Spectroscopic Studies of Blue Copper and Iron Sulfur Electron Transfer Active Sites

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Professor Solomon of Stanford University will conduct studies designed to elucidate the spectroscopy of certain metalloproteins under support from the Inorganic, Bioinorganic and Organometallic Program. The proteins of interest are those that contain Blue Copper and Iron Sulfur sites, and the information to be obtained is a more detailed description of their electronic structures and the contributions of electronic structure to the electron-transfer reactivity of these active sites. Spectral methods to be used include polarized absorption, variable-temperature magnetic circular dichroism, single crystal multifrequency EPR, resonance Raman, variable energy PES, and X-ray absorption. These experimental methods will be combined with ligand field and SCF-Xalpha-SW calculations. These techniques will be applied in studies of simple coordination complexes of Fe(II), Fe(III), Cu(I) and Cu(II). The information obtained from these studies will then allow evaluation of the influence of electronic structure on the unusual reduction potentials and rapid rates of electron transfer of the real proteins. In addition, an analogous set of experiments will be conducted on a variety of mutant and modified blue copper proteins in order to test the deductions derived from the model studies. %%% A diverse array of sophisticated spectroscopic techniques will be used in order to learn about the bonding at the active sites of two classes of metal-containing proteins. These proteins contain either copper-sulfur or iron-sulfur centers, are found in most organisms, and function in the physiological electron transport chains. The approach to be taken will entail detailed experimental and theoretical study of simple models of the active sites, as well as experimental study of a series of modified copper proteins. The information obtained will lead to an understanding of how the bonding at the metal sites controls the rates and energetics of reactions of these proteins.