The principal objective of this project is to understand in detail the mechanisms whereby Zn/Cu, Fe, and Mn containing superoxide dismutases catalyze the reaction, 202-+2H+ is greater than H2O2+O2. Our procedures involve the application of a variety of physical techniques ranging from x-ray crystallography to obtain three-dimensional structures to spectroscopic measuements to characterize the electronic structure of these metalloproteins. Kinetic mechanisms are being explored using a stopped-flow spectrophotometer specially designed for the study of superoxide in aqueous media. Simple recombinant DNA technqiues are being applied to the study of enzyme mechanisms and physiological function of these proteins.