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Lynch P, Das A, Alam S, Rich CC, Frontiera RR. Mastering Femtosecond Stimulated Raman Spectroscopy: A Practical Guide. ACS PHYSICAL CHEMISTRY AU 2024; 4:1-18. [PMID: 38283786 PMCID: PMC10811773 DOI: 10.1021/acsphyschemau.3c00031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 10/02/2023] [Accepted: 10/02/2023] [Indexed: 01/30/2024]
Abstract
Femtosecond stimulated Raman spectroscopy (FSRS) is a powerful nonlinear spectroscopic technique that probes changes in molecular and material structure with high temporal and spectral resolution. With proper spectral interpretation, this is equivalent to mapping out reactive pathways on highly anharmonic excited-state potential energy surfaces with femtosecond to picosecond time resolution. FSRS has been used to examine structural dynamics in a wide range of samples, including photoactive proteins, photovoltaic materials, plasmonic nanostructures, polymers, and a range of others, with experiments performed in multiple groups around the world. As the FSRS technique grows in popularity and is increasingly implemented in user facilities, there is a need for a widespread understanding of the methodology and best practices. In this review, we present a practical guide to FSRS, including discussions of instrumentation, as well as data acquisition and analysis. First, we describe common methods of generating the three pulses required for FSRS: the probe, Raman pump, and actinic pump, including a discussion of the parameters to consider when selecting a beam generation method. We then outline approaches for effective and efficient FSRS data acquisition. We discuss common data analysis techniques for FSRS, as well as more advanced analyses aimed at extracting small signals on a large background. We conclude with a discussion of some of the new directions for FSRS research, including spectromicroscopy. Overall, this review provides researchers with a practical handbook for FSRS as a technique with the aim of encouraging many scientists and engineers to use it in their research.
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Affiliation(s)
- Pauline
G. Lynch
- Department
of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Aritra Das
- Department
of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Shahzad Alam
- Department
of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Christopher C. Rich
- Department
of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Renee R. Frontiera
- Department
of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
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2
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Chen C, Henderson JN, Ruchkin DA, Kirsh JM, Baranov MS, Bogdanov AM, Mills JH, Boxer SG, Fang C. Structural Characterization of Fluorescent Proteins Using Tunable Femtosecond Stimulated Raman Spectroscopy. Int J Mol Sci 2023; 24:11991. [PMID: 37569365 PMCID: PMC10418586 DOI: 10.3390/ijms241511991] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 07/19/2023] [Accepted: 07/24/2023] [Indexed: 08/13/2023] Open
Abstract
The versatile functions of fluorescent proteins (FPs) as fluorescence biomarkers depend on their intrinsic chromophores interacting with the protein environment. Besides X-ray crystallography, vibrational spectroscopy represents a highly valuable tool for characterizing the chromophore structure and revealing the roles of chromophore-environment interactions. In this work, we aim to benchmark the ground-state vibrational signatures of a series of FPs with emission colors spanning from green, yellow, orange, to red, as well as the solvated model chromophores for some of these FPs, using wavelength-tunable femtosecond stimulated Raman spectroscopy (FSRS) in conjunction with quantum calculations. We systematically analyzed and discussed four factors underlying the vibrational properties of FP chromophores: sidechain structure, conjugation structure, chromophore conformation, and the protein environment. A prominent bond-stretching mode characteristic of the quinoidal resonance structure is found to be conserved in most FPs and model chromophores investigated, which can be used as a vibrational marker to interpret chromophore-environment interactions and structural effects on the electronic properties of the chromophore. The fundamental insights gained for these light-sensing units (e.g., protein active sites) substantiate the unique and powerful capability of wavelength-tunable FSRS in delineating FP chromophore properties with high sensitivity and resolution in solution and protein matrices. The comprehensive characterization for various FPs across a colorful palette could also serve as a solid foundation for future spectroscopic studies and the rational engineering of FPs with diverse and improved functions.
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Affiliation(s)
- Cheng Chen
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331, USA;
| | - J. Nathan Henderson
- Center for Molecular Design and Biomimetics, The Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA; (J.N.H.); (J.H.M.)
| | - Dmitry A. Ruchkin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Ulitsa Miklukho-Maklaya, 16/10, 117997 Moscow, Russia; (D.A.R.); (M.S.B.); (A.M.B.)
| | - Jacob M. Kirsh
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA; (J.M.K.); (S.G.B.)
| | - Mikhail S. Baranov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Ulitsa Miklukho-Maklaya, 16/10, 117997 Moscow, Russia; (D.A.R.); (M.S.B.); (A.M.B.)
