Figure 2.

Time courses of displacement and force transients produced by truncated kinesin fragments, K411 (a), K351 (b), K340 (c), and K340–chain (d). The C termini of recombinant fragments were biotinylated to specifically bind to streptavidin-coated beads. By using an optical trap, a kinesin-coated bead was positioned to make contact with a microtubule adsorbed on a glass surface, and its displacements were detected by a quadrant photodiode detector with nanometer accuracy. The forces were obtained as (bead displacement) × (trapping stiffness).