1
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Perego E, Zappone S, Castagnetti F, Mariani D, Vitiello E, Rupert J, Zacco E, Tartaglia GG, Bozzoni I, Slenders E, Vicidomini G. Single-photon microscopy to study biomolecular condensates. Nat Commun 2023; 14:8224. [PMID: 38086853 PMCID: PMC10716487 DOI: 10.1038/s41467-023-43969-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 11/24/2023] [Indexed: 12/18/2023] Open
Abstract
Biomolecular condensates serve as membrane-less compartments within cells, concentrating proteins and nucleic acids to facilitate precise spatial and temporal orchestration of various biological processes. The diversity of these processes and the substantial variability in condensate characteristics present a formidable challenge for quantifying their molecular dynamics, surpassing the capabilities of conventional microscopy. Here, we show that our single-photon microscope provides a comprehensive live-cell spectroscopy and imaging framework for investigating biomolecular condensation. Leveraging a single-photon detector array, single-photon microscopy enhances the potential of quantitative confocal microscopy by providing access to fluorescence signals at the single-photon level. Our platform incorporates photon spatiotemporal tagging, which allowed us to perform time-lapse super-resolved imaging for molecular sub-diffraction environment organization with simultaneous monitoring of molecular mobility, interactions, and nano-environment properties through fluorescence lifetime fluctuation spectroscopy. This integrated correlative study reveals the dynamics and interactions of RNA-binding proteins involved in forming stress granules, a specific type of biomolecular condensates, across a wide range of spatial and temporal scales. Our versatile framework opens up avenues for exploring a broad spectrum of biomolecular processes beyond the formation of membrane-less organelles.
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Affiliation(s)
- Eleonora Perego
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Sabrina Zappone
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
- Dipartimento di Informatica, Bioingegneria, Robotica e Ingegneria dei Sistemi, University of Genoa, Genoa, Italy
| | - Francesco Castagnetti
- Non coding RNAs in Physiology and Pathology, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Davide Mariani
- Non coding RNAs in Physiology and Pathology, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Erika Vitiello
- Non coding RNAs in Physiology and Pathology, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Jakob Rupert
- RNA Systems Biology, Istituto Italiano di Tecnologia, Genoa, Italy
- Department of Biology and Biotechnologies 'C. Darwin', Sapienza University of Rome, Rome, Italy
| | - Elsa Zacco
- RNA Systems Biology, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Gian Gaetano Tartaglia
- RNA Systems Biology, Istituto Italiano di Tecnologia, Genoa, Italy
- Department of Biology and Biotechnologies 'C. Darwin', Sapienza University of Rome, Rome, Italy
| | - Irene Bozzoni
- Non coding RNAs in Physiology and Pathology, Istituto Italiano di Tecnologia, Genoa, Italy
- Department of Biology and Biotechnologies 'C. Darwin', Sapienza University of Rome, Rome, Italy
| | - Eli Slenders
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Giuseppe Vicidomini
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy.
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2
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Yuan G, Gao H, Yang T. Exploring the Role of the Plant Actin Cytoskeleton: From Signaling to Cellular Functions. Int J Mol Sci 2023; 24:15480. [PMID: 37895158 PMCID: PMC10607326 DOI: 10.3390/ijms242015480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 10/06/2023] [Accepted: 10/21/2023] [Indexed: 10/29/2023] Open
Abstract
The plant actin cytoskeleton is characterized by the basic properties of dynamic array, which plays a central role in numerous conserved processes that are required for diverse cellular functions. Here, we focus on how actins and actin-related proteins (ARPs), which represent two classical branches of a greatly diverse superfamily of ATPases, are involved in fundamental functions underlying signal regulation of plant growth and development. Moreover, we review the structure, assembly dynamics, and biological functions of filamentous actin (F-actin) from a molecular perspective. The various accessory proteins known as actin-binding proteins (ABPs) partner with F-actin to finely tune actin dynamics, often in response to various cell signaling pathways. Our understanding of the significance of the actin cytoskeleton in vital cellular activities has been furthered by comparison of conserved functions of actin filaments across different species combined with advanced microscopic techniques and experimental methods. We discuss the current model of the plant actin cytoskeleton, followed by examples of the signaling mechanisms under the supervision of F-actin related to cell morphogenesis, polar growth, and cytoplasmic streaming. Determination of the theoretical basis of how the cytoskeleton works is important in itself and is beneficial to future applications aimed at improving crop biomass and production efficiency.
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Affiliation(s)
| | | | - Tao Yang
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China; (G.Y.); (H.G.)
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3
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SPLIT-PIN software enabling confocal and super-resolution imaging with a virtually closed pinhole. Sci Rep 2023; 13:2741. [PMID: 36792719 PMCID: PMC9931717 DOI: 10.1038/s41598-023-29951-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Accepted: 02/13/2023] [Indexed: 02/17/2023] Open
Abstract
In point-scanning microscopy, optical sectioning is achieved using a small aperture placed in front of the detector, i.e. the detection pinhole, which rejects the out-of-focus background. The maximum level of optical sectioning is theoretically obtained for the minimum size of the pinhole aperture, but this is normally prevented by the dramatic reduction of the detected signal when the pinhole is closed, leading to a compromise between axial resolution and signal-to-noise ratio. We have recently demonstrated that, instead of closing the pinhole, one can reach a similar level of optical sectioning by tuning the pinhole size in a confocal microscope and by analyzing the resulting image series. The method, consisting in the application of the separation of photons by lifetime tuning (SPLIT) algorithm to series of images acquired with tunable pinhole size, is called SPLIT-pinhole (SPLIT-PIN). Here, we share and describe a SPLIT-PIN software for the processing of series of images acquired at tunable pinhole size, which generates images with reduced out-of-focus background. The software can be used on series of at least two images acquired on available commercial microscopes equipped with a tunable pinhole, including confocal and stimulated emission depletion (STED) microscopes. We demonstrate applicability on different types of imaging modalities: (1) confocal imaging of DNA in a non-adherent cell line; (2) removal of out-of-focus background in super-resolved STED microscopy; (3) imaging of live intestinal organoids stained with a membrane dye.
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4
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Focus image scanning microscopy for sharp and gentle super-resolved microscopy. Nat Commun 2022; 13:7723. [PMID: 36513680 PMCID: PMC9747786 DOI: 10.1038/s41467-022-35333-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 11/28/2022] [Indexed: 12/15/2022] Open
Abstract
To date, the feasibility of super-resolution microscopy for imaging live and thick samples is still limited. Stimulated emission depletion (STED) microscopy requires high-intensity illumination to achieve sub-diffraction resolution, potentially introducing photodamage to live specimens. Moreover, the out-of-focus background may degrade the signal stemming from the focal plane. Here, we propose a new method to mitigate these limitations without drawbacks. First, we enhance a STED microscope with a detector array, enabling image scanning microscopy (ISM). Therefore, we implement STED-ISM, a method that exploits the working principle of ISM to reduce the depletion intensity and achieve a target resolution. Later, we develop Focus-ISM, a strategy to improve the optical sectioning and remove the background of any ISM-based imaging technique, with or without a STED beam. The proposed approach requires minimal architectural changes to a conventional microscope but provides substantial advantages for live and thick sample imaging.
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5
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D'Amico M, Di Franco E, Cerutti E, Barresi V, Condorelli D, Diaspro A, Lanzanò L. A phasor-based approach to improve optical sectioning in any confocal microscope with a tunable pinhole. Microsc Res Tech 2022; 85:3207-3216. [PMID: 35686877 PMCID: PMC9542401 DOI: 10.1002/jemt.24178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/26/2022] [Accepted: 05/29/2022] [Indexed: 01/20/2023]
Abstract
Confocal fluorescence microscopy is a well‐established imaging technique capable of generating thin optical sections of biological specimens. Optical sectioning in confocal microscopy is mainly determined by the size of the pinhole, a small aperture placed in front of a point detector. In principle, imaging with a closed pinhole provides the highest degree of optical sectioning. In practice, the dramatic reduction of signal‐to‐noise ratio (SNR) at smaller pinhole sizes makes challenging the use of pinhole sizes significantly smaller than 1 Airy Unit (AU). Here, we introduce a simple method to “virtually” perform confocal imaging at smaller pinhole sizes without the dramatic reduction of SNR. The method is based on the sequential acquisition of multiple confocal images acquired at different pinhole aperture sizes and image processing based on a phasor analysis. The implementation is conceptually similar to separation of photons by lifetime tuning (SPLIT), a technique that exploits the phasor analysis to achieve super‐resolution, and for this reason we call this method SPLIT‐pinhole (SPLIT‐PIN). We show with simulated data that the SPLIT‐PIN image can provide improved optical sectioning (i.e., virtually smaller pinhole size) but better SNR with respect to an image obtained with closed pinhole. For instance, two images acquired at 2 and 1 AU can be combined to obtain a SPLIT‐PIN image with a virtual pinhole size of 0.2 AU but with better SNR. As an example of application to biological imaging, we show that SPLIT‐PIN improves confocal imaging of the apical membrane in an in vitro model of the intestinal epithelium.
