Electrochemical behaviour of horse‐heart cytochrome‐c

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Abstract
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.
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