methoxyphenyl)diazenyl)phenoxy)hexyl methacrylate (MMAZO) was incorporated into a block copolymer with semiconducting poly(3-hexylthiophene) (P3HT). The synthesis was performed by a combination of Grignard metathesis (GRIM) and atom transfer radical polymerization (ATRP) techniques. The composition of synthesized copolymers was determined from 1HNMR analysis. The P3HT block/random copolymers containing thermotropic liquid crystalline segments were expected to bring unique self-assembly and opto-electronic properties. The field-effect mobilities of the synthesized P3HT copolymers were measured in organic thin film transistors (OTFT). The surface morphology of the P3HT copolymer films upon annealing was investigated by tapping mode atomic force microscopy (TMAFM). The transition of liquid crystalline mesophase in response to the temperature for the P3HT copolymers was investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Relatively high hole mobilities were measured for the synthesized block copolymers even at a low content of semiconducting P3HT block (25.9 – 50.5 mol-% P3HT). These relatively high mobilities can be explained by the assembly of a the P3HT block into highly ordered crystalline domains upon crystallization from the liquid crystalline mesophase of PMMAZO which most likely generated densely packed, well aligned nanofibrils of P3HT. This assured the formation of extended carrier transport pathways in phase-separated block copolymers despite the second block being insulating, leading to remarkable electronic properties in OFET devices with favorable structural morphology in thin films especially on the surface treated devices. KEITH J. STEVENSON, F-1529, The University of Texas at Austin. SYNTHESIS OF MESOPOROUS CARBON AND METAL OXIDE ARCHITECTURES.
Over this grant period we have continued to explore for preparing nanostructured and mesoporous carbons, metal oxides such as LaNiO3 and La1‒xSrxCoO3‒δ perovskites for electrocatalysis (work in collaboration with Prof Keith P. Johnston). Specifically, we have investigated the oxidation of urea as a benign fuel source to use N2 and CO2 as carriers for hydrogen fuel. We have also studied the use of the complex cobalt-based perovskite mentioned above as an electrocatalyst for the efficient oxidation of water to dioxygen. This material exhibited far more efficient transformation than several well-known base-metal or precious-metal oxide catalysts, thus providing a new benchmark for earth-abundant water-oxidation. Relatedly, we also investigated the other half-reaction (proton reduction to hydrogen) by using a new, ionic-liquid based deposition of MoSx onto silicon photoelectrodes. This procedure prevents the formation of deleterious oxides (from aqueous deposition) and provides efficient solar→H2 conversion (~0.5%). Ongoing work seeks to expand this project to other metal chalcogenides such as WS2, MoSe2 and WSe2 for hydrogen evolution. In examining the effect of lithium ions on TiO2 anode performance, we discovered and reported the unique counterion dependence (LiPF6) that has implications for next-generation battery technology. We have developed the new tool of a transparent ultra-microelectrodes (UME) to study intermediates in the formation and degradation of reactive oxygen species at working electrodes. Lastly, we have studied and reported on single-molecule modification and imaging on graphene substrates by STM microscopy, which serves as an excellent jumping off point towards understanding single-molecule charge-transfer events and molecular electronics applications. WU-PEI SU, E-1070, University of Houston. DIRECT PHASING IN MACROMOLECULAR CRYSTALLOGRAPHY. We have proposed a new iterative transform method to solve the X-ray phase problem for protein crystals. It is based on the fact that the electron density is constant in the solvent region. Starting from random phases, the algorithm may generate the correct phases after tens of thousands of iterations of Fourier transform using only the diffraction data of a native crystal. The success has been demonstrated for several crystals with high solvent content. Some of them are very large proteins such as the photosynthetic reaction center. As the solvent content approaches 50%, however, the method becomes less effective and a convergent solution may not be reached within a reasonable amount of computer time. Before solving this problem in a fundamental way, we have explored our method as an improved molecular replacement method. The conventional molecular replacement method sometimes runs into problem due to insufficient structural similarity between the template and target proteins. The template must normally represent a large fraction (usually more than 50%) of the structure and have a core whose atomic coordinates are superimposable within approximately 1-2 Angstroms root mean square deviation of the target structure. By starting with a template structure instead of a random structure, our method seems to work for several structures which defy a solution within the conventional molecular replacement method. Compared to some alternate methods which usually are very expensive and computer intensive as they involve quantum chemical force field calculations, our enhanced molecular replacement calculations can be carried out on a laptop.
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JEFFREY J. TABOR, C-1856, Rice University. CHARACTERIZING THE LIGAND BINDING PROPERTIES OF BACTERIAL SENSOR HISTIDINE KINASES FROM THE HUMAN GUT. Our Welch-supported research project has been very successful this year. First, we have successfully expressed a TCS (BAD_0569/8) from a bacterium enriched in the obese gut (Bifidobacterium adolescentis) in E. coli and screened it against more than 50 metabolites enriched in the obese gut to identify that it is activated by L-methionine, which is an obesity biomarker. We have also characterized a poorly understood family of carbohydrate sensing TCSs (hybrid TCSs, or HTCSs) from Bacteroidetes bacteria that are also enriched in obese gut environments in E. coli, which has never been demonstrated before. We developed a new method to identify the output promoters regulated by HTCSs by expressing the DNA binding domain of the HTCS in E. coli and expressing candidate promoters from Bacteroidetes upstream of GFP. We used this method to show, for the first time that the response of the HTCS BT_1754 to fructose is exceptionally sharp (i.e. has a high Hill coefficient). Such a measurement has never been made before, and suggests a possible reason for the unique evolutionary architecture of HTCSs. We are exploring the origins of this phenomenon and whether it is present in other HTCSs. We are currently performing more rigorous investigations of BAD_0569/8 sensing, and applying the results above to characterize the input ligands sensed by other TCSs, and HTCSs enriched in the obese gut. This work will continue to bring us toward our ultimate goals of understanding the biochemistry of these interactions, understanding host microbe chemical signaling in the gut, and developing new diagnostics and therapeutics for obesity. UTTAM K. TAMBAR, I-1748, The University of Texas Southwestern Medical Center. STEREOSELECTIVE ALLYLIC FUNCTIONALIZATION OF OLEFINS.
Based on our initial proposal, we developed a general method for functionalizing terminal olefins with aromatic, aliphatic, and vinyl Grignard reagents. In a one-pot process, olefins react with a sulfurdiimide reagent to generate allylic sulfinamides, which undergo selective copper-catalyzed allylic alkylation with Grignard reagents. Allylic alkylation products are formed with high regioselectivity and E-selectivity. We have also developed conditions for the control of regioselectivity in the generation of either liner or branched allylic alkylation products. By changing the copper source, solvent, and temperature of the catalytic allylic alkylation step, we can now selectively generate the branched products. We have utilized the sulfurdiimide reagent to selectively functionalize 1,3-dienes via a [4+2] cycloaddition to generate cyclic sulfinamides. These intermediates are treated with a copper catalyst and aryl Grignard reagents to generate 1,4-aminoarylation products with three new functional groups (an aryl ring, a sulfonamide, and a Z-olefin). We have also developed an aminothiolation of 1,3-dienes in the presence of alkyl Grignard reagents. We surmise that the divergent reactivity of aryl and alkyl Grignard reagents is due to the formation of a [10-S-4] sulfurane intermediate in the presence of alkyl Grignard reagents. These results represent a general platform for the selective functionalization of many classes of unsaturated hydrocarbons. YIZHI JANE TAO, C-1565, Rice University. CATALYTIC MECHANISM OF ASTROVIRUS RNA REPLICATION. Human astrovirus (HAstV) is a leading cause of viral diarrhea in infants and young children. It is also associated with other serious presentations such as nephritis, hepatitis, and encephalitis, although little is known about the mechanistic basis of the disease. The capsid protein (CP) of HAstV is synthesized as a 90 kDa precursor (VP90) that can be divided into three domains: a highly conserved N-terminal domain, a hypervariable domain, and a highly acidic C-terminal domain. Maturation of the HAstV requires proteolytic processing of the astrovirus CP at both inside and outside of the host cell. As a consequence, infectious virion of the astrovirus contains three predominant protein species with molecular weights of approximately 34 (VP34), 27/29 (VP27/29), and 25/26 (VP25/26) kD, respectively. Despite the biomedical significance of HAstV, difficulties with in vitro cell culture and recombinant capsid production pose serious challenges to detailed structural characterization. In this grant year, we have determined the crystal structure of the HAstV shell fragment (i.e. aa71-415), which is derived from the highly conserved N-terminal region of VP90. HAstV-shell exists as a monomer and each molecule contains two domains: an S domain which adopts the typical jelly-roll n-barrel fold and a P1 domain which has the appearance of a squashed β-barrel consisting of six anti-parallel β-strands. Mapping proteolytic cleavage sites for capsid maturation shows that Arg394 and Ala314 are situated in two highly flexible loop regions exposed on the capsid surface. Further capsid assembly studies using recombinant proteins and negatively staining electron microscopy demonstrated that both fill-length VP90 (aal -782) and VP70 (aal -647) can form virus-like particles (VLPs), suggesting that the acidic domain is dispensable for capsid formation. Our high resolution crystal structure of the HAstV-shell has substantially enhanced our understanding of the HAstV capsid assembly/maturation process and has yielded testable hypotheses as to how virus infectivity is acquired through the proteolytic processing of the capsid. Our work will also have important application in the development of astrovirus vaccines using stabilized capsids. THOMAS S. TEETS, E-1887, University of Houston. FINE TUNING OF MOLECULAR CATALYSTS AND PHOTOSENSITIZERS VIA SYNTHETIC ALLOSTERY. Heteroleptic bis-cyclometalated iridium(III) with β-ketoiminate (acNac) and β-diketinninate (NacNac) ancillary ligands have been disclosed. These ligands are popular in small-molecule activation and catalysis, and work from our group shows their potential value in designing new generations of molecular chromophores. Complexes with these ancillary ligands are potent excited-state reductants, brought on by destabilization of the HOMO through d-n- interactions with the ancillary ligand. When the NacNac ligands are fluorinated in the backbone, new low-energy NacNac-centered excited states are introduced, which give rise to luminescence in the red and near-infrared regions. In the opposite extreme, bis-cyclometalated iridium(III) complexes with strong-field aryl isocyanide ancillary ligands have been developed. These complexes exhibit pronounced redox stability while retaining efficient, color-tunable phosphorescence. Triaryl formazanate ligands, structurally related to NacNac, have also been explored, and cyclometalated platinum(II) complexes of these chromophoric ligands exhibit panchromatic absorption and ligand-based redox activity.
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In addition to these conventional ligand design approaches, the PI's group utilizes secondary-coordination-sphere Lewis acid-base interactions to control the excited-state properties of chromophores. This approach has been applied to pyridine-decorated platinum-diimine complexes; interaction with triarylboranes perturbs the excited states of these complexes. The direction of the excited-state perturbation depends on the site of Lewis acid binding, and the magnitude of the perturbation depends on the strength of the Lewis acid and the number of equivalents bound. This synthetically facile strategy offers numerous layers of fine control over the excited-state properties and will be further developed on other platforms. JONATHAN R. TERMAN, I-1749, The University of Texas Southwestern Medical Center. CHEMISTRY AND ENZYMOLOGY OF MICAL FAMILY OXIDOREDUCTASES. The chemical modification of specific amino acid residues is a critical means to alter the biological activity of proteins. Post-translational modifications such as the kinase-mediated phosphorylation of amino acids alter the activity of specific proteins in a reversible manner. Recently, the oxidation of specific amino acids has also become appreciated as another key mechanism in which to modify protein function – but the enzymes that mediate these oxidation-reduction (Redox) reactions are poorly defined. Interestingly, we have identified a novel family of proteins, the MICALs, whose members are similar at the amino acid level to Redox enzymes. Our investigations of these proteins over the past few years with the support of the Welch Foundation has revealed (as described by others) a "...completely new mechanism" and ". . . adds to the list of posttranslational modifications that effect the regulation of cellular behavior". Our work using Welch Foundation support also reveals that this new mechanism is reversible - and this is accomplished by a family of enzymes called MsrBs (also called SeIRs). Specifically, our work reveals that MICAL stereo-specifically oxidizes a polymerized form of the cellular protein actin to generate actin Met-44-R-sulfoxide and MsrB/SeIR reverses these effects both in vitro and in vivo. Our work is thus the first to discover that the interconversion of specific Met/Met(R)O residues is a precise means to control protein function, identifying a novel reversible post-translational modification and redox regulatory system. Now, over the past year, we find that MICAL synergizes with another protein called cofilin to exert its effects. Strikingly, this synergy is Redox-dependent - in that MICAL oxidizes polymerized actin, which then recruits cofilin, and together their combined effect accelerates both proteins action by over an order of magnitude. These results identify a new type of biochemical synergy underlying biology. ISABELL THOMANN, C-1825, Rice University. ANVANCED FEMTOSECOND OPTICAL IN SITU PROBES FOR PHOTOCATALYSIS.
We synthesized Au/MoS2 nanoparticle hybrid samples, and started investigating these samples suspended in solution by transient absorption spectroscopy. The density and path length for particles in solution are experimental parameters that can be easily controlled which is advantageous for extending initial transient absorption measurements to femtosecond stimulated Raman spectroscopy measurements in the future. In one of our samples we study plasmon-induced hot carrier generation in Au/MoS2 hybrid nanostructures. MoS2 is known for its photocatalytic properties and Au nanostructures are known for their strong optical absorption. Therefore, we utilized Au/MoS2 hybrid nanostructures as antenna/catalyst systems to study the process of hot carrier generation. Our preliminary ultrafast transient absorption measurements show that in some of our samples, there is an anomalous ultrafast damping spike with a decay time of less than 100 fs. The difficulty of the transient absorption experiments lies in the heterogeneity of the Au/MoS2 hybrid nanostructures and batch-to-batch variations. We aim to correlate transient absorption measurements with transmission electron microscopy and photo-induced force microscopy, to develop a clear picture of the sample morphology and electromagnetic field enhancements that should result in a large number of energetic hot carriers.
We have conceived, simulated, fabricated/synthesized several photoelectrodes that can be used for water spitting (see the three publications listed below). We find that it may be easier to first collect transient absorption and femtosecond stimulated Raman spectroscopy (FSRS) data on particles suspended in solution instead of on photoelectrodes that we were initially designing for your FSRS experiements. RANDOLPH P. THUMMEL, E-0621, University of Houston. 6-5 CHELATORS: A NEW PARADIGM IN POLYDYRIDINE CHEMISTRY. A series of Ru(II) complexes were prepared involving a tetradentate equatorial ligand and two 4-substituted pyridines as the axial ligands. All the complexes showed activity towards water oxidation. Investigation of their catalytic behavior and electrochemical properties suggests that they may follow the same catalytic pathway as the prototype [Ru(dpp)pic2]2+ involving a seven-coordinated [Ru(IV)O] intermediate (dpp = di-(2-pyridyl)- 1,10-phenanthroline, pic = 4-methylpyridine). A series of tetradentate ligands related to ppq (ppq = 8-(1",10"-phenanthrol-2"-yl)-2-(pyrid-2'-yl)quinoline) have been synthesized. Co(II) complexes were prepared from these ligands and characterized by UV-vis and mass spectroscopy, cyclic voltammetry, and X-ray analysis. The light-driven H2-evolving activity of these Co complexes was evaluated under homogeneous aqueous conditions. Cyclic voltammograms showed a significant catalytic current for H2 production in both aqueous buffer and H2O/DMF medium. A combined experimental and theoretical study suggests a formal Co(II)-hydride species as a key intermediate that triggers H2 generation. We have discovered that FeC13 reacts with ppq to provide a µ-oxo-bridged dimer that is quite stable in aqueous solution and in the presence of Ce(IV) as a sacrificial oxidant produces oxygen at a very fast rate. We continue our fruitful collaborations with the group of Etsuko Fujita at Brookhaven National Laboratory and Jacek Waluk at the Polish Academy of Sciences.
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CHIN-SEN TING, E-1146, University of Houston. STUDY OF SUPERCONDUCTIVITY AND RELATED SUBJECTS IN STRONGLY CORRELATED ELECTRON SYSTEMS. Considering the coexistence of the 2×1 colinear spin-density-wave (SDW) and superconductivity (SC) with the S± pairing symmetry in iron-pnictide superconductors like BaFe2-xCoxAs2 CaFe2-xCoxAs2 and Ba1-xKxFe2As2, we developed an improved two orbital-model which breaks the symmetry of the tetragonal point group by lowering it from C4 to D2d for the purpose to compare with the angular resolved photoemission experiments. It properly describes the electronic structures of both electron and hole doped compounds. In order to compare with the experiments we performed a comprehensive investigation of the evolution of the Fermi surface (FS) topology in the presence of the SDW order as the doping is changed. Based on this model, the pairing symmetries in heavily electron doped BaFe2-xCoxAs2 and KyFe2Se2 have been studied. We find a unified description of the evolution from s±-wave pairing (2.0 <n<2.4) to d-wave pairing (2.4 <n<2.5) as a function of electron filling with n=2+x and x=y/2. In the crossover region a novel time-reversal symmetry breaking state with s±+ id pairing symmetry emerges. A real-space study further shows that when the impurity scattering effects of Co dopants are taken into account in BaFe2-xCoAs2, the superconductivity is completely suppressed for n > 2.4. This preempts any observation of d-wave pairing in this compound, in contrast to KyFe2Se2. We also examined the phase diagram of the phosphorous (P)-doped BaFe2(As1-xP)2 compound as a function of x by using the lattice Bogoliubov-de-Genes equations, and the magnetic ground state of superconducting Eu(Fe1-xIrx)2As2 (x = 0.12) by the first principle calculations. These results are compared successfully with experiments. In addition, we studied several related subjects, such as the possible Z2 topological order in FeSe based superconductors, the effect of nearest neighboring Coulomb interactions on the spin-polarized-current order in bilayer graphene, and the interaction driven quantum phase transition in systems with fractional quantum Hall effect. FRANK K. TITTEL, C-0586, Rice University. APPLICATION OF MID-INFRARED QUANTUM CASCADE AND DIODE LASERS TO HIGH-PRECISION ATMOSPHERIC TRACE GAS MONITORING. During this grant year we concentrated our efforts on three projects that involve QCL based sensor systems suitable for high precision atmospheric trace gas monitoring. Simultaneous atmospheric nitrous oxide, methane and water vapor detection using a continuous wave (CW), distributed feedback (DFB) quantum cascade laser (QCL) based absorption sensor system was demonstrated. A 7.73-µm CW, DFB QCL with its wavelength scanned over a spectral range of 1296.9-1297.6 cm-1 was used to simultaneously target three neighboring strong absorption lines, N2O at 1297.05 cm-1, CH4 at 1297.486 cm-1 , and H2O at 1297.184 cm-1 . Minimum detection limits of 1.7 ppb for N2O, 8.5 ppb for CH4, and 11 ppm for H2O were achieved with a 2-s integration time for individual gas detection. The recent development of long wavelength QCLs made it feasible to use the quartz enhanced photoacoustic spectroscopy (QEPAS) technique in the THz spectral range by employing a custom-made quartz tuning forks (QTF) with a sufficiently large space separation between the two QTF prongs to allow optimized THz radiation beam focusing, thereby reaching a detection sensitivity level comparable with the best results reported in the mid-IR. Moreover, an innovative spectroscopic technique, called I-QEPAS was recently demonstrated and potentially may lead to the realization of sensors with ppq detection limit. The I-QEPAS method has been used to detect CO2, reaching a sensitivity of 230 ppt with 10 s averaging time and a corresponding normalized noise equivalent absorption of 2.5 × 10-10 Wcm-1/Hz1/2. Furthermore, a single-QCL based absorption sensor for the simultaneous detection of atmospheric CH4 and N2O at ~7.8 µm using a novel compact multi-pass gas cell was demonstrated. ZACHARY J. TONZETICH, AX-1772, The University of Texas at San Antonio. FUNDAMENTAL COORDINATION CHEMISTRY OF BIOLOGICALLY RELEVANT SMALL MOLECULES. We have made significant progress over the last year in understanding the reactivity and structure of transition metal compounds containing small sulfur-based ligands. In work with synthetic iron(II) hemes, we have quantified the binding affinity of the hydrosulfide ion (HSˉ) to several different meso-substituted porphyrinates. For the prototypical tetraphenylporphyrin (TPP), the binding constant of HSˉ to iron(II) in THF was measured at logKa = 5.3. We have also structurally characterized the [FeII(SH)(TPP)]ˉ complex as its tetrabutyl ammonium salt and recorded the first ever electrochemical data on such a compound. Our findings demonstrate that the binding affinity of hydrosulfide to iron(II) hemes varies in response to the electronic characteristics of the porphyrinate ligand. More electron-withdrawing porphyrinates were found to lead to stronger binding, so much so that an unprecedented hydrosulfide-bridged species, [Fe2(µ-SH)(F8TPP)2]ˉ, was detected with the fluorinated TPP ligand. Correspondingly, use of more electron-donating porphyrinates such as tetramesitylporphyrin lead to weaker binding. In addition to the binding studies, we have also examined the reactivity of [Fe(SH)(TPP)]ˉ with the biologically relevant molecules NO, O2, and 1,2-dimethylimidazole. These studies demonstrated that HSˉ is readily displaced by NO but not by imidazole. One-electron oxidation of [Fe(SH)(TPP)]ˉ produces the unstable iron(III) hydrosulfide complex, which we have studied previously. In tandem to our work with iron(II), we have also investigated the chemistry of gallium(III) porphryinates with sulfur-based ligands. Gallium(III) has a very similar ionic radius to iron(III) and is therefore a good structural analog for its complexes. We have succeeded in synthesizing the first examples of Ga(III) porphyrinates containing hydrosulfide, ethane thiolate, and benzene thiolate ligands. We have also obtained the crystal structure of [Ga(SH)(TPP)], which is the first structural model for the putative [FeIII(SH)(TPP)] species.
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THOMAS M. TRUSKETT, F-1696, The University of Texas at Austin. LIQUIDS NEAR INTERFACES: SINGLE-MOLECULE AND COLLECTIVE DYNAMICS. We completed research this year that provides insights into the structure and dynamics of molecular liquid and complex fluid systems (e.g., nanoparticle and colloidal suspensions) where interfaces play an important role. In two related studies, we used novel computational "inverse" methods to design simple, interacting particle systems to assemble into targeted structures (e.g., diamond or simple cubic lattices in 3d; square and honeycomb lattices in 2d). A third investigation introduced a new statistical mechanical approach for detecting and quantifying real-space clustering in colloidal or molecular fluids based on Fourier-space data from the experimental static structure factor (i.e., pair correlations). Two more studies used a Fokker-Planck equation-based approach to characterize and understand the relationship between position-dependent dynamics and inhomogeneous structure in complex fluids: one focusing on dynamics in the solvation shell of a tagged, diffusing particle and the other examining dynamics in solvation shells adjacent to rigid confining boundaries. The differences in the behaviors of equilibrium and supercooled fluid states were also studied. Other investigations explored how to design novel dispersants for stabilization of oil-in-water dispersions and foams, e.g., using "grafted through" polymer-functionalized iron-oxide nanoparticle clusters. To understand how the various dispersants perform under conditions relevant for deep-sea oil release, the mechanism of droplet formation was experimentally characterized as a function of dispersant type, concentration, and jet velocity. Finally, new web-based statistical mechanical tools–which use novel liquid-state theories that our group recently developed–were introduced for designing colloidal interactions to achieve targeted properties. FRANCIS T.F. TSAI, Q-1530, Baylor College of Medicine. STRUCTURAL AND MECHANISTIC STUDIES OF ATP-DRIVEN PROTEIN MACHINES. The heat-shock protein of 90-kDa (Hsp90) is an evolutionary conserved, ATP-dependent molecular chaperone essential for the folding of a vast majority of signaling and tumor promoting proteins. It is known that Hsp90 is a homo-dimer adopting different three-dimensional structures: a wide-open, V-shaped conformation in the apo state, and a closed dimer when ATP is bound. Despite the wealth of structural and biochemical data, it remains unclear how Hsp90 senses the bound nucleotide and facilitates dimer closure. To address this issue, we determined the atomic structures of the N-domain of mitochondrial Hsp90 (mtHsp90N) required for nucleotide binding in the nucleotide-free and ADPNP-bound state at 1.85 Å and 1.82 Å resolution, respectively. Unexpectedly, nucleotide-free mtHsp90N forms a previously unobserved coiled-coil dimer in the crystal, as does intact mtHsp90 in solution, revealing a novel intermediate conformation that could precede dimer closure. Strikingly, in the absence of nucleotide, mtHsp90 exists in an autoinhibited state that is relieved by ATP. We find that ATP binding results in a dramatic change in local structure leading to the formation of a closed-state dimer essential for protein folding. Our results challenge the prevailing view of the Hsp90 conformational cycle, and suggest a mechanism how ATP binding-induced changes in local structure effect globally Hsp90 conformation critical to its chaperone function. BENJAMIN P. TU, I-1797, The University of Texas Southwestern Medical Center. SELECTIVE REGULATION OF AUTOPHAGY BY METABOLIC STATE. Using prototrophic strains of yeast, we discovered when cells are switched from a rich to minimal culture media that is still fully capable of supporting growth, they induce autophagy as a means of cellular homeostasis. Autophagy induced under these conditions is specifically dependent on a conserved complex of three proteins, Iml1p, Npr2p, and Npr3p. The human ortholog of Npr2p lies in a genomic region that is frequently deleted in cancers, and has been described as a tumor suppressor. Notably, yeast npr2∆ mutants exhibit dysregulated growth reminiscent of cancer and recent studies place the Npr2-containing complex (also known as GATOR1) as an upstream negative regulator of TORC1. In the past year, we have investigated the metabolic properties of npr2∆ mutants to learn what TORC1 is doing to cellular metabolism. We determined that Npr2-deficient cells exhibit a metabolic state that is very distinct from WT cells. Instead of accumulating glutamine, npr2∆ cells consumed substantial amounts of glutamine to satisfy their demands for nitrogen, and maintained high S-adenosylmethionine (SAM) concentrations to fuel growth. Moreover, in normal cells, methionine addition stimulated glutamine consumption for biosynthesis of nitrogenous metabolites, showing how a sulfur amino acid cue is integrated with nitrogen utilization. These data reveal the metabolic basis by which the Npr2-complex regulates homeostasis and demonstrate a key function for TORC1 in regulating the synthesis and utilization of glutamine as a nitrogen source. Collectively, over the funding period we have shown that methionine and SAM constitute a key gauge of cellular metabolic state and amino acid sufficiency. This discovery has significant implications for our understanding of the regulation of cell growth and lifespan by amino acids. We will continue to investigate the role of Npr2 in the regulation of cell growth, metabolism, and signaling under different nutritional contexts. ADAM R. URBACH, W-1640, Trinity University. PROTEIN RECOGNITION AND LABELING VIA SUPRAMOLECULAR PROTEASE INHIBITION.
(1) A manuscript was published describing the predictive recognition of human growth hormone on the basis of its N-terminal phenylalanine by the synthetic receptor cucurbit[7]uril (Q7), and the recognition of native proteins in complex mixtures using a resin with covalently immobilized Q7 groups. We explored the use of this resin as a multivalent affinity matrix and confirmed that it binds in a divalent fashion to divalent peptide guests. (2) A manuscript was published describing the use of Q7 to enhance the analysis of protein fragments by mass spectrometry. This study led to the recent discovery of secondary peptide interactions with Q7 in solution, wherein Phe and His residues interact with opposite portals of Q7. (3) A four-step protein organic semisynthesis was developed on 50-100 mg scale to modify insulin with a single aminomethyl group. The resulting compound has a similar structural fold and binds Q7 at mid-nanomolar affinity.
