Polysaccharides structural features

Polysaccharide Structural features Source and properties Applications... 

What structural features allow biological polymers to be informational macromolecnles Is it possible for polysaccharides to be informational macromolecnles ... 

In 1967, Heidelberger, Stacey et al. reported the purification, some structural features, and the chemical modification of the capsular polysaccharide from Pneumococcus Type I. Difficulties of direct hydrolysis of the polysaccharide were overcome and it was possible to identify some of the fragments in the hy-drolyzate. At least six products resulted from nitrous acid deamination. Two were disaccharides, which were identified, and sequences of linked sugar units were proposed. As modification of the polysaccharide decreased the amounts of antibody precipitated by anti-pneumococcal Type I sera, the importance of the unmodified structural features in contributing to the specificity of the polysaccharide was indicated. 

This class of polysaccharide was well known in sugar refineries as the causative agent of ropiness it was formed from cane or beet sugar by bacteria of the Leuconostoc genus. Over many years, numerous papers were published, mainly with E. J. Bourne [Adv. Carbohydr. Chem. Biochem., 34 (1977) 1-22] and S. A. Barker as co-authors, describing the isolation, purification, properties, and structural features of dextrans. 

Within the scope of this review, the contributions of the last decade concerning cell-wall polysaccharides isolated from woody and other plant tissues will be reviewed according to the above-proposed classification of hemicelluloses including larch arabinogalactans. The present review article updates and extends previous reviews [3-5] and will focus in particular on new investigated plant sources, isolation methods, structural features, physicochemical and various functional properties of hemicelluloses. Attention will also be paid to the modification of isolated hemicelluloses or hemicellulosic materials and the appHcation possibiUties of hemicelluloses and their derivatives, including their use for the production of composite materials and other biomaterials. 

The rheological behavior of storage XGs was characterized by steady and dynamic shear rheometry [104,266]. Tamarind seed XG [266] showed a marked dependence of zero-shear viscosity on concentration in the semi-dilute region, which was similar to that of other stiff neutral polysaccharides, and ascribed to hyper-entanglements. In a later paper [292], the flow properties of XGs from different plant species, namely, suspension-cultured tobacco cells, apple pomace, and tamarind seed, were compared. The three XGs differed in composition and structural features (as mentioned in the former section) and... 

Ginsenan S-IIA, a polysaccharide fraction from the roots of P. ginseng is a potent inducer of IL-8 production by human monocytes and THP-1 cells, and this induction is accompanied by increased IL-8 mRNA expression. The polysaccharide appears from the structural feature to be a mixture of arabino-galactan type I and type II, based on the presence of 1,3-, 1,6-, 1,3,6-, 1,4-, and 1,4,6-galactose units as well as terminal arabinose and 1,5-, 1,3,5-, and 1,2,5-linked units. It also contains 1,4,6-linked glucose units that together with the 1,2,5-linked arabinose units are different from the units found in other ginseng polysaccharides and may thus be of importance for the activity [64]. 

Bio activities found for some of the polysaccharides described in this chapter have been assigned to certain structural features. The antioxidant effect of the Cuscuta chinensis pectin was proposed to be caused by the presence of a glucobiose unit linked via a GalA unit on the RG-I polymer [53], but this structural feature was not found for the anti-oxidant polysaccharide from Tinospora cordifolia [78,79]. 

In some polysaccharides, the reducing terminal is linked, through a phosphoric diester linkage, to O-1 of a 2,3-di-6 -acylglycerol. This structural feature has been demonstrated for some capsular polysaccharides from E. coli and Neisseria species, - but is probably more common than that. Non-covalent linkage between the lipid part and the cell membrane may explain why extracellular polysaccharides often occur as capsules, and the high (apparent) molecular weight observed for these polysaccharides may be due to micelle formation in aqueous solution. 

Figure 48-9. Structure of heparin. The polymer section illustrates structural features typical of heparin however, the sequence of variously substituted repeating disaccharide units has been arbitrarily selected. In addition, non-O-sulfated or 3-0-sulfated glucosamine residues may also occur. (Modified, redrawn, and reproduced, with permission, from Lindahl U et al Structure and biosynthesis of heparin-like polysaccharides. Fed Proc 1977 36 19.)...

Tomoda, M., Suzuki, Y., and Satoh, N. (1979) Plant mucilages. XXIII. Partial hydrolysis of Abelmoschus-mucilage M and the structural features of its polysaccharide moiety. Chem.Pharm.Bull. 27 1651-1656. 

The structural features of ceU wall polysaccharides of carrots have been studied by Stevens and Selvendran (1984) and Massiot et al.(1988). Plat et al.(1991), Ben Shalom et al.(1992) and Massiot et al.(1992) investigated the changes in pectic substances of carrots after blanching, dehydration and extended heat treatment. Data on the changes in ceU waU polysaccharides of canned carrots are lacking. This study aims to investigate the effect of preheating time at low temperature and the addition of CaCL on texture and on the composition of various pectin fractions of carrots canned by conventional and by a new process. 

This paper reports the structural features of the silk floss polysaccharide and the partial structure of a viscous acidic polymer obtained from the seeds of Chorisia speciosa. It was of interest to analyze these polysaccarides due to the relationship of Bombacaceae to Sterculiaceae, as well as for its possible commercial uses. 

Structural features of pectic polysaccharides of red beet Beta vulgaris conditiva)... 

To date, the structural features of pectic polysaccharides and plant cell walls have been studied extensively using chemical analysis and enzymatic degradation. In addition, research on isolation and physicochemical characterisation of pectin from citrus peels, apple peels, sunflower head residues and sugar beet pulp has been reported (2). However, the pectic polysaccharides extracted from wheat straw have only previously been reported by Przeszlakowska (3). The author extracted 0.44% pectic substances from Author to whom correspondence should be addressed. 

Because the only general review13 on these compounds in this Series dates back to 1946, it seems pertinent to recall the main structural features of these polysaccharides. (For extensive discussions on the structure and the physicochemical and biological properties of GAG, see Refs. 8,10, and 13-18.)... 

NMR can also be used to elucidate the structural features of a repeating unit in a polysaccharide and to investigate the conformation and dynamics of polysaccharides.21 A unique polysaccharide structure results in a characteristic proton NMR spectrum. Therefore, NMR is a powerful tool for identifying polysaccharide structures. This remarkable specificity has led to the development of a routine NMR-based identity assay, recently reported by Abeygunawardana et al. for quality control testing of bacterial polysaccharide to be used in formulating a polyvalent pneumococcal polysaccharide vaccine.22... 

It should be emphasized that although many structural features of the various polysaccharides are known, in general these polysaccharides are by no means completely characterized. However, with extensive C-13 n.m.r. chemical shift and intensity data, it is possible to employ these reference spectra to further characterize the compounds under consideration. 

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