Name: conducting multiple imaging modes with one fluorescence microscope
Uploaded: 2018-10-28T13:00:00
Description: Watch this Scientific Journal Video about Conducting Multiple Imaging Modes with One Fluorescence Microscope at JoVE.com

J.F. acknowledges support from the Searle Scholars Program and the NIH Director&#39;s New Innovator Award. The authors acknowledge useful suggestions from Paul Selvin&#39;s lab (University of Illinois, Urbana-Champaign) for positioning the 3-D lens.

1. Microscope Design and Assembly
<ol>
	<li>Excitation path 
	NOTE: The excitation path includes lasers, differential interference contrast (DIC) components, the microscope body, and its illumination arm.
	<ol>
		<li>Prepare a vibration-isolated optical table. For example, a structural damping table of 48 x 96 x 12&#8217;&#8217; gives enough space for all the components. 
		NOTE: Build the set-up in a room with temperature control (e.g., 21.4 &#177; 0.55 &#176;C). Temperature stabili...

<ol>
	<li>Lipson, S. G., Lipson, H., Tannhauser, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Optical physics. , (1995).</li><li>T&#246;r&#246;k, P., Wilson, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rigorous+theory+for+axial+resolution+in+confocal+microscopes.">Rigorous theory for axial resolution in confocal microscopes.</a> Optics Communications. 137 (1-3), 127-135 (1997).</li><li>Klar, T. A., Hell, S. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Subdiffraction+resolution+in+far-field+fluorescence+microscopy.">Subdiffraction resolution in far-field fluorescence microscopy.</a> Optics Letters. 24 (14), 954-956 (1999).</li><li>Hell, S. W., Wichmann, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Breaking+the+diffraction+resolution+limit+by+stimulated+emission:+stimulated-emission-depletion+fluorescence+microscopy.">Breaking the diffraction resolution limit by stimulated emission: stimulated-emission-depletion fluorescence microscopy.</a> Optics Letters. 19 (11), 780-782 (1994).</li><li>Gustafsson, M. G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surpassing+the+lateral+resolution+limit+by+a+factor+of+two+using+structured+illumination+microscopy.">Surpassing the lateral resolution limit by a factor of two using structured illumination microscopy.</a> Journal of Microscopy. 198 (2), 82-87 (2000).</li><li>Gustafsson, M. G. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+resolution+doubling+in+wide-field+fluorescence+microscopy+by+structured+illumination.">Three-dimensional resolution doubling in wide-field fluorescence microscopy by structured illumination.</a> Biophysical Journal. 94 (12), 4957-4970 (2008).</li><li>Schermelleh, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Subdiffraction+multicolor+imaging+of+the+nuclear+periphery+with+3D+structured+illumination+microscopy.">Subdiffraction multicolor imaging of the nuclear periphery with 3D structured illumination microscopy.</a> Science. 320 (5881), 1332-1336 (2008).</li><li>Rust, M. J., Bates, M., Zhuang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sub-diffraction-limit+imaging+by+stochastic+optical+reconstruction+microscopy+(STORM).">Sub-diffraction-limit imaging by stochastic optical reconstruction microscopy (STORM).</a> Nature Methods. 3 (10), 793-795 (2006).</li><li>Betzig, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+intracellular+fluorescent+proteins+at+nanometer+resolution.">Imaging intracellular fluorescent proteins at nanometer resolution.</a> Science. 313 (5793), 1642-1645 (2006).</li><li>Balzarotti, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanometer+resolution+imaging+and+tracking+of+fluorescent+molecules+with+minimal+photon+fluxes.">Nanometer resolution imaging and tracking of fluorescent molecules with minimal photon fluxes.</a> Science. 355 (6325), 606-612 (2017).</li><li>Vaughan, J. C., Jia, S., Zhuang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrabright+photoactivatable+fluorophores+created+by+reductive+caging.">Ultrabright photoactivatable fluorophores created by reductive caging.</a> Nature Methods. 9 (12), 1181-1184 (2012).</li><li>Ha, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+the+interaction+between+two+single+molecules:+fluorescence+resonance+energy+transfer+between+a+single+donor+and+a+single+acceptor.">Probing the interaction between two single molecules: fluorescence resonance energy transfer between a single donor and a single acceptor.</a> Proceedings of the National Academy of Sciences of the United States of America. 93 (13), 6264-6268 (1996).</li><li>Roy, R., Hohng, S., Ha, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+practical+guide+to+single-molecule+FRET.">A practical guide to single-molecule FRET.</a> Nature Methods. 5 (6), 507-516 (2008).</li><li>Huang, B., Wang, W., Bates, M., Zhuang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+super-resolution+imaging+by+stochastic+optical+reconstruction+microscopy.">Three-dimensional super-resolution imaging by stochastic optical reconstruction microscopy.</a> Science. 319 (5864), 810-813 (2008).</li><li>Hua, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+improved+surface+passivation+method+for+single-molecule+studies.">An improved surface passivation method for single-molecule studies.</a> Nature Methods. 11 (12), 1233-1236 (2014).</li><li>Fei, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+biochemistry.+Determination+of+in+vivo+target+search+kinetics+of+regulatory+noncoding+RNA.">RNA biochemistry. Determination of in vivo target search kinetics of regulatory noncoding RNA.</a> Science. 347 (6228), 1371-1374 (2015).</li><li>Raj, A., van den Bogaard, P., Rifkin, S. A., van Oudenaarden, A., Tyagi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+individual+mRNA+molecules+using+multiple+singly+labeled+probes.">Imaging individual mRNA molecules using multiple singly labeled probes.</a> Nature Methods. 5 (10), 877-879 (2008).</li><li>Stracy, M., Kapanidis, A. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-molecule+and+super-resolution+imaging+of+transcription+in+living+bacteria.">Single-molecule and super-resolution imaging of transcription in living bacteria.</a> Methods. 120, 103-114 (2017).</li><li>Wang, S., Moffitt, J. R., Dempsey, G. T., Xie, X. S., Zhuang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+and+development+of+photoactivatable+fluorescent+proteins+for+single-molecule-based+superresolution+imaging.">Characterization and development of photoactivatable fluorescent proteins for single-molecule-based superresolution imaging.</a> Proceedings of the National Academy of Sciences of the United States of America. 111 (23), 8452-8457 (2014).</li><li>Sekar, R. B., Periasamy, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescence+resonance+energy+transfer+(FRET)+microscopy+imaging+of+live+cell+protein+localizations.">Fluorescence resonance energy transfer (FRET) microscopy imaging of live cell protein localizations.</a> The Journal of Cell Biology. 160 (5), 629-633 (2003).</li><li>Shi, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Super-resolution+microscopy+reveals+that+disruption+of+ciliary+transition-zone+architecture+causes+Joubert+syndrome.">Super-resolution microscopy reveals that disruption of ciliary transition-zone architecture causes Joubert syndrome.</a> Nature Cell Biology. 19 (10), 1178-1188 (2017).</li><li>Youn, Y., Ishitsuka, Y., Jin, C., Selvin, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+nanoimprint+lithography+for+drift+correction+in+super-resolution+fluorescence+microscopy.">Thermal nanoimprint lithography for drift correction in super-resolution fluorescence microscopy.</a> Optics Express. 26 (2), 1670-1680 (2018).</li></ol>

