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Saga Y, Hamanishi K. Effects of Detergents on the Spectral Features of B820 Bacteriochlorophyll a in Light-Harvesting Complex 3. ACS OMEGA 2022; 7:29231-29235. [PMID: 36033670 PMCID: PMC9404518 DOI: 10.1021/acsomega.2c03323] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Accepted: 08/03/2022] [Indexed: 06/15/2023]
Abstract
Excitonic coupling of bacteriochlorophyll (BChl) a in light-harvesting (LH) proteins of purple photosynthetic bacteria is key for efficient photon capture and energy transfer. Environmental factors can affect the spectral features of these BChl a pigments and investigating these effects can provide insight into the molecular mechanisms underlying the photosynthetic spectral tuning. The present study analyzes the spectral alterations of the Qy band of B820 BChl a within the LH3 protein in relation to the type and concentration of detergents in the buffer. Changing the detergent from lauryl dimethylamine N-oxide (LDAO) to n-dodecyl-β-d-maltoside (DDM) caused a red shift in the B820 Qy band accompanied by hyperchromism; these spectral alterations were completely reversed by exchanging back from DDM to LDAO. These results reflect the different effects of harsh vs mild detergents on the perturbation of LH3. The B820 Qy band did not change when LDAO or NaCl concentration was altered, suggesting that electrostatic effects by external components have little influence on the spectral features of B820 BChl a in LH3.
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2
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Timpmann K, Linnanto JM, Yadav D, Kangur L, Freiberg A. Hydrostatic High-Pressure-Induced Denaturation of LH2 Membrane Proteins. J Phys Chem B 2021; 125:9979-9989. [PMID: 34460261 DOI: 10.1021/acs.jpcb.1c05789] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The denaturation of globular proteins by high pressure is frequently associated with the release of internal voids and/or the exposure of the hydrophobic protein interior to a polar aqueous solvent. Similar evidence with respect to membrane proteins is not available. Here, we investigate the impact of hydrostatic pressures reaching 12 kbar on light-harvesting 2 integral membrane complexes of purple photosynthetic bacteria using two types of innate chromophores in separate strategic locations: bacteriochlorophyll-a in the hydrophobic interior and tryptophan at both protein-solvent interfacial gateways to internal voids. The complexes from mutant Rhodobacter sphaeroides with low resilience against pressure were considered in parallel with the naturally robust complexes of Thermochromatium tepidum. In the former case, a firm correlation was established between the abrupt blue shift of the bacteriochlorophyll-a exciton absorption, a known indicator of the breakage of tertiary structure pigment-protein hydrogen bonds, and the quenching of tryptophan fluorescence, a supposed result of further protein solvation. No such effects were observed in the reference complex. While these data may be naively taken as supporting evidence of the governing role of hydration, the analysis of atomistic model structures of the complexes confirmed the critical part of the structure in the pressure-induced denaturation of the membrane proteins studied.
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Affiliation(s)
- Kõu Timpmann
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu 50411, Estonia
| | - Juha Matti Linnanto
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu 50411, Estonia
| | - Dheerendra Yadav
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu 50411, Estonia
| | - Liina Kangur
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu 50411, Estonia
| | - Arvi Freiberg
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu 50411, Estonia.,Estonian Academy of Sciences, Kohtu Str. 6, Tallinn 10130, Estonia
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3
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Kangur L, Rätsep M, Timpmann K, Wang-Otomo ZY, Freiberg A. The two light-harvesting membrane chromoproteins of Thermochromatium tepidum expose distinct robustness against temperature and pressure. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1861:148205. [PMID: 32305413 DOI: 10.1016/j.bbabio.2020.148205] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 03/17/2020] [Accepted: 04/14/2020] [Indexed: 01/26/2023]
Abstract
An increased robustness against high temperature and the much red-shifted near-infrared absorption spectrum of excitons in the LH1-RC core pigment-protein complex from the thermophilic photosynthetic purple sulfur bacterium Thermochromatium tepidum has recently attracted much interest. In the present work, thermal and hydrostatic pressure stability of the peripheral LH2 and core LH1-RC complexes from this bacterium were in parallel investigated by various optical spectroscopy techniques applied over a wide spectral range from far-ultraviolet to near-infrared. In contrast to expectations, very distinct robustness of the complexes was established, while the sturdiness of LH2 surpassed that of LH1-RC both with respect to temperatures between 288 and 360 K, and pressures between 1 bar and 14 kbar. Subtle structural variances related to the hydrogen bond network are likely responsible for the extra stability of LH2.
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Affiliation(s)
- Liina Kangur
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, 50411 Tartu, Estonia
| | - Margus Rätsep
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, 50411 Tartu, Estonia
| | - Kõu Timpmann
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, 50411 Tartu, Estonia
| | | | - Arvi Freiberg
- Institute of Physics, University of Tartu, W. Ostwald Str. 1, 50411 Tartu, Estonia; Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia; Estonian Academy of Sciences, Kohtu 6, 10130 Tallinn, Estonia.
