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Sarngadharan P, Holtkamp Y, Kleinekathöfer U. Protein Effects on the Excitation Energies and Exciton Dynamics of the CP24 Antenna Complex. J Phys Chem B 2024; 128:5201-5217. [PMID: 38756003 PMCID: PMC11145653 DOI: 10.1021/acs.jpcb.4c01637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 04/29/2024] [Accepted: 05/06/2024] [Indexed: 05/18/2024]
Abstract
In this study, the site energy fluctuations, energy transfer dynamics, and some spectroscopic properties of the minor light-harvesting complex CP24 in a membrane environment were determined. For this purpose, a 3 μs-long classical molecular dynamics simulation was performed for the CP24 complex. Furthermore, using the density functional tight binding/molecular mechanics molecular dynamics (DFTB/MM MD) approach, we performed excited state calculations for the chlorophyll a and chlorophyll b molecules in the complex starting from five different positions of the MD trajectory. During the extended simulations, we observed variations in the site energies of the different sets as a result of the fluctuating protein environment. In particular, a water coordination to Chl-b 608 occurred only after about 1 μs in the simulations, demonstrating dynamic changes in the environment of this pigment. From the classical and the DFTB/MM MD simulations, spectral densities and the (time-dependent) Hamiltonian of the complex were determined. Based on these results, three independent strongly coupled chlorophyll clusters were revealed within the complex. In addition, absorption and fluorescence spectra were determined together with the exciton relaxation dynamics, which reasonably well agrees with experimental time scales.
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Affiliation(s)
- Pooja Sarngadharan
- School of Science, Constructor
University, Campus Ring
1, 28759 Bremen, Germany
| | - Yannick Holtkamp
- School of Science, Constructor
University, Campus Ring
1, 28759 Bremen, Germany
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2
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Bhattacharjee S, Arra S, Daidone I, Pantazis DA. Excitation landscape of the CP43 photosynthetic antenna complex from multiscale simulations. Chem Sci 2024; 15:7269-7284. [PMID: 38756808 PMCID: PMC11095388 DOI: 10.1039/d3sc06714a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 04/07/2024] [Indexed: 05/18/2024] Open
Abstract
Photosystem II (PSII), the principal enzyme of oxygenic photosynthesis, contains two integral light harvesting proteins (CP43 and CP47) that bind chlorophylls and carotenoids. The two intrinsic antennae play crucial roles in excitation energy transfer and photoprotection. CP43 interacts most closely with the reaction center of PSII, specifically with the branch of the reaction center (D1) that is responsible for primary charge separation and electron transfer. Deciphering the function of CP43 requires detailed atomic-level insights into the properties of the embedded pigments. To advance this goal, we employ a range of multiscale computational approaches to determine the site energies and excitonic profile of CP43 chlorophylls, using large all-atom models of a membrane-bound PSII monomer. In addition to time-dependent density functional theory (TD-DFT) used in the context of a quantum-mechanics/molecular-mechanics setup (QM/MM), we present a thorough analysis using the perturbed matrix method (PMM), which enables us to utilize information from long-timescale molecular dynamics simulations of native PSII-complexed CP43. The excited state energetics and excitonic couplings have both similarities and differences compared with previous experimental fits and theoretical calculations. Both static TD-DFT and dynamic PMM results indicate a layered distribution of site energies and reveal specific groups of chlorophylls that have shared contributions to low-energy excitations. Importantly, the contribution to the lowest energy exciton does not arise from the same chlorophylls at each system configuration, but rather changes as a function of conformational dynamics. An unexpected finding is the identification of a low-energy charge-transfer excited state within CP43 that involves a lumenal (C2) and the central (C10) chlorophyll of the complex. The results provide a refined basis for structure-based interpretation of spectroscopic observations and for further deciphering excitation energy transfer in oxygenic photosynthesis.
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Affiliation(s)
- Sinjini Bhattacharjee
- Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1 45470 Mülheim an der Ruhr Germany
| | - Srilatha Arra
- Department of Physical and Chemical Sciences, University of L'Aquila Via Vetoio (Coppito 1) 67010 L'Aquila Italy
| | - Isabella Daidone
- Department of Physical and Chemical Sciences, University of L'Aquila Via Vetoio (Coppito 1) 67010 L'Aquila Italy
| | - Dimitrios A Pantazis
- Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1 45470 Mülheim an der Ruhr Germany
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3
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Biswas S, Niedzwiedzki DM, Pakrasi HB. Energy dissipation efficiency in the CP43 assembly intermediate complex of photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148982. [PMID: 37146928 DOI: 10.1016/j.bbabio.2023.148982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 04/10/2023] [Accepted: 04/20/2023] [Indexed: 05/07/2023]
Abstract
Photosystem II in oxygenic organisms is a large membrane bound rapidly turning over pigment protein complex. During its biogenesis, multiple assembly intermediates are formed, including the CP43-preassembly complex (pCP43). To understand the energy transfer dynamics in pCP43, we first engineered a His-tagged version of the CP43 in a CP47-less strain of the cyanobacterium Synechocystis 6803. Isolated pCP43 from this engineered strain was subjected to advanced spectroscopic analysis to evaluate its excitation energy dissipation characteristics. These included measurements of steady-state absorption and fluorescence emission spectra for which correlation was tested with Stepanov relation. Comparison of fluorescence excitation and absorptance spectra determined that efficiency of energy transfer from β-carotene to chlorophyll a is 39 %. Time-resolved fluorescence images of pCP43-bound Chl a were recorded on streak camera, and fluorescence decay dynamics were evaluated with global fitting. These demonstrated that the decay kinetics strongly depends on temperature and buffer used to disperse the protein sample and fluorescence decay lifetime was estimated in 3.2-5.7 ns time range, depending on conditions. The pCP43 complex was also investigated with femtosecond and nanosecond time-resolved absorption spectroscopy upon excitation of Chl a and β-carotene to reveal pathways of singlet excitation relaxation/decay, Chl a triplet dynamics and Chl a → β-carotene triplet state sensitization process. The latter demonstrated that Chl a triplet in the pCP43 complex is not efficiently quenched by carotenoids. Finally, detailed kinetic analysis of the rise of the population of β-carotene triplets determined that the time constant of the carotenoid triplet sensitization is 40 ns.
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Affiliation(s)
- Sandeep Biswas
- Department of Biology, Washington University, St. Louis, MO 63130, USA.
| | - Dariusz M Niedzwiedzki
- Center for Solar Energy and Energy Storage, Washington University, St. Louis, MO 63130, USA; Department of Energy, Environmental & Chemical Engineering, Washington University, St. Louis, MO 63130, USA.
| | - Himadri B Pakrasi
- Department of Biology, Washington University, St. Louis, MO 63130, USA.
