School of Biological and Chemical Sciences, Queen Mary, University of London, London E1 4NS, UK. j.lees@mail.cryst.bbk.ac.uk <j.lees@mail.cryst.bbk.ac.uk>|School of Biological and Chemical Sciences, Queen Mary, University of London, London E1 4NS, UK. j.lees@mail.cryst.bbk.ac.uk <j.lees@mail.cryst.bbk.ac.uk>|School of Biological and Chemical Sciences, Queen Mary, University of London, London E1 4NS, UK. j.lees@mail.cryst.bbk.ac.uk <j.lees@mail.cryst.bbk.ac.uk>|School of Biological and Chemical Sciences, Queen Mary, University of London, London E1 4NS, UK. j.lees@mail.cryst.bbk.ac.uk <j.lees@mail.cryst.bbk.ac.uk>