Fluctuation of the electronic coupling in DNA: Multistate versus two-state model

The electronic coupling for hole transfer between guanine bases G in the DNA duplex (GT)6GTG(TG)6 is studied using a QM/MD approach. The coupling V is calculated for 10 thousand snapshots within the two- and multistate state Generalized Mulliken–Hush model. We find that the two-state scheme considerably underestimates the rate of the hole transfer within the π stack. Moreover, the probability distributions computed with the two- and multistate schemes are quite different. It has been found that large fluctuations of V2, which are at least an order of magnitude larger than its average value, occur roughly every 1 ps.