FIG. 4.

Investigation of a SF segment as it is contracting under a constant load F* = F/ζ for different values of normalized bond catchiness α^⋆ = 0,0.5 and 1. Top figures: (a) fraction of attached cross bridge η and (b) force f^⋆ = f/ζ on an active cross bridge as a function of time for F* = 1.2. Bottom figures: (c) normalized steady state SF contraction ${\delta }_s^{\ast }=\mathrm{\Delta }{d}_s/\mathrm{\Delta }{d}_s^{\text{max}}$ and (d) activation a = η * N(Δd_s)/(N_xN_y) of an SF segment as a function of applied force F*. The symbols + and □ indicate the points at which the SF segment stalls and ruptures, respectively.