The overall goal of this project is to determine important aspects of the role of intramolecular and intermolecular structure in biological energy conversion. The structural studies proposed here concern the determination of the cylindrically-averaged profile structures if the natural membrane~s~s molecular components within specific bimolecular complexes involved in energy conversion at moderate resolution (about 10 A); the spatial relationships between these components, relative to each other and to the overall profile structure of the membrane; and the spatial relationships among the redox centers associated with these components, relative to each other within these complexes and relative to the overall profile structure of the membrane, with an accuracy of plus/minus1-2A. In addition, analogous structural studies will be extended to the determination of the 3-D structures of three, much less structurally complex, artificial metalloprotein ~maquettes~ designed to mimic key characteristics of such charge- separating redox enzymes. Through a correlation of such structural parameters with the capabilities of these natural and artificial components and/or complexes thereof to exhibit efficient electron transport and the generation of transmembrane electrochemical potentials (and ultimately the synthesis of ATP) in reconstituted, vectorially-oriented single membrane systems, we hope to gain substantial insight into the mechanism of energy coupling in biological membranes.