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KOSAKU UYEDA, I-1720, The University of Texas Southwestern Medical Center. BIOCHEMICAL MECHANISM OF THE GLUCOSE SENSING AND REGULATION OF ChREBP ACTIVITY. ChREBP-dependent gene transcription is regulated by ChREBP trafficking between nucleus and cytoplasm by altered efficiency of ChREBP binding to carbohydrate responsive elements in target genes. The N terminal region of ChREBP (amino acids 1-250) of ChREBP is responsible for the glucose sensing and nuclear/cytosol localization of ChREBP. 14-3-3 proteins form a heterodimer with ChREBP and play important roles in the nuclear/cytosol trafficking of ChREBP. Recently we discovered certain metabolites in liver play critical roles in the trafficking, and we demonstrated that ketones in the liver play dual roles in activation of ChREBP export and inhibition of import. More recently we found that AMP also serves the similar role in the regulation but the biochemical mechanisms are different from the usual mechanism of AMP activation of AMPK. In contrast, AMP stimulates -14-3-3 heterodimer formation by binding directly to ChREBP and inhibits the nuclear localization of ChREBP in rat liver fed with a high fat diet. We will continue to investigate the mechanisms of glucose sensing at the molecular level using X-ray crystallography. RAFAEL VERDUZCO, C-1888, Rice University. CHARGE SEPARATION IN WELL-DEFINED DONOR-ACCEPTOR BLOCK COPOLYMER INTERFACES. Activities in the first year of the grant has focused on the synthesis of donor-linker-acceptor block copolymers and on the study of morphology and electronic characteristics of photovoltaic devices based on these materials. Through a combination of a controlled polymerization from a functionalized initiator, we successfully prepared a series of all-conjugated donor-linker-acceptor block copolymers. Our synthetic strategy enabled control over the length and composition of the linking group, which is the only method reported to date for all-conjugated block copolymers. In related studies, we investigated the impact all-conjugated block copolymers had on the electronic properties of photovoltaic devices. We found a pronounced enhancement of open circuit voltage using an all-conjugated block copolymer additive. Whereas prior studies have found an enhancement in short-circuit current, such a large enhancement in open-circuit voltage is unprecedented and points to interfacial activity of the block copolymer. This work establishes the unique role of conjugated block copolymers in simultaneously dictating morphological and electronic properties at nanometer length scales. Future work will compare the performance of conjugated block copolymers to model multi-layer devices for understanding the properties of the interface and pursue density functional theory calculations for design of the block copolymer linking group. ERIC J. WAGNER, H-1889, The University of Texas Medical Branch. CRYO-EM ANALYSIS OF THE INTEGRATOR COMPLEX. We are continuing our efforts to improve purification conditions for Drosophila Integrator as initially described in the proposal. While these efforts have improved the yield and purity of the complex, the current bottleneck is the actual negative staining and Cryo conditions required to generate a preliminary structure of the complex. We are currently working with the Asturias lab at Scripps where we are sending purified complexes and they are generating grids and acquiring images. We hope that these careful and coordinated efforts lead to a preliminary structure of the Integrator complex. Over the course of the past ten months, we have made significant progress towards mapping the position of specific INT subunits within the complex. In our initial proposal, we described how we could transiently express each dINT subunit in S2 cells. Below, we show how we have been successful to generate 12/14 stable cell lines where IntS11 is tagged with FLAG and a second subunit now expresses MBP at the N-terminus. Importantly, purification using anti-FLAG resin shows that the MBP subunit is efficiently incorporated into the complex and in the case of IntS2, we can observe that the MBP-IntS2 fully replaces the endogenous IntS2 in the complex. We plan to continue our efforts to purify and characterize these "marked" complexes for EM analysis.
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YIHONG WAN, I-1751, The University of Texas Southwestern Medical Center. BIOCHEMICAL CHARACTERIZATION OF PAFAH REGULATION BY MACROPHAGE VLDLR. During the third year of our studies supported by the Welch Foundation, my lab has further investigated the cellular and biochemical mechanisms for how maternal VLDLR modulates offspring health. In addition to prevent neonatal inflammation, we found that maternal VLDLR also enhances offspring bone resorption. Since its cloning decades ago, it is still unknown whether and how VLDLR impacts skeletal homeostasis. We discovered that maternal and offspring VLDLR play opposite roles in osteoclastogenesis and bone resorption. VLDLR deletion in the offspring augments osteoclast differentiation by enhancing RANKL signaling, leading to osteoporosis. In contrast, VLDLR deletion in the mother alters milk metabolism, which inhibits osteoclast differentiation and causes osteopetrosis in the offspring. The maternal effects are dominant. These findings further highlight the critical roles of maternal VLDLR in offspring traits. Our mechanistic studies have also progressed beyond the characterization of how Reelin and Dab2 mediate VLDLR regulation of PAFAH expression. We have found that VLDLR-null lactating mammary gland exhibits higher mTORC1 signaling and cholesterol biosynthesis. Pharmacological probing reveal that rapamycin but not statin treatment of the mother can prevent both the low bone resorption and the inflammatory fur-loss phenotype in their offspring. Genetic rescue reveal that maternal mTORC1 attenuation in adipocytes but not in myeloid cells prevents offspring osteopetrosis and fur-loss. Our studies uncover novel functions of VLDLR and mTORC1 in lactation and osteoclastogenesis, illuminating key mechanisms and therapeutic insights for bone and metabolic diseases. Using neonatal alopecia as visual readout, we have also identified additional maternal factors. By combining in vivo mouse genetic and pharmacological models, in vitro cell-based assays, and biochemical analyses such as LC-MS and metabolomics, our future investigations supported by the Welch foundation will further enhance our understanding of the metabolic control of lactation and the biochemical regulation of offspring health. QINGHUA WANG, Q-1826, Baylor College of Medicine. CHEMICAL MECHANISMS OF COORDINATED EPIGENETIC REGULATIONS IN CELLS. PcG and TrxG are master epigenetic regulators that catalyze trimethylation of histone 3 lysine 27 and lysine 4, respectively, to mark the corresponding genes for transcriptional repression or activation. Without DNA-binding proteins within them, these large protein complexes are believed to utilize DNA-binding transcription factors for their recruitment to thousands of target genes in mammalian genomes. However, the mechanisms by which DNA-binding transcription factors coordinate the binding of PcG and TrxG remained very poorly understood. Therefore, structural and functional studies of ZH, a novel DNA-binding transcription factor newly discovered and characterized in our group, with its DNA recognition motifs, or its binding partners within the PcG and TrxG complexes will reveal new insights into the coordinated epigenetic regulations that is critical to so many fundamental biological processes. In the past year, in order to obtain phase information for the ZH-F1-DNA complex for which we have previously collected X-ray diffraction data to 2.85 Å, we focused on growing heavy-atom derivatives. We have succeeded in collecting X-ray diffraction data for selenium-derived ZH-F1-DNA crystals. We are currently working on solving the phase problem for the ZH-F1 -DNA complex. Furthermore, we have obtained good-size crystals of ZH with EED in PcG or WDR5 in TrxG and X-ray diffraction data will be collected soon.
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YUHONG WANG, E-1721, University of Houston. THE KINETICS AND CONFORMATIONAL CHANGES DURING THE PEPTIDYL 1. We reported a new concept and method to analyze the single molecule FRET data of a ribosome system. The main results are: 1. based on a hierarchic concept, multiple ribosome subpopulations are identified. 2. The subpopulations are self-identified via the cross-correlation analysis of the FRET histogram profiles. 3. The major ribosome subpopulations exchange to each other with a certain pattern, indicating some correlations among the motions of the tRNAs and the ribosomal components. 2. We have developed an assay based on force-induced remnant magnetization spectroscopy (FIRMS) that unambiguously resolves the ribosome's positions on nine consecutive nucleotides during three cycles of translocation. We reveal that both -1" and "-2" frameshiftings occur with high efficiencies on a slippery sequence without a secondary structure. Our results suggest that ribosomal frameshifting may occur more frequently than it had been studied to, more complicated than the current one-step mechanism, and may be biased by both the downstream tRNA and possibly the mechanical force by EF-G. 3. We have measured the dissociation forces of biotin-streptavidin multivalent bonds of different orders, and subsequently reveal the well-controlled formation of double-, triple-, and higher-order multivalent bonds. These experiments demonstrated that the force spectra provided by FIRMS can be a general method for studying noncovalent bonds of different orders and types, analogous to the IR spectra for covalent bonds. ZHIGAO WANG, I-1827 The University of Texas Southwestern Medical Center. BIOCHEMICAL IDENTIFICATION OF PROTEASES INVOLVED IN NECROTIC CELL DEATH. There are a total of 13 serpin proteins identified in humans. Among them, serpin B8 and serpin B13 have significant cell death blocking activity after overexpression. Toward the first aim, previously we used tandem immunoprecipitation to identify Kallikrein-Related Peptidase 15 (KLK15) that specifically conjugated to serpin B13 after necrosis induction. We did siRNA knockdown of endogenous KLK15 and found that necrosis was not significantly affected. It suggests that KLK15 might not play important role in necrosis execution or other proteases perform redundant function such as KLK15. Currently we are continuing to study the effect of tandem immunoprecipitation using serpin B8 as bait. It is possible that blocking proteases conjugated by both serpin B8 and B13 will be able to protect cells from necrotic cell death. Toward the second aim, we tried different protocols to separate intact mitochondria to be used as substrate for protease activity assay. However, we were unable to eliminate lysosome contamination, which produced a significant amount of background activity that prevented further development. Currently we have transferred our effort to assay the leakage of lysosomes during necrotic cell death. Basically cells were loaded with FITC labelled 10KDa dextran beads. During necrosis, the green beads were observed to leak out the lysosome and dispersed into cytosol. For in vitro assay, lysosomes loaded with FITC-labelled beads were isolated from the cells and were used as substrate to incubate with cell lysates. The activity in the lysates that causes lysosome leakage will be further pursued. The leaked beads would be detected by a sandwich ELISA assay where anti-dextran antibody is coated on the plate and anti-FITC antibody will be used to detect FITC-beads bound to the plate. Currently the assay is sensitive enough to detect 0.5ng free FITC-beads. We are testing the cell lysates now to determine if necrotic lysates produces significantly higher activity than the control lysate. CORAN WATANABE, A-1828, Texas A&M University. STREPTOMYCES SAHACHIROI: A RICH TREASURE TROVE OF UNIQUE BIOSYNTHETIC REACTIONS. The x-ray crystal structure of the AziG/5-methylnaphthoic acid complex was solved to 2.2 Å. Gel filtration analysis was performed, which was consistent with AziG forming a tetramer. Gel filtration analysis of AziB with AziG did not reveal a stable complex, which suggests that the complex is formed transiently. Mutagenesis was performed on all polar residues in the aziG active site shell based upon the x-ray crystal structure of the AziG/5-methylnaphthoic acid complex, this included AziG mutants (H44A, H48A, in addition to E57A, S58A, S61A generated previously). Kinetic analyses on the AziG mediated hydrolytic reaction was completed with a DTNB assay with each of the AziG mutants and showed a 2-3 fold reduction in rate and were not distinguishable. No contaminating background hydrolytic activity was observed. The low catalytic competency for the AziG catalyzed reaction (kcat/Km = 1.1 M-1S-1), suggested that the active hydrolase requires association between AziB and AziG to form the fully active enzyme. Additional evidence for a complex, albeit a low affinity one, comes from the observation that the product of AziB is different in the presence and absence of AziG. The results suggest that AziB requires covalently attached product in order for AziG activation to occur. LAUREN J. WEBB, F-1722, The University of Texas at Austin. THE PHYSICAL CHEMISTRY OF BIOLOGICAL INTERFACES. We have published a comprehensive study of electrostatic fields at the interface between several GTPases and their downstream effectors by creating an experimental map of electrostatic fields at the protein-protein interface. These data were used to rationalize selective binding of similarly structured proteins in both in vitro and in vivo environments, and were used to determine the level of simulation detail that is necessary to accurately predict our experimental findings. (Ritchie, JPCB 2015, 119, 13945; Blasiak, PCCP 2016, 18, 18094.) We have used this combination experimental/ computational technique to study a GTPase-effector interface that is inhibited by the small molecule natural product brefeldin A to learn how protein-protein interactions can be affected by small molecules for possible use as drugs. We have continued our collaboration studying lipid membrane structure and dynamics with Dr. Ron Elber. We have focused on making more complex and biologically realistic systems by adding small molecules such as cholesterol to our membrane models to measure the effect on noncovalent membrane organization. A publication is in preparation for submission in July 2016. Our work with the Elber lab has resulted in a joint NIH RO1 grant beginning in June 2016.
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Our experiments rely on vibrational spectroscopy of nitrile probes inserted into the biological system, although there is controversy about the effect of hydrogen bonding on nitrile response to local electrostatic fields. We have used green fluorescent protein (GFP) as a model system for addressing these concerns by biosynthetically incorporating nitriles within GFP. By measuring absorption energies of both the intrinsic GFP fluorophore and inserted nitriles in response to a series of amino acid mutations, we show that observed changes in emission energy of GFP strongly correlate with changes in electric field experienced by both the nitrile probes and the intrinsic fluorophore. Our publication, Slocum, J. Am. Chem. Soc. 2016, 138, 6561, has provided much needed clarity to the study of nitriles in biological systems. R. BRUCE WEISMAN, C-0807, Rice University. PHOTOSTUDIES OF CARBON NANOSTRUCTURES. We continue to develop, refine, and apply our new method of variance spectroscopy. In brief, this measures spectra from many equivalent microscopic regions in a homogeneous Sample of single-walled carbon nanotubes (SWCNTs). Statistical variations in composition cause minor differences among the spectra that we analyze to deduce the concentrations of numerous nanotube structures. One application of the method is in measuring structure-specific absorption strengths (cross sections or molar absorptivities) of SWCNTs. Surprisingly, these essential parameters have remained unknown despite their value for fundamental studies and analytical spectroscopy. Variance analysis provides the key needed information: structure-resolved absolute concentrations, which give us the desired absorptivities once absorption features in the bulk sample are carefully evaluated. We have measured absorptivity values for 13 common small-diameter SWCNTs and deduced an empirical formula for larger structures. These findings finally enable practical quantitative analysis of SWCNT samples using simple near-IR absorption spectroscopy. Further studies are underway using variance spectroscopy to study nanotube aggregation, an important process for SWCNT researchers. In a separate project relevant to cancer research, we developed an advanced optical method to detect and locate small concentrations of SWCNTs in vivo. There are three innovative aspects: diffuse specimen excitation with an LED array; highly sensitive detection using a filtered InGaAs avalanche photodiode; and "spectral triangulation" to deduce SWCNT depth from wavelength-dependent absorption'through tissues containing water. We can detect small SWCNT samples 20 mm inside tissue phantoms and can localize those sources with submillimeter precision. Other progress: further refinements to a non-contact SWCNT spectroscopic method for measuring mechanical strains; analysis / modeling of secondary peaks in SWCNT absorption and emission spectra; and kinetic studies revealing structure selectivity and cooperativity for surfactant displacement of ssDNA wrapped around SWCNTs. KENNETH D. WESTOVER, I-1829, The University of Texas Southwestern Medical Center. CHARACTERIZATION OF COVALENT K-RAS INHIBITORS. 1. We characterized a panel of the most common KRAS mutant isoforms. We did this because the distribution of specific mutations across cancers and the differential responses of patients with specific KRAS mutations in therapeutic clinical trials suggest that different KRAS mutations have unique biochemical behaviors. To further explain these high-level clinical differences and to explore potential therapeutic strategies for specific KRAS isoforms, we characterized the most common KRAS mutants biochemically for substrate binding kinetics, intrinsic and GTPase-activating protein (GAP) stimulated GTPase activities and interactions with the RAS effector, RAF kinase. Of note, KRAS G13D shows rapid nucleotide exchange kinetics compared to other mutants analyzed. This property can be explained by changes in the electrostatic charge distribution of the active site induced by the G13D mutation as shown by x-ray crystallography. High resolution x-ray structures are also provided for the GDP bound forms of KRAS G12V, G12R and Q61L and reveal additional insight. Overall, the structural data and measurements, obtained herein, indicate that measurable biochemical properties provide clues for identifying KRAS-driven tumors that preferentially signal through RAF. Implications: Biochemical profiling and subclassification of KRAS-driven cancers will enable the rational selection of therapies targeting specific KRAS isoforms or specific RAS effectors. 2. We developed an AlphaScreen (Perkin Elmer)-based assay that enables high-throughput screening for new GTP-competitive inhibitors of KRAS G12C that are more chemically accessible and pharmacologically favorable than our current lead KRAS G12C inhibitor, SML-8-73-1. STEVEN E. WHEELER, A-1775, Texas A&M Unviersity. HARNESSING THE POWER OF NON-COVALENT INTERACTIONS FOR ORGANOCATALYSIS. We have made progress quantifying the role of non-covalent interactions in organocatalysis and using this knowledge to design more effective organocatalysts. In particular, we have continued to make advances in understanding stereoselectivity in transition-metal free asymmetric alkylation of aromatic aldehydes. We have shown that the stereoselectivity of these reactions arises from non-covalent electrostatic interactions within the chiral environment of a hexacoordinate silicon intermediate. Furthermore, we have shown that these interactions can be harnessed to design more effective catalysts for these transformations. This depends on our recently developed computer code (AARON), which enables the automated computational prediction of the stereoselectivities of bidentate Lewis-base catalyzed alkylation reactions. AARON has allowed us to examine the origin of stereoselectivity in an unprecedented number of asymmetric reactions and to rationally design new organocatalysts for these reactions. Upon experimental verification (pending), this will be the first clear demonstration of the de novo computational design of asymmetric organocatalysts. Perhaps the most exciting aspect of this work is that it has been largely driven by the work of extremely talented undergraduate co-workers (Rooks, Haas, Porterfield, and Doney). We have also made progress unraveling the origin of stereoselectivity in chiral Brønsted-acid catalyzed reactions. In particular, we recently studied the first enantioselective catalytic Fischer indole reaction, showing that the stereoselectivity of these reactions hinges on the competition among hydrogen bonding, CH/п interactions, and п-
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stacking interactions in the stereocontrolling transition state. These results are informing our efforts to design more effective Brønsted-acid catalysts for asymmetric reactions in collaboration with Benjamin List. ROBERT L. WHETTEN, AX-1857, The University of Texas at San Antonio. CLUSTERS AS MOLECULAR SURFACES: MODIFICATION OF SELECTED NOBLE-METAL THIOLATES. During this initial year of the project, we have achieved progress on several parallel fronts: (a) Analysis of complex mixtures of protected noble-metal clusters by in-line HPLC-ESI-MS. This is a major advance or accomplishment, as one is able to span the entire (m/z)-range of relevance (mass 5 – 40 kDa), with extraordinary high sensitivity and resolution, employing just a few micrograms of clusters, per chromatogram. This is a key enabling method, which will facilitate all the surface-modification work to follow. The proof-of-principle manuscript, documenting the rapid separation and detection of seven (7) major species ranging from Au25 to Au144 clusters, will be submitted shortly, and list the Welch Foundation as a major supporter of this key work. (b) Monitoring of thiolate-exchange reactions of the Au144(SR)60 clusters, using methods including electrospray mass-spectrometry (ESI-MS). Native phenyl-ethane thiolate protected gold clusters, including those of (majority) Au144 and minority species Au137 and Au130, were subjected to reaction conditions with a second thiol(ate), namely captamine, allowing for exchange reactions to proceed. The exchange products were detected with excellent sensitivity and resolution by the advanced ESI-MS methods developed at UTSA by Dr. David Black and the PI. (c) New and improved varieties of protected noble-metal clusters have been generated and characterized at an advanced level, including copper-doped gold-thiolate clusters (cf. the publication list) and aqueous-phase clusters. Also proceeding are analyses of remarkable new clusters from other laboratories (to be reported). MICHAEL A. WHITE, I-1414, The University of Texas Southwestern Medical Center. ANALYSIS OF THE FUNCTIONAL SIGNIFICANCE OF COMPLEX/PROTEIN INTERACTIONS. The major advance I would like to select to describe this year is mechanistic work with important translational implications that was developed from our FuSiOn resource: Modern cancer treatment employs many effective chemotherapeutic agents originally discovered from natural sources. However, a significant challenge currently confronting clinical application is balancing systemic toxicity risk with therapeutic benefit. The cyclic depsipeptide didemnin B, originally isolated from marine tunicates, has demonstrated impressive anti-cancer activity in preclinical models. Clinical use has been approved but is limited by sparse patient responses combined with toxicity risk and an unclear mechanism of action. From a broad-scale effort to match natural products to their cellular activities, we discovered that didemnin B is a potent activator of mTORC1. Mechanistic follow-up demonstrated that translational inhibition is sufficient to explain activation of mTORC1 by didemnin B, but insufficient to explain the rapid and wholesale apoptotic cell death elicited by didemnin B in sensitive cancer cell lines. Importantly, we find that the mechanism through which didemnin B kills cancer cells is through dual inhibition of PPT1 and the translational elongation complex. Furthermore, empirical discovery of a small panel of exceptional responders to didemnin B allowed generation of a regularized regression model to extract a sparse-feature genetic biomarker capable of predicting sensitivity to didemnin B. This may facilitate patient selection that could enhance and expand therapeutic application of didemnin B against neoplastic disease. CHRISTIAN P. WHITMAN, F-1334, The University of Texas at Austin. STRUCTURE FUNCTION RELATIONSHIPS IN ENZYMES. The bacterial pathways for the degradation of mono and polycyclic aromatic hydrocarbons (PAHs) are rich in chemical, mechanistic, structural, and evolutionary questions. There is a significant body of literature on PAH degradation, but the actual substrates and products for many enzymes have never been identified and many proposed activities have never been confirmed because the substrates are not available and the enzymes have not been isolated. This is particularly true for high molecular weight PAHs (e.g., fluoranthene and pyrene). In one major pathway for the microbial degradation of PAHs, ring fission produces a ring-opened species that undergoes a non-enzymatic cyclization event. An isomerase opens the ring and catalyzes a cis to trans double bond isomerization. The resulting product is the substrate for a hydratase/aldolase, which catalyzes the addition of water to the double bond of an α,β-unsaturated ketone, followed by a retro-aldol cleavage. The hydratase/aldolase in the naphthalene pathway (designated NahE) and two putative hydratase/aldolases in the phenanthrene pathway (PhdG and PhdJ) have been cloned, expressed, and purified. The three reactions proceed through a Schiff base mechanism using a conserved lysine residue (e.g., Lys-183 in NahE). Apo and liganded structures identified other potential catalytic residues as well as residues that might contribute to the individual specificities of these hydratase/aldolases. The roles of these residues are under investigation by mutagenesis. Finally, kinetic and NMR studies following the NahE-catalyzed reaction show that it is more complex than previously thought and that the ortho substituent is a key player in the complexity. The complexity is due to the presence of multiple species. KENTON H. WHITMIRE, C-0976, Rice University. THE CHEMISTRY OF NANOMOLECULES. BiPh3 reacts with trifluoroacetic acid in the presence of metal salts or R4N+ hydroxides to produce the first anionic derivatives of bismuth oxo clusters: [Co(H2O)4(NCMe)2][Bi4(µ3-O)2(O2CCF3)9], [Co(NCMe)6][Bi4(µ3-O)2(O2CCF3)10] [Co(HC{CHC(O)Me)2{CHNHMe}}] [Bi4O2(O2CCF3)[Bi4( µ3-O)2
- (O2CCF3)9Ag(C7H8)2]2, Bi4(µ3-O)2(O2C2CF3)9 {Ag(C6H6)2}2 and [Bi4(µ3-O)2 (O2C2CF3)10(AgPPh3)2]. The new Bi4([µ3-O) 2(O2CC6H3C12)8 2C7H8 reacts with Ag2O to produce [Bi12(µ3-O)8(O2CC6H3C12)20].CH2C12 A new polymorph of Bi(O2CC6H4-2-OH)3H2O has been characterized and used to prepared Bi9O7(Hsal)13
.3MeCN cleanly and in high yield. In the course of these studies we discovered that the addition of triflic anhydride to MeCN leads to a previously unobserved asymmetric cyclic trimerization. This paper has been submitted and A is under revision. Reaction of Bi(NO3)3
.5H2O with Co(acac)3 in
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MeCN led to the isolation of the new bismuth nitrate anion, [Bi(NO3)6]3-. Two new Bi coordination compounds with trifluoroacetic acid have been prepared: [Bi2(O2CCF3)6(HO2CCF3).2C7H8 and [CPh(toly)2[Bi6(O2CCF3)20]. Five publications describing these results are in preparation. A. B. A. [M(H2O)4(NCMe)2] [Bi6O2(CF3CO2)12 (M = Co,Ni). B. Cyclic trimer from reaction of MeCN with triflic anhydride. C. GRANT WILSON, F-1830, The University of Texas at Austin. PORGRAMMED SELF-ASSEMBLY OF NANOSTRUCTURES. We have now developed a complete process based on photolithographic techniques and new materials that allows single strand DNA (ss-DNA) to be selectively connected to any face of a nanoscale parallelepiped. The dimensions of the parallelepiped are defined by the limits of photolithography. We have continued to explore directed self-assembly of block copolymers as a path to still higher resolution. The new process required optimization of several sequential steps that must be mutually compatible in order to successfully synthesize the parallelepipeds and conjugate the ss-DNA. The result of this work has yielded what we believe to be the first reproducible asymmetric ss-DNA conjugation process. In effect, we can now functionalize each side of a parallelepiped with a unique DNA sequence. This process will allow us to further pursue our objective of completely programmable self-assembly of micro- and nanostructures. Initial results obtained from this process are promising. The ss-DNA conjugation is easily visible by fluorescence microscopy and we are able to discern which faces are successfully conjugated and which faces are left blank. This provides a useful mid-process analysis step. Although the process requires several sequential steps, the yield of successfully functionalized particles has been steadily increasing, and we can now produce 150,000 parallelepipeds per 36-hour cycle. This is an increase from a pre-optimization yield of only several hundred parallelepipeds per 7-day cycle. Hybridization of complementary particles was tested using both fluorescence microscopy and flow cytometry. It is apparent from each technique that the test particles successfully self-assemble into dimers. Future work will focus on improving the yield of the self-assembly process, with the ultimate goal being the formation of and programmed linear sequences and two dimensional objects including trimers and T-junctions. We will then push on to production of three dimensional objects. LON J. WILSON, C-0627, Rice University. CARBON NANOCAPSULES FOR ADVANCED IMAGING APPLICATIONS. There is an ever increasing interest in developing new stem cell therapies. However, imaging and tracking stem cells in vivo after transplantation remain a serious challenge. Here, we report new, functionalized and high-performance Gd3+ - ion-containing ultra-short carbon nanotube (US-tube) MRI contrast agent (CA) materials which are highly-water-dispersible (ca. 35 mg/ml) without the need of a surfactant. The new materials have extremely high T1-weighted relaxivities of 90 (mM•s)-1 per Gd3+ ion at 1.5 T at room temperature and have been used to safely label porcine bone marrow-derived mesenchymal stem cells for MR imaging. The labeled cells display excellent image contrast in phantom MRI experiments, and TEM images of the labeled cells, in general, reveal small clusters of the CA material located within the cytoplasm with 109 Gd3+ ions/cell. These Gd@(carbon nanotube) materials, covalently derivatized with water-solubilizing carboxyphenylated substituents, thus provide a powerful new technology for labeling and tracking stem cells in vivo in real time. SEBASTIAN E. WINTER, I-1858, The University of Texas Southwestern Medical Center. METABOLISM OF SALMONELLA TYPHIMURIUM IN THE INFLAMED GUT. Our approach relies on a combination of bacterial genetics, metabolite analyses, and animal modeling. In the current (first) grant year, most effort was devoted to establish critical tools and model systems to test our hypotheses. We have now set up two murine models of Salmonella-induced intestinal inflammation (all animal experiments were approved by the IACUC). These systems now allow us to monitor colonization with S. Typhimurium (culture-dependent and –independent methods), severity of intestinal inflammation (measurement of inflammatory markers such as TNFα and IFNγ mRNA in the cecal and colonic mucosa by RT-qPCR), and the composition of the intestinal microbiota (culture-independent methods). We have also generated all isogenic S. Typhimurium mutants deemed of importance for this project. Moreover, we are in the process of developing and validating a GO/MS/MS platform to detect succinate and other relevant dicarboxylic acids in biological samples (bacterial whole cells extracts and intestinal content). Prior to testing our hypotheses in the animal model, we performed initial experiments in a more controlled setting in vitro: We studied the growth of various metabolic mutants in mucin broth under anaerobic conditions in the absence and presence of alternative electron acceptors. Consistent with our hypothesis, succinate utilization was observed only in the presence of electron acceptors. Moreover, administration of sodium tungstate, an inhibitor of anaerobic respiration blunted anaerobic respiration in vitro, although the effect on nitrate respiration was more pronounced than on tetrathionate reduction.
