With density functional theory and non-equilibrium Green function method,we calculate I-V characteristics and transmission spectra of deoxyribonucleotides under low bias.Effect of electrode distance on transverse electronic transport is discussed.As distance between electrodes is less than 1.55 nm,it shows great influence on electronic structures.As the distance is more than 1.55 nm,the energy level near LUMO and HOMO changes slowly and the variation of LUMO-HOMO gap is very small.At a fixed distance between electrodes,the relative current of deoxynucleotides is not changed with lower biases (0.1~0.8 V).The current of T and C increases rapidly and is greater than that of A and G as the bias increases from 0.8 to 1.0 V.

Electronic transport of a two-probe system consisting of Au (111) electrodes and two base pairs sandwiched between Au (111) contacts is investigated with density functional theory combined with non-equilibrium Green's function method.It shows that conductance of base pairs is sensitive to distance between electrodes and oscillates.At a fixed gap between electrodes,transverse transport of base pairs under low bias is calculated and is compared with base pairs with a silver ion.It shows that conductive capability of G-C decreases and that of A-T increases as silver ions are combined with base pairs.