Nucleic acid-promoted electron transfer to cytochrome c

Gold electrodes were modified with short oligonucleotides in order to facil itate the electron transfer to the small redox protein cytochrome c. DNA im mobilization was followed by impedance spectroscopy. The electron exchange was found to be quasi-reversible for both the protein in solution or adsorb ed at the electrode surface. Variations of base sequence or structure (DNA- PNA hybrids) of the nucleic acid promoter layer did not significantly chang e the electron transfer rate constant which was in the range of 0.2-1 x 10( -2) cm/s. Cytochrome c adsorbed at low ionic strength was coupled to molecu les in solution such as superoxide or laccase. Aspects of the DNA conductiv ity and possibilities for DNA detection are also discussed.