1. Department of Chemistry, The Johns Hopkins University Charles and 34th Streets, Baltimore, Maryland 21218 Department of Biochemistry and Molecular Biology Oregon Graduate Institute, Beaverton, Oregon 97006 Department of Physics, Emory University Atlanta, Georgia 30322 Department of Pharmacology and Molecular Sciences The Johns Hopkins School of Medicine Baltimore, Maryland 21205 Institute für Anorganische Chemie, University of Basel CH-4056 Basel, Switzerland