1. Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
2. School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, United States
3. Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96813, United States
4. Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, California 92697, United States
5. Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States