1
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Perez D, Dowlatshahi DP, Azaldegui CA, Ansell TB, Dahlberg PD, Moerner WE. Exploring Transient States of PAmKate to Enable Improved Cryogenic Single-Molecule Imaging. J Am Chem Soc 2024. [PMID: 39388715 DOI: 10.1021/jacs.4c05632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/12/2024]
Abstract
Super-resolved cryogenic correlative light and electron microscopy is a powerful approach which combines the single-molecule specificity and sensitivity of fluorescence imaging with the nanoscale resolution of cryogenic electron tomography. Key to this method is active control over the emissive state of fluorescent labels to ensure sufficient sparsity to localize individual emitters. Recent work has identified fluorescent proteins (FPs) that photoactivate or photoswitch efficiently at cryogenic temperatures, but long on-times due to reduced quantum yield of photobleaching remain a challenge for imaging structures with a high density of localizations. In this work, we explore the photophysical properties of the red photoactivatable FP PAmKate and identify a 2-color process leading to enhanced turn-off of active emitters, improving localization rate. Specifically, after excitation of ground state molecules, we find that a transient state forms with a lifetime of ∼2 ms under cryogenic conditions, which can be bleached by exposure to a second wavelength. We measure the response of the transient state to different wavelengths, demonstrate how this mechanism can be used to improve imaging, and provide a blueprint for the study of other FPs at cryogenic temperatures.
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Affiliation(s)
- Davis Perez
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Dara P Dowlatshahi
- Biosciences Division, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
- Department of Structural Biology, Stanford University, Stanford, California 94305, United States
| | - Christopher A Azaldegui
- Division of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - T Bertie Ansell
- Division of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Peter D Dahlberg
- Division of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - W E Moerner
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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2
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Perez D, Dowlatshahi DP, Azaldegui CA, Ansell TB, Dahlberg PD, Moerner WE. Exploring transient states of PAmKate to enable improved cryogenic single-molecule imaging. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.24.590965. [PMID: 38712218 PMCID: PMC11071506 DOI: 10.1101/2024.04.24.590965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Super-resolved cryogenic correlative light and electron microscopy is a powerful approach which combines the single-molecule specificity and sensitivity of fluorescence imaging with the nanoscale resolution of cryogenic electron tomography. Key to this method is active control over the emissive state of fluorescent labels to ensure sufficient sparsity to localize individual emitters. Recent work has identified fluorescent proteins (FPs) which photoactivate or photoswitch efficiently at cryogenic temperatures, but long on-times due to reduced quantum yield of photobleaching remains a challenge for imaging structures with a high density of localizations. In this work, we explore the photophysical properties of the red photoactivatable FP PAmKate and identify a 2-color process leading to enhanced turn-off of active emitters, improving localization rate. Specifically, after excitation of ground state molecules, we find a transient state forms with a lifetime of ~2 ms under cryogenic conditions which can be bleached by exposure to a second wavelength. We measure the response of the transient state to different wavelengths, demonstrate how this mechanism can be used to improve imaging, and provide a blueprint for study of other FPs at cryogenic temperatures.
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Affiliation(s)
- Davis Perez
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Dara P. Dowlatshahi
- Biosciences Division, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
- Department of Structural Biology, Stanford University, Stanford, California 94305, United States
| | - Christopher A. Azaldegui
- Division of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - T. Bertie Ansell
- Division of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Peter D. Dahlberg
- Division of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - W. E. Moerner
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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3
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Ludvikova L, Simon E, Deygas M, Panier T, Plamont MA, Ollion J, Tebo A, Piel M, Jullien L, Robert L, Le Saux T, Espagne A. Near-infrared co-illumination of fluorescent proteins reduces photobleaching and phototoxicity. Nat Biotechnol 2024; 42:872-876. [PMID: 37537501 PMCID: PMC11180605 DOI: 10.1038/s41587-023-01893-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 06/30/2023] [Indexed: 08/05/2023]
Abstract
Here we present a method to reduce the photobleaching of fluorescent proteins and the associated phototoxicity. It exploits a photophysical process known as reverse intersystem crossing, which we induce by near-infrared co-illumination during fluorophore excitation. This dual illumination method reduces photobleaching effects 1.5-9.2-fold, can be easily implemented on commercial microscopes and is effective in eukaryotic and prokaryotic cells with a wide range of fluorescent proteins.
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Affiliation(s)
- Lucie Ludvikova
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, Paris, France
| | - Emma Simon
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, Paris, France
| | - Mathieu Deygas
- Institut Curie, Paris Sciences et Lettres (PSL) Research University, Centre National de la Recherche Scientifique (CNRS), Paris, France
- Institut Pierre-Gilles de Gennes, PSL Research University, Paris, France
| | - Thomas Panier
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine (IBPS), Laboratoire Jean Perrin (LJP), Paris, France
| | - Marie-Aude Plamont
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, Paris, France
| | | | - Alison Tebo
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, Paris, France
| | - Matthieu Piel
- Institut Curie, Paris Sciences et Lettres (PSL) Research University, Centre National de la Recherche Scientifique (CNRS), Paris, France
- Institut Pierre-Gilles de Gennes, PSL Research University, Paris, France
| | - Ludovic Jullien
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, Paris, France
| | - Lydia Robert
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine (IBPS), Laboratoire Jean Perrin (LJP), Paris, France.
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France.
| | - Thomas Le Saux
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, Paris, France.
| | - Agathe Espagne
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, Paris, France.
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4
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Remmel M, Matthias J, Lincoln R, Keller-Findeisen J, Butkevich AN, Bossi ML, Hell SW. Photoactivatable Xanthone (PaX) Dyes Enable Quantitative, Dual Color, and Live-Cell MINFLUX Nanoscopy. SMALL METHODS 2024:e2301497. [PMID: 38497095 DOI: 10.1002/smtd.202301497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Revised: 02/06/2024] [Indexed: 03/19/2024]
Abstract
The single-molecule localization concept MINFLUX has triggered a reevaluation of the features of fluorophores for attaining nanometer-scale resolution. MINFLUX nanoscopy benefits from temporally controlled fluorescence ("on"/"off") photoswitching. Combined with an irreversible switching behavior, the localization process is expected to turn highly efficient and quantitative data analysis simple. The potential in the recently reported photoactivable xanthone (PaX) dyes is recognized to extend the list of molecular switches used for MINFLUX with 561 nm excitation beyond the fluorescent protein mMaple. The MINFLUX localization success rates of PaX560 , PaX+560, and mMaple are quantitatively compared by analyzing the effective labeling efficiency of endogenously tagged nuclear pore complexes. The PaX dyes prove to be superior to mMaple and on par with the best reversible molecular switches routinely used in single-molecule localization microscopy. Moreover, the rationally designed PaX595 is introduced for complementing PaX560 in dual color 561 nm MINFLUX imaging based on spectral classification and the deterministic, irreversible, and additive-independent nature of PaX photoactivation is showcased in fast live-cell MINFLUX imaging. The PaX dyes meet the demands of MINFLUX for a robust readout of each label position and fill the void of reliable fluorophores dedicated to 561 nm MINFLUX imaging.
