1. Department of Chemistry & Biochemistry, University of California San Diego, La Jolla, CA 92093‐0365, USA
2. Howard Hughes Medical Institute, University of California San Diego, La Jolla, CA 92093‐0365, USA
3. Center for Theoretical Biological Physics, University of California San Diego, La Jolla, CA 92093, USA
4. Department of Pharmacology, University of California San Diego, La Jolla, CA 92093‐0365, USA