Fragmentation of protonated oligonucleotides by energetic photons and Cq+ ions

The ionization and fragmentation of trapped protonated dGCAT oligonucleotides upon interaction with energetic photons (h nu = 10-570 eV) and keV Cq+ ions was investigated by means of time-of-flight mass spectrometry. The observed fragmentation patterns are dominated by protonated and nonprotonated nucleobase ions and fragments of the deoxyribose moiety. Fragments exceeding the size of nucleosides are almost completely absent. Absorption of VUV photons as well as interaction with keV ions predominantly involves ionization or excitation of molecular valence electrons and accordingly the observed fragmentation patterns exhibit qualitatively similar features. Soft-x-ray-induced ionization of core level electrons accompanied by subsequent emission of an Auger electron shifts the fragment distributions towards smaller masses. This systematic study allows for insights into differences and similarities between ion- and photon-induced excitation and fragmentation mechanisms. In particular, the crucial role of the deoxyribose moiety for radiation-induced DNA damage that was predicted on the basis of gas-phase experiments using isolated deoxyribose molecules is confirmed. DOI: 10.1103/PhysRevA.87.032702