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Abstract
Electrofocusing resolved six distinct haemolytic components in crude ammonium sulphate-precipitated staphylococcal a-toxin. Four of these had the properties of staphylococcal a-toxin as judged by several criteria and were designated aA (pI = 8·55±0·12); aB (pI = 9·15±0·07); aC (pI = 7·36±0·03); aD (pI = 6·28±0·11); 85·95 per cent. of the recovered activity was found as the aA component. Reversible interconversion of aA and aB was demonstrated and these forms showed similar patterns in disk-gel electrophoresis; each showed a main band having a molecular weight of 36,000 and a second band having a molecular weight of 170,000. In the presence of 6M urea aA yielded a single haemolytic component having a pI of 8·50, and electrophoresis of aA and aB in urea revealed a single main band.
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