scholarly journals HYSCORE and DFT Studies of Proton-Coupled Electron Transfer in a Bioinspired Artificial Photosynthetic Reaction Center

2020 ◽  
Author(s):  
Dalvin D Méndez-Hernández ◽  
Amgalanbaatar Baldansuren ◽  
Vidmantas Kalendra ◽  
Philip Charles ◽  
Brian Mark ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electronic Structure ◽  
Reaction Center ◽  
Water Oxidation ◽  
Density Functional ◽  
Photosynthetic Reaction Center ◽  
Strong Hydrogen Bond ◽  
Water Molecules ◽  
Proton Coupled Electron Transfer ◽  
Artificial Photosynthetic

<p>Light-driven water oxidation in algae, cyanobacteria, and higher plants generates dioxygen that supports life on Earth. The water-oxidation reaction is catalyzed by the oxygen-evolving complex (OEC) in photosystem II (PSII) that is comprised of the tetranuclear manganese calcium-oxo (Mn<sub>4</sub>CaO<sub>5</sub>) cluster, with participation of the redox-active tyrosine residue (Y<sub>Z</sub>) and a hydrogen-bonded network of amino acids and water molecules. Y<sub>Z</sub> mediates successive proton-coupled electron transfer (PCET) reactions that are essential for the oxidation of water to dioxygen at the Mn<sub>4</sub>CaO<sub>5</sub> cluster. It has been proposed that the strong hydrogen bond between Y<sub>Z</sub> and and its conjugate base, D1-His190, likely renders Y<sub>Z</sub> kinetically and thermodynamically competent leading to highly efficient water oxidation.<sup>1</sup> However, a detailed understanding of PCET at Y<sub>Z</sub> remains elusive due to the transient nature of its intermediate states. In this study, we utilize a combination of high-resolution two-dimensional (2D) <sup>14</sup>N hyperfine sublevel correlation (HYSCORE) spectroscopy and density functional theory (DFT) methods to investigate the electronic structure of a bioinspired artificial photosynthetic reaction center, benzimidazole-phenol porphyrin (BiP–PF<sub>10</sub>), that mimics the PCET process at the Y<sub>Z</sub> residue of PSII. The results of these studies underscore the importance of proximal water molecules and charge delocalization on the electronic structure of the artificial reaction center.</p>

scholarly journals HYSCORE and DFT Studies of Proton-Coupled Electron Transfer in a Bioinspired Artificial Photosynthetic Reaction Center

2020 ◽  
Author(s):  
Dalvin D Méndez-Hernández ◽  
Amgalanbaatar Baldansuren ◽  
Vidmantas Kalendra ◽  
Philip Charles ◽  
Brian Mark ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electronic Structure ◽  
Reaction Center ◽  
Water Oxidation ◽  
Density Functional ◽  
Photosynthetic Reaction Center ◽  
Strong Hydrogen Bond ◽  
Water Molecules ◽  
Proton Coupled Electron Transfer ◽  
Artificial Photosynthetic

<p>Light-driven water oxidation in algae, cyanobacteria, and higher plants generates dioxygen that supports life on Earth. The water-oxidation reaction is catalyzed by the oxygen-evolving complex (OEC) in photosystem II (PSII) that is comprised of the tetranuclear manganese calcium-oxo (Mn<sub>4</sub>CaO<sub>5</sub>) cluster, with participation of the redox-active tyrosine residue (Y<sub>Z</sub>) and a hydrogen-bonded network of amino acids and water molecules. Y<sub>Z</sub> mediates successive proton-coupled electron transfer (PCET) reactions that are essential for the oxidation of water to dioxygen at the Mn<sub>4</sub>CaO<sub>5</sub> cluster. It has been proposed that the strong hydrogen bond between Y<sub>Z</sub> and and its conjugate base, D1-His190, likely renders Y<sub>Z</sub> kinetically and thermodynamically competent leading to highly efficient water oxidation.<sup>1</sup> However, a detailed understanding of PCET at Y<sub>Z</sub> remains elusive due to the transient nature of its intermediate states. In this study, we utilize a combination of high-resolution two-dimensional (2D) <sup>14</sup>N hyperfine sublevel correlation (HYSCORE) spectroscopy and density functional theory (DFT) methods to investigate the electronic structure of a bioinspired artificial photosynthetic reaction center, benzimidazole-phenol porphyrin (BiP–PF<sub>10</sub>), that mimics the PCET process at the Y<sub>Z</sub> residue of PSII. The results of these studies underscore the importance of proximal water molecules and charge delocalization on the electronic structure of the artificial reaction center.</p>

scholarly journals HYSCORE and DFT Studies of Proton-Coupled Electron Transfer in a Bioinspired Artificial Photosynthetic Reaction Center

iScience ◽  
2020 ◽  
Vol 23 (8) ◽  
pp. 101366
Author(s):  
Dalvin D. Méndez-Hernández ◽  
Amgalanbaatar Baldansuren ◽  
Vidmantas Kalendra ◽  
Philip Charles ◽  
Brian Mark ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Reaction Center ◽  
Photosynthetic Reaction Center ◽  
Dft Studies ◽  
Proton Coupled Electron Transfer ◽  
Artificial Photosynthetic

Computational Investigation of the Asymmetry in Photosynthetic Reaction Center Models from First Principles

