Atomistic Models of DNA Charge Transfer

In Chap. 4, Koslowski and Cramer address the phenomenon of charge transport in DNA using a simple, but chemically specific approach intimately related to the Su-Schrieffer-Heeger model. In that model, the Hamiltonian is carefully parameterized using the ab-initio density-functional calculations. In the presence of an excess positive charge, the emerging potential energy surfaces for hole transfer are found to correspond to the formation of small polarons localized mainly on the individual bases. Thermally activated hopping between these states is analyzed using the Marcus theory of charge transfer. Their results are fully compatible with the conjecture of long-range charge transfer in DNA via two competing mechanisms, and the computations provide the corresponding charge-transfer rates both in the short-range superexchange and in the long-range hopping regime as the output of a single atomistic theory. Furthermore, it reproduces the order of magnitude of the current flow in DNA-gold nanojunctions, the over all shape of the current-voltage curves and their dependence upon the DNA sequence.