Fig. 3.
Cellular automaton simulations. The two experimentally observed aggregation processes—merging and growth stiffening are described using a continuous agent-based simulation. The actin-fascin strings are modeled as polar elongated strings that move with a velocity v on meandering trails (A). The tip is subjected to curvature changes of rate ω and a noise level α, resulting in a meandering trajectory (inset B). The strings stiffen due to growth processes of rate λ. Besides, merging events with adjacent objects occur if the relative angle |θ| between them is smaller than θc. These two aggregation processes lead to the emergence of rings in two configurations—open and closed (B). The occurrence of two ring configurations is reflected in the ring radii distribution p(r) and the corresponding cumulative distribution P(r) that can be separated in open and closed contributions (C). The distribution for open and closed rings decays approximately exponential. The ratio of open to closed rings Γ increases with the rate of the random turns ω, while it decreases with the noise level α (D and Fig. S5). If not indicated otherwise the parameters are ω = 0.1, λ = 0.4, α = 1.0, and θc = 100. All scale bars are one string length L0.