title: A chemical synthesis of a multiply13C-labeled hexasaccharide: a high-mannose N-glycan fragment.
abstract: As covalent modifiers of proteins, high-mannose N-glycans are important in maintaining protein structure and function in vivo. The conformations of these glycans can be studied by nuclear magnetic resonance spectroscopy using spin-spin couplings (J-couplings; scalar couplings) and other nuclear magnetic resonance parameters that are sensitive to the geometries of their constituent glycosidic linkages and other mobile elements in their structures. These analyses often require13C-labeling at specific carbon atoms, especially when measurements of13C-13C J-couplings are of interest. The selection of particular13C isotopomers of a glycan depends on the type of question under scrutiny. A chemical synthesis of a mannose-containing hexasaccharide, α[1-13C]Man(1→2)α[1,2-13C2]Man(1→6)[α[1-13C]Man(1→2)α[1,2-13C2]Man(1→3)]α[1,2-13C2]Man(1→6)βManOCH3, which is a nested fragment of the high-mannose N-glycans of human glycoproteins and contains eight13C-enriched carbon sites, is described in this report. The selected13C isotopomer was chosen to maximize the measurement of J-couplings sensitive to linkage conformations. This work demonstrates that chemical syntheses of multiply13C-labeled oligosaccharides are technically feasible and practical using present synthetic methods. The availability of this and other multiply13C-labeled mannose-containing oligosaccharides will promote future studies of their conformations in solution and in the bound state.
authors.affiliation: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA.
authors.forename: Wenhui
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Omicron Biochemicals, Inc., South Bend, IN, USA.
authors.forename: Qingfeng
authors.initials: Q
authors.lastname: Pan
authors.affiliation: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA.|Omicron Biochemicals, Inc., South Bend, IN, USA.
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Serianni
mesh_terms: D002247:Carbon Isotopes / Q000737:chemistry*; D060326:Chemistry Techniques, Synthetic; D007553:Isotope Labeling; D008358:Mannose / Q000737:chemistry*; D011134:Polysaccharides / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D011134:Polysaccharides; D008358:Mannose
keywords: 13C-labeling; NMR; chemical synthesis; hexasaccharide; high-mannose N-glycan