Solution chemical properties and catecholase-like activity of the copper(II)-Ac-His-His-Gly-His-OH system, a relevant functional model for copper containing oxidases

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Abstract

The solution chemical properties, Superoxide dismutase and catecholase activity of the copper(II)-Ac-His-HisGly-His-OH (hhgh) complexes were studied to identify functional and structural models of copper-containing oxidases. The solution speciation was determined in the pH range 3-11 by two independent methods (potentiometry and pH-dependent EPR measurements). The results obtained by the two methods agree very well with each other and show the formation of differently protonated CuHxL complexes (where x = 2,1, 0, -1, -2, -3) in aqueous solution. The spectroscopic (UV-Vis, CD, EPR) data indicate that the coordination of the imidazole rings is a determinant factor in all these complexes. Amide coordinated complexes are dominant only above pH 8. This offers excellent possibilities for structural/functional modelling of copper(II) containing metalloenzymes. Indeed, the {3Nim} coordinated CuL species (pH = 6-7) has efficient Superoxide dismutase-like activity. The {3N im,OH-} coordinated CuH-1 L possesses outstanding activity to catalyze the oxidation of 3,5-di-tert-butylcatechol (H2dtbc) by dioxygen in 86 wt% methanol-water, providing the first example that copper(II)-peptide complexes are able to mimic copper containing oxidases.

Original languageEnglish
Pages (from-to)3187-3194
Number of pages8
JournalDalton Transactions
Issue number19
DOIs
Publication statusPublished - Oct 7 2005

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ASJC Scopus subject areas

  • Inorganic Chemistry

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