In structural analysis of polysaccharides

Anhydrous hydrogen fluoride, application of for the structural analysis of polysaccharides, 47, 167-202 Anomeric and exo-anomeric effects in carbohydrate chemistry, 47, 45-123 Anomeric-oxygen activation for glycoside synthesis, trichloroacetimidate method, 50,21-123... 

How modeling has been useful in the crystal structure analysis of polysaccharides—and how it could lead to a better understanding of other condensed j)hase states—can be illustrated with structural worK done on cellulose. It is one of the world s most important and widely used raw materials whose structure, properties, derivatives, and transformations remain under continuous study. Some of the results, problems, and indications of future directions resulting from the study of its crystalline structure—and the attendant roles for molecular modeling—are briefly described in the following. 

A new potential in polysaccharide immunochemistry is provided by homogeneous immunoglobulins that bind carbohydrate polymers. Here, the specific immunoglobulin-hapten interaction can be studied, and characterized in detail. Thus, the discipline of carbohydrate chemistry can make a real contribution to the elucidation of the structure of immunoglobulins. In return, carbohydrate chemistry may find a tool that can increasingly be applied to the unraveling of its own unsolved problems in the structural analysis of polysaccharides. 

The difficulties attendant on the isolation of pure enzymes of known specificity is a major barrier to their routine use for the structural analysis of polysaccharides. As the specificities are separated and as the action patterns of carbohydrases become better defined, these enzymes may be expected to play an important and vital role in the investigation of the structure of synthetic polysaccharides containing ordered sequences of sugar residues. Conversely, it may be anticipated that synthetic carbohydrate polymers of known structure will aid in studies of the specificity requirements of purified enzymes. 

Anhydrous hydrogen fluoride has been successfully applied in the structural analysis of polysaccharides to cleave glycosidic linkages since the 1980s. Recently, triflic acid has been found to be a more potent and more selective agent.774 In structural studies, for example, polysaccharides isolated from bacteria were stable toward... 

Although various procedures are available for the model analysis of fibrous polymers, methods based on the virtual bond representation of the asymmetric residue may be of advantage in many cases. In the following, we describe one such method that began with simple procedures applied to polysaccharides, but has now been refined into a flexible and powerful model analysis tool that is simple to use with any class of polymer. Its use in the present case, however, is illustrated with examples drawn from the structure analysis of polysaccharides. 

Methylation- or combined methylation-ethylation reactions were used for structure analysis of polysaccharides. The alkylation of dextran can be applied to the investigation of the branching pattern, i.e. the number and length of side chains (Sect. 2.2) [22,23]. The methylation is carried out in liquid ammonia with sodium iodide and methyl iodide, yielding products that are soluble in chloroform and tetrachloroethane [257]. 

The present article summarizes the data on application of hydrogen fluoride for structural analysis of polysaccharides, primarily those of bacterial origin. Some regularities in the stability of glycosidic linkages of different monosaccharides, and the mechanism of interaction between hydrogen fluoride and carbohydrates, are briefly discussed. The experimental technique for carrying out solvolysis is also described. 

The structural analysis of polysaccharides involved in biofilm formation of S. epidermidis has been hampered repeatedly by difficulties with the specific identification and purification of the molecules involved in biofilm formation. Not infrequently, components from the media used to grow the bacteria have been purified and analyzed leading to erroneous conclusions [41, 87] for a review see also [88], A significant step forward in the purification and elucidation of composition and structure of the functionally important polysaccharides was the isolation of isogenic biofilm-negative transposon... 

A most useful application of methylation is for the structural analysis of polysaccharides. Permethylation, followed by hydrolysis of the product and identification of the individual methylated monosaccharides, indicates the original positions of the linkage points, as these are denoted by hydroxyl groups in the methylated monosaccharides. Considerable work has been done on the separation and identification of methylated monosaccharides by gas-liquid chromatography and mass spectrometry this topic is treated in detail in this Volume by Lbnngren and Svensson (see p. 41), Clearly, for such structural analyses to be valid, complete methyl-... 

Four enzjnnic methods that have been of use in the analysis of polysaccharide structure are considered here. 

The enzymic analysis of the structures of the amylaceous polysaccharides illustrates the applications of an enzyme which has been one of the most widely used in polysaccharide structural analysis, namely, beta-amylase. The availability of pure, crystalline preparations of this enz)une heralded the beginning of a new era in the structural analysis of polysaccharides which, as evidenced by new work in the field (for a review, see Ref. 12), is still gathering momentum. 

The uses of enzymes in the structural analysis of polysaccharides have been reviewed. ... 

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