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Bhattacharjee S, Neese F, Pantazis DA. Triplet states in the reaction center of Photosystem II. Chem Sci 2023; 14:9503-9516. [PMID: 37712047 PMCID: PMC10498673 DOI: 10.1039/d3sc02985a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Accepted: 08/16/2023] [Indexed: 09/16/2023] Open
Abstract
In oxygenic photosynthesis sunlight is harvested and funneled as excitation energy into the reaction center (RC) of Photosystem II (PSII), the site of primary charge separation that initiates the photosynthetic electron transfer chain. The chlorophyll ChlD1 pigment of the RC is the primary electron donor, forming a charge-separated radical pair with the vicinal pheophytin PheoD1 (ChlD1+PheoD1-). To avert charge recombination, the electron is further transferred to plastoquinone QA, whereas the hole relaxes to a central pair of chlorophylls (PD1PD2), subsequently driving water oxidation. Spin-triplet states can form within the RC when forward electron transfer is inhibited or back reactions are favored. This can lead to formation of singlet dioxygen, with potential deleterious effects. Here we investigate the nature and properties of triplet states within the PSII RC using a multiscale quantum-mechanics/molecular-mechanics (QM/MM) approach. The low-energy spectrum of excited singlet and triplet states, of both local and charge-transfer nature, is compared using range-separated time-dependent density functional theory (TD-DFT). We further compute electron paramagnetic resonance properties (zero-field splitting parameters and hyperfine coupling constants) of relaxed triplet states and compare them with available experimental data. Moreover, the electrostatic modulation of excited state energetics and redox properties of RC pigments by the semiquinone QA- is described. The results provide a detailed electronic-level understanding of triplet states within the PSII RC and form a refined basis for discussing primary and secondary electron transfer, charge recombination pathways, and possible photoprotection mechanisms in PSII.
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Affiliation(s)
- Sinjini Bhattacharjee
- Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1 45470 Mülheim an der Ruhr Germany
| | - Frank Neese
- Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1 45470 Mülheim an der Ruhr Germany
| | - Dimitrios A Pantazis
- Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1 45470 Mülheim an der Ruhr Germany
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Hayase T, Shimada Y, Mitomi T, Nagao R, Noguchi T. Triplet Delocalization over the Reaction Center Chlorophylls in Photosystem II. J Phys Chem B 2023; 127:1758-1770. [PMID: 36809007 DOI: 10.1021/acs.jpcb.3c00139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
The triplet state of chlorophyll formed by charge recombination in photosystem II (PSII) is a precursor of harmful singlet oxygen. Although main localization of the triplet state on the monomeric chlorophyll, ChlD1, at cryogenic temperatures has been suggested, how the triplet state is delocalized on other chlorophylls remains unclear. Here, we investigated the distribution of the triplet state of chlorophyll in PSII using light-induced Fourier transform infrared (FTIR) difference spectroscopy. Measurements of triplet-minus-singlet FTIR difference spectra with PSII core complexes from cyanobacterial mutants, D1-V157H, D2-V156H, D2-H197A, and D1-H198A, in which the interactions of the 131-keto C═O groups of the reaction center chlorophylls, PD1, PD2, ChlD1, and ChlD2, respectively, were perturbed, identified the 131-keto C═O bands of the individual chlorophylls and showed that the triplet state is delocalized over all of these chlorophylls. It is suggested that the triplet delocalization plays important roles in the photoprotection and photodamage mechanisms in PSII.
