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Chang B, Chen J, Bao J, Sun T, Cheng Z. Molecularly Engineered Room-Temperature Phosphorescence for Biomedical Application: From the Visible toward Second Near-Infrared Window. Chem Rev 2023; 123:13966-14037. [PMID: 37991875 DOI: 10.1021/acs.chemrev.3c00401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2023]
Abstract
Phosphorescence, characterized by luminescent lifetimes significantly longer than that of biological autofluorescence under ambient environment, is of great value for biomedical applications. Academic evidence of fluorescence imaging indicates that virtually all imaging metrics (sensitivity, resolution, and penetration depths) are improved when progressing into longer wavelength regions, especially the recently reported second near-infrared (NIR-II, 1000-1700 nm) window. Although the emission wavelength of probes does matter, it is not clear whether the guideline of "the longer the wavelength, the better the imaging effect" is still suitable for developing phosphorescent probes. For tissue-specific bioimaging, long-lived probes, even if they emit visible phosphorescence, enable accurate visualization of large deep tissues. For studies dealing with bioimaging of tiny biological architectures or dynamic physiopathological activities, the prerequisite is rigorous planning of long-wavelength phosphorescence, being aware of the cooperative contribution of long wavelengths and long lifetimes for improving the spatiotemporal resolution, penetration depth, and sensitivity of bioimaging. In this Review, emerging molecular engineering methods of room-temperature phosphorescence are discussed through the lens of photophysical mechanisms. We highlight the roles of phosphorescence with emission from visible to NIR-II windows toward bioapplications. To appreciate such advances, challenges and prospects in rapidly growing studies of room-temperature phosphorescence are described.
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Affiliation(s)
- Baisong Chang
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, Hubei 430070, China
| | - Jie Chen
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, Hubei 430070, China
| | - Jiasheng Bao
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, Hubei 430070, China
| | - Taolei Sun
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, Hubei 430070, China
| | - Zhen Cheng
- State Key Laboratory of Drug Research, Molecular Imaging Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
- Shandong Laboratory of Yantai Drug Discovery, Bohai Rim Advanced Research Institute for Drug Discovery, Yantai, Shandong 264000, China
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2
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Yahav G, Pawar S, Lipovsky A, Gupta A, Gedanken A, Duadi H, Fixler D. Probing Polarity and pH Sensitivity of Carbon Dots in Escherichia coli through Time-Resolved Fluorescence Analyses. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2068. [PMID: 37513079 PMCID: PMC10384995 DOI: 10.3390/nano13142068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 07/09/2023] [Accepted: 07/12/2023] [Indexed: 07/30/2023]
Abstract
Intracellular monitoring of pH and polarity is crucial for understanding cellular processes and functions. This study employed pH- and polarity-sensitive nanomaterials such as carbon dots (CDs) for the intracellular sensing of pH, polarity, and viscosity using integrated time-resolved fluorescence anisotropy (FA) imaging (TR-FAIM) and fluorescence lifetime (FLT) imaging microscopy (FLIM), thereby enabling comprehensive characterization. The functional groups on the surface of CDs exhibit sensitivity to changes in the microenvironment, leading to variations in fluorescence intensity (FI) and FLT according to pH and polarity. The FLT of CDs in aqueous solution changed gradually from 6.38 ± 0.05 ns to 8.03 ± 0.21 ns within a pH range of 2-8. Interestingly, a complex relationship of FI and FLT was observed during measurements of CDs with decreasing polarity. However, the FA and rotational correlation time (θ) increased from 0.062 ± 0.019 to 0.112 ± 0.023 and from 0.49 ± 0.03 ns to 2.01 ± 0.27 ns, respectively. This increase in FA and θ was attributed to the higher viscosity accompanying the decrease in polarity. Furthermore, CDs were found to bind to three locations in Escherichia coli: the cell wall, inner membrane, and cytoplasm, enabling intracellular characterization using FI and FA decay imaging. FLT provided insights into cytoplasmic pH (7.67 ± 0.48), which agreed with previous works, as well as the decrease in polarity in the cell wall and inner membrane. The CD aggregation was suspected in certain areas based on FA, and the θ provided information on cytoplasmic heterogeneity due to the aggregation and/or interactions with biomolecules. The combined TR-FAIM/FLIM system allowed for simultaneous monitoring of pH and polarity changes through FLIM and viscosity variations through TR-FAIM.
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Affiliation(s)
- Gilad Yahav
- Institute of Nanotechnology and Advanced Materials, Faculty of Engineering, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Shweta Pawar
- Institute of Nanotechnology and Advanced Materials, Faculty of Engineering, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Anat Lipovsky
- Institute of Nanotechnology and Advanced Materials, Faculty of Engineering, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Akanksha Gupta
- Institute of Nanotechnology and Advanced Materials, Department of Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Aharon Gedanken
- Institute of Nanotechnology and Advanced Materials, Department of Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Hamootal Duadi
- Institute of Nanotechnology and Advanced Materials, Faculty of Engineering, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Dror Fixler
- Institute of Nanotechnology and Advanced Materials, Faculty of Engineering, Bar-Ilan University, Ramat Gan 52900, Israel
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3
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van Zanten TS, S GP, Mayor S. Quantitative fluorescence emission anisotropy microscopy for implementing homo-fluorescence resonance energy transfer measurements in living cells. Mol Biol Cell 2023; 34:tp1. [PMID: 37144969 DOI: 10.1091/mbc.e22-09-0446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023] Open
Abstract
Quantitative fluorescence emission anisotropy microscopy reveals the organization of fluorescently labeled cellular components and allows their characterization in terms of changes in either rotational diffusion or homo-Förster's energy transfer characteristics in living cells. These properties provide insights into molecular organization, such as orientation, confinement, and oligomerization in situ. Here we elucidate how quantitative measurements of anisotropy using multiple microscope systems may be made by bringing out the main parameters that influence the quantification of fluorescence emission anisotropy. We focus on a variety of parameters that contribute to errors associated with the measurement of emission anisotropy in a microscope. These include the requirement for adequate photon counts for the necessary discrimination of anisotropy values, the influence of extinction ratios of the illumination source, the detector system, the role of numerical aperture, and excitation wavelength. All these parameters also affect the ability to capture the dynamic range of emission anisotropy necessary for quantifying its reduction due to homo-FRET and other processes. Finally, we provide easily implementable tests to assess whether homo-FRET is a cause for the observed emission depolarization.
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Affiliation(s)
- Thomas S van Zanten
- Cell Biology Group, National Centre for Biological Sciences, UAS-GKVK Campus, Tata Institute for Fundamental Research, Bangalore 560065, India
| | - Greeshma Pradeep S
- Cell Biology Group, National Centre for Biological Sciences, UAS-GKVK Campus, Tata Institute for Fundamental Research, Bangalore 560065, India
| | - Satyajit Mayor
- Cell Biology Group, National Centre for Biological Sciences, UAS-GKVK Campus, Tata Institute for Fundamental Research, Bangalore 560065, India
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4
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Molines AT, Lemière J, Gazzola M, Steinmark IE, Edrington CH, Hsu CT, Real-Calderon P, Suhling K, Goshima G, Holt LJ, Thery M, Brouhard GJ, Chang F. Physical properties of the cytoplasm modulate the rates of microtubule polymerization and depolymerization. Dev Cell 2022; 57:466-479.e6. [PMID: 35231427 PMCID: PMC9319896 DOI: 10.1016/j.devcel.2022.02.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 11/01/2021] [Accepted: 01/31/2022] [Indexed: 11/20/2022]
Abstract
The cytoplasm is a crowded, visco-elastic environment whose physical properties change according to physiological or developmental states. How the physical properties of the cytoplasm impact cellular functions in vivo remains poorly understood. Here, we probe the effects of cytoplasmic concentration on microtubules by applying osmotic shifts to fission yeast, moss, and mammalian cells. We show that the rates of both microtubule polymerization and depolymerization scale linearly and inversely with cytoplasmic concentration; an increase in cytoplasmic concentration decreases the rates of microtubule polymerization and depolymerization proportionally, whereas a decrease in cytoplasmic concentration leads to the opposite. Numerous lines of evidence indicate that these effects are due to changes in cytoplasmic viscosity rather than cellular stress responses or macromolecular crowding per se. We reconstituted these effects on microtubules in vitro by tuning viscosity. Our findings indicate that, even in normal conditions, the viscosity of the cytoplasm modulates the reactions that underlie microtubule dynamic behaviors.