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4
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Saito K, Mitsuhashi K, Tamura H, Ishikita H. Quantum mechanical analysis of excitation energy transfer couplings in photosystem II. Biophys J 2023; 122:470-483. [PMID: 36609140 PMCID: PMC9941724 DOI: 10.1016/j.bpj.2023.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 11/21/2022] [Accepted: 01/04/2023] [Indexed: 01/07/2023] Open
Abstract
We evaluated excitation energy transfer (EET) coupling (J) between all pairs of chlorophylls (Chls) and pheophytins (Pheos) in the protein environment of photosystem II based on the time-dependent density functional theory with a quantum mechanical/molecular mechanics approach. In the reaction center, the EET coupling between Chls PD1 and PD2 is weaker (|J(PD1/PD2)| = 79 cm-1), irrespective of a short edge-to-edge distance of 3.6 Å (Mg-to-Mg distance of 8.1 Å), than the couplings between PD1 and the accessory ChlD1 (|J(PD1/ChlD2)| = 104 cm-1) and between PD2 and ChlD2 (|J(PD2/ChlD1)| = 101 cm-1), suggesting that PD1 and PD2 are two monomeric Chls rather than a "special pair". There exist strongly coupled Chl pairs (|J| > ∼100 cm-1) in the CP47 and CP43 core antennas, which may be candidates for the red-shifted Chls observed in spectroscopic studies. In CP47 and CP43, Chls ligated to CP47-His26 and CP43-His56, which are located in the middle layer of the thylakoid membrane, play a role in the "hub" that mediates the EET from the lumenal to stromal layers. In the stromal layer, Chls ligated to CP47-His466, CP43-His441, and CP43-His444 mediate the EET from CP47 to ChlD2/PheoD2 and from CP43 to ChlD1/PheoD1 in the reaction center. Thus, the excitation energy from both CP47 and CP43 can always be utilized for the charge-separation reaction in the reaction center.
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Affiliation(s)
- Keisuke Saito
- Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Research Center for Advanced Science and Technology, The University of Tokyo, Meguro-ku, Tokyo, Japan.
| | - Koji Mitsuhashi
- Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Hiroyuki Tamura
- Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Research Center for Advanced Science and Technology, The University of Tokyo, Meguro-ku, Tokyo, Japan.
| | - Hiroshi Ishikita
- Department of Applied Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Research Center for Advanced Science and Technology, The University of Tokyo, Meguro-ku, Tokyo, Japan.
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5
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Sarngadharan P, Maity S, Kleinekathöfer U. Spectral densities and absorption spectra of the core antenna complex CP43 from photosystem II. J Chem Phys 2022; 156:215101. [DOI: 10.1063/5.0091005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Besides absorbing light, the core antenna complex CP43 of photosystem II is of great importance in transferring excitation energy from the antenna complexes to the reaction center. Excitation energies, spectral densities, and linear absorption spectra of the complex have been evaluated by a multiscale approach. In this scheme, quantum mechanics/molecular mechanics molecular dynamics simulations are performed employing the parameterized density functional tight binding (DFTB) while the time-dependent long-range-corrected DFTB scheme is applied for the excited state calculations. The obtained average spectral density of the CP43 complex shows a very good agreement with experimental results. Moreover, the excitonic Hamiltonian of the system along with the computed site-dependent spectral densities was used to determine the linear absorption. While a Redfield-like approximation has severe shortcomings in dealing with the CP43 complex due to quasi-degenerate states, the non-Markovian full second-order cumulant expansion formalism is able to overcome the drawbacks. Linear absorption spectra were obtained, which show a good agreement with the experimental counterparts at different temperatures. This study once more emphasizes that by combining diverse techniques from the areas of molecular dynamics simulations, quantum chemistry, and open quantum systems, it is possible to obtain first-principle results for photosynthetic complexes, which are in accord with experimental findings.
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Affiliation(s)
- Pooja Sarngadharan
- Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Sayan Maity
- Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Ulrich Kleinekathöfer
- Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
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6
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Friedl C, Fedorov DG, Renger T. Towards a quantitative description of excitonic couplings in photosynthetic pigment-protein complexes: quantum chemistry driven multiscale approaches. Phys Chem Chem Phys 2022; 24:5014-5038. [PMID: 35142765 PMCID: PMC8865841 DOI: 10.1039/d1cp03566e] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
A structure-based quantitative calculation of excitonic couplings between photosynthetic pigments has to describe the dynamical polarization of the protein/solvent environment of the pigments, giving rise to reaction field and screening effects. Here, this challenging problem is approached by combining the fragment molecular orbital (FMO) method with the polarizable continuum model (PCM). The method is applied to compute excitonic couplings between chlorophyll a (Chl a) pigments of the water-soluble chlorophyll-binding protein (WSCP). By calibrating the vacuum dipole strength of the 0–0 transition of the Chl a chromophores according to experimental data, an excellent agreement between calculated and experimental linear absorption and circular dichroism spectra of WSCP is obtained. The effect of the mutual polarization of the pigment ground states is calculated to be very small. The simple Poisson-Transition-charge-from-Electrostatic-potential (Poisson-TrEsp) method is found to accurately describe the screening part of the excitonic coupling, obtained with FMO/PCM. Taking into account that the reaction field effects of the latter method can be described by a scalar constant leads to an improvement of Poisson-TrEsp that is expected to provide the basis for simple and realistic calculations of optical spectra and energy transfer in photosynthetic light-harvesting complexes. In addition, we present an expression for the estimation of Huang–Rhys factors of high-frequency pigment vibrations from experimental fluorescence line-narrowing spectra that takes into account the redistribution of oscillator strength by the interpigment excitonic coupling. Application to WSCP results in corrected Huang–Rhys factors that are less than one third of the original values obtained by the standard electronic two-state analysis that neglects the above redistribution. These factors are important for the estimation of the dipole strength of the 0–0 transition of the chromophores and for the development of calculation schemes for the spectral density of the exciton-vibrational coupling. The importance of reaction field and screening effects on the excitonic couplings is demonstrated, and from quantum-chemical calculations a single scaling factor is derived that can be used to improve simple models based on the Poisson equation.![]()
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Affiliation(s)
- Christian Friedl
- Institut für Theoretische Physik, Johannes Kepler Universität Linz, Altenberger Str. 69, 4040 Linz, Austria.
| | - Dmitri G Fedorov
- Research Center for Computational Design of Advanced Functional Materials (CD-FMat), National Institute of Advanced Industrial Science and Technology (AIST), Central 2, Umezono 1-1-1, Tsukuba, 305-8568, Japan.
| | - Thomas Renger
- Institut für Theoretische Physik, Johannes Kepler Universität Linz, Altenberger Str. 69, 4040 Linz, Austria.
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7
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Ara AM, Ahmed MK, D'Haene S, van Roon H, Ilioaia C, van Grondelle R, Wahadoszamen M. Absence of far-red emission band in aggregated core antenna complexes. Biophys J 2021; 120:1680-1691. [PMID: 33675767 DOI: 10.1016/j.bpj.2021.02.037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 01/31/2021] [Accepted: 02/22/2021] [Indexed: 10/22/2022] Open
Abstract
Reported herein is a Stark fluorescence spectroscopy study performed on photosystem II core antenna complexes CP43 and CP47 in their native and aggregated states. The systematic mathematical modeling of the Stark fluorescence spectra with the aid of conventional Liptay formalism revealed that induction of aggregation in both the core antenna complexes via detergent removal results in a single quenched species characterized by a remarkably broad and inhomogenously broadened emission lineshape peaking around 700 nm. The quenched species possesses a fairly large magnitude of charge-transfer character. From the analogy with the results from aggregated peripheral antenna complexes, the quenched species is thought to originate from the enhanced chlorophyll-chlorophyll interaction due to aggregation. However, in contrast, aggregation of both core antenna complexes did not produce a far-red emission band at ∼730 nm, which was identified in most of the aggregated peripheral antenna complexes. The 730-nm emission band of the aggregated peripheral antenna complexes was attributed to the enhanced chlorophyll-carotenoid (lutein1) interaction in the terminal emitter locus. Therefore, it is very likely that the no occurrence of the far-red band in the aggregated core antenna complexes is directly related to the absence of lutein1 in their structures. The absence of the far-red band also suggests the possibility that aggregation-induced conformational change of the core antenna complexes does not yield a chlorophyll-carotenoid interaction associated energy dissipation channel.
