LIPID-MODIFIED PYROLYTIC-GRAPHITE ELECTRODES FOR THE STUDY OF NEGATIVELY CHARGED SPECIES

Pyrolytic graphite (PG) electrodes are coated with films of dodecylamine (DDA), dimethyldioctadecylammonium bromide (DODAB) or composite layers based on a mixture of phosphatidylcholine (PC) and cholesterol (CH). Cyclic voltammetry is used to investigate the incorporation of two negatively charged species, Fe(CN)(6)(3-) and spinach ferredoxin, into the DDA or DODAB layers, as a function of time and composition of the cast films. No signal corresponding to the spinach ferredoxin redox reaction is detected at the PG electrode simply coated with a mixed (PC-CH) layer. Well-shaped responses denoting redox reaction of ferredoxin are observed when the (PC-CH) layer is doped with DDA (or DODAB). The results support the electrostatic nature of the interactions between negatively charged species and the positive charges in the lipid layer. Such coated electrodes seem well-suited for studying negatively charged species. They provide a good model for mimicking physiological redox protein-membrane interactions.