110 II. FUNDAMENTAL STRUCTURE OF PROTOPLASM 



native protein particles in size and shape. Again, the action of 

 nuclease leads to the cleavage of the bond between protein and nucleic 

 acid and to a loss of biological activity, but the shape of the particles 

 is not altered by nuclease. It seems evident, therefore, that the shape 

 and size of the virus particle are determined by the protein, nucleic 

 acid apparently having no concern with it. On the other hand, it is 

 stated that the molecular weight of desoxyribonucleic acid is 1.5 or 

 3.7 million ; the length of this thread-like molecule is about 500 mju. 

 (155). Such a macro-molecule might be an artifact, yielded during the 

 isolating procedure, as nucleic acids may have a great tendency to 

 undergo polymerization.. 



Jordan (156) stated that all values of the molecular weight of 

 nucleic acids, which have been determined from isolated sedimentation 

 and diffusion constant determinations, must be regarded as unreliable. 

 It is by no means certain that solutions of nucleic acids at the con- 

 centrations normally studied are molecularly disperse. The presence 

 of divalent cations have shown to cause considerable aggregations, 

 and it has been shown that the variation of light transmission with 

 concentration shows a critical region at a concentration of 0.003 per 

 cent which is regarded as an indication that aggregation commences 

 at this concentration. 



Monne (157) expressed the opinion that protoplasm is constructed 

 of fibrils which consist of ribonucleic acid and nucleic acid free-sec- 

 tions regularly alternating with each other. Pederson (158) claimed 

 that conjugated proteins containing non-protein components have a 

 structure in which non-protein components are inserted like cement 

 among bricks of protein molecules ; thus these latter combining 

 indirectly with one another through the inserted substances. Schmidt 

 (159) considered likewise that in chromosomes nucleic acids are inter- 

 posed like cement among the polypeptide chains of proteins. 



Nucleic acids have long been known to possess the property to 

 combine preferably with various proteins ; owing to this property they 

 were frequently used as precipitating agent of proteins. Even when 

 no precipitate is formed, the formation of compounds between nucleic 

 acids and neutral proteins is proved by a drop in the osmotic pressure 

 of the dissolved protein and also by the loss of the high viscosity (160). 



If protein molecules are cemented by nucleic acid, the alteration 

 of the protein structure may scarcely occur. In fact, Carter and 

 Greenstein (151) reported on a protective effect of desoxyribonucleic 

 acid upon the heat coagulation of egg albumin. Nucleic acids may 

 serve as an agent to prevent free motions of the peptide chains in the 

 protoplasm, in contrast to lipids which may operate as a lubricating 

 oil to facilitate the change of polypeptide chains. 



