Electron Transport Reactions Research Articles

Electro-responsive Molecularly Imprinted Polymers (E-MIPs) for Rapid Detection of Progesterone in Human Serum Samples.

Rapid and reagent-free detection of progesterone (P4) is crucial in point-of-care (POC) measurement due to its important role in the human endocrine and central nervous system. Currently available technologies for P4 detection are often not rapid or require reagents, limiting their use in POC settings. In this work, a self-signaling electrochemical sensing platform for rapid detection of P4 is developed by using electroactive molecularly imprinted polymers (E-MIPs). E-MIPs possess the ability to transduce the molecular recognition event into a measurable electrochemical signal. The E-MIPs are prepared by bulk copolymerization of acrylic acid (AA) and ferrocenylmethyl methacrylate (FcMA) in the presence of P4 followed by its removal from the polymer matrix. By incorporation of ferrocene moieties, the MIP gains intrinsic electroactivity, enabling label-free and direct electrochemical detection of P4 levels. Electrochemical techniques, including cyclic voltammetry and electrochemical impedance spectroscopy, were employed to elucidate the electron transport reaction responsible for the MIP's intrinsic electroactivity. Additionally, the predetermined complementary binding sites confined to the small working area of the screen-printed carbon electrode (SPCE) within the E-MIP matrix facilitate rapid P4 binding, achieving completion within 120 s. The developed E-MIP sensing platform was used for the rapid detection of P4 levels in human serum samples. The short incubation times reported for the E-MIP sensing platform would be beneficial in minimizing the nonspecific binding in the real-world samples. We believe that the proposed E-MIP sensing platform can be applied to clinical samples for detecting fluctuations in P4 levels.

Photosynthetic performance of the red algae Gracilariopsis lemaneiformis under high seawater pH: Excess reactive oxygen production due to carbon limitation.

The red algae Gracilariopsis lemaneiformis is extensively cultivated at high densities, leading to significant increases in regional seawater pH due to its photosynthetic removal of inorganic carbon. We conducted a study on G. lemaneiformis cultured under various pH conditions (normal pH, pH 9.3, and pH 9.6) and light levels (dark and 100 μmol photons m-2 s-1) to investigate how high pH seawater environments affect the metabolic processes of G. lemaneiformis. The high pH did not directly damage the photosynthetic light reactions or the Calvin cycle. Instead, the observed reduction in photosynthetic rates was primarily due to CO2 limitation. However, under illuminated conditions, a high pH environment leads to a decrease in electron transport efficiency (ETo/RC) and reaction center density (RC/CSo), while simultaneously increasing the levels of hydrogen peroxide (H2O2), malondialdehyde (MDA), and the activity of antioxidant enzymes. Under illuminated conditions, the limitation of inhibit the photosynthetic electron transport process, leading to energy imbalance and excessive production of reactive oxygen species, which in turn resulted in lipid peroxidation of the cell membrane. This might be one of the inducing factors responsible for the bleaching in sea-farmed G. lemaneiformis plants.

Elucidating the Transport of Electrons and Molecules in a Solid Electrolyte Interphase Close to Battery Operation Potentials Using a Four-Electrode-Based Generator-Collector Setup.

In lithium-ion batteries, the solid electrolyte interphase (SEI) passivates the anode against reductive decomposition of the electrolyte but allows for electron transfer reactions between anode and redox shuttle molecules, which are added to the electrolyte as an internal overcharge protection. In order to elucidate the origin of these poorly understood passivation properties of the SEI with regard to different molecules, we used a four-electrode-based generator-collector setup to distinguish between electrolyte reduction current and the redox molecule (ferrocenium ion Fc+) reduction current at an SEI-covered glassy carbon electrode. The experiments were carried out in situ during potentiostatic SEI formation close to battery operation potentials. The measured generator and collector currents were used to calculate passivation factors of the SEI with regard to electrolyte reduction and with regard to Fc+ reduction. These passivation factors show huge differences in their absolute values and in their temporal evolution. By making simple assumptions about molecule transport, electron transport, and charge transfer reaction rates in the SEI, distinct passivation mechanisms are identified, strong indication is found for a transition during SEI growth from redox molecule reduction at the electrode | SEI interface to reduction at the SEI | electrolyte interface, and good estimates for the transport coefficients of both electrons and redox molecules are derived. The approach presented here is applicable to any type of electrochemical interphase and should thus also be of interest for interphase characterization in the fields of electrocatalysis and corrosion.

