The Chemical Composition of Wool XI. Separation and Analysis of Exocuticle and Endocuticle

Abstract

Whole cuticle is separated from wool by treatment in formic acid. Digestion of cuticle with pronase is complete after 36% by weight of cuticle is dissolved and the residue is shown by electron microscopy to be exocuticle, with no evidence of adhering endocuticle. The digested protein corresponds to endocuticle and the residue to exocuticle. The endocuticle contains only 3 residues per 100 of !cystine and is generally similar in amino acid analysis to the non-keratinous material from the cortex (Peters and Bradbury 1972).