Thermal and electrochemical gate effects on DNA conductance

In an attempt to understand the complexities of DNA charge transport we have used a scanning tunnelling microscope break junction to repeatedly form a large number of Au-DNA-Au junctions. The DNA is covalently bound to the Au electrodes via gold-thiol bonds, and all measurements are carried out in an aqueous buffer solution to maintain a biological conformation of the duplex. A statistical analysis is carried out to determine the conductance of a single DNA duplex. Previously, we have seen an algebraic dependence of the conductance on length, suggesting a hopping mechanism. To attempt to verify this as the conduction mechanism we have changed the solution temperature and applied an electrochemical gate to the molecular junction to help elucidate the charge transport properties. In an alternating GC sequence with a length of eight base pairs, neither the temperature nor the gate potential caused a significant change in the conductance within the available experimental window.