title: Charge transfer via a two-strand superexchange bridge in DNA.
abstract: Charge transfer in a DNA duplex chain is studied by constructing a system with virtual electrodes connected at the ends of each DNA strand. The system is described by the tight-binding model and its transport is analyzed by the transfer matrix method. The very weak distance dependence in a long (G:C)(T:A)M(G:C)3 DNA chain observed in experiment [B. Giese, Nature (London) 412, 318 (2001)] is explained by a unistep two-strand superexchange bridge without the need for the multistep thermally induced hopping mechanism or the dephasing effect. The crossover number Mc of the (T:A) base pairs, where crossover between the strong and weak distance dependence occurs, reflects the ratio of intra- and interstrand neighboring base-base couplings.
authors.affiliation: Department of Physics and Astronomy, The University of Manitoba, Winnipeg, Canada, R3T 2N2.
authors.forename: X F
authors.initials: XF
authors.lastname: Wang
authors.forename: Tapash
authors.initials: T
authors.lastname: Chakraborty