I 



120 ALTERATIONS IN ALKALI PROTEINS 



Actual experiments on the combination with alkali of 

 compounds with the Dakin tautomerism have not yet appeared. 



The difference in optical rotation between proteins and their 

 salts with alkali observed by Pauli and M. Samec,* in direct 

 analogy with the optical activity of the acid salts of the proteins 

 already discussed, must not be confused with this variation in 

 rotation with time. 



It has already been mentioned that salts of the proteins with 

 bases show a regular behaviour in their combination with 

 alkali in increasing concentrations ; the alteration in viscosity 

 due to hydration of the alkali salt also varies in the same 

 manner. Further, the order for different bases corresponds to 

 that of their dissociation constants. With addition of alkali, 

 the optical rotation is also observed to increase to a maximum 

 corresponding to the saturation point. This value, however, 

 remains constant on further addition of alkali. As in the case of 

 acid, excess of alkali gives no decrease in rotation which can be 

 attributed to repression of the ionisation. Thus, here again it is 

 only the formation of the alkali protein and not the ionisation 

 which affects the rotation. 



Table 66. 

 Optical Rotation <x on addition of Alkalis. 



The optical rotation is thus affected in the same way by 

 combination with both acid and alkali, and it is to be presumed 

 that the effect on the albumin molecule is similar in both cases. 

 Possibly the entrance of acid or metal affects the asymmetric 

 carbon atom nearest the peptide linkage in the same way in the 

 two cases. 



* Biochem. Zeitsch., 1914, 59, 470. 



