1. Department of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW Cambridge, U.K.
2. Stratingh Institute, University of Groningen, Nijenborgh 4, Groningen, The Netherlands
3. Cancer Research U.K., Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, U.K.
4. School of Clinical Medicine, University of Cambridge, Addenbrooke’s Hospital, Hills Road, Cambridge CB2 0SP, U.K.