Jet-FTIR Studies of Model Peptide Systems Corey A. Rice and Martin A. Suhm Institut für Physikalische Chemie Universität Göttingen Tammannstr. 6 D-37077.

Jet-FTIR Studies of Jet-FTIR Studies of Model Peptide SystemsModel Peptide Systems

Corey A. Rice and Martin A. Suhm

Institut für Physikalische ChemieUniversität Göttingen

Tammannstr. 6D-37077 Göttingen, Germany

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

OutlineOutline

MotivationMotivation Experimental SetupExperimental Setup Model compoundsModel compounds

Formamide, N-Methylformamide and Formamide, N-Methylformamide and

N-MethylacetamideN-Methylacetamide

Protected GlycineProtected Glycine Conclusions and OutlookConclusions and Outlook AcknowledgementsAcknowledgements

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

The Peptide BondThe Peptide Bond

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

NCR

HR

O

MotivationMotivation

Pioneers of Peptide models in the gas phasePioneers of Peptide models in the gas phase Simons, Meijer, Gerhards, Zwier, Pratt, etc.Simons, Meijer, Gerhards, Zwier, Pratt, etc.

The structure of proteins is determined through The structure of proteins is determined through hydrogen bonding motifs (i.e. hydrogen bonding motifs (i.e. -helix, -helix, -sheet -sheet structures, etc.)structures, etc.)

Through N-HThrough N-H......O=C interactionsO=C interactions Secondary, Tertiary and higher-order structures are Secondary, Tertiary and higher-order structures are

extremely hard to determineextremely hard to determine A false Primary structure can lead to a false overall A false Primary structure can lead to a false overall

structure, which leads to many known diseasesstructure, which leads to many known diseases Observe the aggregation of small model systemsObserve the aggregation of small model systems Aggregation patterns can be determinedAggregation patterns can be determined Large aggregates hard to get into the gas phaseLarge aggregates hard to get into the gas phase

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

Experimental IdeaExperimental Idea

Solvent-free studiesSolvent-free studies Through adiabatic expansion Through adiabatic expansion

conditionsconditions TTRR ~ 5 – 20 K ~ 5 – 20 K molecular collisionsmolecular collisions

molecular interactions (i.e. hydrogen bonds)molecular interactions (i.e. hydrogen bonds)

Direct Absorption Infrared Direct Absorption Infrared SpectroscopySpectroscopy

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

Experimental SetupExperimental Setup

filet: fine but lengthy600 x 0.2 mm2

substance

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

New Experimental SetupNew Experimental Setuppoppet-controlled, resistively-heated nozzle

(popcorn-jet)

Sub

stan

ceE

xpa

nsi

on

Magnetic Valve

Check Valves

5 x 1 mm2

h (IR)

2

1 check valve cracking pressure1. 70 mbar2. 680 mbar

175 ms pulse length

p0 = 1.5 – 2.0 bar

pb ~ 10-6 bar

Variable Temp. 298 –

500 K

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

moderate heatingmoderate heating

NH(a)NH(s)

Free

NH

D

Nozzle

Temp.

328 K

298 K

FormamideNozzle Dim./m

m

5 x 1

600 x 0.2

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

Model Compounds: N-H stretch Model Compounds: N-H stretch regionregion

Nozzle

Temp.

298 K

318 K

298 K

Nozzle Dim./m

m

600 x 0.2

5 x 1

600 x 0.2

N-Methylformamide

N-Methylacetamide

Formamide

M

MD T(?)

D

DNH(s)

NH(a)

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

C=O of FormamidesC=O of Formamides

Formamide

N-Methylformamide

Nozzle

Temp.

318 K

328 K

Nozzle Dim./m

m

5 x 1

5 x 1

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

Acetylglycine ethyl ester Acetylglycine ethyl ester N-H stretchN-H stretch

stick spectrum of Ac-Phe-OMea

MD

a Gerhards, M.; Unterberg, C. PCCP, 2002, 4, 1760-1765.

Nozzle Temp. 363 K

p0 / bar 2.0}

2 x C=O

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

Acetylglycine ethyl ester Acetylglycine ethyl ester

Amide I

stick spectrum of Ac-Phe-OMeaa Gerhards, M.; Unterberg, C.; Gerlach, A. PCCP, 2002, 4, 5563-5565.

Nozzle Temp. 363 K

p0 / bar 2.0

D

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

Conclusions and OutlookConclusions and Outlook

New Experimental SetupNew Experimental Setup Model compounds to small protected Model compounds to small protected

peptidepeptide Aggregation patterns are differentAggregation patterns are different

In the future, different protected In the future, different protected peptides without a UV-chromophore peptides without a UV-chromophore in the gas phasein the gas phase High-level High-level ab initioab initio calculations calculations

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

AcknowledgementsAcknowledgements

Prof. Dr. Martin SuhmProf. Dr. Martin Suhm Everyone in the Suhm GroupEveryone in the Suhm Group GRK 782 (www.pcgg.de) funded GRK 782 (www.pcgg.de) funded

through the DFGthrough the DFG

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman

Thank YOU for your attention!

61st International Symposium on Molecular Spectroscopy – TB. Infrared/Raman