166 



KERATIN AND KERATIN IZATION 



Macarthur (1943), Bear (1943) and Bear and Rugo (1951). Table 10 by 

 Schor (1958) summarizes the various reflections reported for the more 

 elaborate feather diagram. Discussion of this is postponed until later (p. 

 208). In a-keratin the longitudinal spacings can be regarded as orders 

 of a master spacing of 198 A and the equatorial spacings as orders of 

 80-90 A. In feather the main longitudinal spacing is usually given as 95 A 

 but Schor prefers 189 A. 



Fig. 68. Composite chart of a-keratin diffraction pattern given by por- 

 cupine quill. Fibre axis vertical; plane plate. (To D = 3 A.) Taken 

 from Macarthur (1943). 



A certain independence between the long spacing (macromolecular 

 level) and the short spacings (molecular level) is suggested by the fact that 

 the large-scale order may be destroyed without affecting the order at the 

 molecular level. This is commonly observed in the regenerated keratins, 

 i.e. materials which have been dissolved and reformed into fibres. These 

 may give either a- or j8- or cross ^-patterns at high angles (Astbury, 

 1947; Rudall, 1946 and 1952; Mercer, 1949a) indistinguishable from the 

 original patterns, but they lack long spacings proving that although 

 the small-scale structures in the a-crystallites have been regenerated the 