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Affiliation(s)
- Anjue Mane Ara
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, the Netherlands; Department of Physics, Jagannath University, Dhaka, Bangladesh
| | | | - Sandrine D'Haene
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, the Netherlands
| | - Henny van Roon
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, the Netherlands
| | - Cristian Ilioaia
- Institute for Integrative Biology of the Cell, CEA, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Rienk van Grondelle
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, the Netherlands
| | - Md Wahadoszamen
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, the Netherlands; Department of Physics, University of Dhaka, Dhaka, Bangladesh.
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8
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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: 31] [Impact Index Per Article: 7.8] [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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9
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Kitoh-Nishioka H, Shigeta Y, Itoh S, Kimura A. Excitonic Coupling on a Heliobacterial Symmetrical Type-I Reaction Center: Comparison with Photosystem I. J Phys Chem B 2019; 124:389-403. [DOI: 10.1021/acs.jpcb.9b11290] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Hirotaka Kitoh-Nishioka
- JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
- Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan
| | - Yasuteru Shigeta
- Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan
| | - Shigeru Itoh
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Akihiro Kimura
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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10
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Häse F, Roch LM, Aspuru-Guzik A. Chimera: enabling hierarchy based multi-objective optimization for self-driving laboratories. Chem Sci 2018; 9:7642-7655. [PMID: 30393525 PMCID: PMC6182568 DOI: 10.1039/c8sc02239a] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 08/04/2018] [Indexed: 12/23/2022] Open
Abstract
Finding the ideal conditions satisfying multiple pre-defined targets simultaneously is a challenging decision-making process, which impacts science, engineering, and economics. Additional complexity arises for tasks involving experimentation or expensive computations, as the number of evaluated conditions must be kept low. We propose Chimera as a general purpose achievement scalarizing function for multi-target optimization where evaluations are the limiting factor. Chimera combines concepts of a priori scalarizing with lexicographic approaches and is applicable to any set of n unknown objectives. Importantly, it does not require detailed prior knowledge about individual objectives. The performance of Chimera is demonstrated on several well-established analytic multi-objective benchmark sets using different single-objective optimization algorithms. We further illustrate the applicability and performance of Chimera with two practical examples: (i) the auto-calibration of a virtual robotic sampling sequence for direct-injection, and (ii) the inverse-design of a four-pigment excitonic system for an efficient energy transport. The results indicate that Chimera enables a wide class of optimization algorithms to rapidly find ideal conditions. Additionally, the presented applications highlight the interpretability of Chimera to corroborate design choices for tailoring system parameters.
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Affiliation(s)
- Florian Häse
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , Massachusetts 02138 , USA . ; Tel: +1-617-384-8188
| | - Loïc M Roch
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , Massachusetts 02138 , USA . ; Tel: +1-617-384-8188
| | - Alán Aspuru-Guzik
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , Massachusetts 02138 , USA . ; Tel: +1-617-384-8188
- Department of Chemistry and Department of Computer Science , University of Toronto , Toronto , Ontario M5S3H6 , Canada
- Vector Institute for Artificial Intelligence , Toronto , Ontario M5S1M1 , Canada
- Canadian Institute for Advanced Research (CIFAR) Senior Fellow , Toronto , Ontario M5S1M1 , Canada
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11
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Pan J, Gelzinis A, Chorošajev V, Vengris M, Senlik SS, Shen JR, Valkunas L, Abramavicius D, Ogilvie JP. Ultrafast energy transfer within the photosystem II core complex. Phys Chem Chem Phys 2018; 19:15356-15367. [PMID: 28574545 DOI: 10.1039/c7cp01673e] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We report 2D electronic spectroscopy on the photosystem II core complex (PSII CC) at 77 K under different polarization conditions. A global analysis of the high time-resolution 2D data shows rapid, sub-100 fs energy transfer within the PSII CC. It also reveals the 2D spectral signatures of slower energy equilibration processes occurring on several to hundreds of picosecond time scales that are consistent with previous work. Using a recent structure-based model of the PSII CC [Y. Shibata, S. Nishi, K. Kawakami, J. R. Shen and T. Renger, J. Am. Chem. Soc., 2013, 135, 6903], we simulate the energy transfer in the PSII CC by calculating auxiliary time-resolved fluorescence spectra. We obtain the observed sub-100 fs evolution, even though the calculated electronic energy shows almost no dynamics at early times. On the other hand, the electronic-vibrational interaction energy increases considerably over the same time period. We conclude that interactions with vibrational degrees of freedom not only induce population transfer between the excitonic states in the PSII CC, but also reshape the energy landscape of the system. We suggest that the experimentally observed ultrafast energy transfer is a signature of excitonic-polaron formation.
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Affiliation(s)
- Jie Pan
- Department of Physics, University of Michigan, Ann Arbor, 48109, USA.
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12
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Häse F, Kreisbeck C, Aspuru-Guzik A. Machine learning for quantum dynamics: deep learning of excitation energy transfer properties. Chem Sci 2017; 8:8419-8426. [PMID: 29619189 PMCID: PMC5863613 DOI: 10.1039/c7sc03542j] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2017] [Accepted: 10/23/2017] [Indexed: 12/20/2022] Open
Abstract
Understanding the relationship between the structure of light-harvesting systems and their excitation energy transfer properties is of fundamental importance in many applications including the development of next generation photovoltaics. Natural light harvesting in photosynthesis shows remarkable excitation energy transfer properties, which suggests that pigment-protein complexes could serve as blueprints for the design of nature inspired devices. Mechanistic insights into energy transport dynamics can be gained by leveraging numerically involved propagation schemes such as the hierarchical equations of motion (HEOM). Solving these equations, however, is computationally costly due to the adverse scaling with the number of pigments. Therefore virtual high-throughput screening, which has become a powerful tool in material discovery, is less readily applicable for the search of novel excitonic devices. We propose the use of artificial neural networks to bypass the computational limitations of established techniques for exploring the structure-dynamics relation in excitonic systems. Once trained, our neural networks reduce computational costs by several orders of magnitudes. Our predicted transfer times and transfer efficiencies exhibit similar or even higher accuracies than frequently used approximate methods such as secular Redfield theory.
