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Schneider F, Hernandez-Varas P, Christoffer Lagerholm B, Shrestha D, Sezgin E, Julia Roberti M, Ossato G, Hecht F, Eggeling C, Urbančič I. High photon count rates improve the quality of super-resolution fluorescence fluctuation spectroscopy. JOURNAL OF PHYSICS D: APPLIED PHYSICS 2020; 53:164003. [PMID: 33191951 PMCID: PMC7655148 DOI: 10.1088/1361-6463/ab6cca] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 12/19/2019] [Accepted: 01/16/2020] [Indexed: 05/15/2023]
Abstract
Probing the diffusion of molecules has become a routine measurement across the life sciences, chemistry and physics. It provides valuable insights into reaction dynamics, oligomerisation, molecular (re-)organisation or cellular heterogeneities. Fluorescence correlation spectroscopy (FCS) is one of the widely applied techniques to determine diffusion dynamics in two and three dimensions. This technique relies on the temporal autocorrelation of intensity fluctuations but recording these fluctuations has thus far been limited by the detection electronics, which could not efficiently and accurately time-tag photons at high count rates. This has until now restricted the range of measurable dye concentrations, as well as the data quality of the FCS recordings, especially in combination with super-resolution stimulated emission depletion (STED) nanoscopy. Here, we investigate the applicability and reliability of (STED-)FCS at high photon count rates (average intensities of more than 1 MHz) using novel detection equipment, namely hybrid detectors and real-time gigahertz sampling of the photon streams implemented on a commercial microscope. By measuring the diffusion of fluorophores in solution and cytoplasm of live cells, as well as in model and cellular membranes, we show that accurate diffusion and concentration measurements are possible in these previously inaccessible high photon count regimes. Specifically, it offers much greater flexibility of experiments with biological samples with highly variable intensity, e.g. due to a wide range of expression levels of fluorescent proteins. In this context, we highlight the independence of diffusion properties of cytosolic GFP in a concentration range of approx. 0.01-1 µm. We further show that higher photon count rates also allow for much shorter acquisition times, and improved data quality. Finally, this approach also pronouncedly increases the robustness of challenging live cell STED-FCS measurements of nanoscale diffusion dynamics, which we testify by confirming a free diffusion pattern for a fluorescent lipid analogue on the apical membrane of adherent cells.
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Affiliation(s)
- Falk Schneider
- MRC Human Immunology Unit and MRC Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford, OX3 9DS, United Kingdom
| | - Pablo Hernandez-Varas
- Wolfson Imaging Centre Oxford, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford, OX3 9DS, United Kingdom
- Core Facility for Integrated Microscopy, Panum Institute, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - B Christoffer Lagerholm
- Wolfson Imaging Centre Oxford, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford, OX3 9DS, United Kingdom
| | - Dilip Shrestha
- MRC Human Immunology Unit and MRC Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford, OX3 9DS, United Kingdom
| | - Erdinc Sezgin
- MRC Human Immunology Unit and MRC Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford, OX3 9DS, United Kingdom
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden
| | - M Julia Roberti
- Leica Microsystems CMS GmbH, Am Friedensplatz 3, 68163 Mannheim, Germany
| | - Giulia Ossato
- Leica Microsystems CMS GmbH, Am Friedensplatz 3, 68163 Mannheim, Germany
| | - Frank Hecht
- Leica Microsystems CMS GmbH, Am Friedensplatz 3, 68163 Mannheim, Germany
| | - Christian Eggeling
- MRC Human Immunology Unit and MRC Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford, OX3 9DS, United Kingdom
- Wolfson Imaging Centre Oxford, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford, OX3 9DS, United Kingdom
- Institute of Applied Optics and Biophysics, Friedrich-Schiller-University Jena, Max-Wien Platz 4, 07743 Jena, Germany
- Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Straße 9, 07745 Jena, Germany
| | - Iztok Urbančič
- MRC Human Immunology Unit and MRC Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford, OX3 9DS, United Kingdom
- Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana, Slovenia
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Chojnacki J, Eggeling C. Super-resolution fluorescence microscopy studies of human immunodeficiency virus. Retrovirology 2018; 15:41. [PMID: 29884197 PMCID: PMC5994058 DOI: 10.1186/s12977-018-0424-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 05/28/2018] [Indexed: 11/10/2022] Open
Abstract
Super-resolution fluorescence microscopy combines the ability to observe biological processes beyond the diffraction limit of conventional light microscopy with all advantages of the fluorescence readout such as labelling specificity and non-invasive live-cell imaging. Due to their subdiffraction size (< 200 nm) viruses are ideal candidates for super-resolution microscopy studies, and Human Immunodeficiency Virus type 1 (HIV-1) is to date the most studied virus by this technique. This review outlines principles of different super-resolution techniques as well as their advantages and disadvantages for virological studies, especially in the context of live-cell imaging applications. We highlight the findings of super-resolution based HIV-1 studies performed so far, their contributions to the understanding of HIV-1 replication cycle and how the current advances in super-resolution microscopy may open new avenues for future virology research.
