FIG. 9.

A nonequilibrium phase diagram of kinesin-4 and microtubules. (a) Microscopic building blocks: Kinesin-4 (blue) attaches to a microtubule (gray), walks to the microtubule plus end, and accumulates at the plus end, creating a heterogeneous filament that can interact with other filaments by directed transport or via steric alignment induced by PEG. (b) Mesoscale organizational motifs include asters, layers, or bundles. (c) Hierarchically organized mesoscale building blocks yield macroscopic phases including dynamic asters, globally contracting gels, active bilayer foams, and fluidized extensile bundles. (d) Phase diagram at 200 nM kinesin as a function of tubulin and PEG concentration. (e) Phase diagram at 0.5% PEG (w/w) as a function of protein concentrations.