In vitro tubulin polymerization assay

The tubulin polymerization assay was performed as described by the manufacturer (Cytoskeleton Inc, Denver, CO, USA). Briefly, DI at various concentrations was incubated with purified bovine tubulin in 80 mmol/L PIPES buffer (pH 6.9) containing 2 mmol/L MgCl₂, 0.5 mmol/L EGTA, 1 mmol/L GTP and 15% glycerol. Increases in absorbance at 340 nm were recorded every min for 1 hat 37 °C using a spectrophotometer.