Direct electrochemistry and electrocatalysis of myoglobin immobilized on L-cysteine self-assembled gold electrode |
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Authors: | Paulo Tércio de F Diógenes Izaura C N Abruña Héctor D |
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Affiliation: | Departamento de Qui?mica Orga?nica e Inorga?nica, Universidade Federal do Ceara?, Cx. Postal 6021, Fortaleza, Ceara?, Brazil 60455-970. |
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Abstract: | 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). |
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