Study of Cd2+ complexation by the glutathione fragments Cys–Gly (CG) and γ-Glu–Cys (γ-EC) by differential pulse polarography

Abstract

A differential pulse polarographic study of the Cd²⁺/γ-Glu–Cys and Cd²⁺/Cys–Gly systems assisted by the alternating least-squares multivariate curve resolution (MCR-ALS) method was carried out to obtain a better understanding of the different metal affinities of the complexation sites on glutathione (GSH). The simultaneous analysis of the titration of peptide with metal and of metal with peptide allowed the resolution of the Cd²⁺/Cys–Gly system, whereas in the analysis of the Cd²⁺/γ-Glu–Cys system the analysis of a single titration experiment was sufficient. The analysis of the shape of the resulting pure voltammograms and concentration profiles of the resolved components suggested the presence of two different types of bound Cd²⁺ in the two systems considered, that could be attributed to Cd²⁺ bound to one or two sulfur atoms to form complexes of stoichiometry 1∶1 and 1∶2, respectively.