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Kondo T, Shibata Y. Recent advances in single-molecule spectroscopy studies on light-harvesting processes in oxygenic photosynthesis. Biophys Physicobiol 2022. [PMCID: PMC9173860 DOI: 10.2142/biophysico.bppb-v19.0013] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Photosynthetic light-harvesting complexes (LHCs) play a crucial role in concentrating the photon energy from the sun that otherwise excites a typical pigment molecule, such as chlorophyll-a, only several times a second. Densely packed pigments in the complexes ensure efficient energy transfer to the reaction center. At the same time, LHCs have the ability to switch to an energy-quenching state and thus play a photoprotective role under excessive light conditions. Photoprotection is especially important for oxygenic photosynthetic organisms because toxic reactive oxygen species can be generated through photochemistry under aerobic conditions. Because of the extreme complexity of the systems in which various types of pigment molecules strongly interact with each other and with the surrounding protein matrixes, there has been long-standing difficulty in understanding the molecular mechanisms underlying the flexible switching between the light-harvesting and quenching states. Single-molecule spectroscopy studies are suitable to reveal the conformational dynamics of LHCs reflected in the fluorescence properties that are obscured in ordinary ensemble measurements. Recent advanced single-molecule spectroscopy studies have revealed the dynamical fluctuations of LHCs in their fluorescence peak position, intensity, and lifetime. The observed dynamics seem relevant to the conformational plasticity required for the flexible activations of photoprotective energy quenching. In this review, we survey recent advances in the single-molecule spectroscopy study of the light-harvesting systems of oxygenic photosynthesis.
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Affiliation(s)
- Toru Kondo
- School of Life Science and Technology, Tokyo Institute of Technology
| | - Yutaka Shibata
- Department of Chemistry, Graduate School of Science, Tohoku University
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Le DV, de la Perrelle JM, Do TN, Leng X, Tapping PC, Scholes GD, Kee TW, Tan HS. Characterization of the ultrafast spectral diffusion and vibronic coherence of TIPS-pentacene using 2D electronic spectroscopy. J Chem Phys 2021; 155:014302. [PMID: 34241376 DOI: 10.1063/5.0055528] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
TIPS-pentacene is a small-molecule organic semiconductor that is widely used in optoelectronic devices. It has been studied intensely owing to its ability to undergo singlet fission. In this study, we aim to develop further understanding of the coupling between the electronic and nuclear degrees of freedom of TIPS-pentacene (TIPS-Pn). We measured and analyzed the 2D electronic spectra of TIPS-Pn in solutions. Using center line slope (CLS) analysis, we characterized the frequency-fluctuation correlation function of the 0-0 vibronic transition. Strong oscillations in the CLS values were observed for up to 5 ps with a frequency of 264 cm-1, which are attributable to a large vibronic coupling with the TIPS-Pn ring-breathing vibrational mode. In addition, detailed analysis of the CLS values allowed us to retrieve two spectral diffusion lifetimes, which are attributed to the inertial and diffusive dynamics of solvent molecules. Amplitude beating analysis also uncovered couplings with another vibrational mode at 1173 cm-1. The experimental results can be described using the displaced harmonic oscillator model. By comparing the CLS values of the simulated data with the experimental CLS values, we estimated a Huang-Rhys factor of 0.1 for the ring-breathing vibrational mode. The results demonstrated how CLS analysis can be a useful method for characterizing the strength of vibronic coupling.
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Affiliation(s)
- Duc Viet Le
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | | | - Thanh Nhut Do
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Xuan Leng
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Patrick C Tapping
- Department of Chemistry, University of Adelaide, Adelaide SA 5005, Australia
| | - Gregory D Scholes
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
| | - Tak W Kee
- Department of Chemistry, University of Adelaide, Adelaide SA 5005, Australia
| | - Howe-Siang Tan
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
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Sosa ML, Wong CY. Revealing the evolving mixture of molecular aggregates during organic film formation using simulations of in situ absorbance. J Chem Phys 2020; 153:214902. [PMID: 33291921 DOI: 10.1063/5.0020788] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In this work, we introduce a method for modeling the evolving absorbance spectrum of an organic molecule, pseudoisocyanine (PIC), measured during the process of molecular aggregation. Despite being historically considered a J-aggregate, we find that the absorbance spectrum of PIC cannot be adequately modeled using solely J-aggregates either during molecular aggregation or in the final dry film. The collection of absorbance spectra during solution-casting is particularly difficult since a distribution of aggregates with various sizes and structures can coexist. Here, spectra measured during film formation are fit to a weighted sum of simulated spectra of two aggregate species, revealing the combinations of Coulombic coupling values, Huang-Rhys parameters, and aggregate sizes that provide good fits to measured spectra. The peak intensity ratios and relative peak positions are highly sensitive to the aggregate structure, and fitting only these features enables the rapid comparison of aggregate combinations. We find that the spectra of PIC aggregates cannot be modeled using the Huang-Rhys factor of the PIC monomer, as is typically assumed, leading us to consider models that utilize independent Huang-Rhys factors for each aggregate species. This method of fitting only the key spectral features allows an experimental spectrum to be modeled within 1 h-2 h when using a single Huang-Rhys factor, making the simulation of a series of in situ measurements during aggregation computationally feasible.
