Direct cyclic voltammetry of three ruthenium-modified electron-transfer proteins

A comparison is made between the voltammetric behavior of three electron-transfer proteins and that of their derivatives obtained by attachment of a single Ru(NH 3 ) 5 3+/2+ group to specific histidine (imidazole) residues. The native proteins-plastocyanin from the green alga Scenedesmus obliquus, cytochrome C 551 from Pseudomonas stutzeri, and high-potential iron-sulfur protein from Chromatium vinosum ([4Fe-4S] 3+/2+ center), require the presence of a cationic reagent (neomycin is used here) to promote their interaction and electron exchange with the pyrolytic graphite-«edge» electrode