Superoxide O2 Research Articles

Cofactor-independent C-C bond cleavage reactions catalyzed by the AlpJ family of oxygenases in atypical angucycline biosynthesis.

Biosynthesis of atypical angucyclines involves unique oxidative B-ring cleavage and rearrangement reactions, which are catalyzed by AlpJ-family oxygenases, including AlpJ, JadG, and GilOII. Prior investigations established the essential requirement for FADH2/FMNH2 as cofactors when utilizing the quinone intermediate dehydrorabelomycin as a substrate. In this study, we unveil a previously unrecognized facet of these enzymes as cofactor-independent oxygenases when employing the hydroquinone intermediate CR1 as a substrate. The enzymes autonomously drive oxidative ring cleavage and rearrangement reactions of CR1, yielding products identical to those observed in cofactor-dependent reactions of AlpJ-family oxygenases. Furthermore, the AlpJ- and JadG-catalyzed reactions of CR1 could be quenched by superoxide dismutase, supporting a catalytic mechanism wherein the substrate CR1 reductively activates molecular oxygen, generating a substrate radical and the superoxide anion O2 •-. Our findings illuminate a substrate-controlled catalytic mechanism of AlpJ-family oxygenases, expanding the realm of cofactor-independent oxygenases. Notably, AlpJ-family oxygenases stand as a pioneering example of enzymes capable of catalyzing oxidative reactions in either an FADH2/FMNH2-dependent or cofactor-independent manner.

A study on the anti-senescent effects of flavones derived from Prinsepia utilis Royle seed residue

Ethnopharmacological relevancePrinsepia utilis Royle, also known as the Anas fruit, is a unique perennial woody oil plant from Yunnan Province, China. In the ancient texts of Dongba sutras and Yunnan Southern Materia Medica, it has been documented that the local Naxi, Tibetan, and Mosuo communities extensively utilize the root and leaf fruits of green thorns for various purposes. These include treating mild-to-moderate specific dermatitis, moisturising the skin, providing protection against UV damage, aiding childbirth in pregnant women, safeguarding stomach health, reducing the risk of arteriosclerosis, and delaying aging. Aim of the studyIn this study, leftover residues from oil extraction were efficiently reused, and flavonoids were identified during subsequent extraction and separation processes. The anti-senescent effects of flavonoids in P. utilis Royle have not been systematically studied. Therefore, the objective of this study was to explore the anti-senescent properties of the flavonoids obtained from P. utilis Royle. MethodsFirst, HPLC and other analytical techniques were used to identify the components of the P. utilis Royle flavonoid (PURF). Next, DPPH, hydroxyl radicals, superoxide anion O2−, collagenase, and elastase were initially detected using in vitro biochemical assays. To examine its antioxidant properties, a zebrafish model was used, and to confirm its anti-senescent effects, a d-galactose-induced mouse aging model was employed. The anti-senescent mechanism of PURF was examined using a natural senescence HFF model. Furthermore, the anti-senescent target was confirmed using a 3D full T-Skin™ model. ResultsIn vitro biochemical assays demonstrated that flavones exhibited potent antioxidant activity and anti-senescent potential by inhibiting DPPH, hydroxyl radicals, superoxide anion O2−, collagenase, and elastase. It significantly enhanced the antioxidant effect on zebrafish while suppressing ROS and inflammatory injury, up-regulating COL1A1, COL3A1, AMPK, and mTOR gene expression and down-regulating MMP-9, TGF-β, p21, and p16 gene expression suggesting its potential anti-senescent ability. Findings from the D-galactose-induced aging mouse model showed that PURF greatly increased SOD levels, while simultaneously decreasing HYP and MDA levels. In addition, when PURF was given to the HFF cell and 3D full T-Skin™ model, consistent trends were observed in gene and protein expression, with up-regulation of COL1A1, COL3A1, AMPK, and mTOR genes and down-regulation of TGF-β, MMP-1, MMP-9, p21, and p16 genes. Therefore, these preliminary findings indicate that flavones can modulate AMPK/mTOR/TGF-β signalling pathways to exert its influence. ConclusionThe kernel residue of natural P. utilis Royle oil extracted from Yunnan province was previously considered agricultural waste, but we successfully extracted and isolated its flavonoid components. Our preliminary studies demonstrated its potential as an environmentally friendly anti-senescent raw material.