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Affiliation(s)
- Michael Remmel
- Department of Optical Nanoscopy, Max Planck Institute for Medical Research, 69120, Heidelberg, Germany
| | - Jessica Matthias
- Department of Optical Nanoscopy, Max Planck Institute for Medical Research, 69120, Heidelberg, Germany
| | - Richard Lincoln
- Department of Optical Nanoscopy, Max Planck Institute for Medical Research, 69120, Heidelberg, Germany
| | - Jan Keller-Findeisen
- Department of NanoBiophotonics, Max Planck Institute for Multidisciplinary Sciences, 37077, Göttingen, Germany
| | - Alexey N Butkevich
- Department of Optical Nanoscopy, Max Planck Institute for Medical Research, 69120, Heidelberg, Germany
- Department of NanoBiophotonics, Max Planck Institute for Multidisciplinary Sciences, 37077, Göttingen, Germany
| | - Mariano L Bossi
- Department of Optical Nanoscopy, Max Planck Institute for Medical Research, 69120, Heidelberg, Germany
- Department of NanoBiophotonics, Max Planck Institute for Multidisciplinary Sciences, 37077, Göttingen, Germany
| | - Stefan W Hell
- Department of Optical Nanoscopy, Max Planck Institute for Medical Research, 69120, Heidelberg, Germany
- Department of NanoBiophotonics, Max Planck Institute for Multidisciplinary Sciences, 37077, Göttingen, Germany
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5
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Renouard E, Nowinska M, Lacombat F, Plaza P, Müller P, Espagne A. Multiscale Transient Absorption Study of the Fluorescent Protein Dreiklang and Two Point Variants Provides Insight into Photoswitching and Nonproductive Reaction Pathways. J Phys Chem Lett 2023:6477-6485. [PMID: 37437305 DOI: 10.1021/acs.jpclett.3c00431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
Dreiklang is a reversibly photoswitchable fluorescent protein used as a probe in advanced fluorescence imaging. It undergoes a unique and still poorly understood photoswitching mechanism based on the reversible addition of a water molecule to the chromophore. We report the first comprehensive study of the dynamics of this reaction by transient absorption spectroscopy from 100 fs to seconds in the original Dreiklang protein and two point variants. The picture that emerges from our work is that of a competition between photoswitching and nonproductive reaction pathways. We found that photoswitching had a low quantum yield of 0.4%. It involves electron transfer from a tyrosine residue (Tyr203) to the chromophore and is completed in 33 ns. Nonproductive deactivation pathways comprise recombination of a charge transfer intermediate, excited-state proton transfer from the chromophore to a histidine residue (His145), and decay to the ground state via micro-/millisecond-lived intermediates.
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Affiliation(s)
- Emilie Renouard
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Magdalena Nowinska
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Fabien Lacombat
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Pascal Plaza
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - Pavel Müller
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Agathe Espagne
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
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6
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Rane L, Wulffele J, Bourgeois D, Glushonkov O, Mantovanelli AMR, Zala N, Byrdin M. Light-Induced Forward and Reverse Intersystem Crossing in Green Fluorescent Proteins at Cryogenic Temperatures. J Phys Chem B 2023. [PMID: 37235526 DOI: 10.1021/acs.jpcb.3c02971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Combining fluorescence and phosphorescence kinetics, we characterize forward and reverse intersystem crossing (FISC and RISC, respectively) between the singlet and triplet manifolds S ↔ T in photoswitchable (rsEGFP2) and non-photoswitchable (EGFP) green fluorescent proteins upon continuous 488 nm laser excitation at cryogenic temperatures (CTs). Both proteins behave very similarly, with T1 absorption spectra showing a visible peak at 490 nm (10 mM-1 cm-1) and a vibrational progression in the near-infrared (720 to 905 nm). The dark lifetime of T1 is 21-24 ms at 100 K and very weakly temperature-dependent up to 180 K. Above 180 K, T1 lifetimes reduce rapidly to few milliseconds as found at room temperature (RT). FISC and RISC quantum yields are 0.3 and 0.1%, respectively, for both proteins. The light-induced RISC channel becomes faster than the dark reversal at power densities as low as 20 W cm-2. We discuss implications for fluorescence (super resolution-) microscopy at CT and RT.
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Affiliation(s)
- Lukas Rane
- Institut de Biologie Structurale, CNRS, Université Grenoble Alpes, CEA, IBS, 38044 Grenoble, France
| | - Jip Wulffele
- Institut de Biologie Structurale, CNRS, Université Grenoble Alpes, CEA, IBS, 38044 Grenoble, France
| | - Dominique Bourgeois
- Institut de Biologie Structurale, CNRS, Université Grenoble Alpes, CEA, IBS, 38044 Grenoble, France
| | - Oleksandr Glushonkov
- Institut de Biologie Structurale, CNRS, Université Grenoble Alpes, CEA, IBS, 38044 Grenoble, France
| | - Angela M R Mantovanelli
- Institut de Biologie Structurale, CNRS, Université Grenoble Alpes, CEA, IBS, 38044 Grenoble, France
| | - Ninon Zala
- Institut de Biologie Structurale, CNRS, Université Grenoble Alpes, CEA, IBS, 38044 Grenoble, France
| | - Martin Byrdin
- Institut de Biologie Structurale, CNRS, Université Grenoble Alpes, CEA, IBS, 38044 Grenoble, France
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7
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Krueger TD, Tang L, Fang C. Delineating Ultrafast Structural Dynamics of a Green-Red Fluorescent Protein for Calcium Sensing. BIOSENSORS 2023; 13:bios13020218. [PMID: 36831983 PMCID: PMC9954042 DOI: 10.3390/bios13020218] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/27/2023] [Accepted: 01/30/2023] [Indexed: 05/14/2023]
Abstract
Fluorescent proteins (FPs) are indispensable tools for noninvasive bioimaging and sensing. Measuring the free cellular calcium (Ca2+) concentrations in vivo with genetically encodable FPs can be a relatively direct measure of neuronal activity due to the complex signaling role of these ions. REX-GECO1 is a recently developed red-green emission and excitation ratiometric FP-based biosensor that achieves a high dynamic range due to differences in the chromophore response to light excitation with and without calcium ions. Using steady-state electronic measurements (UV/Visible absorption and emission), along with time-resolved spectroscopic techniques including femtosecond transient absorption (fs-TA) and femtosecond stimulated Raman spectroscopy (FSRS), the potential energy surfaces of these unique biosensors are unveiled with vivid details. The ground-state structural characterization of the Ca2+-free biosensor via FSRS reveals a more spacious protein pocket that allows the chromophore to efficiently twist and reach a dark state. In contrast, the more compressed cavity within the Ca2+-bound biosensor results in a more heterogeneous distribution of chromophore populations that results in multi-step excited state proton transfer (ESPT) pathways on the sub-140 fs, 600 fs, and 3 ps timescales. These results enable rational design strategies to enlarge the spectral separation between the protonated/deprotonated forms and the Stokes shift leading to a larger dynamic range and potentially higher fluorescence quantum yield, which should be broadly applicable to the calcium imaging and biosensor communities.
