1. Department of Chemistry, Stony Brook University, Nicolls Road, Stony Brook, New York 11790, United States
2. Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, New York 11794, United States
3. Institute of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, U.K.