研究論文

A direct electrochem. and intramol. electron transfer of multicopper oxidases are of a great importance for the fabrication of these enzyme-based bioelectrochem.-devices. Ascorbate oxidase from Acremonium sp. (ASOM) has been successfully immobilized via a chemisorptive interaction on the L-cysteine self-assembled monolayer modified gold electrode (cys-SAM/AuE). Thermodn. and kinetics of adsorption of ASOM on the cys-SAM/AuE were studied using cyclic voltammetry. A well-defined redox wave centered at 166 ± 3 mV (vs. AgAgClKCl(saturate)) was observed in 5.0 mM phosphate buffer solution (pH 7.0) at the fabricated ASOM electrode, abbreviated as ASOM/cys-SAM/AuE, confirming a direct electrochem., i.e., a direct electron transfer (DET) between ASOM and cys-SAM/AuE. The direct electrochem. of ASOM was further confirmed by taking into account the chem. oxidation of ascorbic acid (AA) by O2 via an intramol. electron transfer in the ASOM as well as the electrocatalytic oxidation of AA at the ASOM/cys-SAM/AuE. Thermodn. and kinetics of the adsorption of ASOM on the cys-SAM/AuE have been elaborated along with its direct electron transfer at the modified electrodes on the basis of its intramol. electron transfer and electrocatalytic activity towards ascorbic acid oxidation and O2 reduction ASOM saturated surface area was obtained as 2.41 × 10-11 mol cm-2 with the apparent adsorption coefficient of 1.63 × 106 L mol-1. The ASOM confined on the cys-SAM/AuE possesses its essential enzymic function.