Chemical Effects of Tritium Decay in Aqueous Solutions of Cytosine

Abstract

The products resulting from the decay of tritium in doubly labelled [2-14 C,5-3 H]cytosine were determined in diluted oxygenated or deaerated aqueous solutions. The effort was to recognize the relative importance of the transmutation effects and internal /?~-radiolysis. To achieve this, experiments were carried out in the presence of a large excess of non-radioactive cytosine (the diluent addition method). Equations were derived to calculate the decomposition of a labelled parent compound as well as the yields of products. The percent decomposition of [2-14 C,5-3 H]-cytosine per Ή decay was 78% in oxygenated solution and 41% in deaerated solution. Various products that resulted from the transmutation effects were observed in both solutions, a major one with the yield of 28% and 22% per Ή decay in oxygenated and deaerated solutions, respectively. It was suggested that a significant amount of a cytosine cation formed by β~ decay revert to stable cytosine by a hydride ion (H ) abstraction.

Review: Self‐radiolysis of compounds containing tritium and carbon‐14

“…In one of the few literature examples of molecules that contain both a carbon‐14 and a tritium label, Asano et al report that [2‐ 14 C,5‐T]cytosine stored in oxygenated water (for 200 days) and deoxygenated water (for 500 days) had different decomposition profiles with eight distinct products (by radio‐high‐performance liquid chromatography [HPLC] analysis) and 17 (oxygenated sample) and 20 (deoxygenated) spots by radio TLC analysis 121 . In oxygenated samples, impurities resulting from tritium decomposition were significantly greater than those resulting from carbon‐14 decomposition 121 . It is also reported that [2‐ 14 C,5‐T]uracil (stored in 1% aqueous tert‐butanol) decomposed 16% in 121 days while storage in oxygenated water resulted in 58% decomposition in 127 days forming formyl urea, isobarbituric acid, alloxan, and parabanic acid.…”

“…Loss of tritium from [2‐ 14 C,5‐T]uracil afforded a carbocation that reacts with either water or oxygen to afford 5‐ and 6‐hydroxyl uracil indicating an equilibrium between the cationic uracils (Figure 7). 72 …”