Nuts and Bolts of Excitation Energy Migration and Energy Transfer

The applications of Fluorescence Resonance Energy Transfer (FRET) have expanded tremendously in the last 25 years, and the technique has become a staple technique in many biological and biophysical fields. Our understanding of photosynthesis is tightly coupled to our understanding of the transfer of captured energy from the absorption of photons, and following the energy flow through the complex maize of chemical reactions utilizing this energy. Many of these steps involve resonance energy transfer. In this chapter, we have examined some general salient features of resonance energy transfer by stressing the kinetic competition of the FRET pathway with all other pathways of de-excitation. This approach emphasizes many of the biotechnological and biophysical uses of FRET, as well as emphasizing the important competing processes and biological functions of FRET in photosynthesis. Many publications appear weekly using FRET and most of the applications use FRET as a spectroscopic research tool. Photosynthesis holds the unique position that much of the original interest in FRET was derived from attempts to understand the extremely efficient migration of captured light energy to the reaction center of photosynthetic systems, and photosynthesis utilizes energy transfer as a fundamental mechanism in order to carry out its biological function.