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Rätsep M, Linnanto JM, Freiberg A. Higher Order Vibronic Sidebands of Chlorophyll a and Bacteriochlorophyll a for Enhanced Excitation Energy Transfer and Light Harvesting. J Phys Chem B 2019; 123:7149-7156. [PMID: 31356081 DOI: 10.1021/acs.jpcb.9b06843] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Optical absorption and fluorescence spectra of molecules in condensed phases often show extensive sidebands. Originating from electron-vibrational and electron-phonon couplings, these spectral tails bear important information on the dynamics of electronic states and processes the molecules are involved in. The vibronic sidebands observed in conjugate Qy absorption and fluorescence spectra of chlorophyll a and bacteriochlorophyll a are relatively weak, characterized by the total Huang-Rhys factor which is less than one. Therefore, it is widely considered that only fundamental intramolecular modes are responsible for their formation. Here, we provide evidence for extra-long and structured fluorescence tails of chlorophyll a and bacteriochlorophyll a as far as 4000 cm-1 from respective spectral origins, far beyond the frequency range of fundamental modes. According to quantum chemical simulations, these sidebands extending to ∼960 nm in chlorophyll a and ∼1140 nm in bacteriochlorophyll a into the infrared part of the optical spectrum are mainly contributed to by vibrational overtones of the fundamental modes. Because energy transfer and relaxation processes generally depend on vibronic overlap integrals, these findings potentially contribute to better understanding of many vital photo-induced phenomena, including photosynthetic light harvesting.
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Affiliation(s)
- Margus Rätsep
- Institute of Physics , University of Tartu , W. Ostwald Street 1 , 50411 Tartu , Estonia
| | - Juha Matti Linnanto
- Institute of Physics , University of Tartu , W. Ostwald Street 1 , 50411 Tartu , Estonia
| | - Arvi Freiberg
- Institute of Physics , University of Tartu , W. Ostwald Street 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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Saggu M, Fried SD, Boxer SG. Local and Global Electric Field Asymmetry in Photosynthetic Reaction Centers. J Phys Chem B 2019; 123:1527-1536. [PMID: 30668130 DOI: 10.1021/acs.jpcb.8b11458] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The origin of unidirectional electron transfer in photosynthetic reaction centers (RCs) has been widely discussed. Despite the high level of structural similarity between the two branches of pigments that participate in the initial electron transfer steps of photosynthesis, electron transfer only occurs along one branch. One possible explanation for this functional asymmetry is the differences in the electrostatic environment between the active and the inactive branches arising from the charges and dipoles of the organized protein structure. We present an analysis of electric fields in the RC of the purple bacterium Rhodobacter sphaeroides using the intrinsic carbonyl groups of the pigments as vibrational reporters whose vibrational frequency shifts can be converted into electric fields based on the vibrational Stark effect and also provide Stark effect data for plant pigments that can be used in future studies. The carbonyl stretches of the isolated pigments show pronounced Stark effects. We use these data, solvatochromism, molecular dynamics simulations, and data in the literature from IR and Raman spectra to evaluate differences in fields at symmetry-related positions, in particular at the 9-keto and 2-acetyl positions of the pigments involved in primary charge separation.
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Affiliation(s)
- Miguel Saggu
- Department of Chemistry , Stanford University , Stanford , California 94305-5080 , United States
| | - Stephen D Fried
- Department of Chemistry , Stanford University , Stanford , California 94305-5080 , United States
| | - Steven G Boxer
- Department of Chemistry , Stanford University , Stanford , California 94305-5080 , United States
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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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Kimura Y, Inada Y, Numata T, Arikawa T, Li Y, Zhang JP, Wang ZY, Ohno T. Metal cations modulate the bacteriochlorophyll–protein interaction in the light-harvesting 1 core complex from Thermochromatium tepidum. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1022-9. [DOI: 10.1016/j.bbabio.2012.03.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 03/07/2012] [Accepted: 03/11/2012] [Indexed: 11/16/2022]
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McHale JL. Hierarchal Light-Harvesting Aggregates and Their Potential for Solar Energy Applications. J Phys Chem Lett 2012; 3:587-97. [PMID: 26286154 DOI: 10.1021/jz3000678] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The tunable optical properties of self-assembled chromophores are exploited by photosynthetic organisms to optimize their ability to harvest a broad range of the solar spectrum. Similarly, the efficiency of solar photovoltaic and photoelectrochemical devices depends strongly on the coincidence of the absorption spectrum of the photoactive components with the spectrum of the sun. While the possibility of borrowing ideas about light-harvesting aggregates from nature in order to improve the efficiency of solar energy conversion is quite attractive, progress to date is hindered by incomplete understanding of aggregate internal structure and its relation to excitonic states. In this Perspective, we describe our recent work on the hierarchal structure of self-assembled porphyrin aggregates that are similar to light-harvesting complexes of photosynthetic bacteria. We address the question of whether aggregation can be beneficial to dye-sensitized solar energy conversion and present promising results for a solar cell based on an abundant plant pigment that displays signatures of aggregation when adsorbed on TiO2.