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Affiliation(s)
- Morgana D'Amico
- Department of Physics and Astronomy "Ettore Majorana", University of Catania, Catania, Italy
| | - Elisabetta Di Franco
- Department of Physics and Astronomy "Ettore Majorana", University of Catania, Catania, Italy
| | - Elena Cerutti
- Department of Physics and Astronomy "Ettore Majorana", University of Catania, Catania, Italy.,Nanoscopy, CHT Erzelli, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Vincenza Barresi
- Department of Biomedical and Biotechnological Sciences, Section of Medical Biochemistry, University of Catania, Catania, Italy
| | - Daniele Condorelli
- Department of Biomedical and Biotechnological Sciences, Section of Medical Biochemistry, University of Catania, Catania, Italy
| | - Alberto Diaspro
- Nanoscopy, CHT Erzelli, Istituto Italiano di Tecnologia, Genoa, Italy.,DIFILAB, Department of Physics, University of Genoa, Genoa, Italy
| | - Luca Lanzanò
- Department of Physics and Astronomy "Ettore Majorana", University of Catania, Catania, Italy.,Nanoscopy, CHT Erzelli, Istituto Italiano di Tecnologia, Genoa, Italy
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6
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Galiani S, Reglinski K, Carravilla P, Barbotin A, Urbančič I, Ott J, Sehr J, Sezgin E, Schneider F, Waithe D, Hublitz P, Schliebs W, Erdmann R, Eggeling C. Diffusion and interaction dynamics of the cytosolic peroxisomal import receptor PEX5. BIOPHYSICAL REPORTS 2022; 2:None. [PMID: 36299769 PMCID: PMC9586885 DOI: 10.1016/j.bpr.2022.100055] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 03/24/2022] [Indexed: 11/18/2022]
Abstract
Cellular functions rely on proper actions of organelles such as peroxisomes. These organelles rely on the import of proteins from the cytosol. The peroxisomal import receptor PEX5 takes up target proteins in the cytosol and transports them to the peroxisomal matrix. However, its cytosolic molecular interactions have so far not directly been disclosed. Here, we combined advanced optical microscopy and spectroscopy techniques such as fluorescence correlation spectroscopy and stimulated emission depletion microscopy with biochemical tools to present a detailed characterization of the cytosolic diffusion and interaction dynamics of PEX5. Among other features, we highlight a slow diffusion of PEX5, independent of aggregation or target binding, but associated with cytosolic interaction partners via its N-terminal domain. This sheds new light on the functionality of the receptor in the cytosol as well as highlighting the potential of using complementary microscopy tools to decipher molecular interactions in the cytosol by studying their diffusion dynamics.
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Affiliation(s)
- S. Galiani
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
- Wolfson Imaging Centre, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - K. Reglinski
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
- Leibniz-Institute of Photonic Technologies e.V., Jena, Germany
- Institute of Applied Optic and Biophysics, Friedrich-Schiller University Jena, Jena, Germany
- University Hospital Jena, Jena, Germany
| | - P. Carravilla
- Leibniz-Institute of Photonic Technologies e.V., Jena, Germany
- Institute of Applied Optic and Biophysics, Friedrich-Schiller University Jena, Jena, Germany
- Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Bilbao, Spain
- Instituto Biofisika (UPV/EHU, CSIC), University of the Basque Country, Leioa, Spain
| | - A. Barbotin
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
- Department of Engineering Science, University of Oxford, Oxford, UK
| | - I. Urbančič
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
- Laboratory of Biophysics, Condensed Matter Physics Department, Jožef Stefan Institute, Ljubljana, Slovenia
| | - J. Ott
- Institute of Biochemistry and Pathobiochemistry, Systems Biochemistry, Ruhr-University Bochum, Bochum, Germany
| | - J. Sehr
- Institute of Biochemistry and Pathobiochemistry, Systems Biochemistry, Ruhr-University Bochum, Bochum, Germany
| | - E. Sezgin
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
- Science for Life Laboratory, Department of Women’s and Children’s Health, Karolinska Institutet, Solna, Sweden
| | - F. Schneider
- Kennedy Institute for Rheumatology, University of Oxford, Oxford, UK
| | - D. Waithe
- Wolfson Imaging Centre, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
- WIMM Centre for Computational Biology , MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - P. Hublitz
- WIMM Genome Engineering Services, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - W. Schliebs
- Institute of Biochemistry and Pathobiochemistry, Systems Biochemistry, Ruhr-University Bochum, Bochum, Germany
| | - R. Erdmann
- Institute of Biochemistry and Pathobiochemistry, Systems Biochemistry, Ruhr-University Bochum, Bochum, Germany
| | - C. Eggeling
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
- Wolfson Imaging Centre, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
- Leibniz-Institute of Photonic Technologies e.V., Jena, Germany
- Institute of Applied Optic and Biophysics, Friedrich-Schiller University Jena, Jena, Germany
- Jena Center for Soft Matter (JCSM), Jena, Germany
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7
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Irgen-Gioro S, Yoshida S, Walling V, Chong S. Fixation can change the appearance of phase separation in living cells. eLife 2022; 11:79903. [PMID: 36444977 PMCID: PMC9817179 DOI: 10.7554/elife.79903] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 11/28/2022] [Indexed: 11/30/2022] Open
Abstract
Fixing cells with paraformaldehyde (PFA) is an essential step in numerous biological techniques as it is thought to preserve a snapshot of biomolecular transactions in living cells. Fixed-cell imaging techniques such as immunofluorescence have been widely used to detect liquid-liquid phase separation (LLPS) in vivo. Here, we compared images, before and after fixation, of cells expressing intrinsically disordered proteins that are able to undergo LLPS. Surprisingly, we found that PFA fixation can both enhance and diminish putative LLPS behaviors. For specific proteins, fixation can even cause their droplet-like puncta to artificially appear in cells that do not have any detectable puncta in the live condition. Fixing cells in the presence of glycine, a molecule that modulates fixation rates, can reverse the fixation effect from enhancing to diminishing LLPS appearance. We further established a kinetic model of fixation in the context of dynamic protein-protein interactions. Simulations based on the model suggest that protein localization in fixed cells depends on an intricate balance of protein-protein interaction dynamics, the overall rate of fixation, and notably, the difference between fixation rates of different proteins. Consistent with simulations, live-cell single-molecule imaging experiments showed that a fast overall rate of fixation relative to protein-protein interaction dynamics can minimize fixation artifacts. Our work reveals that PFA fixation changes the appearance of LLPS from living cells, presents a caveat in studying LLPS using fixation-based methods, and suggests a mechanism underlying the fixation artifact.
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Affiliation(s)
- Shawn Irgen-Gioro
- Division of Chemistry and Chemical Engineering, California Institute of TechnologyPasadenaUnited States
| | - Shawn Yoshida
- Division of Chemistry and Chemical Engineering, California Institute of TechnologyPasadenaUnited States,Division of Biology and Biological Engineering, California Institute of TechnologyPasadenaUnited States
| | - Victoria Walling
- Division of Chemistry and Chemical Engineering, California Institute of TechnologyPasadenaUnited States
| | - Shasha Chong
- Division of Chemistry and Chemical Engineering, California Institute of TechnologyPasadenaUnited States
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8
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Cerutti E, D'Amico M, Cainero I, Dellino GI, Faretta M, Vicidomini G, Pelicci PG, Bianchini P, Diaspro A, Lanzanò L. Evaluation of sted super-resolution image quality by image correlation spectroscopy (QuICS). Sci Rep 2021; 11:20782. [PMID: 34675304 PMCID: PMC8531054 DOI: 10.1038/s41598-021-00301-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 10/08/2021] [Indexed: 12/05/2022] Open
Abstract
Quantifying the imaging performances in an unbiased way is of outmost importance in super-resolution microscopy. Here, we describe an algorithm based on image correlation spectroscopy (ICS) that can be used to assess the quality of super-resolution images. The algorithm is based on the calculation of an autocorrelation function and provides three different parameters: the width of the autocorrelation function, related to the spatial resolution; the brightness, related to the image contrast; the relative noise variance, related to the signal-to-noise ratio of the image. We use this algorithm to evaluate the quality of stimulated emission depletion (STED) images of DNA replication foci in U937 cells acquired under different imaging conditions. Increasing the STED depletion power improves the resolution but may reduce the image contrast. Increasing the number of line averages improves the signal-to-noise ratio but facilitates the onset of photobleaching and subsequent reduction of the image contrast. Finally, we evaluate the performances of two different separation of photons by lifetime tuning (SPLIT) approaches: the method of tunable STED depletion power and the commercially available Leica Tau-STED. We find that SPLIT provides an efficient way to improve the resolution and contrast in STED microscopy.
