title: Mass + retention time = structure: a strategy for the analysis of N-glycans by carbon LC-ESI-MS and its application to fibrin N-glycans.
abstract: Analysis of the numerous possible, often isobaric structures of protein-bound oligosaccharides calls for a high-performance two-dimensional method that combines liquid chromatography's ability to separate isomers and mass spectrometry's ability to determine glycan composition. Here we investigate the usefulness of porous graphitic carbon columns coupled to ESI-MS for the separation of N-glycans with two or more sialic acids. Internal standards helped to rectify retention time fluctuations and thus allowed elution times to play an essential role in the structural assignment of peaks. For generation of a retention time library, standards representing the possible isomers of diantennary non-, mono-, and disialylated N-glycans, differing in the linkage of galactose and sialic acids as well as isobaric hybrid-type N-glycans, were produced using recombinant glycosyltransferases. Once the retention times library was established, isomers could be identified by LC-ESI-MS in the positive mode without additional MS/MS experiments. The method was applied for the detailed structural analysis of fibrin(ogen) N-glycans from various species (human, cow, pig, mouse, rat, cat, dog, Chinese hamster, horse, sheep, and chicken). All fibrins contained diantennary N-glycans. They differed in the occurrence of beta1,3-linked galactose, alpha2,3-linked sialic acids, and N-glycolylneuraminic acid, in the mono/diantennary glycan ratio, and in the O-acetylation of neuraminic acids. The separation system's potential for analyzing tri- and tetrasialylated N-glycans was demonstrated.
authors.affiliation: Biochemistry Division, Department of Chemistry, University of Natural Resources and Applied Life Sciences (BOKU), Muthgasse 18, 1190 Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Pabst
authors.forename: Jayakumar Singh
authors.initials: JS
authors.lastname: Bondili
authors.forename: Johannes
authors.initials: J
authors.lastname: Stadlmann
authors.forename: Lukas
authors.initials: L
authors.lastname: Mach
authors.forename: Friedrich
authors.initials: F
authors.lastname: Altmann
mesh_terms: D000107:Acetylation; D000818:Animals; D002240:Carbohydrate Sequence; D002244:Carbon / Q000737:chemistry*; D002853:Chromatography, Liquid / Q000379:methods*; D005337:Fibrin / Q000031:analogs & derivatives / Q000032:analysis*; D005690:Galactose / Q000737:chemistry; D016695:Glycosyltransferases / Q000378:metabolism; D006801:Humans; D007536:Isomerism; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000032:analysis*; D012794:Sialic Acids / Q000737:chemistry; D013045:Species Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D013997:Time Factors; D014168:Transferrin / Q000032:analysis
chemical_list: D011134:Polysaccharides; D012794:Sialic Acids; D014168:Transferrin; D002244:Carbon; D005337:Fibrin; D016695:Glycosyltransferases; D005690:Galactose