A new insight into mercurized hemoglobin aggregation mechanism.

Coagulation of bovine oxyhemoglobin in the presence of mercuric acetate in concentrations within a range including concentrations exceeding those required to block the single pair of thiol groups of the protein has been investigated in Tris-acetate buffer. The values of initial coagulation rate plotted against mercury-to-hemoglobin molar ratio give curves exhibiting a clear break points at ratios corresponding to full blocking of the mentioned thiol groups. Larger amounts of mercury reagents producing enhanced protein coagulation effect depend approximately quadratically on the mercury concentration. Interaction of the excess mercuric ions with some mercury-binding sites located on or near the dimer-dimer contact surfaces of the protein producing stronger coagulation effect is suggested.