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Affiliation(s)
- Florian Häse
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , 02138 , USA . ; ; Tel: +1-617-384-8188
| | - Christoph Kreisbeck
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , 02138 , USA . ; ; Tel: +1-617-384-8188
| | - Alán Aspuru-Guzik
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , 02138 , USA . ; ; Tel: +1-617-384-8188
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13
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Müh F, Plöckinger M, Renger T. Electrostatic Asymmetry in the Reaction Center of Photosystem II. J Phys Chem Lett 2017; 8:850-858. [PMID: 28151674 DOI: 10.1021/acs.jpclett.6b02823] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The exciton Hamiltonian of the chlorophyll (Chl) and pheophytin (Pheo) pigments in the reaction center (RC) of photosystem II is computed based on recent crystal structures by using the Poisson-Boltzmann/quantum-chemical method. Computed site energies largely confirm a previous model inferred from fits of optical spectra, in which ChlD1 has the lowest site energy, while that of PheoD1 is higher than that of PheoD2. The latter assignment has been challenged recently under reference to mutagenesis experiments. We argue that these data are not in contradiction to our results. We conclude that ChlD1 is the primary electron donor in both isolated RCs and intact core complexes at least at cryogenic temperatures. The main source of asymmetry in site energies is the charge distribution in the protein. Because many small contributions from various structural elements have to be taken into account, it can be assumed that this asymmetry was established in evolution by global optimization of the RC protein.
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Affiliation(s)
- Frank Müh
- Institute of Theoretical Physics, Department of Theoretical Biophysics, Johannes Kepler University Linz , Altenberger Strasse 69, AT-4040 Linz, Austria
| | - Melanie Plöckinger
- Institute of Theoretical Physics, Department of Theoretical Biophysics, Johannes Kepler University Linz , Altenberger Strasse 69, AT-4040 Linz, Austria
| | - Thomas Renger
- Institute of Theoretical Physics, Department of Theoretical Biophysics, Johannes Kepler University Linz , Altenberger Strasse 69, AT-4040 Linz, Austria
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14
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Kreisbeck C, Aspuru-Guzik A. Efficiency of energy funneling in the photosystem II supercomplex of higher plants. Chem Sci 2016; 7:4174-4183. [PMID: 30155062 PMCID: PMC6014079 DOI: 10.1039/c5sc04296h] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 02/24/2016] [Indexed: 01/16/2023] Open
Abstract
The investigation of energy transfer properties in photosynthetic multi-protein networks gives insight into their underlying design principles. Here, we discuss the excitonic energy transfer mechanisms of the photosystem II (PS-II) C2S2M2 supercomplex, which is the largest isolated functional unit of the photosynthetic apparatus of higher plants. Despite the lack of a definite energy gradient in C2S2M2, we show that the energy transfer is directed by relaxation to low energy states. C2S2M2 is not organized to form pathways with strict energetically downhill transfer, which has direct consequences for the transfer efficiency, transfer pathways and transfer limiting steps. The exciton dynamics is sensitive to small changes in the energetic layout which, for instance, are induced by the reorganization of vibrational coordinates. In order to incorporate the reorganization process in our numerical simulations, we go beyond rate equations and use the hierarchically coupled equation of motion approach (HEOM). While transfer from the peripheral antenna to the proteins in proximity to the reaction center occurs on a faster time scale, the final step of the energy transfer to the RC core is rather slow, and thus the limiting step in the transfer chain. Our findings suggest that the structure of the PS-II supercomplex guarantees photoprotection rather than optimized efficiency.
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Affiliation(s)
- Christoph Kreisbeck
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , MA , USA . ;
| | - Alán Aspuru-Guzik
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , MA , USA . ;
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15
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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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16
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Abstract
The design of optimal light-harvesting (supra)molecular systems and materials is one of the most challenging frontiers of science. Theoretical methods and computational models play a fundamental role in this difficult task, as they allow the establishment of structural blueprints inspired by natural photosynthetic organisms that can be applied to the design of novel artificial light-harvesting devices. Among theoretical strategies, the application of quantum chemical tools represents an important reality that has already reached an evident degree of maturity, although it still has to show its real potentials. This Review presents an overview of the state of the art of this strategy, showing the actual fields of applicability but also indicating its current limitations, which need to be solved in future developments.
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Affiliation(s)
- Carles Curutchet
- Departament de Fisicoquímica, Facultat de Farmàcia, Universitat de Barcelona , Av. Joan XXIII s/n, 08028 Barcelona, Spain
| | - Benedetta Mennucci
- Dipartimento di Chimica e Chimica Industriale, University of Pisa , via G. Moruzzi 13, 56124 Pisa, Italy
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17
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Mohamed A, Nagao R, Noguchi T, Fukumura H, Shibata Y. Structure-Based Modeling of Fluorescence Kinetics of Photosystem II: Relation between Its Dimeric Form and Photoregulation. J Phys Chem B 2016; 120:365-76. [PMID: 26714062 DOI: 10.1021/acs.jpcb.5b09103] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A photosystem II-enriched membrane (PSII-em) consists of the PSII core complex (PSII-cc) which is surrounded by peripheral antenna complexes. PSII-cc consists of two core antenna (CP43 and CP47) and the reaction center (RC) complex. Time-resolved fluorescence spectra of a PSII-em were measured at 77 K. The data were globally analyzed with a new compartment model, which has a minimum number of compartments and is consistent with the structure of PSII-cc. The reliability of the model was investigated by fitting the data of different experimental conditions. From the analysis, the energy-transfer time constants from the peripheral antenna to CP47 and CP43 were estimated to be 20 and 35 ps, respectively. With an exponential time constant of 320 ps, the excitation energy was estimated to accumulate in the reddest chlorophyll (Red Chl), giving a 692 nm fluorescence peak. The excited state on the Red Chl was confirmed to be quenched upon the addition of an oxidant, as reported previously. The calculations based on the Förster theory predicted that the excitation energy on Chl29 is quenched by ChlZD1(+), which is a redox active but not involved in the electron-transfer chain, located in the D1 subunit of RC, in the other monomer with an exponential time constant of 75 ps. This quenching pathway is consistent with our structure-based simulation of PSII-cc, which assigned Chl29 as the Red Chl. On the other hand, the alternative interpretation assigning Chl26 as the Red Chl was not excluded. The excited Chl26 was predicted to be quenched by another redox active ChlZD2(+) in the D2 subunit of RC in the same monomer unit with an exponential time constant of 88 ps.