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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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6
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Structural stability of human butyrylcholinesterase under high hydrostatic pressure. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2018; 1867:107-113. [PMID: 30414450 DOI: 10.1016/j.bbapap.2018.11.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 11/02/2018] [Accepted: 11/05/2018] [Indexed: 11/23/2022]
Abstract
Human butyrylcholinesterase is a nonspecific enzyme of clinical, pharmacological and toxicological significance. Although the enzyme is relatively stable, its activity is affected by numerous factors, including pressure. In this work, hydrostatic pressure dependence of the intrinsic tryptophan fluorescence in native and salted human butyrylcholinesterase was studied up to the maximum pressure at ambient temperature of about 1200 MPa. A correlated large shift toward long wavelengths and broadening observed at pressures between 200 and 700 MPa was interpreted as due to high pressure-induced denaturation of the protein, leading to an enhanced exposure of tryptophan residues into polar solvent environment. This transient process in native butyrylcholinesterase presumably involves conformational changes of the enzyme at both tertiary and secondary structure levels. Pressure-induced mixing of emitting local indole electronic transitions with quenching charge transfer states likely describes the accompanying fluorescence quenching that reveals different course from spectral changes. All the pressure-induced changes turned irreversible after passing a mid-point pressure of about 400 ± 50 MPa. Addition of either 0.1 M ammonium sulphate (a kosmotropic salt) or 0.1 M lithium thiocyanate (a chaotropic salt) to native enzyme similarly destabilized its structure.
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7
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Macrocycle ring deformation as the secondary design principle for light-harvesting complexes. Proc Natl Acad Sci U S A 2018; 115:E9051-E9057. [PMID: 30194231 DOI: 10.1073/pnas.1719355115] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Natural light-harvesting is performed by pigment-protein complexes, which collect and funnel the solar energy at the start of photosynthesis. The identity and arrangement of pigments largely define the absorption spectrum of the antenna complex, which is further regulated by a palette of structural factors. Small alterations are induced by pigment-protein interactions. In light-harvesting systems 2 and 3 from Rhodoblastus acidophilus, the pigments are arranged identically, yet the former has an absorption peak at 850 nm that is blue-shifted to 820 nm in the latter. While the shift has previously been attributed to the removal of hydrogen bonds, which brings changes in the acetyl moiety of the bacteriochlorophyll, recent work has shown that other mechanisms are also present. Using computational and modeling tools on the corresponding crystal structures, we reach a different conclusion: The most critical factor for the shift is the curvature of the macrocycle ring. The bending of the planar part of the pigment is identified as the second-most important design principle for the function of pigment-protein complexes-a finding that can inspire the design of novel artificial systems.
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8
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Ogren JI, Tong AL, Gordon SC, Chenu A, Lu Y, Blankenship RE, Cao J, Schlau-Cohen GS. Impact of the lipid bilayer on energy transfer kinetics in the photosynthetic protein LH2. Chem Sci 2018; 9:3095-3104. [PMID: 29732092 PMCID: PMC5914429 DOI: 10.1039/c7sc04814a] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 02/05/2018] [Indexed: 01/28/2023] Open
Abstract
Photosynthetic purple bacteria convert solar energy to chemical energy with near unity quantum efficiency. The light-harvesting process begins with absorption of solar energy by an antenna protein called Light-Harvesting Complex 2 (LH2). Energy is subsequently transferred within LH2 and then through a network of additional light-harvesting proteins to a central location, termed the reaction center, where charge separation occurs. The energy transfer dynamics of LH2 are highly sensitive to intermolecular distances and relative organizations. As a result, minor structural perturbations can cause significant changes in these dynamics. Previous experiments have primarily been performed in two ways. One uses non-native samples where LH2 is solubilized in detergent, which can alter protein structure. The other uses complex membranes that contain multiple proteins within a large lipid area, which make it difficult to identify and distinguish perturbations caused by protein-protein interactions and lipid-protein interactions. Here, we introduce the use of the biochemical platform of model membrane discs to study the energy transfer dynamics of photosynthetic light-harvesting complexes in a near-native environment. We incorporate a single LH2 from Rhodobacter sphaeroides into membrane discs that provide a spectroscopically amenable sample in an environment more physiological than detergent but less complex than traditional membranes. This provides a simplified system to understand an individual protein and how the lipid-protein interaction affects energy transfer dynamics. We compare the energy transfer rates of detergent-solubilized LH2 with those of LH2 in membrane discs using transient absorption spectroscopy and transient absorption anisotropy. For one key energy transfer step in LH2, we observe a 30% enhancement of the rate for LH2 in membrane discs compared to that in detergent. Based on experimental results and theoretical modeling, we attribute this difference to tilting of the peripheral bacteriochlorophyll in the B800 band. These results highlight the importance of well-defined systems with near-native membrane conditions for physiologically-relevant measurements.
