STUDIES ON THE GELATION MECHANISM OF POLYSACCHARIDES

1)用流变仪和旋光仪研究了植物病原菌野油菜黄单胞菌(Xanthomonas Campestris)产生的黄原胶多糖的流变特性。提出了黄原胶分子内缔合的可能模式。还提出了黄原胶与半乳甘露聚糖(蝗虫豆胶)之间D-甘露糖特异性相互作用的可能结合部位。黄原胶与塔拉豆胶和魔芋葡甘露聚糖混合物(天然、脱乙酰化、脱丙基、脱酰化)和魔芋葡甘露聚糖的流变学特性与刺槐豆胶混合物的流变性基本一致，支持黄原胶与刺槐豆胶在水溶液中可能的缔合部位。胞外细菌多糖黄原胶与植物细胞壁典型的半乳甘露聚糖和葡甘聚糖组分之间的相互作用可能在宿主-病原菌关系中发挥作用，并可能利用…提供D-甘露糖特异结合位点的存在威兰和鼠李糖热稳定性的分子起源，其结构类似于结冷胶在水溶液中形成的硬而脆的凝胶，可能归因于分子内缔合。提出了D-葡萄糖残基的OH-4与L-鼠李糖残基的半缩醛氧原子、L-鼠李糖残基的甲基与D-葡萄糖基残基的半缩醛氧原子之间可能的分子内缔合方式。3)钙离子存在下海藻酸盐凝胶形成的分子根源可能是分子内的氢键和钙桥，以及水溶液中分子间的钙桥。4)凝胶形成的分子来源可能是分子内和分子间的氢键。提出了分子内和分子间相互作用的可能模式。在高温下可能发生疏水相互作用，并提出了疏水相互作用的模式。较少

1) The molecular basis for the rheological characteristics of xanthan gum, a polysaccharide produced by the plant pathogen Xanthomonas campestris, was studied using a rheogoniometer and polarimeter. Possible mode of intramolecular associations in xanthan molecules were proposed. Possible binding sites for D-mannose-specific interaction between xanthan and galactomannan (locust-bean gum) have also been proposed. The rheological characteristics of a mixture of xanthan (native, deacetylated, depyruvated, and deacylated) with tara-bean gum, and with konjac glucomannan agreed with those in the mixture with locust-bean gum, and supported the possible association sites between xanthan and locust-bean gum in aqueous solution. The interaction between the extracellular bacterial polysaccharide xanthan and typical galactomannan and glucomannan components of the plant cell wall may play a part in the host-pathogen relationship, and may provide the existence of D-mannose-specific binding sites used … More for cell recognition by the pathogen.2) Molecular origin for thermal stability of welan and rhamsan, the structure of which are similar to that of gellan gum which formed a stiff, brittle gel in aqueous solution, might be attributed to the intramolecular associations. Possible mode of intramolecular association between the OH-4 of the D-glucosyl residue and the adjacent hemiacetal oxygen atom of the L-rhamnosyl residue, and between the methyl group of the L-rhamnosyl residue and the adjacent hemiacetal oxygen atom of the D-glucoslyl residue were proposed.3) The molecular origin for gel-formation of alginate in the presence of Ca^<2+> might be attributed to the intramolecular hydrogen bonding and Ca-bridge, and to the intermolecular Ca-bridges in aqueous solution. Possible mode of intramolecular hydrogen bonding and Ca-bridge, and intermolecular Ca-bridges were proposed.4) The molecular origin for gel-formation of curdlan might be attributed to the intra- and intermolecular hydrogen bonding. Possible mode of intra- and inter-molecular associations within and between curdlan molecules were proposed. An hydrophobic interaction might take place at high temperature, the mode of which was also proposed. Less