This hybrid microscope system eliminates the need to purchase multiple microscopes. The total cost for all parts, including the optical table, table installation labor, software, and workstation, is about $230,000. Custom-machined parts, including the mag lens and 3-D lens, cost around $700 (the cost depends on the actual charges at different institutes). Typical commercially available integrated systems for single-molecule detection-based SR microscopy cost more than $300,000 ~ 400,000 and are not readily available for ...

Fluorescence microscopes are important tools for the modern biological science research and fluorescent imaging is routinely performed in many biology laboratories. By tagging biomolecules of interest with fluorophores, we can directly visualize them under the microscope and record the time-dependent changes in localization, conformation, interaction, and assembly state in vivo or in vitro. Conventional fluorescence microscopes have a diffraction-limited spatial resolution, which is ~200 - 300 nm in the lateral direction and ~500 - 700 nm in the axial direction1,2, and are, therefore, limited to imaging at the 100s of nanometers-to-micron scale. In order to reveal finer details in the molecular assembly or organization, various SR microscopies that can break the diffraction limit have been developed. Strategies used to achieve SR include non-linear optical effects, such as stimulated emission depletion (STED) microscopy3,4 and structured illumination microscopy (SIM)5,6,7, stochastic detection of single molecules, such as stochastic optical reconstruction microscopy (STORM)8 and photoactivated localization microscopy (PALM)9, and a combination of both, such as MINFLUX10. Among these SR microscopies, single-molecule detection-based SR microscopes can be relatively easily modified from a single-molecule microscope set-up. With repetitive activation and imaging of photoactivatable fluorescent proteins (FPs) or photo-switchable dyes tagged on biomolecules of interest, spatial resolution can reach 10 - 20 nm11. To gain information on molecular interactions and conformational dynamics in real-time, angstrom-to-nanometer resolution is required. smFRET12,13 is one approach to achieve this resolution. Generally, depending on the biological questions of interest, imaging methods with different spatial resolutions are needed.
Typically, for each type of imaging, specific excitation and/or emission optical configuration is needed. For instance, one of the most commonly used illumination methods for single-molecule detection is through total internal reflection (TIR), in which a specific excitation angle needs to be achieved either through a prism or through the objective lens. For smFRET detection, emissions from both donor and acceptor dyes need to be spatially separated and directed to different parts of the electron-multiplying, charge-coupled device (EMCCD), which can be achieved with a set of mirrors and dichroic beam splitters placed in the emission path. For three-dimensional (3-D) SR imaging, an optical component, such as a cylindrical lens14, is needed to cause an astigmatism effect in the emission path. Therefore, homebuilt or commercially available integrated microscopes are, usually, functionally specialized for each type of imaging method and are not flexible to switch between different imaging methods on the same set-up. Here we present a cost-effective, hybrid system that provides adjustable and reproducible switches between three different imaging methods: conventional epi-fluorescent imaging with diffraction-limited resolution, single-molecule detection-based SR imaging, and multi-color single-molecule detection, including smFRET imaging (Figure 1A). Specifically, the set-up presented here contains fiber-coupled input lasers for multi-color excitation and a commercial illumination arm in the excitation path, which allows programmed control of the excitation angle, to switch between epi-mode and TIR mode. In the emission path, a removable homebuilt cylindrical lens cassette is placed within the microscope body for 3-D SR imaging, and a commercial beam splitter is placed before an EMCCD camera that can be selectively enabled to detect multiple emission channels simultaneously.

