Microfluorometry of cell membrane dynamics.

Membranes of living cells are characterized by a combination of conventional and total internal reflection fluorescence microscopy (TIRFM) using the membrane marker laurdan. In the first case, all cellular membranes are assessed simultaneously, whereas in the second case, the plasma membrane is excited selectively by the evanescent electromagnetic field of a laser beam. A spectral shift depending on the phase of membrane lipids is used to characterize membrane stiffness, which decreases with temperature and increases with the amount of cholesterol. Spectral properties are evaluated and displayed as microscopic images. (c) 2006 International Society for Analytical Cytology.