THE STRUCTURE OF YEAST NUCLEIC ACID. 
III. AMMONIA HYDROLYSIS. 
By P. A. LEVENE. 
(From the Laboratories of The Rockefeller Institute for Medical Research.) 
(Received for publication, January 31, 1918.) 
Since the tetranucleotide structure of yeast nucleic acid has 
been generally accepted, the efforts of workers in this field of in- 
vestigation have been devoted to a search for an explanation of 
the mode of linkage between individual nucleotides. . The theory 
of the structure of yeast nucleic acid was established through 
the discovery of methods which yielded on the one hand the indi- 
vidual nucleotides and on the other the pyrimidine nucleotides. 
For the explanation of the further details in the structure of the 
substance it was necessary to obtain a fragment of the nucleic 
acid molecule that would possess a more complex structure than 
the simple mononucleotides. Attempts in this direction were 
made by Thannhauser and Dorfmiiller! and by Walter Jones?* 4 
and his coworkers. Thannhauser and Dorfmiiller reported the 
discovery of a trinucleotide, Walter Jones with his coworkers 
the discovery of two dinucleotides. The conclusions of Thann- 
hauser and Dorfmiiller were criticised by Jones who very con- 
vincingly exposed the weak points in the arguments of Thann- 
hauser. 
However, it is now found that the claim of Jones and Germann 
and Jones and Read to have isolated an adenine-uracil dinucleotide 
was not well founded.. Following exactly the same conditions of 
analysis as given by these authors a brucine salt was obtained 
which possessed analytical values required by the dinucleotide. 
On recrystallization out of 35 per cent ethyl alcohol this brucine 
' Thannhauser, 8. J., and Dorfmiiller, G., Z. physiol. Chem., 1915, xcv, 
259. 
2 Jones, W., and Richards, A. E., J. Biol. Chem., 1914, xvii, 71. 
3 Jones, W., and Germann, H. C., J. Biol. Chem., 1916, xxv, 93. : 
4 Jones, W., and Read, B. E., J. Biol. Chem., 1917, xxix, 123; xxxi, 39. 
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