1
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Diaz S, McCamant DW. Diffuse Reflectance-Based Femtosecond Stimulated Raman Spectroscopy of Opaque Suspensions. Anal Chem 2023; 95:15856-15860. [PMID: 37852269 PMCID: PMC10620773 DOI: 10.1021/acs.analchem.3c02491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 10/03/2023] [Indexed: 10/20/2023]
Abstract
By augmentation of the collection optics utilized in transmission-based femtosecond stimulated Raman spectroscopy (FSRS), two novel diffuse reflectance-based femtosecond stimulated Raman spectroscopy (drFSRS) techniques were developed. These techniques were then used to collect the Raman spectra of opaque systems, those being cyclohexane-intercalated poly(tetrafluoroethylene) microbeads and ethanol in 1% intralipid solutions. The resulting drFSRS data from the cyclohexane:PTFE system show significant distortion of the depolarization ratio of the 803 cm-1 cyclohexane peak, indicating a loss of incident pump:probe polarization in a scattering environment. The drFSRS data from the ethanol in 1% intralipid solution demonstrate less signal strength but equal spectral resolution when compared to transmission-based FSRS of the same sample. The results presented in this Technical Note demonstrate the current capabilities of collecting stimulated Raman spectra of opaque systems using drFSRS.
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Affiliation(s)
- Steven
A. Diaz
- University of Rochester, Department of Chemistry Rochester, New York, New York 14534, United States
| | - David W. McCamant
- University of Rochester, Department of Chemistry Rochester, New York, New York 14534, United States
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2
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Knorr J, Sülzner N, Geissler B, Spies C, Grandjean A, Kutta RJ, Jung G, Nuernberger P. Ultrafast transient absorption and solvation of a super-photoacid in acetoneous environments. PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES : OFFICIAL JOURNAL OF THE EUROPEAN PHOTOCHEMISTRY ASSOCIATION AND THE EUROPEAN SOCIETY FOR PHOTOBIOLOGY 2022; 21:2179-2192. [PMID: 36178669 DOI: 10.1007/s43630-022-00287-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 08/08/2022] [Indexed: 12/13/2022]
Abstract
The phenomenon of photoacidity, i.e., an increase in acidity by several orders of magnitude upon electronic excitation, is frequently encountered in aromatic alcohols capable of transferring a proton to a suitable acceptor. A promising new class of neutral super-photoacids based on pyranine derivatives has been shown to exhibit pronounced solvatochromic effects. To disclose the underlying mechanisms contributing to excited-state proton transfer (ESPT) and the temporal characteristics of solvation and ESPT, we scrutinize the associated ultrafast dynamics of the strongest photoacid of this class, namely tris(1,1,1,3,3,3-hexafluoropropan-2-yl)8-hydroxypyrene-1,3,6-trisulfonate, in acetoneous environment, thereby finding experimental evidence for ESPT even under these adverse conditions for proton transfer. Juxtaposing results from time-correlated single-photon counting and femtosecond transient absorption measurements combined with a complete decomposition of all signal components, i.e., absorption of ground and excited states as well as stimulated emission, we disclose dynamics of solvation, rotational diffusion, and radiative relaxation processes in acetone and identify the relevant steps of ESPT along with the associated time scales.
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Affiliation(s)
- Johannes Knorr
- Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany.,Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Paul-Gordan-Straße 6, 91052, Erlangen, Germany
| | - Niklas Sülzner
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780, Bochum, Germany.,Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Bastian Geissler
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, 95053, Regensburg, Germany.,Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Christian Spies
- Biophysikalische Chemie, Universität des Saarlandes, 66123, Saarbrücken, Germany.,Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Alexander Grandjean
- Biophysikalische Chemie, Universität des Saarlandes, 66123, Saarbrücken, Germany
| | - Roger Jan Kutta
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, 95053, Regensburg, Germany
| | - Gregor Jung
- Biophysikalische Chemie, Universität des Saarlandes, 66123, Saarbrücken, Germany
| | - Patrick Nuernberger
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, 95053, Regensburg, Germany. .,Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany.
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3
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Tang L, Fang C. Photoswitchable Fluorescent Proteins: Mechanisms on Ultrafast Timescales. Int J Mol Sci 2022; 23:6459. [PMID: 35742900 PMCID: PMC9223536 DOI: 10.3390/ijms23126459] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 06/06/2022] [Accepted: 06/08/2022] [Indexed: 12/15/2022] Open
Abstract
The advancement of super-resolution imaging (SRI) relies on fluorescent proteins with novel photochromic properties. Using light, the reversibly switchable fluorescent proteins (RSFPs) can be converted between bright and dark states for many photocycles and their emergence has inspired the invention of advanced SRI techniques. The general photoswitching mechanism involves the chromophore cis-trans isomerization and proton transfer for negative and positive RSFPs and hydration-dehydration for decoupled RSFPs. However, a detailed understanding of these processes on ultrafast timescales (femtosecond to millisecond) is lacking, which fundamentally hinders the further development of RSFPs. In this review, we summarize the current progress of utilizing various ultrafast electronic and vibrational spectroscopies, and time-resolved crystallography in investigating the on/off photoswitching pathways of RSFPs. We show that significant insights have been gained for some well-studied proteins, but the real-time "action" details regarding the bidirectional cis-trans isomerization, proton transfer, and intermediate states remain unclear for most systems, and many other relevant proteins have not been studied yet. We expect this review to lay the foundation and inspire more ultrafast studies on existing and future engineered RSFPs. The gained mechanistic insights will accelerate the rational development of RSFPs with enhanced two-way switching rate and efficiency, better photostability, higher brightness, and redder emission colors.
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Affiliation(s)
- Longteng Tang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331-4003, USA
| | - Chong Fang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331-4003, USA
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4
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Walker AR, Wu B, Meisner J, Fayer MD, Martínez TJ. Proton Transfer from a Photoacid to a Water Wire: First Principles Simulations and Fast Fluorescence Spectroscopy. J Phys Chem B 2021; 125:12539-12551. [PMID: 34743512 DOI: 10.1021/acs.jpcb.1c07254] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Proton transfer reactions are ubiquitous in chemistry, especially in aqueous solutions. We investigate photoinduced proton transfer between the photoacid 8-hydroxypyrene-1,3,6-trisulfonate (HPTS) and water using fast fluorescence spectroscopy and ab initio molecular dynamics simulations. Photoexcitation causes rapid proton release from the HPTS hydroxyl. Previous experiments on HPTS/water described the progress from photoexcitation to proton diffusion using kinetic equations with two time constants. The shortest time constant has been interpreted as protonated and photoexcited HPTS evolving into an "associated" state, where the proton is "shared" between the HPTS hydroxyl and an originally hydrogen bonded water. The longer time constant has been interpreted as indicating evolution to a "solvent separated" state where the shared proton undergoes long distance diffusion. In this work, we refine the previous experimental results using very pure HPTS. We then use excited state ab initio molecular dynamics to elucidate the detailed molecular mechanism of aqueous excited state proton transfer in HPTS. We find that the initial excitation results in rapid rearrangement of water, forming a strong hydrogen bonded network (a "water wire") around HPTS. HPTS then deprotonates in ≤3 ps, resulting in a proton that migrates back and forth along the wire before localizing on a single water molecule. We find a near linear relationship between the emission wavelength and proton-HPTS distance over the simulated time scale, suggesting that the emission wavelength can be used as a ruler for the proton distance. Our simulations reveal that the "associated" state corresponds to a water wire with a mobile proton and that the diffusion of the proton away from this water wire (to a generalized "solvent-separated" state) corresponds to the longest experimental time constant.
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Affiliation(s)
- Alice R Walker
- Department of Chemistry, Stanford University, Stanford, California 94305, United States.,The PULSE Institute, Stanford University, Stanford, California 94305, United States.,SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Boning Wu
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Jan Meisner
- Department of Chemistry, Stanford University, Stanford, California 94305, United States.,The PULSE Institute, Stanford University, Stanford, California 94305, United States.,SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - Michael D Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Todd J Martínez
- Department of Chemistry, Stanford University, Stanford, California 94305, United States.,The PULSE Institute, Stanford University, Stanford, California 94305, United States.,SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
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5
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Grandjean A, Pérez Lustres JL, Jung G. Solvent‐Controlled Intermolecular Proton‐Transfer Follows an Irreversible Eigen‐Weller Model from fs to ns. CHEMPHOTOCHEM 2021. [DOI: 10.1002/cptc.202100177] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Alexander Grandjean
- Biophysikalische Chemie Universität des Saarlandes FR Chemie, Gebäude B2 2, Postfach 151150 D-66041 Saarbrücken Germany
| | - J. Luis Pérez Lustres
- Current Address: Fachbereich Physik Freie Universität Berlin Arnimallee 14 14195 Berlin Germany
- Experimental work conducted at former affiliation Physikalisch Chemisches Institut Universität Heidelberg Im Neuenheimer Feld 229 D-69120 Heidelberg Germany
| | - Gregor Jung
- Biophysikalische Chemie Universität des Saarlandes FR Chemie, Gebäude B2 2, Postfach 151150 D-66041 Saarbrücken Germany
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6
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Santos EM, Sheng W, Esmatpour Salmani R, Tahmasebi Nick S, Ghanbarpour A, Gholami H, Vasileiou C, Geiger JH, Borhan B. Design of Large Stokes Shift Fluorescent Proteins Based on Excited State Proton Transfer of an Engineered Photobase. J Am Chem Soc 2021; 143:15091-15102. [PMID: 34516091 DOI: 10.1021/jacs.1c05039] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The incredible potential for fluorescent proteins to revolutionize biology has inspired the development of a variety of design strategies to address an equally broad range of photophysical characteristics, depending on potential applications. Of these, fluorescent proteins that simultaneously exhibit high quantum yield, red-shifted emission, and wide separation between excitation and emission wavelengths (Large Stokes Shift, LSS) are rare. The pursuit of LSS systems has led to the formation of a complex, obtained from the marriage of a rationally engineered protein (human cellular retinol binding protein II, hCRBPII) and different fluorogenic molecules, capable of supporting photobase activity. The large increase in basicity upon photoexcitation leads to protonation of the fluorophore in the excited state, dramatically red-shifting its emission, leading to an LSS protein/fluorophore complex. Essential for selective photobase activity is the intimate involvement of the target protein structure and sequence that enables Excited State Proton Transfer (ESPT). The potential power and usefulness of the strategy was demonstrated in live cell imaging of human cell lines.
