1. Contribution from the Department of Pharmacology, Center for Biomedical EPR Spectroscopy and Imaging, The Davis Heart and Lung Research Institute, and the Division of Cardiovascular Medicine, Department of Internal Medicine, College of Medicine, and Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, and Laboratory TRACES, JE 2421, Aix-Marseille Universite, Faculte St. Jerome, 13397 Marseille cedex 20, France