Towards Protein-based Bio- Electronics Electron Transfer & Solid-State Electronic Transport Fundamental differences and similarities with Mordechai Sheves , Israel Pecht Nadav Amdursky, Lior Sepunaru Debora Marchak, Noga Friedman +++++ T U Berlin Nov. 14, 2014 Support Minerva Foundation, Munich Israel Min. of Science
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Towards Protein-based Bio-Electronics Electron Transfer & Solid - State Electronic Transport Fundamental differences and similarities with Mordechai Sheves,
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Towards Protein-based Bio-Electronics
Electron Transfer &
Solid-State Electronic Transport
Fundamental differences and similaritieswith
Mordechai Sheves , Israel PechtNadav Amdursky, Lior Sepunaru
Replacing or removing the Cu ion Zn-azurin or apo-Azurin
Example of ETp measurement: Azurin
Current vs. voltageI-V [ln (I)-V]
@ RT
substrate / contactlinker layer
Ametal
Idealized cartoon
Temperature dependent conduction of “any (> ~2 nm) peptide skeleton”
2 4 6 8 10 12-18
-17
-16
-15
-14
-13
-12
BSA apo-Azurin
Cu
rren
t d
ensi
ty [
mA
/cm
2 ]
1000/T [K-1]
400 300 200 100T [K]
5
Temperature independent
Thermally activated
Electron Transport Mechanism
BovineSerum
Albumin
Some proteins “survive”partial dehydration
“SOLID-STATE” ELECTRON TRANSPORT (ETP)
10 20 30 40 50 60 70 80 90 1001E-26
1E-24
1E-22
1E-20
1E-18
1E-16
1E-14
1E-12
1E-10
1E-8 macroscopic
Saturated Conjugated Proteins
Cur
rent
Den
sity
(A/n
m2 )
Length (Å)
32 33 34 351E-18
1E-17
substrate / contactlinker layer
Ametal
Idealized cartoon
Amdursky et al., Adv. Mater. 2014
IdealizedCartoons!
We (can) also use nanoscale contacts; let’s take a closer look at such experiments:
A
10 nm
Metallic substrate
2 μm
9
Nanoscale contacts – Azurin
Holo-Az Apo-Az
-0.5 0.0 0.51E-5
1E-4
1E-3
0.01
0.1
1 holo-Az 12nN
holo-Az 6nNapo-Az 12nN
Cur
rent
(nA
)
Bias (V)
apo-Az 6nN
WIS group, ACS Nano 2012Davis group, JMC 2005
10
0 5 10 15 20 250
5
10
15
20
25R
esis
tan
ce (
G
)
Applied force (nN)
0 5 10 150
5
10
15
20
25 WT-bR WT-Azurin
Res
ista
nce
(G
)
Applied Force (nN)
Applied force-dependent conductance
Elastic regime
Plastic regime
Li et al. ACS Nano, 2012Mukhopadhyay et al., ACS Nano (2014)
Azurin
bR
@RT
11
e-
e-
hν
In solid state In solution
ETp ET
Spectroscopy Electrochemistry
e-
How does Electron Transport (ETp) differ from Electron Transfer (ET)?
ETp is measured with electronically conducting electrodes that• are ionically blocking • have delocalized electron systems (affects reorganization energy)
ET is measured without electrodes (or with one ionically conducting, electronically blocking contact)
How does Electron Transport (ETp) differ from Electron Transfer (ET)?
ETp is measured with electronically conducting electrodes that• are ionically blocking • have delocalized electron systems (affects reorganization energy)
ET is measured without electrodes (or with one ionically conducting, electronically blocking contact)
-----------------------------------------------------------------------ETp is measured on proteins outside their natural environment
• in partially “dry” state, with only tightly bound water kept(but with natural conformation closely preserved)
ET is measured with protein in, or partially exposed to solution.
How does Electron Transport (ETp) differ from Electron Transfer (ET)?
ETp is measured with electronically conducting electrodes that• are ionically blocking • have delocalized electron systems (affects reorganization energy)
ET is measured without electrodes (or with one ionically conducting, electronically blocking contact)
-----------------------------------------------------------------------ETp is measured on proteins outside their natural environment
• in partially “dry” state, with only tightly bound water kept(but with natural conformation closely preserved)
ET is measured with protein in, or partially exposed to solution. -----------------------------------------------------------------------ETp: no redox reaction required can study ETp close to equilibrium (@0.05 V)ET : redox reaction required (coupled to ion transport for charge balance)
How does Electron Transport (ETp) differ from Electron Transfer (ET)?
ETp is measured with electronically conducting electrodes that• are ionically blocking • have delocalized electron systems (affects reorganization energy)
ET is measured without electrodes (or with one ionically conducting, electronically blocking contact)
-----------------------------------------------------------------------ETp is measured on proteins outside their natural environment
• in partially “dry” state, with only tightly bound water kept(but with natural conformation closely preserved)
ET is measured with protein in, or partially exposed to solution. -----------------------------------------------------------------------ETp: no redox reaction required can study ETp close to equilibrium (@0.05 V)ET : redox reaction required (coupled to ion transport for charge balance) ------------------------------------------------------------------------BUT ETp may be differ from ET if• pressure is applied (e.g., in SPM)• significant (> 1-1.5 V bias voltage) is imposed• electronic current flows• ………………………… ………
How does Electron Transport (ETp) differ from Electron Transfer (ET)?
• Effect of protein redox activity (for CytC)
• Redox site effect on conduction (for Az)
(also can add redox site in bR)
• Effect of protein-electrode coupling
How does Electron Transport (ETp) differ from Electron Transfer (ET)?
