Formation of H Adduct Radicals in Cytosine and Its Derivatives

Summary

Low-temperature irradiation and warming-up experiments were used to study by e.s.r. the radical transformation in irradiated cytosine and its derivatives. It is shown that the H adduct radical of the base observed at room temperature is the result of the protonation of the base-anion radical observed at low temperature. In the nucleoside and nucleotide, this protonation occurs around 230 K. The main sources of protons are the molecules of crystallization and the sugar group. The different mechanisms proposed for the radiolysis of DNA constituents are discussed in connection with these findings.