Figure 1.

Experimental set-up. (a) The flow cell is constructed with glass coverslips and double-sided tape. Kinesin is flowed in section by section, resulting in a stepwise gradient. (b) Kinesin motors attach to the surface and move the biotinylated microtubule around. Reproduced from Hess, et al.⁵ with permission from the Americal Chemical Society. (c) The biotin and streptavidin allow the microtubules to crosslink to one another forming microtubule bundles and spools. Reproduced from Luria, et al.²⁰ with permission from the Royal Society of Chemistry. (d) There are several theories on how spools are initiated. Twist-bend coupling occurs as a result of the microtubule structure; simultaneous sticking of three or more microtubules is dependent on the microtubule surface density; and pinning events are dependent on the kinesin surface density. Adapted from Luria, et al.²⁰ with permission from the Royal Society of Chemistry.