Helix polysaccharide

Curdlan is a microbial polysaccharide that occurs naturally as a linear (triple-helix) polysaccharide composed of 1,3-P-hnked D-glucose units, produced by a strain of Mcaligenes faecalis (Figure 2.38). It is a neutral, bacterial polysaccharide without branched chains. It is insoluble in water and alcohol but soluble in alkaline solution and dimethyl sulfoxide (DMSO) [274-276]. It occurs as a tasteless powder, stable in dry state. It was reported as a support matrix for enzyme immobilization, through activation with epichlorohydrin that can be covalently linked to the available amino, hydroxyl, and suHhydryl enzyme groups [277]. It has the specific character to form an irreversible gel by heating of a water suspension [278]. Its water-insoluble nature helps to improve a material s water barrier capabihty, and its solubility in... 

Molecular Interactions. Various polysaccharides readily associate with other substances, including bile acids and cholesterol, proteins, small organic molecules, inorganic salts, and ions. Anionic polysaccharides form salts and chelate complexes with cations some neutral polysaccharides form complexes with inorganic salts and some interactions are stmcture specific. Starch amylose and the linear branches of amylopectin form inclusion complexes with several classes of polar molecules, including fatty acids, glycerides, alcohols, esters, ketones, and iodine/iodide. The absorbed molecule occupies the cavity of the amylose helix, which has the capacity to expand somewhat to accommodate larger molecules. The starch—Hpid complex is important in food systems. Whether similar inclusion complexes can form with any of the dietary fiber components is not known. 

Double helix involving two polysaccharide chains. The helix is stabilised by intermolecular hydrogen bonds... 

A polysaccharide such as xanthan gum is a chain of sugars. Some familiar polysaccharides are starch and cellulose. The backbone of xanthan gum is similar to cellulose, but the trisaccharide side chains of mannose and glucuronic acid make the molecule rigid, and allow it to form a right-handed helix. These features make it interact with... 

Fig. 1. — Schematic drawing of a hypothetical polysaccharide chain whose helix axis is along the c-edge of the unit cell.

Note a, b, and e are in A. a = p= 90 and 7 are in degress. a Chitin I and U were originally termed [S- and a-chitin, respectively. b Non-half-staggered double helix. e Capsular polysaccharide. 

Mutant YE-2 of Rhizobium meliloti excretes a mixture of soluble polysaccharides that include a complex succinoglycan having a branched octasaccharide repeat as well as a simple galactoglucan (22) having a linear disaccharide repeat.102 In contrast to the case of the succinoglycan, oriented fibers of the potassium salt of 22 have yielded good X-ray data and its three-dimensional structure has been established.39 The polymer forms a two-fold helix of pitch... 

Fig. 39.—fa) Stereo view of two turns of the left-handed. 2-fold helix of E. coli capsular polysaccharide (46) stabilized by hydrogen bonds involving both main and side chains. The vertical line represents the helix axis. 

Yanaki, T., Norisuye, T., and Fujita, H., Triple helix of schizophyllum commune polysaccharide in dilute solution. 3. Hydrodynamic properties in water, Macromolecules, 13, 1462, 1980. 

Michel, G., Chantalat, L., Fanchon, E., Henrissat, B., Kloareg, B., and Dideberg, O. (2001). The iota-carrageenase of Alteromonas fortis. A beta-helix fold-containing enzyme for the degradation of a highly polyanionic polysaccharide. J. Biol. Chem. 276, 40202-40209. 

Fig. 7 A model of the cell-wall polysaccharide (CWPS) of group A Streptococcus, looking down the barrel of the helix. The core of the helix is composed of a-L-rhamnose residnes with the 8-d-G1cNAc moieties displayed on the periphery. Reprodnced with permission from [99]. 2004 Elsevier Science...

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