CYCLIC VOLTAMMETRIC BEHAVIOR OF [2FE-2S] FERREDOXINS AT A LIPID BILAYER MODIFIED ELECTRODE

Direct electron transfer between ferredoxins isolated from vegetative cells of the cyanobacterium Anabaena (strain 7120) and from spinach, and a gold electrode modified with a self-assembled lipid bilayer membrane, has been investigated at various ionic strengths by cyclic voltammetry. The lipid bilayers were comprised of the electrically neutral egg phosphatidylcholine (PC), either alone or in combination with varying amounts of the positively charged surfactant dimethyldioctadecylammonium chloride (DODAC+). Both ferredoxins were found to interact strongly enough with the lipid membrane to support an efficient electron transfer reaction with the electrode. The interaction forces could be controlled by the PC concentration, the DODAC+ concentration, and the ionic strength of the supporting electrolyte. The observations suggest a mechanism involving attractive electrostatic interactions between the redox protein molecules and the lipid bilayer, which lead to rapid and discriminatory electron transfer with the gold electrode.