Repeating units polysaccharides

Bastin, D.A., Brown, P.K., Haase, A., Stevenson, G., Reeves, RR. Repeat unit polysaccharides of bacteria a model for polymerisation resembling that of ribosomes and fatty acid synthetase, with a novel mechanism for determining chain length. Mol Microbiol 7 (1993) 725-734. 

L-glycerate and poly(p-hydroxybuty-rate) repeating units. Polysaccharide prod, by Pseudomonas elodea. Shows useful rheological props. Thickener and stabiliser for foods, also used in cell and tissue cultures. 

Polysaccharides are macromolecules which make up a large part of the bulk of the vegetable kingdom. Cellulose and starch are, respectively, the first and second most abundant organic compounds in plants. The former is present in leaves and grasses the latter in fruits, stems, and roots. Because of their abundance in nature and because of contemporary interest in renewable resources, there is a great deal of interest in these compounds. Both cellulose and starch are hydrolyzed by acids to D-glucose, the repeat unit in both polymer chains. 

The polymer 21 contains a reactive olefinic linkage in its repeating unit, and can be modified chemically in various manners. In particular, it is expected that the polymer can be used as a versatile precursor for the chemical synthesis of polysaccharide... 

Five articles on polysaccharide helices solved prior to 1979 have appeared in the volumes published between 1967 and 1982.2-6 The first was a review on X-ray fiber diffraction and its application to cellulose, chitin, amylose, and related structures, and the rest were bibliographic accounts. Since then, X-ray structures of several new polysaccharides composed of simple to complex repeating units have been successfully determined, thanks to technological advances in fiber-diffraction techniques, the availability of fast and powerful computers, and the development of sophisticated software. Also, some old models have been either re-... 

Pectin belongs to a family of plant polysaccharides in which the polymer backbone consists of (1— 4)-linked a-D-galacturonic acid repeating-units. Often, (1— 2)-linked a-L-rhamnose residues interrupt the regular polygalacturonate sequence. The high viscosity and gelling properties of pectins are exploited by the food and pharmaceutical industries. X-Ray studies on sodium pectate, calcium pectate, pectic acid, and pectinic acid (methyl ester of pectic acid) have disclosed their structural details. 

Cartesian and cylindrical polar atomic coordinates of the structural repeating unit of 31 polysaccharide helices are provided in Tables A1 to A31. Errors, if any, in the original publications have been corrected. The coordinates of hydrogen atoms are given in a majority of structures. If missing, they are not available in the references cited in Table I. Each table caption contains the structure number and polymer name assigned in Table I. Refer to Table II for its chemical repeating unit. Cartesian (x, y, z) and cylindrical (r, , z) coordinates are related by x r cost ), y = r sin<(> and z is the same in both systems. 

Pneumococcus, polysaccharides from, 6-7 Poly(a-L-guluronic acid), 353, 355-356,415 Poly(P-D-mannuronic acid), 353-354,414 Polysaccharides, 311 -439 amino sugar derivatives, 166 chemical repeating units, 321, 324-325... 

D-Mannose is common, but L-mannose has only been found in a small group of extracellular polysaccharides of related structures, one of which is elaborated by Alcaligenes ATCC 31555. In these polysaccharides, it is a-linked and partially replaces an a-L-rhamnopyranosyl residue in the pentasaccharide repeating-unit. It seems possible that these sugar residues are scrambled, but the other possibility, that there are two populations of polysaccharides, has not yet been excluded. 

Many bacterial polysaccharides contain phosphoric ester groups. There is a limited number of examples of monoesters. More common are phosphoric diesters, connecting an amino alcohol or an alditol to the polysaccharide chain. Another possibility is that oligosaccharide or oligosaccharide-alditol repeating units are connected to a polymer by phosphoric diester linkages. In addition to the intracellular teichoic acids, several bacteria, for example, different types of Streptococcus pneumoniae, elaborate extracellular polymers of this type. These polymers are generally discussed in connection with the bacterial polysaccharides. 

Xanthan Gum. Xanthan gum is produced by the bacterium Xanthomonas campestris. Commercial productions started in 1964. Xanthans are water-soluble polysaccharide polymers with the following repeating units [502], as given in Table 17-5 and Figure 17-6. 

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). 

In a recent paper650 the relationships between Rhizobium radicicolum polysaccharides and those of pneumococcus are indicated by crossprecipitin reactions of the former with Types III and VI anti-pneumococcus horse sera. In addition, hydrolysis of the methylated polysaccharide of Rhizobium radicicolum yields equal amounts of 2,3,6-trimethyl-D-glucose, 2,3-dimethyl-D-glucose and 2,3-dimethyl-D-glucuronic acid.65 1 The minimum trisaccharide repeating unit consists, in part, of cello-biuronic acid, and may be represented ... 

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