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Affiliation(s)
- John I Ogren
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , MA 02139 , USA .
| | - Ashley L Tong
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , MA 02139 , USA .
| | - Samuel C Gordon
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , MA 02139 , USA .
| | - Aurélia Chenu
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , MA 02139 , USA .
| | - Yue Lu
- Department of Biology and Chemistry , Washington University in St. Louis , St. Louis , MO 63130 , USA
| | - Robert E Blankenship
- Department of Biology and Chemistry , Washington University in St. Louis , St. Louis , MO 63130 , USA
| | - Jianshu Cao
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , MA 02139 , USA .
| | - Gabriela S Schlau-Cohen
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , MA 02139 , USA .
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9
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Saga Y, Hirota K, Asakawa H, Takao K, Fukuma T. Reversible Changes in the Structural Features of Photosynthetic Light-Harvesting Complex 2 by Removal and Reconstitution of B800 Bacteriochlorophyll a Pigments. Biochemistry 2017; 56:3484-3491. [DOI: 10.1021/acs.biochem.7b00267] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Yoshitaka Saga
- Department
of Chemistry, Faculty of Science and Engineering, Kindai University, Higashi-Osaka, Osaka 577-8502, Japan
- Precursory
Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan
| | - Keiya Hirota
- Department
of Chemistry, Faculty of Science and Engineering, Kindai University, Higashi-Osaka, Osaka 577-8502, Japan
| | - Hitoshi Asakawa
- Precursory
Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan
- Graduate
School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan
- Bio-AFM
Frontier Research Center, Kanazawa University, Kanazawa 920-1192, Japan
| | - Kazufumi Takao
- Graduate
School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan
| | - Takeshi Fukuma
- Graduate
School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan
- Bio-AFM
Frontier Research Center, Kanazawa University, Kanazawa 920-1192, Japan
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10
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Kell A, Jassas M, Acharya K, Hacking K, Cogdell RJ, Jankowiak R. Conformational Complexity in the LH2 Antenna of the Purple Sulfur Bacterium Allochromatium vinosum Revealed by Hole-Burning Spectroscopy. J Phys Chem A 2017; 121:4435-4446. [PMID: 28531352 DOI: 10.1021/acs.jpca.7b03188] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This work discusses the protein conformational complexity of the B800-850 LH2 complexes from the purple sulfur bacterium Allochromatium vinosum, focusing on the spectral characteristics of the B850 chromophores. Low-temperature B850 absorption and the split B800 band shift blue and red, respectively, at elevated temperatures, revealing isosbestic points. The latter indicates the presence of two (unresolved) conformations of B850 bacteriochlorophylls (BChls), referred to as conformations 1 and 2, and two conformations of B800 BChls, denoted as B800R and B800B. The energy differences between average site energies of conformations 1 and 2, and B800R and B800B are similar (∼200 cm-1), suggesting weak and strong hydrogen bonds linking two major subpopulations of BChls and the protein scaffolding. Although conformations 1 and 2 of the B850 chromophores, and B800R and B800B, exist in the ground state, selective excitation leads to 1 → 2 and B800R → B800B phototransformations. Different static inhomogeneous broadening is revealed for the lowest energy exciton states of B850 (fwhm ∼195 cm-1) and B800R (fwhm ∼140 cm-1). To describe the 5 K absorption spectrum and the above-mentioned conformations, we employ an exciton model with dichotomous protein conformation disorder. We show that both experimental data and the modeling study support a two-site model with strongly and weakly hydrogen-bonded B850 and B800 BChls, which under illumination undergo conformational changes, most likely caused by proton dynamics.
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Affiliation(s)
| | | | | | - Kirsty Hacking
- Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow G12 8TA, Scotland
| | - Richard J Cogdell
- Institute of Molecular Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow G12 8TA, Scotland
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11
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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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12
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Leiger K, Freiberg A. Up-converted fluorescence from photosynthetic light-harvesting complexes linearly dependent on excitation intensity. PHOTOSYNTHESIS RESEARCH 2016; 127:77-87. [PMID: 25764015 DOI: 10.1007/s11120-015-0117-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2014] [Accepted: 03/05/2015] [Indexed: 06/04/2023]
Abstract
Weak up-converted fluorescence related to bacteriochlorophyll a was recorded from various detergent-isolated and membrane-embedded light-harvesting pigment-protein complexes as well as from the functional membranes of photosynthetic purple bacteria under continuous-wave infrared laser excitation at 1064 nm, far outside the optically allowed singlet absorption bands of the chromophore. The fluorescence increases linearly with the excitation power, distinguishing it from the previously observed two-photon excited fluorescence upon femtosecond pulse excitation. Possible mechanisms of this excitation are discussed.
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Affiliation(s)
- Kristjan Leiger
- Institute of Physics, University of Tartu, Ravila 14c, 51011, Tartu, Estonia.
| | - Arvi Freiberg
- Institute of Physics, University of Tartu, Ravila 14c, 51011, Tartu, Estonia.
- Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51014, Tartu, Estonia.
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13
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Shibuya Y, Itoh T, Matsuura SI, Yamaguchi A. Structural Stability of Light-harvesting Protein LH2 Adsorbed on Mesoporous Silica Supports. ANAL SCI 2015; 31:1069-74. [PMID: 26460373 DOI: 10.2116/analsci.31.1069] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
In the present study, we examined the reversible thermal deformation of the membrane protein light-harvesting complex LH2 adsorbed on mesoporous silica (MPS) supports. The LH2 complex from Thermochromatium tepidum cells was conjugated to MPS supports with a series of pore diameter (2.4 to 10.6 nm), and absorption spectra of the resulting LH2/MPS conjugates were observed over a temperature range of 273 - 313 K in order to examine the structure of the LH2 adsorbed on the MPS support. The experimental results confirmed that a slight ellipsoidal deformation of LH2 was induced by adsorption on the MPS supports. On the other hand, the structural stability of LH2 was not perturbed by the adsorption. Since the pore diameter of MPS support did not influence the structural stability of LH2, it could be considered that the spatial confinement of LH2 in size-matches pore did not improve the structural stability of LH2.
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14
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Rätsep M, Pajusalu M, Linnanto JM, Freiberg A. Subtle spectral effects accompanying the assembly of bacteriochlorophylls into cyclic light harvesting complexes revealed by high-resolution fluorescence spectroscopy. J Chem Phys 2015; 141:155102. [PMID: 25338912 DOI: 10.1063/1.4897637] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have observed that an assembly of the bacteriochloropyll a molecules into B850 and B875 groups of cyclic bacterial light-harvesting complexes LH2 and LH1, respectively, results an almost total loss of the intra-molecular vibronic structure in the fluorescence spectrum, and simultaneously, an essential enhancement of its phonon sideband due to electron-phonon coupling. While the suppression of the vibronic coupling in delocalized (excitonic) molecular systems is predictable, as also confirmed by our model calculations, a boost of the electron-phonon coupling is rather unexpected. The latter phenomenon is explained by exciton self-trapping, promoted by mixing the molecular exciton states with charge transfer states between the adjacent chromophores in the tightly packed B850 and B875 arrangements. Similar, although less dramatic trends were noted for the light-harvesting complexes containing chlorophyll pigments.
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Affiliation(s)
- Margus Rätsep
- Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia
| | - Mihkel Pajusalu
- Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia
| | | | - Arvi Freiberg
- Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia and Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia
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15
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Pajusalu M, Kunz R, Rätsep M, Timpmann K, Köhler J, Freiberg A. Unified analysis of ensemble and single-complex optical spectral data from light-harvesting complex-2 chromoproteins for gaining deeper insight into bacterial photosynthesis. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:052709. [PMID: 26651725 DOI: 10.1103/physreve.92.052709] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Indexed: 05/15/2023]
Abstract
Bacterial light-harvesting pigment-protein complexes are very efficient at converting photons into excitons and transferring them to reaction centers, where the energy is stored in a chemical form. Optical properties of the complexes are known to change significantly in time and also vary from one complex to another; therefore, a detailed understanding of the variations on the level of single complexes and how they accumulate into effects that can be seen on the macroscopic scale is required. While experimental and theoretical methods exist to study the spectral properties of light-harvesting complexes on both individual complex and bulk ensemble levels, they have been developed largely independently of each other. To fill this gap, we simultaneously analyze experimental low-temperature single-complex and bulk ensemble optical spectra of the light-harvesting complex-2 (LH2) chromoproteins from the photosynthetic bacterium Rhodopseudomonas acidophila in order to find a unique theoretical model consistent with both experimental situations. The model, which satisfies most of the observations, combines strong exciton-phonon coupling with significant disorder, characteristic of the proteins. We establish a detailed disorder model that, in addition to containing a C_{2}-symmetrical modulation of the site energies, distinguishes between static intercomplex and slow conformational intracomplex disorders. The model evaluations also verify that, despite best efforts, the single-LH2-complex measurements performed so far may be biased toward complexes with higher Huang-Rhys factors.
