Comparison between isolation protocols commonly used for the purification of mollusc metallothioneins

Two centrifugation methods (at 30 000 and 100 000 g) combined with two isolation procedures (heat denaturation and solvent precipitation) were tested to check if their use introduced significant differences in the quantification of metals (Cd, Cu, Zn) and metallothioneins in blue mussel organs (gills and digestive gland). No contaminating compounds originating from the lowest centrifugation speed were likely to interfere with quantitative measurements of metal, protein and metallothionein. As isolation treatments act on specific properties of proteins in general and metallothionein isoforms in particular they cannot be used interchangeably. Therefore, any comparisons of MT amounts in bivalve tissues with data from the literature have to take into account the isolation procedure. Similar results were obtained with three other molluscs, Crassostrea gigas, Bathymodiolus thermophilus (hydrothermal mussel), and Corbicula fluminea (estuarine bivalve).