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Quantum chemical and molecular dynamics modeling of charge transfer in DNA

A. A. Voityuk ( voityuk-AT-theochem-DOT-tu-muenchen-DOT-de.gif )
Dept. Theoretical Chemistry, Technical University of Munich, 85747 Garching, Germany.

The efficiency of charge transfer (CT) in DNA is determined by three key parameters- the donor-acceptor electronic coupling, the CT driving force, and the solvent reorganization energy.Computational approaches to estimating these parameters are considered. A new method, fragment charge difference scheme, for estimating the electronic coupling is introduced. The method can be applied to systems with several donor acceptor sites which are off resonance and shows a high performance when treating the the electronic coupling in DNA. A combined QM/MD method to calculate couplings is discussed. Results of calculations on energetics of CT in DNA are presented. Stabilization of the radical cation state localized on a base in 5'-XBY-3' is shown to be essentially affected by the by subsequent base Y while the effect of the preceding base X is small. A considerable influence of thermal fluctuations of DNA environment on the CT energetics is found. Calculational results on the reorganization energy and its dependence on donor-acceptor distance, charge delocalization and structural fluctuations are presented.