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Cupellini L, Caprasecca S, Guido CA, Müh F, Renger T, Mennucci B. Coupling to Charge Transfer States is the Key to Modulate the Optical Bands for Efficient Light Harvesting in Purple Bacteria. J Phys Chem Lett 2018; 9:6892-6899. [PMID: 30449098 DOI: 10.1021/acs.jpclett.8b03233] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The photosynthetic apparatus of purple bacteria uses exciton delocalization and static disorder to modulate the position and broadening of its absorption bands, leading to efficient light harvesting. Its main antenna complex, LH2, contains two rings of identical bacteriochlorophyll pigments, B800 and B850, absorbing at 800 and 850 nm, respectively. It has been an unsolved problem why static disorder of the strongly coupled B850 ring is several times larger than that of the B800 ring. Here we show that mixing between excitons and charge transfer states in the B850 ring is responsible for the effect. The linear absorption spectrum of the LH2 system is simulated by using a multiscale approach with an exciton Hamiltonian generalized to include the charge transfer states that involve adjacent pigment pairs, with static disorder modeled microscopically by molecular dynamics simulations. Our results show that sufficient inhomogeneous broadening of the B850 band, needed for efficient light harvesting, is only obtained by utilizing static disorder in the coupling between local excited and interpigment charge transfer states.
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Affiliation(s)
- Lorenzo Cupellini
- Dipartimento di Chimica e Chimica Industriale , University of Pisa , via G. Moruzzi 13 , 56124 Pisa , Italy
| | - Stefano Caprasecca
- Dipartimento di Chimica e Chimica Industriale , University of Pisa , via G. Moruzzi 13 , 56124 Pisa , Italy
| | - Ciro A Guido
- Dipartimento di Chimica e Chimica Industriale , University of Pisa , via G. Moruzzi 13 , 56124 Pisa , Italy
| | - Frank Müh
- Institute of Theoretical Physics, Department of Theoretical Biophysics , Johannes Kepler University Linz , Altenberger Strasse 69 , 4040 Linz , Austria
| | - Thomas Renger
- Institute of Theoretical Physics, Department of Theoretical Biophysics , Johannes Kepler University Linz , Altenberger Strasse 69 , 4040 Linz , Austria
| | - Benedetta Mennucci
- Dipartimento di Chimica e Chimica Industriale , University of Pisa , via G. Moruzzi 13 , 56124 Pisa , Italy
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Caycedo-Soler F, Lim J, Oviedo-Casado S, van Hulst NF, Huelga SF, Plenio MB. Theory of Excitonic Delocalization for Robust Vibronic Dynamics in LH2. J Phys Chem Lett 2018; 9:3446-3453. [PMID: 29863872 DOI: 10.1021/acs.jpclett.8b00933] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Nonlinear spectroscopy has revealed long-lasting oscillations in the optical response of a variety of photosynthetic complexes. Different theoretical models that involve the coherent coupling of electronic (excitonic) or electronic-vibrational (vibronic) degrees of freedom have been put forward to explain these observations. The ensuing debate concerning the relevance of either mechanism may have obscured their complementarity. To illustrate this balance, we quantify how the excitonic delocalization in the LH2 unit of Rhodopseudomonas acidophila purple bacterium leads to correlations of excitonic energy fluctuations, relevant coherent vibronic coupling, and importantly, a decrease in the excitonic dephasing rates. Combining these effects, we identify a feasible origin for the long-lasting oscillations observed in fluorescent traces from time-delayed two-pulse single-molecule experiments performed on this photosynthetic complex and use this approach to discuss the role of this complementarity in other photosynthetic systems.