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Affiliation(s)
- Jeanne L McHale
- Department of Chemistry, Washington State University, Pullman, Washington 99164-4630, United States
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Jing Y, Zheng R, Li HX, Shi Q. Theoretical Study of the Electronic–Vibrational Coupling in the Qy States of the Photosynthetic Reaction Center in Purple Bacteria. J Phys Chem B 2012; 116:1164-71. [DOI: 10.1021/jp209575q] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Yuanyuan Jing
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China
| | - Renhui Zheng
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China
| | - Hui-Xue Li
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China
| | - Qiang Shi
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China
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Rätsep M, Cai ZL, Reimers JR, Freiberg A. Demonstration and interpretation of significant asymmetry in the low-resolution and high-resolution Qy fluorescence and absorption spectra of bacteriochlorophyll a. J Chem Phys 2011; 134:024506. [DOI: 10.1063/1.3518685] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Frolov D, Marsh M, Crouch LI, Fyfe PK, Robert B, van Grondelle R, Hadfield A, Jones MR. Structural and Spectroscopic Consequences of Hexacoordination of a Bacteriochlorophyll Cofactor in the Rhodobacter sphaeroides Reaction Center,. Biochemistry 2010; 49:1882-92. [DOI: 10.1021/bi901922t] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Dmitrij Frolov
- Department of Physics and Astronomy, Free University of Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - May Marsh
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom
| | - Lucy I. Crouch
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom
| | - Paul K. Fyfe
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom
| | - Bruno Robert
- Service de Biophysique des Fonctions Membranaires, DBJC/CEA and URA 2096/CNRS, CEA-Saclay, F-91191 Gif-sur-Yvette, France
| | - Rienk van Grondelle
- Department of Physics and Astronomy, Free University of Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Andrea Hadfield
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom
| | - Michael R. Jones
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom
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Abstract
We report the results of extensive numerical simulations and theoretical calculations of electronic transitions in the reaction center of Rhodobacter sphaeroides photosynthetic bacterium. The energetics and kinetics of five electronic transitions related to the kinetic scheme of primary charge separation have been analyzed and compared to experimental observations. Nonergodic formulation of the reaction kinetics is required for the calculation of the rates due to a severe breakdown of the system ergodicity on the time scale of primary charge separation, with the consequent inapplicability of the standard canonical prescription to calculate the activation barrier. Common to all reactions studied is a significant excess of the charge-transfer reorganization energy from the width of the energy gap fluctuations over that from the Stokes shift of the transition. This property of the hydrated proteins, breaking the linear response of the thermal bath, allows the reaction center to significantly reduce the reaction free energy of near-activationless electron hops and thus raise the overall energetic efficiency of the biological charge-transfer chain. The increase of the rate of primary charge separation with cooling is explained in terms of the temperature variation of induction solvation, which dominates the average donor-acceptor energy gap for all electronic transitions in the reaction center. It is also suggested that the experimentally observed break in the Arrhenius slope of the primary recombination rate, occurring near the temperature of the dynamical transition in proteins, can be traced back to a significant drop of the solvent reorganization energy close to that temperature.
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Affiliation(s)
- David N Lebard
- Center for Biological Physics, Arizona State University, P.O. Box 871604, Tempe, Arizona 85287-1604, USA
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Robert B. Resonance Raman spectroscopy. PHOTOSYNTHESIS RESEARCH 2009; 101:147-55. [PMID: 19568956 DOI: 10.1007/s11120-009-9440-4] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Accepted: 05/19/2009] [Indexed: 05/18/2023]
Abstract
Resonance Raman spectroscopy may yield precise information on the conformation of, and on the interactions assumed by, the chromophores involved in the first steps of the photosynthetic process, whether isolated in solvents, embedded in soluble or membrane proteins, or, as shown recently, in vivo. By making use of this technique, it is possible, for instance, to relate the electronic properties of these molecules to their structure and/or the physical properties of their environment, or to determine subtle changes of their conformation associated with regulatory processes. After a short introduction to the physical principles that govern resonance Raman spectroscopy, the information content of resonance Raman spectra of chlorophyll and carotenoid molecules is described in this review, together with the experiments which helped in determining which structural parameter each Raman band is sensitive to. A selection of applications of this technique is then presented, in order to give a fair and precise idea of which type of information can be obtained from its use in the field of photosynthesis.
