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Polysaccharide Structure (polysaccharide + structure)
Selected AbstractsDIFFERENCES IN POLYSACCHARIDE STRUCTURE BETWEEN CALCIFIED AND UNCALCIFIED SEGMENTS IN THE CORALLINE CALLIARTHRON CHEILOSPORIOIDES (CORALLINALES, RHODOPHYTA),JOURNAL OF PHYCOLOGY, Issue 3 2010Patrick T. Martone The articulated coralline Calliarthron cheilosporioides Manza produces segmented fronds composed of calcified segments (intergenicula) separated by uncalcified joints (genicula), which allow fronds to bend and reorient under breaking waves in the wave-swept intertidal zone. Genicula are formed when calcified cells decalcify and restructure to create flexible tissue. The present study has identified important differences in the main agaran disaccharidic repeating units [,3)-,- d -Galp (1, 4)-,- l -Galp(1,] synthesized by genicular and intergenicular segments. Based on chemical and spectroscopical analyses, we report that genicular cells from C. cheilosporioides biosynthesize a highly methoxylated galactan at C-6 position with low levels of branching with xylose side stubs on C-6 of the [,3)-,- d -Galp (1,] units, whereas intergenicular segments produce xylogalactans with high levels of xylose and low levels of 6- O -methyl ,- d -Gal units. These data suggest that, during genicular development, xylosyl branched, 3-linked ,- d -Galp units present in the xylogalactan backbones from intergenicular walls are mostly replaced by 6- O -methyl -d- galactose units. We speculate that this structural shift is a consequence of a putative and specific methoxyl transferase that blocks the xylosylation on C-6 of the 3-linked ,- d -Galp units. Changes in galactan substitutions may contribute to the distinct mechanical properties of genicula and may lend insight into the calcification process in coralline algae. [source] The identity of the O-specific polysaccharide structure of Citrobacter strains from serogroups O2, O20 and O25 and immunochemical characterisation of C. youngae PCM 1507 (O2a,1b) and related strainsFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 1-2 2003gorzata Miesza Abstract Serological studies using SDS,PAGE and immunoblotting revealed that from five strains that are ascribed to Citrobacter serogroup O2, four strains, PCM 1494, PCM 1495, PCM 1496 and PCM 1507, are reactive with specific anti- Citrobacter O2 serum. In contrast, strain PCM 1573 did not react with anti- Citrobacter O2 serum and, hence, does not belong to serogroup O2. The LPS of Citrobacter youngae O2a,1b (strain PCM 1507) was degraded under mild acidic conditions and the O-specific polysaccharide (OPS) released was isolated by gel chromatography. Sugar and methylation analyses along with 1H- and 13C-NMR spectroscopy, including two-dimensional 1H,1H COSY, TOCSY, NOESY and 1H,13C HSQC experiments, showed that the repeating unit of the OPS has the following structure: NMR spectroscopic studies demonstrated that Citrobacter werkmanii O20 and C. youngae O25 have the same OPS structure as C. youngae O2. Sugar and methylation analyses of the core oligosaccharide fractions demonstrated structural differences in the lipopolysaccharide core regions of these strains, which may substantiate their classification in different serogroups. [source] Review: Condensed tannin and grape cell wall interactions and their impact on tannin extractability into wineAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 1 2010R.L. HANLIN Abstract It has been suggested that tannin extraction from grape berries into wine is limited by tannin binding to cell walls. Here we review the current state of knowledge and identify gaps in research that would enable characterisation of these interactions. Such characterisation could improve tannin extraction management in winemaking. The work identified in this review supports the hypothesis that tannin,cell wall interactions are formed by hydrogen bonding and hydrophobic interactions with the binding capacity of the cell walls influenced by tannin and polysaccharide structure and composition. Cell wall changes during berry development may increase the tannin-binding capacity of cell walls, while tannin structure may also influence its affinity for cell wall material. This review also identifies the need to investigate cultural and environmental factors that affect tannin and polysaccharide composition, to characterise the tannin-binding capacity of cell walls and to develop methods for assessing tannin-binding capacity of fruit prior to harvest. It is envisaged that a detailed understanding of tannin interactions with other components in