THE PROTEINS 



glutamic acid, which forms 8 per cent of egg albumin and only 1 -7 per cent, 

 of globin (derived from haemoglobin), amounts to 36-5 per cent, in gliadin, 

 the protein extracted from wheat flour. Striking differences are also notice- 

 able in the relative proportions of the diamino-acids and bases, the so-called 

 hexone bases. Whereas in casein they form about 12 per cent, of the total 

 molecule, in globin they form about 20 per cent., and in the protamines, 

 salmine and sturine, about 85 per cent, of the total molecule consists of these 

 bodies. On this account the two last-named bodies have a strongly basic 

 character. From these figures it is evident also that certain of the amino- 

 acids must occur many times over in the protein molecule. Thus in globin, 

 if we assume the presence of one tyrosine molecule, there must be at least 

 thirty- two leucine and ten histidine molecules. On these data the molecular 

 weight of haemoglobin would come out at about 14,000, a figure which agrees 

 with that derived from a study of the amounts of sulphur and iron respec- 

 tively in its molecule. 



THE DISTRIBUTION OF NITROGEN IN THE PROTEIN 



MOLECULE 



Attempts have been made to differentiate among the proteins by a 

 method which, while less laborious than the isolation and recognition o: 

 individual ammo-acids, may yet throw some light on the manner in \\ 

 the nitrogen is combined within the molecule, and on the relative amou 

 the different classes of nitrogen groups which may be present, 

 which was devised by Hausmann, is carried out as foUows. 

 the protein is dissociated by boiling with strong hydrochloric << 

 nitrogen, which has been split off as ammonia and is present m tl 