Update on heme biosynthesis, tissue-specific regulation, heme transport, relation to iron metabolism and cellular energy.

Heme is a primordial macrocycle upon which most aerobic life on Earth depends. It is essential to the survival and health of nearly all cells, functioning as a prosthetic group for oxygen-carrying proteins and enzymes involved in oxidation/reduction and electron transport reactions. Heme is essential for the function of numerous hemoproteins and has numerous other roles in the biochemistry of life. In mammals, heme is synthesised from glycine, succinyl-CoA, and ferrous iron in a series of eight steps. The first and normally rate-controlling step is catalysed by 5-aminolevulinate synthase (ALAS), which has two forms: ALAS1 is the housekeeping form with highly variable expression, depending upon the supply of the end-product heme, which acts to repress its activity; ALAS2 is the erythroid form, which is regulated chiefly by the adequacy of iron for erythroid haemoglobin synthesis. Abnormalities in the several enzymes of the heme synthetic pathway, most of which are inherited partial enzyme deficiencies, give rise to rare diseases called porphyrias. The existence and role of heme importers and exporters in mammals have been debated. Recent evidence established the presence of heme transporters. Such transporters are important for the transfer of heme from mitochondria, where the penultimate and ultimate steps of heme synthesis occur, and for the transfer of heme from cytoplasm to other cellular organelles. Several chaperones of heme and iron are known and important for cell health. Heme and iron, although promoters of oxidative stress and potentially toxic, are essential cofactors for cellular energy production and oxygenation.

Based on N, F, and P co-doping biomass carbon to construct 3D porous carbon coated LiFePO4 for preparing lithium-ion batteries

Because of its superior structural stability, high level of safety, and low cost, the olivine-type LiFePO4 (LFP) is a prevailing cathode material in lithium-ion batteries. However, its development is constrained to inferior electronic conductivity and sluggish diffusion kinetic. In this work, a biomass carbon source derived from microbial residue was introduced to modify LiFePO4 (LFP@NFPC). LFP@NFPC composite with three-dimensional (3D) porous structure was synthesized via a facile wet ball milling and high-temperature calcination. Through well-designed experiment and feasible data analysis, a high conductive 3D network structure is constructed by N, F, and P co-doped carbon coating in the surface of LiFePO4, facilitating fast electron transport and rapid reaction kinetics bewteen intercrystalline. Meanwhile, the LFP@NFPC with three-dimensional (3D) porous structure can also improve the accessibility of Li+ over a protrcated cycle. The as-prepared LFP@NFPC shows discharge specific capacities of 168.2, 138.4, and 103.8 mAh/g at 1, 10, and 50C, respectively. Simultaneously, the LFP@NFPC||Graphite full battery indicates a specific capacity of 161.2 mAh/g at 1C, thus exhibiting superior rate capacity and outstanding cycle stability. This work provides a sustainable and economical approach to modify the cathode material of LIBs.

Divergent Protein Redox Dynamics and Their Relationship with Electron Transport Efficiency during Photosynthesis Induction.

Various chloroplast proteins are activated/deactivated during the light/dark cycle via the redox regulation system. Although the photosynthetic electron transport chain provides reducing power to redox-sensitive proteins via the ferredoxin (Fd)/thioredoxin (Trx) pathway for their enzymatic activity control, how the redox states of individual proteins are linked to electron transport efficiency remains uncharacterized. Here we addressed this subject with a focus on the photosynthetic induction phase. We used Arabidopsis plants, in which the amount of Fd-Trx reductase (FTR), a core component in the Fd/Trx pathway, was genetically altered. Several chloroplast proteins showed different redox shift responses toward low- and high-light treatments. The light-dependent reduction of Calvin-Benson cycle enzymes fructose 1,6-bisphosphatase (FBPase) and sedoheptulose 1,7-bisphosphatase (SBPase) was partially impaired in the FTR-knockdown ftrb mutant. Simultaneous analyses of chlorophyll fluorescence and P700 absorbance change indicated that the induction of the electron transport reactions was delayed in the ftrb mutant. FTR overexpression also mildly affected the reduction patterns of FBPase and SBPase under high-light conditions, which were accompanied by the modification of electron transport properties. Accordingly, the redox states of FBPase and SBPase were linearly correlated with electron transport rates. In contrast, ATP synthase was highly reduced even when electron transport reactions were not fully induced. Furthermore, the redox response of proton gradient regulation 5-like photosynthetic phenotype1 (PGRL1; a protein involved in cyclic electron transport) did not correlate with electron transport rates. Our results provide insights into the working dynamics of the redox regulation system and their differential associations with photosynthetic electron transport efficiency.