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BLERTA XHEMALCE, F-1859, The University of Texas at Austin. REGULATION OF GENE EXPRESSION THROUGH CHEMICAL MODIFICATIONS OF RNA. In order to identify the dimethyl 5'-monophosphate demethylase(s), we have employed affinity-based proteomics using modified microRNAs to pull-down proteins from "heavy" and "light" cellular extracts generated by SILAC (Stable Isotope Labeling with Amino Acids in Cell Culture). We chemically synthesized a microRNA that contains a dimethyl monophosphate at its 5' end, i.e. the demethylase substrate, and a biotin group at its 3' end to allow the coupling of the RNA to streptavidin beads, i.e. the solid phase. As a control, we synthesized the same RNA but with a 5'-monophosphate end. We are happy to report that the project has made excellent progress because: We have performed the pull-downs with three conditions (beads, beads bound to miR-145-P and beads bound to miR-145Pme2) under three different stringency conditions (three concentration of salt), and have repeated every experiment three times, for a total of 27 samples. We have performed the quantitative MS/MS on 9 of the samples, corresponding to the pull-downs performed under medium stringency. We have analyzed the quantitative MS/MS data by MaxQuant. Our analysis has identified several high confidence positive hits, i.e. proteins that bind significantly more to the dimethylated RNA as compared to the unmethylated RNA. We are now in the process of verifying the candidates generated by this screen. MIGUEL JOSE YACAMAN, AX-1615, The University of Texas at San Antonio. TRI AND MULTI METALLIC NANOPARTICLES, A NOVEL APPROACH TO CONTROL SHAPE, SIZE STRUCTURE AND PROPERTIES OF NANOPARTICLES. In the present cycle of the project we made important strides on advancing the project both in the theoretical and experimental part. We applied thermodynamics at the nanoscale to study the phase diagram of an alloy and then we searched experimentally. We worked on the system Au-Ag-Cu and synthesized all the alloys along the sides of the triangle shown in Figure I. We covered 100% of the alloys Au-Cu, Au-Ag and Ag-Cu. We are now exploring the trimetallic portion of Figure I. We have found the very precise conditions to generate a myriad of nanoparticles with controlled shape, including helical nanowires, shell structures, flat nanowires, decahedra and many other controlled shapes. The work was published in top journals such as Journal of Physical Chemistry C, ACS NANO, and Nature Communications. We continue with the controlled synthesis using thiols as capping agents and the use of ultra-low intensity electron microscopy to study the nanoparticles. Additionally, in this cycle, 3 PhD students working on this project graduated from the program.
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BORIS I. YAKOBSON, C-1590, Rice University. SCIENCE OF NEARLY-1D MATERIALS: FROM NANOTUBES TO NANOWIRES. During the previous/third year of this grant our studies of 2D and 1 D-materials completed particular class of metallic 'inversion' grain boundaries in transition metal dichalcogenides (MX2), as a unique example of electronics of imbedded 1 D-structures as interfaces. We have explored the chemical-thermodynamic stability limits of graphene doping with nitrogen, with key question being how much n-carriers can be chemically 'forced' into the lattice before it destabilizes. Along the lines of stability analysis, we discovered a possibility of converting very thin 3D-crystal films into few-layer novel material, a 'graphitization', demonstrated for ionic compounds. Extending our research to material of emergent interest, 2D P (phosphorene), we found anomalously mobile P-vacancies, what has far-reaching consequences for this material processing and electronics. Last but not the least we explored conceptually, through large-scale molecular dynamics, a possibility of MoS2-based capacitive displacement sensor for DNA sequencing. Intentionally broad scope of selected nanostructures is aimed to identifying the common physico-chemical features, as we described in earlier year review-account. NAN YAN, I-1831, The University of Texas Southwestern Medical Center. TAIL-ANCHOR OF A CRITICAL INNATE IMMUNITY REGULATOR TREX1 ON THE ER. During the previous year, we discovered the surprising molecular function of TREX1 C-terminus, which is frequently deleted in several TREX1 diseases such as RVCL and SLEs. We continued to investigate this new function and recently published our findings in Immunity. Below is the abstract of the paper that summarizes our progress for the last project year. Cytosolic Nuclease TREX1 Regulates Oligosaccharyltransferase Activity IndependentOof Nuclease Activity to Suppress Immune Activation Immunity, 2015 Sep 15;43(3):463-74. TREX1 is an endoplasmic reticulum (ER)-associated negative regulator of innate immunity. TREX1 mutations are associated with autoimmune and autoinflammatory diseases. Biallelic mutations abrogating DNase activity cause autoimmunity by allowing immunogenic selCDNA to accumulate, but it is unknown how dominant frameshift (fs) mutations that encode DNase-active but mislocalized proteins cause disease. We found that the TREX1 C terminus DING-SHYUE YANG, E-1860, University of Houston. ULTRAFAST STRUCTURAL DYNAMICS OF MOLECULAR ASSEMBLIES AT INTERFACES. Using reflection high-energy electron diffraction, we monitored the structural changes of vapor-deposited interfacial assemblies of water and toluene molecules during annealing processes when they went through the glass and crystallization phase transitions. Water was found to consistently form a vertically ordered assembly (without an apparent horizontal order) on the surface of highly oriented pyrolytic graphite (HOPG), which results from the template effect of the surface terrace even though the water-carbon interaction is weak. We also discovered that water can form a vertically ordered thin film on CdTe, which we attribute to the highly similar lattice structures and parameters between cubic ice and CdTe. However, toluene does not form a well-ordered assembly structure readily. On the surfaces of HOPG, crystalline silicon, and CdTe, the intermolecular order in the toluene thin film was seen barely enhanced even after the crystallization temperature previously reported for micrometer-thick films using Raman spectroscopy. We plan to investigate the effect of film thickness on the phase transitions. To understand the energy transfer and charge transfer dynamics across the interface, we first examined the dynamics of substrates following photoexcitation. We studied ultrafast carrier dynamics of crystalline CdTe specimens with different surface conditions using transient reflectivity measurements. Distinct differences in the thermalization and relaxation time constants were observed for oxidized and stoichiometrically restored specimens, which indicate the important role of surface tellurium oxide on the relaxation of photoinduced carriers. The different recovery time for the oxidized surfaces signifies a transfer of electrons to the tellurium atoms with a high oxidation state, i.e., a transient charge separation near the surface. Publications of these findings are currently in preparation. JIN YE, I-1832, The University of Texas Southwestern Medical Center. SATURATED FATTY ACID-INDUCED LIPOTOXICITY We have previously identified FAF1 as another protein that specifically interacts with unsaturated fatty acids. During this grant year, we have determined that FAR is required for degradation of β-catenin, the aberrant accumulation of which triggers development of various cancers. We demonstrate that unsaturated fatty acids stabilize β-catenin by inactivating FAF1 through their direct interaction with the protein. We further demonstrate the physiological relevance of the findings by showing that excess accumulation of unsaturated fatty acids is required for accumulation of β-catenin in kidney cancers. Our finding reveals the oncogenic mechanism of unsaturated fatty acids, and suggests that compounds disrupting the interaction between FAF1 and fatty acids may be useful to treat cancers with excess accumulation of unsaturated fatty acids Following last year's progress, we have also determined that saturated fatty acid-induced accumulation of LPC is responsible for dilation of the ER in kidney epithelial cells. This finding demonstrates the pathological consequence of saturated fatty acid-induced accumulation of LPC. DANNY L. YEAGER, A-0770, Texas A&M University. DEVELOPMENTS AND STUDIES USING SEVERAL COMPLEX SCALED MULTICONFIGURATIONAL METHODS FOR ELECTRON ATOM/MOLECULE RESONANCES. We propose and develop the complex scaled multicontfigurational spin-tensor electron propagator (CMCSTEP) technique for theoretical determination of resonance parameters with electron-atom/molecule systems including open-shell and highly correlated atoms and molecules. The multicongurational spin-tensor electron propagator method (MCSTEP) developed and implemented by Yeager and his coworkers in real space gives very accurate and reliable ionization potentials and attachment energies. The CMCSTEP method uses a complex scaled multicongurational self-consistent field
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(CMCSCF) state as an initial state along with a dilated Hamiltonian where all of the electronic coordinates are scaled by a complex factor. CMCSCF was developed and applied successfully to resonance problems earlier. We apply the CMCSTEP method to get 2P Beˉ shape resonance parameters using 14s11p5d, 14s14p2d, and 14s14p5d basis sets with a 2s2p3d CAS. The obtained value of the resonance parameters are compared to previous results. This is the first time CMCSTEP has been developed and used for a resonance problem. It will be among the most accurate and reliable techniques. Vertical ionization potentials and attachment energies in real space are typically within 0.2 eV or better of excellent experiments and full configuration interaction calculations with a good basis set. We expect the same sort of agreement in complex space. HSIN-CHIH YEH, F-1833, The University of Texas at Austin. NANOCLUSTER BEACONS FOR HIGH SPECIFIC DNA METHYLATION DETECTION. With the Welch support, we have published one original and high-impact research article within this cycle: "NanoCluster Beacons Enable Enzyme-Free N6-Methyladenine Detection" in JACS. The Office of Technology Commercialization at UT Austin is expected to file a provisional patent based on the invention of this new methylation detection sensor (termed methyladenine-specific NCB). Recently, four reports were published in the journals of Cell or Nature revealing the important regulation functions of N6-methyladenine (m6A) in higher eukaryotes and mammals. However, there is no good way to detect m6A. After our JACS publication, we have been contacted by the researchers (e.g. Andrew Xiao at Yale and Yang Shi at Harvard) who published those Cell or Nature papers talking about the novel regulation roles of m6A. With the Welch support, we have established collaboration with these researchers and we expect to bring this technique to the next level in the next three years. SHERRY J. YENNELLO, A-1266, Texas A&M University. THE EQUATION OF STATE FOR A TWO-COMPONENT NUCLEAR SYSTEM. A nucleus is a Fermi liquid composed of two components, neutron and protons. When two nuclei collide there can be an exchange of nucleons (neutrons and/or protons) due to the difference in chemical potential. When the initial nuclei have different neutron fractions the exchange will drive the reaction partners toward a common value of neutron fraction. The composition of fragments resulting from the nuclear collision can be used to measure the amount of equilibrium attained during the reaction. Fragments produced from 35 MeV/nucleon collisions were measured with NIMROD-ISiS to study equilibration via a nucleon transport analysis. The reactions studied were both constant mass (64Ni,64Zn + 64Ni,64Zn) and constant charge (64Zn,70Zn +64Zn,70Zn) systems. The NIMROD-ISiS array is a 4π charged particle array that consists of 228 detector telescopes covering between 3.6° and 167° in θ located inside of a neutron calorimeter. This complete coverage with NIMROD allows for the reconstruction of the fragmenting quasiprojectile so that the amount of equilibration can be measured. Partial, but not complete, equilibration is observed in these reactions. Globally about 80% equilibration is attained. Comparison of this measurement with theoretical models can help to constrain the parameters of the nuclear equation-of-state. HYE-JEONG YEO, E-1616, University of Houston. STRUCTURAL STUDIES OF NOVEL SURFACE POLYPEPTIDES. In bacteria, lipoproteins are important components of the bacterial membranes and play crucial roles in virulence mechanisms of pathogens including the adaptation to various chemical conditions. Our efforts have focused on identifying novel lipoproteins and attempting to gain functional information from their crystal structures. We have made progress on the crystal structure of Cj1090c (Specific Aim 1), a lipoprotein anchored to the outer membrane and exposed to the periplasmic side. To solve the phase problem, we produced selenomethionine labeled Cj1090c proteins. Crystals were grown at 18°C by vapor diffusion in hanging drops against a reservoir solution containing 18% PEG8000, 0.3 M Ca-acetate, 20% glycerol, and 100 mM MES (pH 6.5). Selenomethionine-derivatized crystals of Cj1090c were cryoprotected and data were collected at the 19ID beamline of the Structural Biology Center at APS. Similar to the native crystals, these crystals belonged to the space group P6222 (cell dimension a=b=89.5 Å and c=120.3 Å) and the diffraction data had a dmin spacing of 2.4 Å. The structure was solved by SAD phasing and three 'Se' sites were located using the program AutoSol from PHENIX. Initial structure model was generated by combining automatic building and manual corrections with COOT and was refined using the PHENIX package. Currently, we are in a final stage of structure refinement (R-value of 0.229 and Rfree-value of 0.258). GUIHUA YU, F-1861, The University of Texas at Austin. PROBING THE CHARGE STORAGE MECHANISMS OF MOLECULARLY-ASSEMBLED TWO-DIMENSIONAL NANOCHALCOGENIDES. We are very grateful to the support from the Welch Foundation, which leads to the following exciting progress and results in total 7 refereed journal articles in the past grant year. 2D Material synthesis and self-assembly. In the second year of this Welch-funded project, we have made progress on several novel 2D nanomaterials including chalcogenides (Cu2S, Cu2Se, MoSe2), oxides (ternary oxide such as LiNil/3Col/3Mn1 /302 (NCM)), and phosphates (VOPO4) by microwave-assisted solvothermal or chemical exfoliation method through better understanding of how solvent molecules interact with precursor molecules and in-situ self-assembled synthetic control for confined growth of chalcogenides/oxides/phosphates based ultrathin 2D nanosheets. We extensively characterized their chemical/crystal structures and physical properties. Three papers on this direction have been published (Nano Letters, Chem. Mater., Nano Energy). Charge transport and storage properties in energy storage devices. We made important progress towards better understanding of charge transport and storage properties of as-synthesized novel 2D nanomaterials and some novel conductive polymer-based nanomaterials for potential hybrid organic-inorganic self-assemblies. Detailed electrochemical measurements (e.g. Li+/Na+ storage) of these nanomaterials have been performed and
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investigated, as well as their layer-dependent electrical/electrochemical properties have been studied, resulting in four high-impact journal papers published in Chem. Soc. Rev., Nano Lett., Chem. Mater., Adv. Energy Mater. HONGTAO YU, I-1441, The University of Texas Southwestern Medical Center. BIOCHEMICAL AND STRUCTURAL ANALYSIS OF SISTER-CHROMATID COHESION. Timely establishment and removal of sister-chromatid cohesion are critical for the fidelity of chromosome segregation. Dysregulation of these processes causes aneuploidy, a driver of tumorigenesis and other human diseases. Sister-chromatid cohesion requires the cohesin complex, which consists of Smc1, Smc3, Scc1, and SA2 in humans and forms a ring-like structure. Cohesin binding to chromatin is dynamically controlled by both positive and negative regulators. Wapl is an anti-establishment factor for cohesin and catalyzes the removal of cohesin from chromatin. During S phase, Smc3 acetylation enables the binding of sororin to the cohesin cofactor Pds5, which protects cohesin from Wapl, thus establishing functional cohesion. In the past year, we have determined the crystal structure of human Pds5B bound to an N-terminal fragment of Wapl. We further show that Sororin and Wapl compete for binding to a conserved site on Pds5. Unexpectedly, Pds5B binds to inositol hexakisphosphate (lP6). lP6 stabilizes the Pds5B protein and contributes to the binding of Pds5B to cohesin. Our results thus establish the structural basis of sororin-dependent cohesion establishment and reveal an unexpected role of lP6 in cohesion regulation. YONGHAO YU, I-1800 The University of Texas Southwestern Medical Center. LARGE-SCALE ISOLATION AND IDENTIFICATION OF POLY-ADP-RIBOSYLATED PROTEINS. We have established a state-of-the-art mass spectrometry platform that allows us to perform large-scale analyses of the ADP-ribosylated proteome (protein ADP-ribosylation is a posttranslational modification that is catalyzed by a family of enzymes termed PARP). Using high resolution mass spectrometry. we characterized the human Asp- and Glu-ADP-ribosylated proteome and identified 1,048 ADP-ribosylation sites on 340 proteins that were involved in a wide array of nuclear functions. In addition, we have, within the last year, adapted this pipeline for quantitative analysis of protein ADP-ribosylation. Specifically. using this technology, we identified hundreds of novel PARP downstream effector proteins. In addition, we analyzed the ADP-ribosylated proteome that is sensitive to clinically relevant PARP inhibitors. PARP inhibitors are a class of compounds that have shown great promise in the clinic. In particular, late stage clinical trials have indicated that a subpopulation of (specifically. BRCA-deficient) breast cancer and ovarian cancer patients show dramatic responses to PARP inhibitors. We envision that the identification of these novel PARP substrates will greatly facilitate the understanding of not only the biology of protein ADP-ribosylation, but also how to better utilize PARP1 inhibitors to treat human cancer. In particular, given the preliminary success of PARP1 inhibitors as single agents in small cell lung cancer (SCLC), we hypothesize that: defining their mechanisms of action will yield critical insight to develop improved therapeutic strategies for this deadly disease. Toward this end, we will use a combination of proteomic and biochemical approaches to explore the role of PARP in SCLC. ANVAR A. ZAKHIDOV, AT-1617, The University of Texas at Dallas. ELECTROCHEMICALLY TUNED SOLAR CELL FIBERS BASED ON ORGANIC-INORGANIC PEROVSKITES.
[Al] Impressive performance of hybrid perovskite solar cells reported in recent years still awaits a comprehensive understanding of its microscopic origins. In our work, the intrinsic Hall mobility and photocarrier recombination coefficient have been directly measured in these rwterials in teady-state transport studies. The results show that electron-hole recombination and carrier trapping rates in hybrid perovskites are very low. The bimolecular recombination coefficient (10-11 - 10-10 cm3sm-1) is found to be on par with that in the best direct-band inorganic semiconductors, even though the intrinsic Hall mobility in hybrid perovskites is considerably lower (up to 60 cm2V-1s-1). Measured here steady-state carrier lifetimes (of up to 3 ms) and diffusion lengths (as long as 650 prn) are significantly longer than those in high-purity crystalline inorganic semiconductors. We suggest that these experimental findings are consistent with the polaronic nature of charge carriers, resulting from an interaction of charges with static organic methylammonium dipoles.
[A2] The uses of carbon nanotubes (CNTs) as a flexible, transparent, lightweight and robust electrode material have been further demonstrated in tandem OLED and OPV devices. Parallel tandem organic light emitting devices (OLEDs) were fabricated with transparent multiwall carbon nanotube sheet (MWCNT) and thin metal films (Al, Ag) as interlayers. In parallel monolithic tandem architecture the CNT (or metallic films) interlayers are an active electrode injecting similar charges into sub-cells. On the contrary, the interlayers of in-series tandems are floating ones, injecting opposite charged carriers. In the case of parallel tandems with common anode (C.A) of this study, holes are injected into top and bottom subunits from the common interlayer electrode, whereas in the configuration of common cathode (C.C.), electrons are injected into the top and bottom subunits. Both subunits of the tandem can thus be monolithically connected functionally in an active structure in which each sub-cell can be electrically addressed separately. Our tandem OLEDs have a polymer as emitter in the bottom subunit and a small molecule emitter in the top subunit. We also compared the performance of the parallel tandem with that of in series and we report additional advantages of the parallel architecture over the in-series such as: tunable chromaticity, lower voltage operation and higher brightness. Furthermore, we demonstrate that processing of the MWCNT sheets as a common anode in parallel tandems is an easy and low cost process, since their integration as electrodes in OLEDs is achieved by simple dry lamination process. Here, we demonstrate tunable color parallel tandem OLEDs with combinations of orange and green emitting materials that are deposited from solution or by thermal evaporation in vacuum.
[A4] Various types of Nanoimprinted OPV solar cells have been studied for high molecular weight polymers. The details can be found in our paper, published in ACS Applied Materials and Interfaces. In this work, we demonstrated efficient polymer solar cells made from large molecular weight poly(3-hexylthiophene-2,5-diyl) (P3HT) nanostructures. The chain alignments in non-patterned thin films and nanoimprint lithography (NIL) defined nanogratings
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with different molecular weights P3HT have been compared. We first observe that the chain alignment is favored by medium molecular weight (Mn = 25 kDa) P3HT for non-patterned thin films. However, NIL allows the polymer with large molecular weight (> 40 kDa) to organize by better chain ordering , which is desired for efficient charge transport but difficult to achieve through other techniques. Consequently P3HT/[6,6]-penyl-C61-butyric-acid-methyl-ester (PCBM) solar cells with large molecular weight P3HT nanogratings show a higher power conversion efficiency of 4.4%, which is among the best reported photovoltaics devices using the same PHT/PCBM materials.
[B1] New promising class of material for PV and optoelectronics, a hybrid organic-inorganic lead halide perovskites have emerged as excellent active materials for solution-processable thin-film photovoltaic solar cells as well as photodetectors. Here we created high-performance nanograting patterned perovskite photodetector implemented by nanoimprint lithography (NIL). The spincoated perovskite shows much improved crystallinity and optical properties after NIL and the as-fabricated patterned photodetectors demonstrate significantly improved performance compared to the non-imprinted conventional thin film devices. The mold geometries were also found to affect the optoelectronic performance. Among the perovskite thin film imprinted with Si flat mold, nanohole mold and nanograting mold, the nanograting pattern geometry based photodetectors have demonstrated best performance, showing approximately 35 times improvement on responsivity and seven times improvement on on/off ratio compared with non-imprinted devices. The high performance of NIL-nanograting photodetector has resulted from high crystallinity and favored nanostructure pattern which contribute to higher mobility, longer diffusion length and better photon absorption. Our results have demonstrated that the NIL is a cost-effective method to fabricate high-performance perovskite nanoscale optoelectronic devices, which may pave the way for high-density perovskite nano-photodetector arrays and to provide the integration with the state-of-art electronic circuits.
[C1] While working on CNT yarns for energy applications we have created new type of actuator, powered by a chemical reaction. High power and large-stroke actuators based on twisted and supercoiled Multi-Wall Carbon Nanotubes (CNT) composite yarns were created by integrating high-density Nanoenergetic Gas Generators (NGG) into carbon nanotube sheets. The linear actuation force, resulting from pneumatic driving force of expanding gases within confined nanospace in twisted carbon nanotube yarns can be further increased by increasing NGG loading density and yarns extreme twisting rotation number, as well as selecting NGG type with high stored energetic density and gas generation discharge. Moreover, the actuation force and power can be tuned in various environments: decreased in vacuum, or inert atmosphere and increased in ambient air. A single CNT/NGG supercoiled yarn with diameter of 200 µm produces up to 20MN/m3 adjustable linear force, with up to 10 m/s combustion front velocity, corresponding to stroke power of up to 10 MW/m3. Such powerful yarn actuators can be operated in vacuum, and therefore used for deployment of heavy loads in outer space, such as solar sails. CHENGCHENG ZHANG, I-1834, The University of Texas Southwestern Medical Center. SMALL MOLECULE MODULATORS OF ANGPTL RECEPTOR FOR STEM CELL EXPANSION AND LEUKEMIA TREATMENT. In Aim 1, while we already identified a number of small molecule chemicals that block a downstream signaling pathway of LILRBs, we did not identify small molecule chemicals that bind to LILRBs that can serve agonists or antagonists. To identify potential ligands of the receptors, we modified the original research plan and started to screen protein ligands and blocking antibodies of LILRBs. We successfully identified a series of blocking antibodies against LILRB2,3,4, as determined by the receptor reporter systems we developed. In parallel, we identified a binding protein of LILRB4, and we are testing whether this is an agonist or antagonist of the receptor. In Aim 2a, we showed that immobilized anti-LILRB2 efficiently supported ex vivo expansion of human cord blood HSCs, and published the results in Blood (Deng et al 2015, Blood, 124(6):924-35). In Aim 2b, we showed that two of these identified small molecule compounds that inhibit LILRB downstream signaling delayed leukemia development in the mouse model of acute myeloid leukemia. In addition, we demonstrated that our newly developed anti-LILRB4 blocking antibody successfully blocks homing and induces mobilization of human leukemia cells in xenografted mouse models. This attested that an antagonist of LILRB4 may inhibit the development of LILRB4-expressing leukemia. CHUN-LI ZHANG, I-1724, The University of Texas Southwestern Medical Center. BIOCHEMICAL REGULATION OF THE ORPHAN NUCLEAR RECEPTOR TLX. The orphan nuclear receptor TLX is a master regulator of postnatal neural stem cell (NSC) self-renewal and neurogenesis; however, it remains unclear how TLX expression is precisely regulated in these tissue-specific stem cells. Through the support of Welch Foundation, we conducted systematic analysis of the sequences and factors that control TLX expression in neural stem cells. We demonstrated that a highly conserved cis-element within the Tlx locus functions to drive gene expression in stem cells. We further showed that the transcription factors SOX2 and MYT1 specifically interact with this genomic element to directly control Tlx enhancer activity during embryogenesis and in postnatal central nervous system, Knockdown experiments further reveal that SOX2 dominantly controls endogenous expression of TLX, whereas MYT1 only plays a modulatory role. Importantly, TLX is essential for SOX2-mediated in vivo reprogramming of astrocytes and itself also sufficient to induce neurogenesis in the adult striatum. Together, our findings unveil functional genetic interactions among transcription factors that are critical to neural stem cells and in vivo lineage reprogramming in the adult mammalian brain.
