Structure of Amylose

Almost all the starches investigated contain some phosphorus.124-126 In addition to phospholipids, phosphorus is also commonly found in starch as monostarch phosphate esters.6,7 Inorganic phosphate is present in some starches.124-126 Monostarch phosphate esters and phospholipids have different effects on starch paste properties.133,135 Monostarch phosphate esters, found in potato, shoti and other starches,6,7,136-140 increase paste clarity and paste viscosity.79 Little phosphate monoester is found in cereal starch.121,124,141,142 Phospholipids, found in normal cereal starches (e.g. wheat, rice and maize) decrease paste clarity and viscosity.133 31P-nmr spectroscopy has 

Although all amylose molecules were once considered to be linear, many amylose molecules cannot be completely hydrolyzed by (3-amylase. With a concurrent or mixed action of pullulanase and beta-amylase, however, amylose can be completely hydrolyzed to maltose.150,151 These results rule out the theory that the incomplete hydrolysis of amylose by (3-amylase is a result of retrogradation, i.e. junction zone formation. It is now clear that the incomplete hydrolysis of an amylose preparation by (3-amylase is due to branching of some molecules. The (3-amylolysis limit of amylose varies from 72% to 95%152,153 compared with 55-61% for amylopectin. Amylose of most cereal starches, such as maize,154 rice,155,156 wheat157 and barley,158 give 80% (3-amylolysis 

Amyloses of different origins and molecular weights have been extensively studied.151 Results indicate that cereal amyloses are smaller than other amyloses. Amyloses isolated from high-amylose maize starches display substantially smaller molecular weights (average DP 690-740 and chain lengths 215-255).161 There is about an equal 

rice 25%).156,166 Maize and rice amyloses of the same molecular weight subtraction had similar structures. 

Using results of these kinds of studies, the characteristic structure of amylose can be differentiated from that of amylopectin. Amylose has a small number of branches and crystallizes and precipitates when complexed with 1 -butanol. The iodine affinity of amylose is much greater (i.a. 18.5 to 21.1) than that of amylopectin (i.a. 0.0 to 6.6),79,152-158,163,169-174 and the iodine affinity of amylose (3-limit dextrin is similar to that of the parent amylose. The average chain length of amylose (3-limit dextrins is much larger than that of the amylopectin (3-limit dextrin.160 

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Table III shows the results of chemical analyses of amylose samples compared, where possible, with values of Mn. These indicate the presence of more than one nonreducing, terminal group in some of the amylose samples. In the case of potato starch, this result is thought to be attributable to the presence of contaminating amylopectin rather than to inherent branching in the molecule.106 Other methods of examining the fine structure of amylose, and the question of branching, will be dealt with later (see p. 381).

The strict primer dependence of the glycogen phosphorylases makes them ideal candidates for the synthesis of hybrid structures of amylose with non-natural materials... 

Takeda, Y, Maruta, N., Hizukuri, S. (1992). Examination of the structure of amylose by tritium labelling of the reducing terminal. Carbohydr. Res., 227, 113-120. 

PrObtom 22.42 The polysaccharide amylose, the water-soluble component of starch, is hydrolyzed to ( + )-maltose and D-(-t-)-glucose, Methylated and hydrolyzed, amylose gives mainly 2,3,6-tri-O-methyl-D-glucopyranose. Deduce the structure of amylose. 4... 

FIGURE 1 Three-dimensional structures of amylose and cellulose polymers. 

The double-helical structures of native A- and B-amyloses are found in the fourth group. It is interesting that in both h as well as the d and dyg spacings, they are comparable with the structure of amylose triacetate I (ATAI). In part, this may arise because the packing of the bulky acetate substituents in ATAI is similar to the close-packing of two amylose chains into a double helix. In the latter, one chain may act as the "substituent" for the other chain. At any rate, all three structures contain similar, cylindrical-shaped helices. Somewhat unexpectedly, the distances cL and d-yo are very close for the two native polymorphs, even though their unit cells and packing are... 

All chapters/subjects that were also in the previous edition have been updated. Chapters have been added on the biochemistry and molecular biology of starch biosynthesis, structural transitions and related physical properties of starch, and cyclo-dextrins. There are two chapters on the structural features of starch granules that present not only advances in understanding the organization of starch granules, but also advances in understanding the fine structures of amylose and amylopectin, both of which are based on techniques that have been developed since 1984. 

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