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Affiliation(s)
- Jakub Chojnacki
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS, UK.
| | - Christian Eggeling
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS, UK
- Institute of Applied Optics, Friedrich-Schiller-University Jena, Max-Wien Platz 4, 07743, Jena, Germany
- Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Straße 9, 07745, Jena, Germany
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Kim N, Kwon J, Lim Y, Kang J, Bae S, Kim SK. Incorporation of STED technique into single-molecule spectroscopy to break the concentration limit of diffusing molecules in single-molecule detection. Chem Commun (Camb) 2018; 54:9667-9670. [DOI: 10.1039/c8cc05726e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Incorporation of STED into ALEX-FRET increases the concentration limit of single-molecule detection by 100-fold to 5 nM.
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Affiliation(s)
- Namdoo Kim
- Department of Chemistry
- Seoul National University
- Seoul 08826
- Korea
| | - Jiwoong Kwon
- Department of Biophysics and Chemical Biology
- Seoul National University
- Seoul 08826
- Korea
| | - Youngbin Lim
- Department of Biophysics and Chemical Biology
- Seoul National University
- Seoul 08826
- Korea
| | - Jooyoun Kang
- Department of Chemistry
- Seoul National University
- Seoul 08826
- Korea
| | - Sohyeon Bae
- Department of Chemistry
- Seoul National University
- Seoul 08826
- Korea
| | - Seong Keun Kim
- Department of Chemistry
- Seoul National University
- Seoul 08826
- Korea
- Department of Biophysics and Chemical Biology
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Li J, Dong C, Ren J. Strategies to reduce detection volume of fluorescence correlation spectroscopy (FCS) to realize physiological concentration measurements. Trends Analyt Chem 2017. [DOI: 10.1016/j.trac.2017.02.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Jazi AA, Ploetz E, Arizki M, Dhandayuthapani B, Waclawska I, Krämer R, Ziegler C, Cordes T. Caging and Photoactivation in Single-Molecule Förster Resonance Energy Transfer Experiments. Biochemistry 2017; 56:2031-2041. [PMID: 28362086 PMCID: PMC5390306 DOI: 10.1021/acs.biochem.6b00916] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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Caged
organic fluorophores are established tools for localization-based
super-resolution imaging. Their use relies on reversible deactivation
of standard organic fluorophores by chemical reduction or commercially
available caged dyes with ON switching of the fluorescent signal by
ultraviolet (UV) light. Here, we establish caging of cyanine fluorophores
and caged rhodamine dyes, i.e., chemical deactivation of fluorescence,
for single-molecule Förster resonance energy transfer (smFRET)
experiments with freely diffusing molecules. They allow temporal separation
and sorting of multiple intramolecular donor–acceptor pairs
during solution-based smFRET. We use this “caged FRET”
methodology for the study of complex biochemical species such as multisubunit
proteins or nucleic acids containing more than two fluorescent labels.
