ELASTIC DEFORMATION OF PROTEIN 

 CHEMICAL STRUCTURE 



(Supplement to The Chemical Organization of Living Matter 



by C. F. Krafet) 



Copyright 1938 by Carl F. Krafft 



Double-strand polypeptide spiral 



Wool fibers in an atmosphere of steam can be stretched 

 elastically to twice their original length, which means 

 that each molecule of the protein of which the fiber is 

 composed must have this same elasticity. The chemical 

 structure of the protein must therefore be such as to 

 permit elastic stretching to twice its original length, but 

 no more. The only explanation which has been recog- 

 nized is that of W. T. Astbury, who assumes that the 

 polypeptide chains of wool keratin and other proteins 

 are ordinarily folded into diketopiperazine rings with 

 intermediate — CO — CHR — NH — groups, but pass over 

 into the simple zig-zag form when tension is applied. 

 Notwithstanding its general acceptance, Astbury 's ex- 

 planation seems entirely inadequate. The change from 

 the normal configuration (alpha-keratin) to the stretched 

 configuration (beta-keratin) would have to result either 

 from bending of the valence-bonds, or from swiveling 

 about the same. If it results from bending, then we 

 would have to assume that some of the valence-bonds can 

 be bent elastically through 180 degrees, which is unusual 



