EXAFS STUDIES OF NITROGENASE AND RELATED SYSTEMS: AN OVERVIEW. Keith O. Hodgson, Department of Chemistry Stanford University, Stanford, CA 94305

X-ray absorption edge and extended fine structure (EXAFS) studies contributed significantly to the early definition of particularly the Mo- Fe-S containing cofactor (FeMoco) of the MoFe protein of the nitrogenase system both within and outside the protein (in its isolated form). The x- ray crystal stucture results have now defined the overall protein structure and the relationships and structures of the metal-containing prosthetic groups in the resting state. However, much remains to be learned about how the electronic structure of the FeMoco mediates electron transfer and dinitrogen reduction and XAS spectroscopy is now being used to probe this question. Edge studies provide information on electronic structure including covaleny and electronic distribution as a function of oxidation state. EXAFS results incorporating multiple scattering analyses provide a specific probe of the metrical details (including longer range distances) and in some cases geometry of the FeMoco. This talk will review some of these recent advances as they provide insights into the structure/function of the nitrogenase system.