Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro City, Tokyo 153-8505, Japan.
Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Bunkyo-ku, Tokyo 113-0033, Japan.
J Phys Chem B. 2023 Feb 16;127(6):1376-1384. doi: 10.1021/acs.jpcb.2c07405. Epub 2023 Feb 7.
Water rotational dynamics in biomolecular solution is crucial to evaluating and controlling biomolecule stability. In this molecular dynamics simulation (MD) study on lysozyme solutions, we present how the exerted internal electric field determines water rotational dynamics. We find that the relaxation time of water rotation is equivalent to that of the reorientation of the exerted overall electric field for every single water molecule, regardless of its translation mode. Namely, water molecular rotation synchronizes with the exerted field reorientation. We also map the reorientation process of the electric field at fixed points relative to protein in the solution, which displays the local hydration dynamics commensurate with the reported time-dependent fluorescence Stokes shift (TDFSS) measurements. Comparing the spatial distribution of local field reorientation relaxation time with that of rotational relaxation time, we further suggest that water rotation dynamics are subject to the reorientation of the local overall field within the hydration layer. While outside the hydration layer, the relaxation time of the local electric field reorientation is short enough (subpicosecond) to assume the δ function, showing the electric force with randomly changing orientation is applied to each water molecule.
生物分子溶液中的水转动动力学对于评估和控制生物分子稳定性至关重要。在这项关于溶菌酶溶液的分子动力学模拟 (MD) 研究中，我们展示了外加内部电场如何决定水的转动动力学。我们发现，无论单个水分子的平移模式如何，水的旋转弛豫时间都等同于外加总电场的重新取向时间。也就是说，水分子的旋转与外加场的重新取向同步。我们还绘制了相对于溶液中蛋白质的固定点处电场的重新取向过程，该过程显示了与报道的时间依赖荧光斯托克斯位移 (TDFSS) 测量结果一致的局部水合动力学。通过比较局部场重新取向弛豫时间的空间分布与旋转弛豫时间的空间分布，我们进一步表明水的旋转动力学受水合层内局部总场的重新取向控制。而在水合层之外，局部电场重新取向的弛豫时间足够短（亚皮秒），可以假设为 δ 函数，表明每个水分子都受到方向随机变化的电场力的作用。
