This award will support collaborative research between Dr. C. Russell Hille, Ohio State University and Dr. Robert F. Anderson, Gray Laboratory, Mount Vernon Hospital, Middlesex, England. The investigators will carry out a study of the oxidation-reduction behavior of milk xanthine oxidase, a well-defined enzyme of importance in metabolism. Xanthine oxidase contains four sites capable of reversibly accepting reducing equivalents during catalytic turnover. A total of six reducing equivalents are required to fully reduce all these centers. The enzyme thus provides an excellent opportunity to examine the principles governing biological electron transfer as a system in which the sites are held at a fixed distance and orientation to one another, within a more or less rigid polypeptide matrix. The principle technique to be used in this work is pulse radiolysis, a technique whose utility in studying biochemical oxidation-reduction problems is not widely appreciated. It is anticipated that the results of this work will have implications beyond xanthine oxidase alone, and will prove relevant to other more complex systems, such as those occurring in the mitochondrion and chloroplast. The demonstration of the general suitability of pulse radiolysis in the study of intra-and interprotein electron transfer would provide the field with a powerful new technique for the study of these fundamental biological processes. The British collaborator is a recognized expert in pulse radiolysis and has a long standing interest in the application of pulse radiolysis to the study of electron transfer processes in biologically important molecules. The project will also benefit from state-of-the art pulse radiolysis facilities available at the Gray Laboratory. Dr. Hille's expertise is in oxidation-reduction enzymology and enzyme kinetics.
