1. University of California, San Diego, Skaggs School of Pharmacy and Pharmaceutical Sciences, La Jolla, CA 92093, USA.
2. Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
3. Department of Chemistry, Bridge Institute.
4. Department of Biological Sciences, Bridge Institute, University of Southern California, Los Angeles, CA 90089, USA.