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Drobizhev M, Molina RS, Franklin J. Multiphoton Bleaching of Red Fluorescent Proteins and the Ways to Reduce It. Int J Mol Sci 2022; 23:770. [PMID: 35054953 PMCID: PMC8775990 DOI: 10.3390/ijms23020770] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 01/06/2022] [Accepted: 01/07/2022] [Indexed: 11/16/2022] Open
Abstract
Red fluorescent proteins and biosensors built upon them are potentially beneficial for two-photon laser microscopy (TPLM) because they can image deeper layers of tissue, compared to green fluorescent proteins. However, some publications report on their very fast photobleaching, especially upon excitation at 750-800 nm. Here we study the multiphoton bleaching properties of mCherry, mPlum, tdTomato, and jREX-GECO1, measuring power dependences of photobleaching rates K at different excitation wavelengths across the whole two-photon absorption spectrum. Although all these proteins contain the chromophore with the same chemical structure, the mechanisms of their multiphoton bleaching are different. The number of photons required to initiate a photochemical reaction varies, depending on wavelength and power, from 2 (all four proteins) to 3 (jREX-GECO1) to 4 (mCherry, mPlum, tdTomato), and even up to 8 (tdTomato). We found that at sufficiently low excitation power P, the rate K often follows a quadratic power dependence, that turns into higher order dependence (K~Pα with α > 2) when the power surpasses a particular threshold P*. An optimum intensity for TPLM is close to the P*, because it provides the highest signal-to-background ratio and any further reduction of laser intensity would not improve the fluorescence/bleaching rate ratio. Additionally, one should avoid using wavelengths shorter than a particular threshold to avoid fast bleaching due to multiphoton ionization.
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Affiliation(s)
- Mikhail Drobizhev
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT 59717, USA;
| | - Rosana S. Molina
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, MT 59717, USA;
| | - Jacob Franklin
- Vidrio Technologies LLC, 19955 Highland Vista Drive Suite 150, Ashburn, VA 20147, USA;
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Molina RS, King J, Franklin J, Clack N, McRaven C, Goncharov V, Flickinger D, Svoboda K, Drobizhev M, Hughes TE. High throughput instrument to screen fluorescent proteins under two-photon excitation. BIOMEDICAL OPTICS EXPRESS 2020; 11:7192-7203. [PMID: 33408990 PMCID: PMC7747914 DOI: 10.1364/boe.409353] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 10/21/2020] [Accepted: 11/10/2020] [Indexed: 06/12/2023]
Abstract
Two-photon microscopy together with fluorescent proteins and fluorescent protein-based biosensors are commonly used tools in neuroscience. To enhance their experimental scope, it is important to optimize fluorescent proteins for two-photon excitation. Directed evolution of fluorescent proteins under one-photon excitation is common, but many one-photon properties do not correlate with two-photon properties. A simple system for expressing fluorescent protein mutants is E. coli colonies on an agar plate. The small focal volume of two-photon excitation makes creating a high throughput screen in this system a challenge for a conventional point-scanning approach. We present an instrument and accompanying software that solves this challenge by selectively scanning each colony based on a colony map captured under one-photon excitation. This instrument, called the GIZMO, can measure the two-photon excited fluorescence of 10,000 E. coli colonies in 7 hours. We show that the GIZMO can be used to evolve a fluorescent protein under two-photon excitation.
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Affiliation(s)
- Rosana S Molina
- Department of Cell Biology & Neuroscience, Montana State University, 109 Lewis Hall, Bozeman, MT 59717, USA
| | - Jonathan King
- Vidrio Technologies, LLC, PO Box 1870, Leesburg, VA 20177, USA
| | - Jacob Franklin
- Vidrio Technologies, LLC, PO Box 1870, Leesburg, VA 20177, USA
| | - Nathan Clack
- Vidrio Technologies, LLC, PO Box 1870, Leesburg, VA 20177, USA
| | - Christopher McRaven
- Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
- Current address: Advanced Engineering Laboratory, Woods Hole Oceanographic Institution, 86 Water Street, Woods Hole, MA 02543, USA
| | - Vasily Goncharov
- Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | | | - Karel Svoboda
- Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Mikhail Drobizhev
- Department of Cell Biology & Neuroscience, Montana State University, 109 Lewis Hall, Bozeman, MT 59717, USA
| | - Thomas E Hughes
- Department of Cell Biology & Neuroscience, Montana State University, 109 Lewis Hall, Bozeman, MT 59717, USA
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Sun D, Yang Y, Liu S, Li Y, Luo M, Qi X, Ma Z. Excitation and emission dual-wavelength confocal metalens designed directly in the biological tissue environment for two-photon micro-endoscopy. BIOMEDICAL OPTICS EXPRESS 2020; 11:4408-4418. [PMID: 32923052 PMCID: PMC7449710 DOI: 10.1364/boe.395539] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 06/27/2020] [Accepted: 07/09/2020] [Indexed: 06/11/2023]
Abstract
With the advantages of completely controlling the phase, amplitude, and polarization in subwavelength range, metalenses have drawn intensive attentions in high resolution two-photon micro-endoscopic fluorescence imaging system. However, chromatic dispersion and severe scattering of biological tissue significantly reduce excitation-collection efficiency in the traditional two-photon imaging system based on traditional metalenses designed in the air background. Here, an excitation and emission dual-wavelength confocal and polarization-insensitive metalens designed in the biological tissue environment was proposed by adopting the composite embedding structure and spatial multiplexing approach. The metalens with numerical aperture (NA) of 0.895 can focus the excitation (915 nm) and emission (510 nm) beams to the same focal spot in the mouse cortex. According to the theoretical simulation of two-photon fluorescence imaging, the lateral resolution of the collected fluorescent spots via the proposed metalens can be up to 0.42 µm. Compared to the metalens designed in the air environment, the collection efficiency of fluorescent spot is improved from 5.92% to 14.60%. Our investigation has opened a new window of high resolution and minimally invasive imaging in deep regions of biological tissues.