<table>
	<tbody>
		<tr>
			<td>Nikon Ti-E microscope stand</td>
			<td>Nikon</td>
			<td>Ti-E</td>
			<td></td>
		</tr>
		<tr>
			<td>Objective lens</td>
			<td>Nikon</td>
			<td>100X NA 1.49 CFI HP TIRF</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscopy imaging software</td>
			<td>Nikon</td>
			<td>NIS-Elements Advanced Research/HC</td>
			<td>HC includes &#34;JOBS&#34; module, the programmed acquisition module being used for SR imaging.</td>
		</tr>
		<tr>
			<td>The illumination arm</td>
			<td>Nikon</td>
			<td>Ti-TIRF-EM Motorized Illuminator Unit M</td>
			<td>This arm has a slot for a magnification lens</td>
		</tr>
		<tr>
			<td>Analyze block</td>
			<td>Nikon</td>
			<td>Ti-A</td>
			<td>This is installed in the filter turret.</td>
		</tr>
		<tr>
			<td>Z-drift correction system</td>
			<td>Nikon</td>
			<td>PFS</td>
			<td>This system is composed by the stepmotor on the objective nosepiece, IR LED, and a detector.</td>
		</tr>
		<tr>
			<td>Optical table top</td>
			<td>TMC</td>
			<td>783-655-02R</td>
			<td></td>
		</tr>
		<tr>
			<td>Optical table bases</td>
			<td>TMC</td>
			<td>14-426-35</td>
			<td></td>
		</tr>
		<tr>
			<td>647 nm laser</td>
			<td>Cobolt</td>
			<td>90346 (0647-06-01-0120-100)</td>
			<td>Modulated Laser Diode 647nm 120mW incl. laser head, CDRH control box, USB cable and PSU (Power Supply Unit)</td>
		</tr>
		<tr>
			<td>561 nm laser</td>
			<td>Coherent</td>
			<td>1280721</td>
			<td>OBIS 561nm LS 150mW Laser System</td>
		</tr>
		<tr>
			<td>488 nm laser</td>
			<td>Cobolt</td>
			<td>90308 (0488-06-01-0060-100)</td>
			<td>Modulated Laser Diode 488nm 60mW incl. laser head, CDRH control box, USB cable and PSU (Power Supply Unit)</td>
		</tr>
		<tr>
			<td>405 nm laser</td>
			<td>Crystalaser</td>
			<td>DL405-025-O</td>
			<td>405 (+/-5)nm, 25mW, Circular , M2 &#60;1.3, Low Noise, CW, TTL up to 20MHz. 2 BNC connectors for TTL &#38; Analog adjust</td>
		</tr>
		<tr>
			<td>Heat sink</td>
			<td>Cobolt</td>
			<td>11658 (HS-03)</td>
			<td>Two units, Heat sink without fan HS-03, Heat sink for 647 nm and 488 nm lasers</td>
		</tr>
		<tr>
			<td>Heat sink</td>
			<td>Coherent</td>
			<td>1193289</td>
			<td>Obis heat sink with fan, 165 x 50 x 50 mm for the 561 nm laser</td>
		</tr>
		<tr>
			<td>CAB-USB-miniUSB</td>
			<td>Cobolt</td>
			<td>10908</td>
			<td>Two units, communication cable for 647 nm and 488 nm lasers</td>
		</tr>
		<tr>
			<td>aluminum for height adjustment</td>
			<td>McMaster-Carr</td>
			<td>9146T35</td>
			<td>Multipurpose 6061 Aluminum, Rectangular Bar, 4MM X 40MM, 1&#39; Long for raising 561 nm laser</td>
		</tr>
		<tr>
			<td>aluminum for height adjustment</td>
			<td>McMaster-Carr</td>
			<td>8975K248</td>
			<td>Multipurpose 6061 Aluminum, 1-1/4&#34; Thick X 3&#34; Width X 1&#39; Length for raising 405 nm laser</td>
		</tr>
		<tr>
			<td>BNC cable</td>
			<td>L-com</td>
			<td>CC58C-6</td>
			<td>RG58C Coaxial Cable, BNC Male / Male, 6.0 ft</td>
		</tr>
		<tr>
			<td>BNC adapter</td>
			<td>L-com</td>
			<td>BA1087</td>
			<td>Coaxial Adapter, BNC Bulkhead, Grounded</td>
		</tr>
		<tr>
			<td>SMA to BNC Adapter</td>
			<td>HOD</td>
			<td>SMA-870</td>
			<td>Cobolt MLD lasers have SMA interface, so this adapter is used for BNC connection.</td>
		</tr>
		<tr>
			<td>SMB to BNC Adapter</td>
			<td>Fairview Microwave</td>
			<td>FMC1638316-12</td>
			<td>SMB Plug to BNC Female Bulkhead Cable RG316 Coax in 12 Inch for Coherent Obis lasers</td>
		</tr>
		<tr>
			<td>Data Acquisition Card</td>
			<td>National Instruments</td>
			<td>PCI-6723</td>
			<td>13-Bit, 32 Channels, 800 kS/s Analog Output Device for controlling lasers, DIC LED, and etc</td>
		</tr>
		<tr>
			<td>Barrier Filter Wheel controller</td>
			<td>Sutter Instrument</td>
			<td>Lambda 10-B</td>
			<td>Optical Filter Changer</td>
		</tr>
		<tr>
			<td>Emission Splitter</td>
			<td>Cairn</td>
			<td>OptoSplit III</td>
			<td></td>
		</tr>
		<tr>
			<td>Dichroic beamsplitter</td>
			<td>Chroma</td>
			<td>T640LPXR-UF2</td>
			<td>Dichroic beamsplitter separating red emission from green emission in OptoSplit III</td>
		</tr>
		<tr>
			<td>Dichroic beamsplitter</td>
			<td>Chroma</td>
			<td>T565LPXR-UF2</td>
			<td>Dichroic beamsplitter separating green &#38; red emission from blue emission in OptoSplit III</td>
		</tr>
		<tr>
			<td>Emission filter</td>
			<td>Chroma</td>
			<td>ET700/75M</td>
			<td>Two units, Emission filter for red emission (like Alexa Fluor 647) in OptoSplit III as well as in the Barrier filter wheel</td>
		</tr>
		<tr>
			<td>Emission filter</td>
			<td>Chroma</td>
			<td>ET595/50M</td>
			<td>Two units, Emission filter for yellow/green emission (like Cy3B) in OptoSplit III as well as in the Barrier filter wheel</td>
		</tr>
		<tr>
			<td>Emission filter</td>
			<td>Chroma</td>
			<td>ET525/50M</td>
			<td>Two units, Emission filter for blue emission(like Alexa Fluor 488/GFP) in OptoSplit III as well as in the Barrier filter wheel</td>
		</tr>
		<tr>
			<td>Emission filter</td>
			<td>Semrock</td>
			<td>FF02-447/60-25</td>
