Fig. 5. Single-molecules of Crac-GFP in polarized cells undergoing chemotaxis. (A) Chemotactic cells expressing Crac-GFP were observed under TIR-FM (see supplementary material Movie 2). Crac molecules on membranes were predominantly observed at the leading edge pseudopod (white arrow), as expected from previous works (Parent et al., 1998). Arrowheads represent Crac-GFP found at the rear end of cells. The gray arrow indicates the direction of cell movement. (B) Dissociation curves of Crac-GFP bound to the pseudopod () or posterior region () were fitted to a single exponential curve with a constant of 110 milliseconds and a sum of two exponentials with constants of 110 milliseconds (72%) and 890 milliseconds (28%), respectively.