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Affiliation(s)
- Taichi Hayase
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Yuichiro Shimada
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Tatsuya Mitomi
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Ryo Nagao
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.,Faculty of Agriculture, Shizuoka University, Shizuoka 422-8529, Japan
| | - Takumi Noguchi
- Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
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Niklas J, Agostini A, Carbonera D, Di Valentin M, Lubitz W. Primary donor triplet states of Photosystem I and II studied by Q-band pulse ENDOR spectroscopy. PHOTOSYNTHESIS RESEARCH 2022; 152:213-234. [PMID: 35290567 PMCID: PMC9424170 DOI: 10.1007/s11120-022-00905-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 02/14/2022] [Indexed: 05/05/2023]
Abstract
The photoexcited triplet state of the "primary donors" in the two photosystems of oxygenic photosynthesis has been investigated by means of electron-nuclear double resonance (ENDOR) at Q-band (34 GHz). The data obtained represent the first set of 1H hyperfine coupling tensors of the 3P700 triplet state in PSI and expand the existing data set for 3P680. We achieved an extensive assignment of the observed electron-nuclear hyperfine coupling constants (hfcs) corresponding to the methine α-protons and the methyl group β-protons of the chlorophyll (Chl) macrocycle. The data clearly confirm that in both photosystems the primary donor triplet is located on one specific monomeric Chl at cryogenic temperature. In comparison to previous transient ENDOR and pulse ENDOR experiments at standard X-band (9-10 GHz), the pulse Q-band ENDOR spectra demonstrate both improved signal-to-noise ratio and increased resolution. The observed ENDOR spectra for 3P700 and 3P680 differ in terms of the intensity loss of lines from specific methyl group protons, which is explained by hindered methyl group rotation produced by binding site effects. Contact analysis of the methyl groups in the PSI crystal structure in combination with the ENDOR analysis of 3P700 suggests that the triplet is located on the Chl a' (PA) in PSI. The results also provide additional evidence for the localization of 3P680 on the accessory ChlD1 in PSII.
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Affiliation(s)
- Jens Niklas
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany.
- Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Ave., Lemont, IL, 60439, USA.
| | - Alessandro Agostini
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy
- Biology Centre, Institute of Plant Molecular Biology, Czech Academy of Sciences, Branišovská 31, 370 05, Ceske Budejovice, Czech Republic
| | - Donatella Carbonera
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy
| | - Marilena Di Valentin
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy.
| | - Wolfgang Lubitz
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany.
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High-Field/High-Frequency Electron Paramagnetic Resonance Involving Single- and Multiple-Transition Schemes. BIOPHYSICAL TECHNIQUES IN PHOTOSYNTHESIS 2008. [DOI: 10.1007/978-1-4020-8250-4_14] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Guzmán MI, Colussi AJ, Hoffmann MR. Photogeneration of Distant Radical Pairs in Aqueous Pyruvic Acid Glasses. J Phys Chem A 2006; 110:931-5. [PMID: 16419992 DOI: 10.1021/jp053449t] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The lambda > 300 nm photolysis of h4- or d4-pyruvic acid aqueous glasses at 77 K yields identical electron magnetic resonance (EMR) spectra arising from distant (r greater or similar 0.5 nm) triplet radical pairs. Spectra comprise: (1) well-resolved quartets, X, at g approximately ge, that closely match the powder spectra of spin pairs interacting across r approximately 1.0 nm with D approximately 3.0 mT, E approximately 0 mT zero field splittings (ZFS), and (2) broad signals, Y, centered at g approximately 2.07 that display marked g-anisotropy and g-strain, exclude D greater or similar 20.0 mT values (i.e., r less or similar 0.5 spin nm separations), and track the temperature dependence of related g approximately 4 features. These results imply that the n-pi excitation of pyruvic acid, PA, induces long-range electron transfer from the promoted carbonyl chromophore into neighboring carbonyl acceptors, rather than homolysis into contact radical pairs or concerted decarboxylation into a carbene. Since PA is associated into hydrogen-bonded dimers prior to vitrification, X signals arise from radical pairs ensuing intradimer electron transfer to a locked acceptor, while Y signals involve carbonyl groups attached to randomly arranged, disjoint monomers. The ultrafast decarboxylation of primary radical ion pairs, 3[PA+* PA-*], accounts for the release of CO2 under cryogenic conditions, the lack of thermal hysteresis displayed by magnetic signals between 10 and 160 K, and averted charge retrotransfer. All EMR signals disappear irreversibly above the onset of ice diffusivity at approximately 190 K.
