Fig. 1. Recapitulating dynamic instability. (A) Snapshots of the simulation at different time steps (T). The MTs grow from seeds at left towards the `cell' edge (right). The colors describe the state (red, GTP; green, GDP) of each subunit. At early times, when free tubulin is near the initial value, MTs grow persistently. As the polymer fraction increases and the concentration of free tubulin drops, catastrophe becomes more frequent. Eventually the steady-state is reached, and the system behavior exhibits behavior very similar to experimentally observed dynamic instability (see Movie 1, supplementary material). (B,C) Comparison between life history plots obtained experimentally in vitro (B) and with our model (C). Experimental data were adapted from Fygenson et al. (Fygenson et al., 1994). C shows three adjacent steady-state MTs from the simulation shown in (A). In this simulation, parameters were chosen arbitrarily; all other simulations reported in this manuscript are correlated to physiological concentrations and dimensions as described in Materials and Methods.