The Amino Acid Analysis of Cuticle-Rich Material from Wool

Abstract

Cuticle material of various degrees of purity was obtained in yields ranging from 0.2% to 7.2% of the weight of the fiber by using descalers of different sharpness. Microscopic examination of the cuticle-rich material and the residual fibers abraded aiong one side showed that the material becomes richer in cuticle as the yield decreases. The material collected in 0.5-0.7% yield consists of about 50% cuticle and for the three saniples of wool contains on the average 27% more proline and 40% less aspartic acid plus glutamic acid than the parent fibers. In one sample the cuticle-rich material is richer in glycine (39%) and in another richer in cystine (22%) than the parent fibers. The high proline content of the cuticle is consistent with its amorphous nature and the dearth of free carboxyl groups, interesting because of Lindberg's suggestion that the barrier to diffusion of dyes into the fiber is electrical in nature. However, other evidence indicates that the barrier is most probahly the epicuticle, which constitutes < 2% of the material analyzed.