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Plasmonic enhancement of photocurrent generation in Photosystem Ia??based hybrid electrode
摘要： We experimentally demonstrate that oriented assembly of red algal photosystem I (PSI) reaction center on a plasmonically active Silver Island Film (SIF) leads to strong enhancement of both fluorescence intensity and photocurrent generated upon illumination. PSI complexes were specifically attached to a monolayer of graphene deposited on the SIF layer. The results of comprehensive fluorescence microscopy point out to the critical role of the SIF layer in enhancing the optical response of PSI, as we observe increased emission intensity. Hence, importantly, the strong increase of photocurrent generation demonstrated for the biohybrid electrodes, can be directly associated with the plasmonic enhancement of optical and electrochemical functionalities of PSI. The results also indicate that the graphene layer is not diminishing the influence of the plasmonic excitations in SIF on the absorption and emission of PSI.
关键词： hybrid electrode,plasmonic enhancement,Photosystem I,graphene,Silver Island Film,photocurrent generation
更新于2025-09-23 15:19:57
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Bio-mimic energy storage system with solar light conversion to hydrogen by combination of photovoltaic devices and electrochemical cells inspired by the antenna-associated photosystem II
摘要： Global warming caused by anthropogenic activity is one of the serious problems today. In order to suppress the global warming, the shift from fossil fuel–based energy source to the nature-oriented sustainable energy is encouraged. In this concept paper, possible biomimetic engineering approach inspired by the efficient and sustainable natural energy utilization in living plants is demonstrated. The focal features in plants include (1) the light-harvesting and energy condensing apparatus, (2) water splitting O2 evolving apparatus, (3) storage of energy-related chemicals, and (4) reversal conversion of storage into the “energy in use” by meeting the demands. Demonstration of solar-driven chemical energy conversion was performed using a system consisted of (i) photovoltaic power-generating device, (ii) an electrochemical unit converting electric power into chemical energy, (iii) storage of H2, and (iv) polymer electrolyte cells converting H2 back to electricity by meeting the demands on site. The present concept paper presenting a technical perspective based on the plant-inspired knowledge (conceptual similarity between natural photosynthesis and solar-to-H2 conversion) is a fruit of interdisciplinary collaboration between the team of chemical energy conversion renown for the world highest record of solar-to-hydrogen conversion efficiency (24.4%, as of 2015) and a group of plant biologists.
关键词： energy system,hydrogen,Photosystem-II,solar light conversion
更新于2025-09-23 15:19:57
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Hydroxyectoine protects Mn-depleted photosystem II against photoinhibition acting as a source of electrons
摘要： In the present study, we have investigated the effect of hydroxyectoine (Ect-OH), a heterocyclic amino acid, on oxygen evolution in photosystem II (PS II) membrane fragments and on photoinhibition of Mn-depleted PS II (apo-WOC-PS II) preparations. The degree of photoinhibition of apo-WOC-PS II preparations was estimated by the loss of the capability of exogenous electron donor (sodium ascorbate) to restore the amplitude of light-induced changes of chlorophyll fluorescence yield (?F). It was found that Ect-OH (i) stimulates the oxygen-evolving activity of PS II, (ii) accelerates the electron transfer from exogenous electron donors (K4[Fe(CN)6], DPC, TMPD, Fe2+, and Mn2+) to the reaction center of apo-WOC-PS II, (iii) enhances the protective effect of exogenous electron donors against donor-side photoinhibition of apo-WOC-PS II preparations. It is assumed that Ect-OH can serve as an artificial electron donor for apo-WOC-PS II, which does not directly interact with either the donor or acceptor side of the reaction center. We suggest that the protein conformation in the presence of Ect-OH, which affects the extent of hydration, becomes favorable for accepting electrons from exogenous donors. To our knowledge, this is the first study dealing with redox activity of Ect-OH towards photosynthetic pigment–protein complexes.
关键词： Hydroxyectoine,Photoinhibition,Photosystem II,Water-oxidizing complex
更新于2025-09-19 17:15:36
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Structure-activity relationships of hierarchical three-dimensional electrodes with photosystem II for semi-artificial photosynthesis
摘要： Semi-artificial photosynthesis integrates photosynthetic enzymes with artificial electronics, which is an emerging approach to reroute the natural photoelectrogenetic pathways for sustainable fuel and chemical synthesis. However, the reduced catalytic activity of enzymes in bioelectrodes limits the overall performance and further applications in fuel production. Here, we show new insights into factors that govern the photoelectrogenesis in a model system consisting of photosystem II and three-dimensional indium tin oxide and graphene electrodes. Fluorescence microscopy and in situ surface-sensitive infrared spectroscopy are employed to probe the enzyme distribution and penetration within electrode scaffolds of different structures, which is further correlated with protein film-photoelectrochemistry to establish relationships between the electrode structure and enzyme activity. We find that the hierarchical structure of electrodes mainly affects the protein integration, but not the enzyme activity. Photoactivity is more limited by light intensity and electronic communication at the biointerface. This study provides guidelines for maximizing the performance of semi-artificial photosynthesis and also presents a set of methodologies to probe the photoactive biofilms in three-dimensional electrodes.
