Dextrins from, structure

B-chains until they are acted on by R-enzyme, when maltose or malto-triose will be produced from the residual A-chain, and linear dextrins from the B-chains. The amount of maltose or maltotriose liberated on treating the /3-limit dextrin with R-enzyme will be a measure of the number of A-chains in the molecule, and from these data, the ratio of A B chains in the molecule can be calculated.220 Peat concluded that multiple branching is an intrinsic part of the amylopectin structure, as the observed yield of these sugars was greater than expected for a singly-branched structure. It should be noted that glycogen has been shown by similar enzymic methods to possess a truly random structure.221... 

Yusuph, M., Tester, R. F., Ansell, R., Snape, C. E. (2003). Composition and properties of starches extracted from tubers of different potato varieties grown under the same environmental conditions. Food Chem., 82,283-289. Zhu, Q., Bertoft, E. (1996). Composition and structural analysis of alpha-dextrins from potato amylopectin. Carbohydr. Res., 288, 155-174. 

Believing that the chemical modification of natural biopolymers could produce materials having many of the physical properties desired for technical applications, he pursued structural studies of synthetic gums, such as the dextrins from pyrolysis of starch (with G. M. Christensen,... 

However, evidence in favor of a true structural feature that resists the action of fcefa-amylase has come from studies of the action of debranching enzymes on amylose and its hefa-limit dextrin. Thus, by treatment with yeast isoamylase, the befa-amylolysis limit of a sample of amylose was increased from 76 to 90 , and that of amylose 6e a-limit dextrin from 6 to 77 . Treatment of amylose with pullulanase also increases the conversion of the substrate into maltose by befa-amylase to an almost quantitative value. " On the basis of these results, the anomalous linkages in amylose that resist beto-amylase action are considered to be a very small proportion of (l->6)-a-D-glucosidic linkages. 

Macerans amylase produces other cyclic dextrins from starch in low yields (11). These dextrins have been isolated and preliminary structural data have been obtained. These data indicate that the dextrins are composed of 9 to 12 glucose units some of which form a cyclic ring and have oligosaccharide side Chains linked by a-D-(l,6) bonds to the residues of the core. However, the complete structures of the new dextrins have not yet been determined. 

The only example of this technique applied to the amylose component is that already described, of the action of Z-enzyme on the /3-limit dextrin. In the case of amylopectin, enzymic methods enable a distinction to be made between the proposed laminated and highly ramified structures (I and III, in Fig. 1, page 352). The method used by Peat and coworkers101 involves the successive action of /3-amylase and R-enzyme on waxy maize starch. /3-Amylolysis will degrade A-chains down to two or three units from the 6 —> 1-a-D interchain linkages. These latter linkages will protect the... 

While nature uses coenzyme-dependent enzymes to influence the inherent reactivity of the coenzyme, in principle, any chemical microenvironment could modulate the chemical properties of coenzymes to achieve novel functional properties. In some cases even simple changes in solvent, pH, and ionic strength can alter the coenzyme reactivity. Early attempts to present coenzymes with a more complex chemical environment focused on incorporating coenzymes into small molecule scaffolds or synthetic host molecules such as cyclophanes and cyclo-dextrins [1,2]. While some notable successes have been reported, these strategies have been less successful for constructing more complex coenzyme microenvironments and have suffered from difficulties in readily manipulating the structure of the coenzyme microenvironment. 

Prior to 1939, however, it was not known whether the cyclodextrins were products of the synthetic metabolism of Bacillus macerans, and therefore, perhaps, quite different from the components of starch, or whether they were formed by a single enzyme and therefore closely related to the starch structure. Then, Tilden and Hudson announced the discovery of a cell-free enzyme preparation from cultures of Bacillus macerans which had the ability to convert starch into the Schardinger dextrins without the production of maltose, glucose, or any other reducing sugars. They thus concluded that the Schardinger dextrins were either the true components of starch or closely related to such true components. 

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