定优胶在水溶液中的构象转变  

Conformational Transition of Diutan Gum in Aqueous Solutions

作　　者：梁珂 苏鑫[1] 冯玉军[1] Ke Liang;Xin Su;Yujun Feng(State Key Laboratory of Polymer Materials Engineering,Polymer Research Institute,Sichuan University,Chengdu 610065,China)

机构地区：[1]高分子材料工程国家重点实验室四川大学高分子研究所

出　　处：《高分子材料科学与工程》2019年第9期40-46,共7页Polymer Materials Science & Engineering

基　　金：国家自然科学基金资助项目(21773161,U1762218);高分子材料工程国家重点实验室开放基金(sklpme2014-2-06)

摘　　要：定优胶为菌种需氧发酵产生的生物多糖,迄今为止,仍未有关于定优胶在水溶液中的链构象转变的研究。文中采用圆二色谱与光散射初步研究了定优胶在水溶液中的链构象,利用超灵敏差示扫描微量热仪与流变仪研究了温度、极性溶剂二甲基亚砜(DMSO)与强碱NaOH对定优胶分子链构象的影响。结果表明,定优胶在水溶液中为通过氢键来维持的刚性棒状螺旋构象,高温、极性溶剂及NaOH皆能破坏氢键作用,促使螺旋结构转变为无规分子链。在100℃左右时,定优胶双螺旋结构发生解旋;高含量的DMSO将破坏定优胶的双螺旋结构;在研究的NaOH浓度范围内(0~0.3 mol/L),部分定优胶分子链发生构象转变。故定优胶溶液具备优异的耐热、耐强碱的性能,在极性溶剂中也有良好的稳定性。As a microbial extracellular polysaccharide produced by aerobic fermentation of bacteria, the solutions behavior and conformation of diutan gum have not been studied systematically enough. Circular dichroism(CD) and light scattering were used to determine the conformation of diutan gum in aqueous solutions. Ultra-sensitive differential scanning calorimetry(DSC), atomic force microscope(AFM) and rheology were performed to research the effect of temperature, polar solvent(dimethyl sulfoxide, DMSO) and NaOH on the molecular chain conformation of diutan gum. The results of light scattering and CD indicate that diutan gum exhibits rigid rod-like helical conformation in aqueous solutions, and the rigid molecular chains can further aggregate to form helix aggregates. The helix structure of diutan gum mainly is stabilized by hydrogen bonds;but, some external factors, like heating, DMSO and NaOH can destroy these hydrogen bonds, changing the ordered double helix structure of diutan gum to random coil. By ultra-sensitive DSC, it is found that diutan gum owns a high unscrewed temperature around 100 ℃.The results of dynamic rheology and AFM show that high concentration of DMSO would destroy the double helix structure of diutan gum. Within the range of NaOH concentrations studied, the conformation of diutan gum is less affected. To sum up, diutan gum exhibits stable rod-like helix structure in aqueous solutions;diutan gum could undergo conformation transition only with high temperature, high content of DMSO or high concentration of NaOH solution. In other words, diutan gum possesses excellent thermal stability, also with good stability to alkali and DMSO.

关 键 词：定优胶 链构象 棒状螺旋结构 构象转变 氢键 

分 类 号：O631.4[理学—高分子化学]