The high‐sulfur proteins of α‐Keratins: Their relation to fiber structure and properties

Abstract

SynopsisIJttrclttted keratins, such as horn and fur, have markedly dissimilar physical properties, and these variations can exist, although to a lesser extent, between two non-identical samples of the same keratin. Each keratin examined contains low-sulfur proteitis which bear resemblance to each other and this is in accord with the concept that all a-keratins contain microfibrils of similar size and structure. However, these keratins can differ greatly in the type and amount of high-sulfur protein which they contain. It is reasonable then to assume that variations in physical properties between keratins must be due, a t least in part, to differences in the proportion or properties of the matrix (high-sulfur protein) which surrounds each microfibril. High-sulfur proteins have been found in every a-keratin examined with horns containing as little as 7% by weight and furs as much as 45% by weight of these proteins. By the supplementary feeding to sheep of cysteine or methionine administered into the abomasum, the high-sulfur protein contetit of wool can be increased by 5075. This opens the possibility of the control of fiber properties by the dietary manipulation of sheep.

Disulfide Cross-Linked Network Structure of Intermediate Filament and Matrix in Hair and Wool Cortices

“…From the amino acid analysis of low-sulfur protein fractions, Gillespie [33,34] showed that the cysteine content analyzed as S -carboxymethyl-cysteine groups in low-sulfur (IF) proteins in wool is 400 µmol/g, which corresponds to 200 µmol/g for numerous SS cross-links ; namely, 20 residues per IF chain.…”

“…Experimental results were analyzed by using nonGaussian chain statistics, and the results are summarized in Table 2 200 20 Table 2 Type, location, and the number of respective SS cross-links in the rod (R) and terminal (E) domains of the IF chain in wool keratin [9][10][11] a) Published by Fraser et al [32]. b) Published by Gillespie [33]. c) Total cystine content of 220 µmol per gram was calculated from the average value of total cysteine content determined by Fraser et al [32] as 22 residues in an IF chain, which were located 7 and 15 residues in rod and terminal domains, respectively.…”

“…The high-and low-sulfur volume fractions of 'd0 and (1 'd0) largely depend on the disulfide content of keratin. Gillespie estimated the weight fractions of both IF and KAP by using the fractional precipitation method for the water-soluble S -carboxymethylated keratin proteins derived from keratin fibers with widely different contents of disulfide [33,34]. The obtained mass fractions of IF in IF-KAP in wool and hair were about 75 % and 57 %, respectively [33,35].…”

“…Gillespie estimated the weight fractions of both IF and KAP by using the fractional precipitation method for the water-soluble S -carboxymethylated keratin proteins derived from keratin fibers with widely different contents of disulfide [33,34]. The obtained mass fractions of IF in IF-KAP in wool and hair were about 75 % and 57 %, respectively [33,35]. Assuming that the density of both IF and KAP materials is the same, these values are somewhat larger than the average data in Table 3.…”