Design of Bismuth Tungstate Bi2WO6 Photocatalyst for Enhanced and Environmentally Friendly Organic Pollutant Degradation.

In this study, a chemical precipitation approach was adopted to produce a photocatalyst based on bismuth tungstate Bi2WO6 for enhanced and environmentally friendly organic pollutant degradation. Various tools such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), optical spectroscopy and X-ray photoelectron spectroscopy, were employed to assess the structural and morphological properties. Hence, the XRD profiles showed a well crystallized Bi2WO6 orthorhombic phase. The photocatalytic performance of the resulting photocatalyst was assessed by the decomposition of Rhodamine B (RhB) and methyl orange (MO) with a decomposition efficiency of 97 and 92%, along with the highest chemical oxygen demand of 82 and 79% during 120 min of illumination, respectively. The principal novelty of the present work is to focus on the changes in the crystalline structure, the morphology, and the optical and the photoelectrochemical characteristics of the Bi2WO6, by tuning the annealing temperature of the designed photocatalyst. Such physicochemical property changes in the as-prepared photocatalyst will affect in turn its photocatalytic activity toward the organic pollutant decomposition. The photocatalytic mechanism was elaborated based on electrochemical impedance spectroscopy, photocurrent analysis, photoluminescence spectroscopy, and radical trapping measurements. The overall data indicate that the superoxide O2•- and holes h+ are the principal species responsible for the pollutant photodegradation.

Sub-picosecond photodynamics of small neutral copper oxide clusters.

The ultrafast dynamics of neutral copper oxide clusters (CunOx, n < 5) are reported using femtosecond pump probe spectroscopy in the gas phase. The transient spectra recorded for each cluster demonstrate they relax on a 100s of fs timescale followed by a long-lived (>50 ps) response. Density functional theory calculations are performed to determine the lowest energy structures and spin states. Topological descripters for the excited states are calculated (time-dependent density functional theory) to relate the measured excited state dynamics to changes in the cluster's electronic structure with increasing oxidation. Strong field ionization is demonstrated here to be a soft form of ionization and able to record transient signals for clusters previously determined to be unstable to nanosecond multiphoton ionization. The relative cluster stability is further demonstrated by signal enhancement/depreciation that is recorded through the synergy from the two laser pulses. Once the oxygen atoms exceed the number of copper atoms, a weakly bound superoxide O2 unit forms, exhibiting a higher spin state. All clusters that are not in the lowest spin configuration demonstrate fragmentation.

Efficient and green oxidation of 2-aminophenol catalyzed by tetra-(p-methoxyphenyl) porphyrin complexes anchored on chitosan in bicarbonate solution

The study explored the catalytic activities of chitosan-supported tetra (p-methoxyphenyl) porphyrin complexes 1–3 in the heterogeneous activation of the aerobic oxidation dimerization of 2-aminophenol (OAP) to 2-aminophenoxazine-3-one (APX) in the presence of bicarbonate, simulating the function of phenoxazinone enzyme synthase. The oxidation reaction was followed by recording the UV–vis spectra of the reaction mixture with time at λmax 433 nm. All chitosan-supported metalloporphyrin complexes 1–3 exhibited effective catalytic activities for OAP oxidation. Under optimal conditions, the chitosan-supported Cu(II) (Tp-OCH3PP) complex displayed the highest catalytic efficiency. Various parameters influencing the catalytic activity of Cu(II) (Tp-OCH3PP)/CTS 1 were studied. The observed rate constant of OAP oxidation exhibited a direct correlation with the concentration of supported catalyst 1 and followed Michaelis–Menten kinetics, indicating saturation of catalyst sites with increasing OAP concentration. The study investigated the impact of temperature, bicarbonate concentration, dissolved oxygen, and the reaction mechanism. Oxidation reaction of OAP catalyzed by 1 in the presence of nitro blue tetrazolium (NTB) revealed no superoxide anion O2−• was formed as a reactive species during the reaction. The chitosan-supported Cu(II) (Tp-OCH3PP) complex shows high catalytic stability and no significant changes up to the fifth run.

Long-Time Oxygen and Superoxide Localization in Arabidopsis thaliana Cryptochrome.