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8
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Krueger TD, Tang L, Chen C, Zhu L, Breen IL, Wachter RM, Fang C. To twist or not to twist: From chromophore structure to dynamics inside engineered photoconvertible and photoswitchable fluorescent proteins. Protein Sci 2023; 32:e4517. [PMID: 36403093 PMCID: PMC9793981 DOI: 10.1002/pro.4517] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 10/31/2022] [Accepted: 11/15/2022] [Indexed: 11/21/2022]
Abstract
Green-to-red photoconvertible fluorescent proteins (FPs) are vital biomimetic tools for powerful techniques such as super-resolution imaging. A unique Kaede-type FP named the least evolved ancestor (LEA) enables delineation of the evolutionary step to acquire photoconversion capability from the ancestral green fluorescent protein (GFP). A key residue, Ala69, was identified through several steady-state and time-resolved spectroscopic techniques that allows LEA to effectively photoswitch and enhance the green-to-red photoconversion. However, the inner workings of this functional protein have remained elusive due to practical challenges of capturing the photoexcited chromophore motions in real time. Here, we implemented femtosecond stimulated Raman spectroscopy and transient absorption on LEA-A69T, aided by relevant crystal structures and control FPs, revealing that Thr69 promotes a stronger π-π stacking interaction between the chromophore phenolate (P-)ring and His193 in FP mutants that cannot photoconvert or photoswitch. Characteristic time constants of ~60-67 ps are attributed to P-ring twist as the onset for photoswitching in LEA (major) and LEA-A69T (minor) with photoconversion capability, different from ~16/29 ps in correlation with the Gln62/His62 side-chain twist in ALL-GFP/ALL-Q62H, indicative of the light-induced conformational relaxation preferences in various local environments. A minor subpopulation of LEA-A69T capable of positive photoswitching was revealed by time-resolved electronic spectroscopies with targeted light irradiation wavelengths. The unveiled chromophore structure and dynamics inside engineered FPs in an aqueous buffer solution can be generalized to improve other green-to-red photoconvertible FPs from the bottom up for deeper biophysics with molecular biology insights and powerful bioimaging advances.
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Affiliation(s)
| | - Longteng Tang
- Department of ChemistryOregon State UniversityCorvallisOregonUSA
| | - Cheng Chen
- Department of ChemistryOregon State UniversityCorvallisOregonUSA
| | - Liangdong Zhu
- Department of ChemistryOregon State UniversityCorvallisOregonUSA
| | - Isabella L. Breen
- School of Molecular Sciences, Center for Bioenergy and Photosynthesis, Biodesign Center for Applied Structural DiscoveryArizona State UniversityTempeArizonaUSA
| | - Rebekka M. Wachter
- School of Molecular Sciences, Center for Bioenergy and Photosynthesis, Biodesign Center for Applied Structural DiscoveryArizona State UniversityTempeArizonaUSA
| | - Chong Fang
- Department of ChemistryOregon State UniversityCorvallisOregonUSA
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9
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Thaggard GC, Haimerl J, Park KC, Lim J, Fischer RA, Maldeni Kankanamalage BKP, Yarbrough BJ, Wilson GR, Shustova NB. Metal-Photoswitch Friendship: From Photochromic Complexes to Functional Materials. J Am Chem Soc 2022; 144:23249-23263. [PMID: 36512744 DOI: 10.1021/jacs.2c09879] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Cooperative metal-photoswitch interfaces comprise an application-driven field which is based on strategic coupling of metal cations and organic photochromic molecules to advance the behavior of both components, resulting in dynamic molecular and material properties controlled through external stimuli. In this Perspective, we highlight the ways in which metal-photoswitch interplay can be utilized as a tool to modulate a system's physicochemical properties and performance in a variety of structural motifs, including discrete molecular complexes or cages, as well as periodic structures such as metal-organic frameworks. This Perspective starts with photochromic molecular complexes as the smallest subunit in which metal-photoswitch interactions can occur, and progresses toward functional materials. In particular, we explore the role of the metal-photoswitch relationship for gaining fundamental knowledge of switchable electronic and magnetic properties, as well as in the design of stimuli-responsive sensors, optically gated memory devices, catalysts, and photodynamic therapeutic agents. The abundance of stimuli-responsive systems in the natural world only foreshadows the creative directions that will uncover the full potential of metal-photoswitch interactions in the coming years.
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Affiliation(s)
- Grace C Thaggard
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208, United States
| | - Johanna Haimerl
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208, United States.,Inorganic and Metal-Organic Chemistry, Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, Garching 85748, Germany
| | - Kyoung Chul Park
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208, United States
| | - Jaewoong Lim
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208, United States
| | - Roland A Fischer
- Inorganic and Metal-Organic Chemistry, Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, Garching 85748, Germany
| | - Buddhima K P Maldeni Kankanamalage
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208, United States
| | - Brandon J Yarbrough
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208, United States
| | - Gina R Wilson
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208, United States
| | - Natalia B Shustova
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208, United States
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10
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S A, Joshi P, Mondal PP. Detection of fortunate molecules induce particle resolution shift (PAR-shift) toward single-molecule limit in SMLM: A technique for resolving molecular clusters in cellular system. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:093704. [PMID: 36182464 DOI: 10.1063/5.0101009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Accepted: 08/11/2022] [Indexed: 06/16/2023]
Abstract
Molecules capable of emitting a large number of photons (also known as fortunate molecules) are crucial for achieving a resolution close to single molecule limit (the actual size of a single molecule). We propose a long-exposure single molecule localization microscopy (leSMLM) technique that enables detection of fortunate molecules, which is based on the fact that detecting a relatively small subset of molecules with large photon emission increases its localization precision (∼r0/N). Fortunate molecules have the ability to emit a large burst of photons over a prolonged time (> average blinking lifetime). So, a long exposure time allows the time window necessary to detect these elite molecules. The technique involves the detection of fortunate molecules to generate enough statistics for a quality reconstruction of the target protein distribution in a cellular system. Studies show a significant PArticle Resolution Shift (PAR-shift) of about 6 and 11 nm toward single-molecule-limit (far from diffraction-limit) for an exposure time window of 60 and 90 ms, respectively. In addition, a significant decrease in the fraction of fortunate molecules (single molecules with small localization precision) is observed. Specifically, 8.33% and 3.43% molecules are found to emit in 30-60 ms and >60 ms, respectively, when compared to single molecule localization microscopy (SMLM). The long exposure has enabled better visualization of the Dendra2HA molecular cluster, resolving sub-clusters within a large cluster. Thus, the proposed technique leSMLM facilitates a better study of cluster formation in fixed samples. Overall, leSMLM technique offers a spatial resolution improvement of ~ 10 nm compared to traditional SMLM at the cost of marginally poor temporal resolution.
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Affiliation(s)
- Aravinth S
- Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560012, India
| | - Prakash Joshi
- Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560012, India
| | - Partha Pratim Mondal
- Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560012, India
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11
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Wulffele J, Thédié D, Glushonkov O, Bourgeois D. mEos4b Photoconversion Efficiency Depends on Laser Illumination Conditions Used in PALM. J Phys Chem Lett 2022; 13:5075-5080. [PMID: 35653150 DOI: 10.1021/acs.jpclett.2c00933] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Green-to-red photoconvertible fluorescent proteins (PCFPs) are widely employed as markers in photoactivated localization microscopy (PALM). However, their highly complex photophysical behavior complicates their usage. The fact that only a limited fraction of a PCFP ensemble can form the photoconverted state upon near-UV light illumination, termed photoconversion efficiency (PCE), lowers the achievable spatial resolution in PALM and creates undercounting errors in quantitative counting applications. Here, we show that the PCE of mEos4b is not a fixed property of this PCFP but strongly depends on illumination conditions. Attempts to reduce long-lived blinking in red mEos4b by application of 488 nm light lead to a reduction of the PCE. Furthermore, the PCE of mEos4b strongly depends on the applied 405 nm power density. A refined photophysical model of mEos4b accounts for the observed effects, involving nonlinear green-state photobleaching upon violet light illumination favored by photon absorption by a putative radical dark state.
