THE PROTEINS 



101 



It can be synthetised by fusing together in a sealed tube trichlorolactamide 

 and urea. Thus : 



NH 2 CONH 2 



I I 

 CO + CHOH + NH 2 



I I >co 



Th 



NH 9 CCL 



NH 



' 



NH CO 



I I 



CO C NH + NH 4 C1. + 2HC1 



I II >co 



NH C NH' 



e relation of xanthine, hypoxanthine, guanine. and adenine to uric acid 

 is shown by the following formulse : 



NH CO 



II 



CO C NH 



I II >co 



HN -- CO 



II 

 CO C NH 



NH C NH 



Uric acid 

 2 -6-8-trioxypurine 



HN CO N = C.NH 2 



II II 



HC C NH. HC C NH 



N _C _N 



Hypoxanthine 



6-oxypurine 



HN - C^-N 



Xanthine 

 2-6-dioxypurine 



NH CO 



II 

 NH 2 C C NH 



N C N 



Adenine 

 6-amino-purine 



N C N 

 Guanine 

 2-amino 6-oxypurine 



Closely allied to this group of bodies are the chief constituents of tea, 

 coffee, and cocoa, namely caffeine, which is trimethyl dioxypurine, and 

 theobromine, which is dimethyl dioxypurine. From the structural formulse 

 given it will be seen that the purine radical contains two nuclei. The 

 nucleus 



N C 



I I 

 C C 



I I 



N C 

 is spoken of as the pyrimidine nucleus, pyrimidine having the formula 



I I 

 2 HC 6 CH 



I II 

 3 N 4 CH 



The other is the radical which we have met with' already in histidine, a 

 disintegration product of proteins, namely iminazol : 



HC NH 



HO-N 



Besides the purine bases proper, we find among the disintegration products 

 of nucleic acid a series of bases derived from the pyrimidine ring. These 

 are uracil, thymine, and cytosine. 

 URACIL is 2-6-dioxypyrimidine, 



