1. Department of Pathology, The University of Chicago, Chicago, Illinois 60637, United States
2. BioCAT and μCoSM, Pritzker Institute of Biomedical Science and Engineering, and CSRRI and Department of Biological Chemical and Physical Sciences, Illinois Institute of Technology, Chicago, Illinois 60616, United States
3. Biomolecular NMR Facility, Shared Research Facilities, The University of Chicago, Chicago, Illinois 60637, United States
4. Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States
5. Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637, United States