Figure 5.

Heterogeneity in cytoplasmic diffusion has varied responsiveness to experimental perturbations. (a) Fluorescence images of fluorescent tubulin (top) and actin (bottom) in the context of the DMSO control (left) and addition of cytoskeleton depolymerizing drugs (right). Scale bars, 5 μm. (b) Schematic of experiments varying the experimental temperature (top) and prediction of the relationships between the diffusivity, D, and the experimental temperature, T, as well as the Boltzmann constant, k_B, and the viscous drag coefficient, ᵞ (bottom). (c) Schematic of experiments varying osmotic shock with sorbitol (top) and example bright-field images of osmotically shocked cells showing a reduction in cell volume (bottom). Scale bars, 5 μm. (d–f) The median diffusivity (bars) and standard error (error bars) are plotted for each experimental condition. Significance stars represent the result of the Wilcoxon rank sum test for equality of the medians. (g–l) Distributions of apparent diffusivities calculated from fits of the track-wise (g–i) or cell-wise (j–l) MSD curves displayed for each condition. Note the logarithmic scale along the y axis. Boxplots are drawn as in Fig. 2. Significance stars represent the result of Levene’s test for equality of variance. (d–l) ^∗p < 0.05, ^∗∗p < 0.01, ^∗∗∗p < 0.001, ^∗∗∗∗p < 0.0001.