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Affiliation(s)
- Elizabeth M Santos
- Michigan State University, Department of Chemistry, East Lansing, Michigan 48824, United States
| | - Wei Sheng
- Michigan State University, Department of Chemistry, East Lansing, Michigan 48824, United States
| | | | - Setare Tahmasebi Nick
- Michigan State University, Department of Chemistry, East Lansing, Michigan 48824, United States
| | - Alireza Ghanbarpour
- Michigan State University, Department of Chemistry, East Lansing, Michigan 48824, United States
| | - Hadi Gholami
- Michigan State University, Department of Chemistry, East Lansing, Michigan 48824, United States
| | - Chrysoula Vasileiou
- Michigan State University, Department of Chemistry, East Lansing, Michigan 48824, United States
| | - James H Geiger
- Michigan State University, Department of Chemistry, East Lansing, Michigan 48824, United States
| | - Babak Borhan
- Michigan State University, Department of Chemistry, East Lansing, Michigan 48824, United States
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7
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Chiariello MG, Donati G, Raucci U, Perrella F, Rega N. Structural Origin and Vibrational Fingerprints of the Ultrafast Excited State Proton Transfer of the Pyranine-Acetate Complex in Aqueous Solution. J Phys Chem B 2021; 125:10273-10281. [PMID: 34472354 DOI: 10.1021/acs.jpcb.1c05590] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The excited state proton transfer (ESPT) reaction from the photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS or pyranine) to an acetate molecule has been investigated in explicit aqueous solution via excited state ab initio molecular dynamics simulations based on hybrid quantum/molecular mechanics (QM/MM) potentials. In all the trajectories, the direct proton transfer has been observed in the excited state within 1 ps. We find that the initial structural configuration extracted from the ground state distribution strongly affects the ESPT kinetics. Indeed, the relative orientation of the proton donor-acceptor pair and the presence of a water molecule hydrogen bonded to the phenolic acid group of the pyranine are the key factors to facilitate the ESPT. Furthermore, we analyze the vibrational fingerprints of the ESPT reaction, reproducing the blue shift of the acetate CO stretching (COac), from 1666 to 1763 cm-1 testifying the transformation of acetate to acetic acid. Finally, our findings suggest that the acetate CC stretching (CCac) is also sensitive to the progress of the ESPT reaction. The CCac stretching is indeed ruled by the two vibrational modes (928 and 1426 cm-1), that in the excited state are alternately activated when the proton is shared or bound to the donor/acceptor, respectively.
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Affiliation(s)
- Maria Gabriella Chiariello
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, I-80126 Napoli, Italy
| | - Greta Donati
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, I-80126 Napoli, Italy
| | - Umberto Raucci
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, I-80126 Napoli, Italy
| | - Fulvio Perrella
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, I-80126 Napoli, Italy
| | - Nadia Rega
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, I-80126 Napoli, Italy.,CRIB Center for Advanced Biomaterials for Healthcare, Piazzale Tecchio, 80-80125 Napoli, Italy
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8
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Chiariello MG, Raucci U, Donati G, Rega N. Water-Mediated Excited State Proton Transfer of Pyranine-Acetate in Aqueous Solution: Vibrational Fingerprints from Ab Initio Molecular Dynamics. J Phys Chem A 2021; 125:3569-3578. [PMID: 33900071 PMCID: PMC8279639 DOI: 10.1021/acs.jpca.1c00692] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
In this work, we
simulate the excited state proton transfer (ESPT)
reaction involving the pyranine photoacid and an acetate molecule
as proton acceptor, connected by a bridge water molecule. We employ
ab initio molecular dynamics combined with an hybrid quantum/molecular
mechanics (QM/MM) framework. Furthermore, a time-resolved vibrational
analysis based on the wavelet-transform allows one to identify two
low frequency vibrational modes that are fingerprints of the ESPT
event: a ring wagging and ring breathing. Their composition suggests
their key role in optimizing the structure of the proton donor–acceptor
couple and promoting the ESPT event. We find that the choice of the
QM/MM partition dramatically affects the photoinduced reactivity of
the system. The QM subspace was gradually extended including the water
molecules directly interacting with the pyranine–water–acetate
system. Indeed, the ESPT reaction takes place when the hydrogen bond
network around the reactive system is taken into account at full QM
level.
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Affiliation(s)
- Maria Gabriella Chiariello
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, I-80126 Napoli, Italy
| | - Umberto Raucci
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, I-80126 Napoli, Italy
| | - Greta Donati
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, I-80126 Napoli, Italy
| | - Nadia Rega
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, I-80126 Napoli, Italy.,Centro Interdipartimentale di Ricerca sui Biomateriali (CRIB) Piazzale Tecchio, Largo Barsanti e Matteucci, I-80125 Napoli, Italy
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9
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Lee C, Chung S, Song H, Rhee YM, Lee E, Joo T. Excited State Proton Transfer of Quinone Cyanine 9: Implications on the Origin of Super‐Photoacidity. CHEMPHOTOCHEM 2020. [DOI: 10.1002/cptc.202000254] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Changmin Lee
- Department of Chemistry Pohang University of Science and Technology (POSTECH) Pohang 37673 Republic of Korea
| | - Seyoung Chung
- Department of Chemistry Pohang University of Science and Technology (POSTECH) Pohang 37673 Republic of Korea
| | - Hayoung Song
- Department of Chemistry Pohang University of Science and Technology (POSTECH) Pohang 37673 Republic of Korea
| | - Young Min Rhee
- Department of Chemistry Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141 Republic of Korea
| | - Eunsung Lee
- Department of Chemistry Pohang University of Science and Technology (POSTECH) Pohang 37673 Republic of Korea
| | - Taiha Joo
- Department of Chemistry Pohang University of Science and Technology (POSTECH) Pohang 37673 Republic of Korea
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10
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Raucci U, Chiariello MG, Rega N. Modeling Excited-State Proton Transfer to Solvent: A Dynamics Study of a Super Photoacid with a Hybrid Implicit/Explicit Solvent Model. J Chem Theory Comput 2020; 16:7033-7043. [PMID: 33112132 PMCID: PMC8016186 DOI: 10.1021/acs.jctc.0c00782] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
![]()
The rapid growth of time-resolved
spectroscopies and the theoretical
advances in ab initio molecular dynamics (AIMD) pave the way to look
at the real-time molecular motion following the electronic excitation.
Here, we exploited the capabilities of AIMD combined with a hybrid
implicit/explicit model of solvation to investigate the ultrafast
excited-state proton transfer (ESPT) reaction of a super photoacid,
known as QCy9, in water solution. QCy9 transfers a proton to a water
solvent molecule within 100 fs upon the electronic excitation in aqueous
solution, and it is the strongest photoacid reported in the literature
so far. Because of the ultrafast kinetics, it has been experimentally
hypothesized that the ESPT escapes the solvent dynamics control (Huppert
et al., J. Photochem. Photobiol. A2014,277, 90). The sampling of the solvent configuration
space on the ground electronic state is the first key step toward
the simulation of the ESPT event. Therefore, several configurations
in the Franck–Condon region, describing an average solvation,
were chosen as starting points for the excited-state dynamics. In
all cases, the excited-state evolution spontaneously leads to the
proton transfer event, whose rate is strongly dependent on the hydrogen
bond network around the proton acceptor solvent molecule. Our study
revealed that the explicit representation at least of three solvation
shells around the proton acceptor molecule is necessary to stabilize
the excess proton. Furthermore, the analysis of the solvent molecule
motions in proximity of the reaction site suggested that even in the
case of the strongest photoacid, the ESPT is actually assisted by
the solvation dynamics of the first and second solvation shells of
the water accepting molecule.