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Affiliation(s)
- Elena Cerutti
- Department of Physics and Astronomy "Ettore Majorana", University of Catania, Via S. Sofia 64, 95123, Catania, Italy.,Nanoscopy and NIC@IIT, CHT Erzelli, Istituto Italiano di Tecnologia, Via Enrico Melen 83, Building B, 16152, Genoa, Italy
| | - Morgana D'Amico
- Department of Physics and Astronomy "Ettore Majorana", University of Catania, Via S. Sofia 64, 95123, Catania, Italy
| | - Isotta Cainero
- Nanoscopy and NIC@IIT, CHT Erzelli, Istituto Italiano di Tecnologia, Via Enrico Melen 83, Building B, 16152, Genoa, Italy
| | - Gaetano Ivan Dellino
- Department of Experimental Oncology, IEO, European Institute of Oncology IRCCS, 20139, Milan, Italy.,Department of Oncology and Hemato-Oncology, University of Milan, 20122, Milan, Italy
| | - Mario Faretta
- Department of Experimental Oncology, IEO, European Institute of Oncology IRCCS, 20139, Milan, Italy
| | - Giuseppe Vicidomini
- Molecular Microscopy and Spectroscopy, CHT Erzelli, Istituto Italiano di Tecnologia, Via Enrico Melen 83, Building B, 16152, Genoa, Italy
| | - Pier Giuseppe Pelicci
- Department of Experimental Oncology, IEO, European Institute of Oncology IRCCS, 20139, Milan, Italy.,Department of Oncology and Hemato-Oncology, University of Milan, 20122, Milan, Italy
| | - Paolo Bianchini
- Nanoscopy and NIC@IIT, CHT Erzelli, Istituto Italiano di Tecnologia, Via Enrico Melen 83, Building B, 16152, Genoa, Italy
| | - Alberto Diaspro
- Nanoscopy and NIC@IIT, CHT Erzelli, Istituto Italiano di Tecnologia, Via Enrico Melen 83, Building B, 16152, Genoa, Italy.,DIFILAB, Department of Physics, University of Genoa, via Dodecaneso 33, 16143, Genoa, Italy
| | - Luca Lanzanò
- Department of Physics and Astronomy "Ettore Majorana", University of Catania, Via S. Sofia 64, 95123, Catania, Italy. .,Nanoscopy and NIC@IIT, CHT Erzelli, Istituto Italiano di Tecnologia, Via Enrico Melen 83, Building B, 16152, Genoa, Italy.
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9
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Advanced Static and Dynamic Fluorescence Microscopy Techniques to Investigate Drug Delivery Systems. Pharmaceutics 2021; 13:pharmaceutics13060861. [PMID: 34208080 PMCID: PMC8230741 DOI: 10.3390/pharmaceutics13060861] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 06/07/2021] [Accepted: 06/08/2021] [Indexed: 01/01/2023] Open
Abstract
In the past decade(s), fluorescence microscopy and laser scanning confocal microscopy (LSCM) have been widely employed to investigate biological and biomimetic systems for pharmaceutical applications, to determine the localization of drugs in tissues or entire organisms or the extent of their cellular uptake (in vitro). However, the diffraction limit of light, which limits the resolution to hundreds of nanometers, has for long time restricted the extent and quality of information and insight achievable through these techniques. The advent of super-resolution microscopic techniques, recognized with the 2014 Nobel prize in Chemistry, revolutionized the field thanks to the possibility to achieve nanometric resolution, i.e., the typical scale length of chemical and biological phenomena. Since then, fluorescence microscopy-related techniques have acquired renewed interest for the scientific community, both from the perspective of instrument/techniques development and from the perspective of the advanced scientific applications. In this contribution we will review the application of these techniques to the field of drug delivery, discussing how the latest advancements of static and dynamic methodologies have tremendously expanded the experimental opportunities for the characterization of drug delivery systems and for the understanding of their behaviour in biologically relevant environments.
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10
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Fluorescence Fluctuation Spectroscopy enables quantification of potassium channel subunit dynamics and stoichiometry. Sci Rep 2021; 11:10719. [PMID: 34021177 PMCID: PMC8140153 DOI: 10.1038/s41598-021-90002-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 04/15/2021] [Indexed: 11/08/2022] Open
Abstract
Voltage-gated potassium (Kv) channels are a family of membrane proteins that facilitate K+ ion diffusion across the plasma membrane, regulating both resting and action potentials. Kv channels comprise four pore-forming α subunits, each with a voltage sensing domain, and they are regulated by interaction with β subunits such as those belonging to the KCNE family. Here we conducted a comprehensive biophysical characterization of stoichiometry and protein diffusion across the plasma membrane of the epithelial KCNQ1-KCNE2 complex, combining total internal reflection fluorescence (TIRF) microscopy and a series of complementary Fluorescence Fluctuation Spectroscopy (FFS) techniques. Using this approach, we found that KCNQ1-KCNE2 has a predominant 4:4 stoichiometry, while non-bound KCNE2 subunits are mostly present as dimers in the plasma membrane. At the same time, we identified unique spatio-temporal diffusion modalities and nano-environment organization for each channel subunit. These findings improve our understanding of KCNQ1-KCNE2 channel function and suggest strategies for elucidating the subunit stoichiometry and forces directing localization and diffusion of ion channel complexes in general.
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11
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Gao P, Nienhaus GU. Axial line-scanning stimulated emission depletion fluorescence correlation spectroscopy. OPTICS LETTERS 2021; 46:2184-2187. [PMID: 33929450 DOI: 10.1364/ol.420765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 04/01/2021] [Indexed: 06/12/2023]
Abstract
Investigating the dynamics and interactions of biomolecules within or attached to membranes of living cells is crucial for understanding biology at the molecular level. In this pursuit, classical, diffraction-limited optical fluorescence microscopy is widely used, but it faces limitations due to (1) the heterogeneity of biomembranes on the nanoscale and (2) the intrinsic motion of membranes with respect to the focus. Here we introduce a new confocal microscopy-based fluctuation spectroscopy technique aimed at alleviating these two problems, called axial line-scanning stimulated emission depletion fluorescence correlation spectroscopy (axial ls-STED-FCS). Axial line scanning by means of a tunable acoustic gradient index of refraction lens provides a time resolution of a few microseconds, which is more than two orders of magnitude greater than that of conventional, lateral line-scanning fluorescence correlation spectroscopy (typically around 1 ms). Using STED excitation, the observation area on the membrane can be reduced 10-100 fold, resulting in sub-diffraction spatial resolution and the ability to study samples with densely labeled membranes. Due to these attractive properties, we expect that the axial ls-STED-FCS will find wide application, especially in the biomolecular sciences.
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12
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Obashi K, Taraska JW, Okabe S. The role of molecular diffusion within dendritic spines in synaptic function. J Gen Physiol 2021; 153:e202012814. [PMID: 33720306 PMCID: PMC7967910 DOI: 10.1085/jgp.202012814] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 02/16/2021] [Indexed: 12/21/2022] Open
Abstract
Spines are tiny nanoscale protrusions from dendrites of neurons. In the cortex and hippocampus, most of the excitatory postsynaptic sites reside in spines. The bulbous spine head is connected to the dendritic shaft by a thin membranous neck. Because the neck is narrow, spine heads are thought to function as biochemically independent signaling compartments. Thus, dynamic changes in the composition, distribution, mobility, conformations, and signaling properties of molecules contained within spines can account for much of the molecular basis of postsynaptic function and regulation. A major factor in controlling these changes is the diffusional properties of proteins within this small compartment. Advances in measurement techniques using fluorescence microscopy now make it possible to measure molecular diffusion within single dendritic spines directly. Here, we review the regulatory mechanisms of diffusion in spines by local intra-spine architecture and discuss their implications for neuronal signaling and synaptic plasticity.