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Affiliation(s)
- Jip Wulffele
- Institut de Biologie Structurale, Univ. Grenoble Alpes, CNRS, CEA, F-38044 Grenoble, France
| | - Daniel Thédié
- Institut de Biologie Structurale, Univ. Grenoble Alpes, CNRS, CEA, F-38044 Grenoble, France
- University of Edinburgh, Roger Land Building, The King's Buildings, EH9 3FF Edinburgh, United Kingdom
| | - Oleksandr Glushonkov
- Institut de Biologie Structurale, Univ. Grenoble Alpes, CNRS, CEA, F-38044 Grenoble, France
| | - Dominique Bourgeois
- Institut de Biologie Structurale, Univ. Grenoble Alpes, CNRS, CEA, F-38044 Grenoble, France
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12
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Eshun A, Varnavski O, Villabona-Monsalve JP, Burdick RK, Goodson T. Entangled Photon Spectroscopy. Acc Chem Res 2022; 55:991-1003. [PMID: 35312287 DOI: 10.1021/acs.accounts.1c00687] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The enhanced interest in quantum-related phenomena has provided new opportunities for chemists to push the limits of detection and analysis of chemical processes. As some have called this the second quantum revolution, a time has come to apply the rules learned from previous research in quantum phenomena toward new methods and technologies important to chemists. While there has been great interest recently in quantum information science (QIS), the quest to understand how nonclassical states of light interact with matter has been ongoing for more than two decades. Our entry into this field started around this time with the use of materials to produce nonclassical states of light. Here, the process of multiphoton absorption led to photon-number squeezed states of light, where the photon statistics are sub-Poissonian. In addition to the great interest in generating squeezed states of light, there was also interest in the formation of entangled states of light. While much of the effort is still in foundational physics, there are numerous new avenues as to how quantum entanglement can be applied to spectroscopy, imaging, and sensing. These opportunities could have a large impact on the chemical community for a broad spectrum of applications.In this Account, we discuss the use of entangled (or quantum) light for spectroscopy as well as applications in microscopy and interferometry. The potential benefits of the use of quantum light are discussed in detail. From the first experiments in porphyrin dendrimer systems by Dr. Dong-Ik Lee in our group to the measurements of the entangled two photon absorption cross sections of biological systems such as flavoproteins, the usefulness of entangled light for spectroscopy has been illustrated. These early measurements led the way to more advanced measurements of the unique characteristics of both entangled light and the entangled photon absorption cross-section, which provides new control knobs for manipulating excited states in molecules.The first reports of fluorescence-induced entangled processes were in organic chromophores where the entangled photon cross-section was measured. These results would later have widespread impact in applications such as entangled two-photon microscopy. From our design, construction and implementation of a quantum entangled photon excited microscope, important imaging capabilities were achieved at an unprecedented low excitation intensity of 107 photons/s, which is 6 orders of magnitude lower than the excitation level for the classical two-photon image. New reports have also illustrated an advantage of nonclassical light in Raman imaging as well.From a standpoint of more precise measurements, the use of entangled photons in quantum interferometry may offer new opportunities for chemistry research. Experiments that combine molecular spectroscopy and quantum interferometry, by utilizing the correlations of entangled photons in a Hong-Ou-Mandel (HOM) interferometer, have been carried out. The initial experiment showed that the HOM signal is sensitive to the presence of a resonant organic sample placed in one arm of the interferometer. In addition, parameters such as the dephasing time have been obtained with the opportunity for even more advanced phenomenology in the future.
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Affiliation(s)
- Audrey Eshun
- Department of Chemistry, University of Michigan, 930 North UniversityAnn Arbor, Michigan 48103, United States
| | - Oleg Varnavski
- Department of Chemistry, University of Michigan, 930 North UniversityAnn Arbor, Michigan 48103, United States
| | - Juan P. Villabona-Monsalve
- Department of Chemistry, University of Michigan, 930 North UniversityAnn Arbor, Michigan 48103, United States
| | - Ryan K. Burdick
- Department of Chemistry, University of Michigan, 930 North UniversityAnn Arbor, Michigan 48103, United States
| | - Theodore Goodson
- Department of Chemistry, University of Michigan, 930 North UniversityAnn Arbor, Michigan 48103, United States
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13
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Lin CY, Romei MG, Mathews II, Boxer SG. Energetic Basis and Design of Enzyme Function Demonstrated Using GFP, an Excited-State Enzyme. J Am Chem Soc 2022; 144:3968-3978. [PMID: 35200017 PMCID: PMC9014791 DOI: 10.1021/jacs.1c12305] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The past decades have witnessed an explosion of de novo protein designs with a remarkable range of scaffolds. It remains challenging, however, to design catalytic functions that are competitive with naturally occurring counterparts as well as biomimetic or nonbiological catalysts. Although directed evolution often offers efficient solutions, the fitness landscape remains opaque. Green fluorescent protein (GFP), which has revolutionized biological imaging and assays, is one of the most redesigned proteins. While not an enzyme in the conventional sense, GFPs feature competing excited-state decay pathways with the same steric and electrostatic origins as conventional ground-state catalysts, and they exert exquisite control over multiple reaction outcomes through the same principles. Thus, GFP is an "excited-state enzyme". Herein we show that rationally designed mutants and hybrids that contain environmental mutations and substituted chromophores provide the basis for a quantitative model and prediction that describes the influence of sterics and electrostatics on excited-state catalysis of GFPs. As both perturbations can selectively bias photoisomerization pathways, GFPs with fluorescence quantum yields (FQYs) and photoswitching characteristics tailored for specific applications could be predicted and then demonstrated. The underlying energetic landscape, readily accessible via spectroscopy for GFPs, offers an important missing link in the design of protein function that is generalizable to catalyst design.
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Affiliation(s)
- Chi-Yun Lin
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Matthew G Romei
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Irimpan I Mathews
- Stanford Synchrotron Radiation Lightsource, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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14
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Mathis P, Sage E, Byrdin M. Pushing the limits of flash photolysis to unravel the secrets of biological electron and proton transfer. Photochem Photobiol Sci 2022; 21:1533-1544. [DOI: 10.1007/s43630-021-00134-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/05/2021] [Indexed: 11/25/2022]
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15
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Mukherjee S, Jimenez R. Photophysical Engineering of Fluorescent Proteins: Accomplishments and Challenges of Physical Chemistry Strategies. J Phys Chem B 2022; 126:735-750. [DOI: 10.1021/acs.jpcb.1c05629] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Srijit Mukherjee
- JILA, University of Colorado at Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
- Department of Chemistry, University of Colorado at Boulder, 215 UCB, Boulder, Colorado 80309, United States
| | - Ralph Jimenez
- JILA, University of Colorado at Boulder and National Institute of Standards and Technology, 440 UCB, Boulder, Colorado 80309, United States
- Department of Chemistry, University of Colorado at Boulder, 215 UCB, Boulder, Colorado 80309, United States
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16
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Burdick RK, Schatz GC, Goodson T. Enhancing Entangled Two-Photon Absorption for Picosecond Quantum Spectroscopy. J Am Chem Soc 2021; 143:16930-16934. [PMID: 34613733 DOI: 10.1021/jacs.1c09728] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Entangled two-photon absorption (ETPA) is known to create photoinduced transitions with extremely low light intensity, reducing the risk of phototoxicity compared to classical two-photon absorption. Previous works have predicted the ETPA cross-section, σe, to vary inversely with the product of entanglement time (Te) and entanglement area (Ae), i.e., σe ∼ 1/AeTe. The decreasing σe with increasing Te has limited ETPA to fs-scale Te, while ETPA applications for ps-scale spectroscopy have been unexplored. However, we show that spectral-spatial coupling, which reduces Ae as the SPDC bandwidth (σf) decreases, plays a significant role in determining σe when Te > ∼100 fs. We experimentally measured σe for zinc tetraphenylporphyrin at several σf values. For type-I ETPA, σe increases as σf decreases down to 0.1 ps-1. For type-II SPDC, σe is constant for a wide range of σf. With a theoretical analysis of the data, the maximum type-I σe would occur at σf = 0.1 ps-1 (Te = 10 ps). At this maximum, σe is 1 order of magnitude larger than fs-scale σe and 3 orders of magnitude larger than previous predictions of ps-scale σe. By utilizing this spectral-spatial coupling, narrowband type-I ETPA provides a new opportunity to increase the efficiency of measuring nonlinear optical signals and to control photochemical reactions requiring ps temporal precision.