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Affiliation(s)
- Mihkel Pajusalu
- Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia
| | - Ralf Kunz
- Experimental Physics IV and Bayreuth Institute for Macromolecular Research, University of Bayreuth, 95440 Bayreuth, Germany
| | - Margus Rätsep
- Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia
| | - Kõu Timpmann
- Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia
| | - Jürgen Köhler
- Experimental Physics IV and Bayreuth Institute for Macromolecular Research, University of Bayreuth, 95440 Bayreuth, Germany
| | - Arvi Freiberg
- Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia
- Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia
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16
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Rancova O, Abramavicius D. Static and Dynamic Disorder in Bacterial Light-Harvesting Complex LH2: A 2DES Simulation Study. J Phys Chem B 2014; 118:7533-7540. [DOI: 10.1021/jp5043156] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Olga Rancova
- Department of Theoretical
Physics, Faculty of Physics, Vilnius University, Sauletekio av. 9 III bld., LT-10222 Vilnius, Lithuania
| | - Darius Abramavicius
- Department of Theoretical
Physics, Faculty of Physics, Vilnius University, Sauletekio av. 9 III bld., LT-10222 Vilnius, Lithuania
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17
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Böhm PS, Kunz R, Southall J, Cogdell RJ, Köhler J. Does the Reconstitution of RC-LH1 Complexes from Rhodopseudomonas acidophila Strain 10050 into a Phospholipid Bilayer Yield the Optimum Environment for Optical Spectroscopy? J Phys Chem B 2013; 117:15004-13. [DOI: 10.1021/jp409980k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Paul S. Böhm
- Experimental
Physics IV and Bayreuth Institute for Macromolecular Research (BIMF), University of Bayreuth, 95440 Bayreuth, Germany
| | - Ralf Kunz
- Experimental
Physics IV and Bayreuth Institute for Macromolecular Research (BIMF), University of Bayreuth, 95440 Bayreuth, Germany
| | - June Southall
- Institute of Molecular, Cell and Systems Biology, College
of Medical Veterinary and Life Sciences, Biomedical Research Building, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
| | - Richard J. Cogdell
- Institute of Molecular, Cell and Systems Biology, College
of Medical Veterinary and Life Sciences, Biomedical Research Building, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
| | - Jürgen Köhler
- Experimental
Physics IV and Bayreuth Institute for Macromolecular Research (BIMF), University of Bayreuth, 95440 Bayreuth, Germany
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18
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Kunz R, Timpmann K, Southall J, Cogdell RJ, Köhler J, Freiberg A. Fluorescence-Excitation and Emission Spectra from LH2 Antenna Complexes of Rhodopseudomonas acidophila as a Function of the Sample Preparation Conditions. J Phys Chem B 2013; 117:12020-9. [DOI: 10.1021/jp4073697] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Ralf Kunz
- Experimental Physics
IV and Bayreuth Institute for Macromolecular Research (BIMF), University of Bayreuth, 95440 Bayreuth, Germany
| | - Kõu Timpmann
- Institute
of Physics, University of Tartu, Riia 142, Tartu EE-51014, Estonia
| | - June Southall
- Institute of Molecular,
Cell and Systems Biology, College of Medical, Veterinary and Life
Sciences, University of Glasgow, Glasgow G12 8TA, United Kingdom
| | - Richard J. Cogdell
- Institute of Molecular,
Cell and Systems Biology, College of Medical, Veterinary and Life
Sciences, University of Glasgow, Glasgow G12 8TA, United Kingdom
| | - Jürgen Köhler
- Experimental Physics
IV and Bayreuth Institute for Macromolecular Research (BIMF), University of Bayreuth, 95440 Bayreuth, Germany
| | - Arvi Freiberg
- Institute
of Physics, University of Tartu, Riia 142, Tartu EE-51014, Estonia
- Institute of Molecular
and Cell Biology, University of Tartu, Riia 23, Tartu EE-51010, Estonia
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19
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Rajapaksha SP, He Y, Lu HP. Combined topographic, spectroscopic, and model analyses of inhomogeneous energetic coupling of linear light harvesting complex II aggregates in native photosynthetic membranes. Phys Chem Chem Phys 2013; 15:5636-47. [PMID: 23474628 DOI: 10.1039/c3cp43582b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Light harvesting by LH1 and LH2 antenna proteins in the photosynthetic membranes of purple bacteria has been extensively studied in recent years for the fundamental understanding of the energy transfer dynamics and mechanism. Here we report the inhomogeneous structural organization of the LH2 complexes in photosynthetic membranes, giving evidence for the existence of energetically coupled linear LH2 aggregates in the native photosynthetic membranes of purple bacteria. Focusing on systematic model analyses, we combined AFM imaging and spectroscopic analysis with energetic coupling model analysis to characterize the inhomogeneous linear aggregation of LH2. Our AFM imaging results reveal that the LH2 complexes form linear aggregates with the monomer number varying from one to eight and each monomer tilted along the aggregated structure in photosynthetic membranes. The spectroscopic results support the attribution of aggregated LH2 complexes in the photosynthetic membranes, and the model calculation values for the absorption, emission and lifetime are consistent with the experimentally determined spectroscopic values, further proving a molecular-level understanding of the energetic coupling and energy transfer among the LH2 complexes in the photosynthetic membranes.