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Affiliation(s)
- Felipe Caycedo-Soler
- Institute of Theoretical Physics and Integrated Quantum Science and Technology IQST , University of Ulm , Albert-Einstein-Allee 11 , D-89069 Ulm , Germany
| | - James Lim
- Institute of Theoretical Physics and Integrated Quantum Science and Technology IQST , University of Ulm , Albert-Einstein-Allee 11 , D-89069 Ulm , Germany
| | - Santiago Oviedo-Casado
- Departmento de Física Aplicada , Universidad Politécnica de Cartagena , 30202 Cartagena , Spain
| | - Niek F van Hulst
- ICFO - Institut de Ciencies Fotoniques , The Barcelona Institute of Science and Technology , 08860 Castelldefels, Barcelona , Spain
- ICREA - Institució Catalana de Recerca i Estudis Avançats , 08010 Barcelona , Spain
| | - Susana F Huelga
- Institute of Theoretical Physics and Integrated Quantum Science and Technology IQST , University of Ulm , Albert-Einstein-Allee 11 , D-89069 Ulm , Germany
| | - Martin B Plenio
- Institute of Theoretical Physics and Integrated Quantum Science and Technology IQST , University of Ulm , Albert-Einstein-Allee 11 , D-89069 Ulm , Germany
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Yu LJ, Kawakami T, Kimura Y, Wang-Otomo ZY. Structural Basis for the Unusual Q y Red-Shift and Enhanced Thermostability of the LH1 Complex from Thermochromatium tepidum. Biochemistry 2016; 55:6495-6504. [PMID: 27933779 DOI: 10.1021/acs.biochem.6b00742] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
While the majority of the core light-harvesting complexes (LH1) in purple photosynthetic bacteria exhibit a Qy absorption band in the range of 870-890 nm, LH1 from the thermophilic bacterium Thermochromatium tepidum displays the Qy band at 915 nm with an enhanced thermostability. These properties are regulated by Ca2+ ions. Substitution of the Ca2+ with other divalent metal ions results in a complex with the Qy band blue-shifted to 880-890 nm and a reduced thermostability. Following the recent publication of the structure of the Ca-bound LH1-reaction center (RC) complex [Niwa, S., et al. (2014) Nature 508, 228], we have determined the crystal structures of the Sr- and Ba-substituted LH1-RC complexes with the LH1 Qy band at 888 nm. Sixteen Sr2+ and Ba2+ ions are identified in the LH1 complexes. Both Sr2+ and Ba2+ are located at the same positions, and these are clearly different from, though close to, the Ca2+-binding sites. Conformational rearrangement induced by the substitution is limited to the metal-binding sites. Unlike the Ca-LH1-RC complex, only the α-polypeptides are involved in the Sr and Ba coordinations in LH1. The difference in the thermostability between these complexes can be attributed to the different patterns of the network formed by metal binding. The Sr- and Ba-LH1-RC complexes form a single-ring network by the LH1 α-polypeptides only, in contrast to the double-ring network composed of both α- and β-polypeptides in the Ca-LH1-RC complex. On the basis of the structural information, a combined effect of hydrogen bonding, structural integrity, and charge distribution is considered to influence the spectral properties of the core antenna complex.
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Affiliation(s)
- Long-Jiang Yu
- Faculty of Science, Ibaraki University , Mito 310-8512, Japan
| | | | - Yukihiro Kimura
- Department of Agrobioscience, Graduate School of Agriculture, Kobe University , Nada, Kobe 657-8501, Japan
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Meldaikis J, Zerlauskiene O, Abramavicius D, Valkunas L. Manifestation of protein conformations in the B850 absorption band of light-harvesting complex LH2. Chem Phys 2013. [DOI: 10.1016/j.chemphys.2013.06.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Chmeliov J, Songaila E, Rancova O, Gall A, Robert B, Abramavicius D, Valkunas L. Excitons in the LH3 complexes from purple bacteria. J Phys Chem B 2013; 117:11058-68. [PMID: 23570515 DOI: 10.1021/jp400239z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The noncovalently bound and structurally identical bacteriochlorophyll a chromophores in the peripheral light-harvesting complexes LH2 (B800-850) and LH3 (B800-820) from photosynthetic purple bacteria ensure the variability of the exciton spectra in the near-infrared (820-850 nm) wavelength region. As a result, the spectroscopic properties of the antenna complexes, such as positions of the maxima in the exciton absorption spectra, give rise to very efficient excitation transfer toward the reaction center. In this work, we investigated the possible molecular origin of the excitonically coupled B820 bacteriochlorophylls in LH3 using femtosecond transient absorption spectroscopy, deconvolution of steady-state absorption spectra, and modeling of the electrostatic intermolecular interactions using a charge density coupling approach. Compared to LH2, the upper excitonic level is red-shifted from 755 to 790 nm and is associated with an approximate 2-fold decrease of B820 intrapigment coupling. The absorption properties of LH3 cannot be reproduced by only changing the B850 site energy but also require a different scaling factor to be used to calculate interpigment couplings and a change of histidine protonation state. Several protonation patterns for distinct amino acid groups are presented, giving values of 162-173 cm(-1) at 100 K for the intradimer resonance interaction in the B820 ring.
