1. Department of Chemistry and Biochemistry, 160 Hughes Hall, Miami University, Oxford, Ohio 45056, Department of Chemistry and Chemical Biology, B80 Clark Hall, MSC03 2060, University of New Mexico, Albuquerque, New Mexico 87131-0001, and National Biomedical EPR Center, Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226-0509