Fig. 6.

Synchrotron SAXS profiles of solutions of taxol-stabilized microtubules (MTs) as a function of increasing divalent ion concentration for GdCl₃ (3+), and divalent oligolysine (2+). The profiles are typical of the MT form factor (except for data at 1 mM for Gd³⁺, which lacks the form factor scattering profile). Gd³⁺ is extremely efficient at depolymerizing taxol-stabilized MTs at concentrations ≈ 1 mM. On the other hand oligolysine (2+) shows profiles typical of the MT form factor indicating that it neither bundles or depolymerizes MTs up to at least 144 mM.