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Affiliation(s)
- Arthur T Molines
- Department of Cell and Tissue Biology, University of California, San Francisco, USA; Marine Biological Laboratory, Woods Hole, MA 02543, USA.
| | - Joël Lemière
- Department of Cell and Tissue Biology, University of California, San Francisco, USA
| | - Morgan Gazzola
- University of Grenoble-Alpes, CEA, CNRS, INRA, Interdisciplinary Research Institute of Grenoble, Laboratoire de Phyiologie Cellulaire & Vegétale, CytoMorpho Lab, 38054 Grenoble, France
| | | | | | - Chieh-Ting Hsu
- Department of Physics, McGill University, Montréal, Quebec, Canada
| | - Paula Real-Calderon
- Department of Cell and Tissue Biology, University of California, San Francisco, USA
| | - Klaus Suhling
- Department of Physics, King's College London, London, UK
| | - Gohta Goshima
- Sugashima Marine Biological Laboratory and Division of Biological Science, Graduate School of Science, Nagoya University, Toba City, Mie, Japan; Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Liam J Holt
- Institute for Systems Genetics, New York University Langone Health, New York, NY 10016, USA; Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Manuel Thery
- University of Grenoble-Alpes, CEA, CNRS, INRA, Interdisciplinary Research Institute of Grenoble, Laboratoire de Phyiologie Cellulaire & Vegétale, CytoMorpho Lab, 38054 Grenoble, France; Université de Paris, INSERM, CEA, Institut de Recherche Saint Louis, U 976, CytoMorpho Lab, 75010 Paris, France
| | - Gary J Brouhard
- Department of Biology, McGill University, Montréal, Quebec, Canada
| | - Fred Chang
- Department of Cell and Tissue Biology, University of California, San Francisco, USA; Marine Biological Laboratory, Woods Hole, MA 02543, USA.
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Yahav G, Weber Y, Duadi H, Pawar S, Fixler D. Classification of fluorescent anisotropy decay based on the distance approach in the frequency domain. OPTICS EXPRESS 2022; 30:6176-6192. [PMID: 35209559 DOI: 10.1364/oe.453108] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 02/01/2022] [Indexed: 06/14/2023]
Abstract
Frequency-domain (FD) fluorometry is a widely utilized tool to probe unique features of complex biological structures, which may serve medical diagnostic purposes. The conventional data analysis approaches used today to extract the fluorescence intensity or fluorescence anisotropy (FA) decay data suffer from several drawbacks and are inherently limited by the characteristics and complexity of the decay models. This paper presents the squared distance (D2) technique, which categorized samples based on the direct frequency response data (FRD) of the FA decay. As such, it improves the classification ability of the FD measurements of the FA decay as it avoids any distortion that results from the challenged translation into time domain data. This paper discusses the potential use of the D2 approach to classify biological systems. Mathematical formulation of D2 technique adjusted to the FRD of the FA decay is described. In addition, it validates the D2 approach using 2 simulated data sets of 6 groups with similar widely and closely spaced FA decay data as well as in experimental data of 4 samples of a fluorophore-solvent (fluorescein-glycerol) system. In the simulations, the classification accuracy was above 95% for all 6 groups. In the experimental data, the classification accuracy was 100%. The D2 approach can help classify samples whose FA decay data are difficult to extract making FA in the FD a realistic diagnostic tool. The D2 approach offers an advanced method for sorting biological samples with differences beyond the practical temporal resolution limit in a reliable and efficient manner based on the FRD of their time-resolved fluorescence measurements thereby achieving better diagnostic quality in a shorter time.
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6
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Pulin M, Stockhausen KE, Masseck OA, Kubitschke M, Busse B, Wiegert JS, Oertner TG. Orthogonally-polarized excitation for improved two-photon and second-harmonic-generation microscopy, applied to neurotransmitter imaging with GPCR-based sensors. BIOMEDICAL OPTICS EXPRESS 2022; 13:777-790. [PMID: 35284188 PMCID: PMC8884218 DOI: 10.1364/boe.448760] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 01/06/2022] [Accepted: 01/06/2022] [Indexed: 06/14/2023]
Abstract
Fluorescent proteins are excited by light that is polarized parallel to the dipole axis of the chromophore. In two-photon microscopy, polarized light is used for excitation. Here we reveal surprisingly strong polarization sensitivity in a class of genetically encoded, GPCR-based neurotransmitter sensors. In tubular structures such as dendrites, this effect led to a complete loss of membrane signal in dendrites running parallel to the polarization direction of the excitation beam. To reduce the sensitivity to dendritic orientation, we designed an optical device that generates interleaved pulse trains of orthogonal polarization. The passive device, which we inserted in the beam path of an existing two-photon microscope, removed the strong direction bias from fluorescence and second-harmonic (SHG) images. We conclude that for optical measurements of transmitter concentration with GPCR-based sensors, orthogonally polarized excitation is essential.
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Affiliation(s)
- Mauro Pulin
- Institute for Synaptic Physiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
- Research Group Synaptic Wiring and Information Processing, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Kilian E. Stockhausen
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, 22529 Hamburg, Germany
| | - Olivia A. Masseck
- Synthetic Biology, University of Bremen, Leobener Str. 5, 28359 Bremen, Germany
| | - Martin Kubitschke
- Synthetic Biology, University of Bremen, Leobener Str. 5, 28359 Bremen, Germany
| | - Björn Busse
- Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, 22529 Hamburg, Germany
- Interdisciplinary Competence Center for Interface Research (ICCIR), University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - J. Simon Wiegert
- Research Group Synaptic Wiring and Information Processing, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Thomas G. Oertner
- Institute for Synaptic Physiology, ZMNH, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
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7
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Fluorophore spectroscopy in aqueous glycerol solution: the interactions of glycerol with the fluorophore. Photochem Photobiol Sci 2021; 20:1397-1418. [PMID: 34609728 DOI: 10.1007/s43630-021-00096-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 08/24/2021] [Indexed: 10/20/2022]
Abstract
A common perception exists that glycerol provides an inert-like environment modifying viscosity and index of refraction by its various concentrations in aqueous solution. Said perception is herein challenged by investigating the effects of the glycerol environment on the spectroscopic properties of fluorescein, as a representative fluorophore, using steady-state and time-resolved techniques and computational chemistry. Results strongly suggest that the fluorescence quantum yield, measured fluorescence lifetime (FLT), natural lifetime and calculated fluorescence lifetime are all highly sensitive to the presence of glycerol. Glycerol was found to impact both the ground and first excited states of fluorescein, quenching and modifying both absorption and emission spectra, affecting the fundamental electrical dipoles of the ground and first excited singlet states, and lowering FLT and quantum yield. Furthermore, the Stern-Volmer, Lippert-Mataga, Perrin and Strickler-Berg relations indicate that glycerol acts upon fluorescein in aqueous solution as a quencher and alters the fluorescein geometry. Predictions made by computational chemistry impressively correspond to experimental results, both indicating changes in the properties of fluorescein at around 35% v/v aqueous glycerol, a clear indication that glycerol is not an innocent medium. This study proposes the Strickler-Berg relation as a means of detecting non-negligible effects of a hosting medium on its host fluorophore. These new insights on the molecular structures, the interactions between glycerol and its host fluorophore, and the effects of one on the other may be essential for understanding fundamental phenomena in chemistry and related fields.
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8
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Shepherd JW, Payne-Dwyer AL, Lee JE, Syeda A, Leake MC. Combining single-molecule super-resolved localization microscopy with fluorescence polarization imaging to study cellular processes. JPHYS PHOTONICS 2021. [DOI: 10.1088/2515-7647/ac015d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Super-resolution microscopy has catalyzed valuable insights into the sub-cellular, mechanistic details of many different biological processes across a wide range of cell types. Fluorescence polarization spectroscopy tools have also enabled important insights into cellular processes through identifying orientational changes of biological molecules typically at an ensemble level. Here, we combine these two biophysical methodologies in a single home-made instrument to enable the simultaneous detection of orthogonal fluorescence polarization signals from single fluorescent protein molecules used as common reporters on the localization of proteins in cellular processes. These enable measurement of spatial location to a super-resolved precision better than the diffraction-limited optical resolution, as well as estimation of molecular stoichiometry based on the brightness of individual fluorophores. In this innovation we have adapted a millisecond timescale microscope used for single-molecule detection to enable splitting of fluorescence polarization emissions into two separate imaging channels for s- and p-polarization signals, which are imaged onto separate halves of the same high sensitivity back-illuminated CMOS camera detector. We applied this fluorescence polarization super-resolved imaging modality to a range of test fluorescent samples relevant to the study of biological processes, including purified monomeric green fluorescent protein, single combed DNA molecules, and protein assemblies and complexes from live Escherichia coli and Saccharomyces cerevisiae cells. Our findings are qualitative but demonstrate promise in showing how fluorescence polarization and super-resolved localization microscopy can be combined on the same sample to enable simultaneous measurements of polarization and stoichiometry of tracked molecular complexes, as well as the translational diffusion coefficient.
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Time-Resolved Fluorescence Anisotropy and Molecular Dynamics Analysis of a Novel GFP Homo-FRET Dimer. Biophys J 2020; 120:254-269. [PMID: 33345902 PMCID: PMC7840444 DOI: 10.1016/j.bpj.2020.11.2275] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 11/06/2020] [Accepted: 11/23/2020] [Indexed: 02/07/2023] Open
Abstract
Förster resonance energy transfer (FRET) is a powerful tool to investigate the interaction between proteins in living cells. Fluorescence proteins, such as the green fluorescent protein (GFP) and its derivatives, are coexpressed in cells linked to proteins of interest. Time-resolved fluorescence anisotropy is a popular tool to study homo-FRET of fluorescent proteins as an indicator of dimerization, in which its signature consists of a very short component at the beginning of the anisotropy decay. In this work, we present an approach to study GFP homo-FRET via a combination of time-resolved fluorescence anisotropy, the stretched exponential decay model, and molecular dynamics simulations. We characterize a new, to our knowledge, FRET standard formed by two enhanced GFPs (eGFPs) and a flexible linker of 15 aminoacids (eGFP15eGFP) with this protocol, which is validated by using an eGFP monomer as a reference. An excellent agreement is found between the FRET efficiency calculated from the fit of the eGFP15eGFP fluorescence anisotropy decays with a stretched exponential decay model (〈EFRETexp〉 = 0.25 ± 0.05) and those calculated from the molecular dynamics simulations (〈EFRETMD〉 = 0.18 ± 0.14). The relative dipole orientation between the GFPs is best described by the orientation factors 〈κ2〉 = 0.17 ± 0.16 and 〈|κ|〉 = 0.35 ± 0.20, contextualized within a static framework in which the linker hinders the free rotation of the fluorophores and excludes certain configurations. The combination of time- and polarization-resolved fluorescence spectroscopy with molecular dynamics simulations is shown to be a powerful tool for the study and interpretation of homo-FRET.
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Agarwal A, Das D, Banerjee T, Mukhopadhyay S. Energy migration captures membrane-induced oligomerization of the prion protein. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2020; 1868:140324. [DOI: 10.1016/j.bbapap.2019.140324] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 10/23/2019] [Accepted: 10/26/2019] [Indexed: 12/22/2022]
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Kozer N, Clayton AHA. In-cell structural dynamics of an EGF receptor during ligand-induced dimer-oligomer transition. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2019; 49:21-37. [PMID: 31740999 DOI: 10.1007/s00249-019-01410-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 10/24/2019] [Accepted: 11/07/2019] [Indexed: 10/25/2022]
Abstract
The epidermal growth factor receptor (EGFR) is a membrane protein that regulates cell proliferation, differentiation and survival, and is a drug target for cancer therapy. Ligand-induced activation of the EGFR kinase is generally regarded to require ligand-bound-dimers, while phosphorylation and down-stream signalling is modulated by oligomers. Recent work has unveiled changes in EGFR dynamics from ligand-induced dimerization in membranes extracted from cells, however, less is known about the changes in EGFR dynamics that accompany the ligand-induced oligomerization in a live cell environment. Here, we determine the dynamics of a c-terminal GFP tag attached to EGFR in the unliganded dimer and in the liganded oligomers. By means of the single-frequency polarized phasor ellipse approach we extracted two correlation times on the sub-nanosecond and super-nanosecond timescales, respectively. EGF binding to the EGFR-GFP dimer lengthened the sub-nanosecond correlation time (from 0.1 to 1.3 ns) and shortened the super-nanosecond correlation time (from 210 to 56 ns) of the c-terminal GFP probe. The sub-nanosecond depolarization processes were assigned to electronic energy migration between proximal GFPs in the EGFR dimer or oligomer, while the super-nanosecond correlation times were assigned to nanosecond fluctuations of the GFP probe in the EGFR complex. Accordingly, these results show that ligand binding increased the average separation between the c-terminal tags and increased their rotational mobility. We propose that the dynamics are linked to an inhibitory function of the c-terminal tail in the un-liganded dimer and to the requirement of facile stochastic switching between kinase activation and cytoplasmic adaptor/effector binding in the active oligomers.
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Affiliation(s)
- Noga Kozer
- Cell Biophysics Laboratory, Department of Physics and Astronomy, Faculty of Science, Engineering and Technology, Centre for Micro-Photonics, School of Science, Swinburne University of Technology, Melbourne, Australia
| | - Andrew H A Clayton
- Cell Biophysics Laboratory, Department of Physics and Astronomy, Faculty of Science, Engineering and Technology, Centre for Micro-Photonics, School of Science, Swinburne University of Technology, Melbourne, Australia.
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Vinegoni C, Feruglio PF, Gryczynski I, Mazitschek R, Weissleder R. Fluorescence anisotropy imaging in drug discovery. Adv Drug Deliv Rev 2019; 151-152:262-288. [PMID: 29410158 PMCID: PMC6072632 DOI: 10.1016/j.addr.2018.01.019] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 01/29/2018] [Accepted: 01/30/2018] [Indexed: 12/15/2022]
Abstract
Non-invasive measurement of drug-target engagement can provide critical insights in the molecular pharmacology of small molecule drugs. Fluorescence polarization/fluorescence anisotropy measurements are commonly employed in protein/cell screening assays. However, the expansion of such measurements to the in vivo setting has proven difficult until recently. With the advent of high-resolution fluorescence anisotropy microscopy it is now possible to perform kinetic measurements of intracellular drug distribution and target engagement in commonly used mouse models. In this review we discuss the background, current advances and future perspectives in intravital fluorescence anisotropy measurements to derive pharmacokinetic and pharmacodynamic measurements in single cells and whole organs.
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Affiliation(s)
- Claudio Vinegoni
- Center for System Biology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
| | - Paolo Fumene Feruglio
- Center for System Biology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA; Department of Neurological, Biomedical and Movement Sciences, University of Verona, Verona, Italy
| | - Ignacy Gryczynski
- University of North Texas Health Science Center, Institute for Molecular Medicine, Fort Worth, TX, United States
| | - Ralph Mazitschek
- Center for System Biology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Ralph Weissleder
- Center for System Biology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
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Althumairy D, Murakami HA, Zhang D, Barisas BG, Roess DA, Crans DC. Effects of vanadium(IV) compounds on plasma membrane lipids lead to G protein-coupled receptor signal transduction. J Inorg Biochem 2019; 203:110873. [PMID: 31706224 DOI: 10.1016/j.jinorgbio.2019.110873] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 09/27/2019] [Accepted: 09/27/2019] [Indexed: 10/25/2022]
Abstract
Luteinizing hormone receptors (LHR), expressed at physiological numbers <30,000 receptors per cell, translocate to and signal within membrane rafts following binding of human chorionic gonadotropin (hCG). Similarly LHR signal in cells when treated with bis(maltolato)oxovanadium(IV) (BMOV), bis(ethylmaltolato)oxovanadium(IV) (BEOV) or VOSO4, which decrease membrane lipid packing. Overexpressed LHR (>85,000 receptors per cell) are found in larger clusters in polarized homo-transfer fluorescence resonance energy transfer (homo-FRET) studies that were not affected by either hCG or vanadium compounds. Intracellular cyclic adenylate monophosphate (cAMP) levels indicate that only clustered LHR are active and produce the intracellular second messenger, cAMP. When LHR are over-expressed, cell signaling is unaffected by binding of hCG or vanadium compounds. To confirm the existence of intact complex, the EPR spectra of vanadium compounds in cell media were obtained using 1 mM BMOV, BEOV or VOSO4. These data were used to determine intact complex in a 10 μM solution and verified by speciation calculations. Effects of BMOV and BEOV samples were about two-fold greater than those of aqueous vanadium(IV) making it likely that intact vanadium complex are responsible for effects of LHR function. This represents a new mechanism for activation of a G protein-coupled receptor; perturbations in the lipid bilayer by vanadium compounds lead to aggregation and accumulation of physiological numbers of LHR in membrane raft domains where they initiate signal transduction and production of cAMP, a second messenger involved in signaling.
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Affiliation(s)
- Duaa Althumairy
- Cell and Molecular Biology Program, Colorado State University Fort Collins, CO 80523, United States of America; Department of Biological Sciences, King Faisal University, Saudi Arabia
| | - Heide A Murakami
- Department of Chemistry, Colorado State University Fort Collins, CO 80523, United States of America
| | - Dongmei Zhang
- Department of Chemistry, Colorado State University Fort Collins, CO 80523, United States of America
| | - B George Barisas
- Cell and Molecular Biology Program, Colorado State University Fort Collins, CO 80523, United States of America; Department of Chemistry, Colorado State University Fort Collins, CO 80523, United States of America
| | - Deborah A Roess
- Department of Biomedical Sciences, Colorado State University Fort Collins, CO 80523, United States of America
| | - Debbie C Crans
- Cell and Molecular Biology Program, Colorado State University Fort Collins, CO 80523, United States of America; Department of Chemistry, Colorado State University Fort Collins, CO 80523, United States of America.
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14
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Algar WR, Hildebrandt N, Vogel SS, Medintz IL. FRET as a biomolecular research tool — understanding its potential while avoiding pitfalls. Nat Methods 2019; 16:815-829. [DOI: 10.1038/s41592-019-0530-8] [Citation(s) in RCA: 197] [Impact Index Per Article: 39.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 07/15/2019] [Indexed: 01/14/2023]
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15
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Snell NE, Rao VP, Seckinger KM, Liang J, Leser J, Mancini AE, Rizzo MA. Homotransfer of FRET Reporters for Live Cell Imaging. BIOSENSORS-BASEL 2018; 8:bios8040089. [PMID: 30314323 PMCID: PMC6316388 DOI: 10.3390/bios8040089] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 09/27/2018] [Accepted: 10/10/2018] [Indexed: 01/01/2023]
Abstract
Förster resonance energy transfer (FRET) between fluorophores of the same species was recognized in the early to mid-1900s, well before modern heterotransfer applications. Recently, homotransfer FRET principles have re-emerged in biosensors that incorporate genetically encoded fluorescent proteins. Homotransfer offers distinct advantages over the standard heterotransfer FRET method, some of which are related to the use of fluorescence polarization microscopy to quantify FRET between two fluorophores of identical color. These include enhanced signal-to-noise, greater compatibility with other optical sensors and modulators, and new design strategies based upon the clustering or dimerization of singly-labeled sensors. Here, we discuss the theoretical basis for measuring homotransfer using polarization microscopy, procedures for data collection and processing, and we review the existing genetically-encoded homotransfer biosensors.
