Linkage 3-1,4-Linked polysaccharides

Alpha amylase diastase endohydrolysis, in a random manner, of (1—>4)-a-D-glu-cosidic linkages in polysaccharides containing three or more (l-+4)-a-D-linked D-glucosyl residues... 

D-xylose on hydrolysis with dilute nitric acid. Percival and Chanda7 isolated a xylan from the same plant. They found that the methylated xylan produced on hydrolysis 2-methyl-D-xylose, 2,3-dimethyl-D-xylose, 2,4-dimethyl-D-xylose and 2,3,4-trimethyl-D-xylose. From this and from the results of periodate oxidation, Percival and Chanda considered that the polysaccharide contains 1 — 3 and 1 —> 4 linkages with a non-reducing endgroup (yielding the 2,3,4-trimethyl-D-xylose) for every 20-21 D-xylose units. They considered that this xylan was not a mixture of 1 —> 3 and 1 —> 4 linked polysaccharides because careful fractionation of its diacetate and dimethyl ether failed to establish any polymer heterogeneity. Barry, Dillon, Hawkins and O Colla74 confirmed the conclusion of Percival and Chanda. 

The exo-anomeric effect enforces a value of cp around 90° for anomeric axial linkages. This ensures a proclivity towards helical structures (as distinct from the ribbons of 1,4-diequatorially linked polysaccharides), as in starch and glycogen. p-(1 4)-Linked galactans, 1,4 axial-equatorial in the other sense, are known as hemicellulose components of compression and tension wood, the storage polysaccharides of lupins and as arabinogalactans attached to the rhamnogalacturonan I component of pectin, but have not been subject to conformational studies they appear to be biosynthesised from UDP-Gal. " ... 

The relationship between glycosidic linkage conformation and C chemical shifts in the solid state for a number of (1 —> 4)-linked polysaccharide polymers and oligomers including CyDs was studied by the CP MAS method [78-80]. The CyD hydration process was investigated using C CP MAS spectra of anhydrous... 

Two different L-arabinans have been isolated from azuki beans (Phaseolus radiatus) by alkaline extraction and separated by gel chromatography. No other sugar residues were present and, from structural analysis, the polymers were composed of chains of 1,5-linked L-arabinofuranose residues with branch points at 0-2 and/or 0-3. These branches were composed of non-reducing terminal L-arabinofuranose residues and there were more (1 2)-linkages than (13)-linkages. The polysaccharides differed in their molecular weights and solubilities in aqueous ethanol. 

Cross-linking between polysaccharide-polysaccharide units can occur in different forms such as ester-linked hydroxycinnamate dimers (Ralph et al., 2004), ferulic acid and/orp-coumaric acid monomers as cyclic dimers (Grabber et al., 2004), and direct linkage between polysaccharides and xyloglucans (Harris and Stone, 2009). Some important interactions between lignin and polysaccharides in the cell walls are the following ... 

Branched structin-es, especially for a linked polysaccharides, enhance solubility Heterogeneity in types of repeating imits, backbone linkages, and polar or charged fimctionabty also imparts greater solubility. Excellent reviews of the effects of the structural conformation of monosaccharides are foimd in References 71 and 72. 

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