1
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Dsouza L, Li X, Erić V, Huijser A, Jansen TLC, Holzwarth AR, Buda F, Bryant DA, Bahri S, Gupta KBSS, Sevink GJA, de Groot HJM. An integrated approach towards extracting structural characteristics of chlorosomes from a bchQ mutant of Chlorobaculum tepidum. Phys Chem Chem Phys 2024; 26:15856-15867. [PMID: 38546236 DOI: 10.1039/d4cp00221k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2024]
Abstract
Chlorosomes, the photosynthetic antenna complexes of green sulfur bacteria, are paradigms for light-harvesting elements in artificial designs, owing to their efficient energy transfer without protein participation. We combined magic angle spinning (MAS) NMR, optical spectroscopy and cryogenic electron microscopy (cryo-EM) to characterize the structure of chlorosomes from a bchQ mutant of Chlorobaculum tepidum. The chlorosomes of this mutant have a more uniform composition of bacteriochlorophyll (BChl) with a predominant homolog, [8Ethyl, 12Ethyl] BChl c, compared to the wild type (WT). Nearly complete 13C chemical shift assignments were obtained from well-resolved homonuclear 13C-13C RFDR data. For proton assignments heteronuclear 13C-1H (hCH) data sets were collected at 1.2 GHz spinning at 60 kHz. The CHHC experiments revealed intermolecular correlations between 132/31, 132/32, and 121/31, with distance constraints of less than 5 Å. These constraints indicate the syn-anti parallel stacking motif for the aggregates. Fourier transform cryo-EM data reveal an axial repeat of 1.49 nm for the helical tubular aggregates, perpendicular to the inter-tube separation of 2.1 nm. This axial repeat is different from WT and is in line with BChl syn-anti stacks running essentially parallel to the tube axis. Such a packing mode is in agreement with the signature of the Qy band in circular dichroism (CD). Combining the experimental data with computational insight suggests that the packing for the light-harvesting function is similar between WT and bchQ, while the chirality within the chlorosomes is modestly but detectably affected by the reduced compositional heterogeneity in bchQ.
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Affiliation(s)
- Lolita Dsouza
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA, Leiden, The Netherlands.
| | - Xinmeng Li
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA, Leiden, The Netherlands.
- Department of Chemistry and Hylleraas Centre for Quantum Molecular Sciences, University of Oslo, 0315, Oslo, Norway
| | - Vesna Erić
- Zernike Institute of Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, The Netherlands
| | - Annemarie Huijser
- MESA+ Institute for Nanotechnology, University of Twente, 7500 AE, The Netherlands
| | - Thomas L C Jansen
- Zernike Institute of Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, The Netherlands
| | - Alfred R Holzwarth
- Max Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Francesco Buda
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA, Leiden, The Netherlands.
| | - Donald A Bryant
- Department for Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Salima Bahri
- NMR Spectroscopy, Bijvoet center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | | | - G J Agur Sevink
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA, Leiden, The Netherlands.
| | - Huub J M de Groot
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA, Leiden, The Netherlands.
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2
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Götze JP, Maity S, Kleinekathöfer U. Incoherent Energy Transfer between the Baseplate and FMO Protein Explored at Ideal Geometries. J Phys Chem B 2023; 127:7829-7838. [PMID: 37691433 DOI: 10.1021/acs.jpcb.3c02568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
The Förster resonance energy transfer (FRET) between the Fenna-Matthews-Olson (FMO) protein complex and the chlorosomal baseplate (CBP) is investigated by using an idealized model. This simplified model is based on crystal structure and molecular dynamics conformations. Some of the further input, such as the transition dipole moments, was extracted from earlier molecular-level simulations. The resulting model mimics the effects of the relative position between the CBP and the FMO complex on the corresponding FRET efficiency under ideal conditions, involving about 1.3 billion FRET calculations per investigated model. In this idealized model and employing some approximations, it is found that FRET efficiency is almost completely independent of the FMO trimer orientation (displacement, distance, and rotation), despite FMO and CBP being highly structured complexes. Even removing individual FMO BChl triples will only reduce the FRET efficiency by up to 8.6%. An FMO containing only the least efficient BChl triple will retain about 25% of the FRET efficiency of a full FMO complex. In addition to its proposed function as an energetic funnel, FMO is thus identified to act as a highly robust spatial funnel for CBP excitation harvesting, independent of the mutual CBP-FMO orientation.
