The interaction of α-haemolysin with sheep erythrocytes was characterised in all experiments by a lag phase, and by a period of lysis that was linear between 20 and 80% haemolysis. The lag phase was inversely proportional to the logarithm of haemolysin concentration. Maximum rates of haemolysis were observed at 43°C and 8.8 to 9.0.

The optimal concentration of CaCl for haemolysis was between 1 m and 10 m. Evidence is presented that the first step in the haemolytic reaction is activation of α-haemolysin by calcium ions. This causes an alteration in the structural appearance of purified haemolysin molecules. It was also shown that EDTA inhibited haemolysis only when added to α-haemolysin before its activation by calcium ions. This finding suggests that, during activation, calcium ions are firmly bound to α-haemolysin.


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