Branching pattern and sequence analysis of underivatized oligosaccharides by combined MS/MS of singly and doubly charged molecular ions in negative-ion electrospray mass spectrometry
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We previously reported that sequence and partial linkage information, including chain and blood-group types, of reducing oligosaccharides can be obtained from negative-ion electros-pray CID MS/MS on a quadrupole-orthogonal time-of-flight instrument with high sensitivity and without derivatization (Chai, W.; Piskarev, V.; Lawson, A. M. Anal. Chem. 2001, 73, 651–657). In contrast to oligonucleotides and peptides, oligosaccharides can form branched structures that result in a greater degree of structural complexity. In the present work we apply negative-ion electrospray CID MS/MS to core-branching pattern analysis using nine 3,6-branched and variously fucosylated oligosaccharides based on hexasaccharide backbones LNH/LNnH as examples. The important features of the method are the combined use of CID MS/MS of singly and doubly charged molecular ions of underivatized oligosaccharides to deduce the branching pattern and to assign the structural details of each of the 3- and 6-branches. These spectra give complimentary structural information. In the spectra of [M -H]−, fragment ions from the 6-linked branch are dominant and those from the 3-linked branch are absent, while fragment ions from both branches occur in the spectra of [M - 2H]2−. This allows the distinction of fragment ions derived from either the 3- or 6-branches. In addition, a unique D2β-3 ion, arising from double D-type cleavage at the 3-linked glycosidic bond of the branched Gal core residue, provides direct evidence of the branching pattern with sequence and partial linkage information being derived from C- and A-type fragmentations, respectively.
KeywordsOligosaccharide GlcNAc Fucose Collision Induce Dissociation Collision Induce Dissociation Spectrum
- 1.Gottschalk, A. The Influenza Virus Enzyme and Its Mucoprotein Substrate. Yale J. Biol. Med. 1954, 26, 352–364.Google Scholar
- 2.Watkins, W. M. Blood-Group Specific Substances. In Glycoproteins: Their composition, Structure and Function; Gottschalk, A., Ed.; Elsevier: Amsterdam, 1972; pp 830–899.Google Scholar
- 3.Kabat, E. A. Contributions of Quantitative Immunochemistry to Knowledge of Blood Group A, B, H, Le, I and i Antigens. Am. J. Clin. Pathol. 1982, 78, 281–292.Google Scholar
- 6.DeFrees, S.; Kosch, W.; Way, W.; Paulson, J. C.; Sabesan, S.; Halcomb, R. L.; Huang, D. H.; Ichikawa, Y.; Wong, C. H. Ligand Recognition by E-Selectin—Synthesis, Inhibitory Activity, and Confirmational-Analysis of Bivalent Sialyl-Lewis-X Analogs. J. Am. Chem. Soc. 1995, 117, 66–79.CrossRefGoogle Scholar