MOLECULAR AND M ACROMOLECULAR STRUCTURE 



207 



Evidence for the existence of large macromolecular units of this kind 

 may be sought in the products which result when fibres are dissolved. 

 For feather, as for wool and hair (Chapter VI) unfortunately the solubili- 

 zation process is drastic and destructive of larger units. Ward, High and 

 Lundgren (1946) using a detergent and reducing agents have dissolved 

 feather and found a molecular weight of a detergent-feather complex of the 

 order of 30-40,000. They concluded also that the particle was elongate and 



Fig. 88. A proposal due to Bear and Rugo (1951) for the fibrillar structure 

 of feather keratin. Two packings of ellipsoidal molecules which would 

 account for the pattern of long spacings remaining after successive 

 treatments with hot water have disorganised the wide-angle pattern, are 

 illustrated. An example of an " aggregation of macromolecular particles 

 model ". Reproduced by permission. 



the mixture polydisperse. Probably the molecules were unfolded by the 

 process. If formed into a sphere, a molecule of the molecular weight found 

 by Ward et at. would have been of a size as envisaged by Bear and Rugo. 

 More recently Woodin (1954a and b) using a reducing solution containing 

 urea obtained an electrophoretically-homogenous material. Osmotic 

 pressure measurements, viscosity, sedimentation rate and light scattering 

 concurred to give a molecular weight of the order of 10,000 and showed 

 that the particle was rather asymmetric (Woodin, 1955). Rougvie (1954) 

 found the same particle weight in an extract of feather oxidized by peracetic 

 acid (see also p. 163). 



The infra-red absorption spectra of feather has provided information 

 about the orientation of hydrogen bonds. The CO stretching mode 



