Acetamido sugar residues

The only example to date of direct addition of a carbohydrate residue to a peptide chain was the coupling72 of 2-acetamido-4-0-(2-acetamido-2-deoxy-/ -D-glucopyranosyl)-2-deoxy-/ -D-glucopyranosylamine (37) with sodium poly(L-aspartate) in the presence of 3-(3-dimethylamino-propyl)-l-ethylcarbodiimide hydrochloride.73 The proportion of sugar residues introduced into the peptide chain was limited. 

Oxidation of 2-acetamido-2-deoxy-D-glucose derivatives with hypoiodite at 0° proceeds quantitatively, without side reactions, and is satisfactory as a procedure for end-group assay in oligosaccharides containing amino sugar residues.177 The possibility that (1 —> 3)-linked disaccharides may be degraded under the reaction conditions must not be overlooked. 

Whilst there appears to be limited scope at present for the utilization of these observations in determinations of polysaccharide structures, they can be of value when the Morgan-Elson test is applied to oligosaccharides containing amino sugar residues, as the work on the oligosaccharides from human milk2 has shown. Obviously, no simple relation exists between a positive test and the presence of free 2-acetamido-2-deoxyhexose, but much information may be culled by a consideration of all the factors outlined above. 

H( C)-HMQC]. The chemical shift of C-2, 50.91 ppm, identified residue A as the acetamido sugar, a-GalNAcp. 

The different stability of the glycosidic linkage of 2-acetamido-2-deoxy-D-mannuronic acid towards hydrogen fluoride at room temperature in H. influenzae and S. pneumoniae polysaccharides on the one hand and in the N. meningitidis polysaccharide on the other, may be accounted for by the different neighboring sugar residues. 

Svennerholm152 found that the molecular ratios of the lipid and sugar residues of the Tay-Sachs ganglioside are ceramide hexose 2-acetamido-2-deoxy-D-galactose N-acetylneuraminic acid = 1 2 1 1. 

When UDP-2-acetamido-2-deoxy-D-glucose and UDP-N-acetyl-muramyl-pentapeptide are together added to broken bacterial-cell preparations, a new product is formed that contains the sugar and sugar-peptide portions of the precursors. If cells broken by means of a sonic oscillator are used, it is necessary to carry out the incubations on a filter-paper support " the precise function played by the filter paper is not yet known. In contrast, if enzymes are prepared by grinding cells with alumina, filter-paper support is unnecessary and the product contains a linear glycan backbone in which the two sugar residues occur in the alternate sequence expected. ... 

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