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Affiliation(s)
- Ryan K Burdick
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - George C Schatz
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Theodore Goodson
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
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17
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Henrikus SS, Tassis K, Zhang L, van der Velde JHM, Gebhardt C, Herrmann A, Jung G, Cordes T. Characterization of Fluorescent Proteins with Intramolecular Photostabilization*. Chembiochem 2021; 22:3283-3291. [PMID: 34296494 PMCID: PMC9291837 DOI: 10.1002/cbic.202100276] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 07/02/2021] [Indexed: 11/10/2022]
Abstract
Genetically encodable fluorescent proteins have revolutionized biological imaging in vivo and in vitro. Despite their importance, their photophysical properties, i. e., brightness, count-rate and photostability, are relatively poor compared to synthetic organic fluorophores or quantum dots. Intramolecular photostabilizers were recently rediscovered as an effective approach to improve photophysical properties of organic fluorophores. Here, direct conjugation of triplet-state quenchers or redox-active substances creates high local concentrations of photostabilizer around the fluorophore. In this paper, we screen for effects of covalently linked photostabilizers on fluorescent proteins. We produced a double cysteine mutant (A206C/L221C) of α-GFP for attachment of photostabilizer-maleimides on the β-barrel near the chromophore. Whereas labelling with photostabilizers such as trolox, a nitrophenyl group, and cyclooctatetraene, which are often used for organic fluorophores, had no effect on α-GFP-photostability, a substantial increase of photostability was found upon conjugation to azobenzene. Although the mechanism of the photostabilizing effects remains to be elucidated, we speculate that the higher triplet-energy of azobenzene might be crucial for triplet-quenching of fluorophores in the blue spectral range. Our study paves the way for the development of fluorescent proteins with photostabilizers in the protein barrel by methods such as unnatural amino acid incorporation.
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Affiliation(s)
- Sarah S Henrikus
- Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.,Biophysical Chemistry, Saarland University, Campus Building B2.2, 66123, Saarbrücken, Germany.,current address: Francis Crick Institute, 1 Midland Road, London, NW1 AT1, UK
| | - Konstantinos Tassis
- Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Lei Zhang
- Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Großhadernerstr. 2-4, 82152, München - Planegg-Martinsried, Germany
| | - Jasper H M van der Velde
- Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Christian Gebhardt
- Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Großhadernerstr. 2-4, 82152, München - Planegg-Martinsried, Germany
| | - Andreas Herrmann
- Department of Polymer Chemistry, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.,DWI - Leibniz Institute for Interactive Materials, Forckenbeckstr. 50, 52056, Aachen, Germany
| | - Gregor Jung
- Biophysical Chemistry, Saarland University, Campus Building B2.2, 66123, Saarbrücken, Germany
| | - Thorben Cordes
- Molecular Microscopy Research Group, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.,Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Großhadernerstr. 2-4, 82152, München - Planegg-Martinsried, Germany
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18
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Ramos‐Soriano J, Pérez‐Sánchez A, Ramírez‐Barroso S, Illescas BM, Azmani K, Rodríguez‐Fortea A, Poblet JM, Hally C, Nonell S, García‐Fresnadillo D, Rojo J, Martín N. An Ultra‐Long‐Lived Triplet Excited State in Water at Room Temperature: Insights on the Molecular Design of Tridecafullerenes. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202104223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Javier Ramos‐Soriano
- Department of Organic Chemistry Faculty of Chemistry University Complutense of Madrid Avenida Complutense 28040 Madrid Spain
| | - Alfonso Pérez‐Sánchez
- Department of Organic Chemistry Faculty of Chemistry University Complutense of Madrid Avenida Complutense 28040 Madrid Spain
| | - Sergio Ramírez‐Barroso
- Department of Organic Chemistry Faculty of Chemistry University Complutense of Madrid Avenida Complutense 28040 Madrid Spain
| | - Beatriz M. Illescas
- Department of Organic Chemistry Faculty of Chemistry University Complutense of Madrid Avenida Complutense 28040 Madrid Spain
| | - Khalid Azmani
- Department of Physical and Inorganic Chemistry Rovira i Virgili University Marcel lí Domingo 1 43007 Tarragona Spain
| | - Antonio Rodríguez‐Fortea
- Department of Physical and Inorganic Chemistry Rovira i Virgili University Marcel lí Domingo 1 43007 Tarragona Spain
| | - Josep M. Poblet
- Department of Physical and Inorganic Chemistry Rovira i Virgili University Marcel lí Domingo 1 43007 Tarragona Spain
| | - Cormac Hally
- Institut Químic de Sarrià Universitat Ramon Llull Via Augusta 390 08017 Barcelona Spain
| | - Santi Nonell
- Institut Químic de Sarrià Universitat Ramon Llull Via Augusta 390 08017 Barcelona Spain
| | - David García‐Fresnadillo
- Department of Organic Chemistry Faculty of Chemistry University Complutense of Madrid Avenida Complutense 28040 Madrid Spain
| | - Javier Rojo
- Glycosystems Laboratory, — Chemical Research Institute (IIQ) CSIC—Seville University Avenida Américo Vespucio 49 41092 Sevilla Spain
| | - Nazario Martín
- Department of Organic Chemistry Faculty of Chemistry University Complutense of Madrid Avenida Complutense 28040 Madrid Spain
- IMDEA Nanoscience Institute C/ Faraday 9, Campus de Cantoblanco 28049 Madrid Spain
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19
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Ramos‐Soriano J, Pérez‐Sánchez A, Ramírez‐Barroso S, Illescas BM, Azmani K, Rodríguez‐Fortea A, Poblet JM, Hally C, Nonell S, García‐Fresnadillo D, Rojo J, Martín N. An Ultra-Long-Lived Triplet Excited State in Water at Room Temperature: Insights on the Molecular Design of Tridecafullerenes. Angew Chem Int Ed Engl 2021; 60:16109-16118. [PMID: 33984168 PMCID: PMC8361972 DOI: 10.1002/anie.202104223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 04/27/2021] [Indexed: 12/14/2022]
Abstract
Suitably engineered molecular systems exhibiting triplet excited states with very long lifetimes are important for high-end applications in nonlinear optics, photocatalysis, or biomedicine. We report the finding of an ultra-long-lived triplet state with a mean lifetime of 93 ms in an aqueous phase at room temperature, measured for a globular tridecafullerene with a highly compact glycodendrimeric structure. A series of three tridecafullerenes bearing different glycodendrons and spacers to the C60 units have been synthesized and characterized. UV/Vis spectra and DLS experiments confirm their aggregation in water. Steady-state and time-resolved fluorescence experiments suggest a different degree of inner solvation of the multifullerenes depending on their molecular design. Efficient quenching of the triplet states by O2 but not by waterborne azide anions has been observed. Molecular modelling reveals dissimilar access of the aqueous phase to the internal structure of the tridecafullerenes, differently shielded by the glycodendrimeric shell.
