Study of Cd complexes in Cd, Zn, metallothioneins by differential pulse polarography
Metallothioneines are proteins of low molecular weight, characterised by high cysteine residue content (approx. 30 %) and absence of aromatic amino acids and by their selective ability to bind heavy metals such as Zn, Cd, Hg and Cu. By use of differential pulse polarography (DPP) several distant chemical forms of the species dervied from these compounds can be identified and their formation traced as a function of the experimental parameters. At pH greater than 6 the polarographic response shows three peaks: MT, Cd-T and Zn-T. The MT peak results from oxidation of electrode Hg in the presence of the protein's thiolic groups. The Cd-T and Zn-T peaks result from reduction of metal cations Cd and Zn bound to the thioneine. Within the range of potentials corresponding to the reduction of Cd bound to the tioneine, either one or two peaks can be distinguished, depending on the experimental conditions. These arise from two distinct Cd-thioneine complexes. The equilibrium between these complexes can be modified by varying the different parameters so that one or other of them predominates.
Bibliographic Reference: Paper presented: Jornadas Analitis Instrumental, Madrid (ES), April 3-6, 1995
Availability: Available from (1) as Paper ES 39135 ORA
Record Number: 199511292 / Last updated on: 1996-08-30
Original language: es
Available languages: es