Lebard David N, Matyushov Dmitry V
Center for Biological Physics, Arizona State University, P.O. Box 871604, Tempe, Arizona 85287-1604, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Dec;78(6 Pt 1):061901. doi: 10.1103/PhysRevE.78.061901. Epub 2008 Dec 1.
Molecular dynamics simulations have revealed a dramatic increase, with increasing temperature, of the amplitude of electrostatic fluctuations caused by water at the active site of metalloprotein plastocyanin. The increased breadth of electrostatic fluctuations, expressed in terms of the reorganization energy of changing the redox state of the protein, is related to the formation of the hydrophobic protein-water interface, allowing large-amplitude collective fluctuations of the water density in the protein's first solvation shell. On top of the monotonic increase of the reorganization energy with increasing temperature, we have observed a spike at approximately 220 K also accompanied by a significant slowing of the exponential collective Stokes shift dynamics. In contrast to the local density fluctuations of the hydration-shell waters, these spikes might be related to the global property of the water solvent crossing the Widom line or undergoing a weak first-order transition.
分子动力学模拟表明，随着温度升高，金属蛋白质体蓝素活性位点处由水引起的静电涨落幅度急剧增加。以改变蛋白质氧化还原状态的重组能来表示，静电涨落宽度的增加与疏水蛋白质 - 水界面的形成有关，这使得蛋白质第一溶剂化层中的水密度能够进行大幅度的集体涨落。除了重组能随温度升高单调增加外，我们还观察到在大约220 K处出现一个尖峰，同时指数型集体斯托克斯位移动力学也显著减慢。与水合层水分子的局部密度涨落不同，这些尖峰可能与水溶剂跨越维德曼线或经历弱一级转变的整体性质有关。
