Scanning Electron Microscopy of Freeze-dried Protein Foams

Two proteins of low molecular weight, which bind cadmium and are rich in cysteine were isolated from kidneys of the striped dolphin, Stenella coeruleoalba, and identified as metallo-thioneins I and II. The two isoforms closely resembled horse renal isometallothioneins both in chromatographic behaviors and chemical compositions. The molecular weights of performic acid-oxidized proteins were estimated to be 6,800. Twenty to 21 cysteine residues and about 6 g-atoms of heavy metals (Zn, Cd, Cu, and Hg) were present per mole of each isomer.