title: Synthesis and immunological properties of a tetrasaccharide portion of the B side chain of rhamnogalacturonan II (RG-II).
abstract: A highly convergent strategy was used for the synthesis of a tetrasaccharide [3-aminopropyl beta-L-arabinofuranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->3)]-alpha-L-arabinopyranoside] portion of the B side chain of the plant cell-wall pectic polysaccharide rhamnogalacturonan II (RG-II). The terminal nonreducing beta-L-arabinofuranosyl residue of the target compound was installed by using an arabinofuranosyl donor that was protected with a 3,5-O-(di-tert-butylsilane) group to facilitate nucleophilic attack from the beta-face. The synthetic strategy also employed a chemoselective glycosylation of a trichloroacetimidate donor with a thioglycosyl acceptor; this gave a product that could be used immediately in a subsequent glycosylation. The reducing end of the tetrasaccharide contained an aminopropyl group to facilitate conjugation to keyhole limpet hemocyanin (KLH) and bovine serum albumin (BSA). Mice that were immunized with a KLH-tetrasaccharide conjugate produced antibodies that recognized RG-II isolated from Arabidopsis thaliana cell walls, but did not recognize RG-II obtained from red wine. Our data suggest that the arabinopyranosyl residue exists in the (4)C(1) conformation in the tetrasaccharide and in A. thaliana RG-II, whereas it has the (1)C(4) conformation in wine RG-II. It is proposed that differences in the conformation of side chain B might account for the ability of antibodies to discriminate between RG-II that was isolated from Arabidopsis and wine.
authors.affiliation: Complex Carbohydrate Research Center, The University of Georgia, 315 Riverbend Road, Athens, GA 30602, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Rao
authors.forename: Therese
authors.initials: T
authors.lastname: Buskas
authors.forename: Anathea
authors.initials: A
authors.lastname: Albert
authors.forename: Malcolm A
authors.initials: MA
authors.lastname: O'Neill
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hahn
authors.forename: Geert-Jan
authors.initials: GJ
authors.lastname: Boons
mesh_terms: D000818:Animals; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D051379:Mice; D019906:Nuclear Magnetic Resonance, Biomolecular; D009844:Oligosaccharides / Q000737:chemistry*; D010368:Pectins / Q000138:chemical synthesis* / Q000737:chemistry / Q000276:immunology*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000939:Epitopes; D009844:Oligosaccharides; C042492:rhamnogalacturonan II; D010368:Pectins