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Affiliation(s)
- Kazuki Obashi
- Biochemistry and Biophysics Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD
| | - Justin W. Taraska
- Biochemistry and Biophysics Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD
| | - Shigeo Okabe
- Department of Cellular Neurobiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
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13
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14
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Wu Z, Xu X, Xi P. Stimulated emission depletion microscopy for biological imaging in four dimensions: A review. Microsc Res Tech 2021; 84:1947-1958. [PMID: 33713513 DOI: 10.1002/jemt.23750] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 02/27/2021] [Indexed: 12/26/2022]
Abstract
Stimulated emission depletion (STED) microscopy allows high lateral and axial resolution, long term imaging in living cells. Here we review recent technical advances in STED microscopy, with emphasis on resolution and measurement range of XYZt four dimensions. Different STED technical advances and novel STED probes are discussed with their respective application in biological subcellular imaging. This review may serve as a practical guide for choosing a suitable approach to the advanced STED super-resolution imaging.
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Affiliation(s)
- Zhaoyang Wu
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, China
| | - Xinzhu Xu
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, China
| | - Peng Xi
- Department of Biomedical Engineering, College of Engineering, Peking University, Beijing, China.,UTS-SUSTech Joint Research Centre for Biomedical Materials and Devices, Department of Biomedical Engineering, College of Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
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15
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Slenders E, Castello M, Buttafava M, Villa F, Tosi A, Lanzanò L, Koho SV, Vicidomini G. Confocal-based fluorescence fluctuation spectroscopy with a SPAD array detector. LIGHT, SCIENCE & APPLICATIONS 2021; 10:31. [PMID: 33542179 PMCID: PMC7862647 DOI: 10.1038/s41377-021-00475-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 12/17/2020] [Accepted: 01/14/2021] [Indexed: 05/13/2023]
Abstract
The combination of confocal laser-scanning microscopy (CLSM) and fluorescence fluctuation spectroscopy (FFS) is a powerful tool in studying fast, sub-resolution biomolecular processes in living cells. A detector array can further enhance CLSM-based FFS techniques, as it allows the simultaneous acquisition of several samples-essentially images-of the CLSM detection volume. However, the detector arrays that have previously been proposed for this purpose require tedious data corrections and preclude the combination of FFS with single-photon techniques, such as fluorescence lifetime imaging. Here, we solve these limitations by integrating a novel single-photon-avalanche-diode (SPAD) array detector in a CLSM system. We validate this new implementation on a series of FFS analyses: spot-variation fluorescence correlation spectroscopy, pair-correlation function analysis, and image-derived mean squared displacement analysis. We predict that the unique combination of spatial and temporal information provided by our detector will make the proposed architecture the method of choice for CLSM-based FFS.
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Affiliation(s)
- Eli Slenders
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Marco Castello
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Mauro Buttafava
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Federica Villa
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Alberto Tosi
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Luca Lanzanò
- Nanoscopy and NIC@IIT, Istituto Italiano di Tecnologia, Genoa, Italy
- Dipartimento di Fisica e Astronomia, Università di Catania, Catania, Italy
| | - Sami Valtteri Koho
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Giuseppe Vicidomini
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy.
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16
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Schneider F, Colin-York H, Fritzsche M. Quantitative Bio-Imaging Tools to Dissect the Interplay of Membrane and Cytoskeletal Actin Dynamics in Immune Cells. Front Immunol 2021; 11:612542. [PMID: 33505401 PMCID: PMC7829180 DOI: 10.3389/fimmu.2020.612542] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 11/23/2020] [Indexed: 12/13/2022] Open
Abstract
Cellular function is reliant on the dynamic interplay between the plasma membrane and the actin cytoskeleton. This critical relationship is of particular importance in immune cells, where both the cytoskeleton and the plasma membrane work in concert to organize and potentiate immune signaling events. Despite their importance, there remains a critical gap in understanding how these respective dynamics are coupled, and how this coupling in turn may influence immune cell function from the bottom up. In this review, we highlight recent optical technologies that could provide strategies to investigate the simultaneous dynamics of both the cytoskeleton and membrane as well as their interplay, focusing on current and future applications in immune cells. We provide a guide of the spatio-temporal scale of each technique as well as highlighting novel probes and labels that have the potential to provide insights into membrane and cytoskeletal dynamics. The quantitative biophysical tools presented here provide a new and exciting route to uncover the relationship between plasma membrane and cytoskeletal dynamics that underlies immune cell function.
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Affiliation(s)
- Falk Schneider
- Medical Research Council (MRC) Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Huw Colin-York
- Medical Research Council (MRC) Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
- Kennedy Institute for Rheumatology, University of Oxford, Oxford, United Kingdom
| | - Marco Fritzsche
- Medical Research Council (MRC) Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
- Kennedy Institute for Rheumatology, University of Oxford, Oxford, United Kingdom
- Rosalind Franklin Institute, Harwell Campus, Didcot, United Kingdom
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17
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Andrian T, Riera R, Pujals S, Albertazzi L. Nanoscopy for endosomal escape quantification. NANOSCALE ADVANCES 2021; 3:10-23. [PMID: 36131870 PMCID: PMC9419860 DOI: 10.1039/d0na00454e] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 10/26/2020] [Indexed: 05/04/2023]
Abstract
The successful cytosolic delivery of nanoparticles is hampered by their endosomal entrapment and degradation. To push forward the smart development of nanoparticles we must reliably detect and quantify their endosomal escape process. However, the current methods employed are not quantitative enough at the nanoscale to achieve this. Nanoscopy is a rapidly evolving field that has developed a diverse set of powerful techniques in the last two decades, opening the door to explore nanomedicine with an unprecedented resolution and specificity. The understanding of key steps in the drug delivery process - such as endosomal escape - would benefit greatly from the implementation of the most recent advances in microscopy. In this review, we provide the latest insights into endosomal escape of nanoparticles obtained by nanoscopy, and we discuss the features that would allow these techniques to make a great impact in the field.
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Affiliation(s)
- Teodora Andrian
- Nanoscopy for Nanomedicine, Institute for Bioengineering of Catalonia Barcelona Spain
| | - Roger Riera
- Department of Biomedical Engineering, Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology Eindhoven Netherlands
| | - Silvia Pujals
- Nanoscopy for Nanomedicine, Institute for Bioengineering of Catalonia Barcelona Spain
- Department of Electronics and Biomedical Engineering, Faculty of Physics, Universitat de Barcelona Av. Diagonal 647 08028 Barcelona Spain
| | - Lorenzo Albertazzi
- Nanoscopy for Nanomedicine, Institute for Bioengineering of Catalonia Barcelona Spain
- Department of Biomedical Engineering, Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology Eindhoven Netherlands
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18
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Barbotin A, Urbančič I, Galiani S, Eggeling C, Booth M. Background Reduction in STED-FCS Using a Bivortex Phase Mask. ACS PHOTONICS 2020; 7:1742-1753. [PMID: 32685609 PMCID: PMC7366504 DOI: 10.1021/acsphotonics.0c00388] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Indexed: 05/04/2023]
Abstract
Fluorescence correlation spectroscopy (FCS) is a valuable tool to study the molecular dynamics in living cells. When used together with a super-resolution stimulated emission depletion (STED) microscope, STED-FCS can measure diffusion processes on the nanoscale in living cells. In two-dimensional (2D) systems like the cellular plasma membrane, a ring-shaped depletion focus is most commonly used to increase the lateral resolution, leading to more than 25-fold decrease in the observation volume, reaching the relevant scale of supramolecular arrangements. However, STED-FCS faces severe limitations when measuring diffusion in three dimensions (3D), largely due to the spurious background contributions from undepleted areas of the excitation focus that reduce the signal quality and ultimately limit the resolution. In this paper, we investigate how different STED confinement modes can mitigate this issue. By simulations as well as experiments with fluorescent probes in solution and in cells, we demonstrate that the coherent-hybrid (CH) depletion pattern created by a bivortex phase mask reduces background most efficiently and thus provides superior signal quality under comparable reduction of the observation volume. Featuring also the highest robustness to common optical aberrations, CH-STED can be considered the method of choice for reliable STED-FCS-based investigations of 3D diffusion on the subdiffraction scale.