Phase‐Bridged Hierarchical Catalysts for Efficient and Stable Water Electrolysis

AbstractThe design and synthesis of low‐cost electrocatalysts with high catalytic activity and long‐term stability is a challenging task. This study utilizes a combination of electronic tuning and surface reconstruction to synthesize a ternary layered double hydroxide (LDH)/phosphide (P−NiCuFe−LDH) hierarchical‐structure catalyst that improves the kinetics of the hydrogen/oxygen evolution reactions in water electrolysis by facilitating the thermodynamically limited reaction pathways. Spectroscopic analyses indicate synergistic electronic interactions among the metal atoms in the LDH and phosphide layers via the P‐bridge effect. This cross‐layer interaction optimizes the electron transport pathways and reaction kinetics, enabling the proposed hierarchical electrocatalyst to exhibit high intrinsic activity. Theoretical calculations confirm the configuration of the cross‐phase bridges and elucidate the origin of the enhanced electrocatalytic effect of P−NiCuFe−LDH. For overall water splitting, the P−NiCuFe0.06−LDH || P−NiCuFe0.06−LDH system requires only 1.517 V to attain a current density of 10 mA cm−2. The P−O‐containing surface (generated in situ during water electrolysis) prevents metal‐ion leaching and endows P−NiCuFe−LDH with excellent operational stability; as demonstrated by the continuous long‐term stability test over 1000 h with negligible performance degradation. This study provides important insights into the design of rational hierarchical structures for a wide range of applications beyond water splitting.

USE OF CYTOKININS AND COMPOSTING TO IMPROVE THE AGRONOMIC AND PHYSIOLOGICAL TRAITS OF CAIGUA (CYCLANTHERA PEDATA L.)

The scarcity of nutrients and synthetic fertilizers reduced crop productivity, increasing production costs and prompting scientists to seek new technologies to ensure high-quality output. In this context, using cytokinins with organic fertilizers ensued to assess their effects on caigua (Cyclanthera pedata L.) production. For this purpose, land preparation for planting comprised two levels of cytokinins (100 and 150 ml, Anthesis Plus per 200 L of water) and organic compost at 10 t/ha, then spread across the land. Results showed that adding cytokinins and compost manure, alone and in combination, significantly improved the agronomic and physiological characteristics of caigua. However, the combined application of compost manure and cytokinins dramatically enriched the caigua plant length, diameter, fruits per plant, and fruit dry and fresh weight per plant up to 85.0%, 46.9%, 81.8%, 80.6%, and 83.2%, respectively, in comparison with the control treatment. Similarly, chlorophyll contents, quantum yield, photosynthetically active radiation, fluorescence yield, and electron transport reaction increased at 68.8%, 66.4%, 79.2%, 51.1%, and 74.0%, respectively, with combined application as compared with control. Furthermore, the co-addition of composting and cytokinins also upgraded the biochemical composition versus the control. The presented results suggested that applying a mixture of compost manure and cytokinins may help enhance caigua plant growth, yield, and quality and improve soil characteristics.

Quantifying the roles of algal photosynthetic electron pathways: a milestone towards photosynthetic robustness.

During photosynthesis, electron transport reactions generate and shuttle reductant to allow CO2 reduction by the Calvin-Benson-Bassham cycle and the formation of biomass building block in the so-called linear electron flow (LEF). However, in nature, environmental parameters like light intensity or CO2 availability can vary and quickly change photosynthesis rates, creating an imbalance between photosynthetic energy production and metabolic needs. In addition to LEF, alternative photosynthetic electron flows are central to allow photosynthetic energy to match metabolic demand in response to environmental variations. Microalgae arguably harbour one of the most diverse set of alternative electron flows (AEFs), including cyclic (CEF), pseudocyclic (PCEF) and chloroplast-to-mitochondria (CMEF) electron flow. While CEF, PCEF and CMEF have large functional overlaps, they differ in the conditions they are active and in their role for photosynthetic energy balance. Here, I review the molecular mechanisms of CEF, PCEF and CMEF in microalgae. I further propose a quantitative framework to compare their key physiological roles and quantify how the photosynthetic energy is partitioned to maintain a balanced energetic status of the cell. Key differences in AEF within the green lineage and the potential of rewiring photosynthetic electrons to enhance plant robustness will be discussed.

