1. School of Chemistry and Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, U.K.
2. Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, U.K.
3. Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115, United States
4. Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa 50011, United States