关键词： semi-artificial photosynthesis,Photosystem II,inverse opal,graphene electrode,indium tin oxide electrode
更新于2025-09-19 17:15:36
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An oxyl/oxo mechanism for oxygen-oxygen coupling in PSII revealed by an x-ray free-electron laser
摘要： Photosynthetic water oxidation is catalyzed by the Mn4CaO5 cluster of photosystem II (PSII) with linear progression through five S-state intermediates (S0 to S4). To reveal the mechanism of water oxidation, we analyzed structures of PSII in the S1, S2, and S3 states by x-ray free-electron laser serial crystallography. No insertion of water was found in S2, but flipping of D1 Glu189 upon transition to S3 leads to the opening of a water channel and provides a space for incorporation of an additional oxygen ligand, resulting in an open cubane Mn4CaO6 cluster with an oxyl/oxo bridge. Structural changes of PSII between the different S states reveal cooperative action of substrate water access, proton release, and dioxygen formation in photosynthetic water oxidation.
关键词： oxygen-oxygen coupling,photosystem II,x-ray free-electron laser,water oxidation,oxyl/oxo mechanism
更新于2025-09-19 17:13:59
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Photovoltaic activity of electrodes based on intact photosystem I electrodeposited on bare conducting glass
摘要： We demonstrate photovoltaic activity of electrodes composed of fluorine-doped tin oxide (FTO) conducting glass and a multilayer of trimeric photosystem I (PSI) from cyanobacterium Synechocystis sp. PCC 6803 yielding, at open circuit potential (OCP) of + 100 mV (vs. SHE), internal quantum efficiency of (0.37 ± 0.11)% and photocurrent density of up to (0.5 ± 0.1) μA/cm2. The photocurrent measured for OCP is of cathodic nature meaning that preferentially the electrons are injected from the conducting layer of the FTO glass to the photooxidized PSI primary electron donor, P700+, and further transferred from the photoreduced final electron acceptor of PSI, Fb, via ascorbate electrolyte to the counter electrode. This observation is consistent with preferential donor-side orientation of PSI on FTO imposed by applied electrodeposition. However, by applying high-positive bias (+ 620 mV) to the PSI-FTO electrode, exceeding redox midpoint potential of P700 (+ 450 mV), the photocurrent reverses its orientation and becomes anodic. This is explained by “switching off” the natural photoactivity of PSI particles (by the electrochemical oxidation of P700 to P700+) and “switching on” the anodic photocurrent from PSI antenna Chls prone to photooxidation at high potentials. The efficient control of the P700 redox state (P700 or P700+) by external bias applied to the PSI-FTO electrodes was evidenced by ultrafast transient absorption spectroscopy. The advantage of the presented system is its structural simplicity together with in situ-proven high intactness of the PSI particles.
关键词： Photoelectrochemical measurements,Cyanobacterium Synechocystis sp. PCC 6803,Femtosecond-transient absorption,Photovoltaics,FTO conducting glass,Photosystem I
更新于2025-09-19 17:13:59
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Design and synthesis of benzimidazole phenol-porphyrin dyads for the study of bioinspired photoinduced proton-coupled electron transfer
摘要： Benzimidazole phenol-porphyrin dyads have been synthesized to study proton-coupled electron transfer (PCET) reactions induced by photoexcitation. High-potential porphyrins have been chosen to model P680, the photoactive chlorophyll cluster of photosynthetic photosystem II (PSII). They have either two or three pentafluorophenyl groups at the meso positions to impart the high redox potential. The benzimidazole phenol (BIP) moiety models the Tyrz-His190 pair of PSII, which is a redox mediator that shuttles electrons from the water oxidation catalyst to P680?+. The dyads consisting of a porphyrin and an unsubstituted BIP are designed to study one-electron one-proton transfer (E1PT) processes upon excitation of the porphyrin. When the BIP moiety is substituted with proton-accepting groups such as imines, one-electron two-proton transfer (E2PT) processes are expected to take place upon oxidation of the phenol by the excited state of the porphyrin. The bis-pentafluorophenyl porphyrins linked to BIPs provide platforms for introducing a variety of electron-accepting moieties and/or anchoring groups to attach semiconductor nanoparticles to the macrocycle. The triads thus formed will serve to study the PCET process involving the BIPs when the oxidation of the phenol is achieved by the photochemically produced radical cation of the porphyrin.
