Fig. 6. Coiled coil response to an applied shear force in SMD simulations. (A) Simulation snapshots of CC-A4B4 obtained at the fastest (v = 109 nm s–1) and slowest (v = 106 nm s–1) retract speeds. (B) Bell–Evans plot showing the relationship between the average plateau force and the corresponding retract speed. The plateau forces shown are calculated as the mean of the average plateau forces obtained in 5 (CC-A4B3) or 6 (CC-A4B4) simulation runs at v = 106 nm s–1 and v = 107 nm s–1, 20 runs for both coiled coils at v = 108 nm s–1 and for CC-A4B3 at 109 nm s–1, and 40 runs for CC-A4B4 at v = 109 nm s–1. The error bars are the standard error of the mean. The average plateau force in each simulation run is calculated by averaging over an extension interval of [2 < ΔL < 6] nm for the two largest retract speeds, and [2 < ΔL < 4] nm otherwise. The lines represent fits to the Bell–Evans equation, using kL = 40 pN nm–1 for converting the retract speed into loading rate. The data points obtained at the fastest retract speed of v = 109 nm s–1 (corresponding to a loading rate of 4 × 1010 pN s–1) were not included into the Bell–Evans fit. At this retract speed, the response mechanism is dominated by progressive uncoiling instead of uncoiling-assisted sliding.