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Affiliation(s)
- Aurélien Barbotin
- Department
of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, United
Kingdom
| | - Iztok Urbančič
- MRC
Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, United Kingdom
- “Jožef
Stefan” Institute, Jamova cesta 39, SI-1000 Ljubljana, Slovenia
| | - Silvia Galiani
- MRC
Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, United Kingdom
- Wolfson
Imaging Centre Oxford, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, United Kingdom
| | - Christian Eggeling
- MRC
Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, United Kingdom
- Wolfson
Imaging Centre Oxford, MRC Weatherall Institute of Molecular Medicine, University of Oxford, 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
| | - Martin Booth
- Department
of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, United
Kingdom
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19
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Back to the Future: Genetically Encoded Fluorescent Proteins as Inert Tracers of the Intracellular Environment. Int J Mol Sci 2020; 21:ijms21114164. [PMID: 32545175 PMCID: PMC7312867 DOI: 10.3390/ijms21114164] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 06/09/2020] [Accepted: 06/09/2020] [Indexed: 01/08/2023] Open
Abstract
Over the past decades, the discovery and development of genetically encoded fluorescent proteins (FPs) has brought a revolution into our ability to study biologic phenomena directly within living matter. First, FPs enabled fluorescence-labeling of a variety of molecules of interest to study their localization, interactions and dynamic behavior at various scales-from cells to whole organisms/animals. Then, rationally engineered FP-based sensors facilitated the measurement of physicochemical parameters of living matter-especially at the intracellular level, such as ion concentration, temperature, viscosity, pressure, etc. In addition, FPs were exploited as inert tracers of the intracellular environment in which they are expressed. This oft-neglected role is made possible by two distinctive features of FPs: (i) the quite null, unspecific interactions of their characteristic β-barrel structure with the molecular components of the cellular environment; and (ii) their compatibility with the use of time-resolved fluorescence-based optical microscopy techniques. This review seeks to highlight the potential of such unique combinations of properties and report on the most significative and original applications (and related advancements of knowledge) produced to date. It is envisioned that the use of FPs as inert tracers of living matter structural organization holds a potential for several lines of further development in the next future, discussed in the last section of the review, which in turn can lead to new breakthroughs in bioimaging.
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20
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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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21
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Biswas J, Nunez L, Das S, Yoon YJ, Eliscovich C, Singer RH. Zipcode Binding Protein 1 (ZBP1; IGF2BP1): A Model for Sequence-Specific RNA Regulation. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2020; 84:1-10. [PMID: 32086331 DOI: 10.1101/sqb.2019.84.039396] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The fate of an RNA, from its localization, translation, and ultimate decay, is dictated by interactions with RNA binding proteins (RBPs). β-actin mRNA has functioned as the classic example of RNA localization in eukaryotic cells. Studies of β-actin mRNA over the past three decades have allowed understanding of how RBPs, such as ZBP1 (IGF2BP1), can control both RNA localization and translational status. Here, we summarize studies of β-actin mRNA and focus on how ZBP1 serves as a model for understanding interactions between RNA and their binding protein(s). Central to the study of RNA and RBPs were technological developments that occurred along the way. We conclude with a future outlook highlighting new technologies that may be used to address still unanswered questions about RBP-mediated regulation of mRNA during its life cycle, within the cell.
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Affiliation(s)
- Jeetayu Biswas
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Leti Nunez
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Sulagna Das
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Young J Yoon
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.,Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Carolina Eliscovich
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.,Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | - Robert H Singer
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.,Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.,Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, Virginia 20147, USA
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22
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Pelicci S, Diaspro A, Lanzanò L. Chromatin nanoscale compaction in live cells visualized by acceptor-to-donor ratio corrected Förster resonance energy transfer between DNA dyes. JOURNAL OF BIOPHOTONICS 2019; 12:e201900164. [PMID: 31365191 PMCID: PMC7065635 DOI: 10.1002/jbio.201900164] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 07/14/2019] [Accepted: 07/29/2019] [Indexed: 05/04/2023]
Abstract
@Chromatin nanoscale architecture in live cells can be studied by Förster resonance energy transfer (FRET) between fluorescently labeled chromatin components, such as histones. A higher degree of nanoscale compaction is detected as a higher FRET level, since this corresponds to a higher degree of proximity between donor and acceptor molecules. However, in such a system, the stoichiometry of the donors and acceptors engaged in the FRET process is not well defined and, in principle, FRET variations could be caused by variations in the acceptor-to-donor ratio rather than distance. Here, to get a FRET level independent of the acceptor-to-donor ratio, we combine fluorescence lifetime imaging detection of FRET with a normalization of the FRET level to a pixel-wise estimation of the acceptor-to-donor ratio. We use this method to study FRET between two DNA binding dyes staining the nuclei of live cells. We show that this acceptor-to-donor ratio corrected FRET imaging reveals variations of nanoscale compaction in different chromatin environments. As an application, we monitor the rearrangement of chromatin in response to laser-induced microirradiation and reveal that DNA is rapidly decompacted, at the nanoscale, in response to DNA damage induction.
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Affiliation(s)
- Simone Pelicci
- Nanoscopy and Nikon Imaging Center, Istituto Italiano di TecnologiaGenoaItaly
- Department of PhysicsUniversity of GenoaGenoaItaly
| | - Alberto Diaspro
- Nanoscopy and Nikon Imaging Center, Istituto Italiano di TecnologiaGenoaItaly
- Department of PhysicsUniversity of GenoaGenoaItaly
| | - Luca Lanzanò
- Nanoscopy and Nikon Imaging Center, Istituto Italiano di TecnologiaGenoaItaly
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23
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Coto Hernández I, Castello M, Tortarolo G, Jowett N, Diaspro A, Lanzanò L, Vicidomini G. Efficient two-photon excitation stimulated emission depletion nanoscope exploiting spatiotemporal information. NEUROPHOTONICS 2019; 6:045004. [PMID: 31720309 PMCID: PMC6830046 DOI: 10.1117/1.nph.6.4.045004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 10/14/2019] [Indexed: 06/10/2023]
Abstract
Stimulated emission depletion (STED) microscopy is a powerful bioimaging technique that theoretically provides molecular spatial resolution while preserving the most important assets of fluorescence microscopy. When combined with two-photon excitation (2PE) microscopy (2PE-STED), subdiffraction resolution may be achieved for thick biological samples. The most straightforward implementation of 2PE-STED microscopy entails introduction of an STED beam operating in continuous wave (CW) into a conventional Ti:sapphire-based 2PE microscope (2PE CW-STED). In this implementation, resolution enhancement is typically achieved using time-gated detection schemes, often resulting in drastic signal-to-noise/-background ratio (SNR/SBR) reductions. Herein, we employ a pixel-by-pixel phasor approach to discard fluorescence photons lacking super-resolution information to enhance image SNR/SBR in 2PE CW-STED microscopy. We compare this separation of photons by lifetime tuning approach against other postprocessing algorithms and combine it with image deconvolution to further optimize image quality.
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Affiliation(s)
- Iván Coto Hernández
- Massachusetts Eye and Ear and Harvard Medical School, Surgical Photonics and Engineering Laboratory, Boston, United States
| | - Marco Castello
- Istituto Italiano di Tecnologia, Molecular Microscopy and Spectroscopy, Genoa, Italy
| | - Giorgio Tortarolo
- Istituto Italiano di Tecnologia, Molecular Microscopy and Spectroscopy, Genoa, Italy
| | - Nate Jowett
- Massachusetts Eye and Ear and Harvard Medical School, Surgical Photonics and Engineering Laboratory, Boston, United States
| | - Alberto Diaspro
- Istituto Italiano di Tecnologia, Nanoscopy and NIC@IIT, Genoa, Italy
- University of Genoa, Department of Physics, Genoa, Italy
| | - Luca Lanzanò
- Istituto Italiano di Tecnologia, Nanoscopy and NIC@IIT, Genoa, Italy
| | - Giuseppe Vicidomini
- Istituto Italiano di Tecnologia, Molecular Microscopy and Spectroscopy, Genoa, Italy
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24
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Barbotin A, Galiani S, Urbančič I, Eggeling C, Booth MJ. Adaptive optics allows STED-FCS measurements in the cytoplasm of living cells. OPTICS EXPRESS 2019; 27:23378-23395. [PMID: 31510616 PMCID: PMC6825603 DOI: 10.1364/oe.27.023378] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 06/17/2019] [Indexed: 05/18/2023]
Abstract
Fluorescence correlation spectroscopy in combination with super-resolution stimulated emission depletion microscopy (STED-FCS) is a powerful tool to investigate molecular diffusion with sub-diffraction resolution. It has been of particular use for investigations of two dimensional systems like cell membranes, but has so far seen very limited applications to studies of three-dimensional diffusion. One reason for this is the extreme sensitivity of the axial (z) STED depletion pattern to optical aberrations. We present here an adaptive optics-based correction method that compensates for these aberrations and allows STED-FCS measurements in the cytoplasm of living cells.
