Amylose inclusion compound

Fig. 8. Amylose inclusion compounds scheme of the amylose helix showing the inclusion channel. The guest compound is shaded (58).

The linear arrangement of iodine atoms in the amylose inclusion compound has generated much interest right from the early days with respect to its spectroscopic and optical properties 138 -140). It has also been known for many years that polyvinyl alcohol (PVA) behaves similarly, and this was applied by Polaroid Corporation for the manufacture of polarising plastic using stretched sheets of iodine-stained polyvinyl alcohol170). 

Amylose inclusion compounds, 14 168 Amylosic phases, for chiral separations, 6 88-89... 

Cavilaics include crown rnacroring inclusion compounds (coronates), cryptates, podates. cytlophane host inclusion compnunds. calixarene inclusion compounds, cyclodextrin and amylose inclusion compounds, cucurbituril inclusion compounds, molecular deft inclusion compounds, and anionic guest inclusion compounds. 

Lysophosphatidyl cholines (LPC), which occur in cereal as amylose inclusion compounds (starch lipids cf. 15.2.5), reduce the foam stability. The terrqterature management during the mashing process regulates the LPC concentration because it determines the activity ratio of a-amylase, which contributes to the release of LPC from amylose, to phospholipase B, which catalyzes the... 

The reaction between starch and iodine (or iodine-iodide mixtures) to form an inclusion compound was first reported in 1814 by Colin and de Claubry 131) and has since become familiar to all chemists through its applications in analytical chemistry. Its deep blue colour (kmax 620 nm) has been known for years to result from a linear arrangement of polyiodide within a canal formed by a helical coil of amylose. The helical amylose structure will trap other molecules 132,1331 and other hosts will stabilise polyatomic iodide guests134> 135). 

More recent crystallographic work has been directed at inclusion compounds of V-amylose (including more detailed examination of the polyiodide compound) and at the structures of Va-amylose and Vh-amylose. Despite the terminology used, both forms have significant water content and may therefore be classed as inclusion compounds in their own right. 

Fig. 14. The Vh-amylose polyiodide inclusion compound shown as a simplified projection on the a, b plane. Guest water molecules are shown as filled circles in the interstitial sites. The guest polyiodide chains are situated inside the helical amylose chains and their cross-sections are shown here as stippled circles...

Thus, despite all the work carried out on starch-iodine, the exact nature of the guest iodine atoms is still not totally resolved. Teitelbaum, Ruby and Marks 156) have examined the compound using Raman and 129I Mossbauer spectroscopy and concluded that the pentaiodide ion 1 was the major chromophore present. However work based on iodine compounds of cyclodextrins 3-134 135) has shown that a variety of polyiodide species is possible, and the starch-iodine inclusion compound could conceivably involve I2 If, I2 I- I2, or I5 species 157). The anhydrous amylose-iodine compound has recently been found to exhibit semiconductor behaviour 158). 

Hui et al. 177) have investigated the inclusion compounds between carboxymethyl-amylose and the two aromatic keto-acid salts (30) and (31). The binding constants... 

Inclusion complexation, 77 552-553 Inclusion compounds, 74 159-190, 170-182 amylose, 74 168 anionic guest, 74 170 cailixarene, 74 165-166 categories of, 74 160 crown macroring, 74 160-161 cucurbituril, 74 168-169 cyclodextrin, 74 166-167... 

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. 

Starch-guest molecule compounds in inclusion complexes are usually nonstoichiometric species. On the other hand, in the case of amylose such compounds are stoichiometric, but their composition is not repeatable. Starch complexes may consist of partly physical mixtures, adsorbates, and true inclusion complexes formed by direct involvement of dipolar interactions, host-guest hydrogen bonds, and/or clathration-like interactions within the starch matrix. 

Thus the blue inclusion complex becomes visible only when all the hydrogen sulfite has been consumed. According to studies by / . C. Teitelbaum, S. L. Ruby and T. ]. Marks the blue inclusion compound consists of the amylose component of the starch and the polyhalogenide anion Is", this was established by comparing the Raman and I Mofibauer spectra of the blue-black amylose-iodine complex with those of the adduct between trimesic acid hydrate and H Is , the structure of which is known (see figures). 