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Affiliation(s)
- Nicole E Snell
- Department of Physiology, University of Maryland School of Medicine, 660 W Redwood St/HH525B, Baltimore, MD 21201, USA.
| | - Vishnu P Rao
- Department of Physiology, University of Maryland School of Medicine, 660 W Redwood St/HH525B, Baltimore, MD 21201, USA.
| | - Kendra M Seckinger
- Department of Physiology, University of Maryland School of Medicine, 660 W Redwood St/HH525B, Baltimore, MD 21201, USA.
| | - Junyi Liang
- Department of Physiology, University of Maryland School of Medicine, 660 W Redwood St/HH525B, Baltimore, MD 21201, USA.
| | - Jenna Leser
- Department of Physiology, University of Maryland School of Medicine, 660 W Redwood St/HH525B, Baltimore, MD 21201, USA.
| | - Allison E Mancini
- Department of Physiology, University of Maryland School of Medicine, 660 W Redwood St/HH525B, Baltimore, MD 21201, USA.
| | - M A Rizzo
- Department of Physiology, University of Maryland School of Medicine, 660 W Redwood St/HH525B, Baltimore, MD 21201, USA.
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16
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Wang L, Chen B, Yan W, Yang Z, Peng X, Lin D, Weng X, Ye T, Qu J. Resolution improvement in STED super-resolution microscopy at low power using a phasor plot approach. NANOSCALE 2018; 10:16252-16260. [PMID: 30124714 DOI: 10.1039/c8nr03584a] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Stimulated emission depletion (STED) microscopy is a powerful super-resolution microscopy technique that has achieved significant results in breaking the resolution limit and relevant applications. In principle, STED super resolution is obtained by stimulated emission partially inhibiting the spontaneous emission in the periphery of a diffraction-limited area. However, very high depletion laser power is generally necessary for the enhancement of imaging resolution, which is harmful to live biological specimens due to its high phototoxicity and photo-bleaching effects. Therefore, further improving the STED resolution at a lower depletion power level has recently attracted increasing interest from researchers in various fields. In this work, a phasor plot approach combined with fluorescence lifetime imaging microscopy (FLIM) is used to resolve the abovementioned problem based on a long- and short-lifetime criterion. Firstly, the time-resolved data obtained by STED-FLIM is converted to the frequency domain via a phasor approach. Next, partial data is extracted according to the information on the phase and amplitude for resolution improvement. Then, fluorescent microspheres (100 nm in diameter) are observed under different depletion powers, resulting in a series of improved resolution through phasor plots. Finally, this method is applied to image human Nup153 in fixed HeLa cells, providing a 86 nm higher resolution than that in traditional STED imaging at a depletion power of 20 mW.
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Affiliation(s)
- Luwei Wang
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
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17
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Masters TA, Robinson NA, Marsh RJ, Blacker TS, Armoogum DA, Larijani B, Bain AJ. Time-resolved stimulated emission depletion and energy transfer dynamics in two-photon excited EGFP. J Chem Phys 2018; 148:134312. [DOI: 10.1063/1.5011643] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- T. A. Masters
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
- CoMPLEX, University College London, London WC1E 6BT, United Kingdom
| | - N. A. Robinson
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - R. J. Marsh
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - T. S. Blacker
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
- CoMPLEX, University College London, London WC1E 6BT, United Kingdom
| | - D. A. Armoogum
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - B. Larijani
- Cell Biophysics Laboratory, Ikerbasque, Basque Foundation for Science and Unidad de Biofisica (CSIC-UPV/EHU), Bilbao, Spain
| | - A. J. Bain
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
- CoMPLEX, University College London, London WC1E 6BT, United Kingdom
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18
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Le Marois A, Suhling K. Quantitative Live Cell FLIM Imaging in Three Dimensions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1035:31-48. [PMID: 29080129 DOI: 10.1007/978-3-319-67358-5_3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
In this chapter, the concept of fluorescence lifetime and its utility in quantitative live cell imaging will be introduced, along with methods to record and analyze FLIM data. Relevant applications in 3D tissue and live cell imaging, including multiplexed FLIM detection, will also be detailed.
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Affiliation(s)
- Alix Le Marois
- Department of Physics, King's College London, Strand, London, WC2R 2LS, UK
| | - Klaus Suhling
- Department of Physics, King's College London, Strand, London, WC2R 2LS, UK.
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19
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Fluorescence Anisotropy to Detect In Vivo Stimulus-Induced Changes in Chemoreceptor Packing. Methods Mol Biol 2018. [PMID: 29429096 DOI: 10.1007/978-1-4939-7577-8_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
The anisotropy of the fluorescence emitted from fluorescent proteins, such as yellow fluorescent protein (YFP), is sensitive to Homo-FRET between the proteins. This effect can be used to detect in vivo ligand-induced changes in packing or conformation of tagged chemoreceptors. Such measurements of clustered or dispersed core-signaling units revealed quantitative dose-dependent responses of these sensors.
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20
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Bene L, Gralle M, Damjanovich L. Confocal microscopic dual-laser dual-polarization FRET (2polFRET) at the acceptor side for correlating rotations at different distances on the cell surface. Biochim Biophys Acta Gen Subj 2018; 1862:1050-1068. [PMID: 29292190 DOI: 10.1016/j.bbagen.2017.12.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 12/16/2017] [Accepted: 12/22/2017] [Indexed: 10/18/2022]
Abstract
Relationship of donor and acceptor fluorescence anisotropies as well as efficiency of fluorescence resonance energy transfer (FRET) has been investigated in a confocal microscope in the context of FRET systems comprised of donor and acceptor-labeled MHCI and MHCII receptors on the surface of Kit-225 K6 human T-cells. The measurements have been carried out in a 2-laser, 5-signal platform where the total donor fluorescence intensity and 2 acceptor fluorescence intensities with their anisotropies - one at the donor's excitation wavelength, the other at the acceptor's excitation wavelength - have been detected. This configuration enabled the determination of FRET efficiency and correlating it with the two acceptor fluorescence anisotropies as a kind of calibration. Estimations for the FRET-enhanced donor fluorescence anisotropy, the directly excited acceptor fluorescence anisotropy, and the fluorescence anisotropy of sensitized emission have been obtained. Procedures for determining FRET by measuring only the total donor intensity and the acceptor intensity and its anisotropy, or two acceptor intensities and their anisotropies have been elaborated, the errors of which have been estimated based on the fluorescence anisotropy values obtained in the calibration with the method of flow cytometric energy transfer (FCET). The combined detection of the donor and acceptor fluorescence anisotropies enabled also the determination of the lower and upper limits of the orientation factor for FRET (κ2). An increase in range for κ2 with increasing FRET efficiency has been observed, with average κ2 values different from the dynamic random average of 2/3. These observations call for the need of κ2 determination in proximity measurements, where the donor and acceptor orientations are not predictable. An increasing range of κ2 with increasing intermolecular proximity of the MHCI and MHCII receptors has been observed. This indicates that molecular flexibility in the clusters of the MHCI and MHCII receptors reduces with increasing cluster density, i.e. a "fluidity gradient" exists in the clusters. More specifically, the local density dependent flexibility can also be taken as a direct proof for that the association of these receptors is non-random, but mediated by some type of physical interaction, a finding as a benefit of FRET detection by polarization spectroscopy. Two new quantities - the quenched donor fluorescence anisotropy and a fluorescence anisotropy analogue, the "dissymmetry index" of the polarized FRET efficiency components - have also been introduced for the characterization of the orientational dynamics of the excited state during FRET.
