title: NMR characterization of endogenously O-acetylated oligosaccharides isolated from tomato (Lycopersicon esculentum) xyloglucan.
abstract: Eight oligosaccharide subunits, generated by endoglucanase treatment of the plant polysaccharide xyloglucan isolated from the culture filtrate of suspension-cultured tomato (Lycopersicon esculentum) cells, were structurally characterized by NMR spectroscopy. These oligosaccharides, which contain up to three endogenous O-acetyl substituents, consist of a cellotetraose core with alpha-D-Xylp residues at O-6 of the two beta-D-Glcp residues at the non-reducing end of the core. Some of the alpha-D-Xylp residues themselves bear either an alpha-L-Arap or a beta-D-Galp residue at O-2. O-Acetyl substituents are located at O-6 of the unbranched (internal) beta-D-Glcp residue, O-6 of the terminal beta-D-Galp residue, and/or at O-5 of the terminal alpha-L-Arap residue. Structural assignments were facilitated by long-range scalar coupling interactions observed in the high-resolution gCOSY spectra of the oligosaccharides. The presence of five-bond scalar coupling constants in the gCOSY spectra provides a direct method of assigning O-acetylation sites, which may prove generally useful in the analysis of O-acylated glycans. Spectral assignment of these endogenously O-acetylated oligosaccharides makes it possible to deduce correlations between their structural features and the chemical shifts of diagnostic resonances in their NMR spectra.
authors.affiliation: Complex Carbohydrate Research Center and Department of Biochemistry and Molecular Biology, University of Georgia, 315 Riverbend Road, Athens, GA 30602-4712, USA.
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Jia
authors.forename: Michael
authors.initials: M
authors.lastname: Cash
authors.forename: Alan G
authors.initials: AG
authors.lastname: Darvill
authors.forename: William S
authors.initials: WS
authors.lastname: York
mesh_terms: D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D005936:Glucans / Q000737:chemistry*; D018551:Solanum lycopersicum / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013053:Spectrophotometry
chemical_list: D005936:Glucans; D009844:Oligosaccharides; D011134:Polysaccharides