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.
Ferrari, R., Lausarot, P., Beringhelli, T., Morazzoni, F. (1984). ON THE PH-DEPENDENCE OF CU(II) BINDING TO INSULIN - ELECTRON-SPIN-RESONANCE AND ELECTRONIC STUDIES. POLYHEDRON, 3(7), 833-838 [10.1016/S0277-5387(00)84631-8].
ON THE PH-DEPENDENCE OF CU(II) BINDING TO INSULIN - ELECTRON-SPIN-RESONANCE AND ELECTRONIC STUDIES
MORAZZONI, FRANCA
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.