Mason D W
Biophys J. 1976 May;16(5):407-16. doi: 10.1016/S0006-3495(76)85697-4.
Velocity sedimentation has been used extensively to separate particles according to the magnitude of their sedimentation velocity in suitable media. This technique has been used over a wide range of particle size from protein molecules, viruses, subcellular particles to whole cells. Successful separation demands that collective particle motion should not occur. In practice it is observed that such systems may, under certain circumstances, suffer from a particular type of instability which destroys the normal dependence of sedimentation velocity on particle size and density. The aim of this paper is to identify the critical parameters that determine the development of this instability. Stability criteria are deduced and predictions of the theory compared with published observations. Satisfactory agreement between theory and observation is obtained. It is concluded that the simple stability criterion, namely that stable sedimentation will occur if the total density gradient is in the direction of the sedimenting force, grossly overestimates the particle load that can be separated in practice. Some specific recommendations for optimum particle loading are included. Earlier theoretical and experimental works are briefly reviewed.
速度沉降法已被广泛用于根据颗粒在合适介质中的沉降速度大小来分离颗粒。该技术已应用于从蛋白质分子、病毒、亚细胞颗粒到全细胞等广泛的粒径范围。成功的分离要求颗粒不能发生集体运动。在实际中观察到，在某些情况下，这类系统可能会遭受一种特殊类型的不稳定性，这种不稳定性会破坏沉降速度对颗粒大小和密度的正常依赖关系。本文的目的是确定决定这种不稳定性发展的关键参数。推导了稳定性准则，并将理论预测与已发表的观测结果进行了比较。理论与观测结果取得了令人满意的一致。得出的结论是，简单的稳定性准则，即如果总密度梯度与沉降力方向一致就会发生稳定沉降，严重高估了实际中可分离的颗粒负载量。文中还包括了一些关于最佳颗粒负载量 的具体建议。对早期的理论和实验工作进行了简要回顾。