There seems little doubt that the dissolved complex is an inclusion compound in which iodine resides within the annular cavity of a more or less regular helical amylose chain. This picture emerged early from the work of Rundle and coworkers on the crystalline (10) and dissolved (11) complex and has not been seriously challenged by any more recent studies. Despite the acknowledged helical character of the dissolved complex, it is very clear from hydrodynamic evidence that the complexed polymer does not adopt a rigid, rod-like conformation indeed, the hydrodynamic volune of the polymer decreases upon complexation with iodine (2. 3, ) The spectroscopic properties of the dissolved complex imply that the bound iodine is arrayed in linear sequences, but neither the... 

CDs have special properties dependant on their molecular structures. For instance, their hydrophobic cavities can encapsulate organic and inorganic molecules with smaller molecular size to form various inclusion compounds in liquid- or sohd-state forms [3] while their hydrophilic shells can generate noninclusion complexes with larger molecular guests, such as amylose molecules and enzyme molecules [4,5]. Mainly based on the formation of the two kinds of complexes, CDs are widely used in many areas, including foods, pharmaceuticals, cosmetics and personal care industries. 

Amylose. A component (20-30%) of starch surrounded by amylopectin. A. is a linear a-l,4-glucan, Mr 50000-200000 (see figure at starch). Crystalline A. occurs in various polymorphic forms (A, B, C, and V-A.), that differ in conformation and crystal packing. A. is soluble in water and gives the characteristic blue color with iodine-potassium iodide solution (Lugol s solution) (formation of inclusion compounds, traces of iodide ions are necessary for occurrence of the blue color, formation of I5 ions I -1 I I -1). Because of its predominately unbranched structure, A. can be degraded to oligosaccharides both by a- and by /S-amylase. The screw-like (helical) conformation also allows the formation of inclusion compounds with alcohols. 

These cyclohexa-(-hepta-, -octa-)amyloses are arranged in the crystal lattice of C. in such a way that open, intramolecular channels are formed in which guest molecules can be enclosed in varying amounts up to saturation ("molecular encapsulation ), e.g., gases, alcohols, or hydrocarbons. a-C. also forms a blue-colored inclusion compound with iodine in which the iodine atoms are arranged like a string-of-pearls in the channels. On account of this property C. are used in the production of food, cosmetics, pharmaceuticals, and pesticides as well as for solid phase extractions and for use as high performance separation phases for enantiomeric and diastereomeric mixtures. 

Formation of crystalline cyclohepta-amylose inclusion complexes has been followed by recording continuously the turbidity of the aqueous solution of cyclohepta-amylose and the guest molecule (solvent, drug, or aromatic compound) from 60 C downwards. The concentrations of the guest molecules were such that they could not form crystals above the crystallization temperature of pure cyclohepta-amylose. The appearance of turbidity caused by crystal formation before the characteristic temperature of cyclohepta-amylose crystallization is therefore considered to be evidence for inclusion complex formation. The influence of parameters such as concentration, pH, cooling speed, presence of inorganic salts, and inoculating crystals was studied. 

Powdered inclusion complexes have been obtained by freeze-drying together cyclohepta-amylose and anti-inflammatory drugs (indomethacin, flufenamic acid, or phenylbutazone). Significantly less irritation was caused to the stomach of rats by phenylbutazone on oral administration when the drug was given as a freeze-dried inclusion compound, but no such effect was observed for the other two drugs. 

Formation of insoluble inclusion compounds with amylose-the water soluble part of starches-is another important application area for monoglycerides, especially saturated distilled monoglycerides (Krog, 1981). By complexing the amylose, monoglycerides improve texture of starch-based foods such as processed potato products, macaroni, noodles and other pasta foods. 

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. 

Lipids also influence the properties of starch. Like free amino acids, monoglycerides or fatty acid esters of hydroxy acids, lipids form inclusion compounds with amylose (cf. 4.4.4.14.3). Like di- and triglycerides, they also reduce the swelling capacity and solubility by inhibiting water diffusion. Therefore, both degreasing as well as lipid addition are of importance as physical modification methods of starches. 

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