title: Molecular mobility on the cell surface.
abstract: Many measurements of lateral diffusion of proteins and lipids on cell membranes and lipid model membranes have become available through application of fluorescence photobleaching recovery methods. A puzzling aspect of these results is slow diffusion and partial immobilization of protein molecules on the cell surface. Observed protein diffusion coefficients on vertebrate structural tissue cells are consistently D less than or equal to 10(-10) cm2/s, while lipid analogues diffuse with D approx. 10(-8) cm2/s. Substantial fractions of the cell membrane proteins are not diffusible. In a pure viscous membrane, theoretical fluid dynamics has suggested only small differences between lipid and protein diffusion coefficients. Measurements of protein diffusion in model membranes recently showed D less than or equal to 10(-9) cm2/s, as expected. Recent experiments on cell membranes show that uncoupling of the membrane from the cytoskeleton by formation of blebs releases the membrane protein molecules so that diffusion is enhanced to D greater than or equal to 10(-9) cm2/s and the non-diffusible fraction is eliminated.
mesh_terms: D000199:Actins; D002478:Cells, Cultured; D004058:Diffusion; D008027:Light; D008051:Lipid Bilayers; D008563:Membrane Lipids / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D011485:Protein Binding; D011955:Receptors, Drug; D013050:Spectrometry, Fluorescence; D013997:Time Factors; D014783:Viscosity
chemical_list: D000199:Actins; D008051:Lipid Bilayers; D008563:Membrane Lipids; D008565:Membrane Proteins; D011955:Receptors, Drug