Figure 4.

Stepwise movements. (a and c) Expanded time courses of K411-bead and K351-bead displacements at trapping stiffness of 0.022 pN/nm. Horizontal broken lines show the positions averaged in the regions where a bead paused within a standard deviation of 2 nm for longer than 30 ms (b and d). Histograms of the step sizes of K411 and K351, respectively. The step sizes of kinesin fragments shown in b and d were obtained from the differences between adjacent broken lines after corrected for the compliance due to the bead-to-glass linkage. The attenuation due to the stiffness of the bead-to-glass linkage [(Kt + Kp)/Kp] was 1.1–1.3 in the region in which we counted the events. (e) Expanded time course of one K340–chain bead at a trapping stiffness 0.071 pN/nm.