Direct electron transfer enhancement of covalently bound tyrosinase to glassy carbon via Woodward's reagent K.

Hassan Faridnouri, Hedayatollah Ghourchian, Seddigheh Hashemnia

Institute of Biochemistry and Biophysics, University of Tehran, Iran. faridnouri@ibb.ut.ac.ir

Bioelectrochemistry (Amsterdam, Netherlands) 2011 Aug

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This work describes the reaction mechanism for chemical modification of tyrosinase by Woodward's Reagent K and its covalent attachment to a glassy carbon electrode. The spectrophotometric studies revealed that the modification does not cause a significant structural change to tyrosinase. The direct electrochemistry of modified enzyme was achieved after immobilization on an oxidatively activated glassy carbon electrode. The enzyme film exhibited a pair of well-defined quasi-revesible voltammetric peaks corresponding to the Cu (II)/Cu (I) redox couple located in the active site of tyrosinase. The formal potential of immobilized enzyme was measured to be 90mV (vs. Ag/AgCl) in phosphate buffer solution at pH 7.0. The charge-transfer coefficient and apparent heterogeneous electron transfer rate constant were estimated to be 0.5 and 0.9±0.06s(-1), respectively. Finally, the electrochemical behavior of the immobilized enzyme in the presence of caffeic acid and L-3,4-dihydroxyphenylalanine as substrates was investigated. The amperometric study of biosensor toward L-3,4-dihydroxyphenylalanine resulted a linear response in the concentration range from 1.66×10(-6) to 8.5×10(-5)M with detection limit of 9.0×10(-5)M and sensitivity of 135mAμM(-1)cm(-2). Copyright © 2011 Elsevier B.V. All rights reserved.

Citation

Hassan Faridnouri, Hedayatollah Ghourchian, Seddigheh Hashemnia. Direct electron transfer enhancement of covalently bound tyrosinase to glassy carbon via Woodward's reagent K. Bioelectrochemistry (Amsterdam, Netherlands). 2011 Aug;82(1):1-9