Proof-of-principle experiments and a characterization of the uncaging
process in the confocal volume are presented. These reveal that chemical
caging and UV reactivation allow temporal uncoupling of convoluted
fluorescence signals from, e.g., multiple spectrally similar donor
or acceptor molecules on nucleic acids. We also use caging without
UV reactivation to remove unwanted overlabeled species in experiments
with the homotrimeric membrane transporter BetP. We finally outline
further possible applications of the caged FRET methodology, such
as the study of weak biochemical interactions, which are otherwise
impossible with diffusion-based smFRET techniques because of the required
low concentrations of fluorescently labeled biomolecules.
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Affiliation(s)
- Atieh Aminian Jazi
- Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.,Institute of Biophysics and Biophysical Chemistry, Universität Regensburg , 95053 Regensburg, Germany
| | - Evelyn Ploetz
- Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Muhamad Arizki
- Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | | | - Izabela Waclawska
- Institute of Biophysics and Biophysical Chemistry, Universität Regensburg , 95053 Regensburg, Germany
| | - Reinhard Krämer
- Institute for Biochemistry, Universität Köln , 50674 Köln, Germany
| | - Christine Ziegler
- Institute of Biophysics and Biophysical Chemistry, Universität Regensburg , 95053 Regensburg, Germany
| | - Thorben Cordes
- Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands
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Abstract
The majority of studies of the living cell rely on capturing images using fluorescence microscopy. Unfortunately, for centuries, diffraction of light was limiting the spatial resolution in the optical microscope: structural and molecular details much finer than about half the wavelength of visible light (~200 nm) could not be visualized, imposing significant limitations on this otherwise so promising method. The surpassing of this resolution limit in far-field microscopy is currently one of the most momentous developments for studying the living cell, as the move from microscopy to super-resolution microscopy or 'nanoscopy' offers opportunities to study problems in biophysical and biomedical research at a new level of detail. This review describes the principles and modalities of present fluorescence nanoscopes, as well as their potential for biophysical and cellular experiments. All the existing nanoscopy variants separate neighboring features by transiently preparing their fluorescent molecules in states of different emission characteristics in order to make the features discernible. Usually these are fluorescent 'on' and 'off' states causing the adjacent molecules to emit sequentially in time. Each of the variants can in principle reach molecular spatial resolution and has its own advantages and disadvantages. Some require specific transitions and states that can be found only in certain fluorophore subfamilies, such as photoswitchable fluorophores, while other variants can be realized with standard fluorescent labels. Similar to conventional far-field microscopy, nanoscopy can be utilized for dynamical, multi-color and three-dimensional imaging of fixed and live cells, tissues or organisms. Lens-based fluorescence nanoscopy is poised for a high impact on future developments in the life sciences, with the potential to help solve long-standing quests in different areas of scientific research.
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Abstract
The local structure and composition of the outer membrane of an animal cell are important factors in the control of many membrane processes and mechanisms. These include signaling, sorting, and exo- and endocytic processes that are occurring all the time in a living cell. Paradoxically, not only are the local structure and composition of the membrane matters of much debate and discussion, the mechanisms that govern its genesis remain highly controversial. Here, we discuss a swathe of new technological advances that may be applied to understand the local structure and composition of the membrane of a living cell from the molecular scale to the scale of the whole membrane.
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Affiliation(s)
- Thomas S van Zanten
- National Centre for Biological Sciences (TIFR), Bellary Road, Bangalore, 560065, India
| | - Satyajit Mayor
- National Centre for Biological Sciences (TIFR), Bellary Road, Bangalore, 560065, India
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Stiel AC, Deán-Ben XL, Jiang Y, Ntziachristos V, Razansky D, Westmeyer GG. High-contrast imaging of reversibly switchable fluorescent proteins via temporally unmixed multispectral optoacoustic tomography. OPTICS LETTERS 2015; 40:367-370. [PMID: 25680049 DOI: 10.1364/ol.40.000367] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Photocontrol of reversibly switchable fluorescent proteins (RSFPs) was used to program optoacoustic signal time courses that were temporally unmixed to increase the proteins' contrast-to-noise-ratios (CNRs) in optoacoustic imaging. In this way, two variants of the RSFP Dronpa with very similar optoacoustic spectra could be readily discriminated in the presence of highly absorbing blood. Addition of temporal unmixing to multispectral optoacoustic tomography (tuMSOT) in conjunction with synthetic or genetically encoded photochromic contrast agents and customized photoswitching schedules can increase the performance of multiplexed and high-contrast molecular optoacoustic imaging.
