Analysis of microtubule growth rate and direction derived from single growing ends. A.

<p>Analysis of microtubule growth rate and direction in green-red ends. Rates are calculated as the distance between the front (green dots) and the rear (white dots) of red head, while directions are calculated from direction vectors connecting the rear of green tails (red dots) to the front of red heads (green dots). Growth vectors (shown by white arrows in left panels) are drawn from the back of green tails using normalized direction vectors scaled up to the quadruple of calculated rates. Scale bar: 1 µm. <b>B.</b> Histogram of growth rates calculated for all single green-red ends identified in the COS cell. <b>C–D.</b> Polar histogram plots of growth directions calculated for all single green-red ends from 12 dCCD frames of the COS cell in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0050421#pone.0050421.s002" target="_blank">Figure S2A</a> (<b>C</b>) or derived by the plusTipTracker program from the raw images of the same cell (<b>D</b>). <b>E–F.</b> Polar plots of growth rates against growth directions of single green-red ends from 12 dCCD images of the entire COS cell (E) or the boxed region (F) shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0050421#pone-0050421-g005" target="_blank">Figure 5B</a>. The numbers between 60° and 90° indicate the actual number of ends (<b>C</b>), the normalized end number ratio (<b>D</b>), or the growth rate in µm/min (<b>E–F</b>).