Strategies for the qualitative and quantitative analysis of metallothionein isoforms by capillary electrophoresis

Metallothioneins (MT) are a heterogeneous family of proteins coded from multiple linked genes whose individual expression can be readily determined at the transcriptional level by assay of mRNA using specific DNA probes targeted against the untranslated regions. Analysis of translated protein products is more challenging since sequence variation between MT isoforms can be as little as one in 61 amino acids. Separation of these isoforms therefore requires a high resolution technique which can exploit minor differences in charge or hydrophobicity. The use of capillary electrophoresis (CE) for MT isoform separation is reviewed, including practical information on capillaries and electrolyte conditions which are most suitable for qualitative evaluation of purified MT and also for quantification of isoforms from biological tissues. Methods of sample preparation are discussed, as are methods of characterising the separated components and enhancing sensitivity of their detection.