1. Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Schuster Building, Manchester M13 9PL, U.K.
2. ISIS Neutron Facility, STFC, Chilton, Didcot OX11 0QZ, U.K.
3. MedImmune LLC, Gaithersburg, Maryland 20878, United States
4. MedImmune Ltd, Sir Aaron Klug Building, Granta Park, Cambridge CB21 6GH, U.K.