THE KERATINIZATION PROCESS 



237 



hydrogen-bond breakers, and reducing agents at a more moderate pH 

 (7-8). As reducing agents, thioglycollic acid, bisulphites, sulphides, 

 cyanides, mercaptoethanol, etc., have been used. By using a lower pH it 

 was hoped that peptide-bond hydrolysis and the conversion of the cystine 

 bridge into the more stable lanthionine bridge ( — CH 2 — S — ) could be 

 avoided. 



Table 14. Comparison of Amino Acid Composition 



of Wool and the Low-Sulphur Protein (a- 



Fraction) of Wool Roots (Rogers (1959)). 



Amino acid N as % of total N. 



About a quarter of the weight of wool dissolves in 5% sodium bisulphite 

 (pH8) and 10 M urea at 50°C in 24 hr (Jones and Mecham, 1934; 

 Mercer, 1949a). The extraction portion is now known to come from the 

 less keratinized orthocortex (see p. 268). When reprecipitated by the 

 addition of ammonium sulphate the extracted keratin derivative is obtained 

 as a white, sticky, coherent curd very closely resembling Rudall's epider- 

 min and Alexander's a-keratose (q.v.). Like these it can be drawn into 

 birefringent threads which give an a-type X-ray pattern. The attempts 

 made to estimate the molecular weight of extracts in urea are not wholly 