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Grants
- CTQ2017-84327-P Ministerio de Economía, Industria y Competitividad, Gobierno de España
- CTQ2017-83531-R Ministerio de Economía, Industria y Competitividad, Gobierno de España
- CTQ2017-87269-P Ministerio de Economía, Industria y Competitividad, Gobierno de España
- CTQ2017-86265-P Ministerio de Economía, Industria y Competitividad, Gobierno de España
- CTQ2015-71896-REDT Ministerio de Economía, Industria y Competitividad, Gobierno de España
- CTQ2016-78454-C2-1-R Ministerio de Economía, Industria y Competitividad, Gobierno de España
- FPU fellowship Ministerio de Economía, Industria y Competitividad, Gobierno de España
- SEV-2016-0686 Ministerio de Economía, Industria y Competitividad, Gobierno de España
- 2017SGR629 Generalitat de Catalunya
- 2017 FI_B 00617 and 2018 FI_B1 00174 Generalitat de Catalunya
- ICREA ACADEMIA Institució Catalana de Recerca i Estudis Avançats
- Ministerio de Economía, Industria y Competitividad, Gobierno de España
- Generalitat de Catalunya
- Institució Catalana de Recerca i Estudis Avançats
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Affiliation(s)
- Javier Ramos‐Soriano
- Department of Organic ChemistryFaculty of ChemistryUniversity Complutense of MadridAvenida Complutense28040MadridSpain
| | - Alfonso Pérez‐Sánchez
- Department of Organic ChemistryFaculty of ChemistryUniversity Complutense of MadridAvenida Complutense28040MadridSpain
| | - Sergio Ramírez‐Barroso
- Department of Organic ChemistryFaculty of ChemistryUniversity Complutense of MadridAvenida Complutense28040MadridSpain
| | - Beatriz M. Illescas
- Department of Organic ChemistryFaculty of ChemistryUniversity Complutense of MadridAvenida Complutense28040MadridSpain
| | - Khalid Azmani
- Department of Physical and Inorganic ChemistryRovira i Virgili UniversityMarcel lí Domingo 143007TarragonaSpain
| | - Antonio Rodríguez‐Fortea
- Department of Physical and Inorganic ChemistryRovira i Virgili UniversityMarcel lí Domingo 143007TarragonaSpain
| | - Josep M. Poblet
- Department of Physical and Inorganic ChemistryRovira i Virgili UniversityMarcel lí Domingo 143007TarragonaSpain
| | - Cormac Hally
- Institut Químic de SarriàUniversitat Ramon LlullVia Augusta 39008017BarcelonaSpain
| | - Santi Nonell
- Institut Químic de SarriàUniversitat Ramon LlullVia Augusta 39008017BarcelonaSpain
| | - David García‐Fresnadillo
- Department of Organic ChemistryFaculty of ChemistryUniversity Complutense of MadridAvenida Complutense28040MadridSpain
| | - Javier Rojo
- Glycosystems Laboratory, —Chemical Research Institute (IIQ) CSIC—Seville UniversityAvenida Américo Vespucio 4941092SevillaSpain
| | - Nazario Martín
- Department of Organic ChemistryFaculty of ChemistryUniversity Complutense of MadridAvenida Complutense28040MadridSpain
- IMDEA Nanoscience InstituteC/ Faraday 9, Campus de Cantoblanco28049MadridSpain
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20
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Nienhaus K, Nienhaus GU. Fluorescent proteins of the EosFP clade: intriguing marker tools with multiple photoactivation modes for advanced microscopy. RSC Chem Biol 2021; 2:796-814. [PMID: 34458811 PMCID: PMC8341165 DOI: 10.1039/d1cb00014d] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 03/27/2021] [Indexed: 02/04/2023] Open
Abstract
Optical fluorescence microscopy has taken center stage in the exploration of biological structure and dynamics, especially on live specimens, and super-resolution imaging methods continue to deliver exciting new insights into the molecular foundations of life. Progress in the field, however, crucially hinges on advances in fluorescent marker technology. Among these, fluorescent proteins (FPs) of the GFP family are advantageous because they are genetically encodable, so that live cells, tissues or organisms can produce these markers all by themselves. A subclass of them, photoactivatable FPs, allow for control of their fluorescence emission by light irradiation, enabling pulse-chase imaging and super-resolution microscopy. In this review, we discuss FP variants of the EosFP clade that have been optimized by amino acid sequence modification to serve as markers for various imaging techniques. In general, two different modes of photoactivation are found, reversible photoswitching between a fluorescent and a nonfluorescent state and irreversible green-to red photoconversion. First, we describe their basic structural and optical properties. We then summarize recent research aimed at elucidating the photochemical processes underlying photoactivation. Finally, we briefly introduce various advanced imaging methods facilitated by specific EosFP variants, and show some exciting sample applications.
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Affiliation(s)
- Karin Nienhaus
- Institute of Applied Physics, Karlsruhe Institute of Technology 76049 Karlsruhe Germany
| | - Gerd Ulrich Nienhaus
- Institute of Applied Physics, Karlsruhe Institute of Technology 76049 Karlsruhe Germany
- Institute of Nanotechnology, Karlsruhe Institute of Technology 76021 Karlsruhe Germany
- Institute of Biological and Chemical Systems, Karlsruhe Institute of Technology 76021 Karlsruhe Germany
- Department of Physics, University of Illinois at Urbana-Champaign Urbana IL 61801 USA
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21
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Peng B, Dikdan R, Hill SE, Patterson-Orazem AC, Lieberman RL, Fahrni CJ, Dickson RM. Optically Modulated and Optically Activated Delayed Fluorescent Proteins through Dark State Engineering. J Phys Chem B 2021; 125:5200-5209. [PMID: 33978414 DOI: 10.1021/acs.jpcb.1c00649] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Modulating fluorescent protein emission holds great potential for increasing readout sensitivity for applications in biological imaging and detection. Here, we identify and engineer optically modulated yellow fluorescent proteins (EYFP, originally 10C, but renamed EYFP later, and mVenus) to yield new emitters with distinct modulation profiles and unique, optically gated, delayed fluorescence. The parent YFPs are individually modulatable through secondary illumination, depopulating a long-lived dark state to dynamically increase fluorescence. A single point mutation introduced near the chromophore in each of these YFPs provides access to a second, even longer-lived modulatable dark state, while a different double mutant renders EYFP unmodulatable. The naturally occurring dark state in the parent YFPs yields strong fluorescence modulation upon long-wavelength-induced dark state depopulation, allowing selective detection at the frequency at which the long wavelength secondary laser is intensity modulated. Distinct from photoswitches, however, this near IR secondary coexcitation repumps the emissive S1 level from the long-lived triplet state, resulting in optically activated delayed fluorescence (OADF). This OADF results from secondary laser-induced, reverse intersystem crossing (RISC), producing additional nanosecond-lived, visible fluorescence that is delayed by many microseconds after the primary excitation has turned off. Mutation of the parent chromophore environment opens an additional modulation pathway that avoids the OADF-producing triplet state, resulting in a second, much longer-lived, modulatable dark state. These Optically Modulated and Optically Activated Delayed Fluorescent Proteins (OMFPs and OADFPs) are thus excellent for background- and reference-free, high sensitivity cellular imaging, but time-gated OADF offers a second modality for true background-free detection. Our combined structural and spectroscopic data not only gives additional mechanistic details for designing optically modulated fluorescent proteins but also provides the opportunity to distinguish similarly emitting OMFPs through OADF and through their unique modulation spectra.
