ELECTROCHEMISTRY OF CYTOCHROME-C - INFLUENCE OF COULOMBIC ATTRACTION WITH INDIUM TIN OXIDE ELECTRODE

The electrochemistry of cytochrome c was investigated using an indium tin oxide electrode. The electrochemistry was highly dependent not only on the purity of cytochrome c but also on the ionic strength mu of the electrolyte. Purified cytochrome c showed stable and quasi-reversible responses at mu = 0.1-0.5 M, while it showed stable but weaker responses with an asymmetric peak current at mu < 0.1 M, suggesting the influence of adsorption on the electrode. Unpurified cytochrome c containing the polymeric and deaminated forms also showed stable and quasi-reversible responses at mu = 0.3-0.5 M, but it showed dramatically deteriorated responses with scan-to-scan decay at mu < 0.3 M. From analysis of the electrochemistry, the denatured ** impurities of cytochrome c which deposit onto the electrode were assumed to block the electron transfer. Low responses with large peak separation were observed at mu > 0.6 M. The responses were assumed to be due to the shielding of the coulombic attraction of cytochrome c. Guanidinated cytochrome c behaved similarly to unpurified cytochrome c.