A-1,6 glycosidic linkages

FIGURE 25 6 Molecu lar models of the disaccha rides maltose and cellobiose Two D glucopyranose units are connected by a glycoside linkage between C 1 and C 4 The glycosidic bond has the a orientation in maltose and IS p in cellobiose Mai tose and cellobiose are diastereomers... 

The small change in stereochemistry between cellulose and amylose creates a large difference in their overall shape and in their properties. Some of this difference can be seen in the strorcture of a short portion of fflnylose in Figure 25.9. The presence of the a-glycosidic linkages imparts a twist to the fflnylose chain. Where the main chain is roughly linear- in cellulose, it is helical in anylose. Attractive forces between chains are weaker in fflnylose, and fflnylose does not form the same kind of strong fibers that cellulose does. 

Figure 12.13 Glycosyl diacylglycerol structure. The carbohydrate, which may be either a monosaccharide or a disaccharide residue, is attached by a glycosidic linkage to the sn-3 position of glycerol.

Sialic acids occur in a-glycosidic linkage as components of oligosaccharides, polysaccharides, and glycoconjugates.19,41-44 As binding... 

It has D-glucose units joined by a-glycosidic linkages [Problem 22.35(a)] to the C of the next unit. This is revealed by isolating maltose, an a-glycoside, and the 2,3,6-tri-O-methyl derivative. The C —OH forms the pyranoside ring. 

Maltose is hydrolyzed by the enzyme maltase (specific for a-glycosidic linkage) to two units of glucose, but for the hydrolysis of cellobiose the enzyme emulsin (specific for (3-glycosidic linkage) is necessary. While maltose is the building block of the polysaccharide starch, cellobiose is the building block of another polysaccharide, cellulose. 

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