1. Department of Biophysical Chemistry, Max-Planck-Institut für Biophysik, Kennedyallee 70, D-60596 Frankfurt am Main, Germany, Department of Pharmacology, Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo, 060, Japan, and Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224