FIGURE 4.

Phase diagram from mean-field models for instability-driven ordering in actomyosin solutions. (Diagram) As the ATP available to be hydrolyzed by the motors is depleted, the clustering process enhances the cross section and thus the effective cluster activity α_cl, causing an approach toward the instability threshold (solid line). Addition of static cross linkers such as streptavidin to the system shifts the instability threshold (as indicated by the dashed line) to smaller values of α_cl, thus enhancing the tendency of ordered clustering. (A and B) Experimentally observed and theoretically reproduced aster architectures demonstrating similarity between final assembly properties. In the simulation of the mean-field model on the right-hand side, the filament cluster density ρ_cl is color-coded in red while arrows show the orientation field. (Scale bar is 20 μm.)