STUDIES ON THE GELATION MECHANISM OF POLYSACCHARIDES

1)利用流变仪和偏振仪研究了植物病原菌黄单胞菌（Xanthomonas campestris）产生的多糖黄原胶流变特性的分子基础。提出了黄原胶分子内缔合的可能模式。黄原胶和半乳甘露聚糖（蝗虫豆胶）之间d -甘露糖特异性相互作用的可能结合位点也被提出。黄原胶（原生、去乙酰化、脱丙酮化和去乙酰化）与魔芋葡甘露聚糖的混合物的流变特性与与槐豆胶的混合物的流变特性一致，并支持黄原胶与槐豆胶在水溶液中可能存在的关联位点。胞外细菌多糖黄原原与植物细胞壁上典型的半乳甘露聚糖和葡甘露聚糖组分之间的相互作用可能在宿主-病原体关系中起作用，并可能提供d -甘露聚糖特异性结合位点的存在，用于病原体对细胞的识别。2)与结冷胶结构相似，结冷胶在水溶液中形成坚硬、易碎的凝胶，其热稳定性的分子来源可能与分子内缔合有关。提出了d -葡萄糖基残基的OH-4与l -鼠李糖基残基的邻半缩醛氧原子、l -鼠李糖基残基的甲基与d -葡萄糖基残基的邻半缩醛氧原子之间可能的分子内缔合模式。3) Ca^<2+>存在下海藻酸盐凝胶形成的分子来源可能是分子内氢键和Ca桥，以及水溶液中的分子间Ca桥。提出了分子内氢键、钙桥和分子间钙桥的可能模式。4)凝乳素凝胶形成的分子来源可能是分子内和分子间的氢键作用。提出了凝乳蛋白分子内部和分子间结合的可能模式。在高温下可能发生疏水相互作用，并提出了其模式。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