Fc–ssDNA conjugate: electrochemical properties in a borate buffer and adsorption on gold electrode surfaces

By using an electroactive species such as ferrocene (Fc), the electrochemical properties of bioorganic molecules were indirectly made accessible. 5′-Fc-NH-ssDNAs have a redox potential of 430–440 mV (vs. Ag|AgCl) in a borate buffer (pH 9), which is characteristic of ferrocene/ferrocenium (Fc/Fc+) substituted by an amide group. The diffusion coefficient of Fc–ssDNA conjugates in a buffer solution was found to be 10−7 cm2 s−1. 5′-Fc-NH-ssDNA-S-S-R (3) was adsorbed onto a gold microelectrode surface to form a self-assembled monolayer (SAM) via a disulfide linker with a high packing density. The Fc-electrophore allows the characterization of the SAM by cyclic voltammetry (CV). The rate constant of electron transfer through DNA was estimated to be 12 s−1.