136 



FINE-STRUCTURE OF PROTOPLASM 



11 



macromolecular Spheres, but also the hydration water inside the glob- 

 ular molecules, so that their structure is destroyed and the solubilitv 

 of the protein is abolished. This physico-chemical transformation of 

 soluble proteins is called denaturation. There are some indications that 

 the denaturation of globular proteins consists in an unfolding of the 



? 



«) 



1/ 



/ \ 



V) 



Fig. 90. Model of the fine-structure of protein (from Frey- 

 Wyssling, 1944b). a) Lattice of spherical macromolecules 

 (slightly anisotropic or isotropic; highly hydrated); b) chain 

 lattice of thread molecules (strongly anisotropic, barely hy- 

 drated). The transformation a -> b is termed "denaturation". 



wrapped-up polypeptide chains. In Fig. 90 the denaturation of globular 

 into fibrillar proteins is indicated by an arrow a -> b. The inverse 

 reaction, the transformation of the denatured protein into globular 

 molecules, is usually impossible in vitro, but it must occur readily 

 in vivo. Forms of protein molecules intermediate between the globular 

 and chain configurations are not well known. Such intermediate 

 shapes do not crystallize out, but it is probable that they are involved 

 in protein metabolism. Fig. 95c (p. 144) shows the length of the poly- 

 peptide chain which is folded up in a globular protein molecule of 

 100 A diameter, 



Ranzi (195 i) has devised a method for distinguishing globular 

 from fibrillar proteins in dilute solutions. The first show an increase 

 in viscosity with KCNS as compared with a test solution equimolar 