			<td>Emission filter for violet emission (like DAPI/Alexa Fluor 405), installed in the Barrier filter wheel</td>
		</tr>
		<tr>
			<td>Dichroic beamsplitter</td>
			<td>Chroma</td>
			<td>zt405/488/561/647/752rpc-UF3</td>
			<td>Multiband dichroic beam splitter for 647, 561, 488, and 405 nm laser excitations inside of the microscope body</td>
		</tr>
		<tr>
			<td>DAPI Filter set</td>
			<td>Chroma</td>
			<td>49000</td>
			<td>installed in the microscope body</td>
		</tr>
		<tr>
			<td>Nikon laser/TIRF filtercube</td>
			<td>Chroma</td>
			<td>91032</td>
			<td></td>
		</tr>
		<tr>
			<td>590 long pass filter</td>
			<td>Chroma</td>
			<td>T590LPXR-UF1</td>
			<td>for combining 647 nm laser and 561 nm laser</td>
		</tr>
		<tr>
			<td>525 long pass filter</td>
			<td>Chroma</td>
			<td>T525LPXR-UF1</td>
			<td>for combining already combined 647 nm and 561nm lasers with 488 nm laser</td>
		</tr>
		<tr>
			<td>470 long pass filter</td>
			<td>Chroma</td>
			<td>T470LPXR-UF1</td>
			<td>for combining already combined 647 nm, 561 nm and 488 nm lasers with 405 nm laser</td>
		</tr>
		<tr>
			<td>Laser clean-up filter (647)</td>
			<td>Chroma</td>
			<td>zet640/20x</td>
			<td>for cleaning up other wavelengths from the 647 nm laser</td>
		</tr>
		<tr>
			<td>Laser clean up filter (488)</td>
			<td>Semrock</td>
			<td>LL01-488-25</td>
			<td>for cleaning up other wavelengths from the 488 nm laser</td>
		</tr>
		<tr>
			<td>LED light source</td>
			<td>Excelitas</td>
			<td>X-Cite120LED</td>
			<td>used only for DAPI imaging</td>
		</tr>
		<tr>
			<td>Mirror mount</td>
			<td>Newport</td>
			<td>SU100-F3K</td>
			<td></td>
		</tr>
		<tr>
			<td>Optical posts</td>
			<td>Newport</td>
			<td>PS-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Clamping fork</td>
			<td>Newport</td>
			<td>PS-F</td>
			<td></td>
		</tr>
		<tr>
			<td>Power Meter</td>
			<td>Newport</td>
			<td>PMKIT</td>
			<td>For measuring laser power</td>
		</tr>
		<tr>
			<td>Dichroic beamcombiner mount</td>
			<td>Edmund Optics</td>
			<td>58-872</td>
			<td>C-Mount Kinematic Mount, for holding dichroic beamcombiners in the laser excitation assembly</td>
		</tr>
		<tr>
			<td>Retaining ring</td>
			<td>Thorlabs</td>
			<td>CMRR</td>
			<td>used for dichroic beamcombiner mounts</td>
		</tr>
		<tr>
			<td>Fiber Adapter Plate</td>
			<td>Thorlabs</td>
			<td>SM1FC</td>
			<td>FC/PC Fiber Adapter Plate with External SM1 (1.035&#34;-40) Thread</td>
		</tr>
		<tr>
			<td>Z-axis translational mount</td>
			<td>Thorlabs</td>
			<td>SM1Z</td>
			<td>Z-Axis Translation Mount, 30 mm Cage Compatible</td>
		</tr>
		<tr>
			<td>Achromatic Doublet lens</td>
			<td>Thorlabs</td>
			<td>AC050-008-A-ML</td>
			<td>&#216;5 mm, Mounted Achromatic Doublets, AR Coated: 400 - 700 nm</td>
		</tr>
		<tr>
			<td>Cage Plate</td>
			<td>Thorlabs</td>
			<td>CP1TM09</td>
			<td>30 mm Cage Plate with M9 x 0.5 Internal Threads, 8-32 Tap</td>
		</tr>
		<tr>
			<td>Cage Assembly Rod</td>
			<td>Thorlabs</td>
			<td>ER4</td>
			<td>Cage Assembly Rod, 4&#34; Long, &#216;6 mm</td>
		</tr>
		<tr>
			<td>Cage Mounting Bracket</td>
			<td>Thorlabs</td>
			<td>CP02B</td>
			<td>30 mm Cage Mounting Bracket</td>
		</tr>
		<tr>
			<td>Single mode optical fiber</td>
			<td>Thorlabs</td>
			<td>P5-405BPM-FC-2</td>
			<td>Patch Cable, PM, FC/PC to FC/APC, 405 nm, Panda, 2 m</td>
		</tr>
		<tr>
			<td>Multi mode optical fiber</td>
			<td>Thorlabs</td>
			<td>M42L01</td>
			<td>&#216;50 &#181;m, 0.22 NA, FC/PC-FC/PC Fiber Patch Cable, 1 m</td>
		</tr>
		<tr>
			<td>Achromatic Doublet lens (mag lens)</td>
			<td>Thorlabs</td>
			<td>ACN127-025-A</td>
			<td>ACN127-025-A - f=-25.0 mm, &#216;1/2&#34; Achromatic Doublet, ARC: 400-700 nm , a concave lens in the &#34;mag lens&#34;</td>
		</tr>
		<tr>
			<td>Achromatic Doublet lens (mag lens)</td>
			<td>Thorlabs</td>
			<td>AC127-050-A</td>
			<td>f=50.0 mm, &#216;1/2&#34; Achromatic Doublet, ARC: 400-700 nm, a convex lens in the &#34;mag lens&#34;</td>
		</tr>
		<tr>
			<td>Retaining ring</td>
			<td>Thorlabs</td>
			<td>SM05PRR</td>
			<td>SM05 Plastic Retaining Ring for &#216;1/2&#34; Lens Tubes and Mounts, for &#34;mag lens&#34;</td>
		</tr>
		<tr>
			<td>Nylon-tipped screw</td>
			<td>Thorlabs</td>
			<td>SS3MN6</td>
			<td>M3 x 0.5 Nylon-Tipped Setscrew, 6 mm Long, for holding &#34;3D lens&#34;</td>
		</tr>
		<tr>
			<td>3D lens</td>
			<td>CVI Laser Optics</td>
			<td>RCX-25.4-50.8-5000.0-C-415-700</td>
			<td>f=10 m, rectangular cylindrical lens</td>
		</tr>
		<tr>
			<td>EMCCD camera</td>
			<td>Andor</td>
			<td>iXon Ultra 888</td>
			<td></td>
		</tr>
		<tr>
			<td>100 nm multichannel beads</td>
			<td>Thermo</td>
			<td>T7279, TetraSpeck microspheres</td>
			<td></td>
		</tr>
		<tr>
			<td>red dye</td>
			<td>Thermo</td>
			<td>Alexa Fluor 647</td>
			<td></td>
		</tr>
		<tr>
			<td>yellow-green dye</td>
			<td>GE Healthcare</td>
			<td>Cy3</td>
			<td></td>
		</tr>
		<tr>
			<td>green dye</td>
			<td>GE Healthcare</td>
			<td>Cy3B</td>
			<td></td>
		</tr>
		<tr>
			<td>blue dye</td>
			<td>Thermo</td>
			<td>Alexa Fluor 488</td>
			<td></td>
		</tr>
	</tbody>
</table>