关键词： pentafluorophenyl porphyrin,benzimidazole derivatives,proton-coupled electron transfer (PCET),photosystem II
更新于2025-09-11 14:15:04
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Structure of a cyanobacterial photosystem I tetramer revealed by cryo-electron microscopy
摘要： Photosystem I (PSI) functions to harvest light energy for conversion into chemical energy. The organisation of PSI is variable depending on the species of organism. Here we report the structure of a tetrameric PSI core isolated from a cyanobacterium, Anabaena sp. PCC 7120, analysed by single-particle cryo-electron microscopy (cryo-EM) at 3.3 ? resolution. The PSI tetramer has a C2 symmetry and is organised in a dimer of dimers form. The structure reveals interactions at the dimer-dimer interface and the existence of characteristic pigment orientations and inter-pigment distances within the dimer units that are important for unique excitation energy transfer. In particular, characteristic residues of PsaL are identified to be responsible for the formation of the tetramer. Time-resolved fluorescence analyses showed that the PSI tetramer has an enhanced excitation-energy quenching. These structural and spectroscopic findings provide insights into the physiological significance of the PSI tetramer and evolutionary changes of the PSI organisations.
关键词： cyanobacterium,excitation energy transfer,tetramer,Photosystem I,cryo-electron microscopy
更新于2025-09-11 14:15:04
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Reconciling Structural and Spectroscopic Fingerprints of the Oxygen Evolving Complex of Photosystem II: A Computational Study of the S <sub/>2</sub> State
摘要： The catalytic cycle of photosynthetic water oxidation occurs at the Mn4CaO5 oxygen-evolving complex (OEC) of Photosystem II (PSII). Extensive spectroscopic data have been collected on the intermediates, especially the S2 (Kok) state, although the proton and electron inventories (Mn oxidation states) are still uncertain. The “high-oxidation” paradigm, assigns S2 Mn oxidation level (III, IV, IV, IV) or (IV, IV, IV, III), whereas a “low-oxidation” paradigm posits two additional electrons. Here we investigate the geometric (XRD, EXAFS) and spectroscopic (EPR, ENDOR) properties of the S2 state using quantum chemical DFT calculations, focusing on the neglected low paradigm. Two interconvertible electronic spin configurations are predicted as ground states, producing multiline (S = 1/2) and broad (S = 5/2) EPR signals in the low paradigm oxidation state (III, IV, III, III) and with W2 as OH– and O5 as OH–. They have “open” (S = 5/2) and “closed” (S = 1/2) Mn3CaO4-cubane geometries. Other energetically accessible isomers with ground spin states 1/2, 7/2, 9/2, or 11/2 can be obtained through perturbations of hydrogen-bonding networks (e.g. H+ from His337 to O3 or W2), consistent with experimental observations. Conformers with the low oxidation state configuration (III, IV, IV, II) also become energetically accessible when the protonation state is O5 (OH–), W2 (H2O) and neutral His337. The configuration with (III, IV, III, III) agrees well with earlier low temperature EPR and ENDOR interpretations, while the MnII-containing configuration agrees partially with recent ENDOR data. However, the low-oxidation paradigm does not yield isotropic ligand hyperfine interactions in good agreement with observed values. We conclude that the low Mn oxidation state proposal for the OEC can closely fit most of the available structural and electronic data for S2 at accessible energies.
关键词： EPR,low-oxidation paradigm,oxygen-evolving complex,ENDOR,Photosystem II,DFT calculations,S2 state
更新于2025-09-10 09:29:36
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Photoreduction of CO2 with a formate dehydrogenase driven by photosystem II using a semi-artificial Z-scheme architecture
摘要： Solar-driven coupling of water oxidation with CO2 reduction sustains life on our planet and is of high priority to contemporary research. Here, we report a photoelectrochemical tandem device, which performs photocatalytic CO2 reduction to formate. We employ a semi-artificial design, which wires a W-dependent formate dehydrogenase (FDH) cathode to a photoanode containing the photosynthetic water oxidation enzyme, photosystem II, via a synthetic dye with complementary light absorption. From a biological perspective, the system achieves a metabolically-inaccessible pathway of light-driven CO2 fixation to formate. From a synthetic point of view, it represents a proof-of-principle system utilizing precious-metal-free catalysts for selective CO2 to formate conversion using water as an electron donor. This hybrid platform demonstrates the translatability and versatility of coupling abiotic and biotic components to create challenging models for solar fuel and chemical synthesis.
关键词： Photoreduction,formate dehydrogenase,photosystem II,semi-artificial Z-scheme architecture,CO2
更新于2025-09-09 09:28:46