Studies of structural fluctuations of complex systems by transient hole-burning

我们开发的时间分辨光谱烧孔光谱是一种很好的方法，使我们能够直接观察各种材料在宽的温度和时间范围内的平衡构象波动。我们已经改进了这种方法的时间分辨率为10纳秒，并将其应用于红溴红染料和锌取代的肌红蛋白在水-甘油混合物。结果表明，在150-300 K温度范围内，空穴的重心随时间的变化可用一个展宽的指数函数表示，涨落的关联时间服从Vogel-Fulcher定律。与染料溶液相比，蛋白质溶液的时间行为更非指数，对温度的依赖性更弱。已经直接证明，蛋白质分子的构象动力学强烈依赖于其周围环境，并且蛋白质的玻璃化转变由溶剂的冻结控制。整体上所得到的结果已被发现是很好地解释了层次约束动力学模型。我们还比较了天然样和熔球样细胞色素c之间的构象动力学。此外，它已被证明，Qx和Qy带的肌红蛋白和细胞色素c，这是埋在非均匀加宽的吸收带的光谱形状，可以确定使用偏振光谱除了时间分辨光谱烧孔。

The time-resolved spectral hole-burning spectroscopy we have developed is an excellent method that enables us directly to observe the equilibrium conformational fluctuations in various materials over wide temperature and time ranges. We have improved the temporal resolution of this method to 10 ns, and applied it to merbromin dye and zinc-substituted myoglobin in a water-glycerol mixture. It has been found that the time dependence of the barycenter of the hole is expressed by a stretched exponential function and that the correlation time of the fluctuation obeys the Vogel-Fulcher law over the 150-300 K temperature range. The time behavior is much more non-exponential and much weakly dependent on temperature in protein solutions compared with dye solutions. It has been directly demonstrated that the conformational dynamics of a protein molecule is strongly dependent on that of its surroundings, and the glass transition of the protein is governed by the freezing of the solvent. Whole the obtained results have been found to be explained well by a hierarchically constrained dynamics model. We have also compared the conformational dynamics between native-like and moltenglobule-like cytochrome c. Further, it has been shown that the spectral shapes of the Qx and Qy bands of myoglobin and cytochrome c, which are buried in the inhomogeneously broadened absorption bands, can be determined using polarization spectroscopy in addition to the time-resolved spectral hole-burning.