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Affiliation(s)
- Umberto Raucci
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S.Angelo, via Cintia, I-80126 Napoli, Italy
| | - Maria Gabriella Chiariello
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S.Angelo, via Cintia, I-80126 Napoli, Italy
| | - Nadia Rega
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S.Angelo, via Cintia, I-80126 Napoli, Italy.,CRIB, Centro Interdipartimentale di Ricerca sui Biomateriali, Piazzale Tecchio, I-80125 Napoli, Italy
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11
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Chiariello MG, Donati G, Rega N. Time-Resolved Vibrational Analysis of Excited State Ab Initio Molecular Dynamics to Understand Photorelaxation: The Case of the Pyranine Photoacid in Aqueous Solution. J Chem Theory Comput 2020; 16:6007-6013. [PMID: 32955870 PMCID: PMC8011922 DOI: 10.1021/acs.jctc.0c00810] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
![]()
We
present a novel time-resolved vibrational analysis for studying
photoinduced nuclear relaxation. Generalized modes velocities are
defined from ab initio molecular dynamics and wavelet transformed,
providing the time localization of vibrational signals in the electronic
excited state. The photoexcited pyranine in aqueous solution is presented
as a case study. The transient and sequential activation of the simulated
vibrational signals is in good agreement with vibrational dynamics
obtained from femtosecond stimulated Raman spectroscopy data.
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Affiliation(s)
- Maria Gabriella Chiariello
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M. S. Angelo, via Cintia, I-80126 Napoli, Italy
| | - Greta Donati
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M. S. Angelo, via Cintia, I-80126 Napoli, Italy
| | - Nadia Rega
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M. S. Angelo, via Cintia, I-80126 Napoli, Italy.,CRIB Center for Advanced Biomaterials for Healthcare, Largo Barsanti e Matteucci, I-80125 Napoli, Italy
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12
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Mbarak H, Ghahrizjani RT, Hamidi SM, Mohajerani E, Zaatar Y. Reversible and tunable photochemical switch based on plasmonic structure. Sci Rep 2020; 10:5110. [PMID: 32198452 PMCID: PMC7083958 DOI: 10.1038/s41598-020-62058-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 03/08/2020] [Indexed: 11/29/2022] Open
Abstract
For the first time, pyranine (8-hydroxypyrene-1,3,6-trisulfonate, HPTS) is studied for realizing active plasmonic control, which is attracted considerable attention owing to its unique photophysical and photochemical properties. We have used this photoacid (HPTS) as an active surrounding medium that can be optically controlled and used for modulating plasmon resonances. In this paper, the fabrication of 2D-plasmonic grating coated by thin film of HPTS exposed to UV irradiation is reported. By switching the UV light on and off, the HPTS thin film maintains an excited-state proton transfer (ESPT) process followed by green fluorescence resulting in a plasmonic redshift caused by the variation of the refractive index. Furthermore, this photochemical active medium has also played another important role in plasmonic sensing, in which the emission-based response of HPTS thin film in 2D-plasmonic grating to water vapor upon photoexcitation is demonstrated, for both s and p polarizations. This tunable, flexible and reversible light-driven system will enhance the development of active plasmonic structures and will have a great influence on many fields such as, biochemical optical sensors and all-optical plasmonic circuits.
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Affiliation(s)
- H Mbarak
- Laser and plasma Research Institute, Shahid Beheshti University, G. C. Tehran, Iran.,Faculty of Sciences 2, LPA, Lebanese University, BP 90656, Jdeidet, Lebanon
| | - R Taheri Ghahrizjani
- Laser and plasma Research Institute, Shahid Beheshti University, G. C. Tehran, Iran
| | - S M Hamidi
- Laser and plasma Research Institute, Shahid Beheshti University, G. C. Tehran, Iran.
| | - E Mohajerani
- Laser and plasma Research Institute, Shahid Beheshti University, G. C. Tehran, Iran.
| | - Y Zaatar
- Faculty of Sciences 2, LPA, Lebanese University, BP 90656, Jdeidet, Lebanon
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13
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Krueger TD, Boulanger SA, Zhu L, Tang L, Fang C. Discovering a rotational barrier within a charge-transfer state of a photoexcited chromophore in solution. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2020; 7:024901. [PMID: 32161777 PMCID: PMC7056454 DOI: 10.1063/1.5143441] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 02/18/2020] [Indexed: 05/15/2023]
Abstract
Methylation occurs in a myriad of systems with protective and regulatory functions. 8-methoxypyrene-1,3,6-trisulfonate (MPTS), a methoxy derivative of a photoacid, serves as a model system to study effects of methylation on the excited state potential energy landscape. A suite of spectroscopic techniques including transient absorption, wavelength-tunable femtosecond stimulated Raman spectroscopy (FSRS), and fluorescence quantum yield measurements via steady-state electronic spectroscopy reveal the energy dissipation pathways of MPTS following photoexcitation. Various solvents enable a systematic characterization of the H-bonding interaction, viscosity, and dynamic solvation that influence the ensuing relaxation pathways. The formation of a charge-transfer state out of the Franck-Condon region occurs on the femtosecond-to-picosecond solvation timescale before encountering a rotational barrier. The rotational relaxation correlates with the H-bond donating strength of solvent, while the rotational time constant lengthens as solvent viscosity increases. Time-resolved excited-state FSRS, aided by quantum calculations, provides crucial structural dynamics knowledge and reveals the sulfonate groups playing a dominant role during solvation. Several prominent vibrational motions of the pyrene ring backbone help maneuver the population toward the more fluorescent state. These ultrafast correlated electronic and nuclear motions ultimately govern the fate of the photoexcited chromophore in solution. Overall, MPTS in water displays the highest probability to fluoresce, while the aprotic and more viscous dimethyl sulfoxide enhances the nonradiative pathways. These mechanistic insights may apply robustly to other photoexcited chromophores that do not undergo excited-state proton transfer or remain trapped in a broad electronic state and also provide design principles to control molecular optical responses with site-specific atomic substitution.
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Affiliation(s)
- Taylor D. Krueger
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, USA
| | - Sean A. Boulanger
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, USA
| | - Liangdong Zhu
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, USA
| | - Longteng Tang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, USA
| | - Chong Fang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, USA
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14
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Fang C, Tang L. Mapping Structural Dynamics of Proteins with Femtosecond Stimulated Raman Spectroscopy. Annu Rev Phys Chem 2020; 71:239-265. [PMID: 32075503 DOI: 10.1146/annurev-physchem-071119-040154] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The structure-function relationships of biomolecules have captured the interest and imagination of the scientific community and general public since the field of structural biology emerged to enable the molecular understanding of life processes. Proteins that play numerous functional roles in cellular processes have remained in the forefront of research, inspiring new characterization techniques. In this review, we present key theoretical concepts and recent experimental strategies using femtosecond stimulated Raman spectroscopy (FSRS) to map the structural dynamics of proteins, highlighting the flexible chromophores on ultrafast timescales. In particular, wavelength-tunable FSRS exploits dynamic resonance conditions to track transient-species-dependent vibrational motions, enabling rational design to alter functions. Various ways of capturing excited-state chromophore structural snapshots in the time and/or frequency domains are discussed. Continuous development of experimental methodologies, synergistic correlation with theoretical modeling, and the expansion to other nonequilibrium, photoswitchable, and controllable protein systems will greatly advance the chemical, physical, and biological sciences.
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Affiliation(s)
- Chong Fang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA;
| | - Longteng Tang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA;
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15
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Fang C, Tang L, Chen C. Unveiling coupled electronic and vibrational motions of chromophores in condensed phases. J Chem Phys 2019; 151:200901. [PMID: 31779327 DOI: 10.1063/1.5128388] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The quest for capturing molecular movies of functional systems has motivated scientists and engineers for decades. A fundamental understanding of electronic and nuclear motions, two principal components of the molecular Schrödinger equation, has the potential to enable the de novo rational design for targeted functionalities of molecular machines. We discuss the development and application of a relatively new structural dynamics technique, femtosecond stimulated Raman spectroscopy with broadly tunable laser pulses from the UV to near-IR region, in tracking the coupled electronic and vibrational motions of organic chromophores in solution and protein environments. Such light-sensitive moieties hold broad interest and significance in gaining fundamental knowledge about the intramolecular and intermolecular Hamiltonian and developing effective strategies to control macroscopic properties. Inspired by recent experimental and theoretical advances, we focus on the in situ characterization and spectroscopy-guided tuning of photoacidity, excited state proton transfer pathways, emission color, and internal conversion via a conical intersection.
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Affiliation(s)
- Chong Fang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Longteng Tang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
| | - Cheng Chen
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA
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Hong DL, Luo YH, He XT, Zheng ZY, Su S, Wang JY, Wang C, Chen C, Sun BW. Unraveling the Mechanisms of the Excited-State Intermolecular Proton Transfer (ESPT) for a D-π-A Molecular Architecture. Chemistry 2019; 25:8805-8812. [PMID: 31054168 DOI: 10.1002/chem.201900856] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2019] [Revised: 04/25/2019] [Indexed: 11/10/2022]
Abstract
Precise revealing the mechanisms of excited-state intermolecular proton transfer (ESPT) and the corresponding geometrical relaxation upon photoexcitation and photoionization remains a formidable challenge. In this work, the compound (E)-4-(((4H-1,2,4-triazol-4-yl)imino)methyl)-2,6-dimethoxyphenol (TIMDP) adopting a D-π-A molecular architecture featuring a significant intramolecular charge transfer (ICT) effect has been designed. With the presence of perchloric acid (35 %), TIMDP can be dissolved through the formation of a HClO4 -H2 O-OH(TIMDP)-N(TIMDP) hydrogen-bonding bridge. At the ground state, the ICT effect is dominant, giving birth to crystals of TIMDP. Upon external stimuli (e.g., UV light irradiation, electro field), the excited state is achieved, which weakens the ICT effect, and significantly promotes the ESPT effect along the hydrogen-bonding bridge, resulting in crystals of [HTIMDP]+ ⋅[H2 O]⋅[ClO4 ]- . As a consequence, the mechanisms of the ESPT can be investigated, which distorted the D-π-A molecular architecture, tuned the emission color with the largest Stokes shift of 242 nm, and finally, high photoluminescence quantum yields (12 %) and long fluorescence lifetimes (8.6 μs) have achieved. These results not only provide new insight into ESPT mechanisms, but also open a new avenue for the design of efficient ESPT emitters.
