Fig. 3.
Torque dependency of the mean rotational rates under various concentrations of ATP, ADP, and Pi. (A) [ATP] = [ADP], and [Pi] = 1 mM. Because the ratio [ADP][Pi]/[ATP] is constant, Δμ is constant (see Eq. 1). (B) [ATP] = 10 μM while varying [ADP] and [Pi] to control Δμ. Data from approximately 15 molecules were averaged under each condition. In total, data of 92 and 74 molecules are used in A and B, respectively. The mean rotational rates are calculated as follows: Because the magnitude of the imposed torque varies from particle to particle, we divided the horizontal axis into bins (width is 7 pN nm/rad except for the case in the absence of external torque) and took an average of the torque and rotational rates in each bin.