1. Department of Molecular and Integrative Physiology, Center for Biophysics and Computational Biology, and National Center for Supercomputing Applications, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana−Champaign, Urbana, Illinois 61801, Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, California 92093, and Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, Rockville, Maryland 20850