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Affiliation(s)
- Dan-Li Hong
- School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189, P.R. China
| | - Yang-Hui Luo
- School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189, P.R. China
| | - Xiao-Tong He
- School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189, P.R. China
| | - Zi-Yue Zheng
- School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189, P.R. China
| | - Shan Su
- School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189, P.R. China
| | - Jia-Ying Wang
- School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189, P.R. China
| | - Cong Wang
- School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189, P.R. China
| | - Chen Chen
- School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189, P.R. China
| | - Bai-Wang Sun
- School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189, P.R. China
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17
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Tang L, Fang C. Nitration of Tyrosine Channels Photoenergy through a Conical Intersection in Water. J Phys Chem B 2019; 123:4915-4928. [PMID: 31094198 DOI: 10.1021/acs.jpcb.9b03464] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Nitration of tyrosine occurs under oxidative stress in vivo. The product, 3-nitrotyrosine (3NY), has a dramatically decreased quantum yield and can be used as a molecular ruler. In this study, femtosecond transient absorption spectroscopy and quantum calculations were implemented to elucidate the photoinduced relaxation processes of anionic 3NY in water. Upon 400 nm excitation into an excited electronic state with notable charge-transfer (CT) character, a barrierless nitro-twisting motion rapidly (<100 fs) guides the chromophore into an adjacent twisted intramolecular CT state, therein reaching a sloped S1/S0 conical intersection on the ∼100 fs time scale. Once in the hot ground state, excess energy is further released through vibrational cooling with biexponential time constants of ∼140 and 680 fs in water. Nitro back-twisting occurs on longer time scales (∼1.1 and 9 ps in water), returning the system to original ground state. Systematic evaluations of excited-state potential energies of anionic 3NY were performed by density functional theory (DFT) and time-dependent DFT calculations, showing that intersystem crossing (ISC) from the first singlet state (S1) to the first or second triplet state (T1 or T2) is unlikely. Inclusion of an explicit water molecule in calculations leads to improved mapping of the excited-state energy ordering of the second singlet state (S2) and T2, further diminishing ISC probability from S1 and favoring an ultrafast internal conversion to S0. These results provide deep insights into the highly efficient nonradiative decay of anionic 3NY in aqueous solution, with nitro-site-specific information that can help infer the characterization and potential optogenetic control of 3NY in protein environment.
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Affiliation(s)
- Longteng Tang
- Department of Chemistry , Oregon State University , 153 Gilbert Hall , Corvallis , Oregon 97331-4003 , United States
| | - Chong Fang
- Department of Chemistry , Oregon State University , 153 Gilbert Hall , Corvallis , Oregon 97331-4003 , United States
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18
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Taylor MA, Zhu L, Rozanov ND, Stout KT, Chen C, Fang C. Delayed vibrational modulation of the solvated GFP chromophore into a conical intersection. Phys Chem Chem Phys 2019; 21:9728-9739. [PMID: 31032505 DOI: 10.1039/c9cp01077g] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Green fluorescent protein (GFP) has revolutionized bioimaging and life sciences. Its successes have inspired modification of the chromophore structure and environment to tune emission properties, but outside the protein cage, the chromophore is essentially non-fluorescent. In this study, we employ the tunable femtosecond stimulated Raman spectroscopy (FSRS) and transient absorption (TA) to map the energy dissipation pathways of GFP model chromophore (HBDI) in basic aqueous solution. Strategic tuning of the Raman pump to 550 nm exploits the stimulated emission band to enhance excited state vibrational motions as HBDI navigates the non-equilibrium potential energy landscape to pass through a conical intersection. The time-resolved FSRS uncovers prominent anharmonic couplings between a global out-of-plane bending mode of ∼227 cm-1 and two modes at ∼866 and 1572 cm-1 before HBDI reaches the twisted intramolecular charge transfer (TICT) state on the ∼3 ps time scale. Remarkably, the wavelet transform analysis reveals a ∼500 fs delayed onset of the coupling peaks, in correlation with the emergence of an intermediate charge-separated state en route to the TICT state. This mechanism is corroborated by the altered coupling matrix for the HBDI Raman modes in the 50% (v/v) water-glycerol mixture, and a notable lengthening of the picosecond time constant. The real-time molecular "movie" of the general rotor-like HBDI isomerization reaction following photoexcitation represents a significant advance in comprehending the photochemical reaction pathways of the solvated GFP chromophore, therefore providing a crucial foundation to enable rational design of diverse nanomachines from efficient molecular rotors to bright fluorescent probes.
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Affiliation(s)
- Miles A Taylor
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331-4003, USA.
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19
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Chen C, Zhu L, Baranov MS, Tang L, Baleeva NS, Smirnov AY, Yampolsky IV, Solntsev KM, Fang C. Photoinduced Proton Transfer of GFP-Inspired Fluorescent Superphotoacids: Principles and Design. J Phys Chem B 2019; 123:3804-3821. [DOI: 10.1021/acs.jpcb.9b03201] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Cheng Chen
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Liangdong Zhu
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Mikhail S. Baranov
- Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya 16/10, Moscow 117997, Russia
- Pirogov Russian National Research Medical University, Ostrovitianov 1, Moscow 117997, Russia
| | - Longteng Tang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Nadezhda S. Baleeva
- Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya 16/10, Moscow 117997, Russia
| | - Alexander Yu. Smirnov
- Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya 16/10, Moscow 117997, Russia
| | - Ilia V. Yampolsky
- Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya 16/10, Moscow 117997, Russia
- Pirogov Russian National Research Medical University, Ostrovitianov 1, Moscow 117997, Russia
| | - Kyril M. Solntsev
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
- New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | - Chong Fang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
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Jana S, Yapamanu AL, Umapathy S. Unraveling structural dynamics in isoenergetic excited S1 and multi-excitonic 1(TT) states of 9,10-bis(phenylethynyl)anthracene (BPEA) in solution via ultrafast Raman loss spectroscopy. Phys Chem Chem Phys 2019; 21:14341-14349. [DOI: 10.1039/c8cp06658b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ultrafast Raman loss spectroscopy provides a direct evidence for the structural changes that occur during the evolution from the S1 to the 1(TT) state of BPEA in solution.
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Affiliation(s)
- Sanjib Jana
- Department of Instrumentation and Applied Physics
- Bangalore 560012
- India
| | | | - Siva Umapathy
- Department of Instrumentation and Applied Physics
- Bangalore 560012
- India
- Department of Inorganic and Physical Chemistry and Applied Physics
- Bangalore 560012
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21
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Tang L, Zhu L, Wang Y, Fang C. Uncovering the Hidden Excited State toward Fluorescence of an Intracellular pH Indicator. J Phys Chem Lett 2018; 9:4969-4975. [PMID: 30111103 DOI: 10.1021/acs.jpclett.8b02281] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Intracellular pH (pHi) imaging is of paramount importance for life sciences. In this work, we implement the ultrafast electronic and stimulated Raman spectroscopies to unravel the fluorescence mechanism of an excitation-ratiometric pHi indicator in basic aqueous solution. After photoexcitation of the pHi indicator HPTS, a hidden charge-transfer (CT) state following the locally excited (LE) state is uncovered as an essential step prior to fluorescence and this LE → CT transition is gated by ultrafast solvation dynamics. A 835 cm-1 intermolecular vibrational mode is identified to potentially facilitate the CT-state formation on the 700 fs time scale. Dynamic correlation with the other excited-state Raman marker bands suggests that the transition between transient electronic states is aided by solvation events mostly in the molecular plane of HPTS. These vivid structural dynamics insights can enable the rational design of more efficient and bright pHi indicators in an H-bonding environment with controllable properties.
