1. Center for Structural Biology, Department of Chemistry, Vanderbilt University, 5140 Medical Research Building III, 465 21st Avenue South, Nashville, Tennessee 37232-8725, Department of Chemistry, University of North Carolina, Campus Box 3290, Chapel Hill, North Carolina 27599-0001, Laboratory of Structural Biology, National Institute of Environmental Health Science, Research Triangle Park, 12 Davis Drive, Chapel Hill, North Carolina 27709-5900, Center for Biophysics and Computational Biology, University...