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