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Affiliation(s)
- Suneth P Rajapaksha
- Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403, USA
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20
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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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21
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Structural implications of hydrogen-bond energetics in membrane proteins revealed by high-pressure spectroscopy. Biophys J 2013; 103:2352-60. [PMID: 23283234 DOI: 10.1016/j.bpj.2012.10.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 10/09/2012] [Accepted: 10/23/2012] [Indexed: 11/23/2022] Open
Abstract
The light-harvesting 1 (LH1) integral membrane complex of Rhodobacter sphaeroides provides a convenient model system in which to examine the poorly understood role of hydrogen bonds (H-bonds) as stabilizing factors in membrane protein complexes. We used noncovalently bound arrays of bacteriochlorophyll chromophores within native and genetically modified variants of LH1 complexes to monitor local changes in the chromophore binding sites induced by externally applied hydrostatic pressure. Whereas membrane-bound complexes demonstrated very high resilience to pressures reaching 2.1 GPa, characteristic discontinuous shifts and broadenings of the absorption spectra were observed around 1 GPa for detergent-solubilized proteins, in similarity to those observed when specific (α or β) H-bonds between the chromophores and the surrounding protein were selectively removed by mutagenesis. These pressure effects, which were reversible upon decompression, allowed us to estimate the rupture energies of H-bonds to the chromophores in LH1 complexes. A quasi-independent, additive role of H-bonds in the α- and β-sublattices in reinforcing the wild-type LH1 complex was established. A comparison of a reaction-center-deficient LH1 complex with complexes containing reaction centers also demonstrated a stabilizing effect of the reaction center. This study thus provides important insights into the design principles of natural photosynthetic complexes.
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22
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Renge I, Mauring K. Spectral shift mechanisms of chlorophylls in liquids and proteins. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2013; 102:301-313. [PMID: 23220672 DOI: 10.1016/j.saa.2012.10.034] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 10/18/2012] [Accepted: 10/19/2012] [Indexed: 05/27/2023]
Abstract
Origins of non-excitonic spectral shifts of chlorophylls that can reach -1,000 cm(-1) in pigment-protein complexes are actively debated in literature. We investigate possible shift mechanisms, basing on absorption and fluorescence measurements in large number of liquids. Transition wavelength in solvent-free state was estimated (±2 nm) for chlorophyll a (Chl a, 647 nm), Chl b (624 nm), bacteriochlorophyll a (BChl a, 752 nm), and pheophytines. The dispersive-repulsive shift is a predominating mechanism. It depends on polarizability difference between the ground and the excited state Δα and the Lorenz-Lorentz function of refractive index of solvent (n). The approximate (± 2Å(3)) increase of polarizability Δα is close to 15Å(3) for S(1) bands of Chl a, BChl a, and BPheo a, slightly larger for Chl b (18Å(3)), and less for Pheo a (11Å(3)). The effect of solvent polarity, expressed in terms of static dielectric permittivity (ε) is relatively minor, but characteristic for different pigments and transitions. Remarkably, maximum influence of ε on S(1) band of BChl a is less (-20 ± 10 cm(-1)) than that for Chl a (-50 ± 10 cm(-1)), and not correlated with dipole moment changes on excitation Δμ (∼2D and 0.1 ± 0.1D, respectively). Hydrogen bonding in protic solvents produces red shifts in Chl a (-60 cm(-1)) and BChl a (-100 cm(-1)), but not in Chl b. Second axial ligand of BChl a has no influence on the S(1) band, whereas the S(2) transition suffers a -400 to -600 cm(-1) down shift. Aromatic character of solvent is responsible for a ∼-100 cm(-1) red shift of both Q transitions in BChl a. The S(1) bands in chlorophylls are relatively insensitive with respect to dielectric properties and specific solvation. Therefore, nontrivial mechanisms, yielding large site-energy shifts are expected in photosynthetic chlorophyll-proteins.
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Affiliation(s)
- Indrek Renge
- Institute of Physics, University of Tartu, 142 Riia Street, EE51014 Tartu, Estonia.
