1. Contribution from the Department of Chemistry, University of California, Berkeley, California 94720-1460, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, Department of Chemistry, University of San Diego, 5998 Alcala Park, San Diego, California 92110, Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, and Division of Chemistry & Chemical Engineering, California Institute of Technology...