1. Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
2. Department of Chemistry and California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, California 94720, United States
3. Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
4. Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, United States
5. Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States