Modeling of the 3D structure of the cluster of amylopectin

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For modeling of branched structure of amylopectin, analytical methods have been developed to gain insights to the branched structure.1.Various conditions for determination of molecular- weight distribution of amylopectin were examined using HPSEC system equipped with a differential refractometer and a fluorescent detector. Amylopectin was separated into two major fractions based on the fluorescence detection while eluted as a single peak by detection with refractive index.2.A method was established for determination of chain-length distribution of β-amylase limit dextrin (β-LD) of amylopectin. The method revealed that the distributions of various amylopectins were characteristic by their botanical sources. The results also suggested relationship between the chain-length distribution and x-ray diffraction patterns of starch granules. Successive hydrolysis of amylopectin with phosphorylase and β-amylase was attempted for preparation of corresponding limit dextrin (Φ,β-LD), which was then subjected to determination of chain-length distribution. The results obtained with Φ,β-LD were consistent with those with β-LD, that is, branched structure of amylopectin is related to starch granules' crystalline structure.3.Models of branched structures of amylopectins from starches of A- and B-type crystalline were constructed, based on the information obtained in this study, such as number of side chains per a given unit-chains, internal chain-length, interval between two branch points. Respective model for A- or B-type showed distinct features in terms of branching in a cluster structure, indicating that the branching characteristics within a cluster unit, as well as average chain-length of the unit, have influence on determination of the higher-order, crystalline structure.