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Affiliation(s)
- Bruno Robert
- Institute of Biology and Technology of Saclay, Commissariat à l'Energie Atomique, URA 2096 Centre National de la Recherche Scientifique, Gif sur Yvette, France.
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Ma F, Kimura Y, Yu LJ, Wang P, Ai XC, Wang ZY, Zhang JP. Specific Ca2+-binding motif in the LH1 complex from photosynthetic bacterium Thermochromatium tepidum as revealed by optical spectroscopy and structural modeling. FEBS J 2009; 276:1739-49. [DOI: 10.1111/j.1742-4658.2009.06905.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Czarnecki K, Chen L, Diers JR, Frank HA, Bocian DF. Low-frequency resonance Raman studies of the H(M202)G cavity mutant of bacterial photosynthetic reaction centers. PHOTOSYNTHESIS RESEARCH 2006; 88:31-41. [PMID: 16847742 DOI: 10.1007/s11120-005-9019-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2005] [Accepted: 09/12/2005] [Indexed: 05/10/2023]
Abstract
Low-frequency (90-435 cm(-1)) NIR-excitation (875-900 nm) resonance Raman (RR) studies are reported for the H(M202)G cavity mutant of bacterial photosynthetic reaction centers (RCs) from Rb. sphaeroides that was first described by Goldsmith et al. [(1996) Biochemistry 35: 2421-2428]. In this mutant, the His residue that axially ligates the Mg ion of the M-side bacteriochlorophyll (BChl) of the special pair primary donor (P) is replaced by a non-ligating Gly residue. Regardless, the Mg ion of P(M) in the H(M202)G RCs remains pentacoordinates and is presumably ligated by a water molecule, although this axial ligand has not been definitively identified. The low-frequency RR studies of the H(M202)G RCs are accompanied by studies of RCs exchanged with D(2)O and incubated with imidazole (Im). The RR studies of the cavity mutant RCs reveal the following: (1) The structure of P(M) in the H(M202)G RCs is different from that of the wild-type, consistent with an altered BChl core. (2) A water ligand for P(M) in the H(M202)G RCs is generally consistent with the low-frequency RR spectra. The Mg-OH(2) stretching vibration is tentatively assigned to a band at 318 cm(-1), a frequency higher than that of the Mg-His stretch of the native pigment ( approximately approximately 235 cm(-1)). (3) The BChl core structure of P(M) in the cavity mutant is rendered similar (but not identical) to that of the wild-type when the adventitious water axial ligand is replaced by Im. (4) Exchange with D(2)O results in more global structural changes, likely involving the protein, which in turn affect the structure of the BChls in P. (5) Assignment of the low-frequency vibrational spectrum of P is generally more complex than originally suggested.
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Affiliation(s)
- Kazimierz Czarnecki
- Department of Chemistry, University of California, Riverside, California 92521-0403, USA.
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Wakeham MC, Jones MR. Rewiring photosynthesis: engineering wrong-way electron transfer in the purple bacterial reaction centre. Biochem Soc Trans 2005; 33:851-7. [PMID: 16042613 DOI: 10.1042/bst0330851] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The purple bacterial reaction centre uses light energy to separate charge across the cytoplasmic membrane, reducing ubiquinone and oxidizing a c-type cytochrome. The protein possesses a macroscopic structural two-fold symmetry but displays a strong functional asymmetry, with only one of two available membrane-spanning branches of cofactors (the so-called A-branch) being used to catalyse photochemical charge separation. The factors underlying this functional asymmetry have been the subject of study for many years but are still not fully understood. Site-directed mutagenesis has been partially successful in rerouting electron transfer along the normally inactive B-branch, allowing comparison of the kinetics of equivalent electron transfer reactions on the two branches. Both the primary and secondary electron transfer steps on the B-branch appear to be considerably slower than their A-branch counterparts. The effectiveness of different mutations in rerouting electron transfer along the B-branch of cofactors is discussed.