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DAVID YU ZHANG, C-1862, Rice University. NATIVE CHARACTERIZATION OF DNA AND RNA STRUCTURE THERMODYNAMICS. The research team has finished developing fluorescent gel assays to characterize the native thermodynamics of fluorophore-DNA interactions, single nucleotide DNA dangle motifs, and multinucleotide DNA dangle motifs. These parameters sets have never before been reported. Multinucleotide dangles are discovered to have an asymptotically destabilizing thermodynamic effect on nearby DNA duplexing, contradicting the current standard model for DNA thermodynamics. A manuscript reporting on these findings has been submitted to Nature Communications for publication on April 6, 2015 and is currently in external peer review. Subsequently, the research team has developed a second generation method for native thermodynamic characterization which allows higher throughput and continuous characterization across a wide range of temperatures, allowing more accurate inference of ∆H0 and ∆S0 values. The team has initially applied these techniques to the characterization of DNA nucleotide modifications such as methylation on CpG motifs, as well as chemical groups such as C3 spacers and 5'-nitroindoles. Moving forward, the team will systematically characterize the thermodynamics of single nucleotide bulges, backbone modifications such as phosphorothioates, and additional nucleotide modifications such as hydromethylation, iso-C/iso-G, locked nucleic acids, and DNA-RNA chimera sequences. JUNJIE ZHANG, A-1863, Texas A&M University. THE STRUCTURAL BASIS OF RIBOSOMAL SILENCING IN TUBERCULOSIS. (1) We have characterized an Mtb Ribosomal silencing factor S (RsfS), which represses the ribosomal activity. Our cryo-EM structure of RsfS in complex with the Mtb 50S ribosome (paper accepted in Structure) shows the RsfS binds to the L14 protein on the Mtb 50S subunit, which displaces the 30S subunit to inhibit the protein synthesis. (2) We have determined the cryo-EM structure of the Mtb 70S ribosome at 5.6Å resolution (manuscript in preparation). This allows us to build a model for the entire Mtb 70S ribosome, including the unique rRNA and protein expansion segments. Compared with our structure of the Mtb 50S ribosome, we saw a 40º outward bending of a 107 nucleotide-long rRN4A expansion segments (termed "handle") upon 30S binding. This suggests the handle may have a role in regulating the 70S formation. (3) We have determined a preliminary cryo-EM density map of the Mtb ribosome bound with the drug capreomycin at 4.5Å resolution. At this resolution, we can clearly see the density of the capreomycin and start to see some bulky protein sidechains from the ribosome. We would further improve the resolution of our density map by collecting more cryo-EM images at higher magnification to more clearly define the ribosomal residues that are interacting with capreomycin. We will then compare the drug-binding pocket of the Mtb ribosome with the ones in other bacterial ribosomes. RENYI ZHANG, A-1417, Texas A&M University. CHEMICAL KINETICS AND MECHANISM OF HYDROCARBON OXIDATION REACTIONS. Experimental and theoretical studies have been carried out to investigate the hydrocarbon oxidation reactions initiated by the hydroxyl radical (OH) and ozone (O3) and to assess their contributions to formation of tropospheric ozone and secondary organic aerosol (SOA). Progress has been made in experimental studies of the oxidation of biogenic (isoprene and α-pinene) and anthropogenic (toluene and xylene) hydrocarbons. Using an environmental chamber, we have simulated the OH-initiated oxidation of isoprene, α-pinene, toluene, and m-xylene and elucidated their roles in aerosol nucleation and aging of primary particles, such as soot particles. Formation of nanoparticles from nucleation of the hydrocarbon oxidation has been examined and attributed to their distinct oxidation mechanisms and product yields, using a particle size magnifier (PSM) and thermal decomposition - ion drift - mass spectrometry (TD-ID-CIMS) capable of measuring the particle size and chemical compositions down to 1 nm. In addition, size-classified soot aerosols are introduced into the environmental chamber in the presence of hydrocarbons, photolytically generated OH, O3, and nitrogen oxides. The evolution in the properties of soot particles is simultaneously monitored, including the particle size, mass, particle effective density, dynamic shape factor, mass fractal dimension, and coating thickness. In addition, quantum chemical calculations have been conducted to investigate the cluster formation from the interaction of organic acids, sulfuric acid, and amines. Geometry optimization and frequency calculations are further performed using high-level theories. Our experimental measurements and theoretical calculations provide evidence on the critical roles of organic species in atmospheric aerosol nucleation and growth. XUEWU ZHANG, I-1702, The University of Texas Southwestern Medical Center. STRUCTURAL BASIS FOR THE INTERACTION BETWEEN CLASS B PLEXINS AND PDZ-RhoGEF/LARG. To understand the high degree of specificity between class B plexin and PDZ-RhoGEF/LARG, we crystallized the full-length cytoplasmic region of PlexinB2 in complex with the PDZ domain of PDZ-RhoGEF. We determined the crystal structure of the complex at 3.2 Å resolution. The structure reveals that, in addition to the motif/PDZ domain interaction, plexin uses its three dimensional domain to form a secondary interface with the PDZ domain. Residues involved in the secondary interface are highly conserved, suggesting functional importance. We then conducted affinity measurements by using isothermal titration calorimetry. The results showed that the full-length cytoplasmic region of PlexinB2 binds the PDZ domain with a Kd value of ~2 µM, approximately 10-fold tighter than the interaction between the isolated C-terminal motif and the PDZ domain. We tested the effects on the affinity of a panel of mutations in the secondary interface. Many mutations significantly decreased the binding, with some of them reducing the affinity to similar levels as the motif/PDZ interaction. These results support the notion that the secondary interface contributes to the specific and tighter interaction between plexin and PDZ-RhoGEF/LARG, ensuring faithful signaling. We plan to perform in vitro activity assays and cell-based functional assays to confirm that the secondary interface is important for activation of PDZ-RhoGEF/LARG and signaling inside the cell.
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YAN JESSIE ZHANG, F-1778, The University of Texas at Austin. CHEMICAL SENSORS TO DETERMINE PROLINE ISOMERIC SPECIFICITY OF RNA POLYMERASE II. The post-translational modification (PTM) states of the unique structure of RNA Pol II at the C-terminal domain have been found to be correlated to different stages of transcription. The interpretation of the biological implication of such PTM states are further complicated since there seems to be cross-talk between different sites. Rtrl, as well as its human homologue RPAP2, was initially identified by several labs as a eukaryotic phosphatase that targets the C-terminal domain of RNA polymerase II (CTD). However, in the only relevant crystal structure previously known (K. lactis Rtrl), neither an active site pocket nor phosphoryl-transfer activity was detected in K. lactis Rtrl, casting doubt on the function and enzymatic activity of this family of proteins. Recently, we determined the crystal structure of a new eukaryotic phosphatase, S. cerevisiae Rtrl. Our structural analysis of Rtrl revealed additional features that were disordered in the previously solved K lactis structure. For example, we detected within the continuous polypeptide of Rtrl a deep groove between the zinc finger core motif and a movable helical pair, potentially suitable for a substrate binding pocket. Consistent with this model, a solvent-derived sulfate ion was trapped in the groove, mimicking the phosphate binding mode. Through bioinformatics analysis and mutagenesis, we identified residues that are essential for the phosphoryl-transfer reaction which are conserved from yeast to human in both identity and function. Yeast strains with such mutations were defective in dephosphorylation of RNA polymerase II CTD and showed a phenotype of slowed growth. Our results resolve the conflicts of the previous structure as well as provide extended biochemical and biological mechanistic insight. Perhaps most importantly, our structure revealed that the protein folding of Rtrl differed dramatically from that of all previously solved phosphatases, suggesting a unique reaction mechanism for phosphoryl-transfer. JOHN C.-G. ZHAO, AX-1593, The University of Texas at San Antonio. EXPEDITIOUS MODIFICATION OF ORGANOCATALYST STRUCTURES FOR IMPROVED STEREOSELECTIVITIES. In the past grant year, we completed another example of diastereodivergent catalysis by using the modularly designed organocatalysts (MDOs), which are self-assembled in the reaction media from the precatalyst modules. Both cis- and trans-fused pyrano[2,3-b]pyrans could be obtained from the same substrates in high enantio- and diastereoselectivities (the Angew. Chem. Int. Ed. paper). We also realized two new methods for the stereoselective synthesis of polysubstituted spirooxindoles using organocatalyzed tandem Michael-Michael reactions using different substrates and organocatalysts (the Adv. Syn. Catal. and Org. Biomol. Chem. papers). The enantioselective direct Mannich reaction of a-styrylacetates was also accomplished (the Org. Lett. paper). This is the first example of organocatalyzed direct Mannich reaction of unfunctionalized esters. During the research, we also observed an unprecedented organocatalyzed C-C bond scission reaction, which was utilized to achieve the enantioselective 13-alkylation of saturated aldehydes (Synlett paper). This method provides an alternative way for the β-alkylation of saturated aldehydes. In addition, we have completed the project on the enantioselective synthesis of 2-amino-4H-chromene derivatives (J. Hereocycl. Chem., in press) and the use of prolinal dithioacetals for the direct nitro-Michael additions (Tetrahedron, currently under revisions). The following sub-projects were also initiated during the past grant period and currently are going on well in the lab: 1. the further utilization of the organocatalyzed C-C bond scission reaction in synthetic methodology development; 2. the diastereodivergent tandem Mannich-Michael reaction for the stereoselective synthesis of piperidines using MDOs; 3. the anti-Mannich reaction catalyzed by MDOs; 4. an unprecedented tandem formal [2+2+2]-Henry reaction catalyzed by organocatalysts. ALEKSEI M. ZHELTIKOV, A-1801, Texas A&M University. OPITCAL DETECTION OF ULTRAFAST ELECTRON DYNAMICS AND ELECTRON-INITIATED CHEMICAL PROCESSES. Experiments performed during the reporting period have shown that a combination of ultrashort pulses in the mid-infrared and nonlinear-optical methods of pulse characterization are ideally suited for the analysis of fundamental molecular motions, helping confront the long-standing challenges of chemically specific spectroscopy and recognition of molecular modes. We demonstrate that the spectral modulation of an ultrashort mid-infrared pulse induced by molecular rovibrational modes can give rise to high-visibility interference patterns and well-resolved echo revivals in the time domain, which can be read out by means of cross-correlation frequency-resolved optical gating based on broadband four-wave mixing in a gas phase, suggesting a powerful tool for the detection, recognition, and remote sensing of molecular vibrations and rotations. We have also experimentally demonstrated that time-domain modulation of stimulated emission depletion (STED), combined with properly designed lock-in detection, can radically enhance the contrast of fluorescent images of strongly autofluorescent biotissues and chemical systems. In our experiments, the temporally modulated STED technique, implemented with low-intensity continuous-wave laser sources, is shown to provide an efficient all-optical suppression of a broadband fluorescent background, allowing the contrast of fluorescent images of mammal brain tissues tagged with nitrogen-vacancy diamond to be increased by five orders of magnitude. As a part of the program toward developing efficient tools for chemically specific spectroscopy in the mid-infrared, a physical scenario whereby freely propagating mid-infrared pulses can be compressed to pulse widths close to the field cycle has been identified, enabling the generation of sub-two-cycle pulses with a peak power up to 60 MW are generated in the range of central wavelengths tunable from 5.9 to 6.3 µm.
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JUNRONG ZHENG, C-1752, Rice University. MULTIPLE-DIMENSIONAL OPTICAL SPECTROSCOPY. The major breakthrough we made this year was to reveal the breakdown conditions of Born Oppenheimer Approximation on metal nanosurfaces. (Nat. Commun. 7, 10749, 2016). QING ZHONG, I-1684, The University of Texas Southwestern Medical Center. REGULATION OF THE CLASS III P13K BY NUTRIENT-SENSING KINASES IN AUTOPHAGY. We have generated two critical reagents for this proposed study. 1), NRBF2 knockout mouse embryonic fibroblasts complemented with wild type NRBF2 and NRBF2 AA and DD phosphorylation mutants. These stable cell lines will be crucial to study the function of NRBF2 phosphorylation in the regulation of PI3KC3 activity and autophagy. 2), NRBF2 phospho-antibodies that specifically recognize the phosphorylated form of NRBF2. This reagent will be used to evaluate the endogenous NRBF2 phosphorylation upon autophagy stresses in a mTORC1 dependent manner. We have also made significant progress in understanding the function of NRBF2-ATG14 in autophagy. We have discovered that, ATG14 has an unexpected function in mediating autophagosome-lysosome fusion, in addition to its known function in autophagy activation. This work is recently published in Nature. In our preliminary results, we found that NRBF2 might regulate this ATG14 mediated function in autophagosome fusion. We will further explore its precise function and mechanism in this process. HONGCAI JOE ZHOU, A-1725, Texas A&M University. EFFICIENT CARBON CAPTURE WITH FUNCTIONALIZED POROUS POLYMER NETWORKS (PPNs). We report a facile one-pot synthetic method to produce large scale metalloporphyrin containing porous polymer networks, named PPN-23 and PPN-24, of which PPN-24 is the firstly reported 3D porphyrin based PPNs obtained by using this bottom-up synthetic strategy. This unique methodology is based on the extended condensation reaction between pyrrole and aromatic aldehydes including benzene-1,3,5-tricaialdehyde (PPN-23) and tetrakis(4-formylphenyl)silane (PPN-24). Porphyrin based PPNs are very exciting due to the presence of basic pyrrole containing macrocyclic cavity, which facilitates strong interaction with Lewis acid CO2. These materials possess high surface areas and demonstrated outstanding adsorption capacity for CO2. This simple and affordable synthetic approach described here may contribute significantly in wide-scale applications in environmental research. We also report the fabrication of two amine functionalized PPNs, namely PPN-80 and PPN-81, based on the nucleophilic substitution reaction between chloromethyl benzene and ethylene diamine. For PPN-81, a surfactant template is also employed to direct the assembly, and leads to enhanced porosity and subsequent superior adsorption performance. The abundant secondary amine groups incorporated in the structure enable these PPNs with selective CO2 adsorption ability. CHAIR GRANTS ZHIQIANG AN, CHAIR AU-0042, The University of Texas Health Science Center at Houston.
Dr. An's laboratory is well published and funded during the 2015-2016 academic year. The group currently consists of more than sixteen students, postdoctoral fellows, and scientists. Dr. An authored/co-authored multiple peer reviewed scientific journal articles and presented scientific lectures in universities, industries, and at conferences both nationally and internationally during the 2015/2016 academic year. Dr. An's lab is well funded by grants from Johnson & Johnson, Merck, PanaMab, CPRIT and the NIH. Dr. An was also active in both graduate student and postdoctoral fellow training and in participation of committees and other professional activities, including journal editorial boards. ERIC V. ANSLYN, CHAIR F-0046, The University of Texas at Austin. Our group is generally involved in the creation of optical sensors for a variety of real world applications of benefit to the pharmaceutical industry and beverage manufacturing. We have pioneered the use of cross-reactive arrays of supramolecular sensing for creating patterns via chemometrics that diagnose complex mixtures. Over the previous year we have taken this work deeper into the analysis of wine, with a study that demonstrated the accurate prediction of wine varietals blends could be determined. Our methods proved more accurate than human test panels, and showed that the falsification of wine labeling could be determined as a forensic method.
Further, while all our previous differential sensing methods relied on the analysis of optical responses as data for chemometric processing, we recently shown that nucleic acid sequence information could be an even more powerful approach. By using the sequences of aptamers that bound to cell surfaces, their population changes could be correlated to cell type via principle component analysis. This was the first use of sequence information as patterns for complex mixtures of analytes.
As a last study of differential sensing, we challenged ourselves to consider what would be the most difficult analyte class for chemical assays to differentiate. We considered lipids as a suite of analytes that differ only by length of fatty acids, positions of alkenes, and stereochemistry thereof. Hence, we devised a differential sensing scheme consisting or serum albumins and various fluorophores. After olefin metathesis on the unsaturated fatty acids, a very clear linear discriminant analysis plot allows for lipid feature identification.
Over the previous year, we also had considerable success in our endeavors to generate rapid supramolecular methods to measure enantiomeric excess. We took the technique to the labs of Scott Miller at Yale University for the analysis of asymmetric Baeyer Villager reactions, and generated a new method for chiral amine ee quantitation.
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DANIEL W. ARMSTRONG, CHAIR Y-0026, The University of Texas at Arlington. As in previous work we continued to push the limits of the chiral recognition possibilities of functionalized cyclofructan and other chiral macrocycles. Particularly notable were the first reported enantiomeric separations of cationic hetero [6] helicenes. The versatility of the cyclofructan chiral selector allows for complete resolution of these compounds in both analytical and preparative modes. The configurational stability of three cationic hetero [6] helicenes was measured. For each replacement of an oxygen atom by an amino group, the racemization barrier increases significantly (∆G' = 29.8, 36.3 and >37 kcal mol-1 for 1+, 2+, and 3+ respectively). (The enantiomeric resolution of 21 ruthenium (II) polypyridyl complexes was achieved with the same class of cyclofructan-based chiral selectors using polar organic solvents.) The results indicated that pi-pi interactions, steric effects, and hydrogen bonding contribute to the chiral recognition of ruthenium II polypyridyl complexes. In two new directions for this work, we have demonstrated that chiral substrates better separate difficult nonchiral substances than other approaches. A case in point is the separation of fluorinated and desfluorinated pharmacologyically active molecules. In these cases the fluorine containing molecules are the active pharmaceutical ingredients while the desfluoro analogues (that have the analogous structure and size) are the "difficult to remove impurities. We also are engineering chiral selectors on new particle supports that permit ultrafast separations (~5-40 sec) while maintaining essential molecular recognition properties and high efficiencies. We have demonstrated that the latest, most modern commercial equipment is often inadequate for such studies. Our ionic liquid research continues to produce outstanding results in areas of synthesis, separations and mass spectrometry. For example deprotection of amino acids and peptides can be performed in < 10 min and using milder conditions by using a properly "tuned" ionic liquid. Previous approaches took several hours to days to complete. A competing and superior method to the classic Karl Fischer titration for water was devised. The essential step was developing a highly polar dicationic liquid that was completely stable at high temperatures to water and oxygen. Finally, it was demonstrated the PIESI (paired ion electrospray ionization) reagents greatly reduce matrix effects and ionization suppression in ESI-mass spectrometry. PIESI reagents are floride ion salts of diationic ionic liquids. M. ZOUHAIR ATASSI, CHAIR Q-0007, Baylor College of Medicine.
Autoimmune diseases (ADs), are growing in complexity as diagnoses improve and many factors escalate disease risk. Considerable genetic similarity is found, and ADs are frequently associated with major histocompatibility complex (MHC) genes. However, a given disease may be associated with more than one human leukocyte antigen (HLA) allotype, and a given HLA may be associated with more than one AD. The associations of non-MHC genes with AD present an additional problem, and the situation is further complicated by the role that other factors, such as age, diet, therapeutic drugs, and regional influences, play in disease. This review discusses some of the genetics and biochemistry of HLA-linked AD and inflammation, covering some of the best-studied examples and summarizing indicators for class I- and II-mediated disease. However, the scope of this review limits a detailed discussion of all known ADs.
Our previous work aimed at elucidating molecular bases for immune recognition of BoNT, types A and B, and role of anti-toxin immune responses in defense against BoNT. Using 92 synthetic 19-residue peptides, overlapping by 5-residues, and comprising entire toxin (A or B) we determined peptides binding to anti-toxin Abs of human, mouse, horse and chicken. We also localized the regions recognized by Abs of cervical dystonia patients who became non-responsive to correlate toxin during treatment with BoNT/A or /B. For BoNT/A, patients' blocking Abs bound to 13 surface regions (5 on L and 8 on H subunit) and the responses to each were under separate MHC control. The antigenic regions coincided or overlapped with synaptosomes binding regions. Ab binding blocked BoNT's ability to bind to neuronal cells, and selected peptides inhibited BoNT's action in vivo. A combination of three strong antigenic peptides detected blocking Abs in 88% of immunoresistant patients. Administration of epitopes, linked at the N(α) group to monomethoxyployethylene glycol, into mice with ongoing blocking anti-toxin Abs, reduced levels of such Abs. This may be suitable for clinical applications. Defined epitopes will be valuable in synthetic vaccines design..
BoNT intoxicates cells in a preset mode initiated by binding to cell surface, internalization and enzymatic cleavage of substrate, thus, inhibiting synaptic exocytosis. Immune significance of BoNT/A C-terminal heavy chain (Hc) and light chain (Lc) domains were studied extensively. We explored the significance of BoNT/A heavy chain N-terminal (HN) region as a vaccine candidate. Mice immunized with recombinant HN519-845 made antibodies (Abs) that protected against lethal dose of BoNT/A. Immuno-dominant regions of HN519-845 were identified and individually investigated for Ab response along with synthetic peptides carrying those regions. Results were confirmed by patch-clamp analysis where anti-HN Abs were studied for the ability to block toxin-induced channel formation. Results indicated for the first time that HN519-593 evoked protective Abs and could be valuable in a vaccine design.. We determined T-cell proliferative responses of the peripheral blood lymphocytes (PBL) from 25 BoNT-treated patients to 31 synthetic overlapping peptides covering the Hc of BoNT/A. PBL responses to Hc peptides varied among patients. Fourteen patients treated only with BoNT/A recognized 2-13 (average 6.4) peptides/sample at Z>3.0 level. Six peptides (residues 855-873, 1023-1041, 1051-1069, 1093-1111, 1135-1153 and 1247-1265) were recognized by 36-57% of these PBLs. Effect of treatment parameters on peptide T-cell recognition was investigated..
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VYTAS A. BANKAITIS, CHAIR BE-0017, Texas A&M University System Health Science Center. We have made progress in seven major areas this year. Area 1 – Sec14-like phosphatidylinositol transfer proteins (PITP5) integrate diverse territories of intracellular lipid metabolism with stimulated phosphatidylinositol-4-phosphate production, and are discriminating portals for interrogating phosphoinositide signaling. Last year we validated the first small molecule inhibitors (SMIs) of the yeast PITP Sec14. These SMIs are nitrophenyl(4-(2-methoxyphenyl)piperazin-1-yl)methanones (NPPMs), and are effective inhibitors in vitro and in vivo. This past year we capitalized on that advance by undertaking an unbiased genetic approach to address these issues. We have now identified a structural 'bar-code' that predicts drug sensitivity vs resistance among highly homologous Sec14-like proteins – some of which are drug sensitive and some which are not. That MS is nearing completion and is slated for submission by September. Moreover, using variomics technologies we are identifying what other genes play a role in resistance to NPPMs. Area 2 – Lipid droplet (LD) utilization is an important cellular activity that regulates energy balance and lipolytic release of lipid second messengers. As fatty acids exhibit both beneficial and toxic properties, their release from LDs must be controlled. We capitalized on our discovery that yeast Sfh3, an unusual Sec14-like phosphatidylinositol transfer protein (PITP), is an LD-associated protein that inhibits lipid mobilization from these particles, to characterize a new and unusual activity required for targeting of Sfh3 to LIDS. This activity is not a classical 'receptor'. Rather it regulates the surface properties of the LD, we have evidence that it has intrinsic and novel acyltransferase activity, and that its production is subject to very unusual mRNA splicing program. We are presently characterizing this activity. Area 3 – Root hairs are elongated extensions of plasma membrane designed for efficient nutrient absorption. Their development involves a polarized membrane growth program which initiates at a precise position on the root hair epidermal cell plasma membrane. The Arabidopsis AtSfh1 protein is critical for root hair biogenesis, and it is comprised of an N-terminal Sec14-domain and a C-terminal nodulin domain of the Nlj16 family. We discovered the unique modular domain organization ofAtSfh1 regulates phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2] signaling in polarized root hair growth. The Sec14-domain supports PtdIns(4,5)P2 synthesis, and PtdIns(4,5)P2 subsequently directs multiple aspects of the root hair tip-growth program. We further demonstrated that the AtSfh1 nodulin domain is a high-affinity PtdIns(4,5)P2 binding module, and that AtSfh1 PtdIns(4,5)P2- binding activity is required for polarized PtdIns(4,5)P2 distribution during root hair development. Those findings describe a mechanism for how signaling machines can be organized to produce highly diverse, yet coherent and high resolution membrane signaling systems. One half of this story was published in a major paper in Molecular Biology of the Cell. The second half is almost completed and slated for submission as a major paper by September 2015. Area 4 – To understand how PITPs work as molecules to stimulate and organize phosphoinositide signaling, it is essential to understand how these proteins bind and release their lipid ligands. We have now made substantial progress on Sec14 using Cys-directed probe mapping, and are now using hydrogen/deuterium exchange technology to map protein dynamics during the lipid exchange reaction at atomic resolution. We have employed computational simulation methods to model how both Sec14-like and mammalian PITPs bind membranes and the conformational dynamics of these proteins associated with lipid exchange. Genetic and biochemical methods are being used to test the predictions of these simulations and, satisfyingly, supporting data are being collected. Area 5 – This year we generated PITPa conditional knockout mice. We previously showed the constitutive knockout of this gene results in a very rapid onset spinal neurodegenerative disease. Moreover, we generated loss-of-function mice for its close homologs PITPb and PITPnc1. These colonies are now being expanded for analysis of mutant phenotypes. Interestingly, we have some data that PITPa and PITPb double deficiencies compromise embryonic neural stem cell self-renewal and this area is now being actively investigated. Area 6 – Inborn errors of metabolism (IEMs) occur with high incidence in human populations. Especially prevalent among these are inborn deficiencies in fatty acid beta-oxidation (FAO) that are clinically associated with developmental neuropsychiatric disorders, including autism. In the last year we discovered that neural stem cell (NSC)-autonomous defects in the activities of TMLHE (an autism-risk factor that supports long-chain FAO by catalyzing carnitine biosynthesis), of CPT1A (enzyme required for long-chain FAO transport into mitochondria), or with fatty acid mobilization from lipid droplets depleted NSC pools from mouse embryonic neocortex. The NSC depletion resulted from increased incidence of symmetric differentiating divisions. Our documentation for a direct role for FAQ in controlling NSC self-renewal vs differentiation in mammalian embryonic brain identifies stem cell homeostasis as a significant mechanism for linking IEMs with human cognitive disorders such as autism. This MS is under review at Cell Reports. Area 7 - We described a new set of protein:protein interactions involving the cystic fibrosis transmembrane regulator (CFTR) protein that govern its trafficking itinerary through the mammalian endomembrane system. The insights gained suggest new ideas for manipulating the system to reduce the severity of cystic fibrosis. This McDermott et al manuscript is in revision at PlosOne after a round of positive reviews. ALLEN J. BARD, CHAIR F-0021, The University of Texas at Austin. Over the reporting period (June 1, 2015 through May 31, 2016), we have extended the field of studying collisions on ultramicroelectrodes (UMEs) to single molecule systems. We have successfully demonstrated that single biological macromolecules can be detected and sized with the collision methodology, and a technique for the detection of single ions was also successfully investigated. We have also studied single vesicles as they collide and interact with a platinum electrode surface. We have furthered the study of observing single emulsion droplets colliding with an electrode surface to study ion transfer across the interface between two immiscible electrolyte solutions, which is the first time that electron transfer and ion transfer have been directly coupled.
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We have continued pursuing investigations with the scanning electrochemical microscope (SECM) by investigating nanometer objects with nano-SECM. We have also maintained our interested in the surface interrogation mode of SECM, which has been used to study catalysts and attain information on intermediates during electrocatalytic reactions. We have studied the electrocatalysis of perovskites as a material for solar water splitting as well as composite materials to test their efficiency.
We have been continuing investigations with the tunneling UME by developing methods to nucleate and grow single platinum nanostructures. We have also worked out a theoretical framework for the electron transfer across a tunneling barrier. Finally, we have continued our pursuits of electrogenerated chemiluminescence by investigating new compounds, such as a new family of oligothienyl-BODIPY molecules and starburst oligofluorenes. ANDREW R. BARRON, CHAIR C-0002, Rice University. Aqueous systems, regardless of composition, heat according to bulk dielectric properties under radiofrequency (RF) exposure at 13.56 MHz. Nanoparticle suspensions, which have long been the subject of debate, display the same heating as simple salt solutions of similar conductivity, indicating that nanoparticles do not contribute to RF heating by any unique mechanism. Peak heating at 13.56 MHz for aqueous systems occurs at 0.06 S/m, beyond which increases in conductivity result in decrease in heating rate. Biologically relevant systems, such as blood and body fluids, exceed this peak heating conductivity, precluding the use of conductive materials for heating rate enhancement. Instead, kosmotropic or water-structuring materials including sugars, glycols, zwitterionic molecules and even a water-soluble fullerene, may be added to these systems to reduce conductivity and enhance heating rate accordingly. Kosmotropes, a class of materials that stabilize water structure, can be used to decrease the conductivity of highly ionic solutions and increase their heating rate in a concentration-dependent manner. Most of the substances tested for RF heating enhancement are widely available, inexpensive, and are generally considered safe, making them highly attractive for clinical use, although their delivery in high concentrations is potentially a significant obstacle. Such high concentrations could be achieved by percutaneous arterial injection into the local tumor vasculature, similar to the well-known and clinically available technique of arterial chemo-embolization. Given the clear relationship between heating rate and conductivity for any aqueous system, any research team with a permittivity analyzer or even a simple DC conductivity probe can now explore and identify new materials for RF heating enhancement without the need of a complex RF system. RAY H. BAUGHMAN, CHAIR AT-0029, The University of Texas at Dallas.
