1. Department of Chemistry, University of York, Heslington, YO10 5DD, UK
2. York Biomedical Research Institute, University of York, Heslington, YO10 5DD, UK
3. Department of Biology, University of York, Heslington, YO10 5DD, UK
4. Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK