FIGURE 3.

Two-kinesin velocity and step-size distributions against constant loads. A, velocity distribution histograms for two-kinesin complexes at applied loads ranging between 2.5 and 12 pN. The load maintained by the force clamp is indicated in each panel. Bead velocities were determined via a chi-squared minimization procedure reported in Ref. 24. Each plot is constructed from 7–27 trajectories (3–19 complexes). Bin counts were taken as the number of distinct trace components where beads moved with a velocity within the range of each bin for a period of 16 ms. B, distributions of bead displacement sizes found using a step-finding algorithm and their corresponding pairwise displacement distribution histograms. Bead displacement analyses are presented separately for cases where the force clamp was used to impose either low (2–5 pN; 58 traces included) or high (10–12 pN; 27 traces included) resisting loads.