- Laboratory of Medicinal Substances Chemistry, Institute of Translational Medicine, Pirogov Russian National Research Medical University, Ostrovitianov 1, 117997 Moscow, Russia
| | - Alexey M. Bogdanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Ulitsa Miklukho-Maklaya, 16/10, 117997 Moscow, Russia; (D.A.R.); (M.S.B.); (A.M.B.)
| | - Jeremy H. Mills
- Center for Molecular Design and Biomimetics, The Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA; (J.N.H.); (J.H.M.)
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA
| | - Steven G. Boxer
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA; (J.M.K.); (S.G.B.)
| | - Chong Fang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331, USA;
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3
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Solaris J, Krueger TD, Chen C, Fang C. Photogrammetry of Ultrafast Excited-State Intramolecular Proton Transfer Pathways in the Fungal Pigment Draconin Red. Molecules 2023; 28:molecules28083506. [PMID: 37110741 PMCID: PMC10144053 DOI: 10.3390/molecules28083506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 04/11/2023] [Accepted: 04/13/2023] [Indexed: 04/29/2023] Open
Abstract
Proton transfer processes of organic molecules are key to charge transport and photoprotection in biological systems. Among them, excited-state intramolecular proton transfer (ESIPT) reactions are characterized by quick and efficient charge transfer within a molecule, resulting in ultrafast proton motions. The ESIPT-facilitated interconversion between two tautomers (PS and PA) comprising the tree fungal pigment Draconin Red in solution was investigated using a combination of targeted femtosecond transient absorption (fs-TA) and excited-state femtosecond stimulated Raman spectroscopy (ES-FSRS) measurements. Transient intensity (population and polarizability) and frequency (structural and cooling) dynamics of -COH rocking and -C=C, -C=O stretching modes following directed stimulation of each tautomer elucidate the excitation-dependent relaxation pathways, particularly the bidirectional ESIPT progression out of the Franck-Condon region to the lower-lying excited state, of the intrinsically heterogeneous chromophore in dichloromethane solvent. A characteristic overall excited-state PS-to-PA transition on the picosecond timescale leads to a unique "W"-shaped excited-state Raman intensity pattern due to dynamic resonance enhancement with the Raman pump-probe pulse pair. The ability to utilize quantum mechanics calculations in conjunction with steady-state electronic absorption and emission spectra to induce disparate excited-state populations in an inhomogeneous mixture of similar tautomers has broad implications for the modeling of potential energy surfaces and delineation of reaction mechanisms in naturally occurring chromophores. Such fundamental insights afforded by in-depth analysis of ultrafast spectroscopic datasets are also beneficial for future development of sustainable materials and optoelectronics.
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Affiliation(s)
- Janak Solaris
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331, USA
| | - Taylor D Krueger
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331, USA
| | - Cheng Chen
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331, USA
| | - Chong Fang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331, USA
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Tang L, Fang C. Fluorescence Modulation by Ultrafast Chromophore Twisting Events: Developing a Powerful Toolset for Fluorescent-Protein-Based Imaging. J Phys Chem B 2021; 125:13610-13623. [PMID: 34883016 DOI: 10.1021/acs.jpcb.1c08570] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The advancement of modern life sciences has benefited tremendously from the discovery and development of fluorescent proteins (FPs), widely expressed in live cells to track a myriad of cellular events. The chromophores of various FPs can undergo many ultrafast photophysical and/or photochemical processes in the electronic excited state and emit fluorescence with different colors. However, the chromophore becomes essentially nonfluorescent in solution environment due to its intrinsic twisting capability upon photoexcitation. To study "microscopic" torsional events and their effects on "macroscopic" fluorescence, we have developed an integrated ultrafast characterization platform involving femtosecond transient absorption (fs-TA) and wavelength-tunable femtosecond stimulated Raman spectroscopy (FSRS). A wide range of naturally occurring, circularly permuted, non-canonical amino-acid-decorated FPs and FP-based optical highlighters with photochromicity, photoconversion, and/or photoswitching capabilities have been recently investigated in great detail. Twisting conformational motions were elucidated to exist in all of these systems but to various extents. The associated different ultrafast pathways can be monitored via frequency changes of characteristic Raman bands during primary events and functional processes. The mapped electronic and structural dynamics information is crucial and has shown great potential and initial success for the rational design of proteins and other photoreceptors with novel functions and fluorescence properties.
