Additive transport in DNA molecular circuits

Abstract

This work describes additive transport in DNA molecules due to a self-assembly of complementary single-stranded deoxyribonucleic acid chains, i.e. DNA hybridization. Charge transport properties in the DNA junctions at the single molecule level were studied experimentally by the break junction technique in an aqueous environment and theoretically including a non-equilibrium Green's function approach within the density functional based tight-binding method and molecular orbital calculations using density functional method and molecular dynamics simulations. Two types of anchoring groups, namely, amino and thiolate moieties were used to connect the single-stranded DNA (anchor-linker-3′-GGCACTCGG-5′-linker-anchor) to gold electrodes. Double-stranded DNA junctions were prepared by hybridization of single-stranded DNA with a complementary oligonucleotide chain (5′-CCGTGAGCC-3′) not containing linkers and anchoring groups. Three stable junction configurations were observed for both single-stranded and double-stranded DNA irrespective of the anchoring group, whereas junction conductance almost doubled upon DNA hybridization. Thiolate anchoring led to more robust and longer junction configurations compared to NH₂ groups. Reasons for the observed conductance enhancement and the anchoring group effect on the overall conductance are being discussed.