Direct electron transfer in immobilized flavoenzyme chemically modified graphite electrodes

Direct electron transfer between covalently immobilized flavoenzymes and a cyanuric chloride-modified graphite electrode is observed via differential pulse voltammetry. L-Amino acid oxidase and xanthine oxidase display peaks arising from the reduction of flavin adenine dinucleotide. Peak current enhancements are observed for both covalently attached enzymes compared to their free and adsorbed state voltammograms. Studies concerning flavin removal and reconstitution indicate that xanthine oxidase contains multiple flavin chromophores which are nonequivalent.