title: Glucuronoxylomannan of Cryptococcus neoformans serotype B: structural analysis by gas-liquid chromatography-mass spectrometry and 13C-nuclear magnetic resonance spectroscopy.
abstract: The major extracellular polysaccharide (glucuronoxylomannan, GXM) from six strains of Cryptococcus neoformans serotype B was characterized by gas-liquid chromatography (g.l.c.), g.l.c.-mass spectrometry (g.l.c.-m.s.), and nuclear magnetic resonance (n.m.r.) spectroscopy. Ultrasonic irradiation (u.i.) was used to reduce the mol.wt. of native GXM from 9.75 x 10(5) to 1.15 x 10(5) without apparent change in its composition (GXM-S). The Xylp:Manp:GlcpA molar ratio of the GXM and GXM-S from the six strains of C. neoformans serotype B is approximately 3.5:3.0:0.6. GXM-S was O-deacetylated (GXM-D) by treatment with NH4OH. The 13C-n.m.r. analysis of GXM-D gave spectra that served as characteristic fingerprints of the structure and also facilitated the assignment of the anomeric carbon resonances to specific structural moieties present in GXM-D. The GXM-D from each serotype B strain was found to be similar by 13C-n.m.r. spectroscopy. The structure contains a linear (1----3)-alpha-D-Manp backbone substituted with 2-O-beta-GlcpA and 2-O-beta-Xylp. beta-Xylp is also O-4 linked to the Manp substituted with GlcpA. In addition, a model for the disposition of the Xylp and GlcpA side chain substituents along the mannopyranan backbone is proposed, based upon results from the combination of g.l.c.-m.s. and 13C-n.m.r. spectroscopy.
authors.affiliation: Department of Chemistry, Georgia State University, Atlanta 30303.
authors.forename: S H
authors.initials: SH
authors.lastname: Turner
authors.forename: R
authors.initials: R
authors.lastname: Cherniak
mesh_terms: D002240:Carbohydrate Sequence; D002241:Carbohydrates / Q000032:analysis; D002247:Carbon Isotopes; D002849:Chromatography, Gas; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003455:Cryptococcus neoformans / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D008094:Lithium; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010084:Oxidation-Reduction; D011134:Polysaccharides; D011135:Polysaccharides, Bacterial / Q000737:chemistry*; D012703:Serotyping; D013010:Sonication
chemical_list: D002241:Carbohydrates; D002247:Carbon Isotopes; D011134:Polysaccharides; D011135:Polysaccharides, Bacterial; C027478:glucuronoxylomannan; D008094:Lithium