1. Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA.
2. Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
3. Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA.
4. Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA.
5. Department of Computer Science, Stanford University, Stanford, CA 94305, USA.
6. Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA 94305, USA.
7. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.