MATOQ: a Monte Carlo simulation of electron transport in environmental-friendly gas mixtures for Resistive Plate Chambers

The increasing interest in environmental-friendly gas mixtures for gaseous particle detectors, especially tetrafluoropropene-based gas mixtures for Resistive Plate Chambers (RPCs), has prompted in recent years the need for simulating electron transport coefficients and reaction rates in these mixtures. MATOQ is a Monte Carlo simulation program that calculates electron transport parameters, specifically designed for studying and optimizing environmental-friendly gas mixtures for RPCs. Unlike other existing codes, MATOQ allows for the simulation of electron avalanches by including the effect of space charge electric field, which can significantly impact the avalanche evolution in gaseous detectors such as RPCs. After the validation of the MATOQ simulation in the temporal and spatial growth configurations, we present the electron transport coefficients and the reaction rates in tetrafluoropropene-based gas mixtures, which may represent a valid alternative to the standard gas mixtures currently used for RPCs.

Impact of growth light environment on oxygen sensitivity in rice: Pseudo-first-order response of photosystem I photoinhibition to O2 partial pressure.

Photosynthetic organisms generate reactive oxygen species (ROS) during photosynthetic electron transport reactions on the thylakoid membranes within both photosystems (PSI and PSII), leading to the impairment of photosynthetic activity, known as photoinhibition. In PSI, ROS production has been suggested to follow Michaelis-Menten- or second-order reaction-dependent kinetics in response to changes in the partial pressure of O2 . However, it remains unclear whether ROS-mediated PSI photoinhibition follows the kinetics mentioned above. In this study, we aimed to elucidate the ROS production kinetics from the aspect of PSI photoinhibition in vivo. For this research objective, we investigated the O2 dependence of PSI photoinhibition by examining intact rice leaves grown under varying photon flux densities. Subsequently, we found that the degree of O2 -dependent PSI photoinhibition linearly increased in response to the increase in O2 partial pressure. Furthermore, we observed that the higher photon flux density on plant growth reduced the O2 sensitivity of PSI photoinhibition. Based on the obtained data, we investigated the O2 -dependent kinetics of PSI photoinhibition by model fitting analysis to elucidate the mechanism of PSI photoinhibition in leaves grown under various photon flux densities. Remarkably, we found that the pseudo-first-order reaction formula successfully replicated the O2 -dependent PSI photoinhibition kinetics in intact leaves. These results suggest that ROS production, which triggers PSI photoinhibition, occurs by an electron-leakage reaction from electron carriers within PSI, consistent with previous in vitro studies.

Leaf chlorophyll fluorescence and reflectance of oakleaf lettuce exposed to metal and metal(oid) oxide nanoparticles

