Cadmium binding properties of the C-terminal hexapeptide from mouse metallothionein:: study by linear sweep voltammetry and multivariate curve resolution analysis

The complexation of cadmium by the C-terminal hexapeptide of mouse metallothionein I, Lys-Cys-Thr-Cys-Cys-Ala (FT), was studied by linear sweep voltammetry (LSV). Experimental data obtained at different Cd-to-FT concentration ratios, in 0.1 mol l(-1) phosphate-HEPES medium at pH 8.0, were analysed by means of several chemometrical techniques based on factor analysis: principal component analysis, evolving factor analysis and multivariate curve resolution (MCR) with alternating least-squares (ALS) optimization. The use of different constraints in the ALS optimization, such as nonnegativity and specially a new LSV-peak-shape constraint, allows one to obtain (i) individual voltammograms corresponding to the unitary signals of the different electrochemical processes involved, and (ii) the corresponding concentration profiles. This level of information cannot be reached by means of classical univariate analysis. Thus the calculated concentration profiles for the different unitary signals suggest the progressive complexation of three Cd2+ by FT. From the results obtained at various Cd-to-FT concentration ratios, where different unitary signals appear, the successive formation of different Cd complexes is deduced. (C) 1999 Elsevier Science S.A. All rights reserved.