Gas-phase fragmentation studies of biotinylated oligomannuronopyranosides under conditions of collisionally activated dissociation

Resumo

High-resolution electrospray ionization mass spectra (MS and MS/MS) of a series of glycoconjugates containing biotin and oligomannuronopyranosyl residues linked via a hexaethylene glycol spacer were recorded in the positive and negative ion modes and interpret. In collision activation mass spectra of the positively charged ions (CID MS²), two series of the most abundant peaks were attributed to the fragments resulting from a glycosidic bond cleavage with localization of a charge at either reducing (Y series) or non-reducing end (B series). Fragmentation of hexaethylene glycol chain observed at relatively high activation energies (30 eV or higher) occurred predominantly at the C—O bond most distant from the biotin moiety. In the mass spectra of the negatively charged ions of the studied compounds, the peaks of B, C, and Z series (a systematic nomenclature for carbohydrate fragmentations was used) were present along with the peak analogous to the aforementioned one, which arose from the cleavage of the same C—O bond. The distinctive feature of the fragmentation of the negative ions is the elimination of H₂S and H₂CS from the biotin moiety.