1. Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, United States
2. Department of Chemistry and Biochemistry, Center for Optical, Molecular and Quantum Science, University of Oregon, Eugene, Oregon 97403, United States
3. Department of Physics, Center for Optical, Molecular and Quantum Science, Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, United States