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Affiliation(s)
- Jevgenij Chmeliov
- Institute of Physics, Center for Physical Sciences and Technology , Gostauto 11, LT-01108 Vilnius, Lithuania
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Goliney I, Sugakov V, Valkunas L, Vertsimakha G. Effect of metal nanoparticles on energy spectra and optical properties of peripheral light-harvesting LH2 complexes from photosynthetic bacteria. Chem Phys 2012. [DOI: 10.1016/j.chemphys.2012.03.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Trinkunas G, Zerlauskiene O, Urbonienė V, Chmeliov J, Gall A, Robert B, Valkunas L. Exciton Band Structure in Bacterial Peripheral Light-Harvesting Complexes. J Phys Chem B 2012; 116:5192-8. [DOI: 10.1021/jp302042w] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gediminas Trinkunas
- Institute of Physics, Center for Physical Sciences and Technology, Savanoriu
Avenue 231, LT-02300 Vilnius, Lithuania
- Department of Theoretical Physics,
Faculty of Physics, Vilnius University,
Sauletekio Avenue 9, LT-10222 Vilnius, Lithuania
| | - Oksana Zerlauskiene
- Institute of Physics, Center for Physical Sciences and Technology, Savanoriu
Avenue 231, LT-02300 Vilnius, Lithuania
| | - Vidita Urbonienė
- Department of General Physics
and Spectroscopy, Faculty of Physics, Vilnius University, Sauletekio Avenue 9, LT-10222 Vilnius, Lithuania
| | - Jevgenij Chmeliov
- Institute of Physics, Center for Physical Sciences and Technology, Savanoriu
Avenue 231, LT-02300 Vilnius, Lithuania
- Department of Theoretical Physics,
Faculty of Physics, Vilnius University,
Sauletekio Avenue 9, LT-10222 Vilnius, Lithuania
| | - Andrew Gall
- Institute of Biology and Technology of Saclay, CNRS-URA2096, CEA-Saclay,
91911 Gif sur Yvette, France
| | - Bruno Robert
- Institute of Biology and Technology of Saclay, CNRS-URA2096, CEA-Saclay,
91911 Gif sur Yvette, France
| | - Leonas Valkunas
- Institute of Physics, Center for Physical Sciences and Technology, Savanoriu
Avenue 231, LT-02300 Vilnius, Lithuania
- Department of Theoretical Physics,
Faculty of Physics, Vilnius University,
Sauletekio Avenue 9, LT-10222 Vilnius, Lithuania
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Spectral dependence of energy transfer in wild-type peripheral light-harvesting complexes of photosynthetic bacteria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:1465-9. [DOI: 10.1016/j.bbabio.2010.05.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Revised: 04/28/2010] [Accepted: 05/05/2010] [Indexed: 11/20/2022]
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Freiberg A, Trinkunas G. Unraveling the Hidden Nature of Antenna Excitations. PHOTOSYNTHESIS IN SILICO 2009. [DOI: 10.1007/978-1-4020-9237-4_4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Zerlauskiene O, Trinkunas G, Gall A, Robert B, Urboniene V, Valkunas L. Static and Dynamic Protein Impact on Electronic Properties of Light-Harvesting Complex LH2. J Phys Chem B 2008; 112:15883-92. [DOI: 10.1021/jp803439w] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- O. Zerlauskiene
- Institute of Physics, Savanoriu 231, LT-02300 Vilnius, Lithuania, CEA, Institut de Biologie et Technologies de Saclay, and CNRS, 91191 Gif sur Yvette Cedex, France, Department of General Physics and Spectroscopy, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania, and Department of Theoretical Physics, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania
| | - G. Trinkunas
- Institute of Physics, Savanoriu 231, LT-02300 Vilnius, Lithuania, CEA, Institut de Biologie et Technologies de Saclay, and CNRS, 91191 Gif sur Yvette Cedex, France, Department of General Physics and Spectroscopy, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania, and Department of Theoretical Physics, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania
| | - A. Gall
- Institute of Physics, Savanoriu 231, LT-02300 Vilnius, Lithuania, CEA, Institut de Biologie et Technologies de Saclay, and CNRS, 91191 Gif sur Yvette Cedex, France, Department of General Physics and Spectroscopy, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania, and Department of Theoretical Physics, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania
| | - B. Robert
- Institute of Physics, Savanoriu 231, LT-02300 Vilnius, Lithuania, CEA, Institut de Biologie et Technologies de Saclay, and CNRS, 91191 Gif sur Yvette Cedex, France, Department of General Physics and Spectroscopy, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania, and Department of Theoretical Physics, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania
| | - V. Urboniene
- Institute of Physics, Savanoriu 231, LT-02300 Vilnius, Lithuania, CEA, Institut de Biologie et Technologies de Saclay, and CNRS, 91191 Gif sur Yvette Cedex, France, Department of General Physics and Spectroscopy, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania, and Department of Theoretical Physics, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania
