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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Protein Dielectrophoresis in Solution
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Protein Dielectrophoresis in Solution

机译：溶液中蛋白质介电泳

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摘要

Proteins experience either pulling or repelling force from the gradient of an external electric field due to the effect known as dielectrophoresis (DEP). The susceptibility to the field gradient is traditionally calculated from the solution of the electrostatic boundary-value problem, which requires assigning a dielectric constant to the protein. This assignment is essential since the DEP susceptibility is proportional, in dielectric theories, to the Clausius-Mossotti factor, the sign of which is controlled by whether the protein dielectric constant is below (repelling) or above (pulling) the dielectric constant of water. The dielectric constant is not uniquely or even well-defined for a particle of molecular size and the Clausius-Mossotti factor is shown here to be inadequate for describing the dipolar response of the protein and hydration water. An alternative theory is developed from the standpoint of molecular properties of the protein solute and water solvent. The effective polarity of the protein molecule enters the theory in terms of the variance of its molecular dipole moment and its refractive index. Molecular dynamics (MD) simulations of the protein cytochrome c in solution are performed to calculate the dipolar susceptibilities entering the theory. We find that tumbling of the protein on the nanosecond time scale results in a positive DEP (pulling). The DEP susceptibility for cytochrome c acquired from MD simulations is 10(3) -10(4) times higher than predicted by the Clausius-Mossotti factor. Nevertheless, this high DEP susceptibility is fully consistent with empirically confirmed Oncley's equation connecting the protein dipole to dielectric increments of protein solutions. For cytochrome c, high DEP susceptibilities calculated from MD are consistent with experimental dielectric data. We provide a general relation connecting the DEP susceptibility to the dielectric increment of solution.
机译：由于称为介电泳（DEP）的效果，蛋白质从外部电影效果（DEP）的效果，蛋白质从外部电场的梯度拔出或排斥。传统上从静电边值问题的溶液计算出对场梯度的敏感性，这需要将介电常数分配给蛋白质。由于DEP易感性在介电理论中，在介电理论中，该任务是必不可少的，该符号由蛋白质介电常数是否低于（排斥）或更高（拉动）水的介电常数来控制。对于分子尺寸的颗粒，介电常数不是唯一的或甚至均匀地定义，并且这里示出了Clausius-mossotti因子以描述蛋白质和水合水的偶极响应不足。从蛋白质溶质和水溶剂的分子特性的观点来发展替代理论。蛋白质分子的有效极性在其分子偶极力矩的方差及其折射率方面进入了理论。进行溶液中蛋白质细胞色素C的分子动力学（MD）模拟，以计算进入该理论的偶极敏感性。我们发现蛋白质的蛋白质在纳秒时间尺度上导致正DEP（拉动）。从MD模拟中获取的细胞色素C的DEP易感性比CLAUSIUS-MOSSOTTI因子预测的10（3）-10（4）倍。然而，这种高DEP易感性与经验证实的INCHEY等式将蛋白质偶极物连接到蛋白质溶液的介电子增量的情况完全一致。对于细胞色素C，由MD计算的高DEP敏感性与实验介质数据一致。我们提供了一种将DEP易感性与解决方案的介电增量连接的一般关系。

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