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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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Ciuti S, Agostini A, Barbon A, Bortolus M, Paulsen H, Di Valentin M, Carbonera D. Magnetophotoselection in the Investigation of Excitonically Coupled Chromophores: The Case of the Water-Soluble Chlorophyll Protein. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27123654. [PMID: 35744779 PMCID: PMC9227413 DOI: 10.3390/molecules27123654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 06/01/2022] [Accepted: 06/02/2022] [Indexed: 12/01/2022]
Abstract
A magnetophotoselection (MPS) investigation of the photoexcited triplet state of chlorophyll a both in a frozen organic solvent and in a protein environment, provided by the water-soluble chlorophyll protein (WSCP) of Lepidium virginicum, is reported. The MPS experiment combines the photoselection achieved by exciting with linearly polarized light with the magnetic selection of electron paramagnetic resonance (EPR) spectroscopy, allowing the determination of the relative orientation of the optical transition dipole moment and the zero-field splitting tensor axes in both environments. We demonstrate the robustness of the proposed methodology for a quantitative description of the excitonic interactions among pigments. The orientation of the optical transition dipole moments determined by the EPR analysis in WSCP, identified as an appropriate model system, are in excellent agreement with those calculated in the point-dipole approximation. In addition, MPS provides information on the electronic properties of the triplet state, localized on a single chlorophyll a pigment of the protein cluster, in terms of orientation of the zero-field splitting tensor axes in the molecular frame.
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Affiliation(s)
- Susanna Ciuti
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy; (S.C.); (A.A.); (A.B.); (M.B.)
| | - Alessandro Agostini
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy; (S.C.); (A.A.); (A.B.); (M.B.)
- Biology Centre, Czech Academy of Sciences, Institute of Plant Molecular Biology, Branišovská 1160/31, 370 05 České Budějovice, Czech Republic
| | - Antonio Barbon
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy; (S.C.); (A.A.); (A.B.); (M.B.)
| | - Marco Bortolus
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy; (S.C.); (A.A.); (A.B.); (M.B.)
| | - Harald Paulsen
- Institute of Molecular Physiology, Johannes Gutenberg-University of Mainz, Johann-Joachim Becher-Weg 7, 55128 Mainz, Germany;
| | - Marilena Di Valentin
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy; (S.C.); (A.A.); (A.B.); (M.B.)
- Correspondence: (M.D.V.); (D.C.); Tel.: +39-0498275139 (M.D.V.); +39-0498275144 (D.C.)
| | - Donatella Carbonera
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy; (S.C.); (A.A.); (A.B.); (M.B.)
- Correspondence: (M.D.V.); (D.C.); Tel.: +39-0498275139 (M.D.V.); +39-0498275144 (D.C.)
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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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Alexeree S, ElZorkany HE, Abdel-Salam Z, Harith MA. A novel synthesis of a chlorophyll b-gold nanoconjugate used for enhancing photodynamic therapy: In vitro study. Photodiagnosis Photodyn Ther 2021; 35:102444. [PMID: 34284147 DOI: 10.1016/j.pdpdt.2021.102444] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 06/12/2021] [Accepted: 07/12/2021] [Indexed: 11/18/2022]
Abstract
Chlorophyll, the essential green pigment in plants, is considered a promising natural photosensitizer (PS) for photodynamic therapy (PDT). However, it suffers from lower stability in the physiological conditions that depress its efficacy in the PDT. The combination of nanotechnology and PDT is becoming a promising approach to combat tumors. Gold nanoparticles (Au NPs), for example, are proposed as suitable carriers that can increase chlorophyll stability when conjugating together. In the present work, the impact of Au NPs conjugation in enhancing Chlorophyll b (Chl b) efficiency in the PDT of cancer cells has been emphasized. A chemical method using a natural product synthesized a novel Chlorophyll b-gold nanoparticles nanoconjugate (Chl b-Au NCs). The synthesized Chl b-Au NCs were characterized via UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Laser-Induced Fluorescence (LIF), Zeta potential, Dynamic light scattering (DLS), and Transmission electron microscopy (TEM). Chl b is characterized by a formyl group (CHO) which is absent in Chl a. This group leads to the formation of an electrostatic reaction between the positive charge of Chl b and the negative charge present on the surface of the gold nanoparticles. Moreover, Chlorophyll b loading on the biosynthesized gold nanoparticles (Au NPs) increases its photostability. The efficiency of the PDT was then studied on the MCF7 and the HepG2 cells using this conjugation. As a result, the prepared Chl b-Au NCs showed low dark toxicity, excellent photostability under laser irradiation of wavelength 650 nm, in addition to a significantly high PDT efficacy against tumor cells in vitro. This is due to the enhanced cellular uptake and the high reactive oxygen species (ROS) production upon laser irradiation. Therefore, the designed Chl b-Au NCs could be a photo-therapeutic agent for enhancing cancer therapy in future applications.
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Affiliation(s)
- Shaimaa Alexeree
- National Institute of Laser Enhanced Science, Cairo University, Egypt
| | - Heba ElSayed ElZorkany
- Nanotechnology and Advanced Materials Central Lab, Agriculture Research Center, El Gamaa St., Giza, Egypt
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Barbon A, Dal Farra MG, Ciuti S, Albertini M, Bolzonello L, Orian L, Di Valentin M. Comprehensive investigation of the triplet state electronic structure of free-base 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin by a combined advanced EPR and theoretical approach. J Chem Phys 2020; 152:034201. [PMID: 31968969 DOI: 10.1063/1.5131753] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The nature of the photoexcited triplet state of free-base 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H2TPPS4-) has been investigated by advanced Electron Paramagnetic Resonance (EPR) techniques combined with quantum chemical calculations. The zero-field splitting (ZFS) parameters, D and E, the orientation of the transition dipole moment in the ZFS tensor frame, and the proton hyperfine couplings have been determined by magnetophotoselection-EPR and pulse electron-nuclear double resonance spectroscopy. Both time-resolved and pulse experiments exploit the electron spin polarization of the photoexcited triplet state. Comparison of the magnetic observables with computational results, including CASSCF calculations of the ZFS interaction tensor, provides an accurate picture of the triplet-state electronic structure. The theoretical investigation has been integrated with a systematic analysis on the parent free-base porphyrin molecule to assess the effect of the sulfonatophenyl substituents on the magnetic tensors. Additionally, the magnetophotoselection effects are discussed in terms of tautomerization in the excited singlet state of H2TPPS4-.
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Affiliation(s)
- Antonio Barbon
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Maria Giulia Dal Farra
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Susanna Ciuti
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Marco Albertini
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Luca Bolzonello
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Laura Orian
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Marilena Di Valentin
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
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