Figure 2.

Series of five consecutive deformation cycles at 1 μm/s. (a) Force-time traces of five consecutive deformations as described in Fig. 1; the force shown is the longitudinal component of the force acting on the trap. A negative force corresponds to a situation where the traps are further apart than the beads, i.e., the exerted force is pulling on the bundle. A positive force denotes pushing on the bundle. Individual cycles are shown in different shades of blue, from black (first cycle) to light blue (last cycle). Yellow and blue regions correspond to compression and expansion periods, respectively. (b) Force-distance curves of the bundle deformation during the cycles. In the compression period, shown by the upper curves, the traps move from right to left; in the expansion periods, shown by the lower curves, the traps move from left to right. The inset is a scheme to show the direction of the hysteresis. (c) Schematic of the model used for fitting the data. L denotes the initial length of the bundle, X(t) is the distance between the traps, and k is the trap stiffness. The bundle tension is denoted by σ_L and the bending torque by σ_θ. (d) Comparison between the fit (continuous line) and the original data yield good overall agreement. One set of parameters τ, k_s, and κ is used to fit the whole curve (see Table S1).