Diffusion of sucrose and α,α-trehalose in aqueous solutions
Diffusion of sucrose and α,α-trehalose in aqueous solutions
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DOI：
10.1021/jp020187b
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发表时间：
2003-02-13
影响因子：
2.9
通讯作者：
von Meerwall, E
中科院分区：
文献类型：
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作者：
Ekdawi-Sever, N;de Pablo, JJ;von Meerwall, E
采用脉冲梯度自旋回波核磁共振法测量了蔗糖和海藻糖在水溶液中的扩散系数，并采用分子动力学模拟计算了扩散系数。蔗糖和海藻糖的扩散系数在低二糖浓度下相当，但随着浓度的增加和温度的降低而彼此不同。在400 K和本研究中考虑的最高二糖浓度（80 wt %）下，模拟海藻糖扩散系数比蔗糖小3.5倍（分别为2.6 x 10（-8）cm（2）/s和9.3 x 10（-8）cm（2）/S）。在74wt%的二糖溶液中，海藻糖的实验扩散系数比蔗糖在358 K时的小3倍。水的扩散系数比二糖的扩散系数大至少1个数量级。在这里考虑的最高二糖溶液中，这种差异增加到2个数量级。水和二糖运动的解耦归因于两种分子所采用的不同扩散机制。模拟结果表明，在高二糖浓度，二糖的扩散出现连续的，而水的随机跳跃，然后由周围的分子创建的瞬态笼内的快速振动。
Diffusion coefficients for sucrose and trehalose in aqueous solutions were measured using pulsed-gradient-spin-echo NMR and calculated using molecular dynamics simulations. The diffusion coefficients of sucrose and trehalose are comparable at low disaccharide concentrations but differ from each other with increasing concentration and decreasing temperature. At 400 K and the highest disaccharide concentration considered in this work (80 wt %), the simulated trehalose diffusion coefficient is a factor of 3.5 smaller than that of sucrose (2.6 x 10(-8) cm(2)/s and 9.3 x 10(-8) cm(2)/S, respectively). In a 74 wt % disaccharide solution, the experimental diffusion coefficient for trehalose is a factor of 3 smaller than that of sucrose at 358 K. The diffusion coefficients of water are at least 1 order of magnitude larger than those of the disaccharides. This difference increases to 2 orders of magnitude at the highest disaccharide solutions considered here. The decoupling of the water and disaccharide motion is attributed to the different diffusion mechanisms adopted by the two molecules. Simulations reveal that, at high disaccharide concentrations, the diffusion of the disaccharides appears continuous while that of water consists of random jumps followed by rapid vibrations within transient cages created by surrounding molecules.