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Affiliation(s)
- Ahmed Mohamed
- Department of Chemistry, Graduate School of Science, Tohoku University , Aramaki Aza Aoba, Aoba-Ku, Sendai 980-8578, Japan
| | - Ryo Nagao
- Division of Material Science (Physics), Graduate School of Science, Nagoya University , Furo-Cho, Chikusa-Ku, Nagoya 464-8602, Japan
| | - Takumi Noguchi
- Division of Material Science (Physics), Graduate School of Science, Nagoya University , Furo-Cho, Chikusa-Ku, Nagoya 464-8602, Japan
| | - Hiroshi Fukumura
- Department of Chemistry, Graduate School of Science, Tohoku University , Aramaki Aza Aoba, Aoba-Ku, Sendai 980-8578, Japan
| | - Yutaka Shibata
- Department of Chemistry, Graduate School of Science, Tohoku University , Aramaki Aza Aoba, Aoba-Ku, Sendai 980-8578, Japan
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18
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Chmeliov J, Trinkunas G, van Amerongen H, Valkunas L. Excitation migration in fluctuating light-harvesting antenna systems. PHOTOSYNTHESIS RESEARCH 2016; 127:49-60. [PMID: 25605669 DOI: 10.1007/s11120-015-0083-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 01/07/2015] [Indexed: 06/04/2023]
Abstract
Complex multi-exponential fluorescence decay kinetics observed in various photosynthetic systems like photosystem II (PSII) have often been explained by the reversible quenching mechanism of the charge separation taking place in the reaction center (RC) of PSII. However, this description does not account for the intrinsic dynamic disorder of the light-harvesting proteins as well as their fluctuating dislocations within the antenna, which also facilitate the repair of RCs, state transitions, and the process of non-photochemical quenching. Since dynamic fluctuations result in varying connectivity between pigment-protein complexes, they can also lead to non-exponential excitation decay kinetics. Based on this presumption, we have recently proposed a simple conceptual model describing excitation diffusion in a continuous medium and accounting for possible variations of the excitation transfer pathways. In the current work, this model is further developed and then applied to describe fluorescence kinetics originating from very diverse antenna systems, ranging from PSII of various sizes to LHCII aggregates and even the entire thylakoid membrane. In all cases, complex multi-exponential fluorescence kinetics are perfectly reproduced on the entire relevant time scale without assuming any radical pair equilibration at the side of the excitation quencher, but using just a few parameters reflecting the mean excitation energy transfer rate as well as the overall average organization of the photosynthetic antenna.
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Affiliation(s)
- Jevgenij Chmeliov
- Department of Theoretical Physics, Faculty of Physics, Vilnius University, Saulėtekio Ave. 9, 10222, Vilnius, Lithuania
- Institute of Physics, Center for Physical Sciences and Technology, Gostauto 11, 01108, Vilnius, Lithuania
| | - Gediminas Trinkunas
- Department of Theoretical Physics, Faculty of Physics, Vilnius University, Saulėtekio Ave. 9, 10222, Vilnius, Lithuania
- Institute of Physics, Center for Physical Sciences and Technology, Gostauto 11, 01108, Vilnius, Lithuania
| | - Herbert van Amerongen
- Laboratory of Biophysics, Wageningen University, P.O. Box 8128, 6700, Wageningen, The Netherlands
| | - Leonas Valkunas
- Department of Theoretical Physics, Faculty of Physics, Vilnius University, Saulėtekio Ave. 9, 10222, Vilnius, Lithuania.
- Institute of Physics, Center for Physical Sciences and Technology, Gostauto 11, 01108, Vilnius, Lithuania.
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19
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Novoderezhkin VI, Croce R, Wahadoszamen M, Polukhina I, Romero E, van Grondelle R. Mixing of exciton and charge-transfer states in light-harvesting complex Lhca4. Phys Chem Chem Phys 2016; 18:19368-77. [DOI: 10.1039/c6cp02225a] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Structure-based modeling of spectra of the wild-type Lhca4 and NH mutant enables us to build the exciton model of the complex that includes a charge-transfer state mixed with the excited-state manifold.
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Affiliation(s)
| | - Roberta Croce
- Department of Biophysics
- Faculty of Sciences
- VU University Amsterdam
- 1081 HV Amsterdam
- The Netherlands
| | - Md. Wahadoszamen
- Department of Biophysics
- Faculty of Sciences
- VU University Amsterdam
- 1081 HV Amsterdam
- The Netherlands
| | - Iryna Polukhina
- Department of Biophysics
- Faculty of Sciences
- VU University Amsterdam
- 1081 HV Amsterdam
- The Netherlands
| | - Elisabet Romero
- Department of Biophysics
- Faculty of Sciences
- VU University Amsterdam
- 1081 HV Amsterdam
- The Netherlands
| | - Rienk van Grondelle
- Department of Biophysics
- Faculty of Sciences
- VU University Amsterdam
- 1081 HV Amsterdam
- The Netherlands
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20
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Xiao QJ, Li ZG, Yang J, He Q, Xi L, Du LF. Heat-induced unfolding of apo-CP43 studied by fluorescence spectroscopy and CD spectroscopy. PHOTOSYNTHESIS RESEARCH 2015; 126:427-435. [PMID: 26071019 DOI: 10.1007/s11120-015-0166-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 06/03/2015] [Indexed: 06/04/2023]
Abstract
CP43 is a chlorophyll-binding protein, which acts as a conduit for the excitation energy transfer. The thermal stability of apo-CP43 was studied by intrinsic fluorescence, exogenous ANS fluorescence, and circular dichroism spectroscopy. Under heat treatment, the structure of apo-CP43 changed and existed transition state occurred between 56 and 62 °C by the intrinsic, exogenous ANS fluorescence and the analysis of hydrophobicity. Besides, the isosbestic point of the sigmoidal curve was 58.10 ± 1.02 °C by calculating α-helix transition and the Tm was 56.45 ± 0.52 and 55.59 ± 0.68 °C by calculating the unfolded fraction of tryptophan and tyrosine fluorescence, respectively. During the process of unfolding, the hydrophobic structure of C-terminal segment firstly started to expose at 40 °C, and then the hydrophobic cluster adjacent to the N-terminal segment also gradually exposed to hydrophilic environment with increasing temperature. Our results indicated that heat treatment, especially above 40 °C, has an important impact on the structural stability of apo-CP43.
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Affiliation(s)
- Qing-Jie Xiao
- Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China
| | - Zai-Geng Li
- Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China
| | - Jiao Yang
- Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China
| | - Qing He
- Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China
| | - Lei Xi
- Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China
| | - Lin-Fang Du
- Key Laboratory of Bio-resources and Eco-environment of the Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China.
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21
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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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22
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Hall J, Renger T, Picorel R, Krausz E. Circularly polarized luminescence spectroscopy reveals low-energy excited states and dynamic localization of vibronic transitions in CP43. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1857:115-128. [PMID: 26449206 DOI: 10.1016/j.bbabio.2015.09.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 09/23/2015] [Accepted: 09/29/2015] [Indexed: 11/26/2022]
Abstract
Circularly polarized luminescence (CPL) spectroscopy is an established but relatively little-used technique that monitors the chirality of an emission. When applied to photosynthetic pigment assemblies, we find that CPL provides sensitive and detailed information on low-energy exciton states, reflecting the interactions, site energies and geometries of interacting pigments. CPL is the emission analog of circular dichroism (CD) and thus spectra explore the optical activity only of fluorescent states of the pigment-protein complex and consequently the nature of the lowest-energy excited states (trap states), whose study is a critical area of photosynthesis research. In this work, we develop the new approach of temperature-dependent CPL spectroscopy, over the 2-120 K temperature range, and apply it to the CP43 proximal antenna protein of photosystem II. Our results confirm strong excitonic interactions for at least one of the two well-established emitting states of CP43 named "A" and "B". Previous structure-based models of CP43 spectra are evaluated in the light of the new CPL data. Our analysis supports the assignments of Shibata et al. [Shibata et al. J. Am. Chem. Soc. 135 (2013) 6903-6914], particularly for the highly-delocalized B-state. This state dominates CPL spectra and is attributed predominantly to chlorophyll a's labeled Chl 634 and Chl 636 (alternatively labeled Chl 43 and 45 by Shibata et al.). The absence of any CPL intensity in intramolecular vibrational sidebands associated with the delocalized "B" excited state is attributed to the dynamic localization of intramolecular vibronic transitions.
