The Chemical Composition of Wool V. The Epicuticle

Abstract

The cuticle membranes of wool raised by chlorine (epicuticle) and by bromine have been isolated and their thicknesses determined by electron microscopy of gold-shadowed specimens. These were found to be 32�10 A and 140�40 A respectively. The epicuticle consists of 78% protein, 5% lipid, 4% ash, and a negligible amount of carbohydrate. Amino acid analyses of the epicuticle and the dissolved protein which fills the Allworden sacs show that (with the exception of glycine) those amino acids which are present in larger amount in the epicuticle than in the whole cuticle are present in smaller amount in the dissolved protein and vice versa. Furthermore, the amino acid composition of the epicuticle resembles that of the cuticle more closely than that of the protein from the cell membrane complex. This fact, together with its low lipid content, suggests that it may not originate from the cuticle cell membrane complex.