Formation of Copper(II)-Wool Keratin Complexes

Abstract

The effect of the binding of Cu(II) ions on the dissociation of the side chain carboxyl groups in wool keratin has been measured using a modified Bjerrum's method. Data taken at various ionic strengths indicate that in the presence of much NaNO3, the formation curves fall on the same curve regardless of Cu(II) ion concentration, and the stability constants b1 and b2 decrease with increasing NaNO3 concentration. This phenomenon might be due to the fact that complexing reactions become increasingly difficult because of the screening effect of NaNO3. The variation of the value of b2 was more significant than that of b1, confirming that the increase of the ratio of the concentrations of Cu(II) to glutamyl and aspartyl residues ( TCu/ THL) and of the NaNO3 concentration resulted in an increase in the fraction of CuL2 species.