FIGURE 6.

Effect of ATPγS concentration on TA2F₁ rotation rate with a magnetic bead. Shown is the effect of ATPγS concentration on rotation of TA2F₁γ2c using the system displayed in Fig. 4A. A, displayed are representative rotation traces recorded at 1000 fps with a variety of ATPγS concentrations: 2 mm (blue), 200 μm (cyan), 20 μm (green), 2 μm (yellow), and 1 μm (red). B, displayed are the average rotation rates of 15 molecules at the concentrations of ATP indicated. Error bars represent S.D. B, inset, Lineweaver-burke plot of data from B used to define the V_max of 4.02 ± 0.3 revolutions s⁻¹ (rps) and K_m of 5.61 ± 1.33 μm. C–E, representative rotation traces recorded using a magnetic particle as a rotation probe at a variety of ATPγS concentrations: 2 mm (C), 200 μm (D), and 20 μm (E). Insets from C–E show the x-y trajectories of the centroid of the rotating particles from the respective traces. F–H are distributions of rotary angles shown in C–E. 1, 2 and 3 are the three dwell positions separated by 120°. The traces, plots, and trajectories are representative of 15 molecules. The rotation assay was conducted as described under “Experimental Procedures.”