Carb-39. Polysaccharides

A general term for a polysaccharide (glycan) composed of a single type of monosaccharide residue is obtained by replacing the ending -ose of the sugar name by -an . 

Examples of established usage of the -an ending are xylan for polymers of xylose, mannan for polymers of mannose, and galactan for polymers of galactose. Cellulose and starch are both glucans, as they are composed of glucose residues. 

When the configurational series of the monomer residues is known, D- or L- may be included as a prefix to the name. 

This is a modified version of the 1980 recommendations on polysaccharide nomenclature 

When the linkage between monosaccharide units is non-glycosidic (as in the phosphate derivative shown below), use of the glycan terminology is inappropriate other methods of polymer nomenclature should be employed [20], 

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Polysaccharides composed of only one kind of monosaccharide are described as homopolysaccharides (homoglycans). Similarly, if two or more different kinds of monomeric unit are present, the class name heteropolysaccharide (heteroglycan) may be used. (See 2-Carb-39.)... 

Oligosaccharide and polysaccharide structures occur not only in free form but often as parts of glycopeptides or glycoproteins [11] or of glycolipids [21]. It can be cumbersome to designate their structures by using the recommendations of 2-Carb-37. The use of three-letter symbols for monosaccharide residues is therefore recommended. With appropriate locants and anomeric descriptors, long sequences can thus be adequately described in abbreviated form. 

Carb-39.7. Polysaccharides composed of more than one kind of residue... 

Paoletti, S., Cesaro, A., and Delben, F., Thermally induced conformational transition of xanthan polysaccharide, Carb. Res., 123, 173, 1983. 

The natural polymers frequently used for the preparation of pharmaceutical gels include tragacanth, pectin, carrageenan, agar, and alginic acid, as well as semisynthetic polysaccharides such as methylcellulose, hydroxymethylcellulose, and carb-oxymethylcellulose. 

Sandford P.A. "Exocellular, Microbial Polysaccharides" Adv. Carb. Chem. Biochem., 1979, 36, 297. 

Different materials used in the isolation procedure both the plant and the chemicals and the soluble will be different, therefore hemicellulose requires a different design of separation procedures. However, the presence of lignin and lignin-carbs relationship will affect the extraction of hemicellulose from the lygnocellulose cell wall matrix. The presence of hydrogen bonds between the individual components of the polysaccharides also inhibits the process of isolation. Therefore, the proper insulation process is required in order to separate it from the other components of polymers such as cellulose and lignin [9,16, 22, 26, 49, 50]. 

Binding acid groups to a polysaccharide (carb-oxymethyl, sulfate or phosphate groups) also results in increased solubihty and viscosity for reasons already outhned. Some derivatized polysaccharides, when moistened, have a pasty consistence. 

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