Figure 2.

Normalized histograms (bin size 25 nm/s) of gliding microtubules for different ratios of N_a/N. Both the experimental data (A) and simulated data (B) display a clear shift in the velocity distributions from fast motility (at high N_a/N) to slow motility (at low N_a/N), notably with a bimodal distribution at approximately N_a/N = 0.7. To keep the y axis equal in all panels, the actual peaks are not visible in all graphs. The peak amplitudes of the normalized occurrence at the given bin width for N_a/N = 0.6 are 0.52 in the experiment and 0.62 in the simulation. Similarly, for N_a/N = 0.3, the peak values are 0.65 in the experiment and 0.96 in the simulation. Negative velocities were due to the finite tracking error of ≈ 20 nm for the microtubule positions. For the numbers of microtubules and the coefficients of the Gaussian fitting to the histograms, see Table S1. In the simulation, the total motor number was varied from N = 10 to N = 100 in increments of 10 and the results were combined in a single histogram. The following parameter values were used: κ = 1 pN/nm, f^c = 3 pN, μ = 5 s⁻¹, f_s = 7 pN, D_a = 1000 nm²/s, ${\omega }_{\text{a}}^0=1{\text{s}}^{-1}$, ${\omega }_{\text{p}}^0=0.1{\text{s}}^{-1}$, v₀ = 830 nm/s and ξ/L = 10 Ns/m². To see this figure in color, go online.