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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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5
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Abstract
Fluorescence microscopy is advantageous for investigating biological processes and mechanisms in living cells. One of the most important considerations when designing an experiment is the selection of an appropriate fluorescent probe. Equally important is deciding how the probe will be attached to the protein of interest. The advantages and disadvantages of different fluorescent probe types and their respective labeling methods are discussed to provide an overview on selecting appropriate fluorophores and labeling systems for fluorescence-based assays. Protocols are outlined when appropriate.
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6
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Liu Y, He Y, Yang Y, Liu Y. Theoretical study on the detailed excited state triple proton transfer mechanism of cyclic 6-Azaindole trimer. Chem Phys Lett 2021. [DOI: 10.1016/j.cplett.2020.138137] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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7
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Oscar BG, Zhu L, Wolfendeen H, Rozanov ND, Chang A, Stout KT, Sandwisch JW, Porter JJ, Mehl RA, Fang C. Dissecting Optical Response and Molecular Structure of Fluorescent Proteins With Non-canonical Chromophores. Front Mol Biosci 2020; 7:131. [PMID: 32733917 PMCID: PMC7358599 DOI: 10.3389/fmolb.2020.00131] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Accepted: 06/02/2020] [Indexed: 12/21/2022] Open
Abstract
Tracking the structural dynamics of fluorescent protein chromophores holds the key to unlocking the fluorescence mechanisms in real time and enabling rational design principles of these powerful and versatile bioimaging probes. By combining recent chemical biology and ultrafast spectroscopy advances, we prepared the superfolder green fluorescent protein (sfGFP) and its non-canonical amino acid (ncAA) derivatives with a single chlorine, bromine, and nitro substituent at the ortho site to the phenolate oxygen of the embedded chromophore, and characterized them using an integrated toolset of femtosecond transient absorption and tunable femtosecond stimulated Raman spectroscopy (FSRS), aided by quantum calculations of the vibrational normal modes. A dominant vibrational cooling time constant of ~4 and 11 ps is revealed in Cl-GFP and Br-GFP, respectively, facilitating a ~30 and 12% increase of the fluorescent quantum yield vs. the parent sfGFP. Similar time constants were also retrieved from the transient absorption spectra, substantiating the correlated electronic and vibrational motions on the intrinsic molecular timescales. Key carbon-halogen stretching motions coupled with phenolate ring motions of the deprotonated chromophores at ca. 908 and 890 cm-1 in Cl-GFP and Br-GFP exhibit enhanced activities in the electronic excited state and blue-shift during a distinct vibrational cooling process on the ps timescale. The retrieved structural dynamics change due to targeted site-specific halogenation of the chromophore thus provides an effective means to design new GFP derivatives and enrich the bioimaging probe toolset for life and medical sciences.
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Affiliation(s)
- Breland G. Oscar
- Department of Chemistry, Oregon State University, Corvallis, OR, United States
| | - Liangdong Zhu
- Department of Chemistry, Oregon State University, Corvallis, OR, United States
| | - Hayati Wolfendeen
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, United States
| | - Nikita D. Rozanov
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR, United States
| | - Alvin Chang
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR, United States
| | - Kenneth T. Stout
- Department of Chemistry, Oregon State University, Corvallis, OR, United States
- School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR, United States
| | - Jason W. Sandwisch
- Department of Chemistry, Oregon State University, Corvallis, OR, United States
| | - Joseph J. Porter
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, United States
| | - Ryan A. Mehl
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR, United States
| | - Chong Fang
- Department of Chemistry, Oregon State University, Corvallis, OR, United States
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8
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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: 33] [Impact Index Per Article: 8.3] [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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9
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Krueger TD, Tang L, Zhu L, Breen IL, Wachter RM, Fang C. Dual Illumination Enhances Transformation of an Engineered Green-to-Red Photoconvertible Fluorescent Protein. Angew Chem Int Ed Engl 2020; 59:1644-1652. [PMID: 31692171 DOI: 10.1002/anie.201911379] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Indexed: 01/13/2023]
Abstract
The molecular mechanisms for the photoconversion of fluorescent proteins remain elusive owing to the challenges of monitoring chromophore structural dynamics during the light-induced processes. We implemented time-resolved electronic and stimulated Raman spectroscopies to reveal two hidden species of an engineered ancestral GFP-like protein LEA, involving semi-trapped protonated and trapped deprotonated chromophores en route to photoconversion in pH 7.9 buffer. A new dual-illumination approach was examined, using 400 and 505 nm light simultaneously to achieve faster conversion and higher color contrast. Substitution of UV irradiation with visible light benefits bioimaging, while the spectral benchmark of a trapped chromophore with characteristic ring twisting and bridge-H bending motions enables rational design of functional proteins. With the improved H-bonding network and structural motions, the photoexcited chromophore could increase the photoswitching-aided photoconversion while reducing trapped species.