BackgroundMost nanoparticles (NPs) have a significant impact on the structure and function of the plant photosynthetic apparatus. However, their spectrum of action varies significantly, from beneficial stimulation to toxicity, depending on the type of NPs, the concentration used and plant genotypic diversity. Photosynthetic performance can be assessed through chlorophyll a fluorescence (ChlF) measurements. These data allow to indirectly obtain detailed information about primary light reactions, thylakoid electron transport reactions, dark enzymatic stroma reactions, slow regulatory processes, processes at the pigment level. It makes possible, together with leaf reflectance performance, to evaluate photosynthesis sensitivity to stress stimuli. ResultsWe investigated effects of different metal and metal(oid) oxide nanoparticles on photosynthesis of oakleaf lettuce seedlings by monitoring the chlorophyll a fluorescence light radiation and reflectance from the leaves. Observations of ChlF parameters and changes in leaf morphology were carried out for 9 days in two-day intervals. Spectrophotometric studies were performed at 9th day. Suspensions of NPs with the following concentrations were used: 6% TiO2, SiO2; 3% CeO2, SnO2, Fe2O3; 0.004% (40 ppm) Ag; 0.002% (20 ppm) Au. Nanoparticles were applied directly on the leaves which caused small symptoms of chlorosis, necrosis and leaf veins deformation, but the plants fully recovered to the initial morphological state at 9th day. Leaf reflectance analysis showed an increase in FRI for SiO2-NPs and CeO2-NPs treatments and ARI2 for Fe2O3, however, WBI and PRI coefficients for the latter nanoparticle were lower than in control. Chlorophyll a fluorescence parameters have changed due to NPs treatment. Fe2O3-NPs caused an increase in Fv/F0, PIABS, ET0/RC, DI0/RC, ABS/RC in different time points in comparison to control, also Ag, Au and SnO2 treatment caused an increase in Fv/F0, PIABS or ET0/RC, respectively. On the other hand, TiO2-NPs caused a decrease in Fv/Fm and Fv/F0 parameters, but an increase in DI0/RC value was observed. SnO2-NPs decreased PIABS, but increased ET0/RC than compared to control. Nanoparticles affected the shape of the O-J-I-P curve in slight manner, however, further analyses showed unfavourable changes within the PSII antenna, manifested by a slowdown in the transport of electrons between the Chl molecules of the light-harvesting complex II and the active center of PSII due to NPs application.ConclusionChanges in ChlF parameters and leaf reflectance values clearly proved the significant influence of NPs on the functioning of the photosynthetic apparatus, especially right after NPs application. The nature of these changes was strictly depended on the type of nanoparticles and sometimes underwent very significant changes over time. The greatest changes in ChlF parameters were caused by Fe2O3 nanoparticles, followed by TiO2-NPs. After slight response of O-J-I-P curves to treatment of the plants with NPs the course of the light phase of photosynthesis stabilized and at 9th day were comparable to the control curve.

Theoretical process for the investigation of dielectric characteristics of F3NO as an alternative gas for SF6

To examine the possibility of using a gas molecule as an SF6 alternative gas, the insulation properties of the molecule must be estimated. In this work, we present a theoretical approach to calculate geometry parameters, electron scattering cross sections, and transport properties of nitrogen fluoride oxide (F3NO), which we have selected as an alternative to SF6. The molecular minimum structure of F3NO was optimized using the ɷB97X-D functional combined with the aug-cc-pVTZ basis set. Using this initial geometry obtained by the molecular structure calculation, the R-matrix calculation was done to obtain the elastic and momentum transfer cross section. The BE-f method was used for electronic excitation cross section. For the ionization cross section, the binary encounter Bethe method was used. From the calculated cross section data, the electron transport coefficients and reaction coefficients were calculated by solving the two-term approximated Boltzmann equation to investigate the discharge and insulation characteristics.

3D space-confined Co0.85Se architecture with effective interfacial stress relaxation as anode material reveals robust and highly loading potassium-ion batteries

Conversion-type transition metal chalcogenide anodes could bring relatively high specific capacity in potassium ion storage due to multiple electron transport reactions, but often accompanying huge volume changes and resulting in low cycle life and rapid capacity fading.While electrode materials are closely packed, the contact at the interface during potassiation/depotassiation is similar to point-to-point contact, generating strong stress to make self-aggregation occur. In this work, we constructed a 3D carbon framework to confine Co0.85Se nanocrystals in three-dimensional space, both fulfilling the requirements of the material's size in the nano-scale and providing the largest contact area for releasing stress. With this optimization, nitrogen-doped carbon confined Co0.85Se nanocrystals (Co0.85Se@NC) reach an ultra-stable cycle life over 4000 times with a specific capacity of 190.9 mA h g−1 at 500 mA g−1 and provide 155.6 mA h g−1 at 10 A g−1 in the rate capability test. It also renders the areal capacity up to 1.03 mA h cm−2 at 500 mA g−1 in the high-mass loading test. Furthermore, based on the finite element analysis, the 3D confinement strategy has the lowest interfacial stress, ensuring Co0.85Se nanocrystals with high structural integrity. This strategy can relieve the stress issue in the conversion-type anode and demonstrate superior electrochemical performance even at high-loading mass electrodes.

