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On the pH dependence of Cu(II) binding to insulin: ESR and electronic studies

By R.P. Ferrari, P. Michelin Lausarot, T. Beringhelli and F. Morazzoni

Abstract

The ESR and electronic absorption spectra have been used to investigate co-ordination of Cu(II) to insulin in aqueous solutions at different pH. Two series of complexes with low- and high copper content were examined and the values of the magnetic tensor components and the shape of the diffuse reflectance transitions suggested that these copper-insulin derivatives have tetragonal symmetry with Cu(II) in a (NxOy) ligand field, where oxygen donor groups are predominant at low pH and nitrogenous ligands at high pH. Such a trend was further supported by the presence of superhyperfine structure at pH = 13. Oxygen of the carboxylato groups, nitrogen of α- and ε-amino groups and of imidazoles, all contribute to the coordinations field. At very high pH only, a preferential binding site for Cu(II) is found, which probably involves deprotonated peptide nitrogens. © 1984

Topics: Settore CHIM/03 - Chimica Generale e Inorganica
Publisher: 'Elsevier BV'
Year: 1984
DOI identifier: 10.1016/S0277-5387(00)84631-8
OAI identifier: oai:air.unimi.it:2434/188113
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