title: Electrochemically mediated reduction of horseradish peroxidase by 1,1'-ferrocenedimethanol in organic solvents.
abstract: Cyclic voltammetry is an efficient means of analyzing the catalytic reduction of H2O2 at immobilized horseradish peroxidase (HRP)-Eastman AQ 55 electrodes in the presence of 1,1'-ferrocenedimethanol as a one-electron reversible cosubstrate. This system was employed to study the kinetics of the reduction of compound II of HRP in a number of organic solvents. An electrocatalytic response was detected in methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, 2-butanone, 1,2-propanediol, acetonitrile, ethyl acetate, and ethylene glycol. Unusual bell-shaped variations of the peak or plateau catalytic current with the substrate concentration were observed in all solvents tested. The results obtained in methanol, acetonitrile, and 1-propanol were analyzed using the model developed by Saveant (Limoges, B.; Saveant, J.-M.; Yazidi, D. J. Am. Chem. Soc. 2003, 125, 9192-9203). The values of k3Gamma0 and K3,M, where k3 = k3,1k3,2/(k3,-1 + k3,2), Gamma0 is the surface concentration of active enzyme, and K3,M = (k3,-1 + k3,2)/k3,1, were determined. The values of k3Gamma0 for the mediated reduction of compound II of HRP in methanol, 1-propanol, and acetonitrile (in the presence of 5% aqueous buffer) were not affected by the solvent dielectric constant but decreased with solvent hydrophobicity. The value of K3,M obtained in methanol was similar to that obtained for [Os(bpy)2pyCl]2+ in aqueous buffer.
authors.affiliation: Department of Chemical and Environmental Sciences and Materials and Surface Science Institute, University of Limerick, Castletroy, Limerick, Ireland.
authors.forename: Anastassija
authors.initials: A
authors.lastname: Konash
authors.forename: Edmond
authors.initials: E
authors.lastname: Magner
mesh_terms: D000433:1-Propanol; D000097:Acetonitriles; D004563:Electrochemistry; D004800:Enzymes, Immobilized; D006735:Horseradish Peroxidase / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D000432:Methanol; D010084:Oxidation-Reduction
chemical_list: D000097:Acetonitriles; D004800:Enzymes, Immobilized; D000433:1-Propanol; D006735:Horseradish Peroxidase; D000432:Methanol; C032159:acetonitrile