Figure 4.

Balance between force generation and relaxation causes weak pulsatile contraction with formation of very small clusters. Conditions used in a case shown here are R_M = 0.04, R_ACP = 0.01, <L_f> = 1 μm, and k_t,A = 70 s⁻¹. (a) The morphology of networks showing cluster formation taken at different time points. (b) The time evolution of a small pulsed cluster indicated by a blue box in (a). This cluster appears from ∼30 s and then becomes the largest at 41 s, as indicated by a white arrow. Then, it disassembles gradually over time. (c) The time evolution of a fluctuating cluster highlighted by a red box in (a). (d) The time evolution of the percentage of actin segments located within clusters. Random colors are assigned to curves to distinguish each cluster. Nascent pulsed clusters are shown in solid lines, whereas fluctuating clusters are shown in dot-dashed lines. (e and f) The frequency of appearance of pulsed clusters per 100 s depending on their size (e) and duration (f). Most clusters are very small and do not last for long time periods. To see this figure in color, go online.