Fig. 3. Movement of a keratin F particle through the cell (Movie 2). (A) Course of a keratin F particle in a keratinocyte (NEB-1) expressing EGFP-K5, tracked over 10 minutes. (B-H) Individual time-points from this sequence; the position of the particle is indicated by the white arrow. During imaging, the particle travelled a distance of 18 µm. The courses of several other F keratin particles are seen to converge in Movie 2. Some slow, S keratin particles appearing tethered to the keratin network are visible (bottom part of B-H). The S particles moved only slightly, with an oscillatory motion around a central axis. As in Fig. 1, the keratin filament network appears to be involved in the particle movement (B-D); the longest pause (here in D, 3 minutes) occurs when the particle is located over a keratin filament. The movie covers 41 time-points with a 15 second interval, and 9 Z sections (500 nm spacing) were taken for each time-point; images were obtained by projection of sections 5 and 6. Bar, 1 µm.