title: Spinning-Spot Shadowless TIRF Microscopy.
abstract: Total internal reflection fluorescence (TIRF) microscopy is a powerful tool for visualizing near-membrane cellular structures and processes, including imaging of local Ca2+ transients with single-channel resolution. TIRF is most commonly implemented in epi-fluorescence mode, whereby laser excitation light is introduced at a spot near the periphery of the back focal plane of a high numerical aperture objective lens. However, this approach results in an irregular illumination field, owing to interference fringes and scattering and shadowing by cellular structures. We describe a simple system to circumvent these limitations, utilizing a pair of galvanometer-driven mirrors to rapidly spin the laser spot in a circle at the back focal plane of the objective lens, so that irregularities average out during each camera exposure to produce an effectively uniform field. Computer control of the mirrors enables precise scanning at 200 Hz (5ms camera exposure times) or faster, and the scan radius can be altered on a frame-by-frame basis to achieve near-simultaneous imaging in TIRF, widefield and 'skimming plane' imaging modes. We demonstrate the utility of the system for dynamic recording of local inositol trisphosphate-mediated Ca2+ signals and for imaging the redistribution of STIM and Orai proteins during store-operated Ca2+ entry. We further anticipate that it will be readily applicable for numerous other near-membrane studies, especially those involving fast dynamic processes.
authors: Department of Neurobiology & Behavior, University of California Irvine, Irvine, CA, 92697, United States of America.
authors: Kyle L
authors: KL
authors: Ellefsen
authors: Department of Physiology & Biophysics, University of California Irvine, Irvine, CA, 92697, United States of America.
authors: Joseph L
authors: JL
authors: Dynes
authors: Department of Neurobiology & Behavior, University of California Irvine, Irvine, CA, 92697, United States of America; Department of Physiology & Biophysics, University of California Irvine, Irvine, CA, 92697, United States of America.
authors: Ian
authors: I
authors: Parker
mesh_terms: D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002522:Chlorocebus aethiops; D005453:Fluorescence; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008029:Lighting; D008565:Membrane Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence / Q000295:instrumentation* / Q000379:methods*; D009363:Neoplasm Proteins / Q000378:metabolism; D000071740:ORAI1 Protein; D055620:Optical Phenomena; D012542:Scattering, Radiation; D000071737:Stromal Interaction Molecule 1
chemical_list: D015220:Calcium Channels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D002118:Calcium