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Affiliation(s)
- Jeremy Hall
- Research School of Chemistry, Australian National University, Canberra, Australia
| | - Thomas Renger
- Institut für Theoretische Physik, Johannes Kepler Universität, Linz, Austria
| | - Rafael Picorel
- Estacion Experimental de Aula Dei (CSIC), Avda. Montañana, Zaragoza, Spain
| | - Elmars Krausz
- Research School of Chemistry, Australian National University, Canberra, Australia.
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23
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Chen J, Kell A, Acharya K, Kupitz C, Fromme P, Jankowiak R. Critical assessment of the emission spectra of various photosystem II core complexes. PHOTOSYNTHESIS RESEARCH 2015; 124:253-265. [PMID: 25832780 DOI: 10.1007/s11120-015-0128-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2014] [Accepted: 03/23/2015] [Indexed: 06/04/2023]
Abstract
We evaluate low-temperature (low-T) emission spectra of photosystem II core complexes (PSII-cc) previously reported in the literature, which are compared with emission spectra of PSII-cc obtained in this work from spinach and for dissolved PSII crystals from Thermosynechococcus (T.) elongatus. This new spectral dataset is used to interpret data published on membrane PSII (PSII-m) fragments from spinach and Chlamydomonas reinhardtii, as well as PSII-cc from T. vulcanus and intentionally damaged PSII-cc from spinach. This study offers new insight into the assignment of emission spectra reported on PSII-cc from different organisms. Previously reported spectra are also compared with data obtained at different saturation levels of the lowest energy state(s) of spinach and T. elongatus PSII-cc via hole burning in order to provide more insight into emission from bleached and/or photodamaged complexes. We show that typical low-T emission spectra of PSII-cc (with closed RCs), in addition to the 695 nm fluorescence band assigned to the intact CP47 complex (Reppert et al. J Phys Chem B 114:11884-11898, 2010), can be contributed to by several emission bands, depending on sample quality. Possible contributions include (i) a band near 690-691 nm that is largely reversible upon temperature annealing, proving that the band originates from CP47 with a bleached low-energy state near 693 nm (Neupane et al. J Am Chem Soc 132:4214-4229, 2010; Reppert et al. J Phys Chem B 114:11884-11898, 2010); (ii) CP43 emission at 683.3 nm (not at 685 nm, i.e., the F685 band, as reported in the literature) (Dang et al. J Phys Chem B 112:9921-9933, 2008; Reppert et al. J Phys Chem B 112:9934-9947, 2008); (iii) trap emission from destabilized CP47 complexes near 691 nm (FT1) and 685 nm (FT2) (Neupane et al. J Am Chem Soc 132:4214-4229, 2010); and (iv) emission from the RC pigments near 686-687 nm. We suggest that recently reported emission of single PSII-cc complexes from T. elongatus may not represent intact complexes, while those obtained for T. elongatus presented in this work most likely represent intact PSII-cc, since they are nearly indistinguishable from emission spectra obtained for various PSII-m fragments.
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Affiliation(s)
- Jinhai Chen
- Department of Chemistry, Kansas State University, Manhattan, KS, 66506, USA
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24
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Skandary S, Hussels M, Konrad A, Renger T, Müh F, Bommer M, Zouni A, Meixner A, Brecht M. Variation of exciton-vibrational coupling in photosystem II core complexes from Thermosynechococcus elongatus as revealed by single-molecule spectroscopy. J Phys Chem B 2015; 119:4203-10. [PMID: 25708355 PMCID: PMC4368080 DOI: 10.1021/jp510631x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Revised: 02/20/2015] [Indexed: 01/01/2023]
Abstract
The spectral properties and dynamics of the fluorescence emission of photosystem II core complexes are investigated by single-molecule spectroscopy at 1.6 K. The emission spectra are dominated by sharp zero-phonon lines (ZPLs). The sharp ZPLs are the result of weak to intermediate exciton-vibrational coupling and slow spectral diffusion. For several data sets, it is possible to surpass the effect of spectral diffusion by applying a shifting algorithm. The increased signal-to-noise ratio enables us to determine the exciton-vibrational coupling strength (Huang-Rhys factor) with high precision. The Huang-Rhys factors vary between 0.03 and 0.8. The values of the Huang-Rhys factors show no obvious correlation between coupling strength and wavelength position. From this result, we conclude that electrostatic rather than exchange or dispersive interactions are the main contributors to the exciton-vibrational coupling in this system.
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Affiliation(s)
| | - Martin Hussels
- IPTC
and Lisa+ Center, Universität Tübingen, Tübingen, Germany
| | | | - Thomas Renger
- Institut
für Theoretische Physik, Johannes
Kepler Universität, Linz, Austria
| | - Frank Müh
- Institut
für Theoretische Physik, Johannes
Kepler Universität, Linz, Austria
| | - Martin Bommer
- Institut
für Biologie, Humboldt Universität
zu Berlin, Berlin, Germany
| | - Athina Zouni
- Institut
für Biologie, Humboldt Universität
zu Berlin, Berlin, Germany
| | | | - Marc Brecht
- IPTC
and Lisa+ Center, Universität Tübingen, Tübingen, Germany
- Zurich University
of Applied Science Winterthur (ZHAW), Winterthur, Switzerland
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25
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Chmeliov J, Bricker WP, Lo C, Jouin E, Valkunas L, Ruban AV, Duffy CDP. An ‘all pigment’ model of excitation quenching in LHCII. Phys Chem Chem Phys 2015; 17:15857-67. [DOI: 10.1039/c5cp01905b] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
This work presents the first all-pigment microscopic model of a major light-harvesting complex of plants and the first attempt to capture the dissipative character of the known structure.
