Lars-Erik Franzén

Structural elucidation, using h.p.l.c.-m.s. and g.l.c.-m.s., of the acidic polysaccharide secreted by rhizobium meliloti strain 1021

Abstract An improved, glycosyl-sequencing method has been used for elucidating the structure of the acidic polysaccharide secreted by Rhizobium meliloti strain 1021. The polysaccharide was methylated, the ether partially hydrolysed, the products were reduced, and the alditols ethylated; the resulting mixture of peralkylated oligosaccharide-alditols was analyzed by h.p.l.c.-m.s. Chemical ionization (c.i.) mass spectra were obtained at 2-s intervals, as the various, peralkylated oligosaccharide-alditols were eluted from the h.p.l.c. column. Peralkylated mono-, di-, tri-, and tetra-saccharide-alditols could be readily detected, and at least partially identified, by their M + I ions, in conjunction with other characteristic ions present in their c.i.-mass spectra. The peralkylated di- and tri-saccharide-alditols were further analyzed by g.l.c.-m.s. in the electron-impact mode. The structure of the acidic polysaccharide secreted by R. meliloti strain 1021 is the same as that of the previously characterized polysaccharide secreted by R. meliloti strain U-27.

[1] Structural analysis of complex carbohydrates using high-performance liquid chromatography, gas chromatography, and mass spectrometry

Publisher Summary This chapter discusses the structural analysis of complex carbohydrates using high-performance liquid chromatography, gas chromatography, and mass spectrometry. The primary structure of a complex carbohydrate is known only when all of the following characteristics have been elucidated: (1) the glycosyl residue composition—that is, the identity and the ratio of the monosaccharides that are glycosidically linked to each other within the complex carbohydrate, (2) the absolute configuration, D or L, of each glycosyl residue, (3) the glycosyl linkage composition—that is, the carbon atoms of each glycosyl residue to which other glycosyl residues are glycosidically linked, (4) the ring form, pyranose or furanose, of each glycosyl residue, (5) the sequence of the glycosyl residues, (3) the anomeric configuration of the glycosidic linkage of each glycosyl residue, and (7) the identity, points of attachment, and stereochemistry, if appropriate, of any noncarbohydrate moieties.

Structure and function of complex carbohydrates active in regulating plant-microbe interactions

A key regulatory role of complex carbohydrates in the interactions between plants and microbes has been estab— lished. The complex carbohydrates act as regulatory mole— cules or hormones in that the carbohydrates induce de novo protein synthesis in receptive cells. [11 The first complex carbohydrate recognized to possess such regulatory proper— ties is a polysaccharide (PS) present in the walls of fungi (2). Hormonal concentrations of this PS elicit plant cells to accumulate phytoalexins (antibiotics). [2] More recently we have recognized that a PS in the walls of growing plant cells also elicits phytoalexin accumulation; microbes and viruses may cause the release of active fragments of this endogenous elicitor. [3] Another PS in plant cell walls is the Proteinase Inhibitor Inducing Factor (PIIF) (53). This hormone appears to protect plants by inducing synthesis in plants of proteins which specifically inhibit digestive enzymes of insects and bacteria. [4] Glycoproteins secreted by incompatible races (races that do not infect the plant) of a fungal pathogen of soybeans protect seedlings from attack by compatible races. Glycoproteins from compatible races do not protect the seedlings (61). [5] The acidic PS secreted by the nitrogen—fixing rhizobia appear to function in the infection of legumes by the rhizobia. W.D. Bauer and his co—workers have evidence that these PS are required for the development of root hairs capable of being infected by symbiont rhizobia. Current knowledge of the structures of these biologically active complex carbohydrates will be presented.

Structural investigation of the acidic polysaccharide secreted by Zoogloea ramigera 115

Abstract Batch-culture growth of Zoogloea ramigera 115 in a defined medium produced a weakly acidic polysaccharide containing glucose and galactose residues, and ( S )-pyruvic acetal groups. Analytical results indicated that the polysaccharide does not have a simple repeating-unit. Mainly with the aid of Smith degradation of the native polysaccharide and oxidation and subsequent β-elimination of the methylated and then depyruvylated polysaccharide, some structural features of the polysaccharide were identified.

The structure of the acidic polysaccharide secreted by Klebsiella aerogenes type 54 strain A3

Abstract The polysaccharide secreted by Klebsiella aerogenes type 54 strain A3 was isolated, methylated, the ester carboxyl-reduced, and the product partially hydrolyzed. The resulting, partially O -methylated oligosaccharides were reduced and ethylated, and the mixture of products was fractionated by l.c. The l.c. fractions containing per- O -alkylated oligosaccharide-alditols were analyzed by e.i.-m.s. Pure per- O -alkylated oligosaccharide-alditols were also analyzed by 1 H-n.m.r. spectroscopy. The products obtained by base-catalyzed degradation and subsequent ethylation of the per- O -methylated polysaccharide were fractionated by l.c. The main product isolated was analyzed by e.i.-m.s., c.i.-m.s., and 1 H-n.m.r. spectroscopy. The results of these studies, in conjunction with results of analytical methods commonly used in the elucidation of polysaccharide structures, unambiguously characterized the primary glycosyl structure of the polysaccharide. Base-labile substituents, previously reported to be present in the polysaccharide, were not studied. Structure 1 revises, and complements, previously reported structures.