title: Differentiation of isomeric Lewis blood groups by positive ion electrospray tandem mass spectrometry.
abstract: Lewis histo-blood group antigens are one of the major classes of biologically active oligosaccharides. In this work, underivatized Lewis blood groups were studied by electrospray tandem mass spectrometry (ESI-MS(n)) in the positive mode with three different mass analyzers: Q-TOF (quadrupole time-of-flight), QqQ (triple quadrupole), and LIT (linear ion trap). It was observed that, under collision-induced fragmentations, type 1 Lewis antigens (Le(a) and Le(b)) could be distinguished from type 2 (Le(x) and Le(y)) on the basis of specific fragmentations of the GlcNAc unit. Whereas O-4-linked sugars of the GlcNAc are lost as residues, the O-3-linked sugars undergo fragmentation both as sugar units and as sugar residues (unit -18Da). Type 2 Lewis antigens also showed a characteristic cross-ring cleavage (0,2)A(2) of the GlcNAc. As a result, the product ions at m/z 388 and 305, characteristic of Le(x), and m/z 372, characteristic of Le(a), are proposed to distinguish the trisaccharide isomers Le(x)/Le(a). Also, the product ions at m/z 534 and 305, characteristic of Le(y), and m/z 372, characteristic of Le(b), are proposed to distinguish the tetrasaccharide isomers Le(b)/Le(y). These diagnostic fragment ions were further applied in the identification of Lewis type 2 antigens (Le(x) and Le(y)) in the lipopolysaccharide of the human gastric pathogen, Helicobacter pylori.
authors.affiliation: Departamento de Química, Universidade de Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: José A
authors.initials: JA
authors.lastname: Ferreira
authors.forename: M Rosário M
authors.initials: MR
authors.lastname: Domingues
authors.forename: Ana
authors.initials: A
authors.lastname: Reis
authors.forename: Mario A
authors.initials: MA
authors.lastname: Monteiro
authors.forename: Manuel A
authors.initials: MA
authors.lastname: Coimbra
mesh_terms: D000942:Antigens, Bacterial / Q000032:analysis; D016480:Helicobacter pylori / Q000276:immunology; D006801:Humans; D007536:Isomerism; D007983:Lewis Blood Group Antigens / Q000737:chemistry*; D009844:Oligosaccharides / Q000032:analysis / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods
chemical_list: D000942:Antigens, Bacterial; D007983:Lewis Blood Group Antigens; D009844:Oligosaccharides