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Mivelle M, Van Zanten TS, Manzo C, Garcia-Parajo MF. Nanophotonic approaches for nanoscale imaging and single-molecule detection at ultrahigh concentrations. Microsc Res Tech 2014; 77:537-45. [DOI: 10.1002/jemt.22369] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 01/28/2014] [Accepted: 03/27/2014] [Indexed: 12/22/2022]
Affiliation(s)
- Mathieu Mivelle
- ICFO-Institut de Ciencies Fotoniques; Mediterranean Technology Park; Castelldefels 08860 Barcelona Spain
| | - Thomas. S. Van Zanten
- ICFO-Institut de Ciencies Fotoniques; Mediterranean Technology Park; Castelldefels 08860 Barcelona Spain
| | - Carlo Manzo
- ICFO-Institut de Ciencies Fotoniques; Mediterranean Technology Park; Castelldefels 08860 Barcelona Spain
| | - Maria F. Garcia-Parajo
- ICFO-Institut de Ciencies Fotoniques; Mediterranean Technology Park; Castelldefels 08860 Barcelona Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats; 08010 Barcelona Spain
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Grotjohann T, Testa I, Reuss M, Brakemann T, Eggeling C, Hell SW, Jakobs S. rsEGFP2 enables fast RESOLFT nanoscopy of living cells. eLife 2012; 1:e00248. [PMID: 23330067 PMCID: PMC3534202 DOI: 10.7554/elife.00248] [Citation(s) in RCA: 153] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 11/19/2012] [Indexed: 12/18/2022] Open
Abstract
The super-resolution microscopy called RESOLFT relying on fluorophore switching between longlived states, stands out by its coordinate-targeted sequential sample interrogation using low light levels. While RESOLFT has been shown to discern nanostructures in living cells, the reversibly photoswitchable green fluorescent protein (rsEGFP) employed in these experiments was switched rather slowly and recording lasted tens of minutes. We now report on the generation of rsEGFP2 providing faster switching and the use of this protein to demonstrate 25–250 times faster recordings. DOI:http://dx.doi.org/10.7554/eLife.00248.001 For decades it was assumed that the diffraction of light meant that optical microscopy could not resolve features that were smaller than about the half the wavelength of the light being used to create an image. However, various ‘super-resolution’ methods have allowed researchers to overcome this diffraction limit for fluorescence imaging, which is the most popular form of microscopy used in the life sciences. This approach involves tagging the biomolecules of interest with fluorescent molecules, such as green fluorescent protein (GFP), so that they can be identified in cells. An excitation laser then drives the fluorescent molecule, which is also known as a fluorophore, into an excited state: after a short time, the fluorophore can return to its ground state by releasing a fluorescence photon. Images of the sample are built up by detecting these photons. In STED super-resolution microscopy a second laser is used to instantly send the molecules from their excited or ‘on’ states back to their ground or ‘off’ states before any fluorescence can occur. The second laser beam is usually shaped like a doughnut, with a small region of low light intensity surrounded by a region of much higher intensity. STED microscopy is able to beat the diffraction limit because the second laser turns all the fluorophores ‘off’ except those in the small sub-wavelength region at the centre of the doughnut. The image is build up by scanning both lasers over the sample so that the small region in which the fluorophores are ‘on’ probes the entire cell. RESOLFT is a similar technique that employs fluorescent molecules with ‘on’ and ‘off’ times that are much longer than those used in STED microscopy. In particular, RESOLFT uses fluorescent molecules that can be rapidly switched back and forth between long-lived ‘on’ and ‘off’ states many times by the two lasers. The fact that both these states are long-lived states means that RESOLFT requires much lower laser intensities than STED, which makes it attractive for imaging biological samples over large areas or long times. RESOLFT demonstrated its suitability for bioimaging for the first time last year, with a protein called rsEGFP (reversibly switchable enhanced GFP) being employed as the fluorophore. However, the time needed to switch this protein between the ‘on state’ and the ‘off state’ was relatively long, and it took