Modeling of the 3D structure of the cluster of amylopectin

为了模拟支链淀粉的支化结构，人们发展了各种分析方法来了解支链淀粉的支化结构。1.利用配有差示折射仪和荧光检测器的HPSEC系统，研究了测定支链淀粉分子量分布的各种条件。采用荧光检测法将支链淀粉分离为两个主要组分，折射率检测法将支链淀粉洗脱成单峰。2.建立了支链淀粉β-淀粉酶极限糊精(β-LD)的链长分布测定方法。该方法揭示了不同支链淀粉的分布具有植物来源的特点。实验结果还揭示了淀粉颗粒的链长分布与X-射线衍射谱之间的关系。尝试用磷酸化酶和β-淀粉酶连续水解支链淀粉制备相应的极限糊精(Φ，β-LD)，并对其链长分布进行了测定。用Φ，β-LD和β-LD得到的结果是一致的，即支链淀粉的支化结构与淀粉颗粒的结晶结构有关。3.根据本研究获得的每一单位链上支链的数目、内部链长、两个支点之间的间隔等信息，构建了A、B型结晶淀粉支链的支化结构模型。A型和B型模型在团簇结构中表现出不同的支化特征，表明团簇单元内的支化特征以及单元的平均链长对确定更高级别的晶体结构有影响。

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.