A theoretical and mass spectrometry study of the novel mechanism of N-glycosidic bond cleavage in nucleoside

The fragmentation pathways of ribonucleosides, deoxynucleosides and isopropylidenenucleosides were investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS) in both positive and negative mode. Novel fragmentation pathways investigated using deuterium-label experiment provided important insight on the nature of N-glycosidic bond cleavage. The deuterium of 5′-hydroxyl group on ribose moiety was deprived by the nucleobase, and a novel five-member ring through 5′-oxygen and 1′-carbon was formed in the ribose residue as the lost neutral molecule, instead of a new double bond generating between 1′-C and 2′-C as the literature reported. The novel fragmentation pathway was supported by density functional theory calculations.