Polysaccharide branched type

The algal polysaccharides resembled the relatively simplified structures of tile neutral mucilages, as in the case of carrageenan A wider spectrum of struclures is found in Ihc bacterial gums, which arc generally of the highly branched type exuded by higher plants,... 

Numerous examples further illustrate the great value of the Smith degradation in determinations of the fine structure of polysaccharides. They include studies on arabinoxylans, mesquite gum, an exocellular yeast mannan, and a type-specific bacterial polysaccharide. Branching patterns in complex types of glycoproteins from several different origins have been elucidated, and detailed structures of gum exudates, seed polysaccharides, and pectic sub-... 

Structural polysaccharides are almost always linear molecules, while polysaccharides that serve primarily as energy sources are commonly branched, or in some cases (e.g. starch) a mixture of linear and branched polysaccharides with the branched type predominating. In general, branched polysaccharides are easily soluble in water and have... 

CWM was then extracted sequentially with water at 80 and with ammonium oxalate at 80, delignified with acidified sodium chlorite at 70 , and then further extracted with M and 4M sodium hydroxide. The crude polysaccharide extracts were likewise analyzed for constituent sugars and uronic acid (Table II). In order to obtain defined polysaccharide fractions the following separations were attempted. Polysaccharide fraction A was separated by ion-exchange chromatography on diethylaminoethyl(DEAE)-Sephadex A-50 and the neutral fraction afforded a virtually pure arablnan ( in Scheme 2) after selective precipitation with cetyltrimethylammonium hydroxide (7 ). Linkage analysis by methylation confirmed that this arablnan was of the highly branched type associated with pectins for which the representative, but not unique, structure (J ) may be advanced. 

Fig. 4.16. Schematic representation of the effective volumes of linear, branched and linearly branched types of polysaccharides...

Type III Limit dextrinosis, Forbes or Corl s disease Absence of debranching enzyme Accumulation of a characteristic branched polysaccharide. 

Type IV Amylopectinosis, Andersen s disease Absence of branching enzyme Accumulation of a polysaccharide having few branch points. Death due to cardiac or liver failure in first year of life. 

A regular fine structure causing maximal hydrogen bonding between the molecules reduces the possibility of reversible processes and therefore reduces the gel-forming properties of the compound. Other polysaccharides with different types of monomers or with branched chain structures can be treated in a similar manner. However, much more study of their fine structure and the accessibility of their functional groups is necessary. 

Molecular Structure. Most starches consist of a mixture of two polysaccharide types amylose, an essentially linear polymer, and amylopectin, a highly branched polymer. The relative amounts of these starch fractions in a particular starch are a major factor in determining the properties of that starch. 

The integral intensities of signals of polysaccharides, obtained with a modem spectrometer under the usual operating conditions, are proportional or quasi-proportional, to the number of 13C nuclei present. This has been observed, in particular, in the case of linear hexo-pyranan structures containing one type,11,47,51,55,56 58-61 or two equal types, of linkage,62 or branched-chain polymers having two linkage types,53,58 where the resonances are readily resolved. In such cases, the T values would be low, 0.2 s or less, and the n.O.e. values would be approximately equal. However, few actual determinations of these values have been made, and extrapolation of such assumptions to more-complex polysaccharide structures is not recommended, as outlined in Section V,2,... 

Figure 14.2 Representative oligosaccharide structures found on mammalian glycoproteins and glycolipids. The complex oligosaccharides may be bi-, tri-, or tetra-antennary the branches may be more or less elongated with 1—>4 linked lactosamine units, and they may or may not be sialylated. The SLex, Lea, and Leb structures represent the different blood group determinants often present on lipids, and the elongated core 2 structure is a mucin-type glycosylation. Proteoglycans have a common core to which a variety of linear acidic polysaccharides are attached.

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