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Affiliation(s)
- Baijie Peng
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Ryan Dikdan
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Shannon E Hill
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Athéna C Patterson-Orazem
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Raquel L Lieberman
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Christoph J Fahrni
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Robert M Dickson
- School of Chemistry & Biochemistry and Petit Institute for Biosciences and Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
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22
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Fare C, Yuan L, Cordon-Preciado V, Michels JJ, Bearpark MJ, Rich P, van Thor JJ. Radical-Triggered Reaction Mechanism of the Green-to-Red Photoconversion of EosFP. J Phys Chem B 2020; 124:7765-7778. [PMID: 32805110 DOI: 10.1021/acs.jpcb.0c04587] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reaction intermediates in the green-to-red photoconversion of the photochromic fluorescent protein EosFP have been observed using high-intensity continuous blue illumination. An intermediate was identified through light-induced accumulation that continues to convert the green form in subsequent darkness, putatively containing a tyrosyl radical, albeit with anomalously shifted features in both the electronic and FTIR spectra. Lowering the pH to 5.5 significantly delays the decay of this tyrosyl intermediate, which is accompanied by Stark-shifted features in the electronic spectra of reactants and products. Vibrational mode assignments for the high-frequency and fingerprint FTIR spectral regions of the reaction intermediates support a proposed sequence of events where the newly formed Cα═Cβ ethylenic bond precedes modifications on the His-62 imidazole ring and confirms a C═O(NH2) product group on Phe-61. We propose a reaction mechanism that involves tyrosyl generation via singlet excited-state-mediated oxidation which subsequently triggers the covalent reactions by oxidation of the green chromophore.
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Affiliation(s)
- Clyde Fare
- Molecular Biophysics, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.,Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 80 Wood Lane, London SW7 2AZ, United Kingdom
| | - Letong Yuan
- Molecular Biophysics, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Violeta Cordon-Preciado
- Molecular Biophysics, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Jasper J Michels
- Division of Molecular Electronics, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Michael J Bearpark
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, 80 Wood Lane, London SW7 2AZ, United Kingdom
| | - Peter Rich
- Department of Structural and Molecular Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Jasper J van Thor
- Molecular Biophysics, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
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23
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Gorbachev DA, Petrusevich EF, Kabylda AM, Maksimov EG, Lukyanov KA, Bogdanov AM, Baranov MS, Bochenkova AV, Mishin AS. A General Mechanism of Green-to-Red Photoconversions of GFP. Front Mol Biosci 2020; 7:176. [PMID: 32850965 PMCID: PMC7405548 DOI: 10.3389/fmolb.2020.00176] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Accepted: 07/07/2020] [Indexed: 12/20/2022] Open
Abstract
Here we dissect the phenomena of oxidative and reductive green-to-red photoconversion of the Green Fluorescent Protein. We characterize distinct orange- and red-emitting forms (λabs/λem = 490/565 nm; λabs/λem = 535/600 nm) arising during the Enhanced Green Fluorescent Protein (EGFP) photoconversion under low-oxygen conditions in the presence of reductants. These forms spectroscopically differ from that observed previously in oxidative redding (λabs/λem = 575/607 nm). We also report on a new green-emitting state (λabs/λem = 405/525 nm), which is formed upon photoconversion under the low-oxygen conditions. Based on the spectral properties of these forms, their light-independent time evolution, and the high-level computational studies, we provide a structural basis for various photoproducts. Under the low-oxygen conditions, the neutral quinoid-like structure formed via a two-electron oxidation process is found to be a key intermediate and a most likely candidate for the novel green-emitting state of the chromophore. The observed large Stokes shift is traced to the formation of the zwitterionic form of the chromophore in the excited state. Subsequently, this form undergoes two types of cyclization reactions, resulting in the formation of either the orange-emitting state (λabs/λem = 490/565 nm) or the red-emitting form (λabs/λem = 535/600 nm). The T65G mutant lacks one of the proposed cyclization pathways and, indeed, the photoconverted T65G EGFP exhibits a single orange-emitting state. In oxidative redding, the red-emitting state resembles the structure of the chromophore from asFP595 (λabs/λem = 572/595 nm), which is directly formed upon two-electron oxidation and deprotonation bypassing the formation of the quinoid-like structure. Our results disclose a general “oxidative” mechanism of various green-to-red photoconversions of EGFP, providing a link between oxidative redding and the photoconversion under low-oxygen conditions.
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Affiliation(s)
- Dmitry A Gorbachev
- Center of Life Sciences, Skolkovo Institute of Science and Technology, Moscow, Russia
| | | | - Adil M Kabylda
- Department of Chemistry, Lomonosov Moscow State University, Moscow, Russia
| | - Eugene G Maksimov
- Department of Biophysics, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Konstantin A Lukyanov
- Center of Life Sciences, Skolkovo Institute of Science and Technology, Moscow, Russia
| | - Alexey M Bogdanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Mikhail S Baranov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.,Institute of Translational Medicine, Pirogov Russian National Research Medical University, Moscow, Russia
| | | | - Alexander S Mishin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
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De Zitter E, Ridard J, Thédié D, Adam V, Lévy B, Byrdin M, Gotthard G, Van Meervelt L, Dedecker P, Demachy I, Bourgeois D. Mechanistic Investigations of Green mEos4b Reveal a Dynamic Long-Lived Dark State. J Am Chem Soc 2020; 142:10978-10988. [PMID: 32463688 DOI: 10.1021/jacs.0c01880] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Green-to-red photoconvertible fluorescent proteins (PCFPs) are key players in advanced microscopy schemes such as photoactivated localization microscopy (PALM). Whereas photoconversion and red-state blinking in PCFPs have been studied intensively, their green-state photophysical behavior has received less attention. Yet dark states in green PCFPs can become strongly populated in PALM schemes and exert an indirect but considerable influence on the quality of data recorded in the red channel. Furthermore, green-state photoswitching in PCFPs can be used directly for PALM and has been engineered to design highly efficient reversibly switchable fluorescent proteins (RSFPs) amenable to various nanoscopy schemes. Here, we demonstrate that green mEos4b efficiently switches to a long-lived dark state through cis-trans isomerization of its chromophore, as do most RSFPs. However, by combining kinetic crystallography, molecular dynamics simulations, and Raman spectroscopy, we find that the dark state in green mEos4b is much more dynamic than that seen in switched-off green IrisFP, a biphotochromic PCFP engineered from the common EosFP parent. Our data suggest that H-bonding patterns maintained by the chromophore in green PCFPs and RSFPs in both their on- and off-states collectively control photoswitching quantum yields. The reduced number of H-bonds maintained by the dynamic dark chromophore in green mEos4b thus largely accounts for the observed lower switching contrast as compared to that of IrisFP. We also compare the long-lived dark states reached from green and red mEos4b, on the basis of their X-ray structures and Raman signatures. Altogether, these data provide a unifying picture of the complex photophysics of PCFPs and RSFPs.