Welch Chair support helped enable 18 refereed publications and two additional accepted papers during the report period, including four in journals published by Nature. Also, Welch Chair support helped enable research leading to the issuance of a US patent on nanofiber actuators and strain amplifiers and various foreign patent allowances, as well as patent applications for our Incandescent Tension Anneal Process (ITAP) for strengthening carbon nanotube yarns, artificial muscle based technologies for comfort adjusting clothing, and novel carbon nanotube composites. The Welch Chair supported NanoExplorer high school students (about 35 strong in the program year), our undergraduate students, and our outreach events at the Perot Museum of Nature and Science and elsewhere. Welch Chair seed funding was leveraged to obtain NanoTech Institute funding from the United States Air Force, the United States Navy, NASA, the US Korea NBIT III program, and NSF. As a partial result of accomplishments made using Welch Chair funding, Baughman was made a foreign member of the European Academy of Sciences and a Fellow of the National Academy of Inventors in 2015, when he also received the Tech Titans Technology Inventors Award, the Inventor Award for Energy Harvesting Materials and Systems, and shared the R&D 100 Gold Award for Market Disruptor Product. TADHG P. BEGLEY, CHAIR A-0034, Texas A&M University. Riboflavin catabolism: We have identified a riboflavin catabolic operon in a bacterial strain isolated from the DSM riboflavin production plant in Germany. We have overexpressed each of the proteins and identified a riboflavin lyase as the first step in the pathway. We are at an advanced stage in the structural and mechanistic characterization of this enzyme. Our experimental data support a mechanism in which reduced flavin mononucleotide reacts with oxygen to generate superoxide, which then triggers the lyase reaction by abstracting a hydrogen atom from C1 of riboflavin. This is a new mechanistic motif in flavoenzymology.
Folate catabolism: Using bioinformatics and an understanding of the chemical logic of metabolism, we have identified the complete bacterial folate catabolic pathway. We have overexpressed and biochemically characterized the enzymes involved. The pathway involves initial deamination of folate followed by a flavin-mediated oxidation to give xanthine, which is then recycled into purine biosynthesis. The required flavoenzyme is novel and is under further study.
Menaquinone biosynthesis by the futalosine pathway: Our studies have focused on characterizing the mechanism of MqnE. This enzyme catalyzes the addition of the adenosyl radical to dehydrated chorismate followed by rearrangement. Our most interesting recent results center around demonstrating that this reaction proceeds via an aryl radical anion intermediate.
Dibenzothiophene catabolism: Dibenzothiophene is a major source of organic sulfur in petroleum. We have reconstituted the entire catabolic pathway and focused our attention on the flavoenzyme that degrades dibenzothiophene sulfone. Our studies on this enzyme have uncovered a mechanism that involves the formation of a flavin N5-oxide. Only one other example of this flavin oxidation state has been uncovered to date.
Vitamin 612/radical SAM catalyzed methylation reactions: We have reconstituted the CysS-catalyzed methylation of 4-amino-3-methoxybenzoic acid thioesters. This reaction is remarkable in that the enzyme catalyzes iterative radical mediated methylations in which the methyl group of the substrate is converted first to ethyl, then to isopropyl and finally to tert-butyl. Mechanistic studies are in progress.
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WESTON T. BORDEN, CHAIR B-0027, University of North Texas During the past year, part of my group's research has continued to involve an ongoing collaboration with Dr. Xue-Bin Wang at PNNL. His group measures the negative ion photoelectron spectroscopy (NIPES) of anions; and my group carries out calculations that allow us to analyze his NIPE spectra, thus providing information about the electronic structures of the neutral molecules that are formed by electron photodetachment. During this past year, we analyzed the NIPE spectrum of CO3
- and showed the spectrum indicates that neutral CO3 has a singlet ground state with a singlet-triplet energy separation of ∆EST = -17.8 kcal/mol. Based on the vibrational structure in the NIPE spectrum, we were able to identify which of the two, nearly degenerate, triplet, excited states is lower in energy in CO3. In contrast to the case in CO3, we predicted that electron detachment from H2CCO2
- should lead to a diradical with a triplet ground state. We also showed that electron detachment from N2P3
- leads to a radical with a a ground state; but, in contrast, a radical with n ground state is formed by electron detachment from HCNP3
-. I performed calculations on the fragmentation of (CO)5 to five molecules of CO and explained why this orbital-symmetry allowed reaction is
calculated to have a very high barrier and is predicted to proceed in a step-wise fashion. 1 authored a review of tunneling by carbon in organic reactions, a topic about which my group has published many papers in previous years; and I coauthored a manuscript that explains why in both ally! and benzyl, the barriers for CH2 rotation are substantially higher for the cations than for the anions and smallest for the radicals. Finally, I participated in very high-level, ab initio study of (CO)4. The calculations found, in agreement with previous experiments, that this molecule has a triplet ground state. ALAN H. COWLEY, CHAIR F-0003, The University of Texas at Austin. During this grant period we have pursued the synthesis of both nickel and cobalt complexes for the purposes of studying multiple electron transfers in metal complexes, as well as for multi-electron redox transformations such as the reduction of carbon dioxide (CO2) to carbon monoxide (CO), methanol (CH3OH) and methane (CH4). To do this, we have employed two types of ligands with extended conjugation in their backbones, which include the BIAN-type ligand and also a phenanthrene-dione type ligand. We have structurally characterized several of the nickel-containing phananthrene complexes. We have also explored the utility of III-V semiconductors for both novel electronic properties (boron arsenide, BaS) and their ability to convert light into chemical potentials that can be harnessed for energy-related transformations. RICHARD M. CROOKS, CHAIR F-0032, The University of Texas at Austin. We have been working to understand correlations between the atomic-level structure and the energetics of electrochemical reactions, including the oxygen reduction reaction (ORR) and carbon monoxide oxidation, catalyzed by nanoparticles. We have performed experiments that are guided by theory and that have been used to test the predictions of our calculations and assess the accuracy of the corresponding models.
We continue our research on the understanding the underlying principles governing energy-efficient Electrochemically Mediated Membrane-Free Separations (EMMS). We are particularly interested in applying this method to energy efficient desalination. Our current emphasis is on: (1) understanding how ion depletion zone formation by Cl- oxidation can be utilized for EMMS and (2) developing photodriven EMMS to further lower the energy requirements for separation/desalination.
We are developing the basic science that will lead to a new family of low-cost sensors for home healthcare. The approach is based on silver nanoparticle-based detection of targets in blood. Our current focus is on detection of picomolar concentrations of NT-proBNP, which is a marker for congestive heart failure (a disease that affects >5M people in the U.S. alone).
Finally, we are studying fundamental principles of collisions between individual nanoparticles and electrode surfaces. OLAFS DAUGULIS, CHAIR E-0044, University of Houston. We have introduced arylphosphinic acid aminoquinoline amides as competent substrates for cobalt-catalyzed sp2 C-H bond functionalization. Specifically, the feasibility of their coupling with alkynes, alkenes, and ally' pivalate has been demonstrated. Reactions are catalyzed by simple Co(NO3)2 hydrate in ethanol or mixed dioxane/tBuOH solvent in the presence of Mn(OAc)3 additive, sodium pivalate, or acetate base, and use oxygen from the air as an oxidant. Directing group removal affords ortho-functionalized P,P-diarylphosphinic acids. We have developed an operationally simple and general method for copper-catalyzed, aminoquinoline-assisted amination of β-C(sp2)-H bonds of benzoic acid derivatives. The reaction employs Cu(OAc)2 or (CuOH)2CO3 catalysts, an amine coupling partner, pyridine or pyridine/DMSO solvent, and oxygen from air as a terminal oxidant. Significant differences from earlier methods for C-H/N-H couplings include utilization of an inexpensive first-row transition metal catalyst in conjunction with air oxidant and high generality with respect to amine coupling partners. Specifically, primary and secondary aliphatic and aromatic amines, heterocycles, such as indoles, pyrazole, and carbazole, sulfonamides, and electron-deficient aromatic and heteroaromatic amines as well as guanidines are competent coupling components. This is the most general method to-date for directed C-H bond amination. In collaboration with Dr. Brookharts' group, we have shown that 8-arylnaphthyl groups incorporated into pyridine-imine nickel catalysts that block only a single axial site are highly effective in retarding chain transfer. These catalysts produce branched polyethylene (ca. 30 - 90 branches per 1000 carbons) with Mr, values up to 2.6 x 104 g/mol. Effects on the catalyst lifetimes and polymerization behavior as a function of substituent variations at the imine carbon and the aryl group were reported.
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LUIS ECHEGOYEN, CHAIR AH-0033, The University of Texas at El Paso. This report covers the progress made since July, 2015. Welch Foundation support was acknowledged in 18 publications in last year's report and this year we acknowledge 20 new articles, ranging in research topic from empty and endohedral fullerene functionalization to Solar Cells. Three of these articles were published in J. Am. Chem. Soc., one in Angew. Chem. Int. Ed. Eng., two in Chem. Eur. J., and one in Chem. Commun.
In the interest of brevity, we only highlight the results reported in a couple of the articles acknowledged. Bis-functionalization of M3N@C80 via 1,3-dipolar cycloadditions led to a surprisingly low number of regioisomeric bis-pyrrolidine derivatives (only 3 for M=Sc and 2 for M=Lu), out of a statistically possible 91 in both cases!. The conclusion is that the endohedral clusters strongly control the regiochemistry of the exohedral additions, which was explained, using DFT calculations, by increased pyramidalization of some selected cage carbons caused by the encapsulated clusters.
We also synthesized and characterized a new endohedral fullerene, Sc2C2@C2v(9)-C86, which contains a uniquely planar and twisted Sc2C2 unit with remarkable crystalline order in an unprecedented carbon cage, C2V(9)-C86, which obeys the Isolated Pentagon Rule.
J. RUSSELL FALCK, CHAIR I-0011, The University of Texas Southwestern Medical Center. In synthetic methodology, we reported the iron catalyzed acylative cleavage of cyclic and acyclic ethers using acyl/aroyl chlorides resulting in chloroesters and esters, respectively. The mechanism of ether cleavage was proposed to involve a single electron initiated SN1 dissociative pathway. In a series of collaborative studies, we described: (1) that 20-hydroxyeicosatetraenoic acid (20-HETE) helped protect the kidney from ischemia-repurfusion injury in a Dahl salt-sensitive rat model; (2) pharyngeal pumping in C. elegans was stimulated by addition of 17,18-epoxyeicosatetraenoic acid (17,18-EEQ) and decreased by 20-HETE suggesting these metabolite function as second messengers; (3) an orally active EET analog did not exhibit antihypertensive nor have reno- and cardio-protective actions in two-kidney, one clip Goldblatt hypertensive rats; (4) angiotensin II receptor blockade or deletion of vascular endothelial angiotensin converting enzyme (ACE) does not prevent vascular dysfunction and remodeling in 20-HETE-dependent hypertension; (5) interlobular arteries from 2-kidney, 1-clip Goldblatt hypertensive rats exhibit impaired vasodilator response to epoxyeicosatrieneoic acids (EETs); (6) increased expression of PPARα/β/γ and RXRα as well as a decrease in AP-1 and importin-a3 expression/activity comntributes to the protective effect of the stable 20-HETE agonist 5,14-HEDGE against hypotension, tachycardia, and inflammation during endotoxemia; (7) the endothelial growth factor midkine regulates EET levels and thereby influences blood pressure; (8) the stable EET mimetic EET-A mitigates kidney injury in a rat model of radiation nephropathy; and (9) the physiologic and pathophysiologic relevance of the arachidonic acid monooxygenase were reviewed. CHARLES P. FRANCE, CHAIR AQ-0039, The University of Texas Health Science Center at San Antonio. We have identified and are characterizing combinations of opioid receptor agonists and cannabinoid receptor agonists that have robust antinociceptive (analgesic) effects with little or no abuse or dependence liability. These combinations could replace the current wide-spread use of opioid receptor agonists alone (e.g., OxyContin) for training moderate to severe pain, thereby addressing the continuing public health challenge associated with the overuse, abuse, and toxicity (overdose of death) of prescription opioids. Dopamine systems mediate many of the abuse-related effects of drugs and serotonin systems can modulate dopamine neurotransmission. Recent studies in our laboratory suggest that the FDA-approved anti-obesity drug lorcaserin (Belviq®), which acts at serotonin 2C receptors, reduces the rewarding effects of cocaine and methamphetamine. Promising results from our laboratory with non-human primates has prompted the initiation of a clinical trial with lorcaserin in cocaine abusers. Other relevant accomplishments during the current year include hosting a highly successful BBC meeting, renewal of an NIH T32 grant that supports a postdoctoral training program in addiction at UTHSCSA, and initiation of a new center of excellence in addiction. ANDREW FUTREAL, CHAIR G-0040, The University of Texas M. D. Anderson Cancer Center.
We have continued to leverage this important funding for generating groundwork data on rare cancers, particularly sarcoma in close collaboration with the Dept. of Sarcoma. This includes work on RNA sequencing in desmoplastic small round cell tumor, a very rare sarcoma primarily affecting young boys with a particularly dismal prognosis that is leading to insights that may prove to have clinical impact. Further, we have been focusing on generating comprehensive molecular phenotype data in several cancer types in the context of longitudinal analyses of patients' cancers. We know that tumors adapt and change over time and under therapy. A key facet to understanding tumor evolution and adaptive responses to therapy is the capability to molecularly profile cancers over time. The Welch funding has allowed us to develop research in several tumor types that are beginning to yield real insights. Excitingly, we are working on understanding the determinants of response and resistance to highly active immunotherapies in metastatic melanoma. As witnessed by our recent publication in Cancer Discovery, these efforts are beginning to yield insights that will allow us to better target these potentially curative therapies to those patients who are most likely to realize clinical benefit. Further, in keeping with this same theme, we have been collaborating with our clinical colleagues in Stem Cell Transplant in studying a leukemia patients how have undergone stem cell and donor lymphocyte cellular-based therapies, another kind of immunotherapy. Again, the key approach and where we have leveraged the Welch funding, is in longitudinal analyses. We have data developing on multiple chronic lymphocytic leukemia patients over multi-year time frames showing dramatic evolution and immune attack on the subclonal makeup of the CLL. These data are currently being written for publication. Lastly, we have embarked on a unique and ambitious project of fully reconstruct a human cancer at the level of molecular heterogeneity at the genomic, transcriptomic (gene expression), protein signaling, immune and microenviromnent characterization. This will allow us, for the first time, to study the entire ecosystem of a human cancer and its heterogeneity.
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The Welch Chair support has been so important in getting nascent ideas, pilot projects and exploratory approaches off the ground. In particularly, we have been championing rare cancer work, longitudinal analyses in the context of immunotherapies and ambitious approaches to truly understanding tumor heterogeneity. I think having this type of generous funding available to help establish collaborations, get projects going and bolster ideas has made a significant difference in shaping what my lab, the department and, I have confidence, the institution can do. VADIVEL GANAPATHY, CHAIR BI-0028, Texas Tech University Health Sciences Center.
I wrote an invited review for the Biochemical Journal on a novel class of tumor suppressors, namely SLC transporters. There are four of these transporters that have been shown to function as tumor suppressors: SLC5A8, SLC22A18, SLC26A3, and SLC39A1. Among these, SLC5A8 is the most important because its tumor-suppressive role has been demonstrated in every cancer type that has been examined to date: colon cancer, breast cancer, lung cancer, prostate cancer, pancreatic cancer, gastric cancer, kidney cancer, brain cancer, head and neck cancer, and leukemia. Our studies have shown that the ability of this transporter to mediate active concentrative uptake of butyrate, propionate, and pyruvate, all three of which are inhibitors of histone deacetylases, is the molecular basis of its tumor-suppressive function in all tissues. This review has been published recently (SLC transporters as a novel class of tumor suppressors: Identity, function and molecular mechanisms. Biochemical Journal 473: 1113-1124, (2015). I have the expertise in the area of colonic bacteria and their relevance to colonic health and also in tumor-cell-specific metabolism. Based on this expertise, I have been invited by two journals to comment on recently published articles from other investigators, one in the journal Immunity and other in the journal Biochemical Journal. The immunity paper linked gut microbiota to the progression of autoimmune diseases in the brain via the bacterial fermentation products called short-chain fatty acids. I wrote a commentary on this article that was published along with the article (Short, but smart: SCFAs train T cells in the gut to fight autoimmunity in the brain. Immunity 43: 629-631, (2015). The article in the Biochemical Journal focused on the molecular basis of the antitumor activity of a drug called Lonidamine. I wrote a commentary on this article emphasizing the different molecular targets of this drug with regard to their relevance to tumor cell proliferation and growth. Again, my commentary was published along with the article in the journal (Reprogramming tumor cell metabolism to treat cancer: no lone target for lonidamine. Biochemical Journal 473: 1503-1506, (2016) JAN-ÅKE GUSTAFSSON, CHAIR E-0004, University of Houston. The etiology of peripheral squamous cell lung cancer (PSCCa) remains unknown. Here, we show that this condition spontaneously develops in mice in which the genes for two oxysterol receptors, Liver X Receptor (LXR) α (Nr1h3) and β (Nr1h2), are inactivated. By one year of age most of these mice have to be euthanized because of severe dyspnea. Starting at three months, the lungs of LXRα,βDko mice, but not of LXRα or LXRβ single knockout mice, progressively accumulate foam cells, so that by one year the lungs are covered by a "golden coat". There is infiltration of inflammatory cells and progressive accumulation of lipid in the alveolar wall, type 2 pneumocytes, and macrophages. By 14 months there are multiple histological lesions resembling adenomatous hyperplasia, squamous metaplasia and p63, Sox2, CK14 and CK13 positive, CK8, TTF1 and pro-SPC negative squamous cell carcinoma. RNA seq analysis at twelve months confirmed a massive increase in markers of M1 macrophages and lymphocytes. The data suggest a novel etiology of PSCCa: cholesterol dysregulation and M1 macrophage-predominant lung inflammation combined with damage to and aberrant repair of lung tissue, particularly the peripheral parenchyma. The results raise the possibility that components of the LXR signaling may be useful targets in the treatment of PSCC. WILLIAM L. HASE, CHAIR D-0005, Texas Tech University.
Progress was made in the development of models, algorithms, and computer programs for chemical dynamics simulations, and in the application of this software to research problems of significant chemical interest. The Hase research group continues to develop the VENUS computer program for performing chemical dynamics simulations and significant progress was made in maintaining a web-based portal for this software, which will make it very accessible and easy to use by other research groups and scientists. The portal includes a repository of all the models the Hase research group has used for their simulations. The Hase research group also develops, maintains, and distributes the VENUS/NWChem software package for direct dynamics simulations. The specific research problems reported here are: 1) effect of microsolvation on chemical reaction dynamics; 2) dynamics of gas-phase SN2 reactions; 3) properties of a zwitterionic organosodium compound; 4) development of algorithms and software for chemical dynamics simulations (including direct dynamics); 5) theory of unimolecular and intramolecular reaction dynamics; 6) intermolecular potentials and dynamics for collisions of peptide ions with organic surfaces; 7) intermolecular energy transfer in gas phase collisions; 8) product branching in post-transition state dynamics; 9) synthesis of organic molecules in the interstellar medium; and 10) collision-induced dissociation (CID) of peptide ions. ALLAN J. JACOBSON, CHAIR E-0024, University of Houston.
Synthesis and Characterization of Novel Organic Frameworks: Metal-organic and covalent organic frameworks are porous materials characterized by outstanding thermal stability, high porosities and modular synthesis. Their repeating structures offer a great degree of control over pore sizes, dimensions and surface properties. We have extended previous studies of the nanoporous frameworks VO(bdc), MIL-47, and M(OH)(bdc), MIL-53; bdc = 1,4-benzenedicarboxylate, that can absorb various guest species in their channels. As synthesized, the channels are filled with disordered H2bdc molecules except for [In(OH)bdc](H2bdc)n with n=3/4, which has an inorganic-organic hybrid Vernier structure with the H2bdc molecules forming an ordered sublattice. Based on X-ray data from large single crystals grown by hydrothermal techniques, similar Vernier structures have been found for MIL-47, n = 5/7, MIL-53AI n= 11/16, and MIL-53Ga n= 12/17. The Vernier structures were determined based on superstructure unit cells that index both host and guest sub-lattices The number of guest H2bdc molecules per framework metal ion is determined by the ratio of the repeat distances of the two sub-lattices which depends on the size
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of the metal ion in the octahedral chain. We have also studied deformation of the MIL-47 framework upon absorption of carbon disulfide, tetrahydrothiophene, thiomorpholine and thioxane by single crystal X-ray diffraction.
Solid State Ionics: The structure and properties of mixed conducting oxides in thin film and bulk form are investigated. Non-stoichiometric oxides which rapidly and reversibly release and take-up oxygen molecules are of interest as oxygen storage materials for use in a variety of hydrocarbon oxidation reactions. We have extended our previous study of the A-site ordered double-perovskite oxide, YBaMn2O5+δ to compositions containing other rare earth cations, specifically LnBa Mn2O5+δ (Ln = Gd, Pr), to investigate and understand the effect of A site cation substitution on the oxygen storage properties. The results show that changing the Ln cation strongly influences the oxidation/reduction behavior. From thermogravimetric analysis data, oxygen uptake begins at lower temperatures in air in compounds with Ln3+ ions larger than Y3+. These oxides exhibit almost complete and reversible oxygen uptake/release between fully-reduced LnBaMn2O5 and fully-oxidized LnBaMn2O6 during changes of pO2 between air and 2%H2/Ar. In addition, the oxygen non-stoichiometries of GdBa Mn2O5+δ and PrBa Mn2O5+δ were determined as a function of pO2 at 600, 650, 700 and 750 °C by Coulometric titration at near-equilibrium conditions. Three distinct phases occur on oxidation/reduction with 5 = 0, 0.5 and ~6. Isothermal experiments show that the larger the Ln3+ cation the lower pO2 for phase conversion. At some temperatures and pO2 conditions, the LnBa Mn2O5+δ compounds are unstable with respect to decomposition to Ba O3+δ and LnMnO3. MICHAEL J. KRISCHE, CHAIR F-0038, The University of Texas at Austin.
Be it commodity chemicals, pharmaceutical ingredients, agrochemicals or flavor fragrance compounds, C-C bond formation lies at the heart of chemical synthesis. The Krische group has pioneered a broad, new class of C-C bond formations that merge the characteristics of catalytic hydrogenation and carbonyl addition. These processes may be viewed as an outgrowth of hydroformylation ‒ the largest volume application of homogenous metal catalysis. Two reaction types have been developed: (a) "C-C Bond Forming Hydrogenations" wherein 7-unsaturated reactants are exposed to carbonyl and imine partners in the presence of gaseous hydrogen to form products of reductive coupling, and (b) "C-C Bond Forming Transfer Hydrogenations" wherein hydrogen exchange between alcohols and Tr-unsaturated reactants delivers aldehyde-organometal pairs that engage in carbonyl addition, thereby converting lower alcohols directly to higher alcohols. Both reactions types merge redox and C-C bond construction events, and bypass the use of intrinsically hazardous stoichiometric organometallic reagents.
In the 2015-2016 funding period, numerous advances were made. One of the most exciting discoveries involves the catalytic enantioselective C-C coupling of alcohols with propargyl ethers to form secondary homoallylic alcohols. This byproduct-free C-C bond formation can be conducted using either ruthenium catalysts (J. Am. Chem. Soc. 2015, 137, 13066) or iridium catalysts (J. Am. Chem. Soc. 2015, 137, 16024) and occurs through a novel mechanism involving hydride shift enabled 7-ally) formation. Using simple ruthenium-BINAP catalysts, enantioselective C-C couplings of alcohols with 1,3-enynes were developed (J. Am. Chem. Soc. 2016, 138, 5238). Additionally, enantioselective C-C couplings of racemic allylic acetates with formaldehyde were achieved using iridium catalysts (J. Am. Chem. Soc. 2016, 138, 3655). Our collective studies were described in several review articles, including a prestigious invited "perspective" article published in the Journal of the American Chemical Society (J. Am. Chem. Soc. 2016, 138, 5467) describing how we have applied our catalytic methods to the synthesis of polyketide natural products. JAMES C. LEE, CHAIR H-0013, The University of Texas Medical Branch. The 20 BMPs are members of the transforming growth factoril (TGF-(3) superfamily. Their biological activities are diverse, including cell differentiation, embryonic development. etc. BMPs have been shown to bind four mammalian type I and three type II BMP-receptors (BMPR) with different affinities. possibly as a hetero-tetrameric complex e.g. (2BMP)o(BMPR-1;BMPR-11). Hence. there are many different pathways to form the complex involving many protein-protein interactions (PPI) characterized by different affinities eliciting different functions. Since the clinical literature reported that either excessive or repressed expression of BMPs can induce human diseases. a potential mechanism to overcome the aberrant effect is to modulate quantitatively protein-protein interface (PPI). Our approach is to identify a novel allosteric ligand-binding site, an advantage of which is to bypas., the potential challenges in competing for high affinity interfacial interactions, as the allosteric site is situated away from but functionally connected to the PP1. Applying the COREVBEST computational algorithm, we uncovered an overall pattern connecting various regions of BMPR-1B ecto-domain (BMP Receptor 1B ECD) including the four conserved residues among all BMP 1 and 11 receptors in the PPI. Experimental results of Ala scanning of the 4 conserved residues in PPI show that each residue plays a different role in defining ligand affinity for F1MP-2, -6. -7 and GDF-5. The algorithm also has identified a network of long-rave residues connected to PPI consisting distal residues which can thermodynamically stabilize (e.g.R77A) or destabilize (e.g.D37A) the PPI. respectively. Thus, we chose these two mutants among six to conduct preliminary binding and cellular activity tests in response to BMP-7. The most encouraging, though preliminary, results showed that these mutants exhibit allosteric effects on both in vitro BMP-7 binding and cellular activity in opposite directions. Encouraged by these results, we continue to 1) define the quantitative impact of residues in the long-ranee network in modulating PP1. They have different effects on stability on the PP1. The chosen mutants: e.g.L97A>Q77A>R76A: G60A>1.61A>D37A. K20A, C2I A (destabilizes PPI), E46A and D47A (destabilizes and stabilizes locally 1.n.; at., effect on PM). Double mutant R76A1)77A will be tested for their predicted opposing effects on PPI to evaluate the magnitude of cross-talk between these residues: 2) define the quantitative correlation between energetics of structural coupling and thermodynamics of PPI: 3) elucidate the structures and dynamics of mutant BMPR 1B in apo and complexed forms of BMP-IB with BMPs by X-ray crystallography.
