CHAPTER I 

 THE THEORY OF MEMORY 



1. The Faculty of Protein to Memorize Its Structure 



As was described repeatedly, many evidences can be presented 

 suggesting that protein molecules can return to the structural pat- 

 tern, which they once possessed, when their structure is disturbed by 

 some adequate agents. The writer designates such a phenomenon as 

 the reversibility of protein structure or the memory ©f protein. Since 

 this phenomenon is of the most importance to elucidate the mechanism 

 of both the individual development or ontogeny and the organic evolu- 

 tion, it will further be discussed in this chapter in great detail. 



In general, the reversible inactivation of physiologically active 

 proteins such as enzymes and toxins can be looked upon as based upon 

 this character of proteins. With viruses many phenomena apparently 

 due to this character are also known. For example, a virus which has 

 been changed in its property by an environmental change may recover 

 its original property when brought under another environmental con- 

 dition. 



This phenomenon can be interpreted as indicating that a protein 

 which can take two structures, A and B, attains one structure, A, 

 under a condition where A-structure is stable, while under another 

 condition where the other structure, B, is stable it is shifted to the 

 structure B as follows : 



h 



A-structure 7=^ ^-structure. 

 a 



^-structure is stable under the condition of "a" and 5-structure 

 under "6", but in most cases i4-structure seems not to be shifted to B 

 by a mere change of the environmental condition, a -^b, unless some 

 proper stimulus disturbing the protein structure is provided. This may 

 be analogous to the phenomenon that water can be coold under O^C. 

 without changing into ice, but that the super-cooled water will be 

 suddently frozen over on the application of an appropriate stimulus. 

 This phenomenon was already discussed as we dealt with the denatu- 

 ration of proteins (Chapter X, Part III). 



