FIG. 1.

Structural transition between asters and bundles. (a) Schematic of two filaments (blue) connected by a motor (orange). The motor is modeled as a Hookean spring with rigidity k. The motor force $\mid {\overrightarrow{f}}_m\mid$ is proportional to motor rigidity k. Each motor head (dark orange) binds to one filament and moves towards the barbed (+) end with velocity ${\overrightarrow{v}}_m$ (Eq. (1)). When the motor is bound to two filaments, the rate of work done by the motor spring $(\stackrel{.}{w})$ is computed as the sum of ${\overrightarrow{f}}_m\cdot {\overrightarrow{v}}_m$ over the two motor heads. (b) Tuning k induces the structural transition between asters and bundles. (c) Color map of $\langle \stackrel{.}{w}\rangle$. Asters and bundles are respectively associated with positive and negative values of $\langle \stackrel{.}{w}\rangle$. (d) Color map of the largest cluster size. A system with no cluster larger than 40 is considered to be isotropic. (e) Color map of radius of gyration R_g of the largest cluster. The boundary between bundle and aster is R_g = 0.125. The boundary of isotropic is the same as in (d).