The stability and solubility of diphtheria toxin in acid and alkili / Una Wallace.

  • Wallace, U.
Date:
[1927?]
Catalogue details

Licence: In copyright

Credit: The stability and solubility of diphtheria toxin in acid and alkili / Una Wallace. Source: Wellcome Collection.

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    sprinted from The Journal of Pathology and Bacteriology, Vol. XXX., 1927 THE STABILITY AND SOLUBILITY OF DIPH¬ THERIA TOXIN IN ACID AND ALKALI. Una Wallace. Wellcome Physiological Research Laboratories, Beckenham, Kent. Fhere are observations from 1890 onwards that diphtheria toxin when icidified loses its toxicity, which is partially recovered on reneutralisa- iion (Doerr 1908). The fact that this loss is due to precipitation vas overlooked until Glenny and Walpole (1915) made it the basis >f a method for purifying toxin. Alkali has on the whole been found iestructive and its effect irreversible. Walbum (1922) showed that between pH 9'5 and 10*5 destruction was complete after 6 days at 37° 0. The aim of the present experiments was to determine the stability, as distinct from the precipitation, of toxin with acid and ilkali in terms of pH, and incidentally the frequent incompleteness of precipitation with acid alone led to the trial of other precipitants. Already in 1890 Erankel and Brieger had found that precipitation j)f toxin with alcohol was most complete if the alcohol was slightly acidified with acetic acid. This precipitant is most effective at that jH where the solubility of the toxic material is already at a minimum; and, since it is not completely insoluble at the isoelectric point, an additional precipitant is needed. Alum was chosen for the following experiments as it had already been shown to give highly antigenic precipitates (Glenny, Pope, Waddington and Wallace 1926). Ammonium sulphate was used by Brieger and Boer in 1896, but the toxicity of ammonium salts is a disadvantage in the purification of diphtheria toxin for immunising purposes. All such methods have one disadvantage; the precipitation of the ;Oxin depends upon, or is inseparable from, the precipitation of other material already present in the culture filtrate. It has been shown that this acid precipitable material is often present in the original medium, that it increases during the growth of G. diphtherias and that its increase bears no relation to the strength of toxin obtained (Watson and Wallace 1924a). Consequently both the purification (toxin units per mgrm. of total weight) and the yield of toxin obtain¬ able by precipitation is liable to vary for different toxins. Adsorption on to some material not naturally present in the culture media, or formed during growth, would give a less variable method of purification.