Conformation and local environment dependent conductance of DNA molecules

DNA conformation and local molecular environment dependant conductance of thiolated 16-base-pair, double stranded DNA on Au(111), was studied using ultrahigh-vacuum scanning tunneling microscopy (UHV/STM) and spectroscopy (STS). The increased conductance was found to occur due to flattened DNA molecules with individual aromatic base pairs mediating the current between the STM tip and Au surface. Isolated molecules were found to exhibit larger band gaps but had higher conductance at voltages above the band-gap threshold. The results showed a conformation-dependent effect on the conductance of DNA molecules. Conformational changes were found to occur due to a re-orientation of the DNA molecules with respect to the substrate due to the applied field. The DNA environment had a significant effect on the density of states and tunneling current, while the electronic properties of DNA were found sensitive to the experimental conditions.