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Affiliation(s)
- László Bene
- Department of Surgery, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
| | - Matthias Gralle
- Departamento de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - László Damjanovich
- Department of Surgery, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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21
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Peulen TO, Opanasyuk O, Seidel CAM. Combining Graphical and Analytical Methods with Molecular Simulations To Analyze Time-Resolved FRET Measurements of Labeled Macromolecules Accurately. J Phys Chem B 2017; 121:8211-8241. [PMID: 28709377 PMCID: PMC5592652 DOI: 10.1021/acs.jpcb.7b03441] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
![]()
Förster resonance energy transfer
(FRET) measurements from
a donor, D, to an acceptor, A, fluorophore are frequently used in vitro and in live cells to reveal information on the
structure and dynamics of DA labeled macromolecules. Accurate descriptions
of FRET measurements by molecular models are complicated because the
fluorophores are usually coupled to the macromolecule via flexible
long linkers allowing for diffusional exchange between multiple states
with different fluorescence properties caused by distinct environmental
quenching, dye mobilities, and variable DA distances. It is often
assumed for the analysis of fluorescence intensity decays that DA
distances and D quenching are uncorrelated (homogeneous quenching
by FRET) and that the exchange between distinct fluorophore states
is slow (quasistatic). This allows us to introduce the FRET-induced
donor decay, εD(t), a function solely
depending on the species fraction distribution of the rate constants
of energy transfer by FRET, for a convenient joint analysis of fluorescence
decays of FRET and reference samples by integrated graphical and analytical
procedures. Additionally, we developed a simulation toolkit to model
dye diffusion, fluorescence quenching by the protein surface, and
FRET. A benchmark study with simulated fluorescence decays of 500
protein structures demonstrates that the quasistatic homogeneous model
works very well and recovers for single conformations the average
DA distances with an accuracy of < 2%. For more complex
cases, where proteins adopt multiple conformations with significantly
different dye environments (heterogeneous case), we introduce a general
analysis framework and evaluate its power in resolving heterogeneities
in DA distances. The developed fast simulation methods, relying on
Brownian dynamics of a coarse-grained dye in its sterically accessible
volume, allow us to incorporate structural information in the decay
analysis for heterogeneous cases by relating dye states with protein
conformations to pave the way for fluorescence and FRET-based dynamic
structural biology. Finally, we present theories and simulations to
assess the accuracy and precision of steady-state and time-resolved
FRET measurements in resolving DA distances on the single-molecule
and ensemble level and provide a rigorous framework for estimating
approximation, systematic, and statistical errors.
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Affiliation(s)
- Thomas-Otavio Peulen
- Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität , Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Oleg Opanasyuk
- Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität , Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Claus A M Seidel
- Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität , Universitätsstraße 1, 40225 Düsseldorf, Germany
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22
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Panek J, Koziolova E, Stepanek P, Etrych T, Janouskova O. Intracellular fate of polymer therapeutics investigated by fluorescence lifetime imaging and fluorescence pattern analysis. Physiol Res 2017; 65:S217-S224. [PMID: 27762587 DOI: 10.33549/physiolres.933423] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Nanocarriers bearing anticancer drugs are promising candidates to improve the efficacy of cancer therapy and minimize side effects. The most potent cytostatics used in the treatment of various cancers are anthracyclines, e.g. doxorubicin or pirarubicin. Recently, polymer therapeutics carrying anthracyclines have been intensively studied. The precise characterization of in vitro nanocarrier biological behavior brings a better understanding of the nanocarrier characteristics and enables prediction of the behavior of the nanocarrier during in vivo application. Advanced fluorescence detection methods, e.g. fluorescence lifetime imaging microscopy (FLIM), were successfully exploited to describe the properties of various polymeric nano-systems and contributed to a complex view of anthracyclines' intracellular transport and DNA intercalation. Here, we report the application of a specific technique for processing FLIM images, called fluorescence pattern decomposition, to evaluate early events after doxorubicin or pirarubicin treatment of cells. Moreover, we characterized changes in the intracellular localization and release of the anthracyclines during the incubation of cells with polymer nanotherapeutics based on poly[N-(2-hydroxypropyl)-methacrylamide] (pHPMA).
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Affiliation(s)
- J Panek
- Institute of Macromolecular Chemistry of the Czech Academy of Sciences, Prague, Czech Republic.
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23
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Liu HT, Lin WL, Feng YL, Lin Y, Chen YC. Multidie LED combined with homogenizing optics to improve frequency response and intensity for FLIM applications. J Microsc 2017; 266:324-334. [PMID: 28294329 DOI: 10.1111/jmi.12541] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 01/19/2017] [Accepted: 01/25/2017] [Indexed: 11/28/2022]
Abstract
Application of light-emitting diodes (LEDs) in frequency-domain fluorescence lifetime imaging microscopy (FLIM) has been limited by the trade-off between modulation frequency and illumination intensity of LEDs, which affects the signal-to-noise ratio in fluorescence lifetime measurements. To increase modulation frequency without sacrificing output power of LEDs, we propose to use LEDs with multiple dice connected in series. The LED capacitance was reduced with series connection; therefore, the frequency response of multidie LED was significantly increased. LEDs in visible light, including blue, green, amber and red, were all applicable in FLIM. We also present a homogenizing optics design, so that multidie LEDs produced uniform illumination on the same focal spot. When the homogenizing optics was combined with multicolour emitters, it provides multiple colour selection in a compact and convenient design.
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Affiliation(s)
- H-T Liu
- Institute of Imaging and Biomedical Photonics, National Chiao Tung University, Tainan, Taiwan
| | - W-L Lin
- Institute of Imaging and Biomedical Photonics, National Chiao Tung University, Tainan, Taiwan
| | - Y-L Feng
- Institute of Photonic System, National Chiao Tung University, Tainan, Taiwan
| | - Y Lin
- Institute of Imaging and Biomedical Photonics, National Chiao Tung University, Tainan, Taiwan
| | - Y-C Chen
- Institute of Imaging and Biomedical Photonics, National Chiao Tung University, Tainan, Taiwan
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24
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A Guide to Fluorescent Protein FRET Pairs. SENSORS 2016; 16:s16091488. [PMID: 27649177 PMCID: PMC5038762 DOI: 10.3390/s16091488] [Citation(s) in RCA: 244] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 08/23/2016] [Accepted: 08/25/2016] [Indexed: 12/20/2022]
Abstract
Förster or fluorescence resonance energy transfer (FRET) technology and genetically encoded FRET biosensors provide a powerful tool for visualizing signaling molecules in live cells with high spatiotemporal resolution. Fluorescent proteins (FPs) are most commonly used as both donor and acceptor fluorophores in FRET biosensors, especially since FPs are genetically encodable and live-cell compatible. In this review, we will provide an overview of methods to measure FRET changes in biological contexts, discuss the palette of FP FRET pairs developed and their relative strengths and weaknesses, and note important factors to consider when using FPs for FRET studies.
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25
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Zolmajd-Haghighi Z, Hanley QS. WhenR > 0.8R0: fluorescence anisotropy, non-additive intensity, and cluster size. Methods Appl Fluoresc 2016; 4:024006. [DOI: 10.1088/2050-6120/4/2/024006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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26
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Exonuclease III-assisted graphene oxide amplified fluorescence anisotropy strategy for ricin detection. Biosens Bioelectron 2016; 85:822-827. [PMID: 27295569 DOI: 10.1016/j.bios.2016.05.091] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/23/2016] [Accepted: 05/30/2016] [Indexed: 11/23/2022]
Abstract
Graphene oxide (GO) is an excellent fluorescence anisotropy (FA) amplifier. However, in the conventional GO amplified FA strategy, one target can only induce the FA change of one fluorophore on probe, which limits the detection sensitivity. Herein, we developed an exonuclease III (Exo III) aided GO amplified FA strategy by using aptamer as an recognition element and ricin B-chain as a proof-of-concept target. The aptamer was hybridized with a blocker sequence and linked onto the surface of magnetic beads (MBs). Upon the addition of ricin B-chain, blocker was released from the surface of MBs and hybridized with the dye-modified probe DNA on the surface of GO through the toehold-mediated strand exchange reaction. The formed blocker-probe DNA duplex triggered the Exo III-assisted cyclic signal amplification by repeating the hybridization and digestion of probe DNA, liberating the fluorophore with several nucleotides (low FA value). Thus, ricin B-chain could be sensitively detected by the significantly decreased FA. The linear range was from 1.0μg/mL to 13.3μg/mL and the limit of detection (LOD) was 400ng/mL. This method improved the sensitivity of FA assay and it could be generalized to any kind of target detection based on the use of an appropriate aptamer.
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27
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Hydrodynamic Radii of Ranibizumab, Aflibercept and Bevacizumab Measured by Time-Resolved Phosphorescence Anisotropy. Pharm Res 2016; 33:2025-32. [PMID: 27225494 PMCID: PMC4942501 DOI: 10.1007/s11095-016-1940-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 04/29/2016] [Indexed: 01/09/2023]
Abstract
PURPOSE To measure the hydrodynamic radii of intravitreal anti-VEGF drugs ranibizumab, aflibercept and bevacizumab with μs time-resolved phosphorescence anisotropy. METHODS Ruthenium-based dye Ru(bpy)2(mcbpy - O - Su - ester)(PF6)2, whose lifetime of several hundred nanoseconds is comparable to the rotational correlation time of these drugs in buffer, was used as a label. The hydrodynamic radii were calculated from the rotational correlation times of the Ru(bpy)2(mcbpy - O - Su - ester)(PF6)2-labelled drugs obtained with time-resolved phosphorescence anisotropy measurements in buffer/glycerol solutions of varying viscosity. RESULTS The measured radii of 2.76±0.04 nm for ranibizumab, 3.70±0.03 nm for aflibercept and 4.58±0.01 nm for bevacizumab agree with calculations based on molecular weight and other experimental measurements. CONCLUSIONS Time-resolved phosphorescence anisotropy is a relatively simple and straightforward method that allows experimental measurement of the hydrodynamic radius of individual proteins, and is superior to theoretical calculations which cannot give the required accuracy for a particular protein.
