Cadmium binding in mixtures of phytochelatins and their fragments: A voltammetric study assisted by MCR and ESI-MS

Analyst, 2010, 135, 86 - 95, DOI: 10.1039/b918293d
Rui Gusmão, Cristina Ariño, José Manuel Díaz-Cruz and Miquel Esteban

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Phytochelatins (PC_n, (-Glu-Cys)_nGly) are cysteine-rich peptides synthesized by plants which are involved in metal bioregulation and phytoremediation. Multivariate Curve Resolution by Alternating Least Squares (MCR-ALS) is applied to voltammetric data obtained from the analysis of the competitive binding of Cys or Cys-Gly with PC₂ or PC₃ by Cd²⁺. The displacements between ligands, the chain length dependence on the competitive binding to PC_n and the possible existence of mixed ligand metal-complexes are investigated. The shape analysis of the resulting pure voltammograms and concentration profiles of the components resolved by MCR-ALS suggests that ligands containing more thiol groups are able to displace the shorter chain ligands from their metal complexes, whereas the opposite does not happen. Electrochemical results are compared with ESI-MS measurements.