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Affiliation(s)
- Dongqing Sun
- School of Biomedical Engineering and Technology, Tianjin Medical University, Tianjin 300070, China
| | - Yanju Yang
- Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China
| | - Shujing Liu
- School of Biomedical Engineering and Technology, Tianjin Medical University, Tianjin 300070, China
| | - Yang Li
- School of Biomedical Engineering and Technology, Tianjin Medical University, Tianjin 300070, China
| | - Mingyan Luo
- School of Biomedical Engineering and Technology, Tianjin Medical University, Tianjin 300070, China
| | - Xiaoling Qi
- School of Biomedical Engineering and Technology, Tianjin Medical University, Tianjin 300070, China
| | - Zengguang Ma
- School of Biomedical Engineering and Technology, Tianjin Medical University, Tianjin 300070, China
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Grabarek D, Andruniów T. Assessment of Functionals for TDDFT Calculations of One- and Two-Photon Absorption Properties of Neutral and Anionic Fluorescent Proteins Chromophores. J Chem Theory Comput 2018; 15:490-508. [PMID: 30485096 DOI: 10.1021/acs.jctc.8b00769] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Performance of DFT functionals with different percentages of exact Hartree-Fock exchange energy (EX) is assessed for recovery of the CC2 reference one- (OPA) and two-photon absorption (TPA) spectra of fluorescent proteins chromophores in vacuo. The investigated DFT functionals, together with their EX contributions are BLYP (0%), B3LYP (20%), B1LYP (25%), BHandHLYP (50%), and CAM-B3LYP (19% at short range and 65% at long range). Our test set consists of anionic and neutral chromophores as naturally occurring in the fluorescent proteins. For the first time, we compare TDDFT and CC2 methods for higher excited states than the S1 state, exhibiting relatively large TPA intensity. Our TDDFT results for neutral chromophores reveal an increase in excitation energies as well as TPA and OPA intensities errors, compared to CC2-derived results, as the DFT functional contains less exact exchange. The long-range-corrected CAM-B3LYP functional performs the best, closely followed by BHandHLYP, while BLYP usually significantly underestimates all investigated spectral properties, hence being the worst in reproducing the reference CC2 results. The hybrid B3LYP and B1LYP functionals can be roughly placed in between. We propose that TDDFT may underestimate the TPA intensities for neutral chromophores of fluorescent proteins due to underestimated oscillator strengths between some excited states. In the case of anionic chromophores, we find that B3LYP and B1LYP functionals overcome others in terms of reproducing CC2 excitation energies. On the other hand, however, TPA intensity is usually significantly underestimated, and in this respect, CAM-B3LYP functional seems to be again superior. In contrast to the case of neutral chromophores, it seems that a large magnitude of excited-state dipole moments or changes in dipole moments upon excitation may be the driving force behind high TPA transition moments.
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Affiliation(s)
- Dawid Grabarek
- Advanced Materials Engineering and Modelling Group , Wroclaw University of Science and Technology , Wyb. Wyspianskiego 27 , 50-370 Wroclaw , Poland
| | - Tadeusz Andruniów
- Advanced Materials Engineering and Modelling Group , Wroclaw University of Science and Technology , Wyb. Wyspianskiego 27 , 50-370 Wroclaw , Poland
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Charan K, Li B, Wang M, Lin CP, Xu C. Fiber-based tunable repetition rate source for deep tissue two-photon fluorescence microscopy. BIOMEDICAL OPTICS EXPRESS 2018; 9:2304-2311. [PMID: 29760989 PMCID: PMC5946790 DOI: 10.1364/boe.9.002304] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 04/16/2018] [Accepted: 04/17/2018] [Indexed: 05/02/2023]
Abstract
Deep tissue multiphoton imaging requires high peak power to enhance signal and low average power to prevent thermal damage. Both goals can be advantageously achieved through laser repetition rate tuning instead of simply adjusting the average power. We show that the ideal repetition rate for deep two-photon imaging in the mouse brain is between 1 and 10 MHz, and we present a fiber-based source with an arbitrarily tunable repetition rate within this range. The performance of the new source is compared to a mode-locked Ti:Sapphire (Ti:S) laser for in vivo imaging of mouse brain vasculature. At 2.5 MHz, the fiber source requires 5.1 times less average power to obtain the same signal as a standard Ti:S laser operating at 80 MHz.
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Affiliation(s)
- Kriti Charan
- School of Applied Physics and Engineering, Cornell University, Ithaca, NY 14850, USA
| | - Bo Li
- School of Applied Physics and Engineering, Cornell University, Ithaca, NY 14850, USA
| | - Mengran Wang
- School of Applied Physics and Engineering, Cornell University, Ithaca, NY 14850, USA
| | - Charles P. Lin
- Wellman Center for Photomedicine and Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Chris Xu
- School of Applied Physics and Engineering, Cornell University, Ithaca, NY 14850, USA
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