Department of Biophysical Chemistry, Center for Molecular Protein Science, Lund University, SE-22100 Lund, Sweden.
J Phys Chem B. 2012 Aug 2;116(30):9196-207. doi: 10.1021/jp304982c. Epub 2012 Jul 18.
The disaccharide trehalose stabilizes proteins against unfolding, but the underlying mechanism is not well understood. Because trehalose is preferentially excluded from the protein surface, it is of interest to examine how trehalose modifies the structure and dynamics of the solvent. From the spin relaxation rates of deuterated trehalose and (17)O-enriched water, we obtain the rotational dynamics of trehalose and water in solutions over wide ranges of concentration (0.025-1.5 M) and temperature (236-293 K). The results reveal direct solute-solute interactions at all concentrations, consistent with transient trehalose clusters. Similar to other organic solutes, the trehalose perturbation of water rotation (and hydrogen-bond exchange) is modest: a factor 1.6 (at 298 K) on average for the 47 water molecules in the first hydration layer. The deviation of the solute tumbling time from the Stokes-Einstein-Debye relation is partly caused by a dynamic solvent effect that is often modeled by incorporating "bound water" in the hydrodynamic volume. By comparing the measured temperature dependences of trehalose and water dynamics, we demonstrate that a more realistic local viscosity model accounts for this second-order dynamic coupling.
海藻糖可以稳定蛋白质使其不发生变性，但其中的作用机制尚不清楚。由于海藻糖优先从蛋白质表面排除，因此研究海藻糖如何改变溶剂的结构和动态具有重要意义。通过氘代海藻糖和（17）O 富集水的自旋弛豫率，我们获得了在广泛浓度（0.025-1.5 M）和温度（236-293 K）范围内海藻糖和水在溶液中的旋转动力学。结果表明，在所有浓度下都存在直接的溶质-溶质相互作用，这与瞬态海藻糖簇一致。与其他有机溶质类似，海藻糖对水旋转（和氢键交换）的干扰适度：在第一层水合层的 47 个水分子中，平均为 1.6 倍（在 298 K 时）。溶质旋转时间偏离斯托克斯-爱因斯坦-德拜关系部分是由动态溶剂效应引起的，该效应通常通过在流体力学体积中包含“结合水”来建模。通过比较海藻糖和水动力学的测量温度依赖性，我们证明了更现实的局部粘度模型可以解释这种二级动态耦合。