Hydrovoltaic effect-enhanced photocatalysis by polyacrylic acid/cobaltous oxide–nitrogen doped carbon system for efficient photocatalytic water splitting

Severe carrier recombination and the slow kinetics of water splitting for photocatalysts hamper their efficient application. Herein, we propose a hydrovoltaic effect-enhanced photocatalytic system in which polyacrylic acid (PAA) and cobaltous oxide (CoO)–nitrogen doped carbon (NC) achieve an enhanced hydrovoltaic effect and CoO–NC acts as a photocatalyst to generate H2 and H2O2 products simultaneously. In this system, called PAA/CoO–NC, the Schottky barrier height between CoO and the NC interface decreases by 33% due to the hydrovoltaic effect. Moreover, the hydrovoltaic effect induced by H+ carrier diffusion in the system generates a strong interaction between H+ ions and the reaction centers of PAA/CoO–NC, improving the kinetics of water splitting in electron transport and species reaction. PAA/CoO–NC exhibits excellent photocatalytic performance, with H2 and H2O2 production rates of 48.4 and 20.4 mmol g−1 h−1, respectively, paving a new way for efficient photocatalyst system construction.

In situ oxidation of ethylene glycol coupled with Bi2O3 epitaxial growth to prepare Bi2O3/BiOCOOH heterojunctions with oxygen vacancies for efficient photocatalytic lignin degradation

Papermaking wastewater has large output and high chemical oxygen demand (COD), which seriously affects the water environment. As a by-product of papermaking industry, lignin is the main contaminant that causes excessive COD value. Bismuth oxide is a potential catalyst for photocatalytic degradation of lignin-contained wastewater because of its high charge conduction performance and light corrosion resistance. However, the high electron-hole recombination rate and poor surface chemical state of pure Bi2O3 seriously hinder the degradation efficiency. Herein, we designed an OV-Bi2O3/BiOCOOH heterojunction with oxygen vacancies and heterojunction coexisting for photocatalytic degradation of lignin. Temperature induced the oxidation of ethylene glycol into formic acid, resulting in the epitaxial growth of Bi2O3 and forming a Bi2O3/BiOCOOH heterojunction. The heterojunction presents a tight interface by sharing the Bi-O tetrahedron, and provides a highway for the charge transfer. Meanwhile, the oxidation of ethylene glycol induces oxygen vacancies (OVs) on Bi2O3/BiOCOOH surface, forming charge trapping centers to promote electron transport and surface reactions. The degradation efficiency of OV-Bi2O3/BiOCOOH is approximately 3 and 16 times that of Bi2O3 and BiOCOOH, respectively. The improvement of photocatalytic performance can be attributed to the synergy of heterojunction and oxygen vacancy, and the stability is attributed to covalent bonds tightly connected.

Quantification of energy-converting protein complexes in plant thylakoid membranes

Knowledge about the exact abundance and ratio of photosynthetic protein complexes in thylakoid membranes is central to understanding structure-function relationships in energy conversion. Recent modeling approaches for studying light harvesting and electron transport reactions rely on quantitative information on the constituent complexes in thylakoid membranes. Over the last decades several quantitative methods have been established and refined, enabling precise stoichiometric information on the five main energy-converting building blocks in the thylakoid membrane: Light-harvesting complex II (LHCII), Photosystem II (PSII), Photosystem I (PSI), cytochrome b6f complex (cyt b6f complex), and ATPase. This paper summarizes a few quantitative spectroscopic and biochemical methods that are currently available for quantification of plant thylakoid protein complexes. Two new methods are presented for quantification of LHCII and the cyt b6f complex, which agree well with established methods. In addition, recent improvements in mass spectrometry (MS) allow deeper compositional information on thylakoid membranes. The comparison between mass spectrometric and more classical protein quantification methods shows similar quantities of complexes, confirming the potential of thylakoid protein complex quantification by MS. The quantitative information on PSII, PSI, and LHCII reveal that about one third of LHCII must be associated with PSI for a balanced light energy absorption by the two photosystems.

The ferredoxin/thioredoxin pathway constitutes an indispensable redox-signaling cascade for light-dependent reduction of chloroplast stromal proteins

