Figure 6: Active kinetic spring model.
(a) Schematic of the model—cytoskeletal springs (green) are connected to fixed boundaries (blue) by kinetic elements (orange diamonds and Y shapes) that can bind and unbind at force-dependent rates. Myosin motors (red) actively contract the springs internally, generating force. Components can also appear or disappear via turnover (transparency). The total force on the walls is the sum of the contractile forces from bound springs. (b) Force profiles based on the model for 25 μM actin and 0.1 ratio of springs (that is, ACP-actin spring constructs) and 0.05 ratio of motors to actin at different network turnover rates. Profiles with transient peaks and stable forces are both observed, as consistent with Brownian dynamics simulations. Curves from top to bottom (based on peak force) represent network turnover rates kd of 0, 0.1, 0.2, 1, 2 and 5 × relative to ku0. (c) Heat maps of the log of the normalized peak force for networks with different configurations. Forces are normalized to networks with 0.1:0.05 ratio between springs and motors and actin concentration of 25 μM. (d) Heat maps of S for corresponding configurations in c. The active kinetic spring model is able to qualitatively capture similar mechanical properties compared with Brownian dynamics simulations.
