The Structure of Cell Membranes Dr. Robert Farley 1. Restricted lateral mobility of lipids and proteins in cell membranes Revisiting the fluid mosaic model of membranes . Ken Jacobson, Erin D. Sheets, Rudolf Simson.
Data are average of hundreds of thousands of molecules.
Careful analysis needed to distinguish between nonrandom and random movements. Optical forces on the bead, which are directed toward the highest intensity of the beam, trap the particle. By moving the laser or microscope stage the labeled protein can be dragged across the plasma membrane until it encounters a barrier or obstacle that causes the bead to escape the trap. SPT shows that lipids and a fraction of the labeled protein population can diffuse freely, but other protein movements are more complicated than originally envisioned. Partial destruction of the cytoskeleton decreases the fraction of confined molecules, and truncation of the cytoplasmic domain leads to less confined diffusion.