Polysaccharide inclusion compound

It should be noted that the different structures of amylose and amylopectin confer distinctive properties to these polysaccharides (Table II). The linear nature of amylose is responsible for its ability to form complexes with fatty acids, low-molecular-weight alcohols, and iodine these complexes are called clathrates or helical inclusion compounds. This property is the basis for the separation of amylose from amylopectin when starch is solubilized with alkali or with dimethylsulfoxide, amylose can be precipitated by adding 1-butanol and amylopectin remains in solution. 

Amylopectin a component of starch (the other is amylose). A. is a branched, water-insoluble polysaccharide (A/, 500,000-1,000,000) consisting of a main chain of a-l,4-linked D-glucose units with side chains (15-25 D-glucose units) attached a-1,6 to every 8th or 9th glucose. A. forms violet to red-violet inclusion compounds with iodine. It swells in water, and upon heating it forms a paste. 

We then studied in more detail the chiroptical properties of iodine inclusion compounds with pure amylose and a few other polysaccharides [50, 51]. 

The acid condensation methods do not distinguish between monosaccharides and polysaccharides, as the various classes of carbohydrates each have different absorption maxima, which results in different molar absorptions at any chosen wavelength. Furthermore, when treated with concentrated sulfuric acid, some three- and four-carbon compounds will condense into structures which will produce colours with those reagents. When the object of the analysis is to obtain some estimate of the total amount of carbohydrate or carbohydratelike material present, the inclusiveness of these methods is useful. However, when the object is to distinguish between the easily metabolised simple sugars and the complex storage and structural materials, these methods give no information at all. 

B) complexes of polysaccharides or disordered proteins with amphiphilic compounds inclusion... 

Additives that specifically interact with an analyte component are also very useful in altering the electrophoretic mobility of that component. For example, the addition of copper(II)-L-histidine (12) or copper(II)-aspartame (54) complexes to the buffer system allows racemic mixtures of derivatized amino acids to resolve into its component enantiomers. Similarly, cyclodextrins have proven to be useful additives for improving selectivity. Cyclodextrins are non-ionic cyclic polysaccharides of glucose with a shape like a hollow truncated torus. The cavity is relatively hydrophobic while the external faces are hydrophilic, with one edge of the torus containing chiral secondary hydroxyl groups (55). These substances form inclusion complexes with guest compounds that fit well into their cavity. The use of cyclodextrins has been successfully applied to the separation of isomeric compounds (56), and to the optical resolution of racemic amino acid derivatives (57). 

The fact that hydrates are more common in the disaccharides provides an opportunity to study the way in which the inclusion of water molecules may influence the hydrogen-bonding patterns of oligo- and polysaccharides. The crystal structures of several compounds have been studied in both the anhydrous and hydrated forms. 

Because tocopherols and tocotrienols and their esters are lipid-soluble compounds, they are soluble in organic solvents and can be extracted with them. Simple extraction of vitamers from cereal products and other foods containing high amounts of fiber and other polysaccharides may be less effective because of the complex matrix. Inclusion of the vitamers in the matrix by various interactions may hinder the penetration of the solvent into the sample, thus lowering its extraction power. To improve the extraction of lipids from cereals, dynamic extraction with hot solvents (Balz et al., 1992 Zhou et al., 1999), and modem techniques such as supercritical fluid extraction, may be used. 

D-glucose and the three-enzyme system GOx, mutarotase and invertase for sucrose estimation. A common format was adopted to facihtate design and operation, in this case immobilization method, the fact that all enzymes used were oxidases and that a common detection principle, reoxidation of H2O2 generated product, was chosen (except for ascorbic acid which was estimated directly). Pectin, a natural polysaccharide present in plant cells, was used as a novel matrix to enhance enzyme entrapment and stabilization in the sensors. Interferences related to electrochemi-caUy active compounds present in fruits under study were significantly reduced by inclusion of a suitable cellulose acetate membrane diffusional barrier or by enzymatic inactivation with ascorbate oxidase. Enzyme sensors demonstrated expected response with respect to their substrates, on analyte average concentration of 5 mM. 

Native molecules are not used frequently for chiral separations because of the dense structure of the oligo- and polysaccharide chains (of which some are helical). Polysaccharides are often derivatized to increase their enantioselec-tivity by enlarging their cavities. This structural change is important because the cavities contribute to the enantiose-lectivity by inclusion of the compounds. Enantiomers are thus separated based on their different affinities (hydrogen bonds, dipole-, tt-tt-, and van der Waals interactions) for the chiral cavities of the saccharides. In Figure 52.11, the structures of amylose, dextran, and heparin, a few polysaccharide selectors, are shown. 

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