Small polaron hopping transport along DNA molecules

Abstract

We present a small polaron hopping model for interpreting the strong temperature(T) dependence of theelectrical conductivity, σ, observed at high (h) temperatures along DNA molecules. The model takes into accountthe one-dimensional character of the system and the presence of disorder in the DNAdouble helix. Percolation-theoretical considerations lead to analytical expressions for thehigh temperature multiphonon-assisted small polaron hopping conductivity, the hoppingdistance and their temperature dependence. The experimental data for lambda phage DNA(λ-DNA) and poly(dA)–poly(dT) DNA follow nicely the theoretically predicted behaviour(lnσh∼T−2/3). Moreover, our model leads to realistic values of the maximum hopping distances,supporting the idea of multiphonon-assisted hopping of small polarons between nextnearest neighbours of the DNA molecular ‘wire’. The low temperature case is alsoinvestigated.