Structure of polysaccharides

The objective of the project described is to obtain insight in the relation between the chemical fine-structure of polysaccharides from soy bean cell walls and their functional properties in industrial products and how they effect processing. Soy meal is of great importance in the feed industry. The application of the (modified) soy bean cell wall polysaccharides as a food additive will be investigated. The obtained knowledge of the polysaccharide structures will also be used in studies concerned with the improvement of the in vivo digestibility of these polysaccharides. 

Analytical work, alone, has educed much helpful information on the structure of polysaccharides.1104 Results in this field have come primarily... 

X-ray fiber diffraction can be used to visualize ordered structures of polysaccharides at atomic resolution. The structures provide information on structure/property relationships in these systems. X-ray fiber diffraction techniques are outlined and are illustrated with applications to typical polysaccharides. 

This article, which is the fourth in the current series,1 presents a bibliographic account of the crystal structures of polysaccharides that have been published during 1977-1979. Several comprehensive reviews on the structures of glycosaminoglycans,2-5 bacterial capsular polysaccharides,3 4,6 starch,7-9 and cell-wall polysaccharides,10 and on... 

Rees, D.A. and Welsh, E.J. (1977). Secondary and tertiary structure of polysaccharides in solution and gels. Angewandte Chemie—International Edition in English, 16, 214-224. 

Polysaccharides that have been modified chemically, or altered physically, have been used as adsorbents for affinity chromatography. The modification of the structure of polysaccharides has been achieved by introducing cross-linkages between the chains of the polymer and bifunctional reagents. The alteration of the properties of polysaccharides by physical means can be effected by embedding the polysaccharide in a network of the support material. The molecular in-... 

The elucidation of the structure of polysaccharides and of the carbohydrate portion of glycoconjugates involves sugar analysis, linkage analysis, and the determination of anomeric configurations and the sequences of the sugar residues. When non-sugar substituents are present, these should also be identified and located. 

In an earlier article1 on the application of enzymic techniques to the analysis of the structure of polysaccharides, the -d- and /3-D-glucans were discussed, as well as more-general aspects of the preparation and use of catabolic enzymes in such analyses. The present article describes enzymic contributions to knowledge of the structures of other polysaccharides, but an account of subsequent research on a- and jS-D-glucans is also included. 

The properties and action patterns of glycosidases and polysaccharide depolymerases have been reviewed,2 5 as also have the enzymes involved in biosynthetic pathways.6,7 An understanding of biosynthesis can provide insights into the structures of polysaccharides. Reviews concerning particular polysaccharides have appeared, and references to these will be given in relevant sections. 

Structure of Polysaccharide Chains, and Mechanisms of Their Assembly... 

The molecular structure of polysaccharides from Klebsiella serotype K8 has been examined by X-ray diffraction and computer-aided molecular modeling. The most favorable molecular model was not the one which had the maximum number of intra-molecular hydrogen bonds. This result suggests that in the analysis one should not a priori choose the molecular model which has the largest number of intra-molecular hydrogen bonds. 

Organic-chemical studies cannot determine completely the structure of polysaccharides, as such methods can only account for about 95% of the linkages present. In many instances there is evidence that labile bonds exist, and the presence of these can only be determined from kinetic studies of the rates of hydrolysis of the polysaccharide under different conditions. The establishment of the presence or absence of such labile linkages should form an important preliminary in the study of the polysaccharides, especially as the breakdown occurring during isolation may be of this nature. 

Lipids and proteins that are part of cell membranes often are bonded to small polysaccharide groups that project from the surface of the cell. Slight differences in the structures of polysaccharides that are bonded to lipids in red blood cell membranes of humans are responsible for the A, B, and O blood types. Antibodies recognize these groups and cause cells to clump when their surface groups are not the same as those on the cells of the original individual. 

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