1. Department of Bionanotechnology, Hanyang University, Ansan 155-88, Korea
2. Department of Neuroscience, University of Copenhagen, Copenhagen DK-2200, Denmark
3. Beijing Advanced Innovation Center for Structural Biology, School of Medicine, School of Pharmaceutical Sciences, Tsinghua University, 100084 Beijing, China
4. Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, United States
5. Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305, United States
6. Department of Life Sciences, Imperial College London, London, SW7 2AZ, United Kingdom