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Affiliation(s)
- Aurélien Barbotin
- Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ,
UK
| | - Silvia Galiani
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS,
UK
- Wolfson Imaging Centre Oxford, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS,
UK
| | - Iztok Urbančič
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS,
UK
- “Jožef Stefan” Institute, Jamova cesta 39, SI-1000 Ljubljana,
Slovenia
| | - Christian Eggeling
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS,
UK
- Wolfson Imaging Centre Oxford, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS,
UK
- 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
| | - Martin J. Booth
- Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ,
UK
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25
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Abstract
STimulated emission depletion (STED) nanoscopy has been proposed to extend greatly our capability of using light to study a variety of biological problems with nanometer-scale resolution. However, in practice the unwanted background noise degrades the STED image quality and precludes quantitative analysis. Here, we discuss the underlying sources of the background noise in STED images, and review current approaches to alleviate this problem, such as time-gating, anti-Stokes excitation removal, and off-focus incomplete depletion suppression. Progress in correcting uncorrelated background photons in fluorescence correlation spectroscopy combined with STED (STED-FCS) will also be discussed.
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Affiliation(s)
- Ye Ma
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States of America
| | - Taekjip Ha
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States of America.,Departments of Biophysics and Biophysical Chemistry, Biophysics, Johns Hopkins University, Baltimore, MD, United States of America.,Howard Hughes Medical Institute, Baltimore, MD, United States of America.,Author to whom any correspondence should be addressed
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26
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Fluorescence fluctuation spectroscopy: an invaluable microscopy tool for uncovering the biophysical rules for navigating the nuclear landscape. Biochem Soc Trans 2019; 47:1117-1129. [DOI: 10.1042/bst20180604] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 06/03/2019] [Accepted: 06/05/2019] [Indexed: 11/17/2022]
Abstract
Abstract
Nuclear architecture is fundamental to the manner by which molecules traverse the nucleus. The nucleoplasm is a crowded environment where dynamic rearrangements in local chromatin compaction locally redefine the space accessible toward nuclear protein diffusion. Here, we review a suite of methods based on fluorescence fluctuation spectroscopy (FFS) and how they have been employed to interrogate chromatin organization, as well as the impact this structural framework has on nuclear protein target search. From first focusing on a set of studies that apply FFS to an inert fluorescent tracer diffusing inside the nucleus of a living cell, we demonstrate the capacity of this technology to measure the accessibility of the nucleoplasm. Then with a baseline understanding of the exploration volume available to nuclear proteins during target search, we review direct applications of FFS to fluorescently labeled transcription factors (TFs). FFS can detect changes in TF mobility due to DNA binding, as well as the formation of TF complexes via changes in brightness due to oligomerization. Collectively, we find that FFS-based methods can uncover how nuclear proteins in general navigate the nuclear landscape.
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27
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Obashi K, Matsuda A, Inoue Y, Okabe S. Precise Temporal Regulation of Molecular Diffusion within Dendritic Spines by Actin Polymers during Structural Plasticity. Cell Rep 2019; 27:1503-1515.e8. [DOI: 10.1016/j.celrep.2019.04.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 02/22/2019] [Accepted: 03/29/2019] [Indexed: 10/26/2022] Open
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28
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Sezgin E, Schneider F, Galiani S, Urbančič I, Waithe D, Lagerholm BC, Eggeling C. Measuring nanoscale diffusion dynamics in cellular membranes with super-resolution STED-FCS. Nat Protoc 2019; 14:1054-1083. [PMID: 30842616 DOI: 10.1038/s41596-019-0127-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 01/04/2019] [Indexed: 11/08/2022]
Abstract
Super-resolution microscopy techniques enable optical imaging in live cells with unprecedented spatial resolution. They unfortunately lack the temporal resolution required to directly investigate cellular dynamics at scales sufficient to measure molecular diffusion. These fast time scales are, on the other hand, routinely accessible by spectroscopic techniques such as fluorescence correlation spectroscopy (FCS). To enable the direct investigation of fast dynamics at the relevant spatial scales, FCS has been combined with super-resolution stimulated emission depletion (STED) microscopy. STED-FCS has been applied in point or scanning mode to reveal nanoscale diffusion behavior of molecules in live cells. In this protocol, we describe the technical details of performing point STED-FCS (pSTED-FCS) and scanning STED-FCS (sSTED-FCS) measurements, from calibration and sample preparation to data acquisition and analysis. We give particular emphasis to 2D diffusion dynamics in cellular membranes, using molecules tagged with organic fluorophores. These measurements can be accomplished within 4-6 h by those proficient in fluorescence imaging.
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Affiliation(s)
- Erdinc Sezgin
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK.
| | - Falk Schneider
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - Silvia Galiani
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - Iztok Urbančič
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
- Solid State Physics Department, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Dominic Waithe
- Wolfson Imaging Centre, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
- MRC Centre for Computational Biology, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - B Christoffer Lagerholm
- Wolfson Imaging Centre, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - Christian Eggeling
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK.
- Wolfson Imaging Centre, MRC Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK.
- Institute of Applied Optics, Friedrich-Schiller-University Jena, Jena, Germany.
- Department of Biophysical Imaging, Leibniz Institute of Photonic Technology e.V., Jena, Germany.
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29
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Di Bona M, Mancini MA, Mazza D, Vicidomini G, Diaspro A, Lanzanò L. Measuring Mobility in Chromatin by Intensity-Sorted FCS. Biophys J 2019; 116:987-999. [PMID: 30819566 PMCID: PMC6428914 DOI: 10.1016/j.bpj.2019.02.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 01/14/2019] [Accepted: 02/08/2019] [Indexed: 12/12/2022] Open
Abstract
The architectural organization of chromatin can play an important role in genome regulation by affecting the mobility of molecules within its surroundings via binding interactions and molecular crowding. The diffusion of molecules at specific locations in the nucleus can be studied by fluorescence correlation spectroscopy (FCS), a well-established technique based on the analysis of fluorescence intensity fluctuations detected in a confocal observation volume. However, detecting subtle variations of mobility between different chromatin regions remains challenging with currently available FCS methods. Here, we introduce a method that samples multiple positions by slowly scanning the FCS observation volume across the nucleus. Analyzing the data in short time segments, we preserve the high temporal resolution of single-point FCS while probing different nuclear regions in the same cell. Using the intensity level of the probe (or a DNA marker) as a reference, we efficiently sort the FCS segments into different populations and obtain average correlation functions that are associated to different chromatin regions. This sorting and averaging strategy renders the method statistically robust while preserving the observation of intranuclear variations of mobility. Using this approach, we quantified diffusion of monomeric GFP in high versus low chromatin density regions. We found that GFP mobility was reduced in heterochromatin, especially within perinucleolar heterochromatin. Moreover, we found that modulation of chromatin compaction by ATP depletion, or treatment with solutions of different osmolarity, differentially affected the ratio of diffusion in both regions. Then, we used the approach to probe the mobility of estrogen receptor-α in the vicinity of an integrated multicopy prolactin gene array. Finally, we discussed the coupling of this method with stimulated emission depletion FCS for performing FCS at subdiffraction spatial scales.
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Affiliation(s)
- Melody Di Bona
- Nanoscopy and Nikon Imaging Center, Istituto Italiano di Tecnologia, Genoa, Italy; Department of Physics, University of Genoa, Genoa, Italy
| | - Michael A Mancini
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas
| | - Davide Mazza
- Experimental Imaging Center Ospedale San Raffaele, Milano, Italy; The European Center for Nanomedicine, Milano, Italy
| | - Giuseppe Vicidomini
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Alberto Diaspro
- Nanoscopy and Nikon Imaging Center, Istituto Italiano di Tecnologia, Genoa, Italy; Department of Physics, University of Genoa, Genoa, Italy.
| | - Luca Lanzanò
- Nanoscopy and Nikon Imaging Center, Istituto Italiano di Tecnologia, Genoa, Italy.