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23
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Liu WL, Zheng ZR, Zhang JP, Wu WZ, Li AH, Zhang W, Huo MM, Liu ZG, Zhu RB, Zhao LC, Su WH. White-light continuum probed femtosecond time-resolved absorption spectroscopic measurement of β-carotene under high pressure. Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2012.02.053] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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24
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Tubasum S, Cogdell RJ, Scheblykin IG, Pullerits T. Excitation−Emission Polarization Spectroscopy of Single Light Harvesting Complexes. J Phys Chem B 2011; 115:4963-70. [DOI: 10.1021/jp107480x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sumera Tubasum
- Department of Chemical Physics, Lund University, P.O. Box 124, SE-22 100, Lund, Sweden
| | - Richard J. Cogdell
- Glasgow Biomedical Research Centre, University of Glasgow, G12 8QQ, United Kingdom
| | - Ivan G. Scheblykin
- Department of Chemical Physics, Lund University, P.O. Box 124, SE-22 100, Lund, Sweden
| | - Tõnu Pullerits
- Department of Chemical Physics, Lund University, P.O. Box 124, SE-22 100, Lund, Sweden
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25
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Neugebauer J, Curutchet C, Muñoz-Losa A, Mennucci B. A Subsystem TDDFT Approach for Solvent Screening Effects on Excitation Energy Transfer Couplings. J Chem Theory Comput 2010; 6:1843-51. [DOI: 10.1021/ct100138k] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Johannes Neugebauer
- Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Department of Chemistry, 80 St. George Street, Institute for Optical Sciences and Centre for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario M5S 3H6 Canada, Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi 17071 Girona, Catalonia, Spain, and Dipartimento di Chimica e Chimica Industriale, Università di
| | - Carles Curutchet
- Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Department of Chemistry, 80 St. George Street, Institute for Optical Sciences and Centre for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario M5S 3H6 Canada, Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi 17071 Girona, Catalonia, Spain, and Dipartimento di Chimica e Chimica Industriale, Università di
| | - Aurora Muñoz-Losa
- Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Department of Chemistry, 80 St. George Street, Institute for Optical Sciences and Centre for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario M5S 3H6 Canada, Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi 17071 Girona, Catalonia, Spain, and Dipartimento di Chimica e Chimica Industriale, Università di
| | - Benedetta Mennucci
- Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Department of Chemistry, 80 St. George Street, Institute for Optical Sciences and Centre for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario M5S 3H6 Canada, Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi 17071 Girona, Catalonia, Spain, and Dipartimento di Chimica e Chimica Industriale, Università di
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26
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Uyeda G, Williams JC, Roman M, Mattioli TA, Allen JP. The Influence of Hydrogen Bonds on the Electronic Structure of Light-Harvesting Complexes from Photosynthetic Bacteria. Biochemistry 2010; 49:1146-59. [DOI: 10.1021/bi901247h] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- G. Uyeda
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
| | - J. C. Williams
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
| | - M. Roman
- Service de Bioénergétique, Département de Biologie Joliot Curie, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
| | - T. A. Mattioli
- Service de Bioénergétique, Département de Biologie Joliot Curie, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
| | - J. P. Allen
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
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27
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28
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29
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Kangur L, Leiger K, Freiberg A. Evidence for high-pressure-induced rupture of hydrogen bonds in LH2 photosynthetic antenna pigment-protein complexes. ACTA ACUST UNITED AC 2008. [DOI: 10.1088/1742-6596/121/11/112004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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30
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Kangur L, Timpmann K, Freiberg A. Stability of Integral Membrane Proteins under High Hydrostatic Pressure: The LH2 and LH3 Antenna Pigment−Protein Complexes from Photosynthetic Bacteria. J Phys Chem B 2008; 112:7948-55. [DOI: 10.1021/jp801943w] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Liina Kangur
- Institute of Physics, University of Tartu, Riia 142, Tartu 51014, Estonia, and Institute of Molecular and Cell Biology, University of Tartu, Riia 23, Tartu 51010, Estonia
| | - Kõu Timpmann
- Institute of Physics, University of Tartu, Riia 142, Tartu 51014, Estonia, and Institute of Molecular and Cell Biology, University of Tartu, Riia 23, Tartu 51010, Estonia
| | - Arvi Freiberg
- Institute of Physics, University of Tartu, Riia 142, Tartu 51014, Estonia, and Institute of Molecular and Cell Biology, University of Tartu, Riia 23, Tartu 51010, Estonia
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31
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Liu WL, Zheng ZR, Dai ZF, Liu ZG, Zhu RB, Wu WZ, Li AH, Yang YQ, Su WH. Effect of solvent on absorption spectra of all-trans-β-carotene under high pressure. J Chem Phys 2008; 128:124501. [DOI: 10.1063/1.2841022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
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32
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Ellervee A, Freiberg A. Formation of bacteriochlorophyll a coordination states under external high-pressure. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2007.11.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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33
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Leiger K, Freiberg A, Dahlbom MG, Hush NS, Reimers JR. Pressure-induced spectral changes for the special-pair radical cation of the bacterial photosynthetic reaction center. J Chem Phys 2007; 126:215102. [PMID: 17567219 DOI: 10.1063/1.2739513] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effect of pressure up to 6 kbars on the near to mid infrared absorption spectrum (7500-14,300 cm(-1) or 1333-700 nm) of the oxidized reaction center of Rhodobacter sphaeroides is measured and interpreted using density-functional B3LYP, INDO, and PM5 calculations. Two weak electronic transition origins at approximately 8010 and approximately 10,210 cm(-1) are unambiguously identified. The first transition is assigned to a Qy tripdoublet band that involves, in the localized description of the excitation, a triplet absorption on one of the bacteriochlorophyll molecules (PM) in the reaction center's special pair intensified by the presence of a radical cation on the other (PL). While most chlorophyll transition energies decrease significantly with increasing pressure, the tripdoublet band is found to be almost pressure insensitive. This difference is attributed to the additional increase in the tripdoublet-band energy accompanying compression of the pi-stacked special pair. The second band could either be the anticipated second Qy tripdoublet state, a Qx tripdoublet state, or a state involving excitation from a low-lying doubly occupied orbital to the half-occupied cationic orbital. A variety of absorption bands that are also resolved in the 8300-9600 cm(-1) region are assigned as vibrational structure associated with the first tripdoublet absorption. These sidebands are composites that are shown by the calculations to comprise many unresolved individual modes; while the calculated pressure sensitivity of each individual mode is small, the calculated pressure dependence of the combined sideband structure is qualitatively similar to the observed pressure dependence, preventing the positive identification of possible additional electronic transitions in this spectral region.
