Hole Mobility in DNA A Tracts

摘要

A unique feature of electron transfer in duplex DNA is the ability of positive charge (holes) to migrate over long distances in poly(dA)-poly(dT) base pair domains,[1], [2] known as A tracts.[3] A hopping has been observed in numerous studies of oxidative strand cleavage at GG and GGG sites.[4]-[6] Giese et al. reported that the relative efficiency of hole transport from an isolated oxidized G to a GGG hole trap separated by a variable number of A-T base pairs (bp) displayed a highly distinctive distance dependence.[7] The relative efficiency of hole transport was observed to be highly distance dependent at short distances (1-3 bp) but weakly distance dependent at longer distances (4-16 bp). This change was attributed to a change in mechanism from tunneling at short distances to multistep hole hopping at longer distances. Giese's report prompted numerous theoretical analyses[8]-[12] as well as experimental efforts to determine the rate constants for hole transport through A hopping.