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Affiliation(s)
- M C Wakeham
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol, BS8 1TD, UK
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Frolov D, Wakeham MC, Andrizhiyevskaya EG, Jones MR, van Grondelle R. Investigation of B-branch electron transfer by femtosecond time resolved spectroscopy in a Rhodobacter sphaeroides reaction centre that lacks the QA ubiquinone. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2005; 1707:189-98. [PMID: 15863097 DOI: 10.1016/j.bbabio.2004.12.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2004] [Revised: 11/30/2004] [Accepted: 12/01/2004] [Indexed: 11/27/2022]
Abstract
The dynamics of electron transfer in a membrane-bound Rhodobacter sphaeroides reaction centre containing a combination of four mutations were investigated by transient absorption spectroscopy. The reaction centre, named WAAH, has a mutation that causes the reaction centre to assemble without a Q(A) ubiquinone (Ala M260 to Trp), a mutation that causes the replacement of the H(A) bacteriopheophytin with a bacteriochlorophyll (Leu M214 to His) and two mutations that remove acidic groups close to the Q(B) ubiquinone (Glu L212 to Ala and Asp L213 to Ala). Previous work has shown that the Q(B) ubiquinone is reduced by electron transfer along the so-called inactive cofactor branch (B-branch) in the WAAH reaction centre (M.C. Wakeham, M.G. Goodwin, C. McKibbin, M.R. Jones, Photo-accumulation of the P(+)Q(B)(-) radical pair state in purple bacterial reaction centres that lack the Q(A) ubiquinone, FEBS Letters 540 (2003) 234-240). In the present study the dynamics of electron transfer in the membrane-bound WAAH reaction centre were studied by femtosecond transient absorption spectroscopy, and the data analysed using a compartmental model. The analysis indicates that the yield of Q(B) reduction via the B-branch is approximately 8% in the WAAH reaction centre, consistent with results from millisecond time-scale kinetic spectroscopy. Possible contributions to this yield of the constituent mutations in the WAAH reaction centre and the membrane environment of the complex are discussed.
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Affiliation(s)
- Dmitrij Frolov
- Department of Physics and Astronomy, Free University of Amsterdam, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands.
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Chen M, Zeng H, Larkum AWD, Cai ZL. Raman properties of chlorophyll d, the major pigment of Acaryochloris marina: studies using both Raman spectroscopy and density functional theory. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2004; 60:527-534. [PMID: 14747075 DOI: 10.1016/s1386-1425(03)00258-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The Raman spectroscopy of purified chlorophyll (Chl) d extracted from Acaryochloris marina has been measured over the wide region of 250-3200 cm(-1) at 77 K following excitation of its Soret band at 488 nm and analyzed with the aid of hybrid density-functional vibrational analyses. A Raman peak specific to Chl d, which arises from the formyl group 3(1) C=O stretching, was clearly observed at 1659 cm(-1) with medium intensity. Peaks due to other C=O stretching vibrations of the 13(1) keto-, 13(3) ester- and 17(3) groups were also observed. Four very strong peaks were observed in the range of 1000-1600 cm(-1), assigned to the CC stretching and mixtures of the CH3 bend and CN stretching. CCC and NCC bending contribute to medium intensity peaks at 986 and 915 cm(-1). Out-of-plane CH bending at Chl d methine sites 10, 5 and 20 contribute to observed peaks at 885, 864 and 853 cm(-1), respectively. A few modes involving the MgN stretching and MgNC bending motions were observed in the very low frequency range. Density functional theory (DFT) calculations have been used to make assignments on the observed Raman spectrum and the DFT results have been found to be in good agreement with the experimental results.
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Affiliation(s)
- Min Chen
- School of Biological Sciences, The University of Sydney, Sydney, NSW 2006, Australia
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Ceccarelli M, Marchi M. Simulation and Modeling of the Rhodobacter sphaeroides Bacterial Reaction Center: Structure and Interactions. J Phys Chem B 2003. [DOI: 10.1021/jp0270001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Matteo Ceccarelli
- CECAM, Centre Européen de Calcul Atomique et Moleculaire, Ecole Normale Superieure de Lyon, 46 Allée d'Italie, 69364 Lyon, France
| | - Massimo Marchi
- Commissariat à l'Energie Atomique, DSV-DBJC-SBFM, Centre d'Études, Saclay, 91191 Gif-sur-Yvette Cedex, France
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