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Affiliation(s)
- Jan P Götze
- Institut für Chemie und Biochemie, Physikalische und Theoretische Chemie, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany
| | - Sayan Maity
- School of Science, Constructor University, Campusring 1, 28759 Bremen, Germany
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3
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Frehan SK, Dsouza L, Li X, Eríc V, Jansen TLC, Mul G, Holzwarth AR, Buda F, Sevink GJA, de Groot HJM, Huijser A. Photon Energy-Dependent Ultrafast Exciton Transfer in Chlorosomes of Chlorobium tepidum and the Role of Supramolecular Dynamics. J Phys Chem B 2023; 127:7581-7589. [PMID: 37611240 PMCID: PMC10493955 DOI: 10.1021/acs.jpcb.3c05282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 08/09/2023] [Indexed: 08/25/2023]
Abstract
The antenna complex of green sulfur bacteria, the chlorosome, is one of the most efficient supramolecular systems for efficient long-range exciton transfer in nature. Femtosecond transient absorption experiments provide new insight into how vibrationally induced quantum overlap between exciton states supports highly efficient long-range exciton transfer in the chlorosome of Chlorobium tepidum. Our work shows that excitation energy is delocalized over the chlorosome in <1 ps at room temperature. The following exciton transfer to the baseplate occurs in ∼3 to 5 ps, in line with earlier work also performed at room temperature, but significantly faster than at the cryogenic temperatures used in previous studies. This difference can be attributed to the increased vibrational motion at room temperature. We observe a so far unknown impact of the excitation photon energy on the efficiency of this process. This dependency can be assigned to distinct optical domains due to structural disorder, combined with an exciton trapping channel competing with exciton transfer toward the baseplate. An oscillatory transient signal damped in <1 ps has the highest intensity in the case of the most efficient exciton transfer to the baseplate. These results agree well with an earlier computational finding of exciton transfer driven by low-frequency rotational motion of molecules in the chlorosome. Such an exciton transfer process belongs to the quantum coherent regime, for which the Förster theory for intermolecular exciton transfer does not apply. Our work hence strongly indicates that structural flexibility is important for efficient long-range exciton transfer in chlorosomes.
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Affiliation(s)
- Sean K. Frehan
- MESA+
Institute for Nanotechnology, University
of Twente, 7500 AE Enschede, The Netherlands
| | - Lolita Dsouza
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Xinmeng Li
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
- Department
of Chemistry and Hylleraas Centre for Quantum Molecular Sciences, University of Oslo, 0315 Oslo, Norway
| | - Vesna Eríc
- Zernike
Institute of Advanced Materials, University
of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Thomas L. C. Jansen
- Zernike
Institute of Advanced Materials, University
of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Guido Mul
- MESA+
Institute for Nanotechnology, University
of Twente, 7500 AE Enschede, The Netherlands
| | - Alfred R. Holzwarth
- Max
Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Francesco Buda
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - G. J. Agur Sevink
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Huub J. M. de Groot
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Annemarie Huijser
- MESA+
Institute for Nanotechnology, University
of Twente, 7500 AE Enschede, The Netherlands
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4
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Chen JH, Wang W, Wang C, Kuang T, Shen JR, Zhang X. Cryo-electron microscopy structure of the intact photosynthetic light-harvesting antenna-reaction center complex from a green sulfur bacterium. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2023; 65:223-234. [PMID: 36125941 DOI: 10.1111/jipb.13367] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Accepted: 09/19/2022] [Indexed: 06/15/2023]
Abstract
The photosynthetic reaction center complex (RCC) of green sulfur bacteria (GSB) consists of the membrane-imbedded RC core and the peripheric energy transmitting proteins called Fenna-Matthews-Olson (FMO). Functionally, FMO transfers the absorbed energy from a huge peripheral light-harvesting antenna named chlorosome to the RC core where charge separation occurs. In vivo, one RC was found to bind two FMOs, however, the intact structure of RCC as well as the energy transfer mechanism within RCC remain to be clarified. Here we report a structure of intact RCC which contains a RC core and two FMO trimers from a thermophilic green sulfur bacterium Chlorobaculum tepidum at 2.9 Å resolution by cryo-electron microscopy. The second FMO trimer is attached at the cytoplasmic side asymmetrically relative to the first FMO trimer reported previously. We also observed two new subunits (PscE and PscF) and the N-terminal transmembrane domain of a cytochrome-containing subunit (PscC) in the structure. These two novel subunits possibly function to facilitate the binding of FMOs to RC core and to stabilize the whole complex. A new bacteriochlorophyll (numbered as 816) was identified at the interspace between PscF and PscA-1, causing an asymmetrical energy transfer from the two FMO trimers to RC core. Based on the structure, we propose an energy transfer network within this photosynthetic apparatus.
