Fluorescence Recovery After Photobleaching (FRAP)
FRAP is based on the principal of observing the rate of recovery of fluorescence due to the movement of a fluorescent marker into an area of the membrane which contains this same marker but which has been rendered non-fluorescent via an intense photobleaching pulse of laser light. The two-dimensional diffusion coefficient (D) of the fluorophore is related to both its rate and extent of recovery. FRAP has proved to be a popular means to assess the structure of artificial and biological membranes.
FRAP is being used to measure the lateral diffusion of various membrane or cytoplasmic constituents. FRAP has been used to characterize the mobility of plasma membrane receptors and lipids under various condition; e.g. during cell locomotion and hypoxic injury. Results from these studies have yielded new descriptions of different classes of membrane components in terms of lateral diffusional mobility which underlies cell injury following hypoxia. FRAP has also been used to examine cytoskeletal dynamics and characterize sperm plasma membranes before and after capacitation.