| | - L. Valkunas
- Institute of Physics, Savanoriu 231, LT-02300 Vilnius, Lithuania, CEA, Institut de Biologie et Technologies de Saclay, and CNRS, 91191 Gif sur Yvette Cedex, France, Department of General Physics and Spectroscopy, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania, and Department of Theoretical Physics, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania
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Urboniene V, Vrublevskaja O, Trinkunas G, Gall A, Robert B, Valkunas L. Solvation effect of bacteriochlorophyll excitons in light-harvesting complex LH2. Biophys J 2007; 93:2188-98. [PMID: 17513366 PMCID: PMC1959563 DOI: 10.1529/biophysj.106.103093] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have characterized the influence of the protein environment on the spectral properties of the bacteriochlorophyll (Bchl) molecules of the peripheral light-harvesting (or LH2) complex from Rhodobacter sphaeroides. The spectral density functions of the pigments responsible for the 800 and 850 nm electronic transitions were determined from the temperature dependence of the Bchl absorption spectra in different environments (detergent micelles and native membranes). The spectral density function is virtually independent of the hydrophobic support that the protein experiences. The reorganization energy for the B850 Bchls is 220 cm(-1), which is almost twice that of the B800 Bchls, and its Huang-Rhys factor reaches 8.4. Around the transition point temperature, and at higher temperatures, both the static spectral inhomogeneity and the resonance interactions become temperature-dependent. The inhomogeneous distribution function of the transitions exhibits less temperature dependence when LH2 is embedded in membranes, suggesting that the lipid phase protects the protein. However, the temperature dependence of the fluorescence spectra of LH2 cannot be fitted using the same parameters determined from the analysis of the absorption spectra. Correct fitting requires the lowest exciton states to be additionally shifted to the red, suggesting the reorganization of the exciton spectrum.
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Affiliation(s)
- V Urboniene
- Department of General Physics and Spectroscopy, Vilnius University, Vilnius, Lithuania
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Jang S, Newton MD, Silbey RJ. Multichromophoric Förster Resonance Energy Transfer from B800 to B850 in the Light Harvesting Complex 2: Evidence for Subtle Energetic Optimization by Purple Bacteria. J Phys Chem B 2007; 111:6807-14. [PMID: 17439170 DOI: 10.1021/jp070111l] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This work provides a detailed account of the application of our multichromophoric Förster resonance energy transfer (MC-FRET) theory (Phys. Rev. Lett. 2004, 92, 218301) for the calculation of the energy transfer rate from the B800 unit to the B850 unit in the light harvesting complex 2 (LH2) of purple bacteria. The model Hamiltonian consists of the B800 unit represented by a single bacteriochlorophyll (BChl), the B850 unit represented by its entire set of BChls, the electronic coupling between the two units, and the bath terms representing all environmental degrees of freedom. The model parameters are determined, independent of the rate calculation, from the literature data and by a fitting to an ensemble line shape. Comparing our theoretical rate and a low-temperature experimental rate, we estimate the magnitude of the BChl-Qy transition dipole to be in the range of 6.5-7.5 D, assuming that the optical dielectric constant of the medium is in the range of 1.5-2. We examine how the bias of the average excitation energy of the B800-BChl relative to that of the B850-BChl affects the energy transfer time by calculating the transfer rates based on both our MC-FRET theory and the original FRET theory, varying the value of the bias. Within our model, we find that the value of bias 260 cm-1, which we determine from the fitting to an ensemble line shape, is very close to the value at which the ratio between MC-FRET and FRET rates is a maximum. This provides evidence that the bacterial system utilizes the quantum mechanical coherence among the multiple chromophores within the B850 in a constructive way so as to achieve efficient energy transfer from B800 to B850.
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Affiliation(s)
- Seogjoo Jang
- Department of Chemistry and Biochemistry, Queens College of the City University of New York, 65-30 Kissena Boulevard, Flushing, New York 11367-1597, USA.
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