车前子来源阿拉伯木聚糖溶液构象表征及计算机分子模拟

Three dimensional structure and conformation of polysaccharide in solution have great effects on its bioactivities. It is significant to elucidate the relationship between polysaccharide structure and its conformational characteristics clearly and scientifically. Plantain seeds could be both used as medicine and food, and are rich in polysaccharide of arabinoxylan. However, previous researches could not explain the gut health improving bioactivities of the polysaccharide from structural and conformational aspects. Seeds of Plantago asiatica L. are widely sown in Ji’an and Yi’chun rural areas in Jiangxi Province. According to previous studies in our lab, polysaccharide from seeds of Plantago asiatica L., mainly consisted of arabinose and xylose, is to be subjected for analysis in this research. Polysaccharide primary chain or branched chain is hydrolyzed by special enzyme or other methods to get sub-fractions, which would be purified if necessary. Then, HPSEC, dynamic and static light scattering and atomic force microscope are applied to characterize the polysaccharides conformational properties. Their fine structure are determined by currently structural characterization methods of polysaccharide, such as methylation, partial acid hydrolysis and NMR, etc. According to changes of polysaccharide in structure and conformation before and after degradation, effects of primary chain or branched chain on conformational characteristics of the polysaccharide would be concluded. Finally, molecular simulation by computer is applied to construct polysaccharide structure, and the conformation characteristics would be calculated and obtained. This research is aimed at acquiring useful information of relationship between structure and conformational characteristics of arabinoxylan from Plantain seeds. Results would help us to understand mechanism of the polysaccharide in improving gut health from structural and conformational aspects. At the same time, the system of analyzing methods would also guide researches on structural and conformational analysis of polysaccharide from other resources.

多糖在溶液中的空间三维结构和构象对其生物功能有重要影响，科学阐明多糖结构与溶液构象对应关系具有很强的科学意义。车前子属于药食两用资源，富含阿拉伯木聚糖，但其发挥良好肠道功能活性的物质结构、构象基础还不清楚。江西省吉安、宜春盛产大粒车前子，本课题拟在前期研究基础上，以大粒车前子多糖为研究对象，通过酶法水解等技术特异性水解多糖主链或支链，获得降解后多糖片段，利用HPSEC、动静态光散射仪、原子力显微镜结合现代多糖结构表征方法解析多糖构象、结构特征，通过比较水解前后车前子多糖结构、构象变化，分析多糖主链、支链结构对其构象特征的影响。并利用计算机分子模拟技术构建上述多糖，模拟计算构象参数。通过本研究，将构建信息较为齐全的车前子来源阿拉伯木聚糖的结构和溶液构象特征对应关系数据库，从而为从结构、构象角度探讨车前子多糖肠道功能活性的物质基础提供数据参考，同时也为其他来源多糖的结构与构象关系研究提供借鉴。

多糖在溶液中的空间三维结构和构象对其生物功能有重要影响，阐明多糖结构与溶液构象对应关系具有很好的科学意义。本课题在前期研究基础上，以大粒车前子多糖为研究对象，通过三氟乙酸水解、草酸水解等技术降解多糖，获得降解后多糖片段，利用HPSEC、原子力显微镜结合现代多糖结构表征方法探索多糖结构对其构象特征的影响，并利用计算机模拟技术进行验证。典型的大粒车前子多糖为阿拉伯木聚糖类多糖，主链由β-1,4-linked Xylp构成，高度分支化，阿拉伯糖分布在其侧链上。大粒车前子多糖呈现明显的半柔顺、线性链构象特征，侧链基团对多糖链的刚性强度有重要影响，减少侧链取代基团将增强车前子阿拉伯木聚糖链的刚性强度。进一步结合计算机模拟技术，发现阿拉伯糖侧链的分支位置对多糖构象性质有很大影响，当主链β-1,4-Xylp残基上的O-2或者O-2、O-3同时发生取代时，能显著降低阿拉伯木聚糖链的刚性强度；当主链β-1,4-Xylp残基上的O-2、O-3同时发生取代时，Ara残基数量越多，阿拉伯木聚糖的刚性结构越弱。通过本研究，构建了信息较为齐全的车前子来源阿拉伯木聚糖的结构和溶液构象特征对应关系数据，从而为阿拉伯木聚糖类多糖的结构与构象关系研究提供借鉴。