44 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



B. 



The data in our possession show definitely that the various 

 proteins are composed of the same units ; in some cases certain are 

 missing and in other cases one or more units are present in very much 

 larger amount. These differences on the whole confirm our classi- 

 fication of the proteins on physical properties. No great differences 

 are noticeable between the members of any single group except in the 

 case of the scleroproteins. Although two proteins in any group may 

 contain the same amount of any unit we cannot say that they are 

 identical. Even if they contained the same amount of all the units 

 they might still be different, for the arrangement of the units in the 

 molecule may not be the same. The following brief particulars may 

 be noted : 



Protamines. 



The protamines are built up almost exclusively of diamino acids, 

 salmine containing over 80 per cent, of arginine. Only small amounts 

 of monoamino acids are present in them ; the actual monoamino acid 

 present is very curious, and still more curious is its quantity, namely, 

 7 -8 per cent, of serine and n per cent, of proline in salmine, and 8*3 

 per cent, of tyrosine in cyclopterine. Another feature of salmine is 

 the presence of 87 per cent, of arginine and the absence of lysine arid 

 histidine ; these peculiarities recur in clupeine and cyclopterine. It is 

 possible that the monoamino acids may be due to impurity, for only 

 at maturity is fish sperm made up of protamine and nucleic acid, 

 whereas at other times histone takes the place of protamine, and 

 histones contain less diamino acids. Kossel and Dakin's analysis of 

 salmine appears to show us a quantitative result. 



The presence of diamino acids in all proteins led Kossel to suppose 

 that there was a protamine nucleus (i.e. of diamino acids) in all pro- 

 teins. The more recent work, especially that of Osborne and his col- 

 laborators on the gliadins, where the diamino acids are present in such 

 small amounts, though it supports the theory, yet suggests that pro- 

 teins may exist in which a protamine nucleus is absent, more especially 

 if the view of Emil Fischer be taken that all the proteins we know, 

 even the crystalline ones, are still mixtures of several proteins. The 

 isolation from proteins of complexes containing only diamino acids 

 will be the only proof of a protamine nucleus in a protein molecule. 