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28
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Kozer N, Clayton AHA. Analysis of complex anisotropy decays from single-frequency polarized-phasor ellipse plots. Methods Appl Fluoresc 2016; 4:024005. [PMID: 28809170 DOI: 10.1088/2050-6120/4/2/024005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The anisotropy decay of a fluorescently-labelled macromolecule provides information on the internal and global dynamics of the macromolecule. Weber was a pioneer of fluorescent probes, polarization and polarized phase-modulation methods and revealed the power of combining or comparing these methods to disentangle complex modes of emission depolarization. In this paper we take a similar course and show that when measurements of dynamic depolarization are combined with steady-state anisotropy, complex anisotropy decays can be deduced from measurements at a single modulation frequency. Specifically, a double exponential anisotropy decay can be resolved by combining one of the polarized emission phasors with the steady-state anisotropy. The key is the polarized phasor ellipse plot which provides a convenient visualisation aid and reduces the dimensionality of the minimisation problem from three variables to one variable. We illustrate these concepts with an experimental measurement of the anisotropy decay of a small cytoplasmic fluorescent probe in live cells.
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Affiliation(s)
- Noga Kozer
- Cell Biophysics Laboratory, Centre for Micro-Photonics, Faculty of Science, Engineering and Technology, Swinburne University of Technology, Victoria 3122, Australia
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29
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Ungvári T, Gogolák P, Bagdány M, Damjanovich L, Bene L. Perrin and Förster unified: Dual-laser triple-polarization FRET (3polFRET) for interactions at the Förster-distance and beyond. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:703-16. [DOI: 10.1016/j.bbamcr.2016.02.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 02/01/2016] [Accepted: 02/03/2016] [Indexed: 11/28/2022]
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30
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Levitt JA, Morton PE, Fruhwirth GO, Santis G, Chung PH, Parsons M, Suhling K. Simultaneous FRAP, FLIM and FAIM for measurements of protein mobility and interaction in living cells. BIOMEDICAL OPTICS EXPRESS 2015; 6:3842-54. [PMID: 26504635 PMCID: PMC4605044 DOI: 10.1364/boe.6.003842] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 08/16/2015] [Accepted: 08/18/2015] [Indexed: 05/23/2023]
Abstract
We present a novel integrated multimodal fluorescence microscopy technique for simultaneous fluorescence recovery after photobleaching (FRAP), fluorescence lifetime imaging (FLIM) and fluorescence anisotropy imaging (FAIM). This approach captures a series of polarization-resolved fluorescence lifetime images during a FRAP recovery, maximizing the information available from a limited photon budget. We have applied this method to analyse the behaviour of GFP-labelled coxsackievirus and adenovirus receptor (CAR) in living human epithelial cells. Our data reveal that CAR exists in oligomeric states throughout the cell, and that these complexes occur in conjunction with high immobile fractions of the receptor at cell-cell junctions. These findings shed light on previously unknown molecular associations between CAR receptors in intact cells and demonstrate the power of combined FRAP, FLIM and FAIM microscopy as a robust method to analyse complex multi-component dynamics in living cells.
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Affiliation(s)
- James A. Levitt
- Department of Physics, King’s College London, Strand, London WC2R 2LS, UK
| | - Penny E. Morton
- Division of Asthma, Allergy, and Lung Biology, Guys Campus, King’s College London, London, UK
- Randall Division of Cell and Molecular Biophysics, Guys Campus, King’s College London, London, SE1 1UL, UK
| | - Gilbert O. Fruhwirth
- Department of Imaging Chemsitry and Biology, Division of Imaging Sciences and Biomedical Engineering, St. Thomas Hospital, King's College London, SE1 7EH, UK
| | - George Santis
- Division of Asthma, Allergy, and Lung Biology, Guys Campus, King’s College London, London, UK
| | - Pei-Hua Chung
- Department of Physics, King’s College London, Strand, London WC2R 2LS, UK
| | - Maddy Parsons
- Randall Division of Cell and Molecular Biophysics, Guys Campus, King’s College London, London, SE1 1UL, UK
| | - Klaus Suhling
- Department of Physics, King’s College London, Strand, London WC2R 2LS, UK
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31
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Warren SC, Margineanu A, Katan M, Dunsby C, French PMW. Homo-FRET Based Biosensors and Their Application to Multiplexed Imaging of Signalling Events in Live Cells. Int J Mol Sci 2015; 16:14695-716. [PMID: 26133241 PMCID: PMC4519867 DOI: 10.3390/ijms160714695] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 06/15/2015] [Accepted: 06/17/2015] [Indexed: 12/20/2022] Open
Abstract
Multiplexed imaging of Förster Resonance Energy Transfer (FRET)-based biosensors potentially presents a powerful approach to monitoring the spatio-temporal correlation of signalling pathways within a single live cell. Here, we discuss the potential of homo-FRET based biosensors to facilitate multiplexed imaging. We demonstrate that the homo-FRET between pleckstrin homology domains of Akt (Akt-PH) labelled with mCherry may be used to monitor 3'-phosphoinositide accumulation in live cells and show how global analysis of time resolved fluorescence anisotropy measurements can be used to quantify this accumulation. We further present multiplexed imaging readouts of calcium concentration, using fluorescence lifetime measurements of TN-L15-a CFP/YFP based hetero-FRET calcium biosensor-with 3'-phosphoinositide accumulation.
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Affiliation(s)
- Sean C Warren
- Photonics Group, Department of Physics, Imperial College London, London SW7 2AZ, UK.
| | - Anca Margineanu
- Photonics Group, Department of Physics, Imperial College London, London SW7 2AZ, UK.
| | - Matilda Katan
- Structural and Molecular Biology, University College London, London WC1E 6BT, UK.
| | - Chris Dunsby
- Photonics Group, Department of Physics, Imperial College London, London SW7 2AZ, UK.
| | - Paul M W French
- Photonics Group, Department of Physics, Imperial College London, London SW7 2AZ, UK.
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32
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Bene L, Ungvári T, Fedor R, Nagy I, Damjanovich L. Dual-laser homo-FRET on the cell surface. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1096-112. [DOI: 10.1016/j.bbamcr.2015.02.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 01/19/2015] [Accepted: 02/02/2015] [Indexed: 10/24/2022]
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Xiao X, Li YF, Huang CZ, Zhen SJ. A novel graphene oxide amplified fluorescence anisotropy assay with improved accuracy and sensitivity. Chem Commun (Camb) 2015; 51:16080-3. [DOI: 10.1039/c5cc05902j] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A novel and versatile graphene oxide (GO) amplified fluorescence anisotropy (FA) strategy with improved accuracy and sensitivity has been successfully developed.
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Affiliation(s)
- Xue Xiao
- Key Laboratory of Luminescent and Real-Time Analytical Chemistry (Southwest University)
- Ministry of Education
- College of Chemistry and Chemical Engineering
- Southwest University
- Chongqing
| | - Yuan Fang Li
- Key Laboratory of Luminescent and Real-Time Analytical Chemistry (Southwest University)
- Ministry of Education
- College of Chemistry and Chemical Engineering
- Southwest University
- Chongqing
| | - Cheng Zhi Huang
- Key Laboratory of Luminescent and Real-Time Analytical Chemistry (Southwest University)
- Ministry of Education
- College of Chemistry and Chemical Engineering
- Southwest University
- Chongqing
| | - Shu Jun Zhen
- Key Laboratory of Luminescent and Real-Time Analytical Chemistry (Southwest University)
- Ministry of Education
- College of Chemistry and Chemical Engineering
- Southwest University
- Chongqing
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Single-laser polarization FRET (polFRET) on the cell surface. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:3047-64. [PMID: 25241341 DOI: 10.1016/j.bbamcr.2014.07.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 07/15/2014] [Accepted: 07/21/2014] [Indexed: 11/22/2022]
Abstract
A new method for the simultaneous detection of rotational mobility and proximity of cell surface receptors is presented based on cell-by-cell basis measurement of polarized fluorescence intensity components of the donor and acceptor of a FRET system. In addition to the FRET efficiency and the donor and acceptor concentrations, the method makes also possible the determination of the rotational characteristics and the associated fraction of the donors (FRET-fraction). The method is illustrated with flow cytometric and rFLIM measurements on donor-acceptor systems comprising fluorescently labeled whole antibodies and their Fab fragments against epitopes of the MHCI and MHCII cell surface receptors on human lymphoblast cells. Fluorescence anisotropy of donor and acceptor and FRET efficiency were measured for samples of different acceptor-to-donor concentration ratios. Acceptor anisotropy proved to be more sensitive than the donor anisotropy for sensing FRET. After determining the rotational constants of the donor-conjugated antibodies by measurements of FRET in the steady state, and by rFLIM as a reference, the associated fractions of the MHCI and MHCII molecules in their clusters were determined. Besides the flow cytometer and the wide-field rFLIM used in this study, the method can be applied also in other devices capable of dual-anisotropy detection.
