PROTEIN AND PROTOPLASMIC STRUCTURE 



Kurt H. Meyer 



I should like to refer to a theory of protoplasmic structure which 

 Seifriz and I independently advanced at about the same time. On 

 the basis of the highly elastic extensibility of Amoebae, erythrocytes, 

 and other cells, Seifriz, in 1929' concluded that the ultimate struc- 

 tural units of the living substance are probably linear molecules or 

 micellae so arranged as to form a framework. We, on the other hand, 

 in 1928- and 1929'' showed that there are two types of pro- 

 teins, the fibrillar and the globular ones; the spherical form of the 

 latter was proved by Svedberg. We demonstrated the undoubted 

 presence of fibrous molecules, or elongated polypeptide chains, in 

 silk, sinew, and stretched muscle. From this it followed that "the 

 living substance is composed of a true network of primary valence 

 chains which at several points are coated by a hydrated layer, and 

 at other points are tied together by chemical bridges held by mole- 

 cular cohesion" (today one would say residual valences or hydrogen 

 bonds) . Proof that a macroscopic change in form, such as muscular 

 contraction, is accompanied by a change in form of protein chains, 

 led us to the assum.ption-' that visible contraction and elongation 

 in muscle or protoplasm is to be ascribed to the contraction and 

 elongation of fibrous protein molecules, which in turn are controlled 

 by chemical activities. 



These were the older concepts. The question now arises, what 

 contributions have since been made in support of this theory. Under- 

 standing of the change in molecular form, especially reversible form 

 changes, is still very meager. Most noteworthy are the changes in 

 molecular configuration observed by Gorter, van Ormondt, and 

 Dam^ in egg-albumen films spread on water. At pH 5 the films 

 are quite flat but below this pH value they are shrunken to one-tenth 

 of their former area. 



'Amer. Naturalist, 63, 410. 1929. 



'Ber. dtsch. chem. Ges., 61. 1932, 1928. 



'Bioch. Z. 214, 253. 1929. 



' Proc. Acad. Wetensch. Amsterdam, 35, 838. 1932. 



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