1. University Chemical Laboratory, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom, School of Clinical Medicine, University of Cambridge, Cambridge CB2 0SP, United Kingdom, Department of Chemistry and Biochemistry, University of Sussex, Falmer Brighton BN1 9QJ, United Kingdom, and The Cancer Research UK, Biomolecular Structure Group, The School of Pharmacy, University of London, 29-39 Brunswick Square, London WC1N 1AX, United Kingdom