蛋白质动态集体性的光开关
Photo Switching of Protein Dynamical Collectivity
摘要：
我们研究了红色荧光蛋白mCherry，mOrange 2和TagRFP-T的皮秒结构动力学的不可逆光漂白的变化。使用太赫兹时域光谱的蛋白质动态转变的测量显示，在所有情况下，在漂白状态的开启温度的增加。该结果是令人惊讶的，因为蛋白质表面几乎没有变化，因此负责转变的溶剂动力学不应该改变。由蛋白质吸光度的准谐波计算指导的测量的光谱分析表明，确实溶剂的动态开启温度是独立的热稳定性和光状态，但蛋白质的动态开启温度转移到更高的温度。这是第一次演示了蛋白质的动态开启温度与蛋白质的功能状态。所观察到的蛋白质动态开启温度相对于溶剂的变化表明蛋白质皮秒运动所需的流动水增加：即这些运动更集体。熔点测量结果表明，光漂白状态是更热稳定和相关的RFPs的结构分析表明，有一个增加内部水通道，以及更均匀的原子均方根位移。这些观察结果与先前的建议一致，即水通道形成与扩展的光激发提供O2进入发色团和随后的荧光损失。我们报告说，这些相同的通道增加内部耦合，提高皮秒蛋白质运动的热稳定性和集体性。蛋白质和溶剂动力学起始点的太赫兹光谱表征可以普遍应用于测量蛋白质运动的总体变化。
英文摘要：
We examine changes in the picosecond structural dynamics with irreversible photobleaching of red fluorescent proteins mCherry, mOrange2 and TagRFP-T. Measurements of the protein dynamical transition using terahertz time-domain spectroscopy show in all cases an increase in the turn-on temperature in the bleached state. The result is surprising given that there is little change in the protein surface, and thus the solvent dynamics held responsible for the transition should not change. A spectral analysis of the measurements guided by quasiharmonic calculations of the protein absorbance reveals that indeed the solvent dynamical turn-on temperature is independent of the thermal stability and photostate however the protein dynamical turn-on temperature shifts to higher temperatures. This is the first demonstration of switching the protein dynamical turn-on temperature with protein functional state. The observed shift in protein dynamical turn-on temperature relative to the solvent indicates an increase in the required mobile waters necessary for the protein picosecond motions: that is these motions are more collective. Melting-point measurements reveal that the photobleached state is more thermally stable and structural analysis of related RFPs shows that there is an increase in internal water channels as well as a more uniform atomic root mean squared displacement. These observations are consistent with previous suggestions that water channels form with extended light excitation providing O2 access to the chromophore and subsequent fluorescence loss. We report that these same channels increase internal coupling enhancing thermal stability and collectivity of the picosecond protein motions. The terahertz spectroscopic characterization of the protein and solvent dynamical onsets can be applied generally to measure changes in collectivity of protein motions.
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