The reaction of oxidizing agents with wool. 5. The oxidation products of the disulphide bond and the formation of a sulphonamide in the peptide chain

Abstract

Oxidation of wool with solns. of KMnO4 at pH 9.2 and Na hypochlorite at pH 10 led to the formation of lanthionine in the cold from the reactive cystine fraction (approx. 30% of the total cystine). Acidic solns. of KMnO4, which also react with only 30% of the total cystine, gave cysteic acid and sulfate. On oxidation with acid solns. of Cl and peracetic acid, which are capable of reacting with all the cystine, combined cysteic acid was not produced directly within the fiber although cysteic acid was produced almost quantitatively on acid hydrolysis. To explain this and other observations the formation of a combined heterocyclic mixed imide of a carboxylic and sulfonic acid, respectively, within the wool is postulated. In order to interpret results obtained by treatment of wool oxidized with peracetic acid or Cl at pH 2 with dilute alkali it is postulated that alkali hydrolyzes this sulfo-carboxylic imide across the CO-N bond to give a sulfonamide within the fibers. The formation of the sulfonamide explains the increase in acidity on alkali extraction. Hydrolysis of the postulated sulfonamides by drastic treatment with HC1 led to the production of cysteic acid together with all the amino acids of wool. This shows cystine is combined with all the various amino acids within the fiber. Evidence for the limited formation of a partially oxidized product formed from cystine by a side reaction was obtained. As this reverts to cystine, at least partially, on treatment with alkali, it is suggested that this intermediate may be a sulfoxide.