2020 ◽  
Author(s):  
Denis Artiukhin ◽  
Patrick Eschenbach ◽  
Johannes Neugebauer
Keyword(s):  
Spin Density ◽  
Reaction Center ◽  
Density Functional ◽  
Photosynthetic Reaction Center ◽  
Chem Phys ◽  
Molecular Structures ◽  
Error Characteristic ◽  
Molecular Systems ◽  
Density Distributions ◽  
The Asymmetry

We present a computational analysis of the asymmetry in reaction center models of photosystem I, photosystem II, and bacteria from <i>Synechococcus elongatus</i>, <i>Thermococcus vulcanus</i>, and <i>Rhodobacter sphaeroides</i>, respectively. The recently developed FDE-diab methodology [J. Chem. Phys., 148 (2018), 214104] allowed us to effectively avoid the spin-density overdelocalization error characteristic for standard Kohn–Sham Density Functional Theory and to reliably calculate spin-density distributions and electronic couplings for a number of molecular systems ranging from dimeric models in vacuum to large protein including up to about 2000 atoms. The calculated spin densities showed a good agreement with available experimental results and were used to validate reaction center models reported in the literature. We demonstrated that the applied theoretical approach is very sensitive to changes in molecular structures and relative orientation of molecules. This makes FDE-diab a valuable tool for electronic structure calculations of large photosynthetic models effectively complementing the existing experimental techniques.

Excited states of analogue models of M-bacteriochlorophylls (M = Mg, Zn) in the photosynthetic reaction center: a time-dependent density functional theory study

2002 ◽  
Vol 06 (10) ◽  
pp. 617-625 ◽  
Author(s):  
Yoichi Yamaguchi
Keyword(s):  
Electron Transfer ◽  
Excited States ◽  
Density Functional ◽  
Photosynthetic Reaction Center ◽  
Excited Electron ◽  
Time Dependent ◽  
Analogue Model ◽  
Functional Theory ◽  
Special Pair ◽  
Dependent Density

Using time-dependent density functional theory (TDDFT), the excited states of the analogue model Mg -bacteriochlorophyll b - imidazole ( BChl -Im) dimer (P) for a special pair in the photosynthetic reaction center (RC) of Rhodopseudomonas (Rps.) viridis were examined. The calculated low-lying excited states and optimal geometries are in good agreement with experimental data. The order of the lowest unoccupied molecular orbital (LUMO) energies of P, the monomeric "accessory" BChl -Im (B), and bacteriopheophytin b ( H ) indicates the possibility of the light-induced electron transfer from P to H via B. The Im ligand of B destabilizes Goutermann's four-orbitals of BChl by 0.3-0.4 eV. With no energetic difference in the LUMOs between H and BChl , the Im ligands of P and B play an important role in providing a greater energetic gradient to the LUMOs along with the pathway for the excited-electron transfer in RC, resulting in the reduced reverse electron transfer from H to P (via B). Thus it is expected that the asymmetric Mg -Im interactions will directly affect the pathway of the excited-electron transfer. Using the deformed heterodimer (P') formed by the BChl halves with and without Im as the primary donor model, its cation radical P'+ was calculated as to whether the experimental asymmetric spin-density distribution can reproduce. The excited states of the analogue model Zn - BChl -Im dimer for a special pair in RC of the recently discovered Acidiphilium rubrum were also examined for a comparison with P.

scholarly journals Electronic Structure of Tyrosyl D Radical of Photosystem II, as Revealed by 2D-Hyperfine Sublevel Correlation Spectroscopy

2021 ◽  
Vol 7 (9) ◽  
pp. 131
Author(s):  
Maria Chrysina ◽  
Georgia Zahariou ◽  
Nikolaos Ioannidis ◽  
Yiannis Sanakis ◽  
George Mitrikas
Keyword(s):  
Electronic Structure ◽  
Photosystem Ii ◽  
Water Oxidation ◽  
Spinacia Oleracea ◽  
Higher Plants ◽  
Correlation Spectroscopy ◽  
Oxygen Evolving Complex ◽  
Higher Plant ◽  
Proton Coupled Electron Transfer ◽  
S Oxidation

The biological water oxidation takes place in Photosystem II (PSII), a multi-subunit protein located in thylakoid membranes of higher plant chloroplasts and cyanobacteria. The catalytic site of PSII is a Mn4Ca cluster and is known as the oxygen evolving complex (OEC) of PSII. Two tyrosine residues D1-Tyr161 (YZ) and D2-Tyr160 (YD) are symmetrically placed in the two core subunits D1 and D2 and participate in proton coupled electron transfer reactions. YZ of PSII is near the OEC and mediates electron coupled proton transfer from Mn4Ca to the photooxidizable chlorophyll species P680+. YD does not directly interact with OEC, but is crucial for modulating the various S oxidation states of the OEC. In PSII from higher plants the environment of YD• radical has been extensively characterized only in spinach (Spinacia oleracea) Mn- depleted non functional PSII membranes. Here, we present a 2D-HYSCORE investigation in functional PSII of spinach to determine the electronic structure of YD• radical. The hyperfine couplings of the protons that interact with the YD• radical are determined and the relevant assignment is provided. A discussion on the similarities and differences between the present results and the results from studies performed in non functional PSII membranes from higher plants and PSII preparations from other organisms is given.

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