Modeling of the 3D structure of the cluster of amylopectin

对于支链淀粉支链结构的建模，已经开发了分析方法来深入了解支链淀粉的支链结构。采用配备差示折射仪和荧光检测器的高效液相色谱系统，考察了支链淀粉分子量分布测定的各种条件。支链淀粉通过荧光检测分离为两大部分，通过折射率检测洗脱为单峰。建立了支链淀粉β-淀粉酶极限糊精（β-LD）链长分布的测定方法。结果表明，各种支链淀粉的分布有其植物来源的特点。结果还表明了淀粉颗粒的x射线衍射模式与链长分布之间的关系。用磷酸化酶和β-淀粉酶连续水解支链淀粉，制备相应的极限糊精（Φ，β-LD），并测定其链长分布。用Φ、β-LD和β-LD得到的结果一致，即支链淀粉的支链结构与淀粉颗粒的结晶结构有关。基于本研究获得的单位链侧链数、内部链长、两个分支点之间的间隔等信息，构建了A型和b型淀粉支链淀粉的支链结构模型。A-型和b -型的模型在团簇结构的分支方面表现出明显的特征，这表明团簇单元内的分支特征以及单元的平均链长对高阶晶体结构的确定有影响。

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.