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30
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Huang JA, Caprettini V, Zhao Y, Melle G, Maccaferri N, Deleye L, Zambrana-Puyalto X, Ardini M, Tantussi F, Dipalo M, De Angelis F. On-Demand Intracellular Delivery of Single Particles in Single Cells by 3D Hollow Nanoelectrodes. NANO LETTERS 2019; 19:722-731. [PMID: 30673248 PMCID: PMC6378653 DOI: 10.1021/acs.nanolett.8b03764] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Delivery of molecules into intracellular compartments is one of the fundamental requirements in molecular biology. However, the possibility of delivering a precise number of nano-objects with single-particle resolution is still an open challenge. Here we present an electrophoretic platform based on 3D hollow nanoelectrodes to enable delivery of single nanoparticles into single selected cells and monitoring of the single-particle delivery by surface-enhanced Raman scattering (SERS). The gold-coated hollow nanoelectrode capable of confinement and enhancement of electromagnetic fields upon laser illumination can distinguish the SERS signals of a single nanoparticle flowing through the nanoelectrode. Tight wrapping of cell membranes around the nanoelectrodes allows effective membrane electroporation such that single gold nanorods are delivered on demand into a living cell by electrophoresis. The capability of the 3D hollow nanoelectrodes to porate cells and reveal single emitters from the background in continuous flow is promising for the analysis of both intracellular delivery and sampling.
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Affiliation(s)
- Jian-An Huang
- Istituto
Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Valeria Caprettini
- Istituto
Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
- DIBRIS, University of Genoa, Via all’Opera Pia 13, 16145 Genova, Italy
| | - Yingqi Zhao
- Istituto
Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - Giovanni Melle
- Istituto
Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
- DIBRIS, University of Genoa, Via all’Opera Pia 13, 16145 Genova, Italy
| | | | - Lieselot Deleye
- Istituto
Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | | | - Matteo Ardini
- Istituto
Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | | | - Michele Dipalo
- Istituto
Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
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31
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Scipioni L, Lanzanó L, Diaspro A, Gratton E. Comprehensive correlation analysis for super-resolution dynamic fingerprinting of cellular compartments using the Zeiss Airyscan detector. Nat Commun 2018; 9:5120. [PMID: 30504919 PMCID: PMC6269422 DOI: 10.1038/s41467-018-07513-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 10/29/2018] [Indexed: 11/08/2022] Open
Abstract
The availability of the Airyscan detector in the Zeiss LSM 880 has made possible the development of a new concept in fluctuation correlation spectroscopy using super-resolution. The Airyscan unit acquires data simultaneously on 32 detectors arranged in a hexagonal array. This detector opens up the possibility to use fluctuation methods based on time correlation at single points or at a number of points simultaneously, as well as methods based on spatial correlation in the area covered by the detector. Given the frame rate of this detector, millions of frames can be acquired in seconds, providing a robust statistical basis for fluctuation data. We apply the comprehensive analysis to the molecular fluctuations of free GFP diffusing in live cells at different subcellular compartments to show that at the nanoscale different cell environments can be distinguished by the comprehensive fluctuation analysis.
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Affiliation(s)
- L Scipioni
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, 92697, CA, USA
| | - L Lanzanó
- Nanoscopy, Istituto Italiano di Tecnologia, Genoa, 16163, Italy
| | - A Diaspro
- Nanoscopy, Istituto Italiano di Tecnologia, Genoa, 16163, Italy
- Nikon Imaging Center, Istituto Italiano di Tecnologia, Genoa, 16163, Italy
| | - E Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, 92697, CA, USA.
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32
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Abstract
Catalysis and mobility of reactants in fluid are normally thought to be decoupled. Violating this classical paradigm, this paper presents the catalyst laws of motion. Comparing experimental data to the theory presented here, we conclude that part of the free energy released by chemical reaction is channeled into driving catalysts to execute wormlike trajectories by piconewton forces performing work of a few kBT against fluid viscosity, where the rotational diffusion rate dictates the trajectory persistence length. This active motion agitates the fluid medium and produces antichemotaxis, the migration of catalyst down the gradient of the reactant concentration. Alternative explanations of enhanced catalyst mobility are examined critically. Using a microscopic theory to analyze experiments, we demonstrate that enzymes are active matter. Superresolution fluorescence measurements—performed across four orders of magnitude of substrate concentration, with emphasis on the biologically relevant regime around or below the Michaelis–Menten constant—show that catalysis boosts the motion of enzymes to be superdiffusive for a few microseconds, enhancing their effective diffusivity over longer timescales. Occurring at the catalytic turnover rate, these fast ballistic leaps maintain direction over a duration limited by rotational diffusion, driving enzymes to execute wormlike trajectories by piconewton forces performing work of a few kBT against viscosity. The boosts are more frequent at high substrate concentrations, biasing the trajectories toward substrate-poor regions, thus exhibiting antichemotaxis, demonstrated here experimentally over a wide range of aqueous concentrations. Alternative noncatalytic, passive mechanisms that predict chemotaxis, cross-diffusion, and phoresis, are critically analyzed. We examine the physical interpretation of our findings, speculate on the underlying mechanism, and discuss the avenues they open with biological and technological implications. These findings violate the classical paradigm that chemical reaction and motility are distinct processes, and suggest reaction–motion coupling as a general principle of catalysis.
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33
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Ponzellini P, Zambrana-Puyalto X, Maccaferri N, Lanzanò L, De Angelis F, Garoli D. Plasmonic zero mode waveguide for highly confined and enhanced fluorescence emission. NANOSCALE 2018; 10:17362-17369. [PMID: 30199084 DOI: 10.1039/c8nr04103b] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We fabricate a plasmonic nanoslot that is capable of performing enhanced single molecule detection at 10 μM concentrations. The nanoslot combines the tiny detection volume of a zero-mode waveguide and the field enhancement of a plasmonic nanohole. The nanoslot is fabricated on a bi-metallic film formed by the sequential deposition of gold and aluminum on a transparent substrate. Simulations of the structure yield an average near-field intensity enhancement of two orders of magnitude at its resonant frequency. Experimentally, we measure the fluorescence stemming from the nanoslot and compare it with that of a standard aluminum zero-mode waveguide. We also compare the detection volume for both structures. We observe that while both structures have a similar detection volume, the nanoslot yields a 25-fold fluorescence enhancement.
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Affiliation(s)
- Paolo Ponzellini
- Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy.
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34
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Sarmento MJ, Oneto M, Pelicci S, Pesce L, Scipioni L, Faretta M, Furia L, Dellino GI, Pelicci PG, Bianchini P, Diaspro A, Lanzanò L. Exploiting the tunability of stimulated emission depletion microscopy for super-resolution imaging of nuclear structures. Nat Commun 2018; 9:3415. [PMID: 30143630 PMCID: PMC6109149 DOI: 10.1038/s41467-018-05963-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 07/27/2018] [Indexed: 11/23/2022] Open
Abstract
Imaging of nuclear structures within intact eukaryotic nuclei is imperative to understand the effect of chromatin folding on genome function. Recent developments of super-resolution fluorescence microscopy techniques combine high specificity, sensitivity, and less-invasive sample preparation procedures with the sub-diffraction spatial resolution required to image chromatin at the nanoscale. Here, we present a method to enhance the spatial resolution of a stimulated-emission depletion (STED) microscope based only on the modulation of the STED intensity during the acquisition of a STED image. This modulation induces spatially encoded variations of the fluorescence emission that can be visualized in the phasor plot and used to improve and quantify the effective spatial resolution of the STED image. We show that the method can be used to remove direct excitation by the STED beam and perform dual color imaging. We apply this method to the visualization of transcription and replication foci within intact nuclei of eukaryotic cells.
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Affiliation(s)
- Maria J Sarmento
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy
- Department of Biophysical Chemistry, J. Heyrovský Institute of Physical Chemistry of the A.S.C.R. v.v.i., Prague, Czech Republic
| | - Michele Oneto
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy
| | - Simone Pelicci
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy
- Department of Physics, University of Genoa, via Dodecaneso 33, 16146, Genoa, Italy
| | - Luca Pesce
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy
- Department of Physics, University of Genoa, via Dodecaneso 33, 16146, Genoa, Italy
| | - Lorenzo Scipioni
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy
| | - Mario Faretta
- Department of Experimental Oncology, European Institute of Oncology, Via Adamello 16, 20139, Milan, Italy
| | - Laura Furia
- Department of Experimental Oncology, European Institute of Oncology, Via Adamello 16, 20139, Milan, Italy
| | - Gaetano Ivan Dellino
- Department of Experimental Oncology, European Institute of Oncology, Via Adamello 16, 20139, Milan, Italy
- Department of Oncology and Hemato-Oncology, University of Milan, Via Santa Sofia 9, 20142, Milan, Italy
| | - Pier Giuseppe Pelicci
- Department of Experimental Oncology, European Institute of Oncology, Via Adamello 16, 20139, Milan, Italy
- Department of Oncology and Hemato-Oncology, University of Milan, Via Santa Sofia 9, 20142, Milan, Italy
| | - Paolo Bianchini
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy
| | - Alberto Diaspro
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy.
