1. Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States
2. School of Biological Sciences and Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland 1142, New Zealand
3. Diabetes Research Program, NYU School of Medicine, 522 First Avenue, New York, New York 10016, United States
4. Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom