There is increasing evidence to suggest that biological oxidation-reduction reactions are fundamentally different from reactions occurring in homogeneous solution. Specifically, the protein matrix is thought to allow formation of unusual metal ion coordination environments and restrict mobilities of electron donor-acceptor pairs. Potential consequences of these structural constraints are that electron transfer must occur over relatively large distances and stabilization of functional multinuclear aggregates essential to biological function can occur. One objective of the proposed research is to investigate the nature of redox reactions between copper(I) and detergent-solubilized ferrihemes. This work is based upon our identification of longlived reaction intermediates as heme-copper binuclear ions, which may serve as useful models for heme-copper pairs postulated to form the oxygen-binding site in cytochrome oxidase. Structural and kinetic analysis is proposed, using principally resonance Raman, EPR magnetic, and optical methods. A second objective is to build simple models useful for examining long-range redox processes. The basis for this work is derived from recent observations by us and other that photoinitiated electron transfer can occur over relatively large distances about 20 angstroms and that electron exchange can apparently occur across artificial phospholipid bilayer membranes. A third objective is to examine the resonance Raman spectra of isolated cytochrome oxidase subunits that contain bound heme a and copper ions to determine the structural basis for discrimination between the cytochrome a and a3 sites in the intact oxidase and to seek evidence for structural organization analogous to the simple micellar heme-copper(I) models. Successful completion of the experiments should provide clarification of the nature of long-range redox processes, as well as heme reactivity towards copper and its relation to cytochrome oxidase function.
