Molecular mass determination of Terebralia hemocyanin by SDS-PAGE. (a) Apparent molecular mass of both intact subunit types (blue triangles), and of the larger tryptic fragment (red triangle) obtained from the larger subunit. As molecular mass markers we used KLH1 (400 kDa ), Nautilus pompilius hemocyanin (335 kDa ), Rapana thomasiana hemocyanin (400 kDa and 280 kDa natural fragment ), and myosin (205 kDa, standard marker). Note that the 540 kDa value is obtained by graphical extrapolation. (b) Apparent molecular mass of the smaller tryptic fragment (red triangle) obtained from the larger subunit; a standard mixture of molecular mass markers (myosin, β-galactosidase, phosphorylase A, bovine serum albumin) was applied. Note that the two fragments summate to 550 kDa.