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Affiliation(s)
- Taylor D Krueger
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR, 97331, USA
| | - Longteng Tang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR, 97331, USA
| | - Liangdong Zhu
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR, 97331, USA
| | - Isabella L Breen
- School of Molecular Sciences, Center for Bioenergy and Photosynthesis, Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ, 85287, USA
| | - Rebekka M Wachter
- School of Molecular Sciences, Center for Bioenergy and Photosynthesis, Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ, 85287, USA
| | - Chong Fang
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR, 97331, USA
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10
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Krueger TD, Tang L, Zhu L, Breen IL, Wachter RM, Fang C. Dual Illumination Enhances Transformation of an Engineered Green‐to‐Red Photoconvertible Fluorescent Protein. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201911379] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Taylor D. Krueger
- Department of Chemistry Oregon State University 153 Gilbert Hall Corvallis OR 97331 USA
| | - Longteng Tang
- Department of Chemistry Oregon State University 153 Gilbert Hall Corvallis OR 97331 USA
| | - Liangdong Zhu
- Department of Chemistry Oregon State University 153 Gilbert Hall Corvallis OR 97331 USA
| | - Isabella L. Breen
- School of Molecular Sciences Center for Bioenergy and Photosynthesis Biodesign Center for Applied Structural Discovery Arizona State University Tempe AZ 85287 USA
| | - Rebekka M. Wachter
- School of Molecular Sciences Center for Bioenergy and Photosynthesis Biodesign Center for Applied Structural Discovery Arizona State University Tempe AZ 85287 USA
| | - Chong Fang
- Department of Chemistry Oregon State University 153 Gilbert Hall Corvallis OR 97331 USA
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11
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Buhrke D, Hildebrandt P. Probing Structure and Reaction Dynamics of Proteins Using Time-Resolved Resonance Raman Spectroscopy. Chem Rev 2019; 120:3577-3630. [PMID: 31814387 DOI: 10.1021/acs.chemrev.9b00429] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The mechanistic understanding of protein functions requires insight into the structural and reaction dynamics. To elucidate these processes, a variety of experimental approaches are employed. Among them, time-resolved (TR) resonance Raman (RR) is a particularly versatile tool to probe processes of proteins harboring cofactors with electronic transitions in the visible range, such as retinal or heme proteins. TR RR spectroscopy offers the advantage of simultaneously providing molecular structure and kinetic information. The various TR RR spectroscopic methods can cover a wide dynamic range down to the femtosecond time regime and have been employed in monitoring photoinduced reaction cascades, ligand binding and dissociation, electron transfer, enzymatic reactions, and protein un- and refolding. In this account, we review the achievements of TR RR spectroscopy of nearly 50 years of research in this field, which also illustrates how the role of TR RR spectroscopy in molecular life science has changed from the beginning until now. We outline the various methodological approaches and developments and point out current limitations and potential perspectives.
