1. Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, FL 33136, USA.
2. National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA 92093–06083, USA.
3. Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093–06083, USA.