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Affiliation(s)
- Longteng Tang
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
| | - Liangdong Zhu
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
| | - Yanli Wang
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
| | - Chong Fang
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
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Excited State Structural Evolution of a GFP Single-Site Mutant Tracked by Tunable Femtosecond-Stimulated Raman Spectroscopy. Molecules 2018; 23:molecules23092226. [PMID: 30200474 PMCID: PMC6225354 DOI: 10.3390/molecules23092226] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 08/29/2018] [Accepted: 08/31/2018] [Indexed: 12/31/2022] Open
Abstract
Tracking vibrational motions during a photochemical or photophysical process has gained momentum, due to its sensitivity to the progression of reaction and change of environment. In this work, we implemented an advanced ultrafast vibrational technique, femtosecond-stimulated Raman spectroscopy (FSRS), to monitor the excited state structural evolution of an engineered green fluorescent protein (GFP) single-site mutant S205V. This mutation alters the original excited state proton transfer (ESPT) chain. By strategically tuning the Raman pump to different wavelengths (i.e., 801, 539, and 504 nm) to achieve pre-resonance with transient excited state electronic bands, the characteristic Raman modes of the excited protonated (A*) chromophore species and intermediate deprotonated (I*) species can be selectively monitored. The inhomogeneous distribution/population of A* species go through ESPT with a similar ~300 ps time constant, confirming that bridging a water molecule to protein residue T203 in the ESPT chain is the rate-limiting step. Some A* species undergo vibrational cooling through high-frequency motions on the ~190 ps time scale. At early times, a portion of the largely protonated A* species could also undergo vibrational cooling or return to the ground state with a ~80 ps time constant. On the photoproduct side, a ~1330 cm−1 delocalized motion is observed, with dispersive line shapes in both the Stokes and anti-Stokes FSRS with a pre-resonance Raman pump, which indicates strong vibronic coupling, as the mode could facilitate the I* species to reach a relatively stable state (e.g., the main fluorescent state) after conversion from A*. Our findings disentangle the contributions of various vibrational motions active during the ESPT reaction, and offer new structural dynamics insights into the fluorescence mechanisms of engineered GFPs and other analogous autofluorescent proteins.
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23
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Chen C, Zhu LD, Fang C. Femtosecond stimulated Raman line shapes: Dependence on resonance conditions of pump and probe pulses. CHINESE J CHEM PHYS 2018. [DOI: 10.1063/1674-0068/31/cjcp1805125] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Cheng Chen
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon, 97331-4003, USA
| | - Liang-dong Zhu
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon, 97331-4003, USA
- Department of Physics, Oregon State University, 301 Weniger Hall, Corvallis, Oregon, 97331-6507, USA
| | - Chong Fang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon, 97331-4003, USA
- Department of Physics, Oregon State University, 301 Weniger Hall, Corvallis, Oregon, 97331-6507, USA
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Abstract
As one of the most fundamental processes, excited-state proton transfer (ESPT) plays a major role in both chemical and biological systems. In the past several decades, experimental and theoretical studies on ESPT systems have attracted considerable attention because of their tremendous potential in fluorescent probes, biological imaging, white-light-emitting materials, and organic optoelectronic materials. ESPT is related to fluorescence properties and usually occurs on an ultrafast time scale at or below 100 fs. Consequently, steady-state and femtosecond time-resolved absorption, fluorescence, and vibrational spectra have been used to explore the mechanism of ESPT. However, based on previous experimental studies, direct information, such as transition state geometries, energy barrier, and potential energy surface (PES) of the ESPT reaction, is difficult to obtain. These data are important for unravelling the detailed mechanism of ESPT reaction and can be obtained from state-of-the-art ab initio excited-state calculations. In recent years, an increasing number of experimental and theoretical studies on the detailed mechanism of ESPT systems have led to tremendous progress. This Account presents the recent advances in theoretical studies, mainly those from our group. We focus on the cases where the theoretical studies are of great importance and indispensable, such as resolving the debate on the stepwise and concerted mechanism of excited-state double proton transfer (ESDPT), revealing the sensing mechanism of ESPT chemosensors, illustrating the effect of intermolecular hydrogen bonding on the excited-state intramolecular proton transfer (ESIPT) reaction, investigating the fluorescence quenching mechanism of ESPT systems by twisting process, and determining the size of the solute·(solvent) n cluster for the solvent-assisted ESPT reaction. Through calculation of vertical excitation energies, optimization of excited-state geometries, and construction of PES of the ESPT reactions, we provide modifications to experimentally proposed mechanisms or completely new mechanism. Our proposed new and inspirational mechanisms based on theoretical studies can successfully explain the previous experimental results; some of the mechanisms have been further confirmed by experimental studies and provided guidance for researchers to design new ESPT chemosensors. Determination of the energy barrier from an accurate PES is the key to explore the ESPT mechanism with theoretical methods. This approach becomes complicated when the charge transfer state is involved for time-dependent density functional theory (TDDFT) method and optimally tuned range-separated TDDFT provides an alternative way. To unveil the driving force of ESPT reaction, the excited-state molecular dynamics combined with the intrinsic reaction coordinate calculations can be employed. These advanced approaches should be used for further studies on ESPT systems.
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Affiliation(s)
- Panwang Zhou
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian 116023, Liaoning, China
| | - Keli Han
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian 116023, Liaoning, China
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Fang C, Tang L, Oscar BG, Chen C. Capturing Structural Snapshots during Photochemical Reactions with Ultrafast Raman Spectroscopy: From Materials Transformation to Biosensor Responses. J Phys Chem Lett 2018; 9:3253-3263. [PMID: 29799757 DOI: 10.1021/acs.jpclett.8b00373] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Chemistry studies the composition, structure, properties, and transformation of matter. A mechanistic understanding of the pertinent processes is required to translate fundamental knowledge into practical applications. The current development of ultrafast Raman as a powerful time-resolved vibrational technique, particularly femtosecond stimulated Raman spectroscopy (FSRS), has shed light on the structure-energy-function relationships of various photosensitive systems. This Perspective reviews recent work incorporating optical innovations, including the broad-band up-converted multicolor array (BUMA) into a tunable FSRS setup, and demonstrates its resolving power to watch metal speciation and photolysis, leading to high-quality thin films, and fluorescence modulation of chimeric protein biosensors for calcium ion imaging. We discuss advantages of performing FSRS in the mixed time-frequency domain and present strategies to delineate mechanisms by tracking low-frequency modes and systematically modifying chemical structures with specific functional groups. These unique insights at the chemical-bond level have started to enable the rational design and precise control of functional molecular machines in optical, materials, energy, and life sciences.
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Affiliation(s)
- Chong Fang
- Department of Chemistry , Oregon State University , 153 Gilbert Hall , Corvallis , Oregon 97331 , United States
| | - Longteng Tang
- Department of Chemistry , Oregon State University , 153 Gilbert Hall , Corvallis , Oregon 97331 , United States
| | - Breland G Oscar
- Department of Chemistry , Oregon State University , 153 Gilbert Hall , Corvallis , Oregon 97331 , United States
| | - Cheng Chen
- Department of Chemistry , Oregon State University , 153 Gilbert Hall , Corvallis , Oregon 97331 , United States
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Tang L, Wang Y, Zhu L, Kallio K, Remington SJ, Fang C. Photoinduced proton transfer inside an engineered green fluorescent protein: a stepwise-concerted-hybrid reaction. Phys Chem Chem Phys 2018; 20:12517-12526. [PMID: 29708241 DOI: 10.1039/c8cp01907j] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photoactivated proton transfer (PT) wire is responsible for the glow of green fluorescent protein (GFP), which is crucial for bioimaging and biomedicine. In this work, a new GFP-S65T/S205V double mutant is developed from wild-type GFP in which the PT wire is significantly modified. We implement femtosecond transient absorption (fs-TA) and femtosecond stimulated Raman spectroscopy (FSRS) to delineate the PT process in action. The excited state proton transfer proceeds on the ∼110 ps timescale, which infers that the distance of one key link (water to T203) in the PT wire of GFP-S205V is shortened by the extra S65T mutation. The rise of an imidazolinone ring deformation mode at ∼871 cm-1 in FSRS further suggests that this PT reaction is in a concerted manner. A ∼4 ps component prior to large-scale proton dissociation through the PT wire is also retrieved, indicative of some small-scale proton motions and heavy-atom rearrangement in the vicinity of the chromophore. Our work provides deep insights into the novel hybrid PT mechanism in engineered GFP and demonstrates the power of tunable FSRS methodology in tracking ultrafast photoreactions with the desirable structural specificity in physiological environments.
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Affiliation(s)
- Longteng Tang
- Oregon State University, Department of Chemistry, 263 Linus Pauling Science Centre (lab), 153 Gilbert Hall (office), Corvallis, OR 97331, USA.
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27
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Bilal SM, Kayal S, Sanju KS, Adithya Lakshmanna Y. Femtosecond Time-Resolved Raman Spectroscopy Reveals Structural Evidence for meta Effect in Stilbenols. J Phys Chem A 2018; 122:4601-4608. [PMID: 29683672 DOI: 10.1021/acs.jpca.7b12339] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The meta effect in substituted aromatics plays a crucial role in their excited-state photophysical properties. Meta-substituted hydroxyarenes such as naphthols, stilbenols, and chromophoric constituents of green fluorescent proteins show unusual photoacidity and enhanced fluorescence lifetime and quantum yield when compared to their para-derivatives. Variation in the excited state features of the meta-derivatives when compared to the para-derivatives in stilbenols has been attributed to the enhanced torsional barrier for interconversion between the planar and the twisted perpendicular forms. Herein, we employed femtosecond time-resolved Raman spectroscopy to provide the direct structural evidence for the enhanced torsional barrier in meta-stilbenol. The Raman band profiles of the olefinic C═C stretch related to the torsional motion are found to decay with time constants of ∼750 and ∼13 ps in meta-stilbenol and para-stilbenol respectively, unraveling the structural evidence for the observed enhanced photoacidity originating from enhanced rates of excited-state proton transfer. Further, time-resolved fluorescence measurements are performed to elucidate the relaxation pathways of the excited states of the stilbenols.
