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Coucke Q, Parveen N, Fernández GS, Qian C, Hofkens J, Debyser Z, Hendrix J. Particle-based phasor-FLIM-FRET resolves protein-protein interactions inside single viral particles. BIOPHYSICAL REPORTS 2023; 3:100122. [PMID: 37649577 PMCID: PMC10463199 DOI: 10.1016/j.bpr.2023.100122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Accepted: 08/07/2023] [Indexed: 09/01/2023]
Abstract
Fluorescence lifetime imaging microscopy (FLIM) is a popular modality to create additional contrast in fluorescence images. By carefully analyzing pixel-based nanosecond lifetime patterns, FLIM allows studying complex molecular populations. At the single-molecule or single-particle level, however, image series often suffer from low signal intensities per pixel, rendering it difficult to quantitatively disentangle different lifetime species, such as during Förster resonance energy transfer (FRET) analysis in the presence of a significant donor-only fraction. In this article we investigate whether an object localization strategy and the phasor approach to FLIM have beneficial effects when carrying out FRET analyses of single particles. Using simulations, we first showed that an average of ∼300 photons, spread over the different pixels encompassing single fluorescing particles and without background, is enough to determine a correct phasor signature (SD < 5% for a 4-ns lifetime). For immobilized single- or double-labeled dsDNA molecules, we next validated that particle-based phasor-FLIM-FRET readily allows estimating fluorescence lifetimes and FRET from single molecules. Thirdly, we applied particle-based phasor-FLIM-FRET to investigate protein-protein interactions in subdiffraction HIV-1 viral particles. To do this, we first quantitatively compared the fluorescence brightness, lifetime, and photostability of different popular fluorescent protein-based FRET probes when genetically fused to the HIV-1 integrase enzyme in viral particles, and conclude that eGFP, mTurquoise2, and mScarlet perform best. Finally, for viral particles coexpressing FRET-donor/acceptor-labeled IN, we determined the absolute FRET efficiency of IN oligomers. Available in a convenient open-source graphical user interface, we believe that particle-based phasor-FLIM-FRET is a promising tool to provide detailed insights in samples suffering from low overall signal intensities.
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Affiliation(s)
- Quinten Coucke
- Molecular Imaging and Photonics Division, Department of Chemistry, KU Leuven, Leuven, Belgium
| | - Nagma Parveen
- Molecular Imaging and Photonics Division, Department of Chemistry, KU Leuven, Leuven, Belgium
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Guillermo Solís Fernández
- Molecular Imaging and Photonics Division, Department of Chemistry, KU Leuven, Leuven, Belgium
- UFIEC, National Institute of Health Carlos III, Madrid, Spain
| | - Chen Qian
- Department of Chemistry, Center for Nano Science (CENS), Center for Integrated Protein Science Munich (CIPSM), and Nanosystems Initiative Munich (NIM), Ludwig Maximilians-Universität München, Munich, Germany
| | - Johan Hofkens
- Molecular Imaging and Photonics Division, Department of Chemistry, KU Leuven, Leuven, Belgium
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Zeger Debyser
- Laboratory for Molecular Virology and Gene Therapy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
| | - Jelle Hendrix
- Molecular Imaging and Photonics Division, Department of Chemistry, KU Leuven, Leuven, Belgium
- Dynamic Bioimaging Lab, Advanced Optical Microscopy Centre and Biomedical Research Institute, Hasselt University, Hasselt, Belgium
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Szalóki N, Doan-Xuan QM, Szöllősi J, Tóth K, Vámosi G, Bacsó Z. High throughput FRET analysis of protein-protein interactions by slide-based imaging laser scanning cytometry. Cytometry A 2013; 83:818-29. [DOI: 10.1002/cyto.a.22315] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 04/24/2013] [Accepted: 05/12/2013] [Indexed: 11/12/2022]
Affiliation(s)
- Nikoletta Szalóki
- Department of Biophysics and Cell Biology; Medical and Health Science Center, Research Center for Molecular Medicine, University of Debrecen; Nagyerdei krt. 98; H-4032; Debrecen; Hungary
| | - Quang Minh Doan-Xuan
- Department of Biophysics and Cell Biology; Medical and Health Science Center, Research Center for Molecular Medicine, University of Debrecen; Nagyerdei krt. 98; H-4032; Debrecen; Hungary
| | | | - Katalin Tóth
- German Cancer Research Center (DKFZ), Biophysics of Macromolecules (B040); Im Neuenheimer Feld 580; D-69120; Heidelberg; Germany
| | - György Vámosi
- Department of Biophysics and Cell Biology; Medical and Health Science Center, Research Center for Molecular Medicine, University of Debrecen; Nagyerdei krt. 98; H-4032; Debrecen; Hungary
| | - Zsolt Bacsó
- Department of Biophysics and Cell Biology; Medical and Health Science Center, Research Center for Molecular Medicine, University of Debrecen; Nagyerdei krt. 98; H-4032; Debrecen; Hungary
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Lajevardipour A, Clayton AHA. The effect of translational motion on FLIM measurements-single particle phasor-FLIM. J Fluoresc 2013; 23:671-9. [PMID: 23471622 DOI: 10.1007/s10895-013-1174-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2012] [Accepted: 02/24/2013] [Indexed: 11/25/2022]
Abstract
Fluorescence lifetime imaging microscopy or FLIM provides a versatile tool for spatially-mapping macromolecular interactions and environments through pixel-by-pixel resolution of the excited-state lifetime. In conventional frequency-domain FLIM the phase and modulation of the detected fluorescence are determined by the photophysics of the fluorophore only. However, translational motion on the timescale of FLIM acquisition can significantly perturb apparent phase and modulation values owing to intensity fluctuations and phase decoherence. Using the phasor plot we outline a simple analytic theory, numerical simulations and measurements on fluorescent beads (ex 470 nm, em 520 nm). Fluctuations due to particle motions result in an increase in the number and spread of phasors, an effect we refer to as phasor broadening. The approach paves the way for the measurement of lifetimes and translational motion from one experiment.
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Affiliation(s)
- Alireza Lajevardipour
- Centre for Micro-photonics, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, John Street, PO Box 218, Hawthorn, Victoria, 3122, Australia
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