Study of metallothionein using capillary zone electrophoresis.

Metallothioneins (MTs) have many different functions in tissues, but the roles of individual isoforms are still not entirely clear. Capillary zone electrophoresis (CZE) is a powerful method for the separation of substances because of its small sample requirement, rapid analysis, high sensitivity and high resolution. The separation and identification of mammalian MT-1, MT-2, and MT-3 and class III MTs by CZE has been reported. Uncoated and polyacrylamide-coated capillary tubes were recently used for the separation of MTs, and a UV detector is usually employed for observations of peaks of MTs. Small changes to the structure and metal components of MTs are reflected in the migration times of the peaks. N-acetylated and non-acetylated MTs can be separated and identified by CZE-mass spectrometry (MS). In addition, metal complexes with MTs can be characterized by CZE-proton-induced X-ray emission (PIXE) detector and CZE-inductively coupled plasma (ICP)-MS. For the quantification of an MT isoform, the peak area of UV absorption is used, but the technique has problems. One is lack of a purified isoform standard. The other is the need for a suitable internal standard substance. CZE-ICP-isotope dilution (ID)-MS is also reported to be able to quantify MT isoforms. CZE combined with other techniques is very effective for separation and quantitative and qualitative analyses of MT isoforms in biological materials.