Diffusion coefficients for rigid macromolecules with irregular shapes that allow rotational‐translational coupling
Diffusion coefficients for rigid macromolecules with irregular shapes that allow rotational‐translational coupling
复制标题
允许旋转平移耦合的不规则形状刚性大分子的扩散系数
作者：
W. Wegener
我们考虑了低雷诺数下刚性高分子在粘性流体中的六维扩散和摩擦张量。我们的治疗允许螺旋状的属性，耦合旋转和平移运动。我们表明，螺旋体的扩散中心可以从它的流体动力学反应中心不同。检查确保重合的对称性条件。扩散中心被发现是一个机构的点与最慢的扩散运动，而围绕反应中心的旋转遇到的平均阻力最小。宏观平移扩散系数是从六维扩散方程的扰动分析中计算出来的。我们发现，忽略旋扭耦合的方法必然会低估螺旋状粒子的扩散速率。提出了一个计算复杂物体扩散系数的程序框架。作为一个例子，我们处理一个长弯曲杆。
We consider six‐dimensional diffusion and frictional tensors for a rigid macromolecule immersed in a viscous fluid at low Reynolds number. Our treatment allows for screwlike properties which couple rotational and translational movements. We show that the center of diffusion of a screwlike body can be distinct from its hydrodynamic center of reaction. Symmetry conditions which ensure coincidence are examined. The center of diffusion is found to be the point of a body with the slowest diffusive movements, while rotations about the center of reaction encounter the least average resistance. The macroscopic translational diffusion coefficient is evaluated from a perturbation analysis of the six‐dimensional diffusion equation. We show that methodologies which ignore translational–rotational coupling will necessarily underestimate the diffusion rate of screwlike particles. A procedural framework is presented to calculate diffusion coefficients of complicated bodies. As an example we treat a long bent rod.