1
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Thwaites O, Christianson BM, Cowan AJ, Jäckel F, Liu LN, Gardner AM. Unravelling the Roles of Integral Polypeptides in Excitation Energy Transfer of Photosynthetic RC-LH1 Supercomplexes. J Phys Chem B 2023; 127:7283-7290. [PMID: 37556839 PMCID: PMC10461223 DOI: 10.1021/acs.jpcb.3c04466] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 07/24/2023] [Indexed: 08/11/2023]
Abstract
Elucidating the photosynthetic processes that occur within the reaction center-light-harvesting 1 (RC-LH1) supercomplexes from purple bacteria is crucial for uncovering the assembly and functional mechanisms of natural photosynthetic systems and underpinning the development of artificial photosynthesis. Here, we examined excitation energy transfer of various RC-LH1 supercomplexes of Rhodobacter sphaeroides using transient absorption spectroscopy, coupled with lifetime density analysis, and studied the roles of the integral transmembrane polypeptides, PufX and PufY, in energy transfer within the RC-LH1 core complex. Our results show that the absence of PufX increases both the LH1 → RC excitation energy transfer lifetime and distribution due to the role of PufX in defining the interaction and orientation of the RC within the LH1 ring. While the absence of PufY leads to the conformational shift of several LH1 subunits toward the RC, it does not result in a marked change in the excitation energy transfer lifetime.
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Affiliation(s)
- Owen Thwaites
- Stephenson
Institute of Renewable Energy, University
of Liverpool, Liverpool L69 7ZF, U.K.
- Department
of Physics, University of Liverpool, Liverpool L69 7ZE, U.K.
| | - Bern M. Christianson
- Institute
of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, U.K.
| | - Alexander J. Cowan
- Stephenson
Institute of Renewable Energy, University
of Liverpool, Liverpool L69 7ZF, U.K.
- Department
of Chemistry, University of Liverpool, Liverpool L69 7ZD, U.K.
| | - Frank Jäckel
- Stephenson
Institute of Renewable Energy, University
of Liverpool, Liverpool L69 7ZF, U.K.
- Department
of Physics, University of Liverpool, Liverpool L69 7ZE, U.K.
| | - Lu-Ning Liu
- Institute
of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, U.K.
- College
of Marine Life Sciences, and Frontiers Science Center for Deep Ocean
Multispheres and Earth System, Ocean University
of China, Qingdao 266003, China
| | - Adrian M. Gardner
- Stephenson
Institute of Renewable Energy, University
of Liverpool, Liverpool L69 7ZF, U.K.
- Department
of Chemistry, University of Liverpool, Liverpool L69 7ZD, U.K.
- Early Career
Laser Laboratory, University of Liverpool, Liverpool L69 3BX, U.K.
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2
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Wang D, Fiebig OC, Harris D, Toporik H, Ji Y, Chuang C, Nairat M, Tong AL, Ogren JI, Hart SM, Cao J, Sturgis JN, Mazor Y, Schlau-Cohen GS. Elucidating interprotein energy transfer dynamics within the antenna network from purple bacteria. Proc Natl Acad Sci U S A 2023; 120:e2220477120. [PMID: 37399405 PMCID: PMC10334754 DOI: 10.1073/pnas.2220477120] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 04/21/2023] [Indexed: 07/05/2023] Open
Abstract
In photosynthesis, absorbed light energy transfers through a network of antenna proteins with near-unity quantum efficiency to reach the reaction center, which initiates the downstream biochemical reactions. While the energy transfer dynamics within individual antenna proteins have been extensively studied over the past decades, the dynamics between the proteins are poorly understood due to the heterogeneous organization of the network. Previously reported timescales averaged over such heterogeneity, obscuring individual interprotein energy transfer steps. Here, we isolated and interrogated interprotein energy transfer by embedding two variants of the primary antenna protein from purple bacteria, light-harvesting complex 2 (LH2), together into a near-native membrane disc, known as a nanodisc. We integrated ultrafast transient absorption spectroscopy, quantum dynamics simulations, and cryogenic electron microscopy to determine interprotein energy transfer timescales. By varying the diameter of the nanodiscs, we replicated a range of distances between the proteins. The closest distance possible between neighboring LH2, which is the most common in native membranes, is 25 Å and resulted in a timescale of 5.7 ps. Larger distances of 28 to 31 Å resulted in timescales of 10 to 14 ps. Corresponding simulations showed that the fast energy transfer steps between closely spaced LH2 increase transport distances by ∼15%. Overall, our results introduce a framework for well-controlled studies of interprotein energy transfer dynamics and suggest that protein pairs serve as the primary pathway for the efficient transport of solar energy.
