Dr. Munck is continuing his state of the art Mossbauer and EPR studies on iron-sulfur proteins. He is also developing a spin-coupling Hamiltonian for valence-delocalized systems. Work performed in the previous grant period has lead to the recognition that spin-coupling in valence-delocalized systems requires an additional mechanism, called double-exchange. in attempting to buttress the new spin Hamiltonian by microscopic theory, Dr. Munck discovered a mechanism of exchange coupling (exchange-transfer). He plans to now describe the various states of iron in as much detail as possible. Mossbauer and EPR spectroscopy, used in conjunction, with each other are well suited to elucidate the active site properties of iron-sulfur clusters. A variety of iron-sulfur proteins are being studied, including nitrogenase, an enzyme system capable of reducing atmospheric nitrogen to ammonia.***//