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Affiliation(s)
- Jing-Hua Chen
- College of Life Science, Zhejiang University, Hangzhou, 310058, China
- Department of Pathology of Sir Run Run Shaw Hospital, and Department of Biophysics, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Weiwei Wang
- College of Life Science, Zhejiang University, Hangzhou, 310058, China
| | - Chen Wang
- Department of Pathology of Sir Run Run Shaw Hospital, and Department of Biophysics, Zhejiang University School of Medicine, Hangzhou, 310058, China
| | - Tingyun Kuang
- Key Laboratory of Photobiology, Institute of Botany, Photosynthesis Research Center, the Chinese Academy of Sciences, Beijing, 100093, China
| | - Jian-Ren Shen
- Key Laboratory of Photobiology, Institute of Botany, Photosynthesis Research Center, the Chinese Academy of Sciences, Beijing, 100093, China
- Research Institute for Interdisciplinary Science, and Graduate School of Natural Science and Technology, Okayama University, Okayama, 700-8530, Japan
| | - Xing Zhang
- Department of Pathology of Sir Run Run Shaw Hospital, and Department of Biophysics, Zhejiang University School of Medicine, Hangzhou, 310058, China
- Center of Cryo Electron Microscopy, Zhejiang University School of Medicine, Hangzhou, 310058, China
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5
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Puskar R, Du Truong C, Swain K, Chowdhury S, Chan KY, Li S, Cheng KW, Wang TY, Poh YP, Mazor Y, Liu H, Chou TF, Nannenga BL, Chiu PL. Molecular asymmetry of a photosynthetic supercomplex from green sulfur bacteria. Nat Commun 2022; 13:5824. [PMID: 36192412 PMCID: PMC9529944 DOI: 10.1038/s41467-022-33505-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 09/20/2022] [Indexed: 11/21/2022] Open
Abstract
The photochemical reaction center (RC) features a dimeric architecture for charge separation across the membrane. In green sulfur bacteria (GSB), the trimeric Fenna-Matthews-Olson (FMO) complex mediates the transfer of light energy from the chlorosome antenna complex to the RC. Here we determine the structure of the photosynthetic supercomplex from the GSB Chlorobaculum tepidum using single-particle cryogenic electron microscopy (cryo-EM) and identify the cytochrome c subunit (PscC), two accessory protein subunits (PscE and PscF), a second FMO trimeric complex, and a linker pigment between FMO and the RC core. The protein subunits that are assembled with the symmetric RC core generate an asymmetric photosynthetic supercomplex. One linker bacteriochlorophyll (BChl) is located in one of the two FMO-PscA interfaces, leading to differential efficiencies of the two energy transfer branches. The two FMO trimeric complexes establish two different binding interfaces with the RC cytoplasmic surface, driven by the associated accessory subunits. This structure of the GSB photosynthetic supercomplex provides mechanistic insight into the light excitation energy transfer routes and a possible evolutionary transition intermediate of the bacterial photosynthetic supercomplex from the primitive homodimeric RC.
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Affiliation(s)
- Ryan Puskar
- School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ, 85287, USA
| | - Chloe Du Truong
- School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ, 85287, USA
- Rampart Bioscience, Monrovia, CA, 91016, USA
| | - Kyle Swain
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ, 85287, USA
| | - Saborni Chowdhury
- School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ, 85287, USA
| | - Ka-Yi Chan
- School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ, 85287, USA
| | - Shan Li
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Kai-Wen Cheng
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Ting Yu Wang
- Proteome Exploration Laboratory, Beckman Institute, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Yu-Ping Poh
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ, 85287, USA
- Center for Mechanisms of Evolution, Biodesign Institute, Arizona State University, Tempe, AZ, 85287, USA
| | - Yuval Mazor
- School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ, 85287, USA
| | - Haijun Liu
- Department of Biology, Washington University, St. Louis, MO, 63130, USA
| | - Tsui-Fen Chou
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125, USA
- Proteome Exploration Laboratory, Beckman Institute, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Brent L Nannenga
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ, 85287, USA
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ, 85287, USA
| | - Po-Lin Chiu
- School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA.
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ, 85287, USA.