- Department of Physics, University of Genoa, via Dodecaneso 33, 16146, Genoa, Italy.
| | - Luca Lanzanò
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy.
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35
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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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36
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Wang R, Brustlein S, Mailfert S, Fabre R, Fallet M, Sivankutty S, Rigneault H, Marguet D. A straightforward STED-background corrected fitting model for unbiased STED-FCS analyses. Methods 2018; 140-141:212-222. [DOI: 10.1016/j.ymeth.2018.02.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 12/22/2017] [Accepted: 02/09/2018] [Indexed: 11/16/2022] Open
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37
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Sarangi NK, Roobala C, Basu JK. Unraveling complex nanoscale lipid dynamics in simple model biomembranes: Insights from fluorescence correlation spectroscopy in super-resolution stimulated emission depletion mode. Methods 2018; 140-141:198-211. [DOI: 10.1016/j.ymeth.2017.11.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 11/18/2017] [Accepted: 11/19/2017] [Indexed: 12/24/2022] Open
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38
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Ghosh A, Karedla N, Thiele JC, Gregor I, Enderlein J. Fluorescence lifetime correlation spectroscopy: Basics and applications. Methods 2018; 140-141:32-39. [DOI: 10.1016/j.ymeth.2018.02.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 02/09/2018] [Accepted: 02/10/2018] [Indexed: 10/18/2022] Open
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39
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Scipioni L, Di Bona M, Vicidomini G, Diaspro A, Lanzanò L. Local raster image correlation spectroscopy generates high-resolution intracellular diffusion maps. Commun Biol 2018; 1:10. [PMID: 30271897 PMCID: PMC6053083 DOI: 10.1038/s42003-017-0010-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 12/15/2017] [Indexed: 01/01/2023] Open
Abstract
Raster image correlation spectroscopy (RICS) is a powerful method for measuring molecular diffusion in live cells directly from images acquired on a laser scanning microscope. However, RICS only provides single average diffusion coefficients from regions with a lateral size on the order of few micrometers, which means that its spatial resolution is mainly limited to the cellular level. Here we introduce the local RICS (L-RICS), an easy-to-use tool that generates high resolution maps of diffusion coefficients from images acquired on a laser scanning microscope. As an application we show diffusion maps of a green fluorescent protein (GFP) within the nucleus and within the nucleolus of live cells at an effective spatial resolution of 500 nm. We find not only that diffusion in the nucleolus is slowed down compared to diffusion in the nucleoplasm, but also that diffusion in the nucleolus is highly heterogeneous. Lorenzo Scipioni et al. present Local Raster Image Correlation Spectroscopy (L-RICS), a method for generating sub-micrometer diffusion maps. They apply L-RICS to GFP in live cells and find that diffusion coefficients differ between the nucleus and nucleolus and are highly heterogeneous within compartments.
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Affiliation(s)
- Lorenzo Scipioni
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy.,Department of Informatics, Bioengineering, Robotics and Systems Engineering, University of Genoa, Via All'Opera Pia, 13, 16145, Genoa, Italy
| | - Melody Di Bona
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy.,Department of Physics, University of Genoa, via Dodecaneso 33, 16146, Genoa, Italy
| | - Giuseppe Vicidomini
- Molecular Microscopy and Spectroscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy
| | - Alberto Diaspro
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy.,Department of Physics, University of Genoa, via Dodecaneso 33, 16146, Genoa, Italy.,Nikon Imaging Center, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy
| | - Luca Lanzanò
- Nanoscopy, Nanophysics, Istituto Italiano di Tecnologia, via Morego 30, 16163, Genoa, Italy.
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40
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Vicidomini G, Bianchini P, Diaspro A. STED super-resolved microscopy. Nat Methods 2018; 15:173-182. [DOI: 10.1038/nmeth.4593] [Citation(s) in RCA: 295] [Impact Index Per Article: 49.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 08/23/2017] [Indexed: 12/18/2022]
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41
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Komis G, Novák D, Ovečka M, Šamajová O, Šamaj J. Advances in Imaging Plant Cell Dynamics. PLANT PHYSIOLOGY 2018; 176:80-93. [PMID: 29167354 PMCID: PMC5761809 DOI: 10.1104/pp.17.00962] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 11/20/2017] [Indexed: 05/20/2023]
Abstract
Advanced bioimaging uncovers insights into subcellular structures of plants.
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Affiliation(s)
- George Komis
- Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University Olomouc, 783 71 Olomouc, Czech Republic
| | - Dominik Novák
- Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University Olomouc, 783 71 Olomouc, Czech Republic
| | - Miroslav Ovečka
- Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University Olomouc, 783 71 Olomouc, Czech Republic
| | - Olga Šamajová
- Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University Olomouc, 783 71 Olomouc, Czech Republic
| | - Jozef Šamaj
- Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University Olomouc, 783 71 Olomouc, Czech Republic
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42
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Su D, Huang X, Dong C, Ren J. Quantitative Determination of Telomerase Activity by Combining Fluorescence Correlation Spectroscopy with Telomerase Repeat Amplification Protocol. Anal Chem 2017; 90:1006-1013. [PMID: 29211436 DOI: 10.1021/acs.analchem.7b04256] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Telomerase is a key enzyme for maintaining the telomere length and is regarded as a versatile cancer biomarker and a potential drug target due to its important role in cancer and aging. It is necessary to develop a sensitive and reliable method for detection of telomerase activity due to its very low level in cells. In this Article, we propose an ultrasensitive and robust method for quantitative determination of telomerase activity by combining single molecule fluorescence correlation spectroscopy (FCS) with telomerase repeat amplification protocol (TRAP). The principle of this new method (FCS-TRAP) is based on measurement of the change in characteristic diffusion time and molecule number of TRAP products by FCS. The characteristic diffusion time is related to the length of TRAP products, and the molecule number represents the concentration of TRAP products. We optimized the conditions of TRAP procedure and FCS measurements. We observed that the telomerase activities are positively correlated to characteristic diffusion time and molecule number of TRAP products at optimal conditions. This method was successfully used for determination of telomerase activity of different cells, and detection of a single cell was realized. Meanwhile, this method was used to evaluate the inhibition efficiency of inhibitors, and the IC50 values obtained were in good agreement with the references. Compared to current TRAP methods, this method shows reliable quantification, ultrahigh sensitivity, and short detection time and is without separation. We believe that the FCS-TRAP method has a potential application in clinical diagnosis and screening of telomerase inhibitors.
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Affiliation(s)
- Di Su
- School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai, 200240, P. R. China
| | - Xiangyi Huang
- School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai, 200240, P. R. China
| | - Chaoqing Dong
- School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai, 200240, P. R. China
| | - Jicun Ren
- School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai, 200240, P. R. China
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43
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Zhang X, Sisamakis E, Sozanski K, Holyst R. Nanoscopic Approach to Quantification of Equilibrium and Rate Constants of Complex Formation at Single-Molecule Level. J Phys Chem Lett 2017; 8:5785-5791. [PMID: 29131951 DOI: 10.1021/acs.jpclett.7b02742] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Equilibrium and rate constants are key descriptors of complex-formation processes in a variety of chemical and biological reactions. However, these parameters are difficult to quantify, especially in the locally confined, heterogeneous, and dynamically changing living matter. Herein, we address this challenge by combining stimulated emission depletion (STED) nanoscopy with fluorescence correlation spectroscopy (FCS). STED reduces the length-scale of observation to tens of nanometres (2D)/attoliters (3D) and the time-scale to microseconds, with direct, gradual control. This allows one to distinguish diffusional and binding processes of complex-formation, even at reaction rates higher by an order of magnitude than in confocal FCS. We provide analytical autocorrelation formulas for probes undergoing diffusion-reaction processes under STED condition. We support the theoretical analysis of experimental STED-FCS data on a model system of dye-micelle, where we retrieve the equilibrium and rates constants. Our work paves a promising way toward quantitative characterization of molecular interactions in vivo.
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Affiliation(s)
- Xuzhu Zhang
- Department of Soft Condensed Matter, Institute of Physical Chemistry, Polish Academy of Sciences , 01-224 Warsaw, Poland
| | | | - Krzysztof Sozanski
- Department of Soft Condensed Matter, Institute of Physical Chemistry, Polish Academy of Sciences , 01-224 Warsaw, Poland
| | - Robert Holyst
- Department of Soft Condensed Matter, Institute of Physical Chemistry, Polish Academy of Sciences , 01-224 Warsaw, Poland
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