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Affiliation(s)
- Syed M Bilal
- School of Chemistry , Indian Institute of Science Education and Research Thiruvananthapuram , Vithura, Thiruvananthapuram 695551 , India
| | - Surajit Kayal
- Department of Inorganic and Physical Chemistry , Indian Institute of Science , Bangalore 560012 , India
| | - Krishnankutty S Sanju
- School of Chemistry , Indian Institute of Science Education and Research Thiruvananthapuram , Vithura, Thiruvananthapuram 695551 , India
| | - Y Adithya Lakshmanna
- School of Chemistry , Indian Institute of Science Education and Research Thiruvananthapuram , Vithura, Thiruvananthapuram 695551 , India
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Tang L, Wang Y, Zhu L, Lee C, Fang C. Correlated Molecular Structural Motions for Photoprotection after Deep-UV Irradiation. J Phys Chem Lett 2018; 9:2311-2319. [PMID: 29672054 DOI: 10.1021/acs.jpclett.8b00999] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Exposure to ultraviolet (UV) light could cause photodamage to biomolecular systems and degrade optoelectronic devices. To mitigate such detrimental effects from the bottom up, we strategically select a photosensitive molecule pyranine and implement femtosecond electronic and Raman spectroscopies to elucidate its ultrafast photoprotection mechanisms in solution. Our results show that pyranine undergoes excited-state proton transfer in water, while this process is blocked in methanol regardless of excitation wavelengths (267, 400 nm). After 267 nm irradiation, the molecule relaxes from a higher lying electronic state into a lower lying singlet state with a <300 fs time constant, followed by solvation events. Transient Raman marker bands exhibit different patterns of intensity dynamics and frequency shift that elucidate the real-time interplay among conformational motions, photochemical reaction, and vibrational cooling after excitation. More energetic photons are revealed to selectively enhance certain relaxation pathways. These mechanistic findings offer new guidelines to improve the UV tolerance and stability of the engineered functional molecules in materials and life sciences.
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Affiliation(s)
- Longteng Tang
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
| | - Yanli Wang
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
| | - Liangdong Zhu
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
| | - Che Lee
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
| | - Chong Fang
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
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29
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Chiariello MG, Rega N. Exploring Nuclear Photorelaxation of Pyranine in Aqueous Solution: an Integrated Ab-Initio Molecular Dynamics and Time Resolved Vibrational Analysis Approach. J Phys Chem A 2018; 122:2884-2893. [DOI: 10.1021/acs.jpca.7b12371] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Maria Gabriella Chiariello
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S.Angelo, via Cintia, I-80126 Napoli, Italy
| | - Nadia Rega
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S.Angelo, via Cintia, I-80126 Napoli, Italy
- Interdisciplinary Research Centre on Biomaterials (CRIB) Università di Napoli Federico II, Piazzale Tecchio 80, I-80125, Napoli, Italy
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30
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Louant O, Champagne B, Liégeois V. Investigation of the Electronic Excited-State Equilibrium Geometries of Three Molecules Undergoing ESIPT: A RI-CC2 and TDDFT Study. J Phys Chem A 2018; 122:972-984. [DOI: 10.1021/acs.jpca.7b10881] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Orian Louant
- Laboratoire de Chimie Théorique,
UCPTS, Namur Institute of Structured Matter, Université de Namur, rue de Bruxelles 61, B-5000 Namur, Belgium
| | - Benoît Champagne
- Laboratoire de Chimie Théorique,
UCPTS, Namur Institute of Structured Matter, Université de Namur, rue de Bruxelles 61, B-5000 Namur, Belgium
| | - Vincent Liégeois
- Laboratoire de Chimie Théorique,
UCPTS, Namur Institute of Structured Matter, Université de Namur, rue de Bruxelles 61, B-5000 Namur, Belgium
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31
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Awasthi AA, Singh PK. Excited-State Proton Transfer on the Surface of a Therapeutic Protein, Protamine. J Phys Chem B 2017; 121:10306-10317. [PMID: 29032681 DOI: 10.1021/acs.jpcb.7b07151] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Proton transfer reactions on biosurfaces play an important role in a myriad of biological processes. Herein, the excited-state proton transfer reaction of 8-hydroxypyrene-1,3,6-trisulfonate (HPTS) has been investigated in the presence of an important therapeutic protein, Protamine (PrS), using ground-state absorption, steady-state, and detailed time-resolved emission measurements. HPTS forms a 1:1 complex with Protamine with a high association constant of 2.6 × 104 M-1. The binding of HPTS with Protamine leads to a significant modulation in the ground-state prototropic equilibrium causing a downward shift of 1.1 unit in the acidity constant (pKa). In contrast to a large number of reports of slow proton transfer of HPTS on biosurfaces, interestingly, HPTS registers a faster proton transfer event in the presence of Protamine as compared to that of even the bulk aqueous buffer medium. Furthermore, the dimensionality of the proton diffusion process is also significantly reduced on the surface of Protamine that is in contrast to the behavior of HPTS in the bulk aqueous buffer medium, where the proton diffusion process is three-dimensional. The effect of ionic strength on the binding of HPTS toward PrS suggests a predominant role of electrostatic interaction between anionic HPTS and cationic Protamine, which is further supported by molecular docking simulations which predict that the most preferable binding site for HPTS on the surface of Protamine is surrounded by multiple cationic arginine residues.
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Affiliation(s)
| | - Prabhat K Singh
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre , Mumbai 400085, India.,Homi Bhabha National Institute , Training School Complex, Anushaktinagar, Mumbai 400094, India
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32
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Kowalewski M, Fingerhut BP, Dorfman KE, Bennett K, Mukamel S. Simulating Coherent Multidimensional Spectroscopy of Nonadiabatic Molecular Processes: From the Infrared to the X-ray Regime. Chem Rev 2017; 117:12165-12226. [DOI: 10.1021/acs.chemrev.7b00081] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Markus Kowalewski
- Department
of Chemistry and Department of Physics and Astronomy, University of California, Irvine, California 92697-2025, United States
| | - Benjamin P. Fingerhut
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, D-12489 Berlin, Germany
| | - Konstantin E. Dorfman
- State
Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Kochise Bennett
- Department
of Chemistry and Department of Physics and Astronomy, University of California, Irvine, California 92697-2025, United States
| | - Shaul Mukamel
- Department
of Chemistry and Department of Physics and Astronomy, University of California, Irvine, California 92697-2025, United States
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33
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Oscar BG, Chen C, Liu W, Zhu L, Fang C. Dynamic Raman Line Shapes on an Evolving Excited-State Landscape: Insights from Tunable Femtosecond Stimulated Raman Spectroscopy. J Phys Chem A 2017; 121:5428-5441. [DOI: 10.1021/acs.jpca.7b04404] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Breland G. Oscar
- Department
of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Cheng Chen
- Department
of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Weimin Liu
- Department
of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Liangdong Zhu
- Department
of Physics, Oregon State University, 301 Weniger Hall, Corvallis, Oregon 97331, United States
| | - Chong Fang
- Department
of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon 97331, United States
- Department
of Physics, Oregon State University, 301 Weniger Hall, Corvallis, Oregon 97331, United States
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34
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Liu W, Tang L, Oscar BG, Wang Y, Chen C, Fang C. Tracking Ultrafast Vibrational Cooling during Excited-State Proton Transfer Reaction with Anti-Stokes and Stokes Femtosecond Stimulated Raman Spectroscopy. J Phys Chem Lett 2017; 8:997-1003. [PMID: 28195486 DOI: 10.1021/acs.jpclett.7b00322] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Energy dissipation following photoexcitation is foundational to photophysics and chemistry. Consequently, understanding such processes on molecular time scales holds paramount importance. Femtosecond stimulated Raman spectroscopy (FSRS) has been used to study the molecular structure-function relationships but usually on the Stokes side. Here, we perform both Stokes and anti-Stokes FSRS to track energy dissipation and excited-state proton transfer (ESPT) for the photoacid pyranine in aqueous solution. We reveal biphasic vibrational cooling on fs-ps time scales during ESPT. Characteristic low-frequency motions (<800 cm-1) exhibit initial energy dissipation (∼2 ps) that correlates with functional events of forming contact ion pairs via H-bonds between photoacid and water, which lengthens to ∼9 ps in methanol where ESPT is inhibited. The interplay between photoinduced dissipative and reactive channels is implied. Thermal cooling to bulk solvent occurs on the ∼50 ps time scale. These results demonstrate the combined Stokes and anti-Stokes FSRS as a powerful toolset to elucidate structural dynamics.
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Affiliation(s)
- Weimin Liu
- School of Physical Science and Technology, ShanghaiTech University , Pudong, Shanghai 201210, People's Republic of China
| | - Longteng Tang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Breland G Oscar
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Yanli Wang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Cheng Chen
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Chong Fang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
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35
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Tachibana SR, Tang L, Wang Y, Zhu L, Liu W, Fang C. Tuning calcium biosensors with a single-site mutation: structural dynamics insights from femtosecond Raman spectroscopy. Phys Chem Chem Phys 2017; 19:7138-7146. [DOI: 10.1039/c6cp08821j] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Structural dynamics governing the emission properties of a single-site mutant of fluorescent-protein-based calcium biosensors are elucidated by femtosecond stimulated Raman spectroscopy.
