Probing microtubule-kinesin active matter in a low activity regime

Countless living systems exhibit complex behaviors driven by the spontaneous self-organization of their constituents. The dynamics of these systems occur far from equilibrium and often rely on the localized consumption of biological energy sources. In this work, we leverage kinesin-driven microtubule networks as a simple experimental system to quantify non-equilibrium material behaviors. By limiting kinesin-motors' access to energy-rich ATP, we tune the activity of our reconstituted ensembles, allowing us to probe the transition between fluidized and elastically gelled protein suspensions. We observe that our system's dynamics depend non-trivially on ATP concentration and can be further tuned by varying an incorporated ATP regeneration backbone. Together, these observations lend a new perspective on the energy-consuming protein interactions that drive emergent non-equilibrium flow in active materials.