conducting multiple imaging modes with one fluorescence microscope

Fluorescence microscopy is a powerful tool to detect biological molecules in situ and monitor their dynamics and interactions in real-time. In addition to conventional epi-fluorescence microscopy, various imaging techniques have been developed to achieve specific experimental goals. Some of the widely used techniques include single-molecule fluorescence resonance energy transfer (smFRET), which can report conformational changes and molecular interactions with angstrom resolution, and single-molecule detection-based super-resolution (SR) imaging, which can enhance the spatial resolution approximately ten&#160;to twentyfold compared to diffraction-limited microscopy. Here we present a customer-designed integrated system, which merges multiple imaging methods in one microscope, including conventional epi-fluorescent imaging, single-molecule detection-based SR imaging, and multi-color single-molecule detection, including smFRET imaging. Different imaging methods can be achieved easily and reproducibly by switching optical elements. This set-up is easy to adopt by any research laboratory in biological sciences with a need for routine and diverse imaging experiments at a reduced cost and space relative to building separate microscopes for individual purposes.

This microscope allows flexible and reproducible switching between different imaging methods. Here we show sample images collected with each imaging module.
Figure 5D demonstrates the PSF of the blinking-on molecule during the SR acquisition. Thousands of such images are reconstructed to generate the final SR image (Figure 5E). Figure 5E sh...

Watch this Scientific Journal Video about Conducting Multiple Imaging Modes with One Fluorescence Microscope at JoVE.com

Conducting Multiple Imaging Modes with One Fluorescence Microscope

Here we present a practical guide of building an integrated microscopy system, which merges conventional epi-fluorescent imaging, single-molecule detection-based super-resolution imaging, and multi-color single-molecule detection, including single-molecule fluorescence resonance energy transfer imaging, into one set-up in a cost-efficient way.

Fluorescence microscopy is a powerful tool to detect biological molecules in situ and monitor their dynamics and interactions in real-time. In addition to ...

This method can help answer key questions in the optical microscopy field, such as how to take super-resolution images as well as FRET images using the same microscope. The main advantage of this technique is that we could combine three different imaging modules into one microscope, significantly reducing the overall cost. Visual demonstration of this method is critical as assembly of the excitation path is difficult to learn.They require proper choice of parts and a sensitive optical alignments. To begin, install a data acquisition card through a PCI interface and use it to connect the lasers to the computer. Control the lasers'on and off behaviors by transistor-transistor logic output and their power adjustment by the analog output of this card.Next, prepare a vibration-isolated optical table with mirrors and beam splitters as shown here and described in the accompanying text protocol. Combine the laser beams into a single-mode optical fiber by first mounting a fiber adaptor plate in a z-axis translation mount. Next, mount an achromatic doublet lens in a cage plate.Use an extension rod to connect the adapter and lens to form a cage. Then, use one-inch thick optical posts to mount the cage on the optical table. Align the 647-nanometer laser by adjusting the components to gain maximum laser power output through the fiber.Once the alignment of the first laser is done, temporarily install a pair of irises and align the rest of the lasers one by one. Check the alignment efficiency of each laser with a power meter. Be sure to leave one iris in front of the adapter plate to reduce the reflections of the lasers.Next, design and install the magnification lens as described in the accompanying text protocol. In order to create the astigmatism effect necessary for extracting the z-coordinates of every single molecule, place a 3D lens with a 10-meter focal length into the cassette and insert it into the emission beam path. To minimize the vibrations during sequential multicolor epifluorescence imaging, use emission filters placed in a barrier filter wheel connected next to the microscope.For simultaneous multicolor detection during single-molecule FRET experiments, place another filter set in an emission splitter. To set up for diffraction-limited imaging using epi-excitation, first adjust the excitation laser's incidental angle to epi mode in the illumination arm. Next, disengage the 3D lens, and insert the bypass cube into the emission splitter.Then, insert the mag lens for broadened illumination. Once set up, take multi-channel, z-stack, and/or time lapsed images of your sample based on your desired results. To set up multicolor single-molecule detection of surface-immobilized molecules, first move the filter wheel to an empty position.This will allow the lasers to pass through. Then, adjust the excitation lasers'incidental angle to the turf angle, and disengage both the mag and 3D lenses. Next, engage the three-channel mode in the emission splitter by first replacing the bypass cube with a calibration cube that allows all of the light to pass through all channels.Then, turn on the camera under DIC and adjust the aperture of the emission splitter until three, fully separated channels appear on the screen. Turn the vertical-horizontal adjustment control knobs on the emission splitter, and roughly align the three channels. Next, turn off the camera and replace the calibration cube with the triple cube.Place a sample of 100-nanometer multi-channel beads. Upon excitation at 488 nanometers, the 100-nanometer multi-channel beads emit different wavelengths of light, enabling three-channel alignment. Then, turn on the camera and the 488-nanometer laser, zoom in on one of the bright beads, and finally align the three channels by turning the adjustment control knobs again.With the sample now in place, using a weak laser, navigate to an area with a reasonable spot density and adjust the laser power and exposure time to achieve acceptable signal-to-noise and photobleaching levels. Then use the imaging software to take time-lapse images. For super-resolution imaging, begin by inserting the 3D lens and remove the mag lens.Then determine the optimal excitation laser's incidental angle to be the turf angle. In order to find the proper objective height for SR imaging, use DIC imaging to find the middle plane of the cells. Identify the plane by the height at which the cells become transparent.Once the desired focal plane is determined, begin super-resolution imaging. While imaging, change the 405-nanometer laser's power to maintain a reasonable density of blinking-on spots. Begin imaging without violet laser power.Count the number of blinking-on spots in a certain period and increase the violet laser power so that the number of blinking-on spots is kept above a user-defined counting threshold in the field of view. Analyze the data by detecting the centroids of each spot in the imaging frames and extract z-values for each spot from X and Y widths. Build a reconstructed image and visualize objects in 3D.This microscope setup allows for flexible and reproducible switching between different imaging methods, including conventional epifluorescent imaging, single-molecule detection-based super-resolution imaging, and multicolor single-molecule detection. In order to reveal finer details in the molecular assembly, super-resolution microscopy combines thousands of images such as this one. These images are then reconstructed to generate a final super-resolution image.Super-resolution techniques allow for high spatial resolution, providing details that can't be seen with other techniques. This is highlighted in the two images shown here. The super-resolution image shows the same bacterial regulatory RNase as the epifluorescence image but allows for single molecule detection.SmFRET is another method capable of angstrom to nanometer resolution. Here, folded RNA molecules were labeled with a green donor dye and a red acceptor dye. Fluorescence intensity trajectories can be extracted from individual single molecules, generating FRET efficiency as a function of time.Don't forget that working with lasers can be hazardous, and precautions such as wearing eye protection or lowering laser powers should always be taken where performing this procedure.