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Affiliation(s)
- Kristjan Leiger
- Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia
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34
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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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35
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Liu W, Lu Y, Liu Y, Liu K, Yan Y, Kong J, Xu C, Qian S. Effect of the in situ electrochemical oxidation on the pigment–protein arrangement and energy transfer in light-harvesting complex from Rhodobacter sphaeroides 601. Biochem Biophys Res Commun 2006; 340:505-11. [PMID: 16380087 DOI: 10.1016/j.bbrc.2005.12.034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Accepted: 12/05/2005] [Indexed: 11/20/2022]
Abstract
The oxidation of bacteriochlorophylls (BChls) in peripheral light-harvesting complexes (LH2) from Rhodobacter sphaeroides was investigated by spectroelectrochemistry of absorption, fluorescence emission, and femtosecond (fs) pump-probe, with the aim obtaining information about the effect of in situ electrochemical oxidation on the pigment-protein arrangement and energy transfer within LH2. The experimental results revealed that: (a) the generation of the BChl radical cation in both B800 and B850 rings dramatically induced bleaching of the characteristic absorption in the NIR region and quenching of the fluorescence emission from the B850 ring for the electrochemical oxidized LH2; (b) the BChl-B850 radical cation might act as an additional channel to compete with the unoxidized BChl-B850 molecules for rapidly releasing the excitation energy, however the B800-B850 energy transfer rate remained almost unchanged during the oxidation process.
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Affiliation(s)
- Weimin Liu
- Physics Department, Fudan University, Shanghai 200433, China
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36
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On the use of the MNDO-d semiempirical method for the structural study of chlorophyll b and anhydrous chlorophyll b dimer. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.theochem.2005.03.048] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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37
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Ellervee A, Linnanto J, Freiberg A. Spectroscopic and quantum chemical study of pressure effects on solvated chlorophyll. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2004.06.113] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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38
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Gall A, Ellervee A, Robert B, Freiberg A. The effect of internal voids in membrane proteins: high-pressure study of two photochemical reaction centres from Rhodobacter sphaeroides. FEBS Lett 2004; 560:221-5. [PMID: 14988026 DOI: 10.1016/s0014-5793(04)00117-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2003] [Revised: 12/31/2003] [Accepted: 01/23/2004] [Indexed: 11/15/2022]
Abstract
The effect of application of high pressure on the carotenoid-containing bacterial reaction centre from Rhodobacter sphaeroides strain 2.4.1 was studied, and compared to recent experiments performed on its carotenoid-less counterpart, isolated from strain R26.1. Our results indicate that the cavity created by the absence of carotenoid contributes to localised differences in protein compressibility when using the intrinsic chromophores as molecular probes. Differential stability of the electronic transitions of the primary electron donor under high hydrostatic pressure is observed, dependent on the presence of the carotenoid cofactor. This suggests that the transition intensity loss is induced by a slight change of the primary electron donor structure, allowed by the void created by the absence of the carotenoid molecule.
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Affiliation(s)
- Andrew Gall
- Service de Biophysique des Fonctions Membranaires, DBJC/CEA and URA CNRS 2096, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France.
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39
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Ng MF, Zhao Y, Chen GH. Low-Lying Excited States of Light-Harvesting System II in Purple Bacteria. J Phys Chem B 2003. [DOI: 10.1021/jp034320r] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Man-Fai Ng
- Department of Chemistry, University of Hong Kong, Hong Kong, P. R. China
| | - Yang Zhao
- Department of Chemistry, University of Hong Kong, Hong Kong, P. R. China
| | - Guan-Hua Chen
- Department of Chemistry, University of Hong Kong, Hong Kong, P. R. China
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40
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Excitonic optical line shapes of cyclic and elliptically deformed molecular aggregates with 18 units: influence of quasi-static and dynamic disorder. Chem Phys 2003. [DOI: 10.1016/s0301-0104(03)00003-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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41
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Zazubovich V, Jankowiak R, Small GJ. A High-Pressure Spectral Hole Burning Study of Correlation between Energy Disorder and Excitonic Couplings in the LH 2 Complex from Rhodopseudomonas Acidophila. J Phys Chem B 2002. [DOI: 10.1021/jp020540d] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- V. Zazubovich
- Ames Laboratory, U.S. Department of Energy and Department of Chemistry, Iowa State University, Ames, Iowa 50011
| | - R. Jankowiak
- Ames Laboratory, U.S. Department of Energy and Department of Chemistry, Iowa State University, Ames, Iowa 50011
| | - G. J. Small
- Ames Laboratory, U.S. Department of Energy and Department of Chemistry, Iowa State University, Ames, Iowa 50011
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