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.

On the pH dependence of Cu(II) binding to insulin: ESR and electronic studies / R.P. Ferrari, P. Michelin Lausarot, T. Beringhelli, F. Morazzoni. - In: POLYHEDRON. - ISSN 0277-5387. - 3:7(1984), pp. 833-838.

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

T. Beringhelli
Penultimo
;
1984

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.
Settore CHIM/03 - Chimica Generale e Inorganica
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/188113
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