Alternating Current Voltammetry Studies of the Effect of Melittin on Heterogeneous Electron Transfer across a Hybrid Bilayer Membrane Supported on a Gold Electrode

Hybrid bilayer membranes (HBM) that consist of two different layers (a self-assembled monolayer of alkanethiols on a gold electrode and a second layer of phospholipids) dramatically attenuate the heterogeneous electron transfer between soluble redox couples and the gold electrode. Alternating current voltammetry indicates the presence of a low density of defects in the HBM through which the redox couples can reach the electrode. Adsorption of a pore-forming cationic peptide, melittin, into the HBM increases the HBM capacitance, accelerates the faradic reaction for the negatively charged redox couple Fe(CN) 6 3 -, decelerates the faradic reaction for the positively charged redox couple Ru(NH 3 ) 6 3+, and has little effect on the faradic reaction of the neutral hydroxymethylferrocene. These results are discussed in terms of several possible mechanisms, including pore-forming processes and electrostatic effects.