A first model for the oxidized active form of the active site in galactose oxidase: a free-radical copper complex |
| |
Authors: | Dacil Zurita Isabelle Gautier-Luneau Stéphane Ménage J-L Pierre Eric Saint-Aman |
| |
Institution: | (1) Laboratoire d'Etudes Dynamiques et Structurales de la Sélectivité (UMR CNRS 5616), Université J. Fourier, BP 53, F-38041 Grenoble Cedex 9, France Fax: +33-76 51-48 36; e-mail: Jean-Louis.Pierre@ujf-grenoble.fr, FR;(2) Laboratoire d'Electrochimie Organique et de Photochimie Redox (UMR CNRS 5630), Université J. Fourier, BP 53, F-38041 Grenoble Cedex 9, France, FR |
| |
Abstract: | Copper(II) complexes derived from the tripodal ligand bis(3′-t–butyl-2′-hydroxybenzyl)(2-pyridylmethyl)amine (LH2) have been studied in order to mimic the redox active site of the free radical-containing copper metalloenzyme galactose
oxidase. In non-coordinating solvents such as dichloromethane, only an EPR-silent dimeric complex was obtained (L2Cu2). The crystal structure of L2Cu2 revealed a "butterfly" design of the Cu(μOR)2Cu] unit, which is not flattened and leads to a short Cu–Cu distance, the t–butyl groups being localized on the same side of the Cu(μOR)2Cu] unit. The dimeric structure was broken down by acetonitrile or by alcohols, leading quantitatively to a brown mononuclear
copper(II) complex. UV-visible and EPR data indicated the coordination of the solvent in these mononuclear complexes. Electrochemical
as well as chemical (silver acetate) one-electron oxidation of acetonitrile solutions of the monomeric complex led to a yellow-green
solution. Based on EPR, UV-visible and resonance Raman spectroscopy, the one-electron oxidation product was identified as
a cupric phenoxyl radical system. It slowly decomposes into a product where the ligand has been substituted (dimerization)
in the para position of the hydroxyl group, for one of the phenolic groups. The data for the one-electron oxidized species provides strong
evidence for a free-radical copper (II) complex.
Received: 19 July 1996 / Accepted: 16 October 1996 |
| |
Keywords: | Galactose oxidase Biomimetic model Copper Free radical |
本文献已被 SpringerLink 等数据库收录! |
|