Joti Yasumasa, Nakagawa Hiroshi, Kataoka Mikio, Kitao Akio
Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
Biophys J. 2008 Jun;94(11):4435-43. doi: 10.1529/biophysj.107.118042. Epub 2008 Feb 29.
Hydration effects on protein dynamics were investigated by comparing the frequency dependence of the calculated neutron scattering spectra between full and minimal hydration states at temperatures between 100 and 300 K. The protein boson peak is observed in the frequency range 1-4 meV at 100 K in both states. The peak frequency in the minimal hydration state shifts to lower than that in the full hydration state. Protein motions with a frequency higher than 4 meV were shown to undergo almost harmonic motion in both states at all temperatures simulated, whereas those with a frequency lower than 1 meV dominate the total fluctuations above 220 K and contribute to the origin of the glass-like transition. At 300 K, the boson peak becomes buried in the quasielastic contributions in the full hydration state but is still observed in the minimal hydration state. The boson peak is observed when protein dynamics are trapped within a local minimum of its energy surface. Protein motions, which contribute to the boson peak, are distributed throughout the whole protein. The fine structure of the dynamics structure factor is expected to be detected by the experiment if a high resolution instrument (< approximately 20 microeV) is developed in the near future.
通过比较在100至300 K温度范围内完全水合状态和最小水合状态下计算得到的中子散射光谱的频率依赖性，研究了水合作用对蛋白质动力学的影响。在两种状态下，于100 K时均在1 - 4 meV频率范围内观察到蛋白质玻色子峰。最小水合状态下的峰频率向低于完全水合状态下的峰频率移动。在所有模拟温度下，频率高于4 meV的蛋白质运动在两种状态下几乎都经历简谐运动，而频率低于1 meV的运动在220 K以上主导总波动并促成类玻璃转变的起源。在300 K时，玻色子峰在完全水合状态下被准弹性贡献掩盖，但在最小水合状态下仍可观察到。当蛋白质动力学被困在其能量表面的局部最小值内时，会观察到玻色子峰。对玻色子峰有贡献的蛋白质运动分布在整个蛋白质中。如果在不久将来开发出高分辨率仪器（<约20微电子伏特），有望通过实验检测到动力学结构因子的精细结构。
