G6 



D. SHUGAR 



be concluded that the production of each of these involves a different de- 

 composition path. However, since measurements were made only after 

 complete disruption of absorption spectra, no conclusions can be drawn 

 regarding intermediate decomposition products. 



Irradiation of uric acid (I) at 253.7 nux, followed by concentration of the 

 solution, resulted in the isolation in about 10% yield (with respect to the 



HN 



<) 



/\ 



=0 



N 



H H 



(I) 

 Uric acid 



O 



L 



H 2 N C 



A N /- 



O 



>=0 



H H 



(ID 

 Allantoin 



H 2 N H 

 O 

 

 C 



NH 2 



H.N 



NH, 



OC 



CO 



N— C— 

 H H 



(III) 

 Allantoic 



acid 



OC O CO 



I II I 

 N— C— N 

 H H 



(IV) 

 Triuret 



original substance) of crystalline triuret (IV) 124 and it has been proposed 

 that the reaction may proceed via formation of allantoin (II) and allantoic 

 acid (III), followed by decarboxylation and oxidation. 



The isolation of parabanic acid from irradiated uracil 125 (see Section V, 

 4, a) suggests other conceivable pathways for the above reaction. Cyanuric 

 acid was also detected in small amounts in irradiated uric acid. 124 



3. Purine Nucleotides and Nucleotide Coenzymes 



Nucleosides and mononucleotides of adenine and guanine are, like the 

 parent purines, remarkably resistant to irradiation 36 ' 118 but, under analo- 

 gous conditions, ATP undergoes considerable degradation to adenine while 

 the photoproducts of diphosphopyridine nucleotide (DPN) include adenine 

 and small amounts of inorganic phosphorus (P), the absence of adenosine 

 indicating that the glycosidic linkage in both adenosine diphosphate (ADP) 

 and ATP is labilized by the pyrophosphate group. 108 The spectral changes 

 resulting from irradiation of DPN are accounted for almost entirely by 

 degradation of the nicotinamide ring. 108 ' 126 



Irradiation of DPN to the point where its coenzyme activity is completely 



124 J. Fellig, Science 119, 129 (1953). 



125 W. E. Conrad, Radiation Research 1, 523 (1954). 



126 M. W. Seraydarian, A. I. Cohen, and H. Z. Sable, Am. J. Physiol. 177, 150 (1954). 