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Affiliation(s)
- Dihao Wang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Olivia C. Fiebig
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Dvir Harris
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Hila Toporik
- School of Molecular Sciences, Arizona State University, Tempe, AZ85281
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ85281
| | - Yi Ji
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Chern Chuang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Muath Nairat
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Ashley L. Tong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA02139
| | - John I. Ogren
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Stephanie M. Hart
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Jianshu Cao
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA02139
| | - James N. Sturgis
- LISM UMR 7255, CNRS and Aix-Marseille University, Marseille Cedex 913402, France
| | - Yuval Mazor
- School of Molecular Sciences, Arizona State University, Tempe, AZ85281
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ85281
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3
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Tani K, Kanno R, Ji XC, Satoh I, Kobayashi Y, Hall M, Yu LJ, Kimura Y, Mizoguchi A, Humbel BM, Madigan MT, Wang-Otomo ZY. Rhodobacter capsulatus forms a compact crescent-shaped LH1-RC photocomplex. Nat Commun 2023; 14:846. [PMID: 36792596 PMCID: PMC9932092 DOI: 10.1038/s41467-023-36460-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Accepted: 02/01/2023] [Indexed: 02/17/2023] Open
Abstract
Rhodobacter (Rba.) capsulatus has been a favored model for studies of all aspects of bacterial photosynthesis. This purple phototroph contains PufX, a polypeptide crucial for dimerization of the light-harvesting 1-reaction center (LH1-RC) complex, but lacks protein-U, a U-shaped polypeptide in the LH1-RC of its close relative Rba. sphaeroides. Here we present a cryo-EM structure of the Rba. capsulatus LH1-RC purified by DEAE chromatography. The crescent-shaped LH1-RC exhibits a compact structure containing only 10 LH1 αβ-subunits. Four αβ-subunits corresponding to those adjacent to protein-U in Rba. sphaeroides were absent. PufX in Rba. capsulatus exhibits a unique conformation in its N-terminus that self-associates with amino acids in its own transmembrane domain and interacts with nearby polypeptides, preventing it from interacting with proteins in other complexes and forming dimeric structures. These features are discussed in relation to the minimal requirements for the formation of LH1-RC monomers and dimers, the spectroscopic behavior of both the LH1 and RC, and the bioenergetics of energy transfer from LH1 to the RC.
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Affiliation(s)
- Kazutoshi Tani
- Graduate School of Medicine, Mie University, Tsu, Japan.
| | - Ryo Kanno
- Scientific Imaging Section, Research Support Division, Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1, Tancha, Onna-Son, Kunigami-Gun, Okinawa, Japan.,Quantum wave microscopy unit, Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1, Tancha, Onna-Son, Kunigami-Gun, Okinawa, Japan
| | | | | | | | - Malgorzata Hall
- Scientific Imaging Section, Research Support Division, Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1, Tancha, Onna-Son, Kunigami-Gun, Okinawa, Japan
| | - Long-Jiang Yu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Yukihiro Kimura
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe, Japan
| | | | - Bruno M Humbel
- Scientific Imaging Section, Research Support Division, Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1, Tancha, Onna-Son, Kunigami-Gun, Okinawa, Japan.,Department of Cell Biology and Neuroscience, Juntendo University, Graduate School of Medicine, Tokyo, Japan
| | - Michael T Madigan
- School of Biological Sciences, Department of Microbiology, Southern Illinois University, Carbondale, IL, USA
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4
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Tani K, Kobayashi K, Hosogi N, Ji XC, Nagashima S, Nagashima KVP, Izumida A, Inoue K, Tsukatani Y, Kanno R, Hall M, Yu LJ, Ishikawa I, Okura Y, Madigan MT, Mizoguchi A, Humbel BM, Kimura Y, Wang-Otomo ZY. A Ca 2+-binding motif underlies the unusual properties of certain photosynthetic bacterial core light-harvesting complexes. J Biol Chem 2022; 298:101967. [PMID: 35460693 PMCID: PMC9133646 DOI: 10.1016/j.jbc.2022.101967] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 04/16/2022] [Accepted: 04/18/2022] [Indexed: 01/24/2023] Open
Abstract
The mildly thermophilic purple phototrophic bacterium Allochromatium tepidum provides a unique model for investigating various intermediate phenotypes observed between those of thermophilic and mesophilic counterparts. The core light-harvesting (LH1) complex from A. tepidum exhibits an absorption maximum at 890 nm and mildly enhanced thermostability, both of which are Ca2+-dependent. However, it is unknown what structural determinants might contribute to these properties. Here, we present a cryo-EM structure of the reaction center–associated LH1 complex at 2.81 Å resolution, in which we identify multiple pigment-binding α- and β-polypeptides within an LH1 ring. Of the 16 α-polypeptides, we show that six (α1) bind Ca2+ along with β1- or β3-polypeptides to form the Ca2+-binding sites. This structure differs from that of fully Ca2+-bound LH1 from Thermochromatium tepidum, enabling determination of the minimum structural requirements for Ca2+-binding. We also identified three amino acids (Trp44, Asp47, and Ile49) in the C-terminal region of the A. tepidum α1-polypeptide that ligate each Ca ion, forming a Ca2+-binding WxxDxI motif that is conserved in all Ca2+-bound LH1 α-polypeptides from other species with reported structures. The partial Ca2+-bound structure further explains the unusual phenotypic properties observed for this bacterium in terms of its Ca2+-requirements for thermostability, spectroscopy, and phototrophic growth, and supports the hypothesis that A. tepidum may represent a “transitional” species between mesophilic and thermophilic purple sulfur bacteria. The characteristic arrangement of multiple αβ-polypeptides also suggests a mechanism of molecular recognition in the expression and/or assembly of the LH1 complex that could be regulated through interactions with reaction center subunits.
