1. Department of Chemistry, Stanford University, Stanford, California 94305, United States
2. Department of Chemistry, University of California at Davis, Davis, California 95616, United States
3. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
4. Department of Biochemistry, The University at Buffalo, Buffalo, New York 14214, United States