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Affiliation(s)
- Jevgenij Chmeliov
- Department of Theoretical Physics
- Faculty of Physics
- Vilnius University
- LT-10222 Vilnius
- Lithuania
| | - William P. Bricker
- Department of Energy
- Environmental and Chemical Engineering
- Washington University in St. Louis
- Saint Louis
- USA
| | - Cynthia Lo
- Department of Energy
- Environmental and Chemical Engineering
- Washington University in St. Louis
- Saint Louis
- USA
| | - Elodie Jouin
- The School of Biological and Chemical Sciences
- Queen Mary
- University of London
- London E1 4NS
- UK
| | - Leonas Valkunas
- Department of Theoretical Physics
- Faculty of Physics
- Vilnius University
- LT-10222 Vilnius
- Lithuania
| | - Alexander V. Ruban
- The School of Biological and Chemical Sciences
- Queen Mary
- University of London
- London E1 4NS
- UK
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26
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Müh F, Lindorfer D, Schmidt am Busch M, Renger T. Towards a structure-based exciton Hamiltonian for the CP29 antenna of photosystem II. Phys Chem Chem Phys 2014; 16:11848-63. [PMID: 24603694 DOI: 10.1039/c3cp55166k] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
Abstract
The exciton Hamiltonian pertaining to the first excited states of chlorophyll (Chl) a and b pigments in the minor light-harvesting complex CP29 of plant photosystem II is determined based on the recent crystal structure at 2.8 Å resolution applying a combined quantum chemical/electrostatic approach as used earlier for the major light-harvesting complex LHCII. Two electrostatic methods for the calculation of the local transition energies (site energies), referred to as the Poisson-Boltzmann/quantum chemical (PBQC) and charge density coupling (CDC) method, which differ in the way the polarizable environment of the pigments is described, are compared and found to yield comparable results, when tested against fits of measured optical spectra (linear absorption, linear dichroism, circular dichroism, and fluorescence). The crystal structure shows a Chl a/b ratio of 2.25, whereas a ratio between 2.25 and 3.0 can be estimated from the simulation of experimental spectra. Thus, it is possible that up to one Chl b is lost in CP29 samples. The lowest site energy is found to be located at Chl a604 close to neoxanthin. This assignment is confirmed by the simulation of wild-type-minus-mutant difference spectra of reconstituted CP29, where a tyrosine residue next to Chl a604 is modified in the mutant. Nonetheless, the terminal emitter domain (TED), i.e. the pigments contributing mostly to the lowest exciton state, is found at the Chl a611-a612-a615 trimer due to strong excitonic coupling between these pigments, with the largest contributions from Chls a611 and a612. A major difference between CP29 and LHCII is that Chl a610 is not the energy sink in CP29, which is presumably to a large extent due to the replacement of a lysine residue with alanine close to the TED.
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Affiliation(s)
- Frank Müh
- Institute for Theoretical Physics, Johannes Kepler University Linz, Altenberger Str. 69, 4040 Linz, Austria.
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27
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Chmeliov J, Trinkunas G, van Amerongen H, Valkunas L. Light harvesting in a fluctuating antenna. J Am Chem Soc 2014; 136:8963-72. [PMID: 24870124 DOI: 10.1021/ja5027858] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
One of the major players in oxygenic photosynthesis, photosystem II (PSII), exhibits complex multiexponential fluorescence decay kinetics that for decades has been ascribed to reversible charge separation taking place in the reaction center (RC). However, in this description the protein dynamics is not taken into consideration. The intrinsic dynamic disorder of the light-harvesting proteins along with their fluctuating dislocations within the antenna inevitably result in varying connectivity between pigment-protein complexes and therefore can also lead to nonexponential excitation decay kinetics. On the basis of this presumption, we propose a simple conceptual model describing excitation diffusion in a continuous medium and accounting for possible variations of the excitation transfer rates. Recently observed fluorescence kinetics of PSII of different sizes are perfectly reproduced with only two adjustable parameters instead of the many decay times and amplitudes required in standard analysis procedures; no charge recombination in the RC is required. The model is also able to provide valuable information about the structural and functional organization of the photosynthetic antenna and in a straightforward way solves various contradictions currently existing in the literature.
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Affiliation(s)
- Jevgenij Chmeliov
- Department of Theoretical Physics, Faculty of Physics, Vilnius University , Sauletekio Avenue 9, LT-10222 Vilnius, Lithuania
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28
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Reimers JR, Cai ZL, Kobayashi R, Rätsep M, Freiberg A, Krausz E. Formation of water–chlorophyll clusters in dilute samples of chlorophyll-a in ether at low temperature. Phys Chem Chem Phys 2014; 16:2323-30. [PMID: 24352346 DOI: 10.1039/c3cp53729c] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Jeffrey R Reimers
- School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia.
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29
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Renger T, Madjet MEA, Schmidt am Busch M, Adolphs J, Müh F. Structure-based modeling of energy transfer in photosynthesis. PHOTOSYNTHESIS RESEARCH 2013; 116:367-388. [PMID: 23921525 DOI: 10.1007/s11120-013-9893-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2013] [Accepted: 07/08/2013] [Indexed: 06/02/2023]
Abstract
We provide a minimal model for a structure-based simulation of excitation energy transfer in pigment-protein complexes (PPCs). In our treatment, the PPC is assembled from its building blocks. The latter are defined such that electron exchange occurs only within, but not between these units. The variational principle is applied to investigate how the Coulomb interaction between building blocks changes the character of the electronic states of the PPC. In this way, the standard exciton Hamiltonian is obtained from first principles and a hierarchy of calculation schemes for the parameters of this Hamiltonian arises. Possible extensions of this approach are discussed concerning (i) the inclusion of dispersive site energy shifts and (ii) the inclusion of electron exchange between pigments. First results on electron exchange within the special pair of photosystem II of cyanobacteria and higher plants are presented and compared with earlier results on purple bacteria. In the last part of this mini-review, the coupling of electronic and nuclear degrees of freedom is considered. First, the standard exciton-vibrational Hamiltonian is parameterized with the help of a normal mode analysis of the PPC. Second, dynamical theories are discussed that exploit this Hamiltonian in the study of dissipative exciton motion.
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Affiliation(s)
- Thomas Renger
- Institut für Theoretische Physik, Johannes Kepler Universität Linz, Altenberger Str. 69, 4040, Linz, Austria,
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Reimers JR, Cai ZL, Kobayashi R, Rätsep M, Freiberg A, Krausz E. Assignment of the Q-bands of the chlorophylls: coherence loss via Qx - Qy mixing. Sci Rep 2013; 3:2761. [PMID: 24067303 PMCID: PMC3783888 DOI: 10.1038/srep02761] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 09/03/2013] [Indexed: 01/12/2023] Open
Abstract
We provide a new and definitive spectral assignment for the absorption, emission, high-resolution fluorescence excitation, linear dichroism, and/or magnetic circular dichroism spectra of 32 chlorophyllides in various environments. This encompases all data used to justify previous assignments and provides a simple interpretation of unexplained complex decoherence phenomena associated with Qx → Qy relaxation. Whilst most chlorophylls conform to the Gouterman model and display two independent transitions Qx (S2) and Qy (S1), strong vibronic coupling inseparably mixes these states in chlorophyll-a. This spreads x-polarized absorption intensity over the entireQ-band system to influence all exciton-transport, relaxation and coherence properties of chlorophyll-based photosystems. The fraction of the total absorption intensity attributed to Qx ranges between 7% and 33%, depending on chlorophyllide and coordination, and is between 10% and 25% for chlorophyll-a. CAM-B3LYP density-functional-theory calculations of the band origins, relative intensities, vibrational Huang-Rhys factors, and vibronic coupling strengths fully support this new assignment.
