THE NUCLEOPROTEIDS 279 



cornerstone for his whole investigation of the uric acid group, Purine is 

 a strong base, readily soluble in water. Its constitution is evident from 

 its preparation. It has the following structure: 



N = CH 



HC C NH 



II II \ CH 

 N C N^ bil 

 Purine 



In order to make it possible to have a uniform nomenclature for the 

 numerous representatives of this group, Emil Fischer numbered the purine 

 ring in the following manner : 



v/6 



C 5 -N 7 



N 3 C 4 N 9 ^ 



We shall make use of this scheme. 



Uric acid itself has the following structural formula: 



HN CO 



COC 1 



;co 



-NH 



HU-NH 



Uric acid (2, 6, 8-trioxypurine) 



This formula harmonizes with the following important transformations 

 of uric acid. 



By heating with hydriodic acid and fuming hydrochloric acid in a sealed 

 tube, glycocoll, carbon dioxide, and ammonia are produced. 



Oxidizing with nitric acid or chlorine produces alloxan and urea. 

 Alloxan is mesoxalyl urea: 



HN CO NH CO MTT 



I /NH2 



NH CO CO + CO 



N CO + O + H 2 O =| \ MTT 



NH X NH CO 



Uric acid Alloxan 



By oxidation of alloxan we obtain parabanic acid, which is oxalyl urea : 



CO NH 



)co 



CO NH 



Parabanic acid 



which decomposes, on boiling with water, into urea and oxalic acid. 



