Coomassie Blue staining. Tubulin (2 μM) was treated with 2.0 mM ODNB or DTNB in Mes a.b. at 25 °C for 90 min. (A) ODNB-modified tubulin without (lanes 1–2) or with (lanes 5–9) 5 mM DTT boiled for 0, 1, 3, 5 and 10 min, by loading 2 μg/lane. Lane 1, control; lane 2, ODNB only; lane 3, molecular-mass standards; lane 4, control with DTT. (B) Conditions are the same as for (A) but with DTNB in lanes 2 and 5–9. Large arrows indicate control monomers and small arrows indicate different monomers.