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Affiliation(s)
- Elke De Zitter
- Department of Chemistry, KU Leuven, Heverlee 3001, Belgium
| | - Jacqueline Ridard
- Institut de Chimie Physique UMR8000, Université Paris-Saclay, CNRS, Orsay 91405, France
| | - Daniel Thédié
- Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, Grenoble 38044, France
| | - Virgile Adam
- Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, Grenoble 38044, France
| | - Bernard Lévy
- Institut de Chimie Physique UMR8000, Université Paris-Saclay, CNRS, Orsay 91405, France
| | - Martin Byrdin
- Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, Grenoble 38044, France
| | - Guillaume Gotthard
- Structural Biology Group, European Synchrotron Radiation Facility, Grenoble 38000, France
| | | | - Peter Dedecker
- Department of Chemistry, KU Leuven, Heverlee 3001, Belgium
| | - Isabelle Demachy
- Institut de Chimie Physique UMR8000, Université Paris-Saclay, CNRS, Orsay 91405, France
| | - Dominique Bourgeois
- Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, Grenoble 38044, France
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25
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Isselstein M, Zhang L, Glembockyte V, Brix O, Cosa G, Tinnefeld P, Cordes T. Self-Healing Dyes-Keeping the Promise? J Phys Chem Lett 2020; 11:4462-4480. [PMID: 32401520 DOI: 10.1021/acs.jpclett.9b03833] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Self-healing dyes have emerged as a new promising class of fluorescent labels. They consist of two units, a fluorescent dye and a photostabilizer. The latter heals whenever the fluorescent dye is in danger of taking a reaction pathway toward photobleaching. We describe the underlying concepts and summarize the developmental history and state-of-the-art, including latest applications in high-resolution microscopy, live-cell, and single-molecule imaging. We further discuss remaining limitations, which are (i) lower photostabilization of most self-healing dyes when compared to solution additives, (ii) limited mechanistic understanding on the influence of the biochemical environment and molecular oxygen on self-healing, and (iii) the lack of cheap and facile bioconjugation strategies. Finally, we provide ideas on how to further advance self-healing dyes, show new data on redox blinking caused by double-stranded DNA, and highlight forthcoming work on intramolecular photostabilization of fluorescent proteins.
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Affiliation(s)
- Michael Isselstein
- Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Großhadernerstr. 2-4, 82152 Planegg-Martinsried, Germany
| | - Lei Zhang
- Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Großhadernerstr. 2-4, 82152 Planegg-Martinsried, Germany
| | - Viktorija Glembockyte
- Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, Haus E 81377 München, Germany
- Department of Chemistry and Quebec Centre for Applied Materials (QCAM), McGill University, 801 Sherbrooke Street W., H3A 0B8 Montreal, Quebec, Canada
| | - Oliver Brix
- Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Großhadernerstr. 2-4, 82152 Planegg-Martinsried, Germany
| | - Gonzalo Cosa
- Department of Chemistry and Quebec Centre for Applied Materials (QCAM), McGill University, 801 Sherbrooke Street W., H3A 0B8 Montreal, Quebec, Canada
| | - Philip Tinnefeld
- Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, Haus E 81377 München, Germany
| | - Thorben Cordes
- Physical and Synthetic Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Großhadernerstr. 2-4, 82152 Planegg-Martinsried, Germany
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26
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Chavez J, Ceresa L, Kitchner E, Kimball J, Shtoyko T, Fudala R, Borejdo J, Gryczynski Z, Gryczynski I. On the possibility of direct triplet state excitation of indole. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2020; 208:111897. [PMID: 32447191 DOI: 10.1016/j.jphotobiol.2020.111897] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Revised: 02/26/2020] [Accepted: 05/13/2020] [Indexed: 11/18/2022]
Abstract
We studied the luminescence properties of indole in poly (vinyl alcohol) (PVA) film. The indole molecules are effectively immobilized in this polymer film and display both fluorescence and phosphorescence emission at room temperature. We noticed that the phosphorescence of indole in PVA film can be effectively excited at a longer wavelength than its typical singlet to triplet population route involving intersystem crossing. The maximum of the phosphorescence excitation is about 410 nm which corresponds to the energy of indole's triplet state. Interestingly, the phosphorescence anisotropy excited with the longer wavelength (405 nm) is positive and reaches a value of about 0.25 in contrast to the phosphorescence anisotropy excited within the indole singlet absorption spectrum (290 nm), which is negative. Very different temperature dependences have been observed for fluorescence and phosphorescence of indole in PVA film. While fluorescence depends minimally, the phosphorescence decreases with temperature dramatically. The fluorescence lifetime was measured to be a single component 4.78 ns while the intensity weighted average phosphorescence lifetime with 290 nm and 405 nm excitations were 6.57 and 5.62 ms, respectively. We believe that the possibility of the excitation of indole phosphorescence in the blue region of visible light and its high anisotropy opens a new avenue for future protein studies.
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Affiliation(s)
- Jose Chavez
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA
| | - Luca Ceresa
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA
| | - Emma Kitchner
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA
| | - Joseph Kimball
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA.
| | - Tanya Shtoyko
- Department of Chemistry and Biochemistry, The University of Texas at Tyler, Tyler, TX 75799, USA
| | - Rafal Fudala
- Department of Microbiology, Immunology, and Genetics, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Julian Borejdo
- Department of Microbiology, Immunology, and Genetics, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Zygmunt Gryczynski
- Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA; Department of Microbiology, Immunology, and Genetics, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Ignacy Gryczynski
- Department of Microbiology, Immunology, and Genetics, Center for Fluorescence Technologies and Nanomedicine, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
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27
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Romei MG, Lin CY, Mathews II, Boxer SG. Electrostatic control of photoisomerization pathways in proteins. Science 2020; 367:76-79. [PMID: 31896714 DOI: 10.1126/science.aax1898] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 06/04/2019] [Accepted: 10/31/2019] [Indexed: 12/23/2022]
Abstract
Rotation around a specific bond after photoexcitation is central to vision and emerging opportunities in optogenetics, super-resolution microscopy, and photoactive molecular devices. Competing roles for steric and electrostatic effects that govern bond-specific photoisomerization have been widely discussed, the latter originating from chromophore charge transfer upon excitation. We systematically altered the electrostatic properties of the green fluorescent protein chromophore in a photoswitchable variant, Dronpa2, using amber suppression to introduce electron-donating and electron-withdrawing groups to the phenolate ring. Through analysis of the absorption (color), fluorescence quantum yield, and energy barriers to ground- and excited-state isomerization, we evaluate the contributions of sterics and electrostatics quantitatively and demonstrate how electrostatic effects bias the pathway of chromophore photoisomerization, leading to a generalized framework to guide protein design.
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Affiliation(s)
- Matthew G Romei
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA.
| | - Chi-Yun Lin
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA.
| | - Irimpan I Mathews
- Stanford Synchrotron Radiation Lightsource, Menlo Park, CA 94025, USA
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
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28
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Vetschera P, Mishra K, Fuenzalida-Werner JP, Chmyrov A, Ntziachristos V, Stiel AC. Characterization of Reversibly Switchable Fluorescent Proteins in Optoacoustic Imaging. Anal Chem 2018; 90:10527-10535. [DOI: 10.1021/acs.analchem.8b02599] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Paul Vetschera
- Institute of Biological and Medical Imaging, Helmholtz Zentrum München, D-85764 Neuherberg, Germany
- Chair of Biological Imaging, Technische Universität München, D-80333 München, Germany
| | - Kanuj Mishra
- Institute of Biological and Medical Imaging, Helmholtz Zentrum München, D-85764 Neuherberg, Germany
| | | | - Andriy Chmyrov
- Institute of Biological and Medical Imaging, Helmholtz Zentrum München, D-85764 Neuherberg, Germany
- Center for Translational Cancer Research, Technische Universität München, D-81675 München, Germany
| | - Vasilis Ntziachristos
- Institute of Biological and Medical Imaging, Helmholtz Zentrum München, D-85764 Neuherberg, Germany
- Chair of Biological Imaging, Technische Universität München, D-80333 München, Germany
- Center for Translational Cancer Research, Technische Universität München, D-81675 München, Germany
| | - Andre C. Stiel
- Institute of Biological and Medical Imaging, Helmholtz Zentrum München, D-85764 Neuherberg, Germany
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