Chemical Investigation of the Sulfur-Containing Amino Acids and Sulfur Content of Persulfate-Oxidized Wool

Abstract

The sulfur content and the sulfur-containing amino acids in wool are greatly affected by oxidation with persulfate. The sulfur content apparently increased due to uptake of sulfate radicals by the wool as a result of the persulfate treatment. This could be reversed by a bicarbonate treatment, and the real trend is a decrease of sulfur with increasing the oxygen consumption. Cystine decreased rapidly in the early stages; with further treatment, no further loss in cystine can be detected. Methionine and its oxidation products could not be detected in the oxidized wool, while lanthionine is only found as traces in the persulfate- treated wool at alkaline pH values. Infrared spectroscopy, carried out to detect other oxidation products without hydrolysis of the wool, gave bands due to sulfoxide, sulfinic, and sulfonic acid groups in the persulfate-oxidized wool. Cysteic acid was found in the hydrolyzate of the persulfate-oxidized wool and could be estimated ionophoretically. Cysteic acid content increased with the degree of oxidation and was found to attain a limiting value of 7.5% at an oxygen consumption of more than 4.30.