Fig. 3. Comparison of patterns of experimental and simulated fluorescence images of lamellipodia. (a-d) Dependence of the pattern on the mean filament length and orientation-disorder parameters in simulated fluorescence images. Low-disorder parameters (R=500 µm, =1°) and a mean filament length of (a) 4 µm, (b) 1 µm and (c) 0.3 µm and, (d) intermediate-disorder parameters (R=20 µm, =20°) and filament length of 4 µm. Simulated image with optimal parameters (L=1.3 µm, R=10 µm, =20°) built from stochastic processes (e) compared with the deterministic process of Arp2/3 activation (f). (g,h) Experimental image of equivalent sizes; (g) untreated cell and (h) cell treated with 0.1 µM cytochalasin D. Bar, 10 µm.