Fragmentation of thymidine induced by ultraviolet photoionization and thermal degradation

Fragmentation of gas phase thymidine at different temperatures was studied with vacuum ultraviolet radiation and time-of-flight spectroscopy. Partial ion yield measurements were carried out in order to study the appearance energies of thymidine and its main fragments. The appearance energies of thymidine and its deoxyribose- and thymine-based fragments were determined to be 8.39, 8.77 and 8.81 eV, independently of temperature. The thermal decomposition of the sample was observed to start around 138-139 degrees C and it was explained by the breakage of the glycosidic bond, accompanied by hydrogen transfer from the deoxyribose ring to the thymine base. (C) 2013 Elsevier B.V. All rights reserved.