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Affiliation(s)
- Sean R. Tachibana
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
| | - Longteng Tang
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
| | - Yanli Wang
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
| | - Liangdong Zhu
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
| | - Weimin Liu
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
| | - Chong Fang
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
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36
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Heo W, Uddin N, Park JW, Rhee YM, Choi CH, Joo T. Coherent intermolecular proton transfer in the acid–base reaction of excited state pyranine. Phys Chem Chem Phys 2017; 19:18243-18251. [DOI: 10.1039/c7cp01944k] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The acidic proton in pyranine is transferred coherently to acetate through the stretching motion of the whole molecule.
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Affiliation(s)
- Wooseok Heo
- Department of Chemistry
- Pohang University of Science and Technology (POSTECH)
- Pohang 37673
- South Korea
| | - Nizam Uddin
- Department of Chemistry
- Kyunpook National University
- Daegu 41566
- South Korea
| | - Jae Woo Park
- Department of Chemistry
- Pohang University of Science and Technology (POSTECH)
- Pohang 37673
- South Korea
| | - Young Min Rhee
- Department of Chemistry
- Pohang University of Science and Technology (POSTECH)
- Pohang 37673
- South Korea
| | - Cheol Ho Choi
- Department of Chemistry
- Kyunpook National University
- Daegu 41566
- South Korea
| | - Taiha Joo
- Department of Chemistry
- Pohang University of Science and Technology (POSTECH)
- Pohang 37673
- South Korea
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37
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Liu W, Wang Y, Tang L, Oscar BG, Zhu L, Fang C. Panoramic portrait of primary molecular events preceding excited state proton transfer in water. Chem Sci 2016; 7:5484-5494. [PMID: 30034688 PMCID: PMC6021748 DOI: 10.1039/c6sc00672h] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Accepted: 05/11/2016] [Indexed: 12/31/2022] Open
Abstract
Primary events that power ultrafast excited state proton transfer in water are revealed to involve coupled intermolecular and intramolecular motions.
Photochemistry powers numerous processes from luminescence and human vision, to light harvesting. However, the elucidation of multidimensional photochemical reaction coordinates on molecular timescales remains challenging. We developed wavelength-tunable femtosecond stimulated Raman spectroscopy to simultaneously achieve pre-resonance enhancement for transient reactant and product species of the widely used photoacid pyranine undergoing excited-state proton transfer (ESPT) reaction in solution. In the low-frequency region, the 280 cm–1 ring deformation mode following 400 nm photoexcitation exhibits pronounced intensity oscillations on the sub-picosecond timescale due to anharmonic vibrational coupling to the 180 cm–1 hydrogen-bond stretching mode only in ESPT-capable solvents, indicating a primary event of functional relevance. This leads to the contact ion pair formation on the 3 ps timescale before diffusion-controlled separation. The intermolecular 180 cm–1 mode also reveals vibrational cooling time constants, ∼500 fs and 45 ps in both H2O and D2O, which differ from ESPT time constants of ∼3/8 and 90/250 ps in H2O/D2O, respectively. Spectral results using H218O further substantiate the functional role of the intermolecular 180 cm–1 mode in modulating the distance between proton donor and acceptor and forming the transient ion pair. The direct observation of molecular structural evolution across a wide spectral region during photochemical reactions enriches our fundamental understanding of potential energy surface and holds the key to advancing energy and biological sciences with exceptional atomic and temporal precision.
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Affiliation(s)
- Weimin Liu
- Oregon State University , Department of Chemistry , 263 Linus Pauling Science Centre (lab) , 153 Gilbert Hall (office) , Corvallis , OR 97331 , USA . ; ; Tel: +1 541 737 6704
| | - Yanli Wang
- Oregon State University , Department of Chemistry , 263 Linus Pauling Science Centre (lab) , 153 Gilbert Hall (office) , Corvallis , OR 97331 , USA . ; ; Tel: +1 541 737 6704
| | - Longteng Tang
- Oregon State University , Department of Chemistry , 263 Linus Pauling Science Centre (lab) , 153 Gilbert Hall (office) , Corvallis , OR 97331 , USA . ; ; Tel: +1 541 737 6704
| | - Breland G Oscar
- Oregon State University , Department of Chemistry , 263 Linus Pauling Science Centre (lab) , 153 Gilbert Hall (office) , Corvallis , OR 97331 , USA . ; ; Tel: +1 541 737 6704
| | - Liangdong Zhu
- Oregon State University , Department of Chemistry , 263 Linus Pauling Science Centre (lab) , 153 Gilbert Hall (office) , Corvallis , OR 97331 , USA . ; ; Tel: +1 541 737 6704
| | - Chong Fang
- Oregon State University , Department of Chemistry , 263 Linus Pauling Science Centre (lab) , 153 Gilbert Hall (office) , Corvallis , OR 97331 , USA . ; ; Tel: +1 541 737 6704
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38
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39
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Tang L, Liu W, Wang Y, Zhu L, Han F, Fang C. Ultrafast Structural Evolution and Chromophore Inhomogeneity inside a Green-Fluorescent-Protein-Based Ca(2+) Biosensor. J Phys Chem Lett 2016; 7:1225-30. [PMID: 26982256 DOI: 10.1021/acs.jpclett.6b00236] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Understanding excited-state structural dynamics of fluorescent-protein-based biosensors for Ca(2+) imaging is crucial for developing new in vivo Ca(2+) indicators and advancing bioimaging. We implemented wavelength-tunable femtosecond stimulated Raman spectroscopy (FSRS) with a 530 nm Raman pump to uncover the working mechanism of an intensiometric fluorescent-protein biosensor, G-GECO1.1, highlighting the deprotonation process of its embedded chromophore. Besides confirming the dynamic difference of excited-state proton transfer (ESPT) in the Ca(2+)-free/bound protein, we revealed a chromophore two-ring twisting process with time constants of 36/60 ps that competes with ESPT. In contrast with FSRS data collected using the 800 nm Raman pump, the bluer Raman pump enables us to access a subset of reactant population with partially deprotonated character that exhibits an additional ESPT component on the ∼5 ps time scale. These findings provide deep mechanistic insights into the inhomogeneity and subpopulation-specific conformational dynamics of biosensor chromophores, which will guide the rational design of improved biosensors for metal ion imaging.
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Affiliation(s)
- Longteng Tang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Weimin Liu
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Yanli Wang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Liangdong Zhu
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Fangyuan Han
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Chong Fang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
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40
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Dietze DR, Mathies RA. Femtosecond Stimulated Raman Spectroscopy. Chemphyschem 2016; 17:1224-51. [DOI: 10.1002/cphc.201600104] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Indexed: 11/10/2022]
Affiliation(s)
- Daniel R. Dietze
- Department of Chemistry; University of California in Berkeley; CA Berkeley 94720 USA
| | - Richard A. Mathies
- Department of Chemistry; University of California in Berkeley; CA Berkeley 94720 USA
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41
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Oscar BG, Liu W, Rozanov ND, Fang C. Ultrafast intermolecular proton transfer to a proton scavenger in an organic solvent. Phys Chem Chem Phys 2016; 18:26151-26160. [DOI: 10.1039/c6cp05692j] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The structural dynamics basis of intermolecular proton transfer from photoacid to acetate in methanol is revealed using femtosecond stimulated Raman spectroscopy.
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Affiliation(s)
- Breland G. Oscar
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
| | - Weimin Liu
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
| | - Nikita D. Rozanov
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
| | - Chong Fang
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Centre (lab)
- Corvallis
- USA
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42
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Ramegowda M, Ranjitha KN, Deepika TN. Exploring excited state properties of 7-hydroxy and 7-methoxy 4-methycoumarin: a combined time-dependent density functional theory/effective fragment potential study. NEW J CHEM 2016. [DOI: 10.1039/c5nj02917a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrogen bond dynamics, C–OH bond contracting, O–H bond stretching and O–H⋯O HB strengthening reveal the ESHT in 4MU at the S1state.
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43
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Sum-Frequency-Generation-Based Laser Sidebands for Tunable Femtosecond Raman Spectroscopy in the Ultraviolet. APPLIED SCIENCES-BASEL 2015. [DOI: 10.3390/app5020048] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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44
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Kardaś TM, Ratajska-Gadomska B, Lapini A, Ragnoni E, Righini R, Di Donato M, Foggi P, Gadomski W. Dynamics of the time-resolved stimulated Raman scattering spectrum in presence of transient vibronic inversion of population on the example of optically excited trans-β-apo-8'-carotenal. J Chem Phys 2015; 140:204312. [PMID: 24880285 DOI: 10.1063/1.4879060] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have studied the effect of transient vibrational inversion of population in trans-β-apo-8(')-carotenal on the time-resolved femtosecond stimulated Raman scattering (TR-FSRS) signal. The experimental data are interpreted by applying a quantum mechanical approach, using the formalism of projection operators for constructing the theoretical model of TR-FSRS. Within this theoretical frame we explain the presence of transient Raman losses on the Stokes side of the TR-FSRS spectrum as the effect of vibrational inversion of population. In view of the obtained experimental and theoretical results, we conclude that the excited S2 electronic level of trans-β-apo-8(')-carotenal relaxes towards the S0 ground state through a set of four vibrational sublevels of S1 state.
