1. Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
2. Graduate Program of Biochemistry, Molecular and Cell Biology, Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, United States
3. Howard Hughes Medical Institute, Department of Chemistry and Chemical Biology, Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, United States