1. Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, U.K.
2. Department of Biochemistry & Structural Biology, Center for Molecular Protein Science, Lund University, PO box 124, 221 00 Lund, Sweden
3. Department of Physics, Cavendish Laboratory, Cambridge CB3 0HE, U.K.