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BETTIE SUE MASTERS, CHAIR AQ-0012, The University of Texas Health Science Center at San Antonio. Mutations in human cytochrome P450 oxidoreductase gene (POR) are associated with severe skeletal deformities, disordered steroidogenesis, and ambiguous genitalia. More than 200 mutations in the POR gene have been reported in both introns and exons, many of which are associated with POR deficiency disorder. In pursuing studies of human mutations of NADPH-cytochrome P450 reductase, the Masters laboratory has expressed more than a dozen of these mutations in E. coli and characterized their properties at the molecular level. The most common mutation in Caucasians, A287P, was recently reported by another group to exhibit flavin deficiency. However, in our hands, the purified variant enzyme is fully complemented with FAD and FMN and exhibits similar activities with different cytochromes P450 (such as CYP17, CYP19 and CYP21, critical for steroid hydroxylation) in vitro but, uniquely, it cannot be purified by the same process applied to the other dozen reductase polymorphic variants. In collaboration with Dr. Jung-Ja Kim, with whom we reported the first crystal structures of both rat and human reductases, we observed that the crystal structures of WT and A287P differ, as well as their susceptibility to trypsinolysis. The A287P variant is also degraded faster than WT reductase in MC 3T3 osteoblast cells into which each has been stably transfected. Compared to the wild type enzyme, the A287P variant is very sensitive to trypsinolysis and is protected by the addition of 2'-AMP, an analog of NADPH. These properties of the A287P mutation in P450 reductase have led to the conclusion that its instability in the in vivo environment could result in the disease phenotype. DAVID D. MOORE, CHAIR Q-0022, Baylor College of Medicine. We have continued to focus on the roles of nuclear receptors in cell stress pathways. We reported that mice lacking the nuclear receptor LRH-1 in the liver show increased sensitivity to endoplasmic reticulum (ER) stress. We asked whether this is evolutionarily conserved. NHR-25 is the homolog of LRH-1 in the nematode C. elegans, and we found that NHR-25 is indeed required for resistance to ER stress. Surprisingly, the NHR-25 dependent pathway for ER stress resolution is quite different from the LRH-1 pathway that we initially uncovered in mice. However, further studies revealed that this pathway is also present in mice, and we are preparing to resubmit a manuscript that describes this new, evolutionarily conserved pathway for cell stress response.
We have also recently studied the impact of a very different chemical stress on nuclear receptor function. In Wilson's disease, copper transport is defective and Cu++ accumulates to high levels in hepatocytes. The structure of the DNA binding domains of the nuclear receptors depends on the presence of 2 bound Zn++ atoms. Previous biochemical studies have shown that Cu++ can readily replace Zn++, but the resulting complex cannot bind to DNA. We have confirmed these results in vitro and in cultured cells, and have reported that hepatic nuclear receptor function is impaired in a mouse model of Wilson's Disease.
We have previously studied the function of the nuclear bile acid receptor FXR, primarily in mice. During the last year we reported on the consequence of loss of FXR function in humans. We identified four patients in two families with complete loss of functional FXR, which resulted in severe neonatal cholestasis. Two patients survived after liver transplants, while the other two died before a year of age. All four patients had severe coagulopathy. This is not associated with other genetic forms of intrahepatic cholestasis, and we attributed this unexpected finding to a direct role of FXR as an activator of the complement and coagulation cascades. ERIC N. OLSON, CHAIR I-0025, The University of Texas Southwestern Medical Center.
Conversion of fibroblasts to functional cardiomyocytes represents a potential approach for restoring cardiac function after myocardial injury, but the technique thus far has been slow and inefficient. To improve the efficiency of reprogramming fibroblasts to cardiac-like myocytes (iCMs) by cardiac transcription factors [Gata4, Hand2, Mef2c, and Tbx5 (GHMT)], we screened 192 protein kinases and discovered that Akt/protein kinase B dramatically accelerates and amplifies this process in three different types of fibroblasts. Approximately 50% of reprogrammed mouse embryo fibroblasts displayed spontaneous beating after 3 wk of induction by Akt plus GHMT. Furthermore, addition of Akt1 to GHMT evoked a more mature cardiac phenotype for iCMs, as seen by enhanced polynucleation, cellular hypertrophy, gene expression, and metabolic reprogramming. Insulin-like growth factor 1 (IGF1) and phosphoinositol 3-kinase (P13K) acted upstream of Akt whereas the mitochondrial target of rapamycin complex 1 (mTORC1) and forkhead box o3 (Foxo3a) acted downstream of Akt to influence fibroblast-to-cardiomyocyte reprogramming. These findings provide insights into the molecular basis of cardiac reprogramming and represent an important step toward further application of this technique.
CRISPR/Cas9-mediated genome editing holds clinical potential for treating genetic diseases, such as Duchenne muscular dystrophy (DMD), which is caused by mutations in the dystrophin gene. To correct DMD by skipping mutant dystrophin exons in postnatal muscle tissue in vivo, we used adeno-associated virus-9 (AAV9) to deliver gene-editing components to postnatal mdx mice, a model of DMD. Different modes of AAV9 delivery were systematically tested, including intraperitoneal at postnatal day 1 (P1), intramuscular at P12, and retro-orbital at P18. Each of these methods restored dystrophin protein expression in cardiac and skeletal muscle to varying degrees, and expression increased from 3 to 12 weeks after injection. Postnatal gene editing also enhanced skeletal muscle function, as measured by grip strength tests 4 weeks after injection. This method provides a potential means of correcting mutations responsible for DMD and other monogenic disorders after birth.
Genomic editing has revolutionized the generation of mutant animals by simplifying the creation of null alleles in virtually any organism. However, most current approaches with this method require zygote injection, making it difficult to assess the adult, tissue-specific functions of genes that are widely expressed or which cause embryonic lethality when mutated. We generated cardiac-specific Cas9 transgenic mice, which express high levels of Cas9 in the heart, but display no overt defects. In proof-of-concept experiments, we used Adeno-Associated Virus 9 (AAV9) to deliver single- guide RNA (sgRNA) that targets the Myh6 locus exclusively in cardiomyocytes. Intraperitoneal injection of postnatal cardiac-Cas9 transgenic mice with AAV9 encoding sgRNA against
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Myh6 resulted in robust editing of the Myh6 locus. These mice displayed severe cardiomyopathy and loss of cardiac function, with elevation of several markers of heart failure, confirming the effectiveness of this method of adult cardiac gene deletion. Mice with cardiac-specific expression of Cas9 provide a tool that will allow rapid and accurate deletion of genes following a single injection of AAV9-sgRNAs, thereby circumventing embryonic lethality. This method will be useful for disease modeling and provides a means of rapidly editing genes of interest in the heart.
The Mediator complex governs gene expression by linking upstream signaling pathways with the basal transcriptional machinery. However, how individual Mediator subunits may function in different tissues remains to be investigated. Through skeletal muscle-specific deletion of the Mediator subunit MED13 in mice, we discovered a gene regulatory mechanism by which skeletal muscle modulates the response of the liver to a high-fat diet. Skeletal muscle-specific deletion of MED13 in mice conferred resistance to hepatic steatosis by activating a metabolic gene program that enhances muscle glucose uptake and storage as glycogen. The consequent insulin-sensitizing effect within skeletal muscle lowered systemic glucose and insulin levels independently of weight gain and adiposity and prevented hepatic lipid accumulation. MED13 suppressed the expression of genes involved in glucose uptake and metabolism in skeletal muscle by inhibiting the nuclear receptor NURR1 and the MEF2 transcription factor. These findings reveal a fundamental molecular mechanism for the governance of glucose metabolism and the control of hepatic lipid accumulation by skeletal muscle. Intriguingly, MED13 exerts opposing metabolic actions in skeletal muscle and the heart, highlighting the customized, tissue-specific functions of the Mediator complex.
During skeletal muscle development, myoblasts fuse to form multinucleated myofibers. Myomaker Transmembrane protein 8c (TMEM8c)] is a muscle-specific protein that is essential for myoblast fusion and sufficient to promote fusion of fibroblasts with muscle cells; however, the structure and biochemical properties of this membrane protein have not been explored. We used CRISPR/Cas9 mutagenesis to disrupt myomaker expression in the C2C12 muscle cell line, which resulted in complete blockade to fusion. To define the functional domains of myomaker required to direct fusion, we established a heterologous cell-cell fusion system, in which fibroblasts expressing mutant versions of myomaker were mixed with WT myoblasts. Our data indicate that the majority of myomaker is embedded in the plasma membrane with seven membrane-spanning regions and a required intracellular C-terminal tail. We show that myomaker function is conserved in other mammalian orthologs; however, related family members (TMEM8a and TMEM8b) do not exhibit fusogenic activity. These findings represent an important step toward deciphering the cellular components and mechanisms that control myoblast fusion and muscle formation. Muscle contraction depends on release of Ca(2+) from the sarcoplasmic reticulum (SR) and reuptake by the Ca(2+)adenosine triphosphatase SERCA. We discovered a putative muscle-specific long noncoding RNA that encodes a peptide of 34 amino acids and that we named dwarf open reading frame (DWORF). DWORF localizes to the SR membrane, where it enhances SERCA activity by displacing the SERCA inhibitors, phospholamban, sarcolipin, and myoregulin. In mice, overexpression of DWORF in cardiomyocytes increases peak Ca(2+) transient amplitude and SR Ca(2+) load while reducing the time constant of cytosolic Ca(2+) decay during each cycle of contraction-relaxation. Conversely, slow skeletal muscle lacking DWORF exhibits delayed Ca(2+) clearance and relaxation and reduced SERCA activity. DWORF is the only endogenous peptide known to activate the SERCA pump by physical interaction and provides a means for enhancing muscle contractility. B. MONTGOMERY PETTITT, CHAIR H-0037, The University of Texas Medical Branch. Biomolecular interfaces are of relevance as ligand targets and in aggregation/solubility studies. A decomposition of the solvation thermodynamics for successively longer oligoglycine polypeptides as a function of molecular mechanics force fields was determined. The oligoglycine peptide has been found to be an excellent model of the protein backbone that plays a prominent role in protein packing and folding into specific structure. Details of the free energy and solubility driven protein-protein molecular recognition and interface formation were modelled to characterize the protein-protein recognition and aggregation driving forces. DNA molecules are also usually found in compact conformations or circular conformations that are strongly affected by the DNA-DNA interactions. Circular DNA has been found to be dependent not only on the nucleic acid interactions but also on their identity, i.e. their sequence. Coarse-grained molecular dynamics simulations were used to decipher the role the sequence of a DNA molecule plays on its dynamic properties upon cyclization which is a critical step in cloning technologies. Our calculations identified the types and positions of structural defects during the process of loop formation that correlated well with the experimental data. Our most recent work on the solution properties of proteins, on protein-protein interfaces, protein-DNA recognition, and nucleic acid systems have correlated well with the experimental data and provided insight into the conformational and thermodynamics of the biomolecular systems modelled. LASZLO PROKAI, CHAIR BK-0031, University of North Texas Health Science Center. In the grant year of 2015/2016, I have continued the evaluation of para-quinols of estratrienes as central nervous system-selective bioprecursor prodrugs to treat estrogen-responsive neurological and psychiatric diseases, which I now consider the most impactful part of my Research Objective A. Focusing on the hypothalamus as the thermoregulatory center of the body, a comprehensive evaluation of a potential therapeutic intervention against menopausal hot flushes in animal models was done and published in a Nature journal. My collaborative research also revealed for the first time that treatment with 10β,17β-dihydroxyestra-1,4-dien-3-one (DHED, a brain-selective bioprecursor prodrug of 17β-estradiol) results in a significant improvement of cognitive performance in a double-transgenic mouse model of Alzheimer's disease without peripheral exposure to estrogen. In addition to the already proven intervention involving DHED, we have synthesized and successfully demonstrated in a mouse model of depression that the DHED stereoisomer 10β,17α-dihydroxyestra-1,4-dien-3-one is a brain-selective bioprecursor prodrug of 17α-estradiol. An important contribution to the chemical biology of estrogens has been the identification and verification of estrogen-regulated uterine proteins that can be developed to and used as a potential biomarker panel to screen estrogenic endocrine disrupting chemicals representing concerns regarding public and environmental health. As part of my Research Objective B, I have continued to develop bioassays based on tandem mass spectrometry to measure neurotransmitters and other small molecules of interest in samples obtained through in vivo
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microdialysis, permitting the measurement of their local concentrations in the brain of experimental animals. In particular, we developed a method coupled with high-performance liquid chromatography to measure dopamine (an important neurotransmitter linked to reward) in samples obtained from animals involved in a rodent study investigating feeding-associated behavior in obese animals. Finally, I developed tandem mass spectrometry-based methods to follow the concentration of carisoprodol and its liver metabolite (meprobamate) in the nucleus accumbens region of the rat brain in vivo for the first time to correlate with neuropharmacological actions. This study is to shed light on carisoprodol's activity not related to meprobamate. JAMES C. SACCHETTINI, CHAIR A-0015, Texas A&M University.
Our work continues on key target pathways from M. tuberculosis (Mtb) such as cell wall biosynthesis, intermediary metabolism, and translation. Our longstanding efforts on integrating structure based methods with drug discovery on the mycolic acid biosynthesis, has led to success on the drug target Pks13. Last year we declared a lead molecule that was developed with structure-guided approaches applied to Pks13. The current lead molecule shows low toxicity, good bioavailability, a favorable pharmacological profile, and anti-Mtb activity similar to that of isoniazid in mouse models. In collaboration with Dundee Drug Discovery Unit (DDU), we expect a clinical candidate by late 2016. We have new programs on several targets like gluconeogenesis enzyme PEPCK, branch amino acid synthesis enzymes 11vB and IlvC, central carbon metabolism targets malate synthase, 1cl, MDH, and nucleotide metabolism target AdoK. We have a project, Mtb ribosome, a validated antibiotic target. A high throughput is complete of 11,000 Mtb whole cell actives, provided by GalxoSmithKline. Further, in collaboration with Dr. Junjie Zhang (A-1863), we are working on high resolution EM structure of the Mtb ribosome to complement developing drugs that efficiently inhibit Mtb translation.
We were able to start with a herbicide-based inhibitors of the acetyl CoA carboxylase. We found that many of the compounds were active against an intestinal parasite. Cryptosporidiosis is responsible for significant child mortality in developing countries because currently there are no effective drugs against it. We developed a structure-activity relationship for Cp and have made inhibitors that are extremely potent, several with anti-parasitic activity in the low picomolar range. They show very low toxicity, efficacy in in vivo mouse models of infection, and our current lead is being evaluated in a calf efficacy model right now. We have discovered novel rifamycins that are extremely efficient at sensitizing drug resistant cancers to standard of care chemotherapeutics. Rufabutin analog RTI-79 has a broad spectrum of action that includes ovarian cancer and double and triple hit non-Hodgkin's lymphoma. It increases the sensitivity of resistant ovarian cancer (NCl/ADR-RES) to doxorubicin (DOX) by over 800-fold. In fact, it synergizes with many different chemotherapeutics in various cancers, restoring drug sensitivity. RTI-79 is relatively non-toxic and has favorable in vivo safety and pharmacokinetic profiles. RTI-79 in combination therapies is effective in multiple drug-resistant cancers in mouse models. GUSTAVO E. SCUSERIA, CHAIR C-0036, Rice University. During the past year, we have continued to develop novel quantum chemistry methods. Our focus remains on methodology for both molecules and systems with periodic boundary conditions (surfaces and bulk materials), and it involves both density functional and wavefunction methods. Our main efforts have focused on symmetry breaking and restoration techniques, novel forms of coupled cluster theory, and a quantum embedding theory based on the one-particle density matrix. ERIC E. SIMANEK, CHAIR P-0008, Texas Christian University. Dendrimer synthesis. The synthesis of these molecules is now streamlined to yield large generation products in as little as 24 hours. A study of the fluorescence properties of these materials has been undertaken and will be communicated during the next grant period. Additional reports of linker-development, biocompatibility, and physicochemical behavior were disseminated.
Therapy and diagnostics. The final constructs bearing different therapeutic peptides and diagnostic agent were prepared and evaluated for activity with collaborators from UT Southwestern Medical Center. These materials represent the cutting edge of theranostics from our laboratory. The addition of prostate-specific targeting groups also advanced during this period.
Education efforts. Collaboration with the College of Education led to the dissemination of reports and conference presentations on a tool for teaching food webs. The Pangea Mat & Cutter is still being distributed with current estimates of >200,000 students impacted each year. The Broadway-style show derived from it is still being performed. As this period closes, the publication of a book intended for general audiences is eagerly anticipated. It is entitled "Shots of Knowledge: The Science of Whiskey" with coauthor Rob Arnold. JOHN L. SPUDICH, CHAIR AU-0009, The University of Texas Health Science Center at Houston.
Following our discovery last year of a family of rhodopsins in cryptophyte algae that we named Anion Channel Rhodopsins (ACRs) that carry out a function previously unknown to occur in nature, light-gated channel conduction of anions (Govorunova et al. Science 349:647-650. 2015), we conducted electrophysiology study of one, GtACR1 from Guillardia theta, and several mutated forms in mammalian cells gaining insight into the ACR gating mechanism and identifying residue determinants of events in the gating process by mutagenesis. Next we developed an expression and purification system for GtACR1 and GtACR2 and their mutants for in vitro studies and, by laser flash photolysis and kinetic analysis of mutants, identified steps in the ACR photochemical reaction cycle and their relationship to channel opening and closing. We incorporated the purified GtACR1 into large unilamellar lipid bilayer vesicles establishing a chemically defined system in which both photocurrents and optical and molecular spectroscopic kinetics can be measured in the same system for future work. We identified a third ACR variant in a second cryptophyte species that suggested ACRs might be widespread in cryptophytes. In our further study
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of the genome of the cryptophyte G. theta, in which we had discovered the first two ACRs, we found a family of cation-conducting channelrhodopsins (CCRs) that are structurally distinct from the known CCRs from chlorophyte algae widely used in optogenetics. The cryptophyte CCRs show close sequence homology with rhodopsin proton pumps rather than with the previously known CCRs. The new-type CCRs carry out light-gated passive transport of Na+ like other CCRs, but also exhibit electrogenic H+ pumping, suggesting they may be an evolutionary "missing link" between rhodopsin channels and pumps. JOHN A. TAINER, CHAIR G-0010, The University of Texas M. D. Anderson Cancer Center. Synthetic biology and protein design. We used X-ray scattering spectra to investigate the universe of folded structures and found that it is possible to design novel repeat proteins with precisely specified geometries, opening novel possibilities for biomolecular engineering. We furthermore created and validated design of a 600kDa protein homododecamer cage. We employed high-throughput X-ray scattering (SAXS), and developed force plots that measure dissimilarity among multiple SAXS datasets to generate a phase diagram associating structure and assembly. Reactive oxygen enzymes. The enzymes perchlorate reductase (PcrAB) and chlorite dismutase collectively take perchlorate to innocuous chloride generating free oxygen (02) thereby providing an ancient biological process to generate oxygen aside from photosynthesis as a possible early source of oxygen on earth. We solved structures of oxidized and reduced PcrAB with and without the substrate providing the first detailed insights into biological perchlorate reduction, a critical component of the chlorine redox cycle on Earth. As many radicals are scavenged by dioxygen into superoxide in cells, superoxide dismutase (SOD) enzymes are a master radical regulator. I analyzed high-resolution and X-ray scattering of SOD from bacterial pathogens Neisseria meningitidis (NmSOD) and Brucella abortus (BaSOD). The identified functional contributions, motifs, and targets distinguishing bacterial and eukaryotic SOD assemblies presented here provide a foundation for efforts to develop SOD-specific inhibitors. DNA transcription, replication, and repair responses and their connection to programed cell death. By combining X-ray methods for structure determination and imaging, we revealed molecular steps that turn on bacteria's pathogenic genes: histone-like proteins twist DNA chromatin open and closed to trigger expression of genes that can make a microbe invasive. To better understand chromosomal rearrangements that create oncogenic fusion genes, we analyzed potential non-B DNA forming sequences, and found them associated with cancer translocation breakpoints. For the DNA double strand break (DSB) responses, we defined the activated RNF8-Ubc13 ubiquitin complex by x-ray crystallography and x-ray scattering, as tested by separation-of-function mutations imaged in cells by immunofluorescence. The collective results show that RNF8 targets Ubc13 to DSB sites and plays a critical role in damage signaling by stimulating polyubiquitination through modulating conformations of ubiquitin covalently linked to the Ubc13 active site. These results suggest an allosteric approach to targeting the ubiquitin-docking cleft at the E2-E3 interface for possible interventions in cancer and chronic inflammation. Apoptosis-inducing factor (AIF) is critical for mitochondrial respiratory complex biogenesis and for mediating a form of programmed cell death. We defined molecular pathways linking AIF's active site to allosteric switching regions by characterizing dimer-permissive AIF mutants using small X-ray scattering and crystallography. This knowledge of AIF allostery and its flavoswitch mechanism provides a foundation for biologically understanding and biomedically controlling its participation in mitochondrial homeostasis and cell death. CHERYL LYN WALKER, CHAIR BE-0023, Texas A&M University System Health Science Center.
Epigenome-cytoskeleton Crosstalk While investigating the impact of loss of function of chromatin modifying enzymes in cancer, our group has made the very exciting discovery that these "readers, writers and erasers" of the histone code are also modifying the cytoskeleton. In our paper to be published in Cell in August 2016, we report that a chromatin remodeler, the histone methyltransferase SETD2, which is lost in several types of cancer, has an important, and previously unknown function, rnethylating microtubules. We identify methylation of a-tubulin as a new post-translational modification of microtubules, show it is required for normal chromosome segregation and cytokinesis, and present a new paradigm whereby loss of this histone methyltransferase causes alterations in the cytoskeleton and genomic instability. Our manuscript "Dual Chromatin and Cytoskeletal Remodeling by SETD2" is the first report of a dual function methyltransferase required for integrity of both the epigenome and the cytoskeleton, and linking for the first time the tubulin and histone codes. We believe this manuscript will be seen as a paradigm shift in the fields of epigenetics and cell biology, allowing us to understand diseases such as cancer in exciting new ways. The epigenetic machinery has not previously been linked to the cytoskeleton, and our findings promise to open new frontiers for exploring both normal cell function and disease pathogenesis. While chromatin remodelers are frequently lost in cancer, we have been blind to the fact that their loss may also impact the cytoskeleton. Discovery of a cytoskeletal function for chromatin remodelers opens an entirely new avenue for understanding how loss contributes to cancer etiology via microtubule defects during mitosis, genomic instability, and cytoskeletal defects that enhance motility, migration and metastasis. STEVEN WEINBERG, CHAIR F-0014, The University of Texas at Austin.
During this grant year Steven Weinberg continued his work on the fundamentals of quantum mechanics. He presented a new analysis of the evolution of the density matrix during measurement. Conditions on the operators appearing in the Lindblad equation are given that are necessary and sufficient for the late-time limit of the density matrix to take the form appropriate for a measurement, and an explicit solution of the equation is found under these conditions. This work was published in Phys. Rev. A 93, 032124 (2016). He completed the second edition of his book Lectures on Quantum Mechanics, which was published by Cambridge University Press in 2015. Much of his work in this period was devoted to the preparation of a new course and a new book on astrophysics.
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THEODORE G. WENSEL, CHAIR Q-0035, Baylor College of Medicine.
We have used an algorithm based on evolution and mutual information to identify pairs of arrino acid residues within the D2 dopamine receptor that are functionally coupled to one another. Fluorescencebased assays of downstream G protein signaling have confirmed the utility of the algorithm and the functional coupling of the residue pairs it identifies. We have also found that the fate of mRNA encoded by mutant rhodopsin genes with premature stop codons is correlated with the dominant vs. recessive phenotype of human retinal degeneration caused by these mutations. We have determined that a group III phosphatidylinositol-3-kinase, Vps34 is essential for autophagy, endosome processing, and cell survival in retinal rod photoreceptor neurons. PETER G. WOLYNES, CHAIR C-0016, Rice University. The Bullard-Welch Chair supported trips of groups members working on Welch funded projects as well as participation in meetings by Peter Wolynes. JOHN L. WOOD, CHAIR AA-0006, Baylor University.
The Wood Group is currently comprised of five graduate students and five postdoctoral fellows. Efforts during the past year have focused on the synthesis of seven natural products which are illustrated below and include: A) Phomoidride D; Hippolachnin A; Caseabaiansin A; Longeracemine; Aspergilline A; Tiachunamide A, and; Tetrapetalone A-D. All of the compounds have interesting biological properties and in each case a novel strategy is being developed for the synthesis. Just prior to last year's report the synthesis of hippolachnin was completed. Since that report the synthesis, through a collaborative effort with the Brown group at Indiana, was Improved and the results published. KAREN L. WOOLEY, CHAIR A-0001, Texas A&M University.
A productive research, education and training program involving the design, preparation and study of unique polymer materials is supported by the Welch Foundation grant. The W. T. Doherty-Welch Chair in Chemistry at Texas A&M University supports significant portions of the infrastructure that is directed toward an innovative mission to educate and train a diverse community of scholars (6 undergraduate students, 19 Ph.D. students, four postdoctoral associates, five senior scientists, and one technician), each conducting research to advance the fundamental knowledge and societal application of functional polymer materials. The primary motivation is to extend the synthetic control of organic chemistry toward increasingly complex and functional materials over many dimensions, often by employing hierarchical approaches, and it relies on combinations of organic chemistry, physical chemistry, biology and engineering. Research advances have included well-defined polypeptide-carbon nanotube hydrogel systems that have promise toward flexible and wearable electronic devices, hybrid organic polymer-inorganic magnetic nanoparticle assemblies designed for environmental clean-up that are capable of capturing crude oil with magnetic recovery, extension of shell crosslinked knedel-like nanoparticles as dual imaging and therapeutic delivery vessels for treatment of lung cancer and infectious diseases, anti-biofouling and anti-icing coatings that present surface complexities, and degradable polymers derived from renewable resources and that undergo breakdown to release biologically-beneficial and environmentally-resorbable natural product small molecules. The Welch Foundation chair has been critical to each of these advances, gratefully supporting research efforts that have led to eleven peer-reviewed published articles, three articles in press, and five manuscripts submitted for publication, currently undergoing peer review or revision.
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HONGCAI JOE ZHOU, CHAIR A-0030, Texas A&M University. We reported a facile one-pot synthetic strategy to incorporate multi-functionalities into stable Zr-MOFs through mixing ligands of different geometry and connectivity. Through combinations of BDC derivatives and TCPP ligands, 49 MOFs with multi-functionalities were obtained. Combining the advantages of framework robustness and facile functionalization that allow further chemistry to be explored within the framework, we expect our strategy to provide a facile route to introduce multi-functionalities for an extensive variety of potential applications. We also report an anionic metal‒organic framework, PCN-99, has been synthesized through a topology-guided strategy; its underlying bor-net is realized by the use of a tetrahedral [In(COO)4] node and a judiciously designed trigonal planar linker. In light of its anionic nature, the inherent cuboctahedral cage and 1D channel make PCN-99 an excellent matrix to encapsulate the photocatalytic [Ru(bpy)3]2+. Lastly, we report two metal‒organic frameworks [PCN-426(Ni) and PCN-427(Cu)] have been designed and synthesized to investigate the structure predictability using a SBB (supermolecular building blocks) approach. Tetratopic ligands featuring 120° angular carboxylate moieties were coordinated with a [Ni3(µ3-O)] cluster and a [Cu2O2] unit, respectively. As topologically predicted, 4-connected networks with square coordination adopted the nbo net for the Ni-MOF and ssb net for the Cu-MOF. PCN-426(Ni) was augmented with 12-connected octahedral SBBs, while PCN-427(Cu) was constructed with tetragonal open channels. MISCELLANEOUS GRANTS
K-A-0002, GRADUATE RESEARCH ENDOWMENT GRANT PROGRAM, Texas A&M University. Thirty-six fellowships were offered to superior students that applied to the chemistry graduate program. Of those offered, seventeen accepted and joined the program. Fifteen of these students have met all department exceptions with respect to academic progress and performance. K-C-0003, ATTWELL-WELCH GRADUATE FELLOWS PROGRAM, Rice University. The funds generated from the Attwell-Welch Graduate Research endowed fund were successful in recruiting eight graduate students to the Department of Chemistry and ten graduate students to the Department of Biochemistry and Cell Biology. All students made substantial progress in their studies and provided significant support in the labs in which they work. K-F-0001, GRADUATE RESEARCH ENDOWMENT GRANT PROGRAM, The University of Texas at Austin. Graduate student recruiting expenses included hotel accommodations and airfare for prospective graduate student visits and other miscellaneous expenses. The assistance of the Welch Foundation was instrumental in our success at maintaining a first class program. We have continued our recruiting success with an incoming class of thirty-five students. This success was due in part to the Welch Foundation fellowships we can offer. L-AU-0002, THE WELCH FOUNDATION ENDOWMENT IN CHEMISTRY AND RELATED SCIENCES, The University of Texas Health Science Center at Houston. PRIYATANSH GURHA:
Pathogenesis of fibro-adipogenesis in arrhythmogenic cardiomyopathy (AC) is largely unknown. To elucidate the pathogenic role of microRNAs (miRNAs) in AC we screened 750 miRNAs using low-density microfluidic panels and identified fifty-nine differentially expressed miRNAs in AC. MiR-184 was the most down-regulated miRNA in AC. MicroRNA-184 was predominantly expressed in cardiac mesenchymal progenitor cells (MPCs) in the adult heart. Knock down of Pkp2 in isolated cardiac MPCs reduced miR-184 levels. Expression of miR-184 was transcriptionally regulated by the E2F1 pathway.ln addition, DNMT1 was recruited to the promoter region of miR-184 and the CpG sites at the upstream region of miR-184 were hypermethylated. Pathway analysis of paired miR-184:mRNA targets identified cell proliferation, differentiation, and death as the main affected pathways. Knock down of miR-184 in HL-1 myocytes and MPCs induced and conversely, its over-expression attenuated Adipogenesis. In conclusions we show that miR-184 levels are reduced in cell and mouse models of AC because of suppression of the E2F1 pathway and hypermethylation of the CpG sites at miR-184 promoter. Suppression of miR-184 enhances and its activation attenuates adipogenesis. Thus, miR-184 contributes to the pathogenesis of AC. VIHANG NARKAR:
PROJECT 1: Dissecting exercise-mimicking pathways that can replicate the benefits of exercise in obesity and diabetes may lead to promising treatments for metabolic disorders. Muscle estrogen-related receptor gamma (ERRγ) is induced by exercise, and when over-expressed in the skeletal muscle mimics exercise by stimulating glycolytic-to-oxidative myofiber switch, mitochondrial biogenesis and angiogenesis in lean mice. The objective of this study was to test whether muscle ERRγ in obese mice mitigates weight gain and insulin resistance. To do so, ERRγ was selectively over-expressed in the skeletal muscle of obese and diabetic db/db mice. Muscle ERRy over-expression successfully triggered glycolytic-to-oxidative myofiber switch, increased functional mitochondrial content and boosted vascular supply in the db/db mice. Despite aerobic remodeling, ERRy surprisingly failed to improve whole-body energy expenditure, block muscle accumulation of triglycerides, toxic diacylglycerols (DAG) and ceramides or suppress muscle PKCc sarcolemmal translocation in db/db mice. Consequently, muscle ERRγdid not mitigate impaired muscle insulin signaling or insulin resistance in these mice. Similar results were obtained
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using the diet-induced obesity and diabetes model, where ERRγ did not have a desired effect. We see this as a paradigm-shifting observation that obesity and diabetes are not amenable to selective ERRγ-directed programming of classic exercise-like effects in the skeletal muscle. Other biochemical pathways or integrated whole-body effects of exercise may be critical for resisting diabetes and obesity. PROJECT 2: In another project we have found a muscle wasting factor called PGC1-beta. We have found that muscle-specific activation of PGC1-beta results in an age-dependent muscle loss. This muscle loss was caused by the activation of apoptosis and autophagy pathways in the skeletal muscles by PGClbeta. We are further exploring the molecular mechanisms of this effect of PG -beta and are asking whether inactivation of this gene can prevent muscle loss with aging. QINGCHUN TONG: With this support, we have demonstrated that leptin action in the brain restored euglycemia in type 1 diabetic models and this effect was mediated by p-STAT3 signaling, but not by fast-acting neurotransmitters, glutamate and GABA. In addition, we also showed that the effect of NPY induction of C-Fos in the paraventricular hypothalamus is contributed by insulin action. This support is instrumental for the group in reducing the burden of the extensive mouse cost associated with the projects, and in establishing the Optogenetics method in the brain, which is now actively employed in the lab to study mouse behavior. A few more manuscripts are being prepared with this support and will be reported in the near future. DACHUN WANG:
We have developed a site-specific targeting strategy to generate genetic mutation-free and reprogramming factor-free "clinical grade" iPSCs (Yan et al., Stem Cells 2014). With this novel technique, we have also generated "clinical grade" patient-derived iPSC types with surfactant protein B (SPB) deficiency (121ins2) for the proposed studies. To isolate disease-specific lung alveolar type II (ATII) cells, we introduced a dual transgene (ATII cell-specific SPC promoter/neomycin plus inducible mature SPB or inducible mature SPC gene) into iPSCs, and thus derived ATII cell types can be purified and conditionally induced to express mature SPB or mature SPC in a dose-dependent manner to analyze the extent to which aberrantly processed proSPB and/or proSPC contribute to surfactant dysfunction. As expected, we have generated essentially pure populations of "clinical grade" human SPB deficient iPSC derived ATII cell phenotypes, and demonstrated that the derived surfactant protein deficient ATII cell types can be reliable model to dissect proSPC processing pathway. We have been working on microRNA array study to define microRNA mediated surfactant protein processing pathways. We recently found that SPB mutations lead to an altered microRNA profile, which can further disturb proSPC processing and be expressed as a disease-specific exosome-microRNA signature. Hence, characterization of exosome-microRNA signature of SPB deficient ATII cells will make it possible for the first time to identify key microRNA and to define the microRNA-mediated pathway controlling proSPC processing. Because SPB and SPC show extensive or complete overlap in their capacity to promote surfactant activity, identification of key microRNA controlling proSPC processing to develop novel strategies to restore endogenous SPC processing will have enormous clinical impact on the treatment of RDS caused by complete SPB deficiency or developmental surfactant deficiency.
In addition, with the generated human iPSCs, we are the first lab that have identified a lung differentiation axis of LSC-BASC-ATTIC and revealed a novel role of miRNA in directing lung lineage-specific differentiation, which will allow us to develop a novel strategy to target the endogenous repair pathways for repair of injured lung (our finding has recently been revised for re-submission). L-C-0004, J. EVANS ATTWELL-WELCH POSTDOCTORAL FELLOWSHIP ENDOWMENT IN CHEMISTRY, Rice University. OARA NEUMANN: My previous year's research has been focused on investigating the effects of the metallic Au nanoshells on the distillation process of the two azeotropic systems, with different hydrogen bonding network strength, ethanol and 1-propanol-water mixtures. In the case of the Au nanoshell-ethanol-water mixtures, the mole fraction of ethanol obtained in the laser induced distillation process was higher than that obtained by the conventional thermal flash distillation process. In contrast, the nanoshell- 1 -propanol-water mixtures the mole fraction that resulted from the laser induced distillation process was found to be similar to that of the thermal distillation process. We have also investigated the laser-induced phase separation between nanoshell-1 -propanol solutions as the mixtures were illuminated from the top vs. the bottom. It was found that the top illumination phase separation process is reversible, whilst illumination from the bottom induced conventional dynamic boiling. Other notable conducted research includes an investigation into the type, size, and shape of the nanostructures on the light-induced evaporation process. This will possibly offer full control of the evaporation process in the future. In addition, we have also been investigating the enhancement of the water purification process using membranes by addition of broadband absorbing nanoparticles.
Finally, I am designing and synthesizing sub-100 nm theranostic nanomatryoshkas nanoparticles with both photothermal and T1 MRI-contrast imaging characteristics that will allow real time tracking of the nanoparticles and light-induced imaging processes. This nanomatryoshka consists of a Au core, interstitial Gd(III/Mn(II)-chelates doped SiO2 layer, and an outer Au shell. The MRI-mechanism of GdNM was theoretically and experimentally investigated in order to control the imaging process. ANTHONY STENDER:
Related to objective #1, much of 2015 was spent performing benchtop bulk-scale experiments in order to test the performance of dyes that begin to fluoresce when they react with ammonia. Since late 2015, I have focused on scaling down the bulk scale experiments (100 mL of solution) to a size that can be used on an optical microscope (2 mL or less). Challenges have included: 1) finding the ideal pH range to perform the microscale experiments since the catalyzed reaction and the best fluorescent dye prefer different pH ranges, and 2) developing the ideal sample preparation methods. Typically this type of experiment would rely on imaging the dye molecules in real time as they move in solution, but the reaction chemistry of the dye is poisonous to the catalyst. As such, I am developing methods to immobilize the dye on the glass substrate alongside the catalytic nanoparticles. Related to objective #2, I have been using microscopy and spectroscopy to study the optical properties of a unique polymer blend that changes transparency, depending on its temperature. I am also in
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the early stages of collaborating with the research group of Jill Millstone at Pitt to study the catalytic properties of nanoparticles synthesized by her group. Lastly, I have previous experience with differential interference contrast (DIC) microscopy, and it has been suggested that DIC cannot be easily combined with a spectrometer. I am testing the validity of that belief with different microscope-spectrometer configurations, because DIC spectroscopy would be a powerful tool for studying nanoscale and microscale inorganic materials as well as biological samples.
THEJASWI TUMKUR: We have successfully imaged the plasmon resonances in gold nanorods and gap modes in gold dimer structures, by mapping the photo-induced
gradient forces (in collaboration with the Halas and Nordlander groups). We further demonstrate the polarization-sensitivity of this technique by studying the orientation-dependent response of the gradient force intensities in the gold nanostructures.
In another effort, we image photocatalytic Pd-decorated Al nanospheres and resolve Pd features, as small as 10nm in diameter using gradient force microscopy (in collaboration with the Ringe group). We have also started imaging the near-fields of atomic layers of MoS2 (in collaboration with the Ajayan group). L-E-0001, ENDOWMENT IN CHEMISTRY AND RELATED SCIENCES (TcSUH), University of Houston.
The Brgoch group has developed new phosphors for solid-state lighting through the synthesis and characterization of borates, nitrides, and carbonitrides. Specifically, the research focus has centered on developing new compositions of matter including a barium yttrium borate phosphor that when substituted with Ce3+ produces a bright blue emission. This work has produced one publication and a patent disclosure. Additionally, a new strontium-based carbonitride was identified that produces a bright red-orange emission when excited with blue light making it a viable material for incorporation in current solid-state lighting devices.
The Brgoch research group has focused on understanding the chemistry of transition metals and main group elements in extreme environments like ultra-high-pressure. Using ab initio density functional theory he has identified a number of unique elemental oxidation states that seemingly violate classic electron counting. For example, above 200 GPa noble gases can accept electrons from Mg and become formally anionic. Applying high pressure (>20 GPa) to the binary lithium iodide (Linl) forces additional electron transfer to iodine in the first report of a halogen going beyond the ‒1 oxidation states. Finally, pressures greater than 10 GPa allow iridium to accept electrons and be formally anionic in the first report of K3lr. This research has led to one publication and the submission of two additional manuscripts.
The Chen group has investigated earth-abundant layered transition metal dichalcogenides (LTMDs) which are promising materials to replace expensive and rare Pt as electro-catalysts for hydrogen evolution through water electrolysis. Various nanostructured LTMDs, such as WSx, NiSe2, and MoS2(1-
x)Se2x were synthesized. The materials were loaded on functionalized porous Ni foams and thus have very high surface area. Their electronic structures are favourable for HER and their HER performance is among the best compared to other reported LTMDs. Based on the results, one paper was published and two manuscripts were submitted. Currently two manuscripts are in preparation. Other LTMDs with proper electronic structures are being studied for the oxygen evolution reaction.
For carbon monoxide oxidation (COO) and methanol oxidation reactions (MOR), nanostructured gold is a very active catalyst. During the past year, a novel method to fabricate nanoporous gold meshes was developed. The meshes consist of high index planes, which are highly efficient for catalyzing COO and MOR. The gold meshes outperform most other gold structures such as nanoparticles and nanoporous gold (made by the traditional de-alloying method) for MOR. Currently, a manuscript on the fabrication method and MOR performance of the gold meshes is in preparation. H-E-0041, CENTER OF EXCELLENCE IN POLYMER CHEMISTRY, University of Houston.
A national search continues to hire an established academic or industrial chemistry researcher at the Associate or Full Professor level to assume a leadership role in the Center. The University has fully committed substantial salary funds for the position and a major portion of the Welch grant will be used to support this position and to purchase Center equipment for polymer characterization. Currently, a draft offer has been made to Professor Bryan Coughlin in the Department of Polymer Science and Engineering at the University of Massachusetts Amherst. Professor Coughlin's research is centered on polymer synthesis to generate functional polymeric materials for emerging technologies. Negotiations to bring Professor Coughlin to UH are continuing.
The Department of Chemical and Biomolecular Engineering has also continued its national search for a senior polymer engineer to join the Center. Negotiations with a prominent polymer theorist focusing on polymer dynamics, polymer surfaces, and biopolymers are in progress. The construction of Polymer Center laboratories for Chemistry totaling approximately 4800 sq. ft. was completed in early 2016. In the space, the Center Director will occupy a new twelve-hood synthetic chemistry laboratory adjacent to a laboratory occupied currently by the research group of Professor Maurice Brookhart, who joined the Chemistry faculty in September 2015 and participates as a member of the Center. The Director will have additional instrumentation laboratories for characterization and shared Center equipment
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PUBLICATIONS BY PRINCIPAL INVESTIGATORS REPORTED DURING 2015 – 2016
Research Grants ................................................................................................................................................ 130
Other Endowed Grants ..................................................................................................................................... 237
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RESEARCH GRANTS
47722. A. D’Brot, P. Kurtz, E. Regan, B. Jakubowski and JOHN M. ABRAMS, Grant I-1865, (The University of Texas Southwestern Medical Center),
47872. Xiaolei Wang, Yang Gao, Zhiqiang Ma, Rodrigo A. Rodriguez, Zhi-Xiang Yu and CHUO CHEN, Grant I-1868, (The University of Texas
Southwestern Medical Center), “Syntheses of Sceptrins and Nakamuric Acid and Insights Into the Biosyntheses of Pyrrole−Imidazole Dimers”,
Organic Chemistry Frontiers, 2, 978-984, (2015).
139
47873. Heping Shi, Jiaxi Wu, Zhijian J. Chen and CHUO CHEN, Grant I-1868, (The University of Texas Southwestern Medical Center), “Molecular Basis
for the Specific Recognition of the Metazoan Cyclic GMP-AMP by the Innate Immune Adaptor Protein STING”, Proceedings of the National
Academy of Sciences, 112, 8947-8952, (2015).
47874. Zhiqiang Ma, Xiao Wang, Yuyong Ma and CHUO CHEN, Grant I-1868, (The University of Texas Southwestern Medical Center), “Asymmetric
Synthesis of Axinellamines A and B”, Angewandte Chemie, International Edition, 55, 4763-4766, (2016).
47875. Baokun He and ZHENG CHEN, Grant AU-1731, (The University of Texas Health Science Center at Houston), “Molecular Targets for Small-
Molecule Modulators of Circadian Clocks”, Current Drug Metabolism, 17, 503-512, (2016).
47876. Baokun He, Kazunari Nohara, Noheon Park, Yong-Sung Park, Bobby Guillory, Zhaoyang Zhao, Jose M. Garcia, Nobuya Koike, Cheng Chi Lee,
Joseph S. Takahashi, Seung-Hee Yoo and ZHENG CHEN, Grant AU-1731, (The University of Texas Health Science Center at Houston), “The
Small Molecule Nobiletin Targets the Molecular Oscillator to Enhance Circadian Rhythms and Protect Against Metabolic Syndrome”, Cell
Metabolism, 23, 610-621, (2016).
47877. Euna Lee, Eunjoo Cho, Doo Hyun Kang, Eun Hee Jeong, ZHENG CHEN, Grant AU-1731, (The University of Texas Health Science Center at
Houston), Seung-Hee Yoo and Eun Young Kim, “Pacemaker-Neuron−Dependent Disturbance of the Molecular Clockwork by a Drosophila CLOCK
Mutant Homologous to the Mouse CLOCK∆19”, Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1523494113, (2016).
47878. Haijie Lu, Qiqi Chu, Guojiang Xie, Hao Han, ZHENG CHEN, Grant AU-1731, (The University of Texas Health Science Center at Houston),
Benhua Xu and Zhicao Yue, “Circadian Gene Expression Predicts Patient Response to Neoadjuvant Chemoradiation Therapy for Rectal Cancer”,
International Journal of Clinical and Experimental Pathology, 8, 10985-10994, (2015).
47879. Daxing Gao, Tuo Li, Xiao-Dong Le, Xiang Chen, Quan-Zhen Li, Mary Wight-Carter and ZHIJIAN J. CHEN, Grant I-1389, (The University of
Texas Southwestern Medical Center), “Activation of Cyclic GMP-AMP Synthase by Self-DNA Causes Autoimmune Diseases”, Proceedings of the
National Academy of Sciences, DOI: 10.1073/pnas.1516465112, (2015).
47880. Nadav Marbach-Bar, Anat Bahat, Shaked Ashkenazi, Michal Golan-Mashiach, Ora Haimov, Shwu-Yuan Wu, CHENG-MING CHIANG, Grant I-
1805, (The University of Texas Southwestern Medical Center), Anna Puzio-Kuter, Kim M. Hirshfield, Arnold J. Levine and Rivka Dikstein, “DTIE,
a Novel Core Promoter Element That Directs Start Site Selection in TATA-Less Genes”, Nucleic Acids Research, 44, 1080-1094, (2016).
47881. Roya Kalantari, CHENG-MING CHIANG, Grant I-1805, (The University of Texas Southwestern Medical Center) and David R. Corey,
“Regulation of Mammalian Transcription and Splicing by Nuclear RNAi”, Nucleic Acids Research, 44, 524-537, (2016).
47882. Maria Delcuratolo, Jasmin Fertey, Markus Schneider, Johanna Schuetz, Natalie Leiprecht, Benjamin Hudjetz, Stephan Brodbeck, Silke Corall, Marcel
Dreer, Roxana Michaela Schwab, Martin Grimm, Shwu-Yuan Wu, Frank Stubenrauch, CHENG-MING CHIANG, Grant I-1805, (The University
of Texas Southwestern Medical Center) and Thomas Iftner, “Papillomavirus-Associated Tumor Formation Critically Depends on c-Fos Expression
Induced by Viral Protein E2 and Bromodomain Protein Brd4”, PLOS Pathogens, DOI: 10.1371/journal/ppat.1005366, (2016).
47883. Shaokum Shu, Charles Y. Lin, Housheng Hansen He, Robert M. Witwicki, Doris P. Tabassum, Justin M. Roberts, Michalina Janiszewska, Sung Jin
Huh, Yi Liang, Jeremy Ryan, Ernest Doherty, Hisham Mohammed, Hao Guo, Daniel G. Stover, Muhammad B. Ekram, Guillermo Peluffo, Jonathan
Brown, Clive D’Santos, Ian E. Krop, Deborah Dillon, Michael McKeown, Christopher Ott, Jun Qi, Min Ni, Prakash K. Rao, Melissa Duarte, Shwu-
Yuan Wu, CHENG-MING CHIANG, Grant I-1805, (The University of Texas Southwestern Medical Center), Lars Anders, Richard A. Young,
Eric P. Winer, Anthony Letai, William T. Barry, Jason S. Carroll, Henry W. Long, Myles Brown, X. Shirley Liu, Clifford A. Meyer, James E. Bradner
and Kornelia Polyak, “Response and Resistance to BET Bromodomain Inhibitors in Triple-Negative Breast Cancer”, Nature, 529, 413-417, (2016).
47884. Dong-Hyun Kim, Sanghoon Kwon, Sangwon Byun, Zhen Xiao, Sean Park, Shwu-Yuan Wu, CHENG-MING CHIANG, Grant I-1805, (The
University of Texas Southwestern Medical Center), Byron Kemper and Jongsook Kim Kemper, “Critical Role of RanBP2-Mediated SUMOylation
of Small Heterodimer Partner in Maintaining Bile Acid Homeostasis”, Nature Communications, DOI: 10.1038/ncomms12179, (2016).
47885. Shwu-Yuan Wu, Dawn Sijin Nin, A-Young Lee, Scott Simanski, Thomas Kodadek and CHENG-MING CHIANG, Grant I-1805, (The University
of Texas Southwestern Medical Center), “BRD4 Phosphorylation Regulates HPV E2-Mediated Viral Transcription, Origin Replication and Cellular
47934. Cholpon Tilegenova, Spandana Vemulapally, Doris M. Cortes and LUIS G. CUELLO, Grant BI-1757, (Texas Tech University Health Sciences
Center), “An Improved Method for the Cost-Effective Expression and Purification of Large Quantities of KcsA”, Protein Expression and Purification,
127, 53-60, (2016).
47935. Chenglin Zhang, Weicheng Lv, Guotai Tan, Yu Song, Scott V. Carr, Songxue Chi, M. Masuda, A. D. Christianson, J. A. Fernandez-Baca, L. W.
Harriger and PENGCHENG DAI, Grant C-1839, (Rice University), “Electron Doping Evolution of the Neutron Spin Resonance in NaFe1−xCoxAs”,
Physical Review B, 93, 174522(1-7), 2016).
47936. Meng Wang, M. Yi, H. L. Sun, P. Valdivia, M. G. Kim, Z. J. Xu, T. Berlijn, A. D. Christianson, Songxue Chi, M. Hashimoto, D. H. Lu, X. D. Li, E.
Bourret-Courchesne, PENGCHENG DAI, Grant C-1839, (Rice University), D. H. Lee, T. A. Maier and R. J. Birgeneau, “Experimental Elucidation
of the Origin of the ‘Double Spin Resonances’ in Ba(Fe1−xCox)2As2”, Physical Review B, 93, 205149(1-7), (2016).
47937. Dongliang Gong, Tao Xie, Xingyu Lu, Cong Ren, Lei Shan, Rui Zhang, PENGCHENG DAI, Grant C-1839, (Rice University), Yi-feng Yang,
Huiqian Luo and Shiliang Li, “Electronic Specific Heat in BaFe2−xNixAs2”, Physical Review B, 93, 134520(1-8), (2016).
47938. Xingye Lu, Kuo-Feng Tseng, T. Keller, Wenliang Zhang, Ding Hu, Yu Song, Haoran Man, J. T. Park, Huiqian Luo, Shiliang Li, Andriy H.
Nevidomskyy and PENGCHENG DAI, Grant C-1839, (Rice University), “Impact of Uniaxial Pressure on Structural and Magnetic Phase
Transitions in Electron-Doped Iron Pnictides”, Physical Review B, 93, 134519(1-17), (2016).
47939. V. K. Thorsmølle, M. Khodas, Z. P. Yin, Chenglin Zhang, S. V. Carr, PENGCHENG DAI, Grant C-1839, (Rice University) and G. Blumberg,
“Critical Quadrupole Fluctuations and Collective Modes in Iron Pnictide Superconductors”, Physical Review B, 93, 054515(1-21), (2016).
(Rice University), Yan Zhang, Yuji Matsuda and Yuan Li, “Nematic Magnetoelastic Effect Contrasted between Ba(Fe1−xCox)2As2 and FeSe”,
Physical Review B, 93, 060504(R1-6), (2016).
47941. Yu Song and PENGCHENG DAI, Grant C-1839, (Rice University), “High-Temperature Superconductors”, Experimental Methods in the Physical
Sciences, 48, 145-201, (2015).
47942. Xiao Ren, Lian Duan, Yuwen Hu, Jiarui Li, Rui Zhang, Huiqian Luo, PENGCHENG DAI, Grant C-1839, (Rice University) and Yuan Li, “Nematic
Crossover in BaFe2As2 Under Uniaxial Stress”, Physical Review Letters, 115, 197002(1-5), (2015).
143
47943. Yu Song, Xingye Lu, D. L. Abernathy, David W. Tam, J. L. Niedziela, Wei Tian, Huiqian Luo, Qimiao Si and PENGCHENG DAI, Grant C-1839,
(Rice University), “Energy Dependence of the Spin Excitation Anisotropy in Uniaxial-Strained BaFe1.9Ni0.1As2”, Physical Review B, 92, 180504(R1-
6), (2015).
47944. Haoran Man, Xingye Lu, Justin S. Chen, Rui Zhang, Wenliang Zhang, Huiqian Luo, J. Kulda, A. Ivanov, T. Keller, Emilia Morosan, Qimiao Si and
PENGCHENG DAI, Grant C-1839, (Rice University), “Electronic Nematic Correlations in the Stress-Free Tetragonal State of BaFe2−xNixAs2”,
Physical Review B, 92, 134521(1-9), (2015).
47945. PENGCHENG DAI, Grant C-1839, (Rice University), “Antiferromagnetic Order and Spin Dynamics in Iron-Based Superconductors”, Reviews of
Modern Physics, 87, 855-896, (2015).
47946. B. J. Campbell, S. Rosenkranz, H. J. Kang, H. T. Stokes, P. J. Chupas, S. Komiya, Y. Ando, Shiliang Li and PENGCHENG DAI, Grant C-1839,
(Rice University), “Long-Range Two-Dimensional Superstructure in the Superconducting Electron-Doped Cuprate Pr0.88LaCe0.12CuO4”, Physical
Review B, 92, 014118(1-7), (2015).
47947. Xuanzhi Zhan, Henriette Stoy, Tamer S. Kaoud, Nicole A. Perry, Quiyan Chen, Alejandro Perez, Sylvia Els-Heindl, Jack V. Slagis, Tina M. Iverson,
Annette G. Beck-Sickinger, Eugenia V. Gurevich, KEVIN N. DALBY, Grant F-1390, (The University of Texas at Austin) and Vsevolod V.
48163. Zinaida Yudina, Amanda Roa, Rory Johnson, Nikolaos Biris, Daniel A. de Souza Aranha Vieira, Vladislav Tsiperson, Natalia Reszka, Alexander B.
Taylor, P. JOHN HART, Grant AQ-1399, (The University of Texas Health Science Center at San Antonio), Borries Demeler, Felipe Diaz-Griffero
and Dmitri N. Ivanov, “RING Dimerization Links Higher-Order Assembly of TRIM5α to Synthesis of K63-Linked Polybiquitim”, Cell Reports, 12,
788-797, (2015).
48164. Nobuhiro Tago, Adam Katolik, Nathaniel E. Clark, Eric J. Montemayor, Kohji Seio, Mitsuo Sekine, P. JOHN HART, Grant AQ-1399, (The
University of Texas Health Science Center at San Antonio) and Masad J. Damha, “Design, Synthesis and Properties of Phosphoramidate 2’,5’-Linked
Branched RNA: Toward the Rational Design of Inhibitors of the RNA Lariat Debranching Enzyme”, The Journal of Organic Chemistry, 80, 10108-
10118, (2015).
48165. Alexander B. Taylor, Livia Pica-Mattoccia, Chiara M. Polcaro, Enrica Donati, Xiaohang Cao, Annalisa Basso, Alessandra Guidi, Anastasia R. Rugel,
Stephen P. Holloway, Timothy J.C. Anderson, P. JOHN HART, Grant AQ-1399, (The University of Texas Health Science Center at San Antonio),
Donato Cioli and Philip T. LoVerde, “Structural and Functional Characterization of the Enantiomers of the Antischistosomal Drug Oxamniquine”,
48166. Frédéric D. Chevalier, Winka Le Clec’h, Nina Eng, Anastasia R. Rugel, Rafael Ramiro de Assis, Guiherme Oliveira, Stephen P. Holloway, Xiaohang
Cao, P. JOHN HART, Grant AQ-1399, (The University of Texas Health Science Center at San Antonio), Philip T. Loverde and Timothy J.C.
Anderson, “Independent Origins of Loss-of-Function Mutations Conferring Oxamniquine Resistance in a Brazilian Schistosome Population”,
International Journal for Parasitology, 46, 417-424, (2016).
