Figure 4. Diffusional description in 4D.

A, time sequence for a moving particle in three dimensional space (x,y,z) during 20 s. The z axis was calibrated using fluorescent beads of known size (see methods). Depicted particle goes from the inside of the cell (blue colors) to the plasma membrane (red colors), and jump from one corral to the next. The arrow indicates the starting point for the trajectory. B, Smoothed plots for the same trajectory, showing the correlation between the position on the z axis (upper panel) with particles' change in velocity (lower panel). C, Histogram for the residence time at the maximal fluorescence intensity. The solid line correspond to a first order exponential decay with an associated time constant indicated (n = 20).