1. Department of Chemistry and Biochemistry, 112 Hughes Hall, Miami University, Oxford, Ohio 45056, Department of Chemistry, 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