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Affiliation(s)
- David Buhrke
- Technische Universität Berlin, Institut für Chemie, Sekr. PC14, Straße des 17, Juni 135, D-10623 Berlin, Germany
| | - Peter Hildebrandt
- Technische Universität Berlin, Institut für Chemie, Sekr. PC14, Straße des 17, Juni 135, D-10623 Berlin, Germany
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12
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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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13
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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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14
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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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15
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Tachibana SR, Tang L, Zhu L, Liu W, Wang Y, Fang C. Watching an Engineered Calcium Biosensor Glow: Altered Reaction Pathways before Emission. J Phys Chem B 2018; 122:11986-11995. [PMID: 30449101 DOI: 10.1021/acs.jpcb.8b10587] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Biosensors have become an indispensable tool set in life sciences. Among them, fluorescent protein-based biosensors have great biocompatibility and tunable emission properties but their development is largely on trial and error. To facilitate a rational design, we implement tunable femtosecond stimulated Raman spectroscopy, aided by transient absorption and quantum calculations, to elucidate the working mechanisms of a single-site Pro377Arg mutant of an emission ratiometric Ca2+ biosensor based on a green fluorescent protein-calmodulin complex. Comparisons with the parent protein and the Ca2+-free/bound states unveil more structural inhomogeneity yet an overall faster excited-state proton-transfer (ESPT) reaction inside the Ca2+-bound biosensor. The correlated photoreactant and photoproduct vibrational modes in the excited state reveal more chromophore twisting and trapping in the Ca2+-bound state during ESPT and the largely conserved chromophore dynamics in the Ca2+-free state from parent protein. The uncovered structural dynamics insights throughout an ESPT reaction inside a calcium biosensor provide important design principles in maintaining a hydrophilic, less compact, and more homogeneous environment with directional H-bonding (from the chromophore to surrounding protein residues) via bioengineering methods to improve the ESPT efficiency and quantum yield while maintaining photostability.
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Affiliation(s)
- Sean R Tachibana
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
| | - 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
| | - 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
| | - Chong Fang
- Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States
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16
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Quincy TJ, Barclay MS, Caricato M, Elles CG. Probing Dynamics in Higher-Lying Electronic States with Resonance-Enhanced Femtosecond Stimulated Raman Spectroscopy. J Phys Chem A 2018; 122:8308-8319. [PMID: 30256101 DOI: 10.1021/acs.jpca.8b07855] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Femtosecond stimulated Raman scattering (FSRS) measurements typically probe the structural dynamics of a molecule in the first electronically excited state, S1. While these measurements often rely on an electronic resonance condition to increase signal strength or enhance species selectivity, the effects of the resonance condition are usually neglected. However, mode-specific enhancements of the vibrational transitions in an FSRS spectrum contain detailed information about the resonant (upper) electronic state. Analogous to ground-state resonance Raman spectroscopy, the relative intensities of the Raman bands reveal displacements of the upper potential energy surface due to changes in the bonding pattern upon S n ← S1 electronic excitation, and therefore provide a sensitive probe of the ultrafast dynamics in the higher-lying state, S n. Raman gain profiles from the wavelength-dependent FSRS spectrum of the model compound 2,5-diphenylthiophene (DPT) reveal several modes with large displacement in the upper potential energy surface, including strong enhancement of a delocalized C-S-C stretching and ring deformation mode. The experimental results provide a benchmark for comparison with calculated spectra using time-dependent density functional theory (TD-DFT) and equation-of-motion coupled-cluster theory with single and double excitations (EOM-CCSD), where the calculations are based on the time-dependent formalism for resonance Raman spectroscopy. The simulated spectra are obtained from S1-S n transition strengths and the energy gradients of the upper (S n) potential energy surfaces along the S1 normal mode coordinates. The experimental results provide a stringent test of the computational approach, and indicate important limitations based on the level of theory and basis set. This work provides a foundation for making more accurate assignments of resonance-enhanced excited-state Raman spectra, as well as extracting novel information about higher-lying excited states in the transient absorption spectrum of a molecule.
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Affiliation(s)
- Timothy J Quincy
- Department of Chemistry , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Matthew S Barclay
- Department of Chemistry , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Marco Caricato
- Department of Chemistry , University of Kansas , Lawrence , Kansas 66045 , United States
| | - Christopher G Elles
- Department of Chemistry , University of Kansas , Lawrence , Kansas 66045 , United States
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17
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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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18
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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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19
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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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20
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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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21
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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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22
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Chen C, Liu W, Baranov MS, Baleeva NS, Yampolsky IV, Zhu L, Wang Y, Shamir A, Solntsev KM, Fang C. Unveiling Structural Motions of a Highly Fluorescent Superphotoacid by Locking and Fluorinating the GFP Chromophore in Solution. J Phys Chem Lett 2017; 8:5921-5928. [PMID: 29148819 DOI: 10.1021/acs.jpclett.7b02661] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Superphotoacidity involves ultrafast proton motions implicated in numerous chemical and biological processes. We used conformational locking and strategic addition of electron-withdrawing substituents to synthesize a new GFP chromophore analogue: p-HO-3,5-diF-BDI:BF2 (diF). It is highly fluorescent and exhibits excited-state proton transfer (ESPT) in various solvents, placing it among the strongest photoacids. Tunable femtosecond stimulated Raman spectroscopy with unique resonance conditions and transient absorption are complementarily employed to elucidate the structural basis for superphotoacidity. We reveal a multistep ESPT reaction from diF to methanol with an initial proton dissociation on the ∼600 fs time scale that forms a charge-separated state, stabilized by solvation, and followed by a diffusion-controlled proton transfer on the ∼350 ps time scale. A ∼1580 cm-1 phenolic ring motion is uncovered to accompany ESPT before 1 ps. This study provides a vivid movie of the photoinduced proton dissociation of a superphotoacid with bright fluorescence, effectively bridging fundamental mechanistic insights to precise control of macroscopic functions.
