Electrical conductance in duplex DNA: Helical effects and low-frequency vibrational coupling

In this work we consider the combined effect of helical structure and base-pair twist motion on charge transfer through duplex DNA at low temperatures. We present a fully analytical treatment of charge-lattice coupled dynamics in terms of nearest-neighbor tight-binding equations describing the propagation of the charge through an effective linear lattice for certain frequency values. The corresponding effective hopping terms include both helicoidal and dynamical effects in a unified way. Although base-pair motion generally reduces pi-pi stack overlapping, the coupling to certain normal modes gives rise to a significant improvement of the Landauer conductance