Polysaccharides with polymer chains

Starch is a polysaccharide found in many plant species. Com and potatoes are two common sources of industrial starch. The composition of starch varies somewhat in terms of the amount of branching of the polymer chains (11). Its principal use as a flocculant is in the Bayer process for extracting aluminum from bauxite ore. The digestion of bauxite in sodium hydroxide solution produces a suspension of finely divided iron minerals and siUcates, called red mud, in a highly alkaline Hquor. Starch is used to settle the red mud so that relatively pure alumina can be produced from the clarified Hquor. It has been largely replaced by acryHc acid and acrylamide-based (11,12) polymers, although a number of plants stiH add some starch in addition to synthetic polymers to reduce the level of residual suspended soHds in the Hquor. Starch [9005-25-8] can be modified with various reagents to produce semisynthetic polymers. The principal one of these is cationic starch, which is used as a retention aid in paper production as a component of a dual system (13,14) or a microparticle system (15). 

Already in 1988 and 1991, Gao et al. [65,66] detected four different polysaccharides present in the leaves of Panax ginseng that had an effect on the complement system, but only two of them, the neutral, GL-NIa, and one of the acidic ones, GL-AIa, had potent activities at low concentrations. GL-NIa was found to be mainly an arabinigalactan type II polymer. GL-AIa was a polysaccharide with a rhamnogalacturonan core with neutral side chains of the AG-II type, confirmed by a strong reaction with the Yariv reagent and the methylation results. It was shown that the crude polysaccharide fraction contained KDO and DHA, suggesting the presence of Rhamnogalacturonan II in... 

Black pepper contains several polysaccharides of which one shows a strong effect as an immune enhancer based on the fact that the polymer is an anti-complementary polysaccharide. The polysaccharide has an Mw of approx. 40 kD. It is composed basically of rhamnose, arabinose, galactose and galac-turonic acid, and shows a high binding capacity for the Yariv reagent. This indicates that the side chain of the polymer is of the arabinogalactan type II, which is a common structure for several polysaccharides with an effect on the complement system [70]. 

The precise stereogeometry of molecules is important in determining the physical properties of a material and is critical in determining the biological properties of materials. Most synthetic and nonspecific natural polymers are a mix of stereoshapes with numerous stereocenters along the polymer chain. For polypropylene, every other backbone carbon is most likely a stereocenter. Even polyethylene has stereochemical sites wherever there is branching. The imprecise structures of most natural nonspecific polymers such as the polyisoprenes and polysaccharides have stereocenters at each branch. 

Fig. 9 a, b. Complex formation of polyelectrolytes with rigid polymer chains such as polysaccharides. (a) pH Dependence of the composition of the complex. (1) Theoretical values assuming stoichiometry (2) Experimental values (b) Schematic representation of a ladder-like complex structure of one part of SCS and two parts of GC SCS = Sulfated cellulose, GC = glycol chitosan... 

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