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Affiliation(s)
- T M Kardaś
- Department of Chemistry, University of Warsaw, Zwirki Wigury 101, 02-089 Warsaw, Poland
| | - B Ratajska-Gadomska
- Department of Chemistry, University of Warsaw, Zwirki Wigury 101, 02-089 Warsaw, Poland
| | - A Lapini
- European Laboratory for Non-linear Spectroscopy (LENS), Universit`a di Firenze, Via Nello Carrara 1, I-50019 Sesto Fiorentino (FI), Italy
| | - E Ragnoni
- European Laboratory for Non-linear Spectroscopy (LENS), Universit`a di Firenze, Via Nello Carrara 1, I-50019 Sesto Fiorentino (FI), Italy
| | - R Righini
- European Laboratory for Non-linear Spectroscopy (LENS), Universit`a di Firenze, Via Nello Carrara 1, I-50019 Sesto Fiorentino (FI), Italy
| | - M Di Donato
- European Laboratory for Non-linear Spectroscopy (LENS), Universit`a di Firenze, Via Nello Carrara 1, I-50019 Sesto Fiorentino (FI), Italy
| | - P Foggi
- European Laboratory for Non-linear Spectroscopy (LENS), Universit`a di Firenze, Via Nello Carrara 1, I-50019 Sesto Fiorentino (FI), Italy
| | - W Gadomski
- Department of Chemistry, University of Warsaw, Zwirki Wigury 101, 02-089 Warsaw, Poland
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45
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Tang L, Liu W, Wang Y, Zhao Y, Oscar BG, Campbell RE, Fang C. Unraveling ultrafast photoinduced proton transfer dynamics in a fluorescent protein biosensor for Ca(2+) imaging. Chemistry 2015; 21:6481-90. [PMID: 25761197 DOI: 10.1002/chem.201500491] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Indexed: 11/08/2022]
Abstract
Imaging Ca(2+) dynamics in living systems holds great potential to advance neuroscience and cellular biology. G-GECO1.1 is an intensiometric fluorescent protein Ca(2+) biosensor with a Thr-Tyr-Gly chromophore. The protonated chromophore emits green upon photoexcitation via excited-state proton transfer (ESPT). Upon Ca(2+) binding, a significant population of the chromophores becomes deprotonated. It remains elusive how the chromophore structurally evolves prior to and during ESPT, and how it is affected by Ca(2+) . We use femtosecond stimulated Raman spectroscopy to dissect ESPT in both the Ca(2+) -free and bound states. The protein chromophores exhibit a sub-200 fs vibrational frequency shift due to coherent small-scale proton motions. After wavepackets move out of the Franck-Condon region, ESPT gets faster in the Ca(2+) -bound protein, indicative of the formation of a more hydrophilic environment. These results reveal the governing structure-function relationship of Ca(2+) -sensing protein biosensors.
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Affiliation(s)
- Longteng Tang
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003 (USA)
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46
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Wang L, Liu W, Fang C. Elucidating low-frequency vibrational dynamics in calcite and water with time-resolved third-harmonic generation spectroscopy. Phys Chem Chem Phys 2015; 17:17034-40. [DOI: 10.1039/c5cp01813g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Coherent low-frequency vibrational dynamics in condensed phase from crystal, water, to aqueous electrolyte are elucidated by time-resolved third-harmonic-generation (TRTHG) spectroscopy.
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Affiliation(s)
- Liang Wang
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Center (lab)
- Corvallis
- USA
| | - Weimin Liu
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Center (lab)
- Corvallis
- USA
| | - Chong Fang
- Oregon State University
- Department of Chemistry
- 263 Linus Pauling Science Center (lab)
- Corvallis
- USA
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47
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Wang Y, Tang L, Liu W, Zhao Y, Oscar BG, Campbell RE, Fang C. Excited state structural events of a dual-emission fluorescent protein biosensor for Ca²⁺ imaging studied by femtosecond stimulated Raman spectroscopy. J Phys Chem B 2014; 119:2204-18. [PMID: 25226022 DOI: 10.1021/jp505698z] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Fluorescent proteins (FPs) are luminescent biomolecules that emit characteristic hues upon irradiation. A group of calmodulin (CaM)-green FP (GFP) chimeras have been previously engineered to enable the optical detection of calcium ions (Ca(2+)). We investigate one of these genetically encoded Ca(2+) biosensors for optical imaging (GECOs), GEM-GECO1, which fluoresces green without Ca(2+) but blue with Ca(2+), using femtosecond stimulated Raman spectroscopy (FSRS). The time-resolved FSRS data (<800 cm(-1)) reveal that initial structural evolution following 400 nm photoexcitation involves small-scale coherent proton motions on both ends of the chromophore two-ring system with a <250 fs time constant. Upon Ca(2+) binding, the chromophore adopts a more twisted conformation in the protein pocket with increased hydrophobicity, which inhibits excited-state proton transfer (ESPT) by effectively trapping the protonated chromophore in S1. Both the chromophore photoacidity and local environment form the ultrafast structural dynamics basis for the dual-emission properties of GEM-GECO1. Its photochemical transformations along multidimensional reaction coordinates are evinced by distinct stages of FSRS spectral evolution, particularly related to the ∼460 and 504 cm(-1) modes. The direct observation of lower frequency modes provides crucial information about the nuclear motions preceding ESPT, which enriches our understanding of photochemistry and enables the rational design of new biosensors.
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Affiliation(s)
- Yanli Wang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331-4003, United States
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48
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Excited-state structural dynamics of a dual-emission calmodulin-green fluorescent protein sensor for calcium ion imaging. Proc Natl Acad Sci U S A 2014; 111:10191-6. [PMID: 24987121 DOI: 10.1073/pnas.1403712111] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Fluorescent proteins (FPs) have played a pivotal role in bioimaging and advancing biomedicine. The versatile fluorescence from engineered, genetically encodable FP variants greatly enhances cellular imaging capabilities, which are dictated by excited-state structural dynamics of the embedded chromophore inside the protein pocket. Visualization of the molecular choreography of the photoexcited chromophore requires a spectroscopic technique capable of resolving atomic motions on the intrinsic timescale of femtosecond to picosecond. We use femtosecond stimulated Raman spectroscopy to study the excited-state conformational dynamics of a recently developed FP-calmodulin biosensor, GEM-GECO1, for calcium ion (Ca(2+)) sensing. This study reveals that, in the absence of Ca(2+), the dominant skeletal motion is a ∼ 170 cm(-1) phenol-ring in-plane rocking that facilitates excited-state proton transfer (ESPT) with a time constant of ∼ 30 ps (6 times slower than wild-type GFP) to reach the green fluorescent state. The functional relevance of the motion is corroborated by molecular dynamics simulations. Upon Ca(2+) binding, this in-plane rocking motion diminishes, and blue emission from a trapped photoexcited neutral chromophore dominates because ESPT is inhibited. Fluorescence properties of site-specific protein mutants lend further support to functional roles of key residues including proline 377 in modulating the H-bonding network and fluorescence outcome. These crucial structural dynamics insights will aid rational design in bioengineering to generate versatile, robust, and more sensitive optical sensors to detect Ca(2+) in physiologically relevant environments.
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Simkovitch R, Akulov K, Shomer S, Roth ME, Shabat D, Schwartz T, Huppert D. Comprehensive Study of Ultrafast Excited-State Proton Transfer in Water and D2O Providing the Missing RO–···H+ Ion-Pair Fingerprint. J Phys Chem A 2014; 118:4425-43. [DOI: 10.1021/jp5002435] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ron Simkovitch
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Katherine Akulov
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Shay Shomer
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Michal E. Roth
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Doron Shabat
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Tal Schwartz
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Dan Huppert
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
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50
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Finkler B, Spies C, Vester M, Walte F, Omlor K, Riemann I, Zimmer M, Stracke F, Gerhards M, Jung G. Highly photostable "super"-photoacids for ultrasensitive fluorescence spectroscopy. Photochem Photobiol Sci 2014; 13:548-62. [PMID: 24469857 DOI: 10.1039/c3pp50404b] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The photoacid 8-hydroxypyren-1,3,6-trisulfonic acid (HPTS, pyranine) is a widely used model compound for the examination of excited state proton transfer (ESPT). We synthesized five "super"-photoacids with varying hydrophilicity and acidity on the basis of HPTS. By chemical modification of the three sulfonic acid substituents, the photoacidity is enhanced by up to more than five logarithmic units from pK*≈ 1.4 to ∼-3.9 for the most acidic compound. As a result, nearly quantitative ESPT in DMSO can be observed. The novel photoacids were characterized by steady-state and time-resolved fluorescence techniques showing distinctively red shifted spectra compared to HPTS while maintaining a high quantum yield near 90%. Photostability of the compounds was checked by fluorescence correlation spectroscopy (FCS) and was found to be adequately high for ultrasensitive fluorescence spectroscopy. The described photoacids present a valuable palette for a wide range of applications, especially when the properties of HPTS, i.e. highly charged, low photostability and only moderate excited state acidity, are limiting.
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Affiliation(s)
- Björn Finkler
- Biophysical Chemistry, Saarland University, Campus B2 2, 66123 Saarbrücken, Germany.
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