The Chemical Composition of Wool II. Analysis of the Major Histological Components Produced by Ultrasonic Disintegration

Abstract

Ultrasonic disruption of powdered Merino wool in formic acid and dichloroacetic acid causes some protein to be dissolved, but the amino acid content of the residual wool is unchanged by the treatment. Cortical cells and disrupted cortical cells are found to have the same composition as the parent fibre, which is to be expected because the latter consists of about 90 % cortical cells. However, the cuticle of Merino wool is different in composition from the parent fibre, being richer in cysteic acid, serine, proline, glycine, valine, and cystine, and poorer in aspartic acid, threonine, glutamic acid, methionine, isoleucine, leucine, tyrosine, phenylalanine, and arginine than the whole fibre. Thus the cuticle is considerably less polar than the fibre as a whole. With the exceptions detailed below, it is found that the first group of amino acids listed above are classified as non a.helix.forming and the second group as a·helix· forming by Blout (1962). The exceptions are isoleucine and threonine, whilst arginine and glycine are not classified. It is therefore postulated that the cuticle is amorphous because of its high content of non a·helix.forming amino acids. The cuticle of Lincoln wool shows similar differences to those already given for Merino cuticle but, in addition, contains less lysine and histidine than the whole fibre.