Sequence Dependence of Electronic Transport in DNA

We study electronic transport in long DNA chains using the tight-binding approach for a ladder-like model of DNA. We find insulating behavior with localizaton lengths ξ ≈ 25 in units of average base-pair seperation. Furthermore, we observe small, but significant differences between λ-DNA, centromeric DNA, promoter sequences as well as random-ATGC DNA. 1 Introduction DNA is a macro-molecule consisting of repeated stacks of bases formed by either AT (TA) or GC (CG) pairs coupled via hydrogen bonds and held in the double-helix structure by a sugar-phosphate backbone. In most models of electronic transport [1, 2] it has been assumed — following earlier pioneering work [3, 4] — that the transmission channels are along the long axis of the DNA molecule and that the conduction path is due to π-orbital overlap between consecutive bases [5]. A simple quasi-1D model incorporating these aspects has been recently introduced [6], building on an earlier, even simpler 1D model [1]. For the model, electronic transport properties have been investigated in terms of localisation lengths [6, 7], crudely speaking the length over which electrons travel. Various types of disorder, including random potentials, had been employed to account for different real environments. It was found that random and λ-DNA have localisation lengths allowing for electron motion among a few dozen base pairs only. However, poly(dG)-poly(dC) and also telomeric-DNA have much larger electron localization lengths. In Ref. [6], a novel enhancement of localisation lengths has been observed at particular energies for an increasing binary backbone disorder.