374 Abstracts

E029 NEW INSIGHTS INTO THE STRUCTURE AND REACTIVITY OF FeMoco USING X-RAY ABSORPTION AND SCATTERING TECHNIQUES

Lingling Chen,a David Eliezer,b Isaac Liu,a Hirotsugu Tsuruta,~ Narasaiah Gavini,d William E. Newton,e Barbara K. Burgess, Patrick Frank,a Britt Hedrmf and Keith 0. Hodgsonapc

aDepartment of Chemistry, Stanford University, Stanford, CA 94305 bDe- partment of Applied Physics, Stanford University, Stan$ord, CA 94305 ‘Stanford Synchrotron Radiation Laboratory, Stanford University, SLAC, M.S. 69, P.O. Box 4349, Stanford, CA 94309 dDepartment of Molecular Bi- ology and Biochemistry, University of California at Irvine, Irvine, CA 92717 eDepartment of Biochemistry and Nutrition, Virginia Polytechnical Institute, Blacksburg, VA 24061

Recent experimental results have provided new insights into the solu- tion structure of FeMoco and how it compares with the cluster in the active MoFe-protein. X-ray absorption edge and EXAFS experiments have been carried out at the S, Fe, and MO edges of FeMoco as well as for a number of relevant inorganic cluster complexes. Analysis of EXAFS data has utilized a new approach based on theme&al parameters and multiple scattering analy- sis (called GNXAS) to provide more reliable information about longer-range interaction in the polynuclear FeMo cluster. Additonal information has been determined about electronic structural changes upon redox chemistry and the binding of exogeneous ligands. X-ray scattering (XAS) measurments can be used to investigate the size and shape of molecules in solution. Such XAS studies have been used to probe the structure of FeMoco in solution and how it is altered by redox and ligand-binding. Taken together, these re- sults help provide information on the structural and functional role of the various sub-cluster components of FeMoco.

This work is supported by grants from N?H and NSF. The x-ray ab- sorption and scattering data were measured at the Stanford Synchrotron Ra- diation Laboratory which is supported by the U.S. Department of Energy and the NIH.