^ GENERAL PHENOMENA OF NUTRITION 57 



formation of such a salt cannot be explained if the two mononucleotides 

 are joined through the PO 4 . Therefore, the nucleotides in this dinu- 

 cleotide, and those in nucleic acid, must be joined through the carbohy- 

 drate. This was also verified when using the method described by Jones 

 and Gehrmann ; Levene 1 takes exception to these conclusions. He calls 

 attention to the fact that nucleotides, forming tetrabrucine salts, might 

 be linked through the carbohydrate group of one and through the base 

 of the other. He emphasizes that further work is necessary before 

 deciding between the two possibilities, and that work should also be 

 carried out on other nucleic acids such as thymus nucleic acid. Levene 2 

 in continuing this work secured evidence that there is no experimental 

 proof that the nucleotides in yeast nucleic acid were bound together 

 through the carbohydrate group. He does not believe that a tetra- 

 riboseis the nucleus of yeast nucleic acid. He considers that the 

 work in his laboratory, and in Jones', indicates the tetranucleotide 

 structure of nucleic acid. The following three nucleotides were iso- 

 lated in pure form: guanylic acid, uredinephosphoric acid and ade- 

 nophosphoric acid. 



Levene 3 in later investigations has written the structure of yeast 

 nucleic acid as follows : 



H0\ 



O = P CgHiA.Cs^NsO 

 HO/ 



H0\ 



O = P C 5 H 8 04.C4H4N 3 

 HO/ 



HO\ 



O = P 



HO/ 



H0\ 



= P 

 HO/ 



1 Levene, P. A. The structure of yeast nucleic acid. J. Biol. Chem. 31, 

 591-8, 1917. 



2 Levene, P. The structure of yeast nucleic acid. II. Uridinephosphoric 

 acid. J. Biol. Chem. 33, 229-234. 



3 Levene, P. A. The structure of yeast nucleic acid. Jour. Biol. Chem. 31 

 (1917), 591-598; The structure of yeast nucleic acid. II, Uridinephosphoric acid. 

 Jour. Biol. Chem. 33 (1918), 229-234; III, Ammonia hydrolysis. J. Biol. Chem. 33 

 (1918), 425-428. 



