Download - Mariano Venanzi [email protected]
Mariano [email protected]
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
Rome, July 3 2013
Peptide Self-Assembled Monolayers
Au
Stable!
Easy!
Denselypacked!Ordered!
Smart!
• Sensing• Tissue Engineering• Electronics• Coating• Surface engineering
Peptide Self-Assembled Monolayers
Applications:Applications:
• Two case studies:
- Electron Transfer through peptide SAMs
- Photosensitive Polypeptide mimicking Elastin
Case study 1: ET through peptide SAMs A bicomponent peptide SAM formed by antiparallely oriented peptides
A8A8PyrPyr/SSA4/SSA4WWAA
Langmuir (2012) 28, 2817-2826Langmuir (2012) 28, 2817-2826
SSA4SSA4WWAA
A8A8PyrPyr
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
295
305315 325 335
345
355
A8Pyr/SSA4WAA8Pyr/SSA4WA
SSA6SSA6
AuAu
A8Pyr/SSA4WAA8Pyr/SSA4WA
PyrPyr
WW
e-
e-
δ-
δ-δ+
δ+
hhνν
junction effectjunction effect
Trp
dipole effectdipole effect
antenna effectantenna effect
Pathway I:Pathway I:through-bridgethrough-bridge+ through-space+ through-space
Pathway II:Pathway II:interchaininterchain
+ through-bridge+ through-bridge
(Au+-S-)
Antenna effectAntenna effect
A8Pyr/SSA4WAA8Pyr/SSA4WA
A8Pyr/SSA6A8Pyr/SSA6
Trp enhances the efficiency of inter-chain ET!
FcFc- CO(- CO(AdtAdt-Ala-Aib)-Ala-Aib)22OMeOMe
S S
CONH
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
Please, buy the book! I get royalties from Wiley.
Peptide Materials.From Nanostructures to Applications.
C. Aleman, A. Bianco, M. Venanzi Eds.
Wiley&Sons (2013)