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.
|Titolo:||On the pH dependence of Cu(II) binding to insulin: ESR and electronic studies|
BERINGHELLI, TIZIANA (Penultimo)
|Settore Scientifico Disciplinare:||Settore CHIM/03 - Chimica Generale e Inorganica|
|Data di pubblicazione:||1984|
|Digital Object Identifier (DOI):||10.1016/S0277-5387(00)84631-8|
|Appare nelle tipologie:||01 - Articolo su periodico|