Improved procedure for crystallization of Clostridium botulinum type A toxic complexes.

A modified protocol for the preparation of botulinum type A toxic crystals is decribed. The essential change was the substitution of chromatography on diethylaminoethyl-Sephadex for the step in which toxin was precipitated with ethanol. Colored materials and nucleic acids were removed by the chromatography so that crystal lots of greater uniformity could be produced. Significantly more of toxin in the starting culture was recovered as crystals. The lots of crystals obtained initially by either the original or the modified method contained an antigen that was eliminated when the lots were recrystallized.