Electrochemistry of ferredoxin and c-type cytochromes at surfactant film-modified pyrolytic graphite electrodes

Pyrolytic graphite electrodes cast with multilayer films of didodecyldimethylammonium bromide (DDAB) or lauric acid (LA) are used to study the electrochemical behaviour of spinach ferredoxin and multiheme cytochromes c(3) (from Desulfovibrio vulgaris Hildenborough, D. desulfuricans Norway and D. gigas). As shown by the pH-dependence of their electrochemical behaviour, DDAB films act as anion exchanger, incorporating the redox proteins upon repetitive cycling, provided they bear a global negative charge. Results support the electrostatic nature of the interactions between negatively (or positively) charged redox species and positively (or negatively) charged headgroups in the DDAB (or LA) films, respectively. Because of the appearance of a new voltammetric couple at less negative potentials, it can be assumed that modifications of cytochrome c(3) incorporated within the multilayer DDAB or LA films occur upon repetitive cycling. Copyright (C) 1996 Elsevier Science Ltd