FIGURE 6.

Critical bond stiffness. We determine the conditions necessary to hold the filament ends at a distance Δ from the surface for different end-to-end (a) and contour length (L); a is the control parameter and L is given by L/a = 1.1; L_p = 15 μm; Δ is chosen in the range 3–9 nm, i.e., the typical size of one actin monomer (∼6 nm). The curvilinear domain with blue (red) boundaries gives the bond stiffness compatible with the constraint 3 nm < Δ < 9 nm for conditions BC1 (BC2). For both kind of boundary conditions, the top (respectively, bottom) border, indicated by red and blue squares, is associated with Δ = 3 nm (Δ = 9 nm, red and blue dots). The vertical borders, indicated by blue and red triangles, are determined by the condition L_c < L (Eqs. D-3 and D-4); below this limit, no buckling occurs, whatever the bond robustness.