The proposed research will apply methods from synthetic and physical inorganic chemistry to selected transition metal proteins and enzymes possessing unusual structural features, as evidenced by their spectroscopic or catalytic properties. The objectives of the research are to understand how transition metal ions are coordinated in these systems, and how this chemical environment leads to their distinctive spectroscopic and catalytic properties. This will be accomplished by the preparation of potential synthetic analogs of the metal sites of certain copper and iron-sulfur proteins, allowing the properties of the metal site in the absence of the protein to be determined and the effect of specific perturbations of the metal site to be investigated, and by fundamental physical and chemical studies on a series of novel iron-containing hydrolytic enzymes. Thus, the synthesis and characterization of copper complexes of branched polydentate imidazole- and sulfur-containing ligands as models for the blue copper proteins and the binuclear sites of the multi-copper oxidases and hemocyanin will be examined. The former constitute a unique and biologically widespread class of high potential electron transfer agents; the latter are involved in oxygen activation and transport. Iron-sulfur clusters containing covalently attached flavin and porphyrin moieties will be prepared in order to allow an examination of factors affecting electron transfer and other interactions between such species. Many enzymes, as well as components of the mitochondrial electron transport chain, are known to contain and transfer electrons between similar units. The purple acid phosphatase from beef spleen and the purple alkaline phosphatase from Micrococcus sodonensis will be examined by physical and chemical methods, to determine the nature of the distinctive purple iron chromophore and its role in catalysis. These enzymes are unusual among iron enzymes in that they catalyze a hydrolytic rather than a redox reaction.