Gas-Phase Fragmentation Studies of Biotinylated, Hexaethylene Glycol–Spacered Oligosaccharides—Molecular Probes—Using Electrospray Mass Spectrometry on a Hybrid High-Resolution Mass Spectrometer

The electrospray ionization high-resolution mass spectra of biotinylated hexaethylene glycol–spacered molecular probes bearing biologically relevant carbohydrate moieties in positive and negative modes were recorded and interpreted. Collisionally induced decay mass spectra (positive mode) revealed different patterns depending on the charge of the parent ion, attached cations (or ions), the composition, and the sequence of carbohydrate fragments. The most intense peaks (two series) originated from the sequential cleavage of glycoside bonds resulting in charge location on the reducing end (Y series observed for all of the test compounds) or nonreducing end (B series). Hexaethylene glycol chain fragmentation giving rise to the cleavage of the C–O bond remote from the biotin moiety was observed. Other fragment ions lighter than the above by a difference of (C2H4O) n were absent or much smaller. Similar fragmentation was found for all of the nonsulfated biotinylated glycosides with the hexaethylene glycol spacer thus demonstrating that this type of fragmentation was characteristic of such molecular probes. Similar cleavages along with biotin moiety decay via the elimination of H2S and H2CS were observed for negative ions in the collisionally induced decay mass spectra of sulfated and neutral molecular probes.