Mass spectrometric investigation of N-sulfonylated purine nucleic bases and nucleosides

The gas/phase behaviour of N-sulfonylated purine nucleic bases and nucleosides towards electron impact (EI) and matrix-assisted laser desorption/ionization (MALDI) occurring in a ion trap of a Fourier transform ion cyclotron resonance mass spectrometer is investigated. The influence of the storage time on the protonated molecule ([M+H](+)) abundance under EI conditions confirms that the formation of these ions proceeds through ion/molecule reactions. Using stored-waveform inverse Fourier transform (SWIFT) selective isolation of M(+.) or H(3)O(+), self-chemical ionization, M(+.)/M, and chemical ionization, H(3)O(+)/M, are detected. Investigation of specific EI expulsion of SO(2), SO(2)H and/or SO(2)H(2) from M(+.) and/or [M+H](+) shows that oxygen protonation in bond;SO(2)bond; proceeds faster than nitrogen protonation. Expulsion of SO(2) from molecular ions is not observed in MALDI mass spectra of nucleosides.