Distance dependence of charge carrier injection into DNA

Kinetic scheme for hole injection, hopping and trapping in DNA

E

(X+)*

Hole Trap

G G

A A

C CT T

G

A

CT

X+

N

HN

OOP

H

O

OO-

Cl

MeO

X+-Labeled DNA duplexes

3‘ 5‘

A X+

T A

T A

GC

T A

A

T A

T A

T A

X+

GC

3‘ 5‘

A

T A

T A

X+

T A

GC

3‘ 5‘

XAG

X+AG

1(X+)*AG

0

0.5

1.0

Wavelength [nm]

Ab

sorb

ance

/Flu

ores

cen

ce

[a.u

.]

400 600500

Structural Characterization

• Melting Points• CD Spectra• NMR Structure

transition dipole moments of ACMA vs. duplex axis: ~70-75° consistent with time-resolved fluorescence polarisation (65-90°)

H6,H8 H1‘

H2‘‘

H2‘

MeasuredCalculated

Restraints :• NOEs (136 intra DNA + 7 inter ACMA-DNA) 0 violations (>0,2 Å)• Anisotropy of chemical shifts

QF-ACMA-NMR Struktur 1 03-10-21.ppt

NMR structure of 5‘ GCGTAAX+AATGCG duplex

Griesinger/Neubauer 2003

Kinetics of photo-induced guanine oxidation via (X+)*

-1 0 10 100 1000

-1,0

-0,5

0,0

0,5

1,0

455 nm Pump / 500 nm Probe

X+(AT) X+G X+AG

A (

a.u.

)

Time (ps)

X+AT CGC TAT TAT TAX+ ATT TAT CGC-3’

X+GA GCG TTA TAA GX+A TAA TAT GCG-3’

X+AGA GCG TTA TAG AX+A TAA TAT GCG-3’

Duplex ES (ns) CS (ns) CR (ns)X+G 0.003 0.003 0.030X+AG 6.9 11.2 ----X+ AT 18.0 ---- ----

kG / kAG ~ 4000“” ~ 2.4 Å-1

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

2

22 1exp

4 ( )4 ( )DA

G R Rk H R

R kTR kT

X+Z 5’-GCG TTA TAA ZX+A TAA TAT GCGX+AZ 5’-GCG TTA TAZ AX+A TAA TAT GCGX+AAZ 5’-GCG TTA AZA AX+A TAA TAT GCG

NH

O

PO O

O

O

PO O

O NH

Cl

H3CO

+

[

[

X+ =

Distance dependent activation energy of hole transfer rates in DNA duplex

Temperature Range: 245-305 K

HF-Analysis of Ea and k-03-10-21.ppt

How to analyze activation energies and rates

TkE

expT

Ak

B

a21

2

/)λ(V

A

weak contribution

Duplex Ea [eV] kFET [s-1]

(T=285 K) [s-1]

X+Z < 0.015 2.0 1012 6.2 1013

X+AZ 0.09 ± 0.01 9.3 1010 6.3 1013

X+AAZ 0.20 ± 0.02 4.6 107 2.8 1012

X+G 0.08 ± 0.04 2.0 1011 9.1 1013

X+AG 0.20 ± 0.04 6.5 107 4.0 1012

4

GE

2

a

Tk/EFET

BaeTkA

Distance dependence of reorganisation energy

λ

λGEa

4

2

Duplex Ea [eV] FET [eV]

X+G 0.08 ± 0.04 0.6 ± 0.1

X+AG 0.20 ± 0.04 1.0 ± 0.2

X+Z < 0.015 0.6 ± 0.1

X+AZ 0.09 ± 0.01 1.1 ± 0.1

X+AAZ 0.20 ± 0.02 1.4 ± 0.1

+ + ½ + ½

Small D/A distance&Smaller

Large D/A distance&Larger

Initial states Transition states

+ + ½ + ½

Reorganisation energy for the simple case of a self-exchange reaction

(G=0)

sopDAs εεRrr

)e(λ111

2

1

2

1

21

2

Distance dependence of the medium reorganization energy

stopDAADs Rrr

e

11121

21

)( 2

Marcus Two-Sphere-Model:

rD rA 4.5 Å

Optimization of charge transport energetics

Minimization of medium reorganization energy

• Short D/A distances

• Nonpolar environment

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