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6
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Chen JH, Wu H, Xu C, Liu XC, Huang Z, Chang S, Wang W, Han G, Kuang T, Shen JR, Zhang X. Architecture of the photosynthetic complex from a green sulfur bacterium. Science 2021; 370:370/6519/eabb6350. [PMID: 33214250 DOI: 10.1126/science.abb6350] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 09/09/2020] [Indexed: 01/09/2023]
Abstract
The photosynthetic apparatus of green sulfur bacteria (GSB) contains a peripheral antenna chlorosome, light-harvesting Fenna-Matthews-Olson proteins (FMO), and a reaction center (GsbRC). We used cryo-electron microscopy to determine a 2.7-angstrom structure of the FMO-GsbRC supercomplex from Chlorobaculum tepidum The GsbRC binds considerably fewer (bacterio)chlorophylls [(B)Chls] than other known type I RCs do, and the organization of (B)Chls is similar to that in photosystem II. Two BChl layers in GsbRC are not connected by Chls, as seen in other RCs, but associate with two carotenoid derivatives. Relatively long distances of 22 to 33 angstroms were observed between BChls of FMO and GsbRC, consistent with the inefficient energy transfer between these entities. The structure contains common features of both type I and type II RCs and provides insight into the evolution of photosynthetic RCs.
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Affiliation(s)
- Jing-Hua Chen
- Department of Pathology of Sir Run Run Shaw Hospital and Department of Biophysics, Zhejiang University School of Medicine, Hangzhou, 310058 Zhejiang, China.,Center of Cryo-Electron Microscopy, Zhejiang University, Hangzhou, 310058 Zhejiang, China
| | - Hangjun Wu
- Department of Pathology of Sir Run Run Shaw Hospital and Department of Biophysics, Zhejiang University School of Medicine, Hangzhou, 310058 Zhejiang, China.,Center of Cryo-Electron Microscopy, Zhejiang University, Hangzhou, 310058 Zhejiang, China
| | - Caihuang Xu
- Department of Pathology of Sir Run Run Shaw Hospital and Department of Biophysics, Zhejiang University School of Medicine, Hangzhou, 310058 Zhejiang, China
| | - Xiao-Chi Liu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, 100093 Beijing, China
| | - Zihui Huang
- Department of Pathology of Sir Run Run Shaw Hospital and Department of Biophysics, Zhejiang University School of Medicine, Hangzhou, 310058 Zhejiang, China
| | - Shenghai Chang
- Department of Pathology of Sir Run Run Shaw Hospital and Department of Biophysics, Zhejiang University School of Medicine, Hangzhou, 310058 Zhejiang, China.,Center of Cryo-Electron Microscopy, Zhejiang University, Hangzhou, 310058 Zhejiang, China
| | - Wenda Wang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, 100093 Beijing, China
| | - Guangye Han
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, 100093 Beijing, China
| | - Tingyun Kuang
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, 100093 Beijing, China.
| | - Jian-Ren Shen
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, 100093 Beijing, China. .,Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, 700-8530 Okayama, Japan
| | - Xing Zhang
- Department of Pathology of Sir Run Run Shaw Hospital and Department of Biophysics, Zhejiang University School of Medicine, Hangzhou, 310058 Zhejiang, China. .,Center of Cryo-Electron Microscopy, Zhejiang University, Hangzhou, 310058 Zhejiang, China.,Zhejiang Laboratory for System and Precision Medicine, Zhejiang University Medical Center, 1369 West Wenyi Road, Hangzhou, 311121 Zhejiang, China
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7
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Irgen-Gioro S, Gururangan K, Spencer AP, Harel E. Non-Uniform Excited State Electronic-Vibrational Coupling of Pigment-Protein Complexes. J Phys Chem Lett 2020; 11:10388-10395. [PMID: 33238100 DOI: 10.1021/acs.jpclett.0c02454] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Photosynthetic organisms exploit interacting quantum degrees of freedom, namely intrapigment electron-vibrational (vibronic) and interpigment dipolar couplings (J-coupling), to rapidly and efficiently convert light into chemical energy. These interactions result in wave function configurations that delocalize excitation between pigments and pigment vibrations. Our study uses multidimensional spectroscopy to compare two model photosynthetic proteins, the Fenna-Matthews Olson (FMO) complex and light harvesting 2 (LH2), and confirm that long-lived excited state coherences originate from the vibrational modes of the pigment. Within this framework, the J-coupling of vibronic pigments should have a cascading effect in modifying the structured spectral density of excitonic states. We show that FMO effectively couples all of its excitations to a uniform set of vibrations while in LH2, its two chromophore rings each couple to a unique vibrational environment. We simulate energy transfer in a simple model system with non-uniform vibrational coupling to demonstrate how modification of the vibronic coupling strength can modulate energy transfer. Because increasing vibronic coupling increases internal relaxation, strongly coupled vibronic states can act as an energy funnel, which can potentially benefit energy transport.
