Analysis of fusion protein association with the macropinosome. (A and B) The probes all localize to macropinosomes but time of association differs. The images show a time sequence of a single macropinosome internalization for each probe. The sequence starts at time zero, when the macropinosome outline becomes a complete circle indicating membrane fusion to create a vesicle. The time of association of the GFP-FLN probe is longer than any of the other probes. (See also movies in Additional files 1, 2 and 3). (C) The graph shows the mean association time of each probe with macropinosomes. The mean for GFP-FLN was 71 sec (n = 40); GFP-FLNABD, 42.5 sec (n = 40); GFP-αA, 38.5 sec (n = 37) and GFP-αAABD 32.2 sec (n = 33) (GFP-FLN; GFP-FLNABD; GFPα-A; GFPα-AABD. Error bars represent standard error of the mean (SEM). The mean time of association of GFP-FLN was significantly different from all other probes (* = P < 0.001) and the GFP-FLNABD probe was significantly different from the GFP-αAABD (p < 0.05).