Fig. 5. Track of a spot photoactivated in the plasma membrane of a moving cell. A spot was photoactivated on the underside of a cell expressing the cAMP receptor coupled to photoactivatable GFP and followed as a pseudopod extended. Ax2 cells transformed with plasmid pDT18 were made aggregation-competent and induced to migrate under a thin layer of agarose to constrain movement in the z-axis. Cell outlines were traced from the accompanying DIC image. Photoactivation was for 0.77 seconds and frames were taken every 0.59 seconds; times are given in seconds in the images; scale bar is 10 µm. To aid visualization, the contrast/brightness of these images was altered in ImageJ by conversion to 8-bit then changing the min/max pixels from 0-255 to 11-137. See Movie 9 in supplementary material.