conducting-multiple-imaging-modes-with-one-fluorescence-microscope

Research

JoVE Journal

Bioengineering

Fluorescence Lifetime Imaging of Molecular Rotors in Living Cells

Diffusion is often an important rate-determining step in chemical reactions or biological processes and plays a role in a wide range of intracellular events. Viscosity is one of the key parameters affecting the diffusion of molecules and proteins, and changes in viscosity have been linked to disease and malfunction at the cellular level.1-3 While methods to measure the bulk viscosity are well developed, imaging microviscosity remains a challenge. Viscosity maps of microscopic objects, such as single cells, have until recently been hard to obtain. Mapping viscosity with fluorescence techniques is advantageous because, similar to other optical techniques, it is minimally invasive, non-destructive and can be applied to living cells and tissues.
Fluorescent molecular rotors exhibit fluorescence lifetimes and quantum yields which are a function of the viscosity of their microenvironment.4,5 Intramolecular twisting or rotation leads to non-radiative decay from the excited state back to the ground state. A viscous environment slows this rotation or twisting, restricting access to this non-radiative decay pathway. This leads to an increase in the fluorescence quantum yield and the fluorescence lifetime. Fluorescence Lifetime Imaging (FLIM) of modified hydrophobic BODIPY dyes that act as fluorescent molecular rotors show that the fluorescence lifetime of these probes is a function of the microviscosity of their environment.6-8 A logarithmic plot of the fluorescence lifetime versus the solvent viscosity yields a straight line that obeys the F&ouml;rster Hoffman equation.9 This plot also serves as a calibration graph to convert fluorescence lifetime into viscosity.
Following incubation of living cells with the modified BODIPY fluorescent molecular rotor, a punctate dye distribution is observed in the fluorescence images. The viscosity value obtained in the puncta in live cells is around 100 times higher than that of water and of cellular cytoplasm.6,7 Time-resolved fluorescence anisotropy measurements yield rotational correlation times in agreement with these large microviscosity values. Mapping the fluorescence lifetime is independent of the fluorescence intensity, and thus allows the separation of probe concentration and viscosity effects. 
In summary, we have developed a practical and versatile approach to map the microviscosity in cells based on FLIM of fluorescent molecular rotors.

Fluorescence Lifetime Imaging (FLIM) has emerged as a key technique to image the environment and interaction of specific proteins and dyes in living cells. FLIM of fluorescent molecular rotors allows mapping of viscosity in living cells.

Diffusion is often an important rate-determining step in chemical reactions or biological processes and plays a role in a wide range of intracellular ...

Optical Frequency Domain Imaging of Ex vivo Pulmonary Resection Specimens: Obtaining One to One Image to Histopathology Correlation

Lung cancer is the leading cause of cancer-related deaths1. Squamous cell and small cell cancers typically arise in association with the conducting airways, whereas adenocarcinomas are typically more peripheral in location. Lung malignancy detection early in the disease process may be difficult due to several limitations: radiological resolution, bronchoscopic limitations in evaluating tissue underlying the airway mucosa and identifying early pathologic changes, and small sample size and/or incomplete sampling in histology biopsies. High resolution imaging modalities, such as optical frequency domain imaging (OFDI), provide non-destructive, large area 3-dimensional views of tissue microstructure to depths approaching 2 mm in real time (Figure 1)2-6. OFDI has been utilized in a variety of applications, including evaluation of coronary artery atherosclerosis6,7 and esophageal intestinal metaplasia and dysplasia6,8-10.
Bronchoscopic OCT/OFDI has been demonstrated as a safe in vivo imaging tool for evaluating the pulmonary airways11-23 (Animation). OCT has been assessed in pulmonary airways16,23 and parenchyma17,22 of animal models and in vivo human airway14,15. OCT imaging of normal airway has demonstrated visualization of airway layering and alveolar attachments, and evaluation of dysplastic lesions has been found useful in distinguishing grades of dysplasia in the bronchial mucosa11,12,20,21. OFDI imaging of bronchial mucosa has been demonstrated in a short bronchial segment (0.8 cm)18. Additionally, volumetric OFDI spanning multiple airway generations in swine and human pulmonary airways in vivo has been described19. Endobronchial OCT/OFDI is typically performed using thin, flexible catheters, which are compatible with standard bronchoscopic access ports. Additionally, OCT and OFDI needle-based probes have recently been developed, which may be used to image regions of the lung beyond the airway wall or pleural surface17.
While OCT/OFDI has been utilized and demonstrated as feasible for in vivo pulmonary imaging, no studies with precisely matched one-to-one OFDI:histology have been performed. Therefore, specific imaging criteria for various pulmonary pathologies have yet to be developed. Histopathological counterparts obtained in vivo consist of only small biopsy fragments, which are difficult to correlate with large OFDI datasets. Additionally, they do not provide the comprehensive histology needed for registration with large volume OFDI. As a result, specific imaging features of pulmonary pathology cannot be developed in the in vivo setting. Precisely matched, one-to-one OFDI and histology correlation is vital to accurately evaluate features seen in OFDI against histology as a gold standard in order to derive specific image interpretation criteria for pulmonary neoplasms and other pulmonary pathologies. Once specific imaging criteria have been developed and validated ex vivo with matched one-to-one histology, the criteria may then be applied to in vivo imaging studies. Here, we present a method for precise, one to one correlation between high resolution optical imaging and histology in ex vivo lung resection specimens. Throughout this manuscript, we describe the techniques used to match OFDI images to histology. However, this method is not specific to OFDI and can be used to obtain histology-registered images for any optical imaging technique. We performed airway centered OFDI with a specialized custom built bronchoscopic 2.4 French (0.8 mm diameter) catheter. Tissue samples were marked with tissue dye, visible in both OFDI and histology. Careful orientation procedures were used to precisely correlate imaging and histological sampling locations. The techniques outlined in this manuscript were used to conduct the first demonstration of volumetric OFDI with precise correlation to tissue-based diagnosis for evaluating pulmonary pathology24. This straightforward, effective technique may be extended to other tissue types to provide precise imaging to histology correlation needed to determine fine imaging features of both normal and diseased tissues.

Optical Frequency Domain Imaging of Ex vivo Pulmonary Resection Specimens: Obtaining One to One Image to Histopathology Correlation

A method to image ex vivo pulmonary resection specimens with optical frequency domain imaging (OFDI) and obtain precise correlation to histology is described, which is essential to developing specific OFDI interpretation criteria for pulmonary pathology. This method is applicable to other tissue types and imaging techniques to obtain precise imaging to histology correlation for accurate image interpretation and assessment. Imaging criteria established with this technique would then be applicable to image assessment in future in vivo studies.

Lung cancer is the leading cause of cancer-related deaths1. Squamous cell and small cell cancers typically arise in association with the conducting ...

