INFLUENCE OF SOLUTION PH ON THE ADSORPTION OF MODIFYING AGENTS AND DIRECT ELECTRON-TRANSFER IN THE SYSTEM - GOLD ELECTRODE PROTEIN-FRAGMENTCYTOCHROME-C

Cyclic voltammetry and ellipsometry were used to study the formation o f redox systems: gold electrode - dipeptide - cytochrome c. It was sho wn that the solution pH influences adsorption of the protein fragments , viz., that of the dipeptide CysGly (which promotes direct electron t ransfer) and that of the amino acid cysteine, as well as the resulting redox response of cytochrome c at the gold electrode. An adsorption s cheme was proposed for cysteine and cysteinylglycine adsorption on the gold electrode in acidic, neutral and alkaline solutions, and used to discuss the results obtained when studying the redox changes of cytoc hrome c at dipeptide-modified gold electrodes. The ellipsometric data were used as a basis to suggest a two-step adsorption of cysteinylglyc ine on the gold electrode in alkaline solutions.