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Affiliation(s)
- Kazutoshi Tani
- Graduate School of Medicine, Mie University, Tsu, Japan.
| | - Kazumi Kobayashi
- EM Business Unit, JEOL Ltd 3-1-2 Musashino, Akishima, Tokyo, Japan
| | - Naoki Hosogi
- EM Business Unit, JEOL Ltd 3-1-2 Musashino, Akishima, Tokyo, Japan
| | | | - Sakiko Nagashima
- Research Institute for Integrated Science, Kanagawa University, Hiratsuka, Kanagawa, Japan
| | - Kenji V P Nagashima
- Research Institute for Integrated Science, Kanagawa University, Hiratsuka, Kanagawa, Japan
| | - Airi Izumida
- Department of Biological Sciences, Faculty of Science, Kanagawa University, Hiratsuka, Kanagawa, Japan
| | - Kazuhito Inoue
- Research Institute for Integrated Science, Kanagawa University, Hiratsuka, Kanagawa, Japan; Department of Biological Sciences, Faculty of Science, Kanagawa University, Hiratsuka, Kanagawa, Japan
| | - Yusuke Tsukatani
- Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Kanagawa, Japan
| | - Ryo Kanno
- Imaging Section, Research Support Division, Okinawa Institute of Science and Technology Graduate University (OIST), Kunigami-gun, Okinawa, Japan
| | - Malgorzata Hall
- Imaging Section, Research Support Division, Okinawa Institute of Science and Technology Graduate University (OIST), Kunigami-gun, Okinawa, Japan
| | - Long-Jiang Yu
- Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Isamu Ishikawa
- EM Business Unit, JEOL Ltd 3-1-2 Musashino, Akishima, Tokyo, Japan
| | - Yoshihiro Okura
- EM Business Unit, JEOL Ltd 3-1-2 Musashino, Akishima, Tokyo, Japan
| | - Michael T Madigan
- School of Biological Sciences, Department of Microbiology, Southern Illinois University, Carbondale, Illinois, USA
| | | | - Bruno M Humbel
- Imaging Section, Research Support Division, Okinawa Institute of Science and Technology Graduate University (OIST), Kunigami-gun, Okinawa, Japan
| | - Yukihiro Kimura
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Nada, Kobe, Japan.
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5
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Sattley WM, Swingley WD, Burchell BM, Dewey ED, Hayward MK, Renbarger TL, Shaffer KN, Stokes LM, Gurbani SA, Kujawa CM, Nuccio DA, Schladweiler J, Touchman JW, Wang-Otomo ZY, Blankenship RE, Madigan MT. Complete genome of the thermophilic purple sulfur Bacterium Thermochromatium tepidum compared to Allochromatium vinosum and other Chromatiaceae. PHOTOSYNTHESIS RESEARCH 2022; 151:125-142. [PMID: 34669148 DOI: 10.1007/s11120-021-00870-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 08/07/2021] [Indexed: 06/13/2023]
Abstract
The complete genome sequence of the thermophilic purple sulfur bacterium Thermochromatium tepidum strain MCT (DSM 3771T) is described and contrasted with that of its mesophilic relative Allochromatium vinosum strain D (DSM 180T) and other Chromatiaceae. The Tch. tepidum genome is a single circular chromosome of 2,958,290 base pairs with no plasmids and is substantially smaller than the genome of Alc. vinosum. The Tch. tepidum genome encodes two forms of RuBisCO and contains nifHDK and several other genes encoding a molybdenum nitrogenase but lacks a gene encoding a protein that assembles the Fe-S cluster required to form a functional nitrogenase molybdenum-iron cofactor, leaving the phototroph phenotypically Nif-. Tch. tepidum contains genes necessary for oxidizing sulfide to sulfate as photosynthetic electron donor but is genetically unequipped to either oxidize thiosulfate as an electron donor or carry out assimilative sulfate reduction, both of which are physiological hallmarks of Alc. vinosum. Also unlike Alc. vinosum, Tch. tepidum is obligately phototrophic and unable to grow chemotrophically in darkness by respiration. Several genes present in the Alc. vinosum genome that are absent from the genome of Tch. tepidum likely contribute to the major physiological differences observed between these related purple sulfur bacteria that inhabit distinct ecological niches.