Time-lapse Fluorescence Imaging of Arabidopsis Root Growth with Rapid Manipulation of The Root Environment Using The RootChip

The root functions as the physical anchor of the plant and is the organ responsible for uptake of water and mineral nutrients such as nitrogen, phosphorus, sulfate and trace elements that plants acquire from the soil. If we want to develop sustainable approaches to producing high crop yield, we need to better understand how the root develops, takes up a wide spectrum of nutrients, and interacts with symbiotic and pathogenic organisms. To accomplish these goals, we need to be able to explore roots in microscopic detail over time periods ranging from minutes to days.
We developed the RootChip, a polydimethylsiloxane (PDMS)- based microfluidic device, which allows us to grow and image roots from Arabidopsis seedlings while avoiding any physical stress to roots during preparation for imaging1 (Figure 1). The device contains a bifurcated channel structure featuring micromechanical valves to guide the fluid flow from solution inlets to each of the eight observation chambers2. This perfusion system allows the root microenvironment to be controlled and modified with precision and speed. The volume of the chambers is approximately 400 nl, thus requiring only minimal amounts of test solution.
Here we provide a detailed protocol for studying root biology on the RootChip using imaging-based approaches with real time resolution. Roots can be analyzed over several days using time lapse microscopy. Roots can be perfused with nutrient solutions or inhibitors, and up to eight seedlings can be analyzed in parallel. This system has the potential for a wide range of applications, including analysis of root growth in the presence or absence of chemicals, fluorescence-based analysis of gene expression, and the analysis of biosensors, e.g. FRET nanosensors3.

This article provides a protocol for cultivation of Arabidopsis seedlings in the RootChip, a microfluidic imaging platform that combines automated control of growth conditions with microscopic root monitoring and FRET-based measurement of intracellular metabolite levels.

The root functions as the physical anchor of the plant and is the organ responsible for uptake of water and mineral nutrients such as nitrogen, ...

Creating Adhesive and Soluble Gradients for Imaging Cell Migration with Fluorescence Microscopy

Cells can sense and migrate towards higher concentrations of adhesive cues such as the glycoproteins of the extracellular matrix and soluble cues such as growth factors. Here, we outline a method to create opposing gradients of adhesive and soluble cues in a microfluidic chamber, which is compatible with live cell imaging. A copolymer of poly-L-lysine and polyethylene glycol (PLL-PEG) is employed to passivate glass coverslips and prevent non-specific adsorption of biomolecules and cells. Next, microcontact printing or dip pen lithography are used to create tracks of streptavidin on the passivated surfaces to serve as anchoring points for the biotinylated peptide arginine-glycine-aspartic acid (RGD) as the adhesive cue. A microfluidic device is placed onto the modified surface and used to create the gradient of adhesive cues (100% RGD to 0% RGD) on the streptavidin tracks. Finally, the same microfluidic device is used to create a gradient of a chemoattractant such as fetal bovine serum (FBS), as the soluble cue in the opposite direction of the gradient of adhesive cues.

A method for the assembly of adhesive and soluble gradients in a microscopy chamber for live cell migration studies is described. The engineered environment combines antifouling surfaces and adhesive tracks with solution gradients and therefore allows one to determine the relative importance of guidance cues.

Cells can sense and migrate towards higher concentrations of adhesive cues such as the glycoproteins of the extracellular matrix and soluble cues such as ...

One Minute, Sub-One-Watt Photothermal Tumor Ablation Using Porphysomes, Intrinsic Multifunctional Nanovesicles

We recently developed porphysomes as intrinsically multifunctional nanovesicles. A photosensitizer, pyropheophorbide &alpha;, was conjugated to a phospholipid and then self-assembled to liposome-like spherical vesicles. Due to the extremely high density of porphyrin in the porphyrin-lipid bilayer, porphysomes generated large extinction coefficients, structure-dependent fluorescence self-quenching, and excellent photothermal efficacy. In our formulation, porphysomes were synthesized using high pressure extrusion, and displayed a mean particle size around 120 nm. Twenty-four hr post-intravenous injection of porphysomes, the local temperature of the tumor increased from 30 &deg;C to 62 &deg;C rapidly upon one minute exposure of 750 mW (1.18 W/cm2), 671 nm laser irradiation. Following the complete thermal ablation of the tumor, eschars formed and healed within 2 weeks, while in the control groups the tumors continued to grow and all reached the defined end point within 3 weeks. These data show how porphysomes can be used as potent photothermal therapy (PTT) agents.

We developed novel intrinsic multifunctional nanovesicles called porphysomes, which have structure-dependent fluorescence self-quenching and unique photothermal properties, thus functioning as potent photothermal therapy agents. We formulated porphysomes using high pressure extrusion and investigated their photothermal therapy efficacy in a xenograft tumor model.

We recently developed porphysomes as intrinsically multifunctional nanovesicles. A photosensitizer, pyropheophorbide &alpha;, was conjugated to a ...

Quantitative Optical Microscopy: Measurement of Cellular Biophysical Features with a Standard Optical Microscope

We describe the use of a standard optical microscope to perform quantitative measurements of mass, volume, and density on cellular specimens through a combination of bright field and differential interference contrast imagery. Two primary approaches are presented: noninterferometric quantitative phase microscopy (NIQPM), to perform measurements of total cell mass and subcellular density distribution, and Hilbert transform differential interference contrast microscopy (HTDIC)&#160;to determine volume. NIQPM is based on a simplified model of wave propagation, termed the paraxial approximation, with three underlying assumptions: low numerical aperture (NA) illumination, weak scattering, and weak absorption of light by the specimen. Fortunately, unstained cellular specimens satisfy these assumptions and low NA illumination is easily achieved on commercial microscopes. HTDIC is used to obtain volumetric information from through-focus DIC imagery under high NA illumination conditions. High NA illumination enables enhanced sectioning of the specimen along the optical axis. Hilbert transform processing on the DIC image stacks greatly enhances edge detection algorithms for localization of the specimen borders in three dimensions by separating the gray values of the specimen intensity from those of the background. The primary advantages of NIQPM and HTDIC lay in their technological accessibility using &#8220;off-the-shelf&#8221; microscopes. There are two basic limitations of these methods: slow z-stack acquisition time on commercial scopes currently abrogates the investigation of phenomena faster than 1 frame/minute, and secondly, diffraction effects restrict the utility of NIQPM and HTDIC to objects from 0.2 up to 10 (NIQPM) and 20 (HTDIC) &#956;m in diameter, respectively. Hence, the specimen and its associated time dynamics of interest must meet certain size and temporal constraints to enable the use of these methods. Excitingly, most fixed cellular specimens are readily investigated with these methods.

We describe the use of a standard optical microscope to perform quantitative measurements of cellular mass, volume, and density through a combination of bright field and differential interference contrast imagery.

We describe the use of a standard optical microscope to perform quantitative measurements of mass, volume, and density on cellular specimens through a ...

