Disaccharide repeating units

Disaccharide Repeating Units in the Regular Regions of Glycosaminoglycans. 

We used this procedure in estimating the chain properties of hyaluronic acid 16). Hyaluronic acid is a regular polysaccharide with a disaccharide repeat unit. The two units are glucuronic acid (Figure 1) and N-acetyl glucosamine (Figure 2). 

Carbohydrate chain Main disaccharide repeating unit Refer- ences... 

The sodium salt form, at 92% r.h., crystallizes in a trigonal unit-cell, with a = b = 1.45 nra and c = 2.88 nm, with a 3(— 0.96) conformation of the chain. On conversion of the sodium form into the calcium form, the unit cell converts to the orthorhombic, with a = 0.745 nm, b = 1.781 nm, and c = 1.964 nm. The chain is a 2(0.982) helix, with the disaccharide repeat-unit. Two antiparallel chains are contained in the unit cell, along with— 30 water molecules. The space group is P2,2,21. 

Hindered rotation is studied for the disaccharides composed of basic p-glucopyranose units. The van der Waals Interactions are calculated for the Lennard-Jones, Buckingham, and Kitaygorodsky interatomic potential functions. Values of the ratio of unperturbed to free-rotation root-mean-square end-to-end distance are calculated for chains composed of the unsolvated disaccharide repeating units. 

Uronic acid degradation of the fully methylated Klebsiella type 47 capsular polysaccharide120 results in a partially methylated polysaccharide having a disaccharide repeating-unit (see Section IV,2, p. 218), in which the hydroxyl groups at C-3 in the L-rhamnose residues are free. Oxidation with ruthenium tetraoxide consequently gave the product 82, which, on treatment with base, followed by... 

Two mechanisms were demonstrated for the assembly of linear chains of bacterial polysaccharides.278,279 Their general features are presented in Scheme 2, using as an example a hypothetical polysaccharide (-B-A-) composed of disaccharide repeating units. 

Figure 2. Structures of the glycosaminoglycans and their linkage regions to protein. Two disaccharide repeating units are shown to emphasize the microheterogeneity that exists in some cases. Heparan sulfate and heparin show many structural similarities. However, heparan sulfate contains more GlcNAc(a-1 — 4)GlcUA repeating units fewer glucosamine residues are N-sulfated, and few iduronic acid residues are sulfated at C2.

For each mixture, maximum a-helix content was obtained at a characteristic ratio of amino acid residues to disaccharide repeating units (Table IV). 

Geert-Jan Boons et al. also synthesized peptidoglycan fragments such as the disaccharide repeating unit [51] and muramyl peptide derivatives containing Lys and DAP residues [52-55] obtained through cross olefin metathesis [56], The muramyl peptides, such as 48 prepared by solid-phase synthesis on Sieber amide resin (Scheme 14.6), were subjected to biological and structural analyses [50, 57, 58] of... 

The structures of the type-specific polysaccharides are shown in Table II, and, except for one particular strain43 of type e, are composed of linear arrangements of disaccharide repeating-units. The clinically... 

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