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Affiliation(s)
- W Matthew Sattley
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA.
| | - Wesley D Swingley
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - Brad M Burchell
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Emma D Dewey
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Mackenzie K Hayward
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Tara L Renbarger
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Kathryn N Shaffer
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Lynn M Stokes
- Division of Natural Sciences, Indiana Wesleyan University, Marion, IN, 46953, USA
| | - Sonja A Gurbani
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - Catrina M Kujawa
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - D Adam Nuccio
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - Jacob Schladweiler
- Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA
| | - Jeffrey W Touchman
- School of Life Sciences, Arizona State University, Tempe, AR, 85287, USA
| | | | - Robert E Blankenship
- Departments of Chemistry and Biology, Washington University, St. Louis, MO, 63130, USA
| | - Michael T Madigan
- Department of Microbiology, School of Biological Sciences, Southern Illinois University, Carbondale, IL, 62901, USA
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6
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Tamura H, Saito K, Ishikita H. The origin of unidirectional charge separation in photosynthetic reaction centers: nonadiabatic quantum dynamics of exciton and charge in pigment-protein complexes. Chem Sci 2021; 12:8131-8140. [PMID: 34194703 PMCID: PMC8208306 DOI: 10.1039/d1sc01497h] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 05/03/2021] [Indexed: 11/21/2022] Open
Abstract
Exciton charge separation in photosynthetic reaction centers from purple bacteria (PbRC) and photosystem II (PSII) occurs exclusively along one of the two pseudo-symmetric branches (active branch) of pigment-protein complexes. The microscopic origin of unidirectional charge separation in photosynthesis remains controversial. Here we elucidate the essential factors leading to unidirectional charge separation in PbRC and PSII, using nonadiabatic quantum dynamics calculations in conjunction with time-dependent density functional theory (TDDFT) with the quantum mechanics/molecular mechanics/polarizable continuum model (QM/MM/PCM) method. This approach accounts for energetics, electronic coupling, and vibronic coupling of the pigment excited states under electrostatic interactions and polarization of whole protein environments. The calculated time constants of charge separation along the active branches of PbRC and PSII are similar to those observed in time-resolved spectroscopic experiments. In PbRC, Tyr-M210 near the accessary bacteriochlorophyll reduces the energy of the intermediate state and drastically accelerates charge separation overcoming the electron-hole interaction. Remarkably, even though both the active and inactive branches in PSII can accept excitons from light-harvesting complexes, charge separation in the inactive branch is prevented by a weak electronic coupling due to symmetry-breaking of the chlorophyll configurations. The exciton in the inactive branch in PSII can be transferred to the active branch via direct and indirect pathways. Subsequently, the ultrafast electron transfer to pheophytin in the active branch prevents exciton back transfer to the inactive branch, thereby achieving unidirectional charge separation.
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Affiliation(s)
- Hiroyuki Tamura
- Department of Applied Chemistry, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-8654 Japan
- Research Center for Advanced Science and Technology, The University of Tokyo 4-6-1 Komaba, Meguro-ku Tokyo 153-8904 Japan
| | - Keisuke Saito
- Department of Applied Chemistry, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-8654 Japan
- Research Center for Advanced Science and Technology, The University of Tokyo 4-6-1 Komaba, Meguro-ku Tokyo 153-8904 Japan
| | - Hiroshi Ishikita
- Department of Applied Chemistry, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-8654 Japan
- Research Center for Advanced Science and Technology, The University of Tokyo 4-6-1 Komaba, Meguro-ku Tokyo 153-8904 Japan
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7
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Chuang C, Brumer P. LH1-RC light-harvesting photocycle under realistic light-matter conditions. J Chem Phys 2020; 152:154101. [PMID: 32321270 DOI: 10.1063/5.0004490] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Quantum master equations are used to simulate the photocycle of the light-harvesting complex 1 (LH1) and the associated reaction center (RC) in purple bacteria excited with natural incoherent light. The influence of the radiation and protein environments and the full photocycle of the complexes, including the charge separation and RC recovery processes, are taken into account. Particular emphasis is placed on the steady state excitation energy transfer rate between the LH1 and the RC and the steady state dependence on the light intensity. The transfer rate is shown to scale linearly with light intensity near the value in the natural habitat and at higher light intensities is found to be bounded by the rate-determining step of the photocycle, the RC recovery rate. Transient (e.g., pulsed laser induced) dynamics, however, shows rates higher than the steady state value and continues to scale linearly with the intensity. The results show a correlation between the transfer rate and the manner in which the donor state is prepared. In addition, the transition from the transient to the steady state results can be understood as a cascade of ever slower rate-determining steps and quasi-stationary states inherent in multi-scale sequential processes. This type of transition of rates is relevant in most light-induced biological machinery.