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When one plus one does not equal two: fluorescence anisotropy in aggregates and multiply labeled proteins. Biophys J 2014; 106:1457-66. [PMID: 24703307 DOI: 10.1016/j.bpj.2014.02.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 02/13/2014] [Accepted: 02/25/2014] [Indexed: 12/11/2022] Open
Abstract
The behavior of fluorescence anisotropy and polarization in systems with multiple dyes is well known. Homo-FRET and its consequent energy migration cause the fluorescence anisotropy to decrease as the number of like fluorophores within energy transfer distance increases. This behavior is well understood when all subunits within a cluster are saturated with fluorophores. However, incomplete labeling as might occur from a mixture of endogenous and labeled monomer units, incomplete saturation of binding sites, or photobleaching produces stochastic mixtures. Models in widespread and longstanding use that describe these mixtures apply an assumption of equal fluorescence efficiency for all sites first stated by Weber and Daniel in 1966. The assumption states that fluorophores have the same brightness when free in solution as they do in close proximity to each other in a cluster. The assumption simplifies descriptions of anisotropy trends as the fractional labeling of the cluster changes. However, fluorophores in close proximity often exhibit nonadditivity due to such things as self-quenching behavior or exciplex formation. Therefore, the anisotropy of stochastic mixtures of fluorophore clusters of a particular size will depend on the behavior of those fluorophores in clusters. We present analytical expressions for fractionally labeled clusters exhibiting a range of behaviors, and experimental results from two systems: an assembled tetrameric cluster of fluorescent proteins and stochastically labeled bovine serum albumin containing up to 24 fluorophores. The experimental results indicate that clustered species do not follow the assumption of equal fluorescence efficiency in the systems studied with clustered fluorophores showing reduced fluorescence intensity. Application of the assumption of equal fluorescence efficiency will underpredict anisotropy and consequently underestimate cluster size in these two cases. The theoretical results indicate that careful selection of the fractional labeling in strongly quenched systems will enhance opportunities to determine cluster sizes, making accessible larger clusters than are currently considered possible.
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Statistical filtering in fluorescence microscopy and fluorescence correlation spectroscopy. Anal Bioanal Chem 2014; 406:4797-813. [DOI: 10.1007/s00216-014-7892-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 05/07/2014] [Accepted: 05/13/2014] [Indexed: 01/21/2023]
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Xue M, Zink JI. Probing the Microenvironment in the Confined Pores of Mesoporous Silica Nanoparticles. J Phys Chem Lett 2014; 5:839-842. [PMID: 24803992 PMCID: PMC3985790 DOI: 10.1021/jz402760b] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Accepted: 02/11/2014] [Indexed: 06/03/2023]
Abstract
The microenvironment inside of the pores of mesoporous silica nanoparticles is probed using spectroscopic techniques. The probe molecules are sealed inside of the pores by a nanovalve system that is capable of controlling the access to the pore and ensuring the exclusive probing of the pore environment without any interference from the probe molecules on the outer surface of the particles or from the surrounding solution. Rigidochromism studies are used to evaluate the rigidity of the solvent matrix inside of the pore, and dynamic fluorescence anisotropy experiments are employed to determine the rotational diffusion freedom of the probe molecule. The data show that those probe molecules are neither completely free to move nor tightly attached to the pore wall, and their mobility is changed by altering the charge of the pore wall.
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Abstract
Fluorescence can be characterized by its intensity, position, wavelength, lifetime, and polarization. The more of these features are acquired in a single measurement, the more can be learned about the sample, i.e., the microenvironment of the fluorescence probe. Polarization-resolved fluorescence lifetime imaging-time-resolved fluorescence anisotropy imaging, TR-FAIM-allows mapping of viscosity or binding or of homo-FRET which can indicate dimerization or generally oligomerization.
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Affiliation(s)
- Klaus Suhling
- Department of Physics, King's College London, London, UK
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Warren SC, Margineanu A, Alibhai D, Kelly DJ, Talbot C, Alexandrov Y, Munro I, Katan M, Dunsby C, French PMW. Rapid global fitting of large fluorescence lifetime imaging microscopy datasets. PLoS One 2013; 8:e70687. [PMID: 23940626 PMCID: PMC3734241 DOI: 10.1371/journal.pone.0070687] [Citation(s) in RCA: 136] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 06/20/2013] [Indexed: 12/18/2022] Open
Abstract
Fluorescence lifetime imaging (FLIM) is widely applied to obtain quantitative information from fluorescence signals, particularly using Förster Resonant Energy Transfer (FRET) measurements to map, for example, protein-protein interactions. Extracting FRET efficiencies or population fractions typically entails fitting data to complex fluorescence decay models but such experiments are frequently photon constrained, particularly for live cell or in vivo imaging, and this leads to unacceptable errors when analysing data on a pixel-wise basis. Lifetimes and population fractions may, however, be more robustly extracted using global analysis to simultaneously fit the fluorescence decay data of all pixels in an image or dataset to a multi-exponential model under the assumption that the lifetime components are invariant across the image (dataset). This approach is often considered to be prohibitively slow and/or computationally expensive but we present here a computationally efficient global analysis algorithm for the analysis of time-correlated single photon counting (TCSPC) or time-gated FLIM data based on variable projection. It makes efficient use of both computer processor and memory resources, requiring less than a minute to analyse time series and multiwell plate datasets with hundreds of FLIM images on standard personal computers. This lifetime analysis takes account of repetitive excitation, including fluorescence photons excited by earlier pulses contributing to the fit, and is able to accommodate time-varying backgrounds and instrument response functions. We demonstrate that this global approach allows us to readily fit time-resolved fluorescence data to complex models including a four-exponential model of a FRET system, for which the FRET efficiencies of the two species of a bi-exponential donor are linked, and polarisation-resolved lifetime data, where a fluorescence intensity and bi-exponential anisotropy decay model is applied to the analysis of live cell homo-FRET data. A software package implementing this algorithm, FLIMfit, is available under an open source licence through the Open Microscopy Environment.
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Affiliation(s)
- Sean C Warren
- Department of Chemistry, Institute for Chemical Biology, Imperial College London, London, United Kingdom.
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Sun Y, Rombola C, Jyothikumar V, Periasamy A. Förster resonance energy transfer microscopy and spectroscopy for localizing protein-protein interactions in living cells. Cytometry A 2013; 83:780-93. [PMID: 23813736 DOI: 10.1002/cyto.a.22321] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 04/08/2013] [Accepted: 05/23/2013] [Indexed: 12/15/2022]
Abstract
The fundamental theory of Förster resonance energy transfer (FRET) was established in the 1940s. Its great power was only realized in the past 20 years after different techniques were developed and applied to biological experiments. This success was made possible by the availability of suitable fluorescent probes, advanced optics, detectors, microscopy instrumentation, and analytical tools. Combined with state-of-the-art microscopy and spectroscopy, FRET imaging allows scientists to study a variety of phenomena that produce changes in molecular proximity, thereby leading to many significant findings in the life sciences. In this review, we outline various FRET imaging techniques and their strengths and limitations; we also provide a biological model to demonstrate how to investigate protein-protein interactions in living cells using both intensity- and fluorescence lifetime-based FRET microscopy methods.
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Affiliation(s)
- Yuansheng Sun
- The W.M. Keck Center for Cellular Imaging (KCCI), Department of Biology, Physical and Life Sciences Building, University of Virginia, Charlottesville, Virginia
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Romero G, Qiu Y, Murray RA, Moya SE. Study of intracellular delivery of doxorubicin from poly(lactide-co-glycolide) nanoparticles by means of fluorescence lifetime imaging and confocal Raman microscopy. Macromol Biosci 2013; 13:234-41. [PMID: 23316003 DOI: 10.1002/mabi.201200235] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 09/21/2012] [Indexed: 11/09/2022]
Abstract
The intracellular delivery of Doxorubicin (Dox) from poly(lactide-co-glycolide) (PLGA) nanoparticles stabilised with bovine serum albumin, in HepG2 cells, is studied via flow cytometry, fluorescence lifetime imaging microscopy (FLIM), confocal Raman microscopy (CRM) and cell viability studies. Flow cytometry shows that the initial uptake of PLGA and Dox follow the same kinetics. However, following 8 h of incubation, the fluorescence intensity and cellular uptake of Dox decreases, while in the case of PLGA both parameters remain constant. FLIM shows the presence of a single-lifetime species, with a lifetime of 1.15 ns when measured inside the cells. Cell viability decreases by approximately 20% when incubated for 24 h with PLGA loaded with Dox, with a particle concentration of 100 µg · mL(-1). At the single-cell level, CRM shows changes in the bands from DNA and proteins in the cell nucleus when incubated with PLGA loaded with Dox.
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Helm PJ. Proposal of a New Method for Measuring Förster Resonance Energy Transfer (FRET) Rapidly, Quantitatively and Non-Destructively. Int J Mol Sci 2012. [PMID: 23202903 PMCID: PMC3497277 DOI: 10.3390/ijms131012367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
The process of radiationless energy transfer from a chromophore in an excited electronic state (the “donor”) to another chromophore (an “acceptor”), in which the energy released by the donor effects an electronic transition, is known as “Förster Resonance Energy Transfer” (FRET). The rate of energy transfer is dependent on the sixth power of the distance between donor and acceptor. Determining FRET efficiencies is tantamount to measuring distances between molecules. A new method is proposed for determining FRET efficiencies rapidly, quantitatively, and non-destructively on ensembles containing donor acceptor pairs: at wavelengths suitable for mutually exclusive excitations of donors and acceptors, two laser beams are intensity-modulated in rectangular patterns at duty cycle ½ and frequencies f1 and f2 by electro-optic modulators. In an ensemble exposed to these laser beams, the donor excitation is modulated at f1, and the acceptor excitation, and therefore the degree of saturation of the excited electronic state of the acceptors, is modulated at f2. Since the ensemble contains donor acceptor pairs engaged in FRET, the released donor fluorescence is modulated not only at f1 but also at the beat frequency Δf: = |f1 − f2|. The depth of the latter modulation, detectable via a lock-in amplifier, quantitatively indicates the FRET efficiency.
