Fig. 6. Effect of ligands on the turbidity time course of in vitro microtubule assembly. The reaction was started by warming the solution from 15 to 37 °C. (A) Effect of various concentrations of colchicine (1) (a: 0 μM; b: 1 μM; c: 3 μM; d: 5 μM; and e: 7 μM) on tubulin at 18 μM in polymerization buffer. (B) Effect of various concentrations of 5i (a: 0 μM; b: 2 μM; c: 4 μM; d: 6 μM; and e: 10 μM) on tubulin at 18 μM in polymerization buffer. The insets represent the percentage of assembly inhibition as a function of the mole ratio of the total ligand to total tubulin in the solution (R).