RADIOLYSIS OF 4-THIORURACIL AND OF 4-THIOURACIL MOIETIES OF 4-THIOURIDINE AND TRANSFER RIBONUCLEIC ACID FROM ESCHERICHIA COLI IN AQUEOUS SOLUTIONS

4-Thiouracil, 4-thiouridine and tRNA from Escherichia coli were irradiated with X-rays in air-saturated solutions and the radiolysis of the 4-thiouracil moieties was determined spectrophotometrically. The dose-effect curves were exponential, giving initial yields of destruction (G value) of 3.22 for thiouracil, 2.45 for thiouridine and 0.31 for the thiouracil residues in tRNA. The thiopyrimidine residues were more radiolabile than the corresponding oxygen analogues, as the G values found for uracil and uridine under the same conditions were 2.28 and 1.83, respectively. The following radiolysis products were demonstrated in irradiated thiouracil solutions: uracil, thiouracil disulfide, isobarbituric acid, di-isobarbituric acid and inorganic sulfate. Radiolysis products identified in irradiated thiouridine solutions were uridine, thiouridine disulfide and sulfate. © 1968.