Charge transport in a double-stranded DNA: Effects of helical symmetry and long-range hopping.

Within a tight-binding framework, we examine conformation-dependent charge transport properties of the DNA double-helix, including helical symmetry and the possibility of multiple charge conduction pathways. Using techniques based on the Green's function method, we inspect changes in the localization properties of DNA in the presence of long-range hopping, with varying disorder strength. We study three characteristic DNA sequences, two periodic and one random. We observe that, in all cases, due to disorder-induced delocalization, the localization length variation is similar. We also investigate the effect of backbone energetics on current-voltage (I-V) responses, using the Landauer-Büttiker formalism. We find that, in the presence of helical symmetry and long-range hopping, due to environmental effects, DNA can undergo a phase transition from semiconductor to insulator.