Advantages and disadvantages of voltammetric method in studying cadmium-metallothionein interactions.

A sensitive and chemical species-selective technique of differential pulse anodic stripping voltammetry (DPASV) was applied in studying the cadmium-metallothionein (Cd-MT) interaction. The amperometric titrations of the purified MT20 and MT10 fractions, isolated by verified biochemical procedures from the digestive gland of cadmium-exposed mussels Mytilus galloprovincialis, with Cd2+ ions were performed in the buffered sodium chloride solution of 0.59 M ionic strength, pH 7.9 and 25 degrees C. Applying the DPASV method at various cadmium to metallothionein ratio several groups of chemical species were recorded. The data on the available ligand concentration to complex cadmium ions (CL), the apparent concentration stability constants (K,) of the respective complexes and the reliability of the determined complexing parameters are discussed. In quantifying the Cd-MT interaction the interference of dithiotreitol (DTT), which is used as the reducing agent in isolation and purification of MTs, is documented.