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Affiliation(s)
- Chern Chuang
- Chemical Physics Theory Group, Department of Chemistry, and Center for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Paul Brumer
- Chemical Physics Theory Group, Department of Chemistry, and Center for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario M5S 3H6, Canada
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8
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Imanishi M, Takenouchi M, Takaichi S, Nakagawa S, Saga Y, Takenaka S, Madigan MT, Overmann J, Wang-Otomo ZY, Kimura Y. A Dual Role for Ca 2+ in Expanding the Spectral Diversity and Stability of Light-Harvesting 1 Reaction Center Photocomplexes of Purple Phototrophic Bacteria. Biochemistry 2019; 58:2844-2852. [PMID: 31145583 DOI: 10.1021/acs.biochem.9b00351] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The light-harvesting 1 reaction center (LH1-RC) complex in the purple sulfur bacterium Thiorhodovibrio ( Trv.) strain 970 cells exhibits its LH1 Q y transition at 973 nm, the lowest-energy Q y absorption among purple bacteria containing bacteriochlorophyll a (BChl a). Here we characterize the origin of this extremely red-shifted Q y transition. Growth of Trv. strain 970 did not occur in cultures free of Ca2+, and elemental analysis of Ca2+-grown cells confirmed that purified Trv. strain 970 LH1-RC complexes contained Ca2+. The LH1 Q y band of Trv. strain 970 was blue-shifted from 959 to 875 nm upon Ca2+ depletion, but the original spectral properties were restored upon Ca2+ reconstitution, which also occurs with the thermophilic purple bacterium Thermochromatium ( Tch.) tepidum. The amino acid sequences of the LH1 α- and β-polypeptides from Trv. strain 970 closely resemble those of Tch. tepidum; however, Ca2+ binding in the Trv. strain 970 LH1-RC occurred more selectively than in Tch. tepidum LH1-RC and with a reduced affinity. Ultraviolet resonance Raman analysis indicated that the number of hydrogen-bonding interactions between BChl a and LH1 proteins of Trv. strain 970 was significantly greater than for Tch. tepidum and that Ca2+ was indispensable for maintaining these bonds. Furthermore, perfusion-induced Fourier transform infrared analyses detected Ca2+-induced conformational changes in the binding site closely related to the unique spectral properties of Trv. strain 970. Collectively, our results reveal an ecological strategy employed by Trv. strain 970 of integrating Ca2+ into its LH1-RC complex to extend its light-harvesting capacity to regions of the near-infrared spectrum unused by other purple bacteria.
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Affiliation(s)
- Michie Imanishi
- Graduate School of Agricultural Science , Kobe University , Nada, Kobe 657-8501 , Japan
| | - Mizuki Takenouchi
- Faculty of Science , Ibaraki University , Bunkyo, Mito 310-8512 , Japan
| | - Shinichi Takaichi
- Faculty of Life Sciences , Tokyo University of Agriculture , Setagaya, Tokyo 156-8502 , Japan
| | - Shiori Nakagawa
- Department of Chemistry , Kindai University , Higashi-Osaka, Osaka 577-8502 , Japan
| | - Yoshitaka Saga
- Department of Chemistry , Kindai University , Higashi-Osaka, Osaka 577-8502 , Japan
| | - Shinji Takenaka
- Graduate School of Agricultural Science , Kobe University , Nada, Kobe 657-8501 , Japan
| | - Michael T Madigan
- Department of Microbiology , Southern Illinois University , Carbondale , Illinois 62901 , United States
| | - Jörg Overmann
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures , 38124 Braunschweig , Germany.,Microbiology , Braunschweig University of Technology , 38106 Braunschweig , Germany
| | | | - Yukihiro Kimura
- Graduate School of Agricultural Science , Kobe University , Nada, Kobe 657-8501 , Japan
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9
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Yu LJ, Suga M, Wang-Otomo ZY, Shen JR. Novel features of LH1-RC from Thermochromatium tepidum revealed from its atomic resolution structure. FEBS J 2018; 285:4359-4366. [PMID: 30328658 DOI: 10.1111/febs.14679] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 10/09/2018] [Indexed: 11/28/2022]
Abstract
Light-harvesting-1 (LH1)-reaction center (RC) super-complex is a membrane protein-pigment complex existing in purple photosynthetic bacteria, where LH1 absorbs light energy and transfers them rapidly and efficiently to RC to initiate the charge separation and electron transfer reactions. The structure of LH1-RC has been reported at relatively low resolutions from several different species of bacteria previously, but was solved at an atomic resolution recently from a thermophilic photosynthetic bacterium Thermochromatium tepidum. This high-resolution structure revealed the detailed organization of the super-complex including a number of unique features that are important for its functioning, such as a more intact RC structure, transporting routes for quinones to replace the bound QB as well as for the in-and-out of the closed LH1 ring, detailed coordinating environment of the Ca2+ ions in LH1 important for the remarkable red shift of the absorption spectrum, as well as for the enhanced thermostability. These results thus greatly advance our understanding on the mechanisms of energy transfer, quinone exchange, the red shift in the LH1-Qy transition and the enhanced thermal stability, in this super-complex.
