1. Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States, Japan Synchrotron Radiation Research Institute, SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan, and Department of Applied Science, University of California, Davis, California 95616, United States