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Affiliation(s)
- Shawn Irgen-Gioro
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Karthik Gururangan
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Austin P Spencer
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Elad Harel
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
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8
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Sato Y, Navarro Hernández A, Gillespie LD, Valete D. Effects of intramolecular vibrations on excitation energy transfer dynamics of the Fenna-Matthews-Olson complex. Chem Phys 2020. [DOI: 10.1016/j.chemphys.2020.110940] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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9
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10
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Fujiwara Y, Tamiaki H. Stereoselective self-aggregation of synthetic zinc 3 1-epimeric bacteriochlorophyll-d analogs possessing a methylene group at the 13 2-position as models of green photosynthetic bacterial chlorosomes. Photochem Photobiol Sci 2019; 18:1218-1227. [PMID: 30839974 DOI: 10.1039/c8pp00535d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Zinc bacteriochlorophyll-d analogs possessing a methylene group at the 132-position were prepared by chemical modification of naturally occurring chlorophyll-a. The synthetic 31-epimers were successfully separated by reverse phase HPLC to give diastereomerically pure samples. The stereochemistry of the chiral C31-center in the separated bacteriochlorophyll-d analogs was determined by HPLC analysis of the authentic stereoisomers prepared stereospecifically. Both the epimers were monomeric in tetrahydrofuran to give sharp absorption bands, while they self-aggregated to form chlorosomal oligomers with red-shifted bands in an aqueous Triton X-100 micelle solution. The resulting large oligomers deaggregated by addition of Triton X-100 to give monomeric species. Their aggregation and deaggregation were dependent on the 31-stereochemistry, indicating that each epimer produced self-aggregates that were supramolecularly different. The substitution with the 132-methylene group enhanced their self-aggregation abilities and the stability of their resulting self-aggregates.
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Affiliation(s)
- Yoshiki Fujiwara
- Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
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11
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Ranjbar Choubeh R, Koehorst RBM, Bína D, Struik PC, Pšenčík J, van Amerongen H. Efficiency of excitation energy trapping in the green photosynthetic bacterium Chlorobaculum tepidum. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2019; 1860:147-154. [PMID: 30537470 DOI: 10.1016/j.bbabio.2018.12.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 12/07/2018] [Accepted: 12/08/2018] [Indexed: 01/05/2023]
Abstract
During the millions of years of evolution, photosynthetic organisms have adapted to almost all terrestrial and aquatic habitats, although some environments are obviously more suitable for photosynthesis than others. Photosynthetic organisms living in low-light conditions require on the one hand a large light-harvesting apparatus to absorb as many photons as possible. On the other hand, the excitation trapping time scales with the size of the light-harvesting system, and the longer the distance over which the formed excitations have to be transferred, the larger the probability to lose excitations. Therefore a compromise between photon capture efficiency and excitation trapping efficiency needs to be found. Here we report results on the whole cells of the green sulfur bacterium Chlorobaculum tepidum. Its efficiency of excitation energy transfer and charge separation enables the organism to live in environments with very low illumination. Using fluorescence measurements with picosecond resolution, we estimate that despite a rather large size and complex composition of its light-harvesting apparatus, the quantum efficiency of its photochemistry is around ~87% at 20 °C, ~83% at 45 °C, and about ~81% at 77 K when part of the excitation energy is trapped by low-energy bacteriochlorophyll a molecules. The data are evaluated using target analysis, which provides further insight into the functional organization of the low-light adapted photosynthetic apparatus.
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Affiliation(s)
| | - Rob B M Koehorst
- Laboratory of Biophysics, Wageningen University, Wageningen, the Netherlands; MicroSpectroscopy Research Facility, Wageningen University, Wageningen, the Netherlands
| | - David Bína
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Paul C Struik
- Centre for Crop Systems Analysis, Wageningen University, Wageningen, the Netherlands
| | - Jakub Pšenčík
- Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
| | - Herbert van Amerongen
- Laboratory of Biophysics, Wageningen University, Wageningen, the Netherlands; MicroSpectroscopy Research Facility, Wageningen University, Wageningen, the Netherlands.
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