Pathway Analysis on DNA Charge Transfer through Adenine and Guanine Bridges^†

Long-range DNA charge transfer dynamics of 5'-GA(n)GA(m)G(3)-3' (n = 1, 2, m = 1-3) sequences have been explored on a quantitative basis. First, the degree of coherence was determined in terms of coherence length. Second, relative contribution of charge transfer mechanisms such as incoherent (nearest-neighbor) hopping, through-bridge, and superexchange as well as C-hopping mechanism was assessed by the density matrix decomposition based on the path integral formalism. Finally, time evolution of individual trajectory contribution was investigated through pathway analysis. Although C-hopping pathways were indeed found to be crucial, we have also shown that the initial transfer is driven by the nearest-neighbor hopping pathways through energetically less favored adenines followed by G-hopping pathways. Therefore, not only the G-hopping pathways but also the through-adenine pathways govern the overall long-range DNA charge transfer. By placing guanines no farther than two adenines apart, one can fully utilize efficient tunneling between guanines for long-range DNA charge transfer.