Molecular mass (MW) markers are 180, 130, 73, 54, 48, 35, 24, 16 and 10 kDa. Left: placenta (lanes 1 and 2); skin (lane 3). Right: human SBCE2 (lane 1), WM35 (lane 2), hamster AbC-1 (lane 3) and mouse S-91 (lane 4) melanomas; placenta (lane 5). The amount of protein loaded on gels was 5 and 1 μg for placenta (lanes 1 and 2, respectively) and 20 μg for the skin samples.