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Bennett DIG, Amarnath K, Fleming GR. A structure-based model of energy transfer reveals the principles of light harvesting in photosystem II supercomplexes. J Am Chem Soc 2013; 135:9164-73. [PMID: 23679235 DOI: 10.1021/ja403685a] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Photosystem II (PSII) initiates photosynthesis in plants through the absorption of light and subsequent conversion of excitation energy to chemical energy via charge separation. The pigment binding proteins associated with PSII assemble in the grana membrane into PSII supercomplexes and surrounding light harvesting complex II trimers. To understand the high efficiency of light harvesting in PSII requires quantitative insight into energy transfer and charge separation in PSII supercomplexes. We have constructed the first structure-based model of energy transfer in PSII supercomplexes. This model shows that the kinetics of light harvesting cannot be simplified to a single rate limiting step. Instead, substantial contributions arise from both excitation diffusion through the antenna pigments and transfer from the antenna to the reaction center (RC), where charge separation occurs. Because of the lack of a rate-limiting step, fitting kinetic models to fluorescence lifetime data cannot be used to derive mechanistic insight on light harvesting in PSII. This model will clarify the interpretation of chlorophyll fluorescence data from PSII supercomplexes, grana membranes, and leaves.
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Affiliation(s)
- Doran I G Bennett
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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Shibata Y, Nishi S, Kawakami K, Shen JR, Renger T. Photosystem II does not possess a simple excitation energy funnel: time-resolved fluorescence spectroscopy meets theory. J Am Chem Soc 2013; 135:6903-14. [PMID: 23537277 PMCID: PMC3650659 DOI: 10.1021/ja312586p] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
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The experimentally
obtained time-resolved fluorescence spectra
of photosystem II (PS II) core complexes, purified from a thermophilic
cyanobacterium Thermosynechococcus vulcanus, at 5–180 K are compared with simulations. Dynamic localization
effects of excitons are treated implicitly by introducing exciton
domains of strongly coupled pigments. Exciton relaxations within a
domain and exciton transfers between domains are treated on the basis
of Redfield theory and generalized Förster theory, respectively.
The excitonic couplings between the pigments are calculated by a quantum
chemical/electrostatic method (Poisson-TrEsp). Starting with previously
published values, a refined set of site energies of the pigments is
obtained through optimization cycles of the fits of stationary optical
spectra of PS II. Satisfactorily agreement between the experimental
and simulated spectra is obtained for the absorption spectrum including
its temperature dependence and the linear dichroism spectrum of PS
II core complexes (PS II-CC). Furthermore, the refined site energies
well reproduce the temperature dependence of the time-resolved fluorescence
spectrum of PS II-CC, which is characterized by the emergence of a
695 nm fluorescence peak upon cooling down to 77 K and the decrease
of its relative intensity upon further cooling below 77 K. The blue
shift of the fluorescence band upon cooling below 77 K is explained
by the existence of two red-shifted chlorophyll pools emitting at
around 685 and 695 nm. The former pool is assigned to Chl45 or Chl43
in CP43 (Chl numbering according to the nomenclature of Loll et al. Nature2005, 438, 1040) while
the latter is assigned to Chl29 in CP47. The 695 nm emitting chlorophyll
is suggested to attract excitations from the peripheral light-harvesting
complexes and might also be involved in photoprotection.
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Affiliation(s)
- Yutaka Shibata
- Division of Material Science (Physics), Graduate School of Science, Nagoya University, Nagoya, Japan.
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Renger T, Müh F. Understanding photosynthetic light-harvesting: a bottom up theoretical approach. Phys Chem Chem Phys 2013; 15:3348-71. [PMID: 23361062 DOI: 10.1039/c3cp43439g] [Citation(s) in RCA: 125] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We discuss a bottom up approach for modeling photosynthetic light-harvesting. Methods are reviewed for a full structure-based parameterization of the Hamiltonian of pigment-protein complexes (PPCs). These parameters comprise (i) the local transition energies of the pigments in their binding sites in the protein, the site energies; (ii) the couplings between optical transitions of the pigments, the excitonic couplings; and (iii) the spectral density characterizing the dynamic modulation of pigment transition energies and excitonic couplings by protein vibrations. Starting with quantum mechanics perturbation theory, we provide a microscopic foundation for the standard PPC Hamiltonian and relate the expressions obtained for its matrix elements to quantities that can be calculated with classical molecular mechanics/electrostatics approaches including the whole PPC in atomic detail and using charge and transition densities obtained with quantum chemical calculations on the isolated building blocks of the PPC. In the second part of this perspective, the Hamiltonian is utilized to describe the quantum dynamics of excitons. Situations are discussed that differ in the relative strength of excitonic and exciton-vibrational coupling. The predictive power of the approaches is demonstrated in application to different PPCs, and challenges for future work are outlined.
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Affiliation(s)
- Thomas Renger
- Institut für Theoretische Physik, Johannes Kepler Universität Linz, Linz, Austria.
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Renger T, Klinger A, Steinecker F, Schmidt am Busch M, Numata J, Müh F. Normal mode analysis of the spectral density of the Fenna-Matthews-Olson light-harvesting protein: how the protein dissipates the excess energy of excitons. J Phys Chem B 2012; 116:14565-80. [PMID: 23163520 PMCID: PMC3557933 DOI: 10.1021/jp3094935] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 11/19/2012] [Indexed: 11/29/2022]
Abstract
We report a method for the structure-based calculation of the spectral density of the pigment-protein coupling in light-harvesting complexes that combines normal-mode analysis with the charge density coupling (CDC) and transition charge from electrostatic potential (TrEsp) methods for the computation of site energies and excitonic couplings, respectively. The method is applied to the Fenna-Matthews-Olson (FMO) protein in order to investigate the influence of the different parts of the spectral density as well as correlations among these contributions on the energy transfer dynamics and on the temperature-dependent decay of coherences. The fluctuations and correlations in excitonic couplings as well as the correlations between coupling and site energy fluctuations are found to be 1 order of magnitude smaller in amplitude than the site energy fluctuations. Despite considerable amplitudes of that part of the spectral density which contains correlations in site energy fluctuations, the effect of these correlations on the exciton population dynamics and dephasing of coherences is negligible. The inhomogeneous charge distribution of the protein, which causes variations in local pigment-protein coupling constants of the normal modes, is responsible for this effect. It is seen thereby that the same building principle that is used by nature to create an excitation energy funnel in the FMO protein also allows for efficient dissipation of the excitons' excess energy.
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Affiliation(s)
- Thomas Renger
- Institut für Theoretische Physik, Johannes Kepler Universität Linz, Altenberger Str. 69, 4040 Linz, Austria.
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Hoyer S, Ishizaki A, Whaley KB. Spatial propagation of excitonic coherence enables ratcheted energy transfer. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:041911. [PMID: 23214619 DOI: 10.1103/physreve.86.041911] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2012] [Indexed: 06/01/2023]
Abstract
Experimental evidence shows that a variety of photosynthetic systems can preserve quantum beats in the process of electronic energy transfer, even at room temperature. However, whether this quantum coherence arises in vivo and whether it has any biological function have remained unclear. Here we present a theoretical model that suggests that the creation and recreation of coherence under natural conditions is ubiquitous. Our model allows us to theoretically demonstrate a mechanism for a ratchet effect enabled by quantum coherence, in a design inspired by an energy transfer pathway in the Fenna-Matthews-Olson complex of the green sulfur bacteria. This suggests a possible biological role for coherent oscillations in spatially directing energy transfer. Our results emphasize the importance of analyzing long-range energy transfer in terms of transfer between intercomplex coupling states rather than between site or exciton states.
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Affiliation(s)
- Stephan Hoyer
- Department of Physics, University of California, Berkeley, California 94720, USA
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