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Affiliation(s)
- Paul Johannes Helm
- Center of Molecular Biology and Neuroscience and Institute of Basic Medical Sciences, Department of Anatomy, University of Oslo, P.O. Box 1105-Blindern, NO-0317 Oslo, Norway.
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Vishwasrao H, Trifilieff P, Kandel E. In vivo imaging of the actin polymerization state with two-photon fluorescence anisotropy. Biophys J 2012; 102:1204-14. [PMID: 22404943 PMCID: PMC3296026 DOI: 10.1016/j.bpj.2012.01.031] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 01/10/2012] [Accepted: 01/17/2012] [Indexed: 01/31/2023] Open
Abstract
Using two-photon fluorescence anisotropy imaging of actin-GFP, we have developed a method for imaging the actin polymerization state that is applicable to a broad range of experimental systems extending from fixed cells to live animals. The incorporation of expressed actin-GFP monomers into endogenous actin polymers enables energy migration FRET (emFRET, or homoFRET) between neighboring actin-GFPs. This energy migration reduces the normally high polarization of the GFP fluorescence. We derive a simple relationship between the actin-GFP fluorescence polarization anisotropy and the actin polymer fraction, thereby enabling a robust means of imaging the actin polymerization state with high spatiotemporal resolution and providing what to the best of our knowledge are the first direct images of the actin polymerization state in live, adult brain tissue and live, intact Drosophila larvae.
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Affiliation(s)
- Harshad D. Vishwasrao
- Department of Neuroscience, Columbia University, New York, New York
- Howard Hughes Medical Institute, New York, New York
| | - Pierre Trifilieff
- Department of Neuroscience, Columbia University, New York, New York
- New York State Psychiatric Institute, New York, New York
- Research Foundation for Mental Hygiene, New York, New York
| | - Eric R. Kandel
- Department of Neuroscience, Columbia University, New York, New York
- Howard Hughes Medical Institute, New York, New York
- Kavli Institute for Brain Science, New York, New York
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Abstract
Biological research has always tremendously benefited from the development of key methodology. In fact, it was the advent of microscopy that shaped our understanding of cells as the fundamental units of life. Microscopic techniques are still central to the elucidation of biological units and processes, but equally important are methods that allow access to the dimension of time, to investigate the dynamics of molecular functions and interactions. Here, fluorescence spectroscopy with its sensitivity to access the single-molecule level, and its large temporal resolution, has been opening up fully new perspectives for cell biology. Here we summarize the key fluorescent techniques used to study cellular dynamics, with the focus on lipid and membrane systems.
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Ehrlich N, Christensen AL, Stamou D. Fluorescence Anisotropy Based Single Liposome Assay to Measure Molecule–Membrane Interactions. Anal Chem 2011; 83:8169-76. [DOI: 10.1021/ac2017234] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Nicky Ehrlich
- Bio-Nanotechnology Laboratory, Department of Neuroscience and Pharmacology, ‡Nano-Science Center, and §Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Andreas L. Christensen
- Bio-Nanotechnology Laboratory, Department of Neuroscience and Pharmacology, ‡Nano-Science Center, and §Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Dimitrios Stamou
- Bio-Nanotechnology Laboratory, Department of Neuroscience and Pharmacology, ‡Nano-Science Center, and §Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, 2100 Copenhagen, Denmark
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Kozer N, Henderson C, Jackson JT, Nice EC, Burgess AW, Clayton AHA. Evidence for extended YFP-EGFR dimers in the absence of ligand on the surface of living cells. Phys Biol 2011; 8:066002. [PMID: 21946082 DOI: 10.1088/1478-3975/8/6/066002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The epidermal growth factor receptor (EGFR) is a member of the erbB tyrosine kinase family of receptors. Structural studies have revealed two distinct conformations of the ectodomain of the EGFR: a compact, tethered, conformation and an untethered extended conformation. In the context of a monomer-dimer transition model, ligand binding is thought to untether the monomeric receptor leading to exposure of a dimerization arm which then facilitates receptor dimerization, kinase activation and signaling. For receptors directed orthogonal to the local plane of the membrane surface, this would lead to a large change in the distance of the receptor N-terminus from the membrane surface. To investigate this experimentally, we produced stable BaF/3 cell lines expressing a biochemically functional yellow fluorescent protein (YFP)-EGFR chimera and determined the vertical separation of the N-terminal YFP tag from the membrane using fluorescence resonance energy transfer (FRET) techniques. Homo-FRET/rFLIM was employed to determine the presence of unliganded dimers and to measure the average distance between the N-terminal tags in those dimers. The results suggest that EGF-induced activation occurs within or between pre-formed and extended dimers with very little change in the extension of the N-terminii from the membrane surface. These results provide constraints on possible models for EGFR activation.
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Affiliation(s)
- Noga Kozer
- Centre for Microphotonics, Swinburne University of Technology, Victoria, Australia
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Non fitting based FRET-FLIM analysis approaches applied to quantify protein-protein interactions in live cells. Biophys Rev 2011; 3:63-70. [PMID: 28510004 DOI: 10.1007/s12551-011-0047-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Accepted: 04/26/2011] [Indexed: 01/14/2023] Open
Abstract
New imaging methodologies in quantitative fluorescence microscopy and nanoscopy have been developed in the last few years and are beginning to be extensively applied to biological problems, such as the localization and quantification of protein interactions. Fluorescence resonance energy transfer (FRET) detected by fluorescence lifetime imaging microscopy (FLIM) is currently employed not only in biophysics or chemistry but also in bio-medicine, thanks to new advancements in technology and also new developments in data treatment. FRET-FLIM can be a very useful tool to ascertain protein interactions occurring in single living cells. In this review, we stress the importance of increasing the acquisition speed when working in vivo employing Time-Domain FLIM. The development of the new mathematical-based non-fitting methods allows the determining of the fraction of interacting donor without the requirement of high count statistics, and thus allows the performing of high speed acquisitions in FRET-FLIM to still be quantitative.
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Ganguly S, Clayton AHA, Chattopadhyay A. Organization of higher-order oligomers of the serotonin₁(A) receptor explored utilizing homo-FRET in live cells. Biophys J 2011; 100:361-8. [PMID: 21244832 DOI: 10.1016/j.bpj.2010.12.3692] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 11/16/2010] [Accepted: 12/08/2010] [Indexed: 10/18/2022] Open
Abstract
The serotonin₁(A) receptor is a representative member of the GPCR superfamily and serves as an important drug target. The possible role of GPCR oligomerization in receptor function is an active area of research. We monitored the oligomerization state of serotonin₁(A) receptors using homo-FRET and fluorescence lifetime measurements. Homo-FRET is estimated by a reduction in fluorescence anisotropy and provides a superior approach for exploring oligomerization. In addition, homo-FRET offers the possibility of detecting higher-order oligomers. On the basis of an observed increase in fluorescence anisotropy upon progressive photobleaching and analysis of the difference between the extrapolated anisotropy and the predicted anisotropy of an immobile monomer, we propose the presence of constitutive oligomers of the serotonin₁(A) receptor. To the best of our knowledge, these results constitute the first report of higher-order oligomers for the serotonin₁(A) receptor. We further show that cholesterol depletion and antagonist treatment result in a reduced population of higher-order oligomers. In contrast, agonist stimulation and destabilization of the actin cytoskeleton lead to an increased contribution from higher oligomers. These results provide novel insight into the oligomerization status of the serotonin₁(A) receptor that could enhance the ability to design better therapeutic strategies to combat diseases related to malfunctioning of GPCRs.
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Affiliation(s)
- Sourav Ganguly
- Centre for Cellular and Molecular Biology, Hyderabad, India
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Rusakov DA, Savtchenko LP, Zheng K, Henley JM. Shaping the synaptic signal: molecular mobility inside and outside the cleft. Trends Neurosci 2011; 34:359-69. [PMID: 21470699 PMCID: PMC3133640 DOI: 10.1016/j.tins.2011.03.002] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2011] [Revised: 03/01/2011] [Accepted: 03/02/2011] [Indexed: 02/06/2023]
Abstract
Rapid communication in the brain relies on the release and diffusion of small transmitter molecules across the synaptic cleft. How these diffuse signals are transformed into cellular responses is determined by the scatter of target postsynaptic receptors, which in turn depends on receptor movement in cell membranes. Thus, by shaping information transfer in neural circuits, mechanisms that regulate molecular mobility affect nearly every aspect of brain function and dysfunction. Here we review two facets of molecular mobility that have traditionally been considered separately, namely extracellular and intra-membrane diffusion. By focusing on the interplay between these processes we illustrate the remarkable versatility of signal formation in synapses and highlight areas of emerging understanding in the molecular physiology and biophysics of synaptic transmission.
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Affiliation(s)
- Dmitri A Rusakov
- Institute of Neurology, University College London, Queen Square, London WC1 3BG, UK
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