High-resolution Spatiotemporal Analysis of Receptor Dynamics by Single-molecule Fluorescence Microscopy

Single-molecule microscopy is emerging as a powerful approach to analyze the behavior of signaling molecules, in particular concerning those aspect (e.g., kinetics, coexistence of different states and populations, transient interactions), which are typically hidden in ensemble measurements, such as those obtained with standard biochemical or microscopy methods. Thus, dynamic events, such as receptor-receptor interactions, can be followed in real time in a living cell with high spatiotemporal resolution. This protocol describes a method based on labeling with small and bright organic fluorophores and total internal reflection fluorescence (TIRF) microscopy to directly visualize single receptors on the surface of living cells. This approach allows one to precisely localize receptors, measure the size of receptor complexes, and capture dynamic events such as transient receptor-receptor interactions. The protocol provides a detailed description of how to perform a single-molecule experiment, including sample preparation, image acquisition and image analysis. As an example, the application of this method to analyze two G-protein-coupled receptors, i.e., &#946;2-adrenergic and &#947;-aminobutyric acid type B (GABAB) receptor, is reported. The protocol can be adapted to other membrane proteins and different cell models, transfection methods and labeling strategies.

This protocol describes how to use total internal reflection fluorescence microscopy to visualize and track single receptors on the surface of living cells and thereby analyze receptor lateral mobility, size of receptor complexes as well as to visualize transient receptor-receptor interactions. This protocol can be extended to other membrane proteins.

Single-molecule microscopy is emerging as a powerful approach to analyze the behavior of signaling molecules, in particular concerning those aspect (e.g., ...

3D Orbital Tracking in a Modified Two-photon Microscope: An Application to the Tracking of Intracellular Vesicles

The objective of this video protocol is to discuss how to perform and analyze a three-dimensional fluorescent orbital particle tracking experiment using a modified two-photon microscope1. As opposed to conventional approaches (raster scan or wide field based on a stack of frames), the 3D orbital tracking allows to localize and follow with a high spatial (10 nm accuracy) and temporal resolution (50 Hz frequency response) the 3D displacement of a moving fluorescent particle on length-scales of hundreds of microns2. The method is based on a feedback algorithm that controls the hardware of a two-photon laser scanning microscope in order to perform a circular orbit around the object to be tracked: the feedback mechanism will maintain the fluorescent object in the center by controlling the displacement of the scanning beam3-5. To demonstrate the advantages of this technique, we followed a fast moving organelle, the lysosome, within a living cell6,7. Cells were plated according to standard protocols, and stained using a commercially lysosome dye. We discuss briefly the hardware configuration and in more detail the control software, to perform a 3D orbital tracking experiment inside living cells. We discuss in detail the parameters required in order to control the scanning microscope and enable the motion of the beam in a closed orbit around the particle. We conclude by demonstrating how this method can be effectively used to track the fast motion of a labeled lysosome along microtubules in 3D within a live cell. Lysosomes can move with speeds in the range of 0.4-0.5 &#181;m/sec, typically displaying a directed motion along the microtubule network8.

In this video protocol we track - at high speed and in three dimensions - fluorescently labeled lysosomes within living cells, using the orbital tracking method in a modified two-photon microscope.

The objective of this video protocol is to discuss how to perform and analyze a three-dimensional fluorescent orbital particle tracking experiment using a ...

From Fast Fluorescence Imaging to Molecular Diffusion Law on Live Cell Membranes in a Commercial Microscope

It has become increasingly evident that the spatial distribution and the motion of membrane components like lipids and proteins are key factors in the regulation of many cellular functions. However, due to the fast dynamics and the tiny structures involved, a very high spatio-temporal resolution is required to catch the real behavior of molecules. Here we present the experimental protocol for studying the dynamics of fluorescently-labeled plasma-membrane proteins and lipids in live cells with high spatiotemporal resolution. Notably, this approach doesn&#8217;t need to track each molecule, but it calculates population behavior using all molecules in a given region of the membrane. The starting point is a fast imaging of a given region on the membrane. Afterwards, a complete spatio-temporal autocorrelation function is calculated correlating acquired images at increasing time delays, for example each 2, 3, n repetitions. It is possible to demonstrate that the width of the peak of the spatial autocorrelation function increases at increasing time delay as a function of particle movement due to diffusion. Therefore, fitting of the series of autocorrelation functions enables to extract the actual protein mean square displacement from imaging (iMSD), here presented in the form of apparent diffusivity vs average displacement. This yields a quantitative view of the average dynamics of single molecules with nanometer accuracy. By using a GFP-tagged variant of the Transferrin Receptor (TfR) and an ATTO488 labeled 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphoethanolamine (PPE) it is possible to observe the spatiotemporal regulation of protein and lipid diffusion on &#181;m-sized membrane regions in the micro-to-milli-second time range.

Spatial distribution and temporal dynamics of plasma membrane proteins and lipids is a hot topic in biology. Here this issue is addressed by a spatio-temporal image fluctuation analysis that provides conceptually the same physical quantities of single particle tracking, but it uses small molecular labels and standard microscopy setups.

It has become increasingly evident that the spatial distribution and the motion of membrane components like lipids and proteins are key factors in the ...

A Guide to Structured Illumination TIRF Microscopy at High Speed with Multiple Colors

Optical super-resolution imaging with structured illumination microscopy (SIM) is a key technology for the visualization of processes at the molecular level in the chemical and biomedical sciences. Although commercial SIM systems are available, systems that are custom designed in the laboratory can outperform commercial systems, the latter typically designed for ease of use and general purpose applications, both in terms of imaging fidelity and speed. This article presents an in-depth guide to building a SIM system that uses total internal reflection (TIR) illumination and is capable of imaging at up to 10 Hz in three colors at a resolution reaching 100 nm. Due to the combination of SIM and TIRF, the system provides better image contrast than rival technologies. To achieve these specifications, several optical elements are used to enable automated control over the polarization state and spatial structure of the illumination light for all available excitation wavelengths. Full details on hardware implementation and control are given to achieve synchronization between excitation light pattern generation, wavelength, polarization state, and camera control with an emphasis on achieving maximum acquisition frame rate. A step-by-step protocol for system alignment and calibration is presented and the achievable resolution improvement is validated on ideal test samples. The capability for video-rate super-resolution imaging is demonstrated with living cells.

This article provides an in depth guide for the assembly and operation of a structured illumination microscope operating with total internal reflection fluorescence illumination (TIRF-SIM) to image dynamic biological processes with optical super-resolution in multiple colors.

Optical super-resolution imaging with structured illumination microscopy (SIM) is a key technology for the visualization of processes at the molecular ...