1. Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, U.K.
2. Nuffield Department of Clinical Medicine, Structural Genomics Consortium, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 3TA, U.K.
3. Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
4. Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, U.K.
5. Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States
6. Department of Chemistry, Colorado State University, 1301 Center Ave, Ft. Collins, Colorado 80523-1872, United States