The surface analysis technique of x-ray photoelectron spectroscopy (XPS) has been used to investigate the chemical composition and reactivity of the wool epicuticle. Approximate relative proportions of protein and lipid material in the epicuticle have been deduced from the surface elemental ratios; the sulfur content of the proteins in the epicuticle was estimated to be about 9% by weight. Treating wool with potassium t-butoxide in anhydrous t-butanol, a reagent that is reported to cause specific epicuticle modification, caused only minor changes in the elemental composition of the fiber surface. There were marked changes, however, in the sulfur (2p) photoelectron spec trum. Approximately one third of the cystine residues in the epicuticle were converted to cysteic acid residues. Evidence was also obtained for the partial conversion of cystine residues into lanthionine residues.
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