Figure 3.

Displacement and force of beads coated with single 22S dynein molecules at high trap stiffness. (a) Time course of displacement of a 22S dynein-coated bead at 3 μM ATP. The bead was prepared by mixing 22S dynein molecules and beads at 10:1 molar ratio. The trap stiffness was 0.050 pN/nm. Force (right-hand scale) was calculated from the displacement multiplied by the trap stiffness (20). (b) Histogram of the maximum force developed by single molecules of 22S dynein. The maximum force was measured where the bead stayed more than 0.2 s at the maximal level of displacement without taking further steps. Trap stiffness was 0.050–0.20 pN/nm. The mean and standard deviation are 4.7 and 0.64 pN, respectively (n = 92). (c) Force-velocity relationship of single 22S dynein molecules. Twelve runs of bead displacements were averaged, and the displacement of 22S dynein molecules was calculated according to Kojima et al. (20). The velocities were calculated from the slopes of the displacement. Error bars indicate confidence intervals of the velocities at a confidence level of 95%. The curve fit (v + 1.70)(y + 74.9) = 504 refers to Hill (33).