Application of multivariate curve resolution to voltammetric data. II. Study of metal-binding properties of the peptides.
The complexation of Cd2+ by glutathione (GSH), in 0.13 m borate buffer at pH 9.5, was studied by differential pulse polarography (DPP) and multivariate curve resolution. The Cd-GSH system has been chosen as a model to check the possibilities of this new polarographic approach to the study of metal ion complexation by peptides. Experimental data obtained by DPP for different Cd2+-to-GSH concentration ratios have been analyzed by a procedure which consists of using several chemometrical techniques based on factor analysis: principal component analysis, evolving factor analysis, and multivariate curve resolution with alternating least-squares (ALS) optimization. The use of different constraints during the ALS optimization process, such as nonnegativity and unimodality constraints, yields the optimal sought solution from a chemical point of view. In the present work, a new constraint has been implemented during ALS optimization to take into account the expected peak-shaped signal of DPP. This data treatment allows us to detect simultaneously the formation of 1:1 and 1:2 Cd:GSH complexes which were very difficult to detect by univariate analysis of DPP data. It is concluded that the described multivariate curve resolution method could be a reliable tool for studying metal-binding properties of peptides.
Mendieta
J
J
Departament de Química Analítica, Facultat de Química, Universitat de Barcelona, Av. Diagonal 647, Barcelona, 08028, Spain.
Díaz-Cruz
M S
MS
Tauler
R
R
Esteban
M
M
D002104:Cadmium / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D016018:Least-Squares Analysis; D015999:Multivariate Analysis; D011048:Polarography / Q000379:methods*
D002104:Cadmium; D005978:Glutathione