Mariano Venanzi [email protected]Peptide-based Self-Assembled Peptide-based Self-Assembled Monolayers as a New Tool for Monolayers as a New Tool for Bioinspired Nanotechnology Bioinspired Nanotechnology Biosystems, Energy and Cultural Heritage: aterials Enhancement for Technological Applications Rome, July 3 2013
Biosystems, Energy and Cultural Heritage: Materials Enhancement for Technological Applications Rome, July 3 2013. Peptide-based Self-Assembled Monolayers as a New Tool for Bioinspired Nanotechnology. Mariano Venanzi [email protected]. Peptide Self-Assembled Monolayers. Smart!. - PowerPoint PPT Presentation
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Peptide-based Self-Assembled Monolayers as a Peptide-based Self-Assembled Monolayers as a New Tool for Bioinspired NanotechnologyNew Tool for Bioinspired Nanotechnology
Biosystems, Energy and Cultural Heritage: Materials Enhancement for Technological Applications
A8Pyr (bright dots in the STM image) protrudes by 2Å from the covalently linked SSA4WA monolayer.Each dots has a diameter of 1 nm, typical of 310-helix cross-section.Applied bias: 3.8 VIntensity: 60 pA
STM imagingSTM imaging
I/V curveI/V curve
Cu
rren
t (n
A)
Bias Potential (V)
The high symmetry of the I−V response suggests that there is not a preferred direction for ET, supporting the view of an antiparallel orientation of the two peptide chains.
Photocurrent Generation in anodic conditionsPhotocurrent Generation in anodic conditions
Case study 1: ET through peptide SAMs A peptide horizontally layered on the gold surface
Fc = Ferrocene Adt
The linear dependence of the CV peak intensity on the scan velocity demonstrates that the peptide is covalently linked to the gold surface.
Ip = Nn2F2v/4RT
From this equation, the density of the bound Fc molecules can be easily obtained:
N = (2±1) 10-11 mol/cm2
-5 10-6
0
5 10-6
0.3 0.4 0.5 0.6 0.7 0.8 0.9
255075 100125150175200250
i (A
)
Voltage (V)
-4 10-6
-2 10-6
0
2 10-6
4 10-6
0 50 100 150 200 250 300
i (A
)
scan rate (mV/s)
0,5
1
1,5
2
2,5
3
3,5
0 0,1 0,2 0,3 0,4 0,5
ln (
i /
A)
t (s)
Y = M0 + M1*X
4,006M0
-19,437M1
0,99806R
Y = M0 + M1*X
1,3218M0
-1,5674M1
0,99372R
Chronoamperometry measurements show two different time decays of the current intensity, suggesting two locations of the Fc groups, characterized by different distances from the gold surface.
k(η) = k° exp [(1-α) nFη/RT]
k° = (13 ± 2) s-1
Dependence on the applied bias potential
k° = (1±0.5) s-1
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
0.4 0.6 0.8 1 1.2 1.4
delta E oxDelta E red
log 1/m
Vp
ox (V
)V
p re
d(V
)
α = (0.35±0.07)
XPS
100 200 300 400 500 600 700
O 1s
C 1s
N1s
Au 4d
Inte
nsi
ty (
arb
. units
)
Binding energy (eV)
Au 4f
170 168 166 164 162 160 158
FIT unbound unbound bound bound data
Inte
nsi
ty (
arb
. units
)
Binding Energy ( eV)
S 2p
161.5eV e 162.1eV bonded S
163.7 eV free S
165.3 eV oxidized S
Fc-CO-Aib-Ala-Aib-Adt-Ala-Aib-O-CH3
k0 = (11±3)s-1
-300 -250 -200 -150 -100 -50 0
y = 2.337 - 0.0014163x R= 0.92618
1
1.5
2
2.5
3
3.5
0 50 100 150 200 250 300
y = 2.4056 + 0.001441x R= 0.99191
Case study 2: A photosensitive SAM based on a polypeptide mimicking Elastin
C-[(VPGVG)C-[(VPGVG)22(VPGE(VPGE0.50.5G)(VPGVG)G)(VPGVG)22]]n n (AzoGlu15) (AzoGlu15)
λ=370 nm
Dark or λ=455 nm
E0.5 = 50% of Glutamic residues functionalized with azobenzene molecules
TransCis
Thermal (dark) cis→trans relaxation of AzoGlu15 in a phosphate buffer solution at pH=4 (T=10°C).
The trans isomer is more stable by ~50 kJ·mol-1, while the barrier for photoisomerization is ~200 kJ·mol-1.
CV experiments show that AzoGlu15 forms a densely-packed SAM on a gold surface, inhibiting almost completely the [Fe(CN)6]3+ discharge.Red: bare electrodeBlue: gold electrode modified by the linked AzoGlu15 SAM.
C-(VPGVG)C-(VPGVG)22(VPGE(VPGE0.50.5G)(VPGVG)G)(VPGVG)22]]n n (AzoGlu15) (AzoGlu15)
It shows a pH-dependent sol→gel Inverse Temperature Transition, driven by the extent of hydrophobic interactions.
T < TT < Ttrtr: ordered clathrate-like water structures surrounded the apolar groups. T>TT>Ttrtr: release of water molecules, collapse of polymer chains, phase separation.
pH=2.5
pH=4.0
pH=7.0
Sol→gel
Temperature
transition
pH 2.5 pH 4 pH 7
Trans 24±4 °C 26±4 °C 28±6 °C
Cis 29±4 °C 31±2 °C 33±3 °C
AzoGlu15 with azobenzene in the cis form is less hydrophobic than the trans isomer!
A photoswitchable system for photocurrent generationA photoswitchable system for photocurrent generationP
hoto
curr
ent (
nA)
Pho
tocu
rren
t (nA
)Time (s)
λ (nm)
Trans PG
Cis Abs
Trans AbsThe photocurrent spectrum
can be modulated by selective excitation of the cis or trans form, as determined by the cis-trans equilibrium in dark or ‘light-on’ conditions.
AzoGlu15 Photocurrent in the Trans form
Undecanthiol
Cis PG
Synthesis of conformationally-constrained peptidesSynthesis of conformationally-constrained peptidesClaudio Toniolo, Fernando FormaggioChemistry Dept. – University of Padova (Italy)
Synthesis of photoresponsive peptides mimicking ElastinSynthesis of photoresponsive peptides mimicking ElastinJosé C. Rodriguez-Cabello, Ana M. TexteraDept. Physics of Condensed Matter Dept. – University of Valladolid (Spain)
Lab. of Physical Chemistry of BiomoleculesLab. of Physical Chemistry of BiomoleculesAntonio PalleschiGianfranco BocchinfusoEmanuela Gatto (Photocurrent) Emanuela Gatto (Photocurrent) Claudia MazzucaLorenzo StellaMario Caruso (Photoresponsive polymer/ Adt peptides)Mario Caruso (Photoresponsive polymer/ Adt peptides)Chemistry Dept. Chemistry Dept. – University of Roma Tor Vergata– University of Roma Tor Vergata
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Peptide Materials.From Nanostructures to Applications.