Electrochemical behaviour of horse-heart cytochrome-c

A quasi-reversible electrochemical behaviour of horse-heart cytochrome-c is obtained at gold and platinum electrodes in the presence of 4, 4'-bipyridine. Transparent tin-dioxide and glassy-carbon electrodes, modified with pyridine groups, also give rise to a quasi-reversible response of cytochrome-c. From impedance measurements and from cyclic- and ac-voltammetry at the gold an platinum electrodes, reaction rate constants (k0') of 0.6·10-4 to 1.4·10-4 m·s-1 were determined for cytochrome-c in the presence of 4, 4'-bipyridine. In both cyclic- and ac-voltammograms, an adsorption peak is observed at -0.2 V vs. SCE. This peak is ascribed to strong adsorption of both ferri- and ferrocytochrome-c. The 4, 4'-bipyridine molecule creates a suitable interface at the electrode surface. Although no interaction between 4, 4'-bipyridine and cytochrome-c could be detected in solution, a specific interaction is believed to be present between adsorbed 4, 4'-bipyridine and cytochrome-c.