Reaction of Cystine Residues in Wool with Peroxy Compounds

Abstract

Wool was oxidized under aqueous acidic conditions with Caro's salt, and the oxi dation products of cystine were measured using Fourier transform infrared spectroscopy coupled with the attenuated total internal reflectance sampling technique. The reso lution of the infrared bands in the wool spectrum was improved by differentiation to the second-order derivative. Following differentiation, individual sulphur-oxygen bands in the infrared spectrum of wool were resolved and identified. The intensity of the cysteic acid band was proportional to cysteic acid concentration, and following such oxidation treatments of the wool substrate, cysteic acid was the main oxidation product formed from cystine. The overall effect of applying Caro's salt to wool was determined by high performance liquid chromatography. The amino acids were labeled with the fluorescent tag, 9-fluorenylmethyl-chloroformate, separated on a C-18 column, and detected at 340 nm. The results show that permonosulphuric acid treatments convert cystine to cysteic acid and methionine to methionine sulphoxide and reduce the con centration of tyrosine in wool.