Uridin and cytidin phosphoric acid

Abstract

In a series of articles published in course of the last few years, Walter Jones and his co-workers advanced a theory on the mode of linkage of the four nucleotides taking part in the molecular structure of yeast nucleic acid. According to these authors, the nucleus of yeast nucleic acid is a tetra ribose of the following structure [(C₅H₁₀O₅)₄—₃H₂O]. The assumption was based on the isolation of three substances which the authors viewed as dinucleotides, having the properties of a tetrabasic acid. In a previous publication the present author expressed the view that the experimental evidence adduced by Jones and coworkers was not sufficient to establish their theory. It also seemed to the present author that the experimental evidence presented was insufficient to establish the individuality of the guanosin 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 nucleotides 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 cytidinphosphoric acid.

The barium salt of uridin-phosphoric acid had a specific rotation of [α]²⁰ _D = + 3.5°. 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 cytosinepicrate from the mother liquor was unsuccessful.