Uronic acids residues

Most of the glucuronoxylans have single 4-0-methyl-o -D-glucopyranosyl uronic acid residues (MeGlcA) attached always at position 2 of the main chain Xylp units (Fig. 2). This structural type is usually named as 4-0-methyl-D-glucurono-D-xylan (MGX). However, the glucuronic acid side chain may be present in both the 4-0-methylated and non-methylated forms (GlcA). 

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 uronic acid residues in fraction N1... 

Although the glycosidic bonds of uronic acid residues are usually more resistant to acid hydrolysis than those of neutral polysaccharides,218 these linkages in heparin are more readily cleavable then those between the hexosamine and the uronic acid residues. Disaccharides obtained by exhaustive hydrolysis of heparin with 0.5 MHC1 at 80° contained hexu-... 

Periodate oxidation was used in early work for obtaining information on the substitution pattern of heparin.1,100 102 In fully N-substituted (N-sulfated or N-acetylated, or both) glycosaminoglycans, the only bond susceptible to splitting by periodate is C-2-C-3 of unsubstituted uronic acid residues. As illustrated in Scheme 4 for heparin, only nonsulfated D-glucuronic acid and L-iduronic acid residues are split by periodate. 

A computer-built model, having an axial rise per disaccharide of 0.84 nm and possible stabilization by an 0-3-H 0-5, intramolecular hydrogen-bond from a hexosamine to a uronic acid residue, is a rather extended, two-fold helix (see Fig. 8),346 with each fold approximately corresponding341,346 to the disaccharide repeat in Fig. 7a. A substantially similar model was obtained by use of calculations also taking into consid-... 

Fig. 11. —Proposed Model for aTemary Complex between Heparin (HEP), Antithrombin (AT), and Thrombin (T), Involving an Octadecasaccharide Sequence of the Heparin Chain.419 [Within the large brace, full circles denote uronic acid residues, the small brace encompassing the minimal binding-site for AT. The thrombin-binding region is presumed to be situated towards the nonreducing end of the AT-binding sequence,933 which is arbitrarily assumed to be in the middle of the heparin chain.]...

Mucopolysaccharide8 Without Hexosamine or Uronic Acid Residues... 

The relaxation of certain 13C nuclei in some uronic acids and derivatives is affected by Gd3+. For example, on addition of gadolinium nitrate to solutions of heparin or dermatan sulfate in D20, the C-l and C-6 signals of the uronic acid residues are selectively diminished. This property would be expected from a-L-idopyranosyluronic acid residues, as the C-l and C-6 signals of sodium a-D-idopyranuronate are similarly lessened in intensity, whereas those of the j8 anomer are... 

The mammalian blood anticoagulant heparin is also a carbohydrate polymer in which amino sugars (glucosamine) alternate with uronic acid residues (see... 

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