Figure 6. Time-dependent synchrotron SAXS data of the transition kinetics from bundles of microtubules (B_MT) to bundles of inverted tubulin tubules (B_ITT).

a, The B_MT phase was suddenly taken from room temperature to ≈ 0° C and the resulting transition to the B_ITT phase was followed in real time (t) by synchrotron small-angle-xray-scattering (SAXS). The profiles are for SAXS scans of a sample with 15 mM spermine taken at the temperature change (t = 0), thirteen minutes after the temperature change, and subsequently every ten minutes. The scans are offset for clarity with t = 0 at the bottom and t = 93 minutes at the top. b, The amplitude of the (10) peak of the B_MT phase (open diamonds) and the B_ITT phase (open squares) obtained from best fits for the data in (a). For simplicity, the (10) peak of the coexisting B_MT and the B_ITT phases were fit to Gaussians. c, Rates of disassembly of the B_MT phase (R(B_MT), open diamond) and creation of the B_ITT phase (R(B_ITT), open squares) as a function of spermine concentration obtained from fits to SAXS data (as in (a) and (b) for 15 mM spermine). All SAXS samples were at taxol/tubulin molar ratio = 0.55.