244 KERATIN AND KERATINIZATION 



showed that all these preparations were more polydisperse and unstable 

 than had been previously described. They concluded that possibly the 

 solutions contain monomers in equilibrium with aggregates and that there 

 may be complicating factors in changes of shape and solvation under 

 various conditions. Further, in most cases some peptide bonds are broken 

 as well as disulphide bonds and special precautions must be taken to 

 prevent further hydrolysis with time. Moreover, most solutions show, 

 superimposed on these changes, others due to a progressive aggregation of 

 material with standing. They are not hopeful that the various effects due 

 to aggregation and disaggregation, hydrolysis, changes in shape and 

 solvation can be distinguished. In later articles, Woods (1952) and 

 Gillespie et al. (1960) take a somewhat gloomy view of the possibility of 

 further analysing these solutions, since apart from the actual experimental 

 difficulties, the theoretical interpretation of the results in such systems is 

 also obscure. Nevertheless when the whole of the results obtained from 

 solubilized wool keratin is reviewed it is clear that several significant 

 conclusions emerge: 



(a) It is possible to extract from wool quantities (50-60% of weight) of 

 an a-type, fibre-forming protein which are low in cystine and have other 

 significant departures in composition from the original wool. This may be 

 termed the a-component ; its oxidized form is a-keratose with a molecular 

 weight of the order of 50,000-80,000. Kerateine-2 appears to be a related 

 product. The actual analyses in part support this view. 



(b) In addition to the a-component, other less well-defined, probably 

 heterogeneous polypeptides, of smaller molecular weight (3000-10,000) and 

 higher in cystine, can be extracted. These are, in their reduced form, 

 contained in part in Lennox and Gillespie's A-E extracts and, when 

 oxidized, Alexander's y-keratose. These polypeptides show little tendency 

 to form fibres. 



(c) These various polypeptides may be linked by oxidation of their thiol 

 groups to reform higher polymers and insoluble, partly-synthetic keratins. 



(d) Even in the absence of the possibility of disulphide cross-linking they 

 still exhibit a marked potentiality for aggregation. This property probably 

 arises from the multiple possibilities of interaction between the rich side- 

 chain population of the keratin polypeptides, and may well be of impor- 

 tance in the formation of the initial fibrous aggregates in the follicle prior 

 to the formation of disulphide bonds. 



The similarities between a-keratose, kerateine-2 and Lindley's (1947) 

 cetylsulphonic acid (CSA)-soluble extract on the one hand and y-keratose 

 and the CSA-insoluble fraction on the other, have also been pointed out by 

 Earland and Wiseman (1959) and are brought out in their table (Table 19). 

 The CSA method is effective although the disulphide bonds remain largely 

 intact. 



