Figure 32.

HS-AFM analysis of the diffusion and interaction dynamics of trimeric OmpF. (a) High-resolution HS-AFM visualization of the dynamic movement of about 70 OmpF trimers in the membrane (imaging rate, at 2.1 fps). The resolution is high enough to allow determining the lateral position and the rotational angle of every single channel. (b) The effect of local membrane crowding on the diffusion behavior of individual OmpF trimers. The average position (black star) and positional standard deviation (black error bars) were determined for each molecule by the lateral and angular tracking of the proteins in subsequent frames (colored lines and arrows). From the average positions, the Voronoi tessellation of the membrane surface was calculated (black meshwork) depicting the free membrane area that each molecules experiences. Molecules housed in large Voronoi cells (i.e., large free membrane space) revealed high mobility, while molecules in locally and densely packed regions were essentially immobile. Four trimers in a rather solid association are outlined (1) in correspondence to the molecules outlined (1) in frame t = 1908 ms in (a). A highly mobile single molecule is outlined (2) corresponding to the molecule outlined (2) in frame t = 2385 ms in (a).