1. Department of Crystallography, Birkbeck College, University of London, London WC1E 7HX, UK
2. Institute for Storage Ring facilities (ISA), Aarhus University, Aarhus, Denmark
3. Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
4. School of Biological and Chemical Sciences, Queen Mary, University of London, London E1 4NS, UK