Direct electron transfer of redox proteins on a Nafion-cysteine modified gold electrode

A novel Nafion-cysteine functional membrane was constructed. Rapid and direct electron transfer of horseradish peroxidase, Euphorbia latex amine oxidase, superoxide dismutase and cytochrome c was carried out on the functional membrane modified gold electrode with good stability and repeatability. The immobilized protein modified electrodes showed quasi-reversible electrochemical redox behaviors with formal potentials of 60, 35, 66 and 38 mV (vs. Ag/AgCl) in 20 mM potassium phosphate buffer solution, pH 7.0 at 25 °C. The cathodic transfer coefficients were 0.42, 0.42, 0.45, 0.44 and electron transfer rate constants were evaluated to be 1.2, 1.6, 1.0 and 0.6 s−1.