Amy loses

FIGURE 7.23 The starch phosphorylase reaction cleaves glucose residues from amy-lose, producing a-D-glucose-l-phosphate. 

The latter approach is used in the enantioselective determination of a Phase I metabolite of the antihistaminic drug, terfenadine. Terfenadine is metabolized to several Phase I compounds (Fig. 7-13), among which the carboxylic acid MDL 16.455 is an active metabolite for which plasma concentrations must often be determined. Although terfenadine can be separated directly on Chiralpak AD - an amy-lose-based CSP - the adsorption of the metabolite MDL 16.455 is too high to permit adequate resolution. By derivatizing the plasma sample with diazomethane, the carboxylic acid is converted selectively to the methyl ester, which can be separated in the presence of all other plasma compounds on the above-mentioned CSP Chiralpak AD [24] (Fig. 7-14). Recently, MDL 16.455 has been introduced as a new antihistaminic drug, fexofenadine. 

The reagent methanesulfonyl chloride-IV,IV-dimethylformamide has been used to prepare 6-chloro-6-deoxyamylose of d.s. 0.8 from the polysaccharide,391 but it was necessary first to convert the amy-lose into a reactive form by freeze-drying its aqueous solution. 

The unit cell is tetragonal, with a symmetry approximating P2i2 2i. The cell dimensions are a = b= 18.87 A (1.887 nm) and c = 7.99 A (799 pm). The helix diameter is 13.3 A (1.33 nm). One ethylenediamine molecule for every two D-glucose residues is indicated. The location of the ethylenediamine molecule in the lattice was discussed. The structure is almost identical to that of the amy-lose-dimethyl sulfoxide complex. 

The unit cell is orthorhombic, with a = 1.19 nm, b = 1.77 nra, and c = 1.052 nm. The favored conformation is a parallel-stranded, double helix. Each strand is a 6(0.351) helix. Equally good refinement was achieved with the OH-6 group in the g+[x(5) = 61°] or t[ (5) = 144°] states. The R factors are 37 and 36%, respectively, for these two positions. It was suggested that the true structure is a mixture of both. The double helices pack in an antiparallel array, with eight water molecules distributed along the a and h axes of the unit cell in the interstices between the helices. The structural features of A- and B-amy-lose were compared. 

The helical structure of amy-lose makes it possible for two ends of amylose fragments to bind together via glycoside bonds, (b) Top view showing interior of each loop. 

E2.1 Overview of Laboratory Isolation of Starch from Plant Materials E2.2 Enzymatic Quantitation of Total Starch in Plant Products E2.3 Determination of Total Amy lose Content of Starch... 

Presence of native starch crystals. In plant materials, starch exists as semicrystalline, granular entities. Starch molecules, both amy-lose and amy lopectin, with their many intermo-lecular hydrogen bonds, give structure to the starch granule (Zobel, 1988). The crystalline regions formed by this intermolecular hydrogen bonding are somewhat resistant to enzyme hydrolysis and need to be broken prior to enzyme treatments. 

Prepare a series of mixtures of pure potato amy lose and amylopectin (0%, 10%, 20%, 40%, 50%, 60%, 80%, 90%, and 100% amylose). Weigh 20 mg of each into round-bottom tubes with caps. 

FIGURE 24.13 Glucose polymers in starch, (a) Amy-lose consists of linear chains of a-glucose units linked by 1,4 bonds, (b) Amylopectin has branch points about every 25 sugars in the chain. A glucose unit at a branch point uses two of its hydroxyls (at C4 and C6) to form 1,4 and 1,6 links to two other sugars. 

Radicals derived from ethers show fragmentation if they are suitably substituted.51 Similarly, fragmentation according to reaction 15 has been observed in disaccharides49,52 and cyclo-hexa- and -hepta-amy-loses.50... 

Non-mutant normal) reserve and transitory starch granules are composed primarily of amylose and amylopectin. Amy lose is essentially a linear polymer consisting of (1—4)-linked a-D-glucopyranosyl units. Amylopectin is a branched polymer of a-D-glucop-yranosyl units primarily linked by (1—>4) bonds with branches resulting from (1—6) linkages. Properties of these two major starch components are summarized in Table 3.1. 

Historically, chemical modification of starch was the first widely-investigated method for producing starch-based plastics. Attempts at forming cast films from starch or amy-lose showed that the properties were highly dependent on relative humidity the films became brittle at low humidities.4 Figure 19.2 shows data for films of various amylose/ amylopectin ratios conditioned at 50% relative humidity and 23°C. Efforts to overcome... 

Starch Amy lose Amylopectin Proteins Organic acids Citric acid Malic acid Succinic acid Fumaric acid Minerals... 

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