On the Turnover of Purines and Pyrimidines from Polynucleotides in the Rat Determined with N15.

Abstract
Cytosine and thymine may be prepared from 30-50 mg. desoxyribonucleic acid by hydrolysis with formic acid followed by partition chromatography (I) on starch. Cytidine was converted into uridine by treatment with an aqueous soln. of pyridine, and separation effected by I. While free cytosine may be deaminated to uracil by refluxing with 0 4 [image] H2SO4 for 48 hrs., cytidine was converted mainly into uridine with some uracil and cytosine formed. N15-labelled orotic acid was shown to act as a precursor for both ribo-nucleic acid pyrimidines (II) and desoxyribonucleic acid pyrimidines. On H, the cytosine ring has a higher turnover rate than uracil.