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Affiliation(s)
- Morgan L Sosa
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, USA
| | - Cathy Y Wong
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, USA
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Müh F, Zouni A. Structural basis of light-harvesting in the photosystem II core complex. Protein Sci 2020; 29:1090-1119. [PMID: 32067287 PMCID: PMC7184784 DOI: 10.1002/pro.3841] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 02/06/2020] [Accepted: 02/06/2020] [Indexed: 12/20/2022]
Abstract
Photosystem II (PSII) is a membrane-spanning, multi-subunit pigment-protein complex responsible for the oxidation of water and the reduction of plastoquinone in oxygenic photosynthesis. In the present review, the recent explosive increase in available structural information about the PSII core complex based on X-ray crystallography and cryo-electron microscopy is described at a level of detail that is suitable for a future structure-based analysis of light-harvesting processes. This description includes a proposal for a consistent numbering scheme of protein-bound pigment cofactors across species. The structural survey is complemented by an overview of the state of affairs in structure-based modeling of excitation energy transfer in the PSII core complex with emphasis on electrostatic computations, optical properties of the reaction center, the assignment of long-wavelength chlorophylls, and energy trapping mechanisms.
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Affiliation(s)
- Frank Müh
- Department of Theoretical Biophysics, Institute for Theoretical Physics, Johannes Kepler University Linz, Linz, Austria
| | - Athina Zouni
- Humboldt-Universität zu Berlin, Institute for Biology, Biophysics of Photosynthesis, Berlin, Germany
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Adolphs J, Maier F, Renger T. Wavelength-Dependent Exciton-Vibrational Coupling in the Water-Soluble Chlorophyll Binding Protein Revealed by Multilevel Theory of Difference Fluorescence Line-Narrowing. J Phys Chem B 2018; 122:8891-8899. [PMID: 30183300 DOI: 10.1021/acs.jpcb.8b08410] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
One of the most powerful line-narrowing techniques used to unravel the homogeneous lineshapes of inhomogeneously broadened systems is difference fluorescence line-narrowing spectroscopy. When this spectroscopy was applied to multichromophoric systems so far, the spectra were analyzed by an effective two-level system approach, composed of the electronic ground state and the lowest exciton state. An effective Huang-Rhys factor was assigned for the coupling of this state to the vibrations. Here, we extend this approach by including a multilevel line shape theory, which takes into account the excitonic coupling between pigments and thereby the effect of the delocalization of the excited states explicitly. In this way, it becomes possible to extract the spectral density of the local exciton-vibrational coupling. The theory is applied to the recombinant water-soluble chlorophyll binding protein reconstituted with chlorophyll a or b and reveals a significant decrease of the Huang-Rhys factor of the local exciton-vibrational coupling with decreasing transition energy of the chlorophylls. This decrease could be due to the increase in steric interactions reducing the flexibility of the environment and red-shifting the site energy of the pigments.
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Affiliation(s)
- Julian Adolphs
- Institute for Theoretical Physics , Johannes Kepler University Linz , Altenberger Strasse 69 , 4040 Linz , Austria
| | - Franziska Maier
- Institute for Theoretical Physics , Johannes Kepler University Linz , Altenberger Strasse 69 , 4040 Linz , Austria
| | - Thomas Renger
- Institute for Theoretical Physics , Johannes Kepler University Linz , Altenberger Strasse 69 , 4040 Linz , Austria
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Pieper J, Artene P, Rätsep M, Pajusalu M, Freiberg A. Evaluation of Electron–Phonon Coupling and Spectral Densities of Pigment–Protein Complexes by Line-Narrowed Optical Spectroscopy. J Phys Chem B 2018; 122:9289-9301. [DOI: 10.1021/acs.jpcb.8b05220] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Skandary S, Müh F, Ashraf I, Ibrahim M, Metzger M, Zouni A, Meixner AJ, Brecht M. Role of missing carotenoid in reducing the fluorescence of single monomeric photosystem II core complexes. Phys Chem Chem Phys 2018; 19:13189-13194. [PMID: 28489091 DOI: 10.1039/c6cp07748j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The fluorescence of monomeric photosystem II core complexes (mPSIIcc) of the cyanobacterium Thermosynechococcus elongatus, originating from redissolved crystals, is investigated by using single-molecule spectroscopy (SMS) at 1.6 K. The emission spectra of individual mPSIIcc are dominated by sharp zero-phonon lines, showing the existence of different emitters compatible with the F685, F689, and F695 bands reported formerly. The intensity of F695 is reduced in single mPSIIcc as compared to single PSIIcc-dimers (dPSIIcc). Crystal structures show that one of the β-carotene (β-Car) cofactors located at the monomer-monomer interface in dPSIIcc is missing in mPSIIcc. This β-Car in dPSIIcc is in van der Waals distance to chlorophyll (Chl) 17 in the CP47 subunit. We suggest that this Chl contributes to the F695 emitter. A loss of β-Car cofactors in mPSIIcc preparations will lead to an increased lifetime of the triplet state of Chl 17, which can explain the reduced singlet emission of F695 as observed in SMS.
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Affiliation(s)
- Sepideh Skandary
- IPTC and LISA+ Center, University of Tübingen, Tübingen, Germany.
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Kondo T, Chen WJ, Schlau-Cohen GS. Single-Molecule Fluorescence Spectroscopy of Photosynthetic Systems. Chem Rev 2017; 117:860-898. [DOI: 10.1021/acs.chemrev.6b00195] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Toru Kondo
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge Massachusetts 02139, United States
| | - Wei Jia Chen
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge Massachusetts 02139, United States
| | - Gabriela S. Schlau-Cohen
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge Massachusetts 02139, United States
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The quest for energy traps in the CP43 antenna of photosystem II. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2015; 152:286-300. [DOI: 10.1016/j.jphotobiol.2015.05.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2015] [Revised: 05/13/2015] [Accepted: 05/28/2015] [Indexed: 01/08/2023]
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