Interbase electronic coupling for transport through DNA

Abstract

We develop an approach to derive single-state tight-binding sSSTBd model for electron transport in the vicinity of valence-conduction bands of polysGd-polysCd and polysAd-polysTd DNA. The SSTB parameters are derived from first principlesand are used to model charge transport through finite length DNA. We investigate the rigor of reducing the full DNA Hamiltonian to SSTB model. While the transmission coefficient spectrum is preserved, its position shifts in energy. Thymine is poorly represented and its peak height is substantially reduced. This is attributed to the abstraction of the HOMO-LUMO sHOMO, highest occupied molecular orbital; LUMO, lowest unoccupied molecular orbitald coupling to other eigenstates in the nearest-neighbor DNA bases, and can be corrected within second-order time-independent perturbation theory. Interstrand charge transport has also been analyzed and it is found that hopping to the nearest neighbor in the complementary strand is the most important process except in the valence band of polysGd-polysCd, where hopping to the second nearest neighbor between 38-ends is the most dominant process. As a result, transport between 38-ends and 58-ends in the vicinity of valence band of polysGd-polysCd is asymmetric.