Turnover of Eg5 and microtubules in egg extract spindles measured by time-lapse fluorescence microscopy after photoactivation and photobleaching. (a) Fluorescence decay of photoactivated Eg5-paGFP (green) and fluorescence recovery of Cy5 microtubules (red) in the midzone, the halfzone, and the pole region within the first 2 min after photoactivation and photobleaching. A monoexponential fit (lines) to the experimental values (dots) yielded half-lives as indicated. (b) Box plots of half-lives and residuals of fluorescence decays of photoactivated Eg5-paGFP in the three different spindle regions. 4–12 measurements were made per region.