Direct electrochemistry and electrocatalysis of myoglobin immobilized on L-cysteine self-assembled gold electrode.
Myoglobin (Mb) has been successfully immobilized on a self-assembled monolayer (SAM) of L-cysteine (Cys) on a gold electrode, Au/Cys. The presence of a pair of well-defined and nearly reversible waves centered at ca. 0.086 V vs Ag/AgCl (pH 6.5) suggests that the native character of Mb heme Fe(III/II) redox couple has been obtained. The formal potential of Mb on Cys SAM exhibited pH-dependent variation in the pH range of 5-9 with a slope of 55 mV/pH, indicating that the electron transfer is accompanied by a single proton exchange. Thermodynamic and kinetic aspects of Mb adsorption processes on Au/Cys were studied by using voltammetric and quartz-crystal microbalance methods. The Au/Cys electrode with immobilized Mb exhibited electrocatalytic activity toward ascorbic acid (AA) oxidation with an overpotential decrease of over 400 mV and a linear dependence of current on the AA concentration from 0.5 to 5.0 mmol L(-1).
Departamento de Química Orgânica e Inorgânica, Universidade Federal do Ceará, Cx. Postal 6021, Fortaleza, Ceará, Brazil 60455-970.
Tércio de F
Tde F
Paulo
Izaura C N
IC
Diógenes
Héctor D
HD
Abruña
D000327:Adsorption; D000818:Animals; D001205:Ascorbic Acid / Q000737:chemistry; D002384:Catalysis; D003545:Cysteine / Q000737:chemistry*; D004563:Electrochemistry; D004566:Electrodes; D004579:Electron Transport; D006046:Gold / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D055767:Immobilized Proteins / Q000737:chemistry*; D007700:Kinetics; D009211:Myoglobin / Q000737:chemistry*; D009994:Osmolar Concentration; D058525:Quartz Crystal Microbalance Techniques; D013816:Thermodynamics
D055767:Immobilized Proteins; D009211:Myoglobin; D006046:Gold; D003545:Cysteine; D001205:Ascorbic Acid