48167. Sarah J. Wong, Micah D. Gearhart, Alexander B. Taylor, David R. Nanyes, Daniel J. Ha, Angela K. Robinson, Jason A. Artigas, Oliver J. Lee, Borries
Demeler, P. JOHN HART, Grant AQ-1399, (The University of Texas Health Science Center at San Antonio), Vivian J. Bardwell and Chongwoo
A. Kim, “KDM2B Recruitment of the Polycomb Group Complex, PRC1.1, Requires Cooperation Between PCGF1 and BCORL1”, Structure, D-16-
00152R, (2016).
156
48168. Vivek A. Kumar, Qi Liu, Navindee C. Wickremasinghe, Siyu Shi, Toya T. Cornwright, Yuxiao Deng, Alon Azares, Amanda N. Moore, Amanda M.
Acevedo-Jake, Noel R. Agudo, Su Pan, Darren G. Woodside, Peter Vanderslice, James T. Willerson, Richard A. Dixon and JEFFREY D.
HARTGERINK, Grant C-1557, (Rice University), “Treatment of Hind Limb Ischemia Using Angiogenic Peptide Nanofibers”, Biomaterials, 98,
113-119, (2016).
48169. Amanda M. Acevedo-Jake, Katherine A. Clements and JEFFREY D. HARTGERINK, Grant C-1557, (Rice University), “Synthetic, Register-
Specific, AAB Heterotrimers to Investigate Single Point Glycine Mutations in Osteogenesis Imperfecta”, Biomacromolecules, 17, 914-921, (2016).
48170. Vivek A. Kumar, Navindee C. Wickremasinghe, Siyu Shi and JEFFREY D. HARTGERINK, Grant C-1557, (Rice University), “Nanofibrous
48734. Fang Bai, Faruck Morcos, Yang-Sung Sohn, Merav Darash-Yahana, Celso O. Rezende, Colin H. Lipper, Mark L. Paddock, Luhua Song, Yuting Luo,
Sarah H. Holt, Sagi Tamir, Emmanuel A. Theodorakis, Patricia A. Jennings, JOSÉ N. ONUCHIC, Grant C-1792, (Rice University), Ron Mittler
and Rachel Nechushtai, “The Fe-S Cluster-Containing NEET Proteins mitoNEET and MAF-1 as Chemotherapeutic Targets in Breast Cancer”,
Proceedings of the National Academy of Sciences, 112, 3698-3703, (2015).
48735. Biman Jana and JOSÉ N. ONUCHIC, Grant C-1792, (Rice University), “Strain Mediated Adaptation Is Key for Myosin Mechanochemistry:
Discovering General Rules for Motor Activity”, PLoS Computational Biology, DOI: 10.1371/journal.pcbi.1005035, (2016).
48736. Dor Salomon, John A. Klimko, David C. Trudgian, Lisa N. Kinch, Nick V. Grishin, Hamid Mirzaei and KIM ORTH, Grant I-1561, (The University
of Texas Southwestern Medical Center), “Type VI Secretion System Toxins Horizontally Shared between Marine Bacteria”, PLoS Pathogens, DOI:
10.1371/journal.ppat.1005128, (2015).
48737. Peng Li, Giomar Rivera-Cancel, Lisa N. Kinch, Dor Salomon, Diana R. Tomchick, Nick V. Grishin and KIM ORTH, Grant I-1561, (The University
of Texas Southwestern Medical Center), “Bile Salt Receptor Complex Activates a Pathogenic Type III Secretion System”, eLife, DOI:
10.7554/eLife.15718, (2016).
48738. Ann Ray, Lisa N. Kinch, Marcela de Souza Santos, Nick V. Grishin, KIM ORTH, Grant I-1561, (The University of Texas Southwestern Medical
Center) and Dor Salomon, “Proteomics Analysis Reveals Previously Uncharacterized Virulence Factors in Vibrio proteolyticus”, mBio, DOI:
10.1128/mBio.01077-16, (2016).
48739. Chun-I Lee, Nathanael A. Hirscher, Jia Zhou, Nattamai Bhuvanesh and OLEG V. OZEROV, Grant A-1717, (Texas A&M University),
“Adaptability of the SiNN Pincer Ligand in Iridium and Rhodium Complexes Relevant to Borylation Catalysis”, Organometallics, 34, 3099-3102,
(2015).
189
48740. Christopher J. Pell and OLEG V. OZEROV, Grant A-1717, (Texas A&M University), “Catalytic Dehydrogenative Borylation of Terminal Alkynes
by POCOP-Supported Palladium Complexes”, Inorganic Chemistry Frontiers, 2, 720-724, (2015).
48741. Wei-Chun Shih and OLEG V. OZEROV, Grant A-1717, (Texas A&M University), “One-Pot Synthesis of 1,3-Bis(phosphinomethyl)arene
PCP/PNP Pincer Ligands and Their Nickel Complexes”, Organometallics, 34, 4591-4597, (2015).
48742. Chun-I Lee, Wei-Chun Shih, Jia Zhou, Joseph H. Reibenspies and OLEG V. OZEROV, Grant A-1717, (Texas A&M University), “Synthesis of
Triborylalkenes from Terminal Alkynes by Iridium-Catalyzed Tandem C−H Borylation and Diboration”, Angewandte Chemie International Edition,
54, 14003-14007, (2015).
48743. Jessica C. DeMott, John R. Dekarske, Billy J. McCulloch and OLEG V. OZEROV, Grant A-1717, (Texas A&M University), “Cyclometallation of
the NNN Pincer Ligand in Complexes of Platinum”, Inorganic Chemistry Frontiers, 2, 912-916, (2015).
48744. Chun-I Lee, Jessica C. DeMott, Christopher J. Pell, Alyson Christopher, Jia Zhou, Nattamai Bhuvanesh and OLEG V. OZEROV, Grant A-1717,
(Texas A&M University), “Ligand Survey Results in Identification of PNP Pincer Complexes of Iridium as Long-Lived and Chemoselective Catalysts
for Dehydrogenative Borylation of Terminal Alkynes”, Chemical Science, 6, 6572-6582, (2015).
48745. Jessica C. DeMott, Weixing Gu, Billy J. McCulloch, David E. Herbert, Mitchell D. Goshert, Justin R. Walensky, Jia Zhou and OLEG V. OZEROV,
Grant A-1717, (Texas A&M University), “Silyl−Silylene Interplay in Cationic PSiP Pincer Complexes of Platinum”, Organometallics, 34, 3930-
3933, (2015).
48746. Loren P. Press, Billy J. McCulloch, Weixing Gu, Chun-Hsing Chen, Bruce M. Foxman and OLEG V. OZEROV, Grant A-1717, (Texas A&M
University), “Triflyloxy-Substituted Carboranes as Useful Weakly Coordinating Anions”, Chemical Communications, 51, 14034-14037, (2015).
48747. Wei-Chun Shih, Weixing Gu, Morgan C. MacInnis, Samuel D. Timpa, Nattamai Bhuvanesh, Jia Zhou and OLEG V. OZEROV, Grant A-1717,
(Texas A&M University), “Facile Insertion of Rh and Ir into a Boron−Phenyl Bond, Leading to Boryl/Bis(phosphine) PBP Pincer Complexes”,
Journal of the American Chemical Society, 138, 2086-2089, (2016).
48748. Alex J. Kosanovich, Joseph H. Reibenspies and OLEG V. OZEROV, Grant A-1717, (Texas A&M University), “Complexes of High-Valent
Rhenium Supported by the PCP Pincer”, Organometallics, 35, 513-519, (2016).
48749. Loren P. Press, Alex J. Kosanovich, Billy J. McCulloch and OLEG V. OZEROV, Grant A-1717, (Texas A&M University), “High-Turnover
Aromatic C−H Borylation Catalyzed by POCOP-Type Pincer Complexes of Iridium”, Journal of the American Chemical Society, DOI:
10.1021/jacs6b03656, (2016).
48750. JEREMY C. PALMER, Grant E-1882, (University of Houston), Rakesh S. Singh, Renjie Chen, Fausto Martelli and Pablo G. Debenedetti, “Density
and Bond-Orientational Relaxations in Supercooled Water”, Molecular Physics, DOI: 10.1080/00268976.2016.1179351, (2016).
48751. Hemant K. Sharma, Paulina E. Gonzalez, Alexander L. Craig, Sanchita Chakrabarty, Alejandro Metta-Magaña and KEITH H. PANNELL, Grant
AH-0546, (The University of Texas at El Paso), “Siloxymethylamines as Aminomethylation Reagents for Amines Leading to Labile
Diaminomethanes That can be Trapped as Their [Mo(CO)4] Complexes”, Chemistry, A European Journal, 22, 7363-7366, (2016).
48752. Renzo N. Arias-Ugarte, Hemant K. Sharma and KEITH H. PANNELL, Grant AH-0546, (The University of Texas at El Paso), “Amide (A)-
Thioamide (T) Interconversions Using Ph3SiSH (A to T) and Ph3SnOH (T to A) Reagents”, Applied Organometallic Chemistry, 30, 510-513, (2016).
48753. Robinson I. Roacho, Alejandro Metta-Magaña, José L. Belmonte-Vázquez, Eduardo Peña-Cabrera and KEITH H. PANNELL, Grant AH-0546,
(The University of Texas at El Paso), “Formation of 8-RS-BODIPYs via Direct Substitution of 8-MeS-BODIPY by RSH (R = Et, Pr, Bu, tBu, n-
C12H25, C6H5, p-MeC6H4, p-MeOC6H4 and 2,6-Me2C6H3)”, Canadian Journal of Chemistry, 94, 234-239, (2016).
48754. Jing Sun, Ning Li, Kyu-Seon Oh, Bhaskar Dutta, Sharat J. Vayttaden, Bin Lin, Thomas S. Ebert, Dominic De Nardo, Joie Davis, Rustam Bagirzadeh,
Nicholas W. Lounsbury, CHANDRASHEKHAR PASARE, Grant I-0820, (The University of Texas Southwestern Medical Center), Eicke Latz,
Veit Hornung and Iain D.C. Fraser, “Comprehensive RNAi-Based Screening of Human and Mouse TLR Pathways Identifies Species-Specific
Preferences in Signaling Protein Use”, Science Signaling, DOI: 10.1126/scisignal.aab2191, (2016).
48755. S. B. Fairchild, J. Boeckl, T. C. Back, J. B. Ferguson, H. Koerner, P. T. Murray, B. Maruyama, M. A. Lange, M. M. Cahay, N. Behabtu, C. C. Young,
MATTEO PASQUALI, Grant C-1668, (Rice University), N. P. Lockwood, K. L. Averett, G. Gruen and D. E. Tsentalovich, “Morphology
Dependent Field Emission of Acid-Spun Carbon Nanotube Fibers”, Nanotechnology, 26, 105706(1-9), (2015).
48756. Dmitri E. Tsentalovich, Anson W.K. Ma, J. Alex Lee, Natnael Behabtu, E. Amram Bengio, April Choi, Junli Hao, Yimin Luo, Robert J. Headrick,
Micah J. Green, Yeshayahu Talmon and MATTEO PASQUALI, Grant C-1668, (Rice University), “Relationship of Extensional Viscosity and
Liquid Crystalline Transition to Length Distribution in Carbon Nanotube Solutions”, Macromolecules, 49, 681-689, (2016).
190
48757. Francesca Mirri, Nathan D. Orloff, Aaron M. Forster, Rana Ashkar, Robert J. Headrick, E. Amram Bengio, Christian J. Long, April Choi, Yimin Luo,
Angela R. Hight Walker, Paul Butler, Kalman B. Migler and MATTEO PASQUALI, Grant C-1668, (Rice University), “Lightweight, Flexible,
High-Performance Carbon Nanotube Cables Made by Scalable Flow Coating”, ACS Applied Materials and Interfaces, 8, 4903-4910, (2016).
48758. Xiaoyi Deng, David Matthews, Pradipsinh K. Rathod and MARGARET A. PHILLIPS, Grant I-1257, (The University of Texas Southwestern
Medical Center), “The X-Ray Structure of Plasmodium falciparum Dihydroorotate Dehydrogenase Bound to a Potent and Selective N-
48904. Rong Yu and QIMIAO SI, Grant C-1411, (Rice University), “Antiferroquadrupolar and Ising-Nematic Orders of a Frustrated Bilinear-Biquadratic
Heisenberg Model and Implications for the Magnetism of FeSe”, Physical Review Letters, 115, 116401(1-6), (2015).
48905. Z. K. Liu, M. Yi, Y. Zhang, J. Hu, R. Yu, J.-X. Zhu, R.-H. He, Y. L. Chen, M. Hashimoto, R. G. Moore, S.-K. Mo. Z. Hussain, QIMIAO SI, Grant
C-1411, (Rice University), Z. Q. Mao, D. H. Lu and Z.-X. Shen, “Experimental Observation of Incoherent-Coherent Crossover and Orbital-Dependent
Band Renormalization in Iron Chalcogenide Superconductors”, Physical Review B, 92, 235138(1-7), (2015).
48906. Emilian M. Nica, Rong Yu and QIMIAO SI, Grant C-1411, (Rice University), “Glide Reflection Symmetry, Brillouin Zone Folding and
Superconducting Pairing for the P4/nmm Space Group”, Physical Review B, 92, 174520(1-12), (2015).
48907. M. Yi, Z.-K. Liu, Y. Zhang, R. Yu, J.-X. Zhu, M. J. Lee, R. G. Moore, F. T. Schmitt, W. Li, S. C. Riggs, J.-H. Chu, B. Lv, J. Hu, M. Hashimoto, S.-
K. Mo, Z. Hussain, Z. Q. Mao, C. W. Chu, I. R. Fisher, QIMIAO SI, Grant C-1411, (Rice University), Z.-X. Shen and D. H. Lu, “Observation of
Universal Strong Orbital-Dependent Correlation Effects in Iron Chalcogenides”, Nature Communications, 10.1038/ncomms8777, (2015).
48908. Haoran Man, Xingye Lu, Justin S. Chen, Rui Zhang, Wenliang Zhang, Huiqian Luo, J. Kulda, A. Ivanov, T. Keller, Emilia Morosan, QIMIAO SI,
Grant C-1411, (Rice University) and Pengcheng Dai, “Electronic Nematic Correlations in the Stress-Free Tetragonal State of BaFe2−xNixAs2”,
Physical Review B, 92, 134521(1-9), (2015).
199
48909. Yu Song, Xingye Lu, D. L. Abernathy, David W. Tam, J. L. Niedziela, Wei Tian, Huiqian Luo, QIMIAO SI, Grant C-1411, (Rice University) and
Pengcheng Dai, “Energy Dependence of the Spin Excitation Anisotropy in Uniaxial-Strained BaFe1.9Ni0.1As2”, Physical Review B, 92, 180504(1-
6), (2015).
48910. S. Paschen, S. Friedemann, S. Wirth, F. Steglich, S. Kirchner and QIMIAO SI, Grant C-1411, (Rice University), “Kondo Destruction in Heavy
Fermion Quantum Criticality and the Photoemission Spectrum of YbRhzSi2”, Journal of Magnetism and Magnetic Materials, 400, 17-22, (2016).
48911. Erwin Schuberth, Marc Tippmann, Lucia Steinke, Stefan Lausberg, Alexander Steppke, Manuel Brando, Cornelius Drellner, Christoph Geibel, Rong
Yu, QIMIAO SI, Grant C-1411, (Rice University) and Frank Steglich, “Emergence of Superconductivity in the Cononical Heavy-Electron Metal
YbRh2Si2”, Science, 351, 485-488, (2016).
48912. QIMIAO SI, Grant C-1411, (Rice University), Rong Yu and Elihu Abrahams, “High-Temperature Superconductivity in Iron Pnictides and
49161. I. V. Fedotov, N. A. Safronov, Yu. G. Ermakova, M. E. Matlashov, D. A. Sidorov-Biryukov, A. B. Fedotov, V. V. Belousov and ALEKSEI M.
ZHELTIKOV, Grant A-1801, (Texas A&M University), “Fiber-Optic Control and Thermometry of Single-Cell Thermosensation Logic”, Scientific
Reports, DOI: 10.1038/srep15737, (2015).
49162. A. V. Mitrofanov, D. A. Sidorov-Biryukov, A. A. Voronin, A. Pugžlys, A. A. Lanin, A. B. Fedotov, V. Ya. Panchenko, a. Baltuška and ALEKSEI
M. ZHELTIKOV, Grant A-1801, (Texas A&M University), “New Horizons of Optics of the Midinfrared Spectral Range”, Optics and Spectroscopy,
119, 569-576, (2015).
49163. S. M. Blakley, I. V. Fedotov, S. Ya. Kilin and ALEKSEI M. ZHELTIKOV, Grant A-1801, (Texas A&M University), “Room-Temperature
Magnetic Gradiometry with Fiber-Coupled Nitrogen-Vacancy Centers in Diamond”, Optics Letters, 40, 3727-3730, (2015).
49164. P. N. Malevich, R. Maurer, D. Kartashov, A. Ališauskas, A. A. Lanin, ALEKSEI M. ZHELTIKOV, Grant A-1801, (Texas A&M University), M.
Marangoni, G. Cerullo, A. Baltuška and A. Pugžlys, “Stimulated Raman Gas Sensing by Backward UV Lasing from a Femtosecond Filament”, Optics
Letters, 40, 2469-2472, (2015).
49165. N. A. Safronov, I. V. Fedotov, Yu. G. Ermakova, M. E. Matlashov, D. A. Sidorov-Biryukov, A. B. Fedotov, V. V. Belousov and ALEKSEI M.
ZHELTIKOV, Grant A-1801, (Texas A&M University), “Microwave-Induced Thermogenetic Activation of Single Cells”, Applied Physics Letters,
106, 163702(1-4), (2015).
214
49166. A. V. Mitrofanov, A. A. Voronin, S. I. Mitryukovskiy, D. A. Sidorov-Biryukov, A. Pugžlys, G. Andriukaitis, T. Flöry, E. A. Stepanov, A. B. Fedotov,
A. Baltuška and ALEKSEI M. ZHELTIKOV, Grant A-1801, (Texas A&M University), “Mid-Infrared-to-Mid-Ultraviolet Supercontinuum
Enhanced by Third-to-Fifteenth Odd Harmonics”, Optics Letters, 40, 2068-2071, (2015).
49167. A. A. Lanin, A. A. Voronin, E. A. Stepanov, A. B. Fedotov and ALEKSEI M. ZHELTIKOV, Grant A-1801, (Texas A&M University),
“Multioctave, 3−18 μm Sub-Two-Cycle Supercontinua from Self-Compressing, Self-Focusing Soliton Transients in a Solid”, Optics Letters, 40, 974-
977, (2015).
49168. A. A. Voronin, V. Ya. Panchenko and ALEKSEI M. ZHELTIKOV, Grant A-1801, (Texas A&M University), “Supercomputations and Big-Data
Analysis in Strong-Field Ultrafast Optical Physics: Filamentation of High-Peak-Power Ultrashort Laser Pulses”, Laser Physics Letters, 13, 065403(1-
6), (2016).
49169. Chuanqi Ge, Yuneng Shen, Gang-Hua Deng, Yuhuan Tian Dongqi Yu, Xueming Yang, Kaijun Yuan and JUNRONG ZHENG, Grant C-1752,
(Rice University), “Negligible Isotopic Effect on Dissociation of Hydrogen Bonds”, The Journal of Physical Chemistry B, 120, 3187-3195, (2016).
49447. Oleg A. Sineshchelov, Hai Li, Elena G. Govorunova and JOHN L. SPUDICH, Chair AU-0009, (The University of Texas Health Science Center at
Houston), “Photochemical Reaction Cycle Transitions During Anion Channelrhodopsin Gating”, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.1525269113, (2016).
49448. Elena G. Govorunova, Oleg A. Sineshchelov and JOHN L. SPUDICH, Chair AU-0009, (The University of Texas Health Science Center at Houston),
“Proteomonas sulcata ACR1: A Fast Anion Channelrhodopsin”, Photochemistry and Photobiology, 92, 257-263, (2016).
49449. Oleg A. Sineshchelov, Elena G. Govorunova, Hai Li and JOHN L. SPUDICH, Chair AU-0009, (The University of Texas Health Science Center at
Houston), “Gating Mechanisms of a Natural Anion Channelrhodopsin”, Proceedings of the National Academy of Sciences, 112, 14236-14241, (2015).
49450. Adrian Yi, Natalia Mamaeva, Hai Li, JOHN L. SPUDICH, Chair AU-0009, (The University of Texas Health Science Center at Houston) and
Kenneth J. Rothschild, “Resonance Raman Study of an Anion Channelrhodopsin: Effects of Mutations Near the Retinylidene Schiff Base”,
Biochemistry, 55, 2371-2380, (2016).
49451. Hai Li, Oleg A. Sineshchekov, Giordano F.Z. da Silva and JOHN L. SPUDICH, Chair AU-0009, (The University of Texas Health Science Center
at Houston), “In Vitro Demonstration of Dual Light-Driven Na+/H+ Pumping by a Microbial Rhodopsin”, Biophysical Journal, 109, 1446-1453,
(2015).
231
49452. Albino Bacolla, JOHN A. TAINER, Chair G-0010, (The University of Texas M. D. Anderson Cancer Center), Karen M. Vasquez and David N.
Cooper, “Translocation and Deletion Breakpoints in Cancer Genomes are Associated with Potential Non-B DNA-Forming Sequences”, Nucleic Acids
Research, 44, 5673-5688, (2016).
49453. Matthew D. Youngblut, Chi-Lin Tsai, Iain C. Clark, Hans K. Carlson, Adrian P. Maglaqui, Phonchien S. Gau-Pan, Steven A. Redford, Alan Wong,
JOHN A. TAINER, Chair G-0010, (The University of Texas M. D. Anderson Cancer Center) and John D. Coates, “Perchlorate Reductase Is
Distinguished by Active Site Aromatic Gate Residues”, The Journal of Biological Chemistry, 291, 9190-9202, (2016).
49454. Curtis D. Hodge, Ismail H. Ismail, Ross A. Edwards, Greg L. Hura, Andrew T. Xiao, JOHN A. TAINER, Chair G-0010, (The University of Texas
M. D. Anderson Cancer Center), Michael J. Hendzel and J. N. Mark Glover, “RNF8 E3 Ubiquitin Ligase Stimulates Ubc13 E2 Conjugating Activity
That Is Essential for DNA Double Strand Break Signaling and BRCA1 Tumor Suppressor Recruitment”, The Journal of biological Chemistry, 291,
9396-9410, (2016).
49455. T. J. Brunette, Fabio Parmeggiani, Po-Ssu Huang, Gira Bhabha, Damian C. Ekiert, Susan E. Tsutakawa, Greg L. Hura, JOHN A. TAINER, Chair
G-0010, (The University of Texas M. D. Anderson Cancer Center) and David Baker, “Exploring the Repeat Protein Universe Through Computational
Protein Design”, Nature, 528, 580-584, (2015).
49456. Ashley J. Pratt, Michael DiDonato, David S. Shin, Diane E. Cabelli, Cami K. Bruns, Carol A. Belzer, Andrew R. Gorringe, Paul R. Langford, Louisa
B. Tabatabai, J. Simon Kroll, JOHN A. TAINER, Chair G-0010, (The University of Texas M. D. Anderson Cancer Center) and Elizabeth D.
Getzoff, “Structural, Functional and Immunogenic Insights on Cu,Zn Superoxide Dismutase Pathogenic Virulence Factors from Neisseria
meningitidis and Brucella abortus”, Journal of Bacteriology, 197, 3834-3847, (2015).
49457. Adreinne S. McCampbell, Megan L. Mittelstadt, Ruhee Dere, Sunam Kim, Lijun Zhou, Bojana Djordjevic, Pamela T. Soliman, Qian Zhang, Caimiao
Wei, Stephen D. Hursting, Karen H. Lu, Russell R. Broaddus and CHERYL LYN WALKER, Chair BE-0023, (Texas A&M University Health
Science Center), “Loss of p27 Associated with Risk for Endometrial Carcinoma Arising in the Setting of Obesity”, Current Molecular Medicine, 16,
252-265, (2016).
49458. Jiangwei Zhang, Durga Nand Tripathi, Ji Jing, Angela Alexander Jinhee Kim, Reid T. Powell, Ruhee Dere, Jacqueline Tait-Mulder, Ji-Hoon Lee,
Tanya T. Paull, Raf K. Pandita, Vijaya K. Charaka, Tej K. Pandita, Michael B. Kastan and CHERYL LYN WALKER, Chair BE-0023, (Texas
A&M University Health Science Center), “ATM Functions at the Peroxisome to Induce Pexophagy in Response to ROS”, Nature Cell Biology, 17,
49476. Jennifer S. Zigmond, Adriana Pavía-Sanders, Joel D. Russell and KAREN L. WOOLEY, Chair A-0001, (Texas A&M University), “Dynamic Anti-
Icing Coatings: Complex, Amphiphilic Hyperbranched Fluoropolymer Poly(Ethylene Glycol) Crosslinked Networks with an Integrated Liquid
Crystalline Comonomer”, Chemistry of Materials, 28, 5471-5479, (2016).
49477. Young H. Lim, Kristin M. Tiemann, David A. Hunstad, Mahmoud Elsabahy and KAREN L. WOOLEY, Chair A-0001, (Texas A&M University),
“Polymeric Nanoparticles in Development for Treatment of Pulmonary Infectious Diseases”, Nanomedicine and Nanobiotechnology, DOI:
10.1002/wnan.1401, (2016).
49478. Samantha L. Kristufek, Guozhen Yang, Lauren A. Link, Brian J. Rohde, Megan L. Robertson and KAREN L. WOOLEY, Chair A-0001, (Texas
A&M University), “Synthesis, Characterization and Cross-Linking Strategy of a Quercetin-Based Epoxidized Monomer as a Naturally-Derived
Replacement for BPA in Epoxy Resins”, ChemSusChem, DOI: 10.1002/cssc.201600392, (2016).
49479. Xun He, Jingwei Fan, Jiong Zou and KAREN L. WOOLEY, Chair A-0001, (Texas A&M University), “Reversible Photo-Patterning of Soft
Conductive Materials via Spatially-Defined Supramolecular Assembly”, Chemical Communications, 52, 8455-8458, (2016).
49480. Yongfeng Zhao, Lisa Detering, Deborah Sultan, Matthew L. Cooper, Meng You, Sangho Cho, Stephanie L. Meier, Hannah Luehmann, Guorong Sun,
Michael Rettig, Farrokh Dehdashti, KAREN L. WOOLEY, Chair A-0001, (Texas A&M University), John F. DiPersio and Yongjian Liu, “Gold
Nanoclusters Doped with 64Cu for CXCR4 Positron Emission Tomography Imaging of Breast Cancer and Metastasis”, ACS Nano, 10, 5959-5970,
(2016).
49481. Kvar C.L. Black, Aida Ibricevic, Sean P. Gunsten, Jeniree A. Flores, Tiffany P. Gustafson, Jeffery E. Raymond, Sandani Samarajeewa, Ritu Shrestha,
Simcha E. Felder, Tianyi Cai, Yuefei Shen, Ann-Kathrin Löbs, Natalia Zhegalova, Deborah H. Sultan, Mikhail Berezin, KAREN L. WOOLEY,
Chair A-0001, (Texas A&M University), Yongjian Liu and Steven L. Brody, “In Vivo Fate Tracking of Degradable Nanoparticles for Lung Gene
Transfer using PET and Ĉerenkov Imaging”, Biomaterials, 98, 53-63, (2016).
49482. Tyler S. Kristufek, Samantha L. Kristufek, Lauren A. Link, Andrew C Weems, Sarosh Khan, Soon-Mi Lim, Alexander T. Lonnecker, Jeffery E.
Raymond, Duncan J. Maitland and KAREN L. WOOLEY, Chair A-0001, (Texas A&M University), “Rapidly-Cured Isosorbide-Based Cross-