Linkages sugar residues

Methylation analyses of fractions N1 indicated that the linkage pattern of uronic acid residues (table 2) remains unchanged during ripening whereas the glycosidic linkage composition of neutral sugar residues showed different alterations. 

Glycosidic linkage composition of the neutral sugar residues in fraction N1... 

Figure 1.30 Hydroxyl groups within sugar residues may undergo alkylation or acylation reactions, forming ether or ester linkages.

In each nucleotide monomer of DNA or RNA molecules, a phosphate group is attached to the C-5 hydroxyl of each sugar residue in an ester (anhydride) linkage. These phosphate groups in turn are linked in diester bonds to neighboring sugar groups of adjacent nucleotides... 

An example of the use of 1,4-butanediol diglycidyl ether for the activation of soluble dex-tran polymers is given in Chapter 25, Section 2.3. One end of the fezs-epoxide reacts with the hydroxylic sugar residues of dextran to form ether linkages, which terminate in epoxy functionalities. The epoxides of the activated derivative then can be used to couple additional mol-ecules-containing nucleophilic groups to the dextran backbone. 

Depolymerization of the permethylated carbohydrate is achieved by hydrolysis with acid. Under these conditions, the amino sugar residues are N-deacetylated, and the aminohexosidic linkages become resistant to hydrolysis. Stellner and coworkers29 showed that, when the acid degradation is conducted in 95% acetic acid, the amino sugar residues are also liberated, and can be analyzed by the methylation technique.29 Therefore, acetolysis followed by acid hydrolysis is now commonly used, as it allows the analysis both of hexose and hexosamine residues. 

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... 

The final compound was isolated after peracetylation no trace of P-anomer was formed during the process. As in their first report, these authors also investigated the MPEG-DOX linkage of the first sugar residue via hydroxyl groups other than the anomeric one (Scheme 4.16). 

Scheme 4.16 MPEG-DOX linkage of the first sugar residue via nonanomeric hydroxyl groups.

Stereochemistry of the Intermediate. These experiments therefore demonstrated that a 2-fluoroglucosyl-enzyme had been trapped. It was then of interest to prove the stereochemistry of the linkage of this sugar residue to the enzyme. Unfortunately, the 19F-NMR spectrum shown in Figure 4 was of no use in this regard, since the 19F-chemical shift of 2-deoxy-... 

Tryptophan 108 is recognized to be an active site in promoting the hydrolysis of 3(l,4)-glycosidic linkages between amino sugar residues in polysaccharide components of the bacterial cell walls. This residue is shown to occupy the cleft as well as trjrptophan 62 and 63, and is in a hydrophobic region. Tryptophan residues 62 and 108 are indispensable for the action of lysozyme, and tryptophan 62 is known to be the only binding site for the complex formation (13). Oxidation of tryptophan-108 is expected... 

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