Fluorescence Energy Transfer in Membrane Biochemistry

Abstract

In the two decades since its first application to biological systems (Stryer and Haugland, 1967), fluorescence energy transfer has become a standard technique for measuring distances in biological systems. Early studies usually measured distances between a single donor and a single acceptor each at a specific location. The extension to transfer between multiple donors and multiple acceptors has proven quite useful for the study of multienzyme complexes (Hahn and Hammes, 1978; Angelides and Hammes, 1979). Most of the applications to membrane biochemistry also represent a situation in which multiple donors and multiple acceptors are present. These applications have a long history as well, starting with the initial study of energy transfer from chlorophyll in monomeric films (Tweet et al., 1964). This early work relied heavily on Foerster’s derivation of energy transfer between multiple acceptors and multiple donors in three dimensions (Foerster, 1949) and derived the appropriate expression for two dimensions. Unfortunately, these results went unnoticed and identical expressions have been derived in several subsequent works. The first studies on lipid bilayer systems were aimed at determining the depth of a chromophore in the membrane (Shaklai et al., 1977) or at determining the surface density of an acceptor (Fung and Stryer, 1978). These have been the two observables of major interest in membrane systems. Energy transfer has subsequently been used to monitor a variety of membrane processes and interactions. A representative example of the diversity of applications is given in Table I. Additional references may be found in recent reviews (Hammes, 1981; Blumberg, 1985; Tron et al., 1987).