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Affiliation(s)
- Marcelo I Guzmán
- W. M. Keck Laboratories, California Institute of Technology, Pasadena, California 91125, USA
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Hertel MM, Denysenkov VP, Bennati M, Prisner TF. Pulsed 180-GHz EPR/ENDOR/PELDOR spectroscopy. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2005; 43 Spec no.:S248-55. [PMID: 16235223 DOI: 10.1002/mrc.1681] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Within this review, we describe a home-built pulsed electron paramagnetic resonance (EPR) spectrometer operating at 180 GHz as well as the incorporation of two double resonance techniques, electron nuclear double resonance (ENDOR) and pulsed electron double resonance (PELDOR), along with first applications. Hahn-echo decays on a TEMPO/polystyrene sample are presented, demonstrating that the observation of anisotropic librational motions is possible in a very precise manner at high magnetic fields. Bisdiphenylene-phenyl-allyl is used as a model system to illustrate the performance of the setup for 1H-ENDOR using the Mims as well as the Davies sequence. Furthermore, first 1H-Mims and Davies ENDOR spectra on a biological sample, the wild-type Ras*Mn2+*GDP protein, are reported. The capability of the 180-GHz PELDOR setup is demonstrated using the three-pulse ELDOR sequence on the protein ribonucleotide reductase (RNR) subunit R2 from Escherichia coli, which contains two tyrosyl radicals at a 33 angstroms distance. At 180 GHz, orientation selectivity is observed and the modulation frequency is found to be in good agreement with theoretical predictions.
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Affiliation(s)
- M M Hertel
- Institute for Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance, J. W. Goethe-University, Frankfurt am Main, Germany
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Feikema WO, Gast P, Klenina IB, Proskuryakov II. EPR characterisation of the triplet state in photosystem II reaction centers with singly reduced primary acceptor Q(A). BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2005; 1709:105-12. [PMID: 16095558 DOI: 10.1016/j.bbabio.2005.07.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2004] [Revised: 07/14/2005] [Accepted: 07/18/2005] [Indexed: 11/30/2022]
Abstract
The triplet states of photosystem II core particles from spinach were studied using time-resolved cw EPR technique at different reduction states of the iron--quinone complex of the reaction center primary electron acceptor. With doubly reduced primary acceptor, the well-known photosystem II triplet state characterised by zero-field splitting parameters |D|=0.0286 cm(-1), |E|=0.0044 cm(-1) was detected. When the primary acceptor was singly reduced either chemically or photochemically, a triplet state of a different spectral shape was observed, bearing the same D and E values and characteristic spin polarization pattern arising from RC radical pair recombination. The latter triplet state was strongly temperature dependent disappearing at T=100 K, and had a much faster decay than the former one. Based on its properties, this triplet state was also ascribed to the photosystem II reaction center. A sequence of electron-transfer events in the reaction centers is proposed that explains the dependence of the triplet state properties on the reduction state of the iron--quinone primary acceptor complex.
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Affiliation(s)
- W Onno Feikema
- Department of Biophysics, Huygens Laboratory, P.O. Box 9504, 2300 RA Leiden, The Netherlands
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Kropacheva TN, Germano M, Zucchelli G, Jennings RC, van Gorkom HJ. Circular dichroism of the peripheral chlorophylls in photosystem II reaction centers revealed by electrochemical oxidation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2005; 1709:119-26. [PMID: 16054591 DOI: 10.1016/j.bbabio.2005.04.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Revised: 04/14/2005] [Accepted: 04/19/2005] [Indexed: 11/19/2022]
Abstract
Visible absorption spectra and circular dichroism (CD) of the red absorption band of isolated photosystem II reaction centers were measured at room temperature during progressive bleaching by electrochemical oxidation, in comparison with aerobic photochemical destruction, and with anaerobic photooxidation in the presence of the artificial electron acceptor silicomolybdate. Initially, selective bleaching of peripheral chlorophylls absorbing at 672 nm was obtained by electrochemical oxidation at +0.9 V, whereas little selectivity was observed at higher potentials. Illumination in the presence of silicomolybdate did not cause a bleaching but a spectral broadening of the 672-nm band was observed, apparently in response to the oxidation of carotene. The 672-nm absorption band is shown to exhibit a positive CD, which accounts for the 674-nm shoulder in CD spectra at low temperature. The origin of this CD is discussed in view of the observation that all CD disappears with the 680-nm absorption band during aerobic photodestruction.
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Affiliation(s)
- Tatyana N Kropacheva
- Chemistry Department, Udmurt State University, Universitetskaya 1, Izhevsk 426037, Russia.
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