about an hour to record a typical image. Now, Grotjohann et al. have modified this protein to make a new fluorophore called rsEGFP2 with a shorter switching time, and have used it to image various structures—including Vimentin, a protein that forms part of the cytoskeleton in many cells, and organelles called peroxisomes—inside live mammalian cells. They were able to record these images some 25–250 times faster than would have been possible with previous RESOLFT approaches. The combination of RESOLFT and rsEGFP2 should allow researchers to image a wide variety of structures and processes in living cells that have not been imaged before. DOI:http://dx.doi.org/10.7554/eLife.00248.002
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Affiliation(s)
- Tim Grotjohann
- Department of NanoBiophotonics , Max Planck Institute for Biophysical Chemistry , Göttingen , Germany
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Fast molecular tracking maps nanoscale dynamics of plasma membrane lipids. Proc Natl Acad Sci U S A 2010; 107:6829-34. [PMID: 20351247 DOI: 10.1073/pnas.0912894107] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We describe an optical method capable of tracking a single fluorescent molecule with a flexible choice of high spatial accuracy (approximately 10-20 nm standard deviation or approximately 20-40 nm full-width-at-half-maximum) and temporal resolution (< 1 ms). The fluorescence signal during individual passages of fluorescent molecules through a spot of excitation light allows the sequential localization and thus spatio-temporal tracking of the molecule if its fluorescence is collected on at least three separate point detectors arranged in close proximity. We show two-dimensional trajectories of individual, small organic dye labeled lipids diffusing in the plasma membrane of living cells and directly observe transient events of trapping on < 20 nm spatial scales. The trapping is cholesterol-assisted and much more pronounced for a sphingo- than for a phosphoglycero-lipid, with average trapping times of approximately 15 ms and < 4 ms, respectively. The results support previous STED nanoscopy measurements and suggest that, at least for nontreated cells, the transient interaction of a single lipid is confined to macromolecular dimensions. Our experimental approach demonstrates that fast molecular movements can be tracked with minimal invasion, which can reveal new important details of cellular nano-organization.
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Stiel AC, Andresen M, Bock H, Hilbert M, Schilde J, Schönle A, Eggeling C, Egner A, Hell SW, Jakobs S. Generation of monomeric reversibly switchable red fluorescent proteins for far-field fluorescence nanoscopy. Biophys J 2008; 95:2989-97. [PMID: 18658221 PMCID: PMC2527278 DOI: 10.1529/biophysj.108.130146] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Accepted: 05/22/2008] [Indexed: 11/18/2022] Open
Abstract
Reversibly switchable fluorescent proteins (RSFPs) are GFP-like proteins that may be repeatedly switched by irradiation with light from a fluorescent to a nonfluorescent state, and vice versa. They can be utilized as genetically encodable probes and bear large potential for a wide array of applications, in particular for new protein tracking schemes and subdiffraction resolution microscopy. However, the currently described monomeric RSFPs emit only blue-green or green fluorescence; the spectral window for their use is thus rather limited. Using a semirational engineering approach based on the crystal structure of the monomeric nonswitchable red fluorescent protein mCherry, we generated rsCherry and rsCherryRev. These two novel red fluorescent RSFPs exhibit fluorescence emission maxima at approximately 610 nm. They display antagonistic switching modes, i.e., in rsCherry irradiation with yellow light induces the off-to-on transition and blue light the on-to-off transition, whereas in rsCherryRev the effects of the switching wavelengths are reversed. We demonstrate time-lapse live-cell subdiffraction microscopy by imaging rsCherryRev targeted to the endoplasmic reticulum utilizing the switching and localization of single molecules.
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Affiliation(s)
- Andre C Stiel
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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