High-Precision Megahertz-to-Terahertz Dielectric Spectroscopy of Protein Collective Motions and Hydration Dynamics
High-Precision Megahertz-to-Terahertz Dielectric Spectroscopy of Protein Collective Motions and Hydration Dynamics
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DOI：
10.1021/acs.jpcb.8b02872
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发表时间：
2018-06-21
影响因子：
3.3
通讯作者：
Vinh, Nguyen Q.
中科院分区：
文献类型：
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作者：
Charkhesht, Ali;Regmi, Chola K.;Vinh, Nguyen Q.
蛋白质中的低频集体振动模式以及蛋白质-水界面已被认为是控制生物化学反应和生物能量传输效率的主导因素。因此，至关重要的是要揭开神秘的水合结构和动力学，以及它们的耦合到集体运动的蛋白质在水溶液中。在这里，我们报告的介电性能的水溶液牛血清白蛋白的蛋白质溶液作为一个模型系统，使用一个非常敏感的介电光谱仪的频率从兆赫到太赫兹。介电弛豫谱揭示了分子水平上具有不同时间常数和介电强度的几种极化机制，反映了蛋白质-水相互作用的复杂性。结合有效介质近似和分子动力学模拟，我们已经确定了太赫兹频率的集体振动模式和紧密结合和松散结合的水合层中的水分子的数量。对水合水分子数量的高精度测量表明，蛋白质的动力学影响超出了第一溶剂化层，达到距离蛋白质表面约7埃的距离，其中最大的减速来自直接与蛋白质氢键结合的水分子。我们的研究结果揭示了蛋白质动力学和蛋白质-水界面的关键信息，这些信息决定了蛋白质的生化功能和反应性。
The low-frequency collective vibrational modes in proteins as well as the protein-water interface have been suggested as dominant factors controlling the efficiency of biochemical reactions and biological energy transport. It is thus crucial to uncover the mystery of the hydration structure and dynamics as well as their coupling to collective motions of proteins in aqueous solutions. Here, we report dielectric properties of aqueous bovine serum albumin protein solutions as a model system using an extremely sensitive dielectric spectrometer with frequencies spanning from megahertz to terahertz. The dielectric relaxation spectra reveal several polarization mechanisms at the molecular level with different time constants and dielectric strengths, reflecting the complexity of protein-water interactions. Combining the effective-medium approximation and molecular dynamics simulations, we have determined collective vibrational modes at terahertz frequencies and the number of water molecules in the tightly bound and loosely bound hydration layers. High-precision measurements of the number of hydration water molecules indicate that the dynamical influence of proteins extends beyond the first solvation layer, to around 7 angstrom distance from the protein surface, with the largest slowdown arising from water molecules directly hydrogen-bonded to the protein. Our results reveal critical information of protein dynamics and protein-water interfaces, which determine biochemical functions and reactivity of proteins.