1. Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
2. Department of Biology, Chemistry, and Pharmacy, Institute of Chemistry and Biochemistry, Freie Universität Berlin, D-14195 Berlin, Germany
3. Department of Genetics, Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, United States