Cells are remarkable machines capable of performing an exquisite range of functions, many of which depend crucially on the activity of molecular motors that generate forces. Recent experiments have shown that intracellular random movements are not solely thermal in nature but also arise from stochasticity in the forces from these molecular motors. Here we consider the effects of these non-thermal random forces. We show that stochastic motor force not only enhances diffusion but also leads to size-dependent transport of objects that depends on the local density of the cytoskeletal filaments on which motors operate. As a consequence, we find that objects that are larger than the mesh-size of the cytoskeleton should be attracted to regions of high cytoskeletal density, while objects that are smaller than the mesh-size will preferentially avoid these regions. These results suggest a mechanism for size-based organelle positioning and also suggests that motor-driven random forces can additionally enhance motor-driven transport.

细胞是出色的机器，能够执行各种功能，其中许多功能主要取决于产生力的分子电动机的活动。最近的实验表明，细胞内随机运动不仅在性质上是热的，而且还起因于这些分子马达的力的随机性。在这里，我们考虑这些非热随机力的影响。我们表明，随机电动机力不仅增强扩散，而且导致物体的尺寸依赖性运输，该运输取决于电动机所作用的细胞骨架细丝的局部密度。结果，我们发现大于细胞骨架网孔大小的物体应被吸引到细胞骨架密度高的区域，而小于网格尺寸的对象将优先避开这些区域。这些结果表明了一种基于大小的细胞器定位的机制，并且还表明了马达驱动的随机力可以进一步增强马达驱动的运输。