Temperature dependence of electrochemical DNA charge transport: influence of a mismatch.

Charge transfer through DNA is of interest as DNA is both the quintessential biomolecule of all living organisms and a self-organizing element in bioelectronic circuits and sensing applications. Here, we report the temperature-dependent properties of DNA charge transport in an electronically relevant arrangement of DNA monolayers on gold under biologically relevant conditions, and we track the effects of incorporating a CA single base pair mismatch. Charge transfer (CT) through double stranded, 17mer monolayers was monitored by following the yield of electrochemical reduction of a Nile blue redox probe conjugated to a modified thymine. Analysis with cyclic voltammetry and square wave voltammetry shows that DNA CT increases significantly with temperature, indicative of more DNA bridges becoming active for transport. The mismatch was found to attenuate DNA CT at lower temperatures, but the effect of the mismatch diminished as temperature was increased. Voltammograms were analyzed to extract the electron transfer rate k(0), the electron transfer coefficient α, and the redox-active surface coverage Γ*. Arrhenius behavior was observed, with activation energies of 100 meV for electron transfer through well-matched DNA. Single CA mismatches increased the activation energy by 60 meV. These results have clear implications for sensing applications and are evaluated with respect to the prominent models of DNA CT.