Grebenkov Denis S, Vahabi Mahsa, Bertseva Elena, Forró László, Jeney Sylvia
Laboratoire de Physique de la Matière Condensée (UMR 7643), CNRS - Ecole Polytechnique, 91128 Palaiseau, France.
Phys Rev E Stat Nonlin Soft Matter Phys. 2013 Oct;88(4):040701. doi: 10.1103/PhysRevE.88.040701. Epub 2013 Oct 21.
We investigate the diffusive motion of micron-sized spherical tracers in a viscoelastic actin filament network over the time span of 8 orders of magnitude using optical-tweezers single-particle tracking. The hydrodynamic interactions of a tracer with the surrounding fluid are shown to dominate at microsecond time scales, while subdiffusive scaling due to viscoelastic properties of the medium emerges at millisecond time scales. The transition between these two regimes is analyzed in the frame of a minimal phenomenological model which combines the Basset force and the generalized Stokes force. The resulting Langevin equation accounts for various dynamical features of the thermal motion of endogenous or exogenous tracers in viscoelastic media such as inertial and hydrodynamic effects at short times, subdiffusive scaling at intermediate times, and eventual optical trapping at long times. Simple analytical formulas for the mean-square displacement and velocity autocorrelation function are derived.
我们使用光镊单粒子追踪技术，在8个数量级的时间跨度内，研究了微米级球形示踪剂在粘弹性肌动蛋白丝网络中的扩散运动。结果表明，示踪剂与周围流体的流体动力学相互作用在微秒时间尺度上占主导地位，而由于介质的粘弹性特性导致的亚扩散标度则在毫秒时间尺度上出现。在一个结合了巴塞特力和广义斯托克斯力的最小唯象模型框架内，分析了这两种状态之间的转变。由此得到的朗之万方程解释了粘弹性介质中内源性或外源性示踪剂热运动的各种动力学特征，如短时间内的惯性和流体动力学效应、中间时间的亚扩散标度以及长时间最终的光学捕获。推导了均方位移和速度自相关函数的简单解析公式。
