1. Mayo Clinic Arizona (M.B.C., D.L.R., D.F.S.), S. C. Johnson Research Building, Scottsdale, Arizona 85259;
2. Border Biomedical Research Center and Department of Biological Sciences (M.B.C.), University of Texas at El Paso, El Paso, Texas 79968;
3. Institut fur Organische Chemie und Biochemie (M.H., F.S., J.B.), Technische Universitat Munchen, 85747 Garching, Germany