Stabilization of whole molecules of gastropodan haemocyanins by chlorhexidine

Chlorhexidine diacetate 0.01% stabilized the whole molecules of Helix pomatia alpha-haemocyanin under dissociating conditions; in 1 M NaCl and in 1.42 M sucrose. Dissociation at low ionic strength (10 mM) of the haemocyanin of Pila leopoldvillensis was likewise prevented by chlorhexidine. After dissociation into half molecules of H. pomatia alpha-haemocyanin in 1.42 M sucrose and of P. leopoldvillensis haemocyanin by lowering the ionic strength, whole molecules were formed on introduction by dialysis of chlorhexidine diacetate to a concentration of 0.01%. This stabilization points to the binding of the two chlorophenyl groups in hydrophobic regions of the protein and an ensuing cross-linking of the half molecules of gastropodan haemocyanins. Chlorguanide, which almost corresponds to one half chlorhexidine, even at a concentration of 0.1%, only slightly stabilized the whole molecules.