1. Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, Departments of Chemistry and Molecular and Cellular Biology, QB3 Institute, and Division of Physical Biosciences, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720-3220, and National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310