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Affiliation(s)
- Long-Jiang Yu
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Japan
| | - Michihiro Suga
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Japan
| | | | - Jian-Ren Shen
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Japan
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10
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Kimura Y, Hashimoto K, Akimoto S, Takenouchi M, Suzuki K, Kishi R, Imanishi M, Takenaka S, Madigan MT, Nagashima KVP, Wang-Otomo ZY. Biochemical and Spectroscopic Characterizations of a Hybrid Light-Harvesting Reaction Center Core Complex. Biochemistry 2018; 57:4496-4503. [PMID: 29965735 DOI: 10.1021/acs.biochem.8b00644] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The light-harvesting 1 reaction center (LH1-RC) complex from Thermochromatium tepidum exhibits a largely red-shifted LH1 Q y absorption at 915 nm due to binding of Ca2+, resulting in an "uphill" energy transfer from LH1 to the reaction center (RC). In a recent study, we developed a heterologous expression system (strain TS2) to construct a functional hybrid LH1-RC with LH1 from Tch. tepidum and the RC from Rhodobacter sphaeroides [Nagashima, K. V. P., et al. (2017) Proc. Natl. Acad. Sci. U. S. A. 114, 10906]. Here, we present detailed characterizations of the hybrid LH1-RC from strain TS2. Effects of metal cations on the phototrophic growth of strain TS2 revealed that Ca2+ is an indispensable element for its growth, which is also true for Tch. tepidum but not for Rba. sphaeroides. The thermal stability of the TS2 LH1-RC was strongly dependent on Ca2+ in a manner similar to that of the native Tch. tepidum, but interactions between the heterologous LH1 and RC became relatively weaker in strain TS2. A Fourier transform infrared analysis demonstrated that the Ca2+-binding site of TS2 LH1 was similar but not identical to that of Tch. tepidum. Steady-state and time-resolved fluorescence measurements revealed that the uphill energy transfer rate from LH1 to the RC was related to the energy gap in an order of Rba. sphaeroides, Tch. tepidum, and strain TS2; however, the quantum yields of LH1 fluorescence did not exhibit such a correlation. On the basis of these findings, we discuss the roles of Ca2+, interactions between LH1 and the RC from different species, and the uphill energy transfer mechanisms.
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Affiliation(s)
- Yukihiro Kimura
- Department of Agrobioscience, Graduate School of Agriculture , Kobe University , Nada, Kobe 657-8501 , Japan
| | - Kanako Hashimoto
- Department of Agrobioscience, Graduate School of Agriculture , Kobe University , Nada, Kobe 657-8501 , Japan
| | - Seiji Akimoto
- Department of Science, Graduate School of Science , Kobe University , Nada, Kobe 657-8501 , Japan
| | - Mizuki Takenouchi
- Faculty of Science , Ibaraki University , Bunkyo, Mito 310-8512 , Japan
| | - Kengo Suzuki
- Hamamatsu Photonics K. K. , Joko-cho, Hamamatsu 431-3196 , Japan
| | - Rikako Kishi
- Department of Agrobioscience, Graduate School of Agriculture , Kobe University , Nada, Kobe 657-8501 , Japan
| | - Michie Imanishi
- Department of Agrobioscience, Graduate School of Agriculture , Kobe University , Nada, Kobe 657-8501 , Japan
| | - Shinji Takenaka
- Department of Agrobioscience, Graduate School of Agriculture , Kobe University , Nada, Kobe 657-8501 , Japan
| | - Michael T Madigan
- Department of Microbiology , Southern Illinois University , Carbondale , Illinois 62901 , United States
| | - Kenji V P Nagashima
- Research Institute for Photobiological Hydrogen Production , Kanagawa University , Tsuchiya, Hiratsuka 259-1293 , Japan
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11
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Tan LM, Yu J, Kawakami T, Kobayashi M, Wang P, Wang-Otomo ZY, Zhang JP. New Insights into the Mechanism of Uphill Excitation Energy Transfer from Core Antenna to Reaction Center in Purple Photosynthetic Bacteria. J Phys Chem Lett 2018; 9:3278-3284. [PMID: 29863354 DOI: 10.1021/acs.jpclett.8b01197] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The uphill excitation energy transfer (EET) from the core antenna (LH1) to the reaction center (RC) of purple photosynthetic bacteria was investigated at room temperature by comparing the native LH1-RC from Thermochromatium ( Tch.) tepidum with the hybrid LH1-RC from a mutant strain of Rhodobacter ( Rba.) sphaeroides. The latter protein with chimeric Tch-LH1 and Rba-RC exhibits a substantially larger RC-to-LH1 energy difference (Δ E = 630 cm-1) of 3-fold thermal energy (3 kB T). The spectroscopic and kinetics results are discussed on the basis of the newly reported high-resolution structures of Tch. tepidum LH1-RC, which allow us to propose the existence of a passage formed by LH1 BChls that facilitates the LH1 → RC EET. The semilogarithmic plot of the EET rate against Δ E was found to be linear over a broad range of Δ E, which consolidates the mechanism of thermal activation as promoted by the spectral overlap between the LH1 fluorescence and the special pair absorption of RC.
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Affiliation(s)
- Li-Ming Tan
- Department of Chemistry , Renmin University of China , Beijing 1000872 , PR China
| | - Jie Yu
- Department of Chemistry , Renmin University of China , Beijing 1000872 , PR China
| | | | - Masayuki Kobayashi
- Institute of National Colleges of Technology , Ariake College , Omuta , Fukuoka 836-8585 , Japan
| | - Peng Wang
- Department of Chemistry , Renmin University of China , Beijing 1000872 , PR China
| | | | - Jian-Ping Zhang
- Department of Chemistry , Renmin University of China , Beijing 1000872 , PR China
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12
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Gao D, Aly SM, Karsenti PL, Harvey PD. What does it take to induce equilibrium in bidirectional energy transfers? Phys Chem Chem Phys 2018; 20:13682-13692. [PMID: 29745390 DOI: 10.1039/c7cp07879j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Two dyads built with a co-facial slipped bis(zinc(ii)porphyrin), a free base and a bridge, [Zn2]-bridge-[Fb] (bridge = C6H4C[triple bond, length as m-dash]C, 1 and C6H4C[triple bond, length as m-dash]CC6H4, 2), exhibit S1 energy equilibrium [Zn2]* ↔ [Fb]* at 298 K, an extremely rare situation, which depends on the degree of MO coupling between the units. At 77 K, 2 becomes bi-directional due to the two large C6H4-[Zn2] and C6H4-[Fb] dihedral angles.
