Fig. 4: Hydrophobic and ionic reagents change the IF-microtubule bond properties.

a Valid unbinding rates r_u,eff and potential widths x_u to simulate the experimental data shown in Fig. 3c, e, and g for the different buffer conditions: pure CB (gray), CB with TX100 (orange), and CB with additional magnesium (blue). r_u,eff and x_u pairs, which are valid for several buffer conditions, are color coded by mixed colors. r_u,eff and x_u increase from additional magnesium chloride across pure CB to added TX100. b Energy landscape for the theoretical modeling of the IF-microtubule bond: A two-state model (unbound, bound) is sufficient to describe the experimental data shown in Fig. 3. From the binding and unbinding rates, we calculated the differences in activation energies E_Ab and E_Au (see Eq. (8) in the Supplementary Information) of bonds in different buffer conditions to open or close. However, the absolute values cannot be determined, as indicated by the graph break (black double-lines). For different buffer conditions, the position of the energy barrier relative to the unbound and bound state, x_b and x_u, respectively, changes. Source data are provided as a Source Data file.