Linear dextrins

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... 

Besemer, A.C. and van Bekkum, H., The catalytic effect of bromide in the hypochlorite oxidation of linear dextrins and inulin, Starch/Starke, 46, 101-106, 1994c. 

Isoamylase is used primarily in the production of food ingredients from starch (e.g. glucose syrup, maltose and maltitol, trehalose, cyclodextrins and resistant starch). It is typically used in combination with other amylolytic enzymes, such as a-amylase, p-amylase and glucoamylase, which further degrade the linear dextrins that arise from the debranching activity of isoamylase. The recommended use levels range from 50 to 5000 lAU/g starch. 

Mild acidic hydrolysis (5mM HCl at 100 C) of cyclohepta-amylose gave an 8% yield of maltoheptaose. The first-order rate constant increased during hydrolysis because the a-(l - 4)-linkages of cyclohepta-amylose and linear dextrins are cleaved at different rates. Various thermodynamic parameters and the dependence of the rate of hydrolysis on pH and on complexation of cyclohepta-amylose with toluene were determined. 

The cyclisation reaction of linear malto-oligosaccharides into a, p and y-cyclodextrins (CD) and the coupling reaction which leads to modified linear dextrins on the reducing end are special disproportionation reactions. 

The incubation of modified maltosyl fluorides confirmed some features already reported in the literature/ but also bring some new information about the specificity of the active site of CGTase. The amino acids of sxabsites T and U do not establish essential bondings with primary hydroxyls of maltosyl residues. On the donor part/ the subsite S does not accept any modification of these positions, but R is less specific. The same specificity was also found in Taica-amylase (11) and was confirmed when linear dextrins from the condensation of 6 -O-methyl-maltosyl fluoride were incubated with Ta)ca-amylase to afford 6 -0-methyl-maltose. 

While there has been sustained research on the solution properties of amylose, the solution behavior of linear dextrins has been less Investigated. For these molecules light scattering studies become more difficult as the Intensity of the light scattered by the dextrin is much less than that of the macromolecule. Viscometric studies have, however, been performed both on dilute and concentrated solutions. For the dilute solutions It Is possible to obtain by extrapolation values of the Intrinsic viscosity. One approach (44-46) to Interpreting this value is to consider the dextrin as a particle Immersed In a continuous fluid. 

Linear Dextrins. Both linear and cyclic maltodextrins in aqueous solution can form molecular complexes with other small molecules, possibly the most commonly known example being the blue... 

The high enthalpy water theory may explain, at least in part, the reason why cyclodextrins tend to have higher affinities for guest molecules than do linear dextrins. Another reason may be that of strain relaxation within cyclodextrin molecules. Saenger has suggested (g6) that in a cyclodextrin the uncomplexed molecule is in a slightly strained conformation due to rotation of one of the... 

Based on the experimental data on vinylidene chloride pofynerization in the presence of linear dextrin, a chemical interaction between poly(vinylidene chloride) and p-cyclodextrin was ruled out The results of the experiments demonstrated an absence of a chain transfer to linear dextrin, i.e. an absence of chemical bonds. In addition, comparing the data of investigation of the structure of obtained compounds indicated a nonchemical bonding of p-cyclodextrin and poly(vinylidene chloride). Due to the identity of the crystalline structure of monomeric adducts of P-cyclodextrin with both MMA and vinylidene chloride, on the one hand, and to the formation of an unstable product by a solid-state polyn rization of p-cyclodextrin with MMA (dissociates into P-cyclodextrin and PMMA on being treated with hot water), on the other hand, these researchers also assumed an absence of chemical bonds in the stable product, obtained in the same way and consisting of poly(vinylidene chloride) and p-cyclodextrin. 

It has been demonstrated - that in the conversion of amylose to amylopectin, the linear dextrin must reach a certain size before the Q-enzyme is able to act on it. The dextrin must contain at least 42 glucose units before it can be attacked by the enzyme. 

FIGURE 3.3 Chemical structure of the main soluble sugars found in cereal grains, (a) Glucose, (b) Fructose, (c) Sucrose, (d) Maltose, (e) Maltotriose. (f) Linear dextrin, (g) Branched dextrin. 

Cyclodextrin glycosyltransferase Enzymes that cleave starch and cyclize linear dextrins into a cyclodextrin ring. 

Dextrin A short-chain polysaccharide of glucose units linked with a-1,4 (linear dextrin) and a-l,6-glycosidic bonds (branched dextrins) formed during the breakdown of starch. 

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