Comparison of curdlan and its carboxymethylated derivative by means of Rheology, DSC, and AFM
Comparison of curdlan and its carboxymethylated derivative by means of Rheology, DSC, and AFM
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通过流变学、DSC 和 AFM 比较凝胶多糖及其羧甲基化衍生物
DOI：
10.1016/j.carres.2005.11.003
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发表时间：
2006-01-16
影响因子：
3.1
通讯作者：
Nishinari, K
中科院分区：
文献类型：
--
作者：
Jin, Y;Zhang, HB;Nishinari, K
以一氯乙酸为醚化剂，在碱性水溶液中进行羧甲基化。通过红外光谱（FT-IR）和核磁共振光谱（NMR）对羧甲基化凝乳蛋白（CMc）的结构进行了分析，结果表明羧甲基主要在C-6位点以及C-2和C-4位点引入。利用流变学和DSC方法对CMc与天然凝乳进行了比较。结果表明，两种多糖在水中均表现为假塑性流体，符合幂律和Herschel-Bulkley流变模型。CMc水溶液的储存剪切模量G′和损失剪切模量G′均随浓度的降低而减小，且频率依赖性更强。模量-温度曲线也表明，化学改性后凝乳蛋白失去了凝胶特性，这与DSC结果一致。AFM图像显示天然凝乳蛋白和羧甲基化凝乳蛋白的构象存在差异，从大分子聚集变为三螺旋结构。实验结果表明，胶凝蛋白与间隙水形成胶束的氢键被完全破坏，55℃以上形成的C-6亚甲基的疏水相互作用由于亲水性羧基的引入而消失。(c) 2005 Elsevier Ltd版权所有。
Curdlan was carboxymethylated in an aqueous alkaline medium using monochloroacetic acid as the etherifying agent. The structure of carboxymethylated curdlan (CMc) was analyzed by FT-IR and NMR spectroscopy, which revealed that the carboxymethyl group was introduced mainly at the C-6 position as well as at the C-2 and C-4 positions. Furthermore, CMc was compared with the native curdlan by using rheology and DSC methods. It was found that in water, both polysaccharides behaved as pseudoplastic fluids and fit the power law and Herschel-Bulkley rheological models well. Both the storage shear modulus G' and the loss shear modulus G' of CMc aqueous solutions decreased and became more frequency dependent with decreasing concentration in comparison with the curdlan aqueous suspensions. The modulus-temperature curve also suggested that the gel characteristic of curdlan has been lost after chemical modification, which is consistent with the DSC results. AFM images revealed differences in the conformation of native and carboxymethylated curdlan, which changed from the aggregation of macromolecules to triple helices. All the experimental results suggest that the hydrogen bonds that bind curdlan with interstitial water to form the micelles have been destroyed completely and that the hydrophobic interactions related to the methylene groups at C-6 formed above 55 degrees C disappeared due to the introduction of the hydrophilic carboxymethyl group. (c) 2005 Elsevier Ltd. All rights reserved.