1. A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry, Chemistry, and Pharmacology, Vanderbilt Institute of Chemical Biology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
2. Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
3. Northeastern Collaborative Access Team, Argonne National Laboratory, Argonne, Illinois 60439, United States