To ensure efficient photosynthesis, chloroplast proteins need to be flexibly regulated under fluctuating light conditions. Thiol-based redox regulation plays a key role in reductively activating several chloroplast proteins in a light-dependent manner. The ferredoxin (Fd)/thioredoxin (Trx) pathway has long been recognized as the machinery that transfers reducing power generated by photosynthetic electron transport reactions to redox-sensitive target proteins; however, its biological importance remains unclear, because the complete disruption of the Fd/Trx pathway in plants has been unsuccessful to date. Especially, recent identifications of multiple redox-related factors in chloroplasts, as represented by the NADPH-Trx reductase C, have raised a controversial proposal that other redox pathways work redundantly with the Fd/Trx pathway. To address these issues directly, we used CRISPR/Cas9 gene editing to create Arabidopsis mutant plants in which the activity of the Fd/Trx pathway was completely defective. The mutants generated showed severe growth inhibition. Importantly, these mutants almost entirely lost the ability to reduce several redox-sensitive proteins in chloroplast stroma, including four Calvin-Benson cycle enzymes, NADP-malate dehydrogenase, and Rubisco activase, under light conditions. These striking phenotypes were further accompanied by abnormally developed chloroplasts and a drastic decline in photosynthetic efficiency. These results indicate that the Fd/Trx pathway is indispensable for the light-responsive activation of diverse stromal proteins and photoautotrophic growth of plants. Our data also suggest that the ATP synthase is exceptionally reduced by other pathways in a redundant manner. This study provides an important insight into how the chloroplast redox-regulatory system operates invivo.

A Label-Free Electrochemical Aptasensor Based on Zn/Fe Bimetallic MOF Derived Nanoporous Carbon for Ultra-Sensitive and Selective Determination of Paraquat in Vegetables.

Paraquat (PQ) has high acute toxicity, even at low concentrations. For most people, the main pathway of exposure to PQ is through the diet. Therefore, the development of simple and efficient methods for PQ testing is critical for ensuring food safety. In this study, a new electrochemical detection strategy for paraquat is proposed based on the specific binding of PQ to its nucleic acid aptamer. Firstly, the Zn/Fe bimetallic ZIF derived nanoporous carbon (Zn/Fe-ZIF-NPC) and nickel hexacyanoferrate nanoparticles (NiHCF-NPs) were sequentially modified onto the glassy carbon electrode (GCE). NiHCF-NPs served as the signal probes, while Zn/Fe-ZIF-NPC facilitated electron transfer and effectively enhanced the sensing signal of NiHCF-NPs. Au nanoparticles (AuNPs) were then electrodeposited on the NiHCF-NPs/Zn/Fe-ZIF-NPC/GCE and then the thiolated aptamer was assembled on the AuNPs/NiHCF-NPs/Zn/Fe-ZIF-NPC/GCE via Au-S bonding. When incubated with PQ, the formation of PQ–aptamer complexes delayed the interfacial electron transport reaction of NiHCF-NPs, which caused a decrease in the current signals. As a result, simple and highly sensitive detection of PQ can be readily achieved by detecting the signal changes. A linear range was obtained from 0.001 to 100 mg/L with a detection limit as low as 0.34 μg/L. Due to the recognition specificity of the aptamer to its target molecule, the proposed method has excellent anti-interference ability. The prepared electrochemical aptasensor was successfully used for PQ assay in lettuce, cabbage and agriculture irrigation water samples with recoveries ranging from 96.20% to 104.02%, demonstrating the validity and practicality of the proposed method for PQ detection in real samples.

Molecular, Brownian, kinetic and stochastic models of the processes in photosynthetic membrane of green plants and microalgae.

The paper presents the results of recent work at the Department of Biophysics of the Biological Faculty, Lomonosov Moscow State University on the kinetic and multiparticle modeling of processes in the photosynthetic membrane. The detailed kinetic models and the rule-based kinetic Monte Carlo models allow to reproduce the fluorescence induction curves and redox transformations of the photoactive pigment P700 in the time range from 100ns to dozens of seconds and make it possible to reveal the role of individual carriers in their formation for different types of photosynthetic organisms under different illumination regimes, in the presence of inhibitors, under stress conditions. The fitting of the model curves to the experimental data quantifies the reaction rate constants that cannot be directly measured experimentally, including the non-radiative thermal relaxation reactions. We use the direct multiparticle models to explicitly describe the interactions of mobile photosynthetic carrier proteins with multienzyme complexes both in solution and in the biomembrane interior. An analysis of these models reveals the role of diffusion and electrostatic factors in the regulation of electron transport, the influence of ionic strength and pH of the cellular environment on the rate of electron transport reactions between carrier proteins. To describe the conformational intramolecular processes of formation of the final complex, in which the actual electron transfer occurs, we use the methods of molecular dynamics. The results obtained using kinetic and molecular models supplement our knowledge of the mechanisms of organization of the photosynthetic electron transport processes at the cellular and molecular levels.