Polysaccharide branching

Normal com starch is composed of 20—30% of the linear polysaccharide amylose and 70—80% of the branched polysaccharide amylopectin. 

However, fine grinding of iasoluble dietary fiber such as bran reduces WHC. In general, branched polysaccharides are more soluble than are linear polysaccharides because close packing of molecular chains is precluded. WHC is strongly kifluenced by the pentosan components of cell-waU dietary fiber and varies with the stmcture and source of these hemiceUuloses. 

Whether the chemical repeating motif is a simple disaccharide or up to a complex octasaccharide, the molecular morphologies of branched polysaccharides are quite intriguing. The structure of welan (43) is a pleasant surprise. Others... 

Helical Parameters and Conformation Angles in Two Branched Polysaccharides... 

A putative packing arrangement in the monoclinic unit cell (Fig. 40b) reveals that there are no direct interactions among the main chains of adjacent helices. However, the peripheral side chains form hydrogen bonds with both main and side chains. As in the case of 46, the ordered structure of 47 supports the hypothesis that side chains often promote the formation of stable, branched polysaccharide helices. 

Recent progress of basic and application studies in chitin chemistry was reviewed by Kurita (2001) with emphasis on the controlled modification reactions for the preparation of chitin derivatives. The reactions discussed include hydrolysis of main chain, deacetylation, acylation, M-phthaloylation, tosylation, alkylation, Schiff base formation, reductive alkylation, 0-carboxymethylation, N-carboxyalkylation, silylation, and graft copolymerization. For conducting modification reactions in a facile and controlled manner, some soluble chitin derivatives are convenient. Among soluble precursors, N-phthaloyl chitosan is particularly useful and made possible a series of regioselective and quantitative substitutions that was otherwise difficult. One of the important achievements based on this organosoluble precursor is the synthesis of nonnatural branched polysaccharides that have sugar branches at a specific site of the linear chitin or chitosan backbone [89]. 

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

Yu, L.P. and Rollings, J. E., Quantitative branching of linear and branched polysaccharide mixtures by size exclusion chromatography and on-line low-angle laser light-scattering detection, /. Appl. Polym. Sci., 35, 1085, 1988. 

The branched polysaccharide dextran is assembled with alkanethiol-modified gold nanoparticles and the resulting nanocomposite is then functionalized to facilitate the specific binding of target biomolecules. This biorecognition process can be easily detected by particle plasmon resonance (PPR), based on the optical properties of gold nanoparticles [163]. 

Scheme 7 Chitosan-sialic acid hybrid as branched polysaccharide...

In amylopectin and glycogen p =p is the branching probability, which does not depend on the molar mass of the branched polysaccharides. 

Amylose consists of unbranched al 4-linked chains of 200-300 glucose residues. Due the a configuration at C-1, these chains form a helix with 6-8 residues per turn (1). The blue coloring that soluble starch takes on when iodine is added (the iodine-starch reaction ) is caused by the presence of these helices—the iodine atoms form chains inside the amylose helix, and in this largely non-aqueous environment take on a deep blue color. Highly branched polysaccharides turn brown or reddishbrown in the presence of iodine. 

Concanavalin A is an antibody-like protein isolated from the jack bean. 82 It was shown to form a precipitate with glycogen and with yeast mannan, and was later also used to differentiate between glycogen-like polysaccharides from various sources.283 284 It has now been shown that concanavalin A forms a precipitate only with branched polysaccharides which contain terminal, nonreducing a-D-glucopyranosyl or a-D-manno-pyranosyl groups.18 The combining sites of the protein appear to be directed against the 2-deoxy-a-D-aratano-hexopyranosyl system.2 ... 

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