| Self assembled monolayers provide a platform to investigate the charge transport kinetics of DNA through the electrochemical methods of cyclic and square wave voltammetry. DNA was used as a bridge between a donor and acceptor site in an electronically and biologically relevant arrangement. Transport across the DNA bridge was found to be highly sensitive to temperature and structural integrity. Deviation from the well ordered pi-stack, which can be caused by a mismatched base pair, resulted in a change to the charge kinetics. Electrochem- ical signals were monitored by the redox activity of a Nile blue and Perylene redox probe which were attached to the DNA, thus ensuring that the probe was at a definite location and electronically coupled to the base pair pi-stack. The importance of the DNA bridge integrity was investigated by including a single CA mismatch. Comparison to a fully well matched sequence was performed at multiple temperatures, and it was found that the kinetic results of both the well matched and single mismatch duplexes were strongly temperature dependent. An additional study was performed to study the mechanism of DNA charge transport by repositioning the Nile blue probe along the bridge. Repositioning enabled for the investigation into the two dominant theories of DNA charge transport: hopping and superexchange. In this study, it was found that the hopping mechanism was the dominant mechanism. Additionally, the significance of the sequence content and its relationship to charge transport was explored. Using the same experimental setup, the kinetic behavior of a new redox probe was investigated. This new probe, perylene diimide, is included into the duplex via base pair substitution. Continuing, investigation into the dominant charge carrier was explored by using modified bases which included a cyclopropylamine. The cyclopropy- lamine undergoes ring opening upon the transport of an electron or hole. Simulations using a nonlinear least squares analysis were coded, compiled, and used to aid in the acquisition of the kinetic transport rate (k), the electron transport coefficient (alpha), and the redox-active surface coverage (Gamma*) for these systems. All of these results can be used to further develop nanoscale electrical circuits and biological detection assays. |
