Distance dependence of charge carrier injection into DNA

1
Distance dependence of charge carrier injection
into DNA
2
Kinetic scheme for hole injection, hopping and
trapping in DNA
E
C
T
T
C
C
T
A
A
A
(X)
G
G
G
Hole Trap
X
3
X-Labeled DNA duplexes
1(X)AG
0 0.5 1.0
XAG
XAG

• Structural Characterization
• Melting Points
• CD Spectra
• NMR Structure

4
NMR structure of 5 GCGTAAXAATGCG duplex
Restraints NOEs (136 intra DNA 7 inter
ACMA-DNA)
0 violations (gt0,2 Å) Anisotropy of chemical
shifts
transition dipole moments of ACMA vs. duplex
axis 70-75 consistent with time-resolved
fluorescence polarisation (65-90)
Griesinger/Neubauer 2003
QF-ACMA-NMR Struktur 1 03-10-21.ppt
5
Kinetics of photo-induced guanine oxidation via
(X)
XAT CGC TAT TAT TAX ATT TAT CGC-3 XGA
GCG TTA TAA GXA TAA TAT GCG-3 XAGA GCG TTA
TAG AXA TAA TAT GCG-3
Duplex tES (ns) tCS (ns) tCR (ns) XG 0.003 0.003
0.030 XAG 6.9 11.2 ---- X AT 18.0 ---- ----
kG / kAG 4000 b 2.4 Å-1
6
Factors controlling nonadiabatic charge transfer

• Marcus formula
• classical nuclear dynamics
• ET rate k determined by distance dependant 3
  terms
• effective electronic coupling HDA
• free energy change ?G
• reorganization energy ?

7
Distance dependent activation energy of hole
transfer rates in DNA duplex
XZ 5-GCG TTA TAA ZXA TAA TAT GCG XAZ
5-GCG TTA TAZ AXA TAA TAT GCG XAAZ
5-GCG TTA AZA AXA TAA TAT GCG
Temperature Range 245-305 K
8
How to analyze activation energies and rates
Duplex Ea eV kFET s-1 (T285 K) s-1
XZ lt 0.015 2.0 ? 1012 6.2 ? 1013
XAZ 0.09 0.01 9.3 ? 1010 6.3 ? 1013
XAAZ 0.20 0.02 4.6 ? 107 2.8 ? 1012
XG 0.08 0.04 2.0 ? 1011 9.1 ? 1013
XAG 0.20 0.04 6.5 ? 107 4.0 ? 1012
HF-Analysis of Ea and k-03-10-21.ppt
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Distance dependence of reorganisation energy
Duplex Ea eV FET l eV
XG 0.08 0.04 0.6 0.1
XAG 0.20 0.04 1.0 0.2
XZ lt 0.015 0.6 0.1
XAZ 0.09 0.01 1.1 0.1
XAAZ 0.20 0.02 1.4 0.1
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Reorganisation energy ? for the simple case of a
self-exchange reaction (?G0)
Small D/A distance Smaller ?

½
½
½

½
Large D/A distance Larger ?
Transition states
Initial states
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Distance dependence of the medium reorganization
energy
Marcus Two-Sphere-Model
rD ? rA ? 4.5 Å
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Optimization of charge transport energetics

• Minimization of medium reorganization energy
• Short
• D/A distances
• Nonpolar
• environment

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On the distance dependence of charge transfer in
DNA Who did the work?
M.E. Michel-Beyerle Group Design of
Oligonucleotides and fs pump-probe spectroscopy
Stephan Hess (Thesis 2002) M. Götz (Thesis
2002) William B. Davis (now at Washington
State at Pullman) Till von Feilitzsch
Gagik Gurzadyan at present Nanosecond
pump-probe spectroscopy Isabella.
Naydenova, Reinhard Haselsberger Alex
Ogrodnik Collaborations Fs Broadband
Absorption spectrocopy N. P. Ernsting , S.
A. Kovalenko J. L. Pérez Lustres (HU Berlin)
NMR Structure C. Griesinger H.
Neubauer (MPI Göttingen) Thermal Injection
Charge Transport B. Giese (U. Basel)
Quantum Chemical Computations MD Simulations
N. Rösch A. Voityuk (TU München)
Modelling of Charge Transfer Transport
Dynamics M. Bixon J. Jortner (Tel Aviv
U.) M. D. Newton (Brookhaven)
Funding VW-Stiftung DFG SFB 377 EU 5th 6th
Frame Program