418 JOSEPH H. PKATT 



group to phosphoric acid. This constitutes the long sought synthesis of a 

 nucleic acid, although the product is not identical with any known to occur 

 in nature. Davis and Benedict have isolated from beef blood as a crystal- 

 line substance a compound of uric acid and pentose. This is a uric acid 

 nucleosid, the possible existence of which had been suggested by the im- 

 portant discoveries of Levene. 



The theory that yeast nucleic acid was composed of four nucleotids 

 was presented by Levene(c?) in 1909, and its correctness conclusively 

 proved by Levene, Jones, Thannhauser, and their co-workers. All four of 

 the nucleotids have been separated from yeast nucleic acid in pure crystal- 

 line form. Cytosin nucleotid by Thannhauser and Dorfmuller(&) in 

 1918, adenin nucleotid by Jones and Kennedy in 1918; guanosin nucleo- 

 tid (guanylic acid) by Levene(c?) in 1919; uracil nucleotid by Levene(e) 

 in 1920. Levene has found that a mild hydrolysis with 5 per cent am- 

 monia at a temperature of 100 C. breaks up yeast nucleic acid into its 

 four mononucleotids. 



HO 

 Guanin Nucleotid O=P O . C 5 H 8 O 3 . C 5 H 4 N 5 O 



HO/ 



HO\ 

 Adenin Nucleotid O=P O . C 5 H 8 O 3 . C 5 H 4 N 5 



HO/ 



HO\ 

 Cytosin Nucleotid O=P O . C 5 H 8 O 3 . C 4 H 4 N 3 O 



HO/ 



HO\ 

 Uracil Nucleotid O=P O . C 5 H 8 O 3 . C 4 H 3 N 2 O 2 



HO/ 



Jones holds that the linkages of the mononucleotids is through the 

 carbohydrate groups and presents experimental evidence in support of this 

 view. 



Yeast nucleic acid has been decomposed by neutral hydrolysis with 

 the formation of four nucleosids (Levene and Jacobs). 

 Guanosin C 10 H 13 N 5 O 5 



Adenosin C 10 H 13 N 5 O 4 



Cytidin C 9 H 13 N 3 O 5 



Uridin C 9 H 12 N 2 O 6 



Levene * has recently prepared nucleic acid from the spleen, pancreas 

 and liver. None of the samples contained pentose. The two purin bases 

 adenin and guanin were present in each, but the amount was much greater 

 in the spleen nucleic acid than in the others. 



1 Levene. "Preparation and Analysis of Animal Nucleic Acid," Journ. Biol. Chem., 

 1921, 48, 177. 