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Affiliation(s)
- 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
| | - Mikhail S Baranov
- Institute of Bioorganic Chemistry, Russian Academy of Sciences , Miklukho-Maklaya 16/10, 117997 Moscow, Russia
| | - Nadezhda S Baleeva
- Institute of Bioorganic Chemistry, Russian Academy of Sciences , Miklukho-Maklaya 16/10, 117997 Moscow, Russia
| | - Ilia V Yampolsky
- Institute of Bioorganic Chemistry, Russian Academy of Sciences , Miklukho-Maklaya 16/10, 117997 Moscow, Russia
- Pirogov Russian National Research Medical University , Ostrovitianov 1, Moscow 117997, Russia
| | - Liangdong Zhu
- Department of Chemistry, Oregon State University , 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Yanli Wang
- Department of Chemistry, Oregon State University , 153 Gilbert Hall, Corvallis, Oregon 97331, United States
| | - Alexandra Shamir
- School of Chemistry and Biochemistry, Georgia Institute of Technology , 901 Atlantic Drive, Atlanta, Georgia 30332, United States
| | - Kyril M Solntsev
- School of Chemistry and Biochemistry, Georgia Institute of Technology , 901 Atlantic Drive, Atlanta, Georgia 30332, United States
| | - Chong Fang
- Department of Chemistry, Oregon State University , 153 Gilbert Hall, Corvallis, Oregon 97331, United States
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23
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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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24
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Tang L, Wang Y, Liu W, Zhao Y, Campbell RE, Fang C. Illuminating Photochemistry of an Excitation Ratiometric Fluorescent Protein Calcium Biosensor. J Phys Chem B 2017; 121:3016-3023. [PMID: 28326779 DOI: 10.1021/acs.jpcb.7b01269] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Fluorescent protein (FP)-based biosensors have become an important and promising tool to track metal ion movement inside living systems. Their working principles after light irradiation, however, remain elusive. To facilitate the rational design of biosensors, we dissect the fluorescence modulation mechanism of a newly developed excitation ratiometric green FP-based Ca2+ biosensor, GEX-GECO1, using femtosecond stimulated Raman spectroscopy (FSRS) in the electronic excited state. Upon 400 nm photoexcitation, characteristic vibrational marker bands at ∼1180 and 1300 cm-1 show concomitant decay and rise dynamics, probing the progression of an ultrafast excited state proton transfer (ESPT) reaction. The Ca2+-bound biosensor exhibits two distinct populations that undergo ESPT with ∼6 and 80 ps time constants, in contrast to one dominant population with a 25 ps time constant in the Ca2+-free biosensor. This result is supported by key structural constraints from molecular dynamics simulations with and without Ca2+. The blueshift of the ∼1265 cm-1 C-O stretch mode unravels the vibrational cooling dynamics of the protonated chromophore regardless of Ca2+ binding events. This unique line of inquiry reveals the essential structural dynamics basis of fluorescence modulation inside an excitation ratiometric protein biosensor, correlating the uncovered chromophore structural heterogeneity with different H-bonding configurations and intrinsic proton transfer rate in the photoexcited state.
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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
| | - Weimin Liu
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Yongxin Zhao
- Department of Chemistry, University of Alberta , Edmonton, Alberta T6G 2G2, Canada
| | - Robert E Campbell
- Department of Chemistry, University of Alberta , Edmonton, Alberta T6G 2G2, Canada
| | - Chong Fang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
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25
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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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26
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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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27
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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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28
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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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29
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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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30
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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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31
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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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