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Affiliation(s)
- Di Gao
- Departement de chimie, Université de Sherbrooke, Sherbrooke, QC J1K 2R1, Canada.
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13
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Yu LJ, Suga M, Wang-Otomo ZY, Shen JR. Structure of photosynthetic LH1-RC supercomplex at 1.9 Å resolution. Nature 2018; 556:209-213. [PMID: 29618814 DOI: 10.1038/s41586-018-0002-9] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2017] [Accepted: 02/23/2018] [Indexed: 11/09/2022]
Abstract
Light-harvesting complex 1 (LH1) and the reaction centre (RC) form a membrane-protein supercomplex that performs the primary reactions of photosynthesis in purple photosynthetic bacteria. The structure of the LH1-RC complex can provide information on the arrangement of protein subunits and cofactors; however, so far it has been resolved only at a relatively low resolution. Here we report the crystal structure of the calcium-ion-bound LH1-RC supercomplex of Thermochromatium tepidum at a resolution of 1.9 Å. This atomic-resolution structure revealed several new features about the organization of protein subunits and cofactors. We describe the loop regions of RC in their intact states, the interaction of these loop regions with the LH1 subunits, the exchange route for the bound quinone QB with free quinone molecules, the transport of free quinones between the inside and outside of the LH1 ring structure, and the detailed calcium-ion-binding environment. This structure provides a solid basis for the detailed examination of the light reactions that occur during bacterial photosynthesis.
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Affiliation(s)
- Long-Jiang Yu
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Michihiro Suga
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | | | - Jian-Ren Shen
- Research Institute for Interdisciplinary Science, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan.
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14
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Rätsep M, Timpmann K, Kawakami T, Wang-Otomo ZY, Freiberg A. Spectrally Selective Spectroscopy of Native Ca-Containing and Ba-Substituted LH1-RC Core Complexes from Thermochromatium tepidum. J Phys Chem B 2017; 121:10318-10326. [PMID: 29058423 DOI: 10.1021/acs.jpcb.7b07841] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The LH1-RC core complex from the thermophilic photosynthetic purple sulfur bacterium Thermochromatium tepidum has recently attracted interest of many researchers because of its several unique properties, such as increased robustness against environmental hardships and the much red-shifted near-infrared absorption spectrum of the LH1 antenna exciton polarons. The known near-atomic-resolution crystal structure of the complex well supported this attention. Yet several mechanistic aspects of the complex prominence remained to be understood. In this work, samples of the native, Ca2+-containing core complexes were investigated along with those destabilized by Ba2+ substitution, using various spectrally selective steady-state and picosecond time-resolved spectroscopic techniques at physiological and cryogenic temperatures. As a result, the current interpretation of exciton spectra of the complex was significantly clarified. Specifically, by evaluating the homogeneous and inhomogeneous compositions of the spectra, we showed that there is little to no effect of cation substitution on the dynamic or kinetic properties of antenna excitons. Reasons of the extra red shift of absorption/fluorescence spectra observed in the Ca-LH1-RC and not in the Ba-LH1-RC complex should thus be searched in subtle structural differences following the inclusion of different cations into the core complex scaffold.
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Affiliation(s)
- Margus Rätsep
- Institute of Physics, University of Tartu , W. Ostwald Str. 1, 50411 Tartu, Estonia
| | - Kõu Timpmann
- Institute of Physics, University of Tartu , W. Ostwald Str. 1, 50411 Tartu, Estonia
| | | | | | - Arvi Freiberg
- Institute of Physics, University of Tartu , W. Ostwald Str. 1, 50411 Tartu, Estonia.,Institute of Molecular and Cell Biology, University of Tartu , Riia 23, 51010 Tartu, Estonia
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15
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Probing structure-function relationships in early events in photosynthesis using a chimeric photocomplex. Proc Natl Acad Sci U S A 2017; 114:10906-10911. [PMID: 28935692 DOI: 10.1073/pnas.1703584114] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The native core light-harvesting complex (LH1) from the thermophilic purple phototrophic bacterium Thermochromatium tepidum requires Ca2+ for its thermal stability and characteristic absorption maximum at 915 nm. To explore the role of specific amino acid residues of the LH1 polypeptides in Ca-binding behavior, we constructed a genetic system for heterologously expressing the Tch. tepidum LH1 complex in an engineered Rhodobacter sphaeroides mutant strain. This system contained a chimeric pufBALM gene cluster (pufBA from Tch. tepidum and pufLM from Rba. sphaeroides) and was subsequently deployed for introducing site-directed mutations on the LH1 polypeptides. All mutant strains were capable of phototrophic (anoxic/light) growth. The heterologously expressed Tch. tepidum wild-type LH1 complex was isolated in a reaction center (RC)-associated form and displayed the characteristic absorption properties of this thermophilic phototroph. Spheroidene (the major carotenoid in Rba. sphaeroides) was incorporated into the Tch. tepidum LH1 complex in place of its native spirilloxanthins with one carotenoid molecule present per αβ-subunit. The hybrid LH1-RC complexes expressed in Rba. sphaeroides were characterized using absorption, fluorescence excitation, and resonance Raman spectroscopy. Site-specific mutagenesis combined with spectroscopic measurements revealed that α-D49, β-L46, and a deletion at position 43 of the α-polypeptide play critical roles in Ca binding in the Tch. tepidum LH1 complex; in contrast, α-N50 does not participate in Ca2+ coordination. These findings build on recent structural data obtained from a high-resolution crystallographic structure of the membrane integrated Tch. tepidum LH1-RC complex and have unambiguously identified the location of Ca2+ within this key antenna complex.
