1. Department of Chemistry, Princeton University, Princeton, New Jersey 08544,
United States
2. Cornell High
Energy Synchrotron
Source, Wilson Laboratory, Cornell University, Ithaca, New York 14853, United States
3. Max-Planck Institute for Bioinorganic Chemistry, Stiftstrasse 34-36, D-45470
Mülheim an der Ruhr, Germany
4. Department of Chemistry and Chemical
Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States