Voltammetry on mercury and carbon electrodes as a tool for studies of metallothionein interactions with metal ions.
Rabbit liver Cd-metallothionein (CdMT) and Cd-complex of synthetically prepared pentapeptide (gamma-Glu-Cys)2-Gly were studied as examples of animal and plant metallothioneins. Using hanging mercury electrode, cathodic stripping voltammetry after adsorptive accumulation of the Cd(II)-SR complex at different potentials, is suitable for estimating changes occurring in metal coordination due to the presence of metal ions such as Zn2+, Cu2+, Hg2+ or excessive Cd2+. Conditions under which similar behaviour can be observed for both CdMT and Cd-pentapeptide complex are specified. On carbon electrodes, detailed study of reduction processes of Cd(II)-SR complexes is prevented by occurrence of a large catalytic current; oxidation processes are more suitable for study at these electrodes. Carbon composite paste electrode (10% SiO2) allows deposition of Cd(II)-SR complex during its reduction, as was demonstrated with Cd-cysteine, CdMT or Cd-pentapeptide complex. After deposition, oxidation peak of the uncomplexed Cd2+ ions and one or two oxidation peaks corresponding to a formation of the RS-Cd(II) complex are observed. Also, similarly as on Hg electrode, it was observed that excessive Cd2+ or Zn2+ ions influence oxidation peaks of the RS-Cd(II) complex formation. Combination of measurements on mercury electrode and composite paste electrode is recommended for studies of metallothionein interactions with metal ions or other metal complexes.
Sestáková
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J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague. sestakov@jh-inst.cas.cz
Mader
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D000818:Animals; D002104:Cadmium / Q000737:chemistry; D002244:Carbon / Q000737:chemistry*; D003545:Cysteine / Q000737:chemistry; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D005973:Glutamine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008099:Liver / Q000737:chemistry; D008628:Mercury / Q000737:chemistry*; D008668:Metallothionein / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D011817:Rabbits; D015032:Zinc / Q000737:chemistry
D007477:Ions; D010455:Peptides; D002104:Cadmium; D005973:Glutamine; D002244:Carbon; D008668:Metallothionein; D008628:Mercury; D015032:Zinc; D003545:Cysteine