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16
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Ma F, Yu LJ, Llansola-Portoles MJ, Robert B, Wang-Otomo ZY, van Grondelle R. Metal Cations Induced αβ-BChl a
Heterogeneity in LH1 as Revealed by Temperature-Dependent Fluorescence Splitting. Chemphyschem 2017; 18:2295-2301. [DOI: 10.1002/cphc.201700551] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 06/09/2017] [Indexed: 11/09/2022]
Affiliation(s)
- Fei Ma
- Department of Biophysics; Faculty of Sciences; VU University Amsterdam; De Boelelaan 1081 1081 HV Amsterdam The Netherlands
| | - Long-Jiang Yu
- Faculty of Science; Ibaraki University; Mito Ibaraki 310-8512 Japan
| | - Manuel J. Llansola-Portoles
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS; Univ Paris-Sud, Université Paris-Saclay; F-91198 Gif-sur-Yvette cedex France
| | - Bruno Robert
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS; Univ Paris-Sud, Université Paris-Saclay; F-91198 Gif-sur-Yvette cedex France
| | | | - Rienk van Grondelle
- Department of Biophysics; Faculty of Sciences; VU University Amsterdam; De Boelelaan 1081 1081 HV Amsterdam The Netherlands
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17
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Ma F, Yu LJ, Hendrikx R, Wang-Otomo ZY, van Grondelle R. Excitonic and Vibrational Coherence in the Excitation Relaxation Process of Two LH1 Complexes as Revealed by Two-Dimensional Electronic Spectroscopy. J Phys Chem Lett 2017; 8:2751-2756. [PMID: 28585830 DOI: 10.1021/acs.jpclett.7b00824] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Ultrafast excitation relaxation within a manifold exciton state and long-lived vibrational coherence are two universal characteristics of photosynthetic antenna complexes. In this work, we studied the two-dimensional electronic spectra of two core light-harvesting (LH1) complexes of Thermochromatium (Tch.) tepidum, native Ca2+-LH1 and modified Ba2+-LH1. The role of the vibrational coherence in the exciton relaxation was revealed by comparing the two LH1 with similar structures but different electronic properties and by the evolution of the exciton and vibrational coherence as a function of temperature.
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Affiliation(s)
- Fei Ma
- Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam , De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Long-Jiang Yu
- Faculty of Science, Ibaraki University , Mito, Ibaraki 310-8512, Japan
- Research Institute for Interdisciplinary Science, Okayama University , 3-1-1 Tsushima Naka, Okayama 700-8530, Japan
| | - Ruud Hendrikx
- Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam , De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | | | - Rienk van Grondelle
- Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam , De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
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18
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Ma F, Yu LJ, Hendrikx R, Wang-Otomo ZY, van Grondelle R. Direct Observation of Energy Detrapping in LH1-RC Complex by Two-Dimensional Electronic Spectroscopy. J Am Chem Soc 2017; 139:591-594. [DOI: 10.1021/jacs.6b11017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Fei Ma
- Department
of Biophysics, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Long-Jiang Yu
- Faculty
of Science, Ibaraki University, Mito, Ibaraki 310-8512, Japan
- Research
Institute for Interdisciplinary, Okayama University, Tsushima
Naka 3-1-1, Okayama 700-8530, Japan
| | - Ruud Hendrikx
- Department
of Biophysics, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | | | - Rienk van Grondelle
- Department
of Biophysics, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
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19
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Challenges facing an understanding of the nature of low-energy excited states in photosynthesis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1627-1640. [PMID: 27372198 DOI: 10.1016/j.bbabio.2016.06.010] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 06/27/2016] [Accepted: 06/28/2016] [Indexed: 01/09/2023]
Abstract
While the majority of the photochemical states and pathways related to the biological capture of solar energy are now well understood and provide paradigms for artificial device design, additional low-energy states have been discovered in many systems with obscure origins and significance. However, as low-energy states are naively expected to be critical to function, these observations pose important challenges. A review of known properties of low energy states covering eight photochemical systems, and options for their interpretation, are presented. A concerted experimental and theoretical research strategy is suggested and outlined, this being aimed at providing a fully comprehensive understanding.
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