1. Department of Chemistry, Oregon
Center for Optics, Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, United States
2. Department of Chemistry and
Chemical Biology, Harvard University, Cambridge,
Massachusetts 02138, United States
3. Department of Chemistry and Biochemistry,
and The Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California
92093, United States