22 



Scientific Proceedings (86). 



cytidine and adenosin-uracil dinucleotides. On the other hand, 

 it seemed to the present author that a cytosin-uracil dinucleotide 

 could actually be isolated from the mixture of pyrimidine nucleo- 

 tides previously described by Levene and Jacobs. 



The latter conclusion is now proven erroneous. Employing a 

 different process for the fractionation of the brucine salts of the 

 pyrimidine nucleotides it was possible to separate them into two 

 brucine salts. One of these was converted into a crystalline 

 barium salt of uridin-phosphoric acid, the other into an amorphous 

 barium salt having the composition of the barium salt of cytidin- 

 phosphoric acid. 



The barium salt of uridin-phosphoric acid had a specific rota- 

 tion of [a] 20 D = + 3. 5 0 . The barium salt as well as the products 

 of hydrolysis with 10 per cent, sulphuric acid were tested for 

 amino-nitrogen with a negative result. The base isolated on 

 hydrolysis was pure uracil and the attempt to isolate cytosine- 

 picrate from the mother liquor was unsuccessful. 



The second brucine salt when converted into the barium salt 

 gave a product which differed in composition and in physical 

 properties from that of uridin-phosphoric acid. It deposited 

 from a concentrated aqueous solution as a precipitate consisting 

 of microscopic globules. It apparently had greater solubility 

 and a higher optical rotation than the first salt [a] 20 D = + 14.0 0 . 



It is possible that this salt was not as yet obtained in the same 

 degree of purity as the first. No dinucleotide was for the present 

 isolated from the mixed brucine salts of the pyrimidine nucleo- 

 tides. Of course, it is realized that eventually such conditions 

 of hydrolysis may be found, that will yield dinucleotides. Efforts 

 in this direction are now being made in this laboratory. However, 

 for the present one must admit that the structural formulae 

 advanced by Jones and co-workers are merely a matter of specula- 

 tion, and that the mode of linkage of the four nucleotides of the 

 yeast nucleic acid still remains to be established. Omitting all 

 arbitrary elements the structure of yeast nucleic acid should be 

 represented as follows: 