280 320 360 400 440
Nor
mal
ized
Flu
ores
cenc
e (a
.u)
Wavelength (nm)
HSA
HSA-hemin
Case Study – I‘Doping’ serum albumin with hemin
& comparison with Cyt C
Some ETp-ET differences :
• Effect of protein redox activity
-1.0 -0.5 0.0 0.5 1.0
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
-1.0 -0.5 0.0 0.5 1.0
-0.002
0.000
0.002
0.004
Cur
rent
Den
sity
(A
/cm
2 )
Bias (V)
HSA
HSA-hemin
-1.0 -0.5 0.0 0.5 1.0
-0.002
0.000
0.002
0.004
Cur
rent
Den
sity
(A
/cm
2 )
Bias (V)
CytC HSA-hemin
-1.0 -0.5 0.0 0.5 1.01E-8
1E-7
1E-6
1E-5
1E-4
1E-3
‘Doping’ serum albumin with hemin& comparison with Cyt C
Amdursky et al., PCCP 2013
Some ETp-ET differences :
• Effect of protein redox activity
0 5 10 15 20 25 30 35
-17
-16
-15
-14
-13
-12
ln
(J@
-0.0
5V)
1000/T
HSA
HSA-hemin
0 5 10 15 20 25 30 35-16
-15
-14
-13
-12
HSA-hemin CytC electrostatic
ln(J
@-0
.05V
)1000/T
95 meV
220 meV
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
-0.0010
-0.0005
0.0000
0.0005
0.0010
Cur
rent
Bias
-0.4 -0.2 0.0 0.2 0.4 0.6-0.0012
-0.0008
-0.0004
0.0000
0.0004
0.0008
Cur
rent
Bias
HSA-heminCytC
kET ≈ 18 s-1
kET ≈ 5 s-1
‘Doping’ serum albumin with hemin& comparison with Cyt C
Amdursky et al., PCCP 2013
0 10 20 30 40
-12
-10
-8
-6
ln
(J@
0.05
V)
1000/T
100 meV
Fe
0 10 20 30 40-16
-14
-12
-10
-8
-6
-4
ln
(J@
0.05
V)
1000/T
Iron-free CytC
Holo-CytC
Apo-CytC
Cyt C electrostatically bound (physisorbed) to surface
Amdursky et al., JACS 2013
‘Doping’ serum albumin with hemin& comparison with Cyt C
Some ETp-ET differences :
• Effect of protein redox activity
-1.0 -0.5 0.0 0.5 1.0
-0.002
0.000
0.002
0.004
CytC Iron free CytC
Bias (V)
Cur
rent
Den
sity
(A
/cm
2 )
-1.0 -0.5 0.0 0.5 1.0-0.004
-0.002
0.000
0.002
0.004
HSA-hemin HSA-PPIX
Cur
rent
Den
sity
(A
/cm
2 )
Bias (V)
-0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5
-200
-100
0
100
200 HSA-hemin HSA-PPIX
Cur
rent
(nA
)
Bias vs. SCE (V)
-0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5
-300
-200
-100
0
100
200
300 CytC Iron free CytC
Cur
rent
(nA
)
Bias vs. SCE (V)
The conjugated porphyrin ring, not the Fe ion, is the main ETp mediator,
while in ET the Fe2+/3+ redox process controls the electron transfer.
Amdursky et al., PCCP 2013
‘Doping’ serum albumin with hemin& comparison with Cyt C
)(A
TkE
AeI b
2 4 6 8 10 12
-20
-19
-18
-17
-16
-15
-14
-13
-12
Holo-Az
1000/T [K-1]
ln(J
@+
0.05
V)
Cu ion removal
300 meV
Sepunaru et al., JACS 2011
2 4 6 8 10 12
-20
-19
-18
-17
-16
-15
-14
-13
-12
Apo-Az
Holo-Az
1000/T [K-1]
ln(J
@+
0.05
V)
CASE STUDY-IIAZURINSome ETp – ET differences:
• Redox site effect on conduction
2 4 6 8 10 12-20
-18
-16
-14
-12
ln J
[+
50 m
V]
1000/T [K-1]
400 300 200 100T [K]
Cu-Az
Ni-Az
Co-Az
Zn-Az
TBP
Cu ion replacement
Some ETp – ET differences: • Redox site effect on conduction
AZURIN
0 5 10 15 20 25 30 35
-18
-17
-16
-15
-14
-13
-12holo-Az - Protonated
holo-Az - Deuterated
apo-Az - Deuterated
1000/T
ln(J
@0.
05V
)
apo-Az - Protonated
Amdursky et al., PNAS 2013 and TBP
AZURINSome ETp – ET differences: • Redox site effect on conduction
-1.0 -0.5 0.0 0.5 1.0
-6
-5
-4
-3
-2
-1
0
1
2
3
Cur
rent
(A
)
Bias (V)
Cu+2
Cu+1
2 4 6 8 10 12 14 16
-12
-11
-10
-9
-8
-7
+0.5V +0.2V +0.05V -0.05V -0.2V -0.5V
ln(J
)
1000/T
5 10 15 20 25
-13
-12
-11
-10
-9
-8
-7
+0.5V +0.2V +0.05V -0.05V -0.2V -0.5V
ln(J
)
1000/T
Cu(I) vs. Cu(II) Az
Some ETp – ET differences:
• Redox site effect on conduction TBP
@RT
AZURIN
CASE STUDY-IIIETP WITH CYT C MUTANTS
Amdursky et al., PNAS 2014
with Dmitry Dolgikhd & Rita ChertkovadShemyakin-Ovchinnikov Inst. Bioorg. Chem., RASCarlo Bortolotti, U Modena