First-passage time analysis of particle transport in the cytoplasm

Abstract

Cell mechanics are often probed by tracking fluorescent tracer particles embedded in the cytoplasm. The analysis of such experiments typically involves computation of the mean-square displacement of the particles, and thus ignores the variation in how individual particles are transported by activity within the cell. Here, first-passage time (FPT) analysis is presented as an alternate measure that can better represent the diversity of particle behavior. FPT analysis reveals that the diffusive-like motion of tracer particles can not be accurately modeled as random-walk diffusion due to inhomogeneity of particle transport rates. The technique is then used to investigate the effect of vimentin intermediate filaments (VIFs) on cytoplasmic transport. We find that VIFs significantly inhibit the displacement of objects in the cytoplasm.