the grape would lead to a predictive model for extractability of condensed tannins into wine. [source] Pectin-Derived Porous MaterialsCHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2010Robin Abstract Porous forms of pectin, a major industrial waste biomass polysaccharide, have been prepared by aqueous phase expansion routes (SBET>200,m2,g,1; Vpore>0.80,cm3,g,1). It was demonstrated that the aqueous phase acidity crucially influenced the properties of the porous pectin form. Preparation route selection allows direction of material textural and morphological properties, thought to be the result of polysaccharide configuration, and methyl ester group hydrolysis, believed to alter the lowest energy accessible metastable polysaccharide state during gel recrystallisation. The resulting low density amorphous powders or mouldable monoliths (,powder ,0.20,g,cm,3/,monolith ,0.07,g,cm,3) can be directly transformed by thermal carbonisation into low density mesoporous carbonaceous materials (e.g. , ,0.27,g,cm,3 (Tp=550,°C)), which possess textural and nanoscale material morphology reflective of the porous pectin precursor employed. Acidic gelation promotes methyl ester groups hydrolysis of the polysaccharide structure, generating carbons with unusual interdigitated rod-like nanoscale morphology. Importantly, the materials presented herein are produced directly from the parent porous pectin material, without the need for additive catalyst (or template) to yield highly mesoporous products (e.g. Vmeso,0.45,cm3,g,1; polydispersity (PD)>10,nm), with accessible tuneable functionally rich surfaces. Due to the high mesoporosity (>85,%), materials have potential application in chromatography, heterogeneous catalysis and large molecule adsorption strategies. [source] Structure of the O-polysaccharide from Proteus myxofaciensFEBS JOURNAL, Issue 15 2003Classification of the bacterium into a new Proteus O-serogroup The O-polysaccharide (O-antigen) was obtained from the lipopolysaccharide of Proteus myxofaciens, a Proteus strain producing copious amounts of slime, which was isolated from the gypsy moth larvae. The structure of the polysaccharide was studied by chemical analysis and 1H and 13C NMR spectroscopy, including 2D COSY, TOCSY, ROESY and H-detected 1H,13C HMQC experiments. It was found that the polysaccharide contains an amide of glucuronic acid (GlcA) with an unusual ,-linked amino acid, N, -[(R)-1-carboxyethyl]- l -lysine (2S,8R -alaninolysine, 2S,8R -AlaLys), and has a linear tetrasaccharide repeating unit of the following structure: This structure is unique among known bacterial polysaccharide structures. On the basis of these and serological data, it is proposed that P. myxofaciens be classified into a new Proteus serogroup, O60, of which this strain is the single representative. Structural and serological relatedness of P. myxofaciens to other AlaLys-containing O-antigens of Proteus and Providencia is discussed. [source] Composition and properties of biologically active pectic polysaccharides from leek (Allium porrum)JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 12 2010Maria Kratchanova Abstract BACKGROUND: Leek (Allium porrum) is very commonly used vegetable in Bulgaria and is distinctive with high content of bioactive components1. Previously2 we obtained five crude pectic polysaccharides from leek through consecutive extraction. Some of them appeared to be good stimulators of the immune system. Schols and Voragen3 investigated the composition of modified hairy regions of pectic polysaccharides isolated from leek cell walls. Samuelson et al.4 identified the polysaccharide structures encountered in hairy regions as bioactive. The aim of this work was to study the isolation, composition and biological activities of pectic polysaccharides from leek. RESULTS: Two pectic polysaccharides from leek were isolated through consecutive water and acid extraction. The water extractable pectin had higher polyuronic content, higher protein content and lower neutral sugar content. It was found that next to galacturonic acid they also contain glucuronic acid in ratio 9:1 for the water- and 3:1 for the acid-extractable polysaccharide. The main neutral sugar was galactose. The water-extractable pectic polysaccharide had higher molecular weight (106 Da) and homogeneity. It was shown that the pectic polysaccharides from leek have considerable immunostimulating activities. CONCLUSION: Leek polysaccharides have relatively high galacturonic and glucuronic acid content and are distinguished with high biological activity. 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