基于原子力显微图像和流变学特性的大豆种皮多糖构象分析

Conformational Analysis of Polysaccharide from Soybean Hull Based on Atomic Force Microscope and Rheological Properties

大豆种皮多糖(SHP)是从大豆种皮中分离纯化得到的高分子质量酸性多糖。采用原子力显微镜(AFM)观察大豆种皮多糖在溶液-云母片表面的表观形貌,探究多糖的构象特征,并通过流变学验证其构象结果。结果表明:质量浓度及离子强度显著影响大豆种皮多糖的AFM成像。随着大豆种皮多糖质量浓度的降低,多糖分子间的作用力减弱,水溶液中多糖形貌从密集堆积的条带状结构逐渐分散为网状、双链结构。0.5 mol/L KCl盐溶液中多糖形貌从交联紧密的凝胶网状结构逐渐分散为螺旋短棒状结构。离子强度对大豆种皮多糖的影响体现在多糖的螺旋紧密度上,大豆种皮多糖在水溶液中呈现伸展的柔性长链,而在0.5 mol/L KCl溶液中则为螺旋的刚性短链。SHP溶液静态流变分析验证了KCl的加入导致糖链间相互交联形成网络结构,溶液体系逐渐从流体状态转变为弱凝胶状态。

The polysaccharide of soybean hull(SHP)was a high molecular weight acidic polysaccharide isolated and purified from soybean hull.The atomic force microscopy(AFM)was used to observe the apparent morphology on the surface of solution-mica for exploring the advanced conformational characteristics of polysaccharides,and verified by rheology.The results showed that the mass concentration and ionic strength significantly affected the AFM imaging of SHP,and the images of molecular aggregation behavior of different morphological polysaccharides were obtained.The interaction between polysaccharides was weakened as the concentration decreased.The conformation of polysaccharides gradually dispersed from densely packed strip-like structures into branched,single-and double-stranded structures in aqueous solution,and a cross-linked gel network structure into a short spiral-like structure in 0.5 mol/L KCl solution.The effects of ionic strength on SHP were reflected in the tightness of polysaccharide,and the conformation transformed from a stretched flexible long chain to a helical rigid short chain.By static rheological measurement of SHP solution,it was verified that the addition of KCl led to the cross-linking of polysaccharides chains to form a network structure,and the solution system gradually changed from a fluid state to a weak gel state.