242 



KERATIN AND KERATINIZATION 



In these extractions a number of processes are involved, the rates of some 

 of which are diffusion controlled, the limiting step being either the ingress 

 of the reagent on the egress of the dissolved protein. These rates differ in 

 the two segments (o and p, see p. 268) of the fibre and probably the 

 o-segment contributes most of the extracted protein. 



The analysis of kerateine-2 by Simmonds (Table 18) shows that relative 

 to the original wool it contains : increased amounts of the di-amino acids, 



Table 17. Amino Acid Composition of Whole Wool and 



Various Fractions. (Simmonds and Steel, 1956.) 



(Amino acid-N as per cent total-N). 



leucine, lysine and ammonia N, and less of cystine, proline, serine and 

 tryptophane. Harrap's (1955) molecular weight determinations by means 

 of a surface balance suggest a magnitude of 30,000. Table 17 shows the 

 change in composition between the first extract A and the major component 

 "kerateine-2". It is evident from the analyses that a-keratose and kera- 

 teine-2 are not derived from precisely the same original fraction but there 

 appears to be some " overlap". There is thus reason to think that 

 numerous separate polypeptides exist in the original wool and that the 

 various solubilization procedures sample these differently. 



