Monosaccharides glycans

Natural monosaccharide target Unnaiial monosaccharide Glycan types labeled HO OH AcO OAc... 

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 . 

Note. 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],... 

Some yeasts are able to add other monosaccharides, like galactose (S. pombe), but with unusual bonds [70], and they also tend to phosphorylate their glycans everywhere to obtain an additional charge on proteins [71]. 

A congener of the GPI membrane anchor, present on the cell surface of the malaria pathogen Plasmodium falciparum 127, was also tackled. The molecule is composed of one inositol moiety (I) and four monosaccharide units (II-V) [80]. The retrosynth-esis identified a single NPOE retron 108 as the precursor for all glycan units (Scheme 5.28). Transformations of the latter afforded NPOE analogs 128, 89,... 

The high sensitivity and reproducibility of currently used instruments also allows to directly monitor the binding of small ligands, i.e. disaccharides or monosaccharides, to immobilized lectins.75 77 Fig. 3 illustrates the binding of small glycans to BclA lectin from Burkholderia cenocepacia.26... 

The partially methylated monosaccharides obtained on depolymerization of the permethylated sample are preferably analyzed as acetates by g.l.c.-m.s., as shown by Bjomdal and coworkers.41,42 The neutral sugars and the amino sugars obtained in acetolysis-acid hydrolysis are reduced, and acetylated for the analysis, and the amino-hexitol and the neuraminic acid residues are acetylated after methanolysis. Identification with the aid of g.l.c.-m.s. has been described for all of the common components of protein- and lipid-linked glycans and oligosaccharides from animal cells, namely, the neutral sugars,41-43 hexitols,44 hexosamines,29,43,45,46 aminohexitols,31,32 and neuraminic acids.33,34,47... 

Acid-labile linkages of carbohydrates are commonly those of furano-sidic sugar residues or of deoxy monosaccharides.50,63 Consequently, neuraminic acid and fucose residues, which occur as terminal monosaccharides of protein- and lipid-linked glycans, are removed by hydrolysis with a dilute acid. The linkages formed by these two sugar residues can conveniently be differentiated by subjecting a portion of... 

Polysaccharides that are formed from only one type of monosaccharide are called homo-glycans, while those formed from different sugar constituents are called heteroglycans. Both forms can exist as either linear or branched chains. 

Very useful manual for analysis of all types of sugar-containing molecules—monosaccharides, polysaccharides and glycosamino-glycans, glycoproteins, proteoglycans, and glycolipids. 

Occasionally, the branchings are incomplete and the formation of the N-acetyl-lactosamine residues is only started in outline, as in the glycans of ovotransferrin (see Fig. 15), ovalbumin (see Fig. 16), and ovomucoid (see Fig. 18). In other instances, glycan structures such as have just been described are enriched with supplementary monosaccharide residues for example, the occurrence of disialyl groups [a-NeuAc-(2—>8)-a-NeuAc], and of /3-Gal-(l- 3) residues linked to the terminal galactosyl residues, has been demonstrated in different tissues and cell membranes,114,115 and in calf-thymocyte membranes,118 respectively. 

It thus became desirable to understand, first, the basis of this determinism in the creation of glycosidic linkages, and second, the order in which the residues of monosaccharides of the branching points are conjugated. Some work has now been performed that demonstrates that this double problem is linked simultaneously to the specificity of the glycosyltransferases and to the presence of well defined, oligosaccharide structures in the glycan molecule. For example, Roseman s... 

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