Microscopic viscosity and rotational diffusion of proteins in a macromolecular environment
Microscopic viscosity and rotational diffusion of proteins in a macromolecular environment
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DOI：
10.1016/s0006-3495(99)77427-8
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发表时间：
1999-05-01
影响因子：
3.4
通讯作者：
Blouquit, Y
中科院分区：
文献类型：
--
作者：
Lavalette, D;Tétreau, C;Blouquit, Y
斯托克斯-爱因斯坦-德拜方程目前用于从旋转相关时间的测量获得关于蛋白质大小或局部粘度的信息。然而，连续和均匀溶剂的隐含假设在体内（因为大分子的高密度）或体外（其中通过添加各种尺寸的粘性共溶剂来调节粘度）都不成立。为了量化的非均匀性的后果，我们已经测量了旋转布朗运动的三个球状蛋白质的分子量从66到4000 kD的存在下，1.5至2000 kD的葡聚糖作为粘性共溶剂。我们的研究结果表明，线性粘度依赖的斯托克斯-爱因斯坦关系必须取代幂律来描述旋转布朗运动的蛋白质在大分子环境中。幂律指数表示蛋白质仅经历大分子共溶剂的流体动力学相互作用的一小部分。的指数在蛋白质的大小和共溶剂的质量方面的显式表达式得到，允许定义的微观粘度。实验数据表明，一个类似的有效微粘度应在克莱默斯介绍！描述蛋白质反应速率的方程。
The Stokes-Einstein-Debye equation is currently used to obtain information on protein size or on local viscosity from the measurement of the rotational correlation time. However, the implicit assumptions of a continuous and homogeneous solvent do not hold either in vivo, because of the high density of macromolecules, or in vitro, where viscosity is adjusted by adding viscous cosolvents of various size. To quantify the consequence of nonhomogeneity, we have measured the rotational Brownian motion of three globular proteins with molecular mass from 66 to 4000 kD in presence of 1.5 to 2000 kD dextrans as viscous cosolvents. Our results indicate that the linear viscosity dependence of the Stokes-Einstein relation must be replaced by a power law to describe the rotational Brownian motion of proteins in a macromolecular environment. The exponent of the power law expresses the fact that the protein experiences only a fraction of the hydrodynamic interactions of macromolecular cosolvents. An explicit expression of the exponent in terms of protein size and cosolvent's mass is obtained, permitting definition of a microscopic viscosity. Experimental data suggest that a similar effective microviscosity should be introduced in Kramers! equation describing protein reaction rates.