Figure 1

Transport of colloidal polystyrene particles during microtubule self-organisation. Images of the preparation (10 mg ml^-1 tubulin, 2 mM GTP) as viewed between crossed linear polars and wavelength retardation plate, at different times during self-organisation; A), 20 min; B), 40 min; C), 60 min; D), 5 hours. The numerous small dots are polystyrene beads of 1.1 μm diameter. Several have been highlighted and the coloured lines indicate their trajectories. During the first hour of self-organisation, the microtubules orient along the direction indicated by the bead trajectories. In the completed self-organised structure shown in D), a level of organisation of 20 μm separation can also be seen. At higher magnification, there are other levels of organisation having separations of 5 μm and 1 μm.