Cryptochromes are proteins that are highly conserved across species and in many instances bind the flavin adenine dinucleotide (FAD) cofactor within their photolyase-homology region (PHR) domain. The FAD cofactor has multiple redox states that help catalyze reactions, and absorbs photons at about 450 nm, a feature linked to the light-related functions of cryptochrome proteins. Reactive oxygen species (ROS) are produced from redox reactions involving molecular oxygen and are involved in a myriad of biological processes. Superoxide O2•- is an exemplary ROS that may be formed through electron transfer from FAD to O2, generating an electron radical pair. Although the formation of a superoxide-FAD radical pair has been speculated, it is still unclear if the required process steps could be realized in cryptochrome. Here, we present results from molecular dynamics (MD) simulations of oxygen interacting with the PHR domain of Arabidopsis thaliana cryptochrome 1 (AtCRY1). Using MD simulation trajectories, oxygen binding locations are characterized through both the O2-FAD intermolecular distance and the local protein environment. Oxygen unbinding times are characterized through replica simulations of the bound oxygen. Simulations reveal that oxygen molecules can localize at certain sites within the cryptochrome protein for tens of nanoseconds, and superoxide molecules can localize for significantly longer. This relatively long-duration molecule binding suggests the possibility of an electron-transfer reaction leading to superoxide formation. Estimates of electron-transfer rates using the Marcus theory are performed for the identified potential binding sites. Molecular oxygen binding results are compared with recent results demonstrating long-time oxygen binding within the electron-transfer flavoprotein (ETF), another FAD binding protein.

Reactive oxygen species production by photoexcited (CuInS2)x(ZnS)1-x quantum dots and their phototoxicity towards Staphylococcus aureus bacteria

The photoproduction of reactive oxygen species (ROS) by semiconductor nanocrystals is of high interest for biological and environmental applications. Herein, water-dispersible 3-mercaptopropionic (MPA)-capped (CuInS2)x(ZnS)1-x quantum dots (ZCIS@MPA QDs) were prepared from dodecanethiol-capped ZCIS QDs by a ligand exchange and their photoreactivity was evaluated. By combining colorimetric and fluorescent probes with electron spin resonance (ESR) measurements, we showed that ZCIS@MPA QDs can photogenerate ROS like hydroxyl ●OH and superoxide O2●- radicals and singlet oxygen 1O2 that alter the MPA ligand and participate in photoluminescence quenching. The phototoxicity of ZCIS@MPA QDs against S. aureus bacteria and the inhibition of the cell growth on a surface were further investigated. These deleterious effects of ROS photoproduced by ZCIS@MPA QDs could significantly be reduced by coupling the antioxidant glutathione peptide with the QDs. Our findings enrich the understanding of photochemical reactions mediated by ZCIS@MPA QDs but also provide new pathways for ROS production, even under ambient light, that may be valuable for antibacterial applications like surface disinfection.

Mitochondria-specific near-infrared photoactivation of peroxynitrite upconversion luminescent nanogenerator for precision cancer gas therapy

Gas therapy is emerging as a highly promising therapeutic strategy for cancer treatment. However, there are limitations, including the lack of targeted subcellular organelle accuracy and spatiotemporal release precision, associated with gas therapy. In this study, we developed a series of photoactivatable nitric oxide (NO) donors NRh-R-NO (R = Me, Et, Bn, iPr, and Ph) based on an N-nitrosated upconversion luminescent rhodamine scaffold. Under the irradiation of 808 nm light, only NRh-Ph-NO could effectively release NO and NRh-Ph with a significant turn-on frequency upconversion luminescence (FUCL) signal at 740 nm, ascribed to lower N–N bond dissociation energy. We also investigated the involved multistage near-infrared-controlled cascade release of gas therapy, including the NO released from NRh-Ph-NO along with one NRh-Ph molecule generation, the superoxide anion O2⋅− produced by the photodynamic therapy (PDT) effect of NRh-Ph, and highly toxic peroxynitrite anion (ONOO‒) generated from the co-existence of NO and O2⋅−. After mild nano-modification, the nanogenerator (NRh-Ph-NO NPs) empowered with superior biocompatibility could target mitochondria. Under an 808 nm laser irradiation, NRh-Ph-NO NPs could induce NO/ROS to generate RNS, causing a decrease in the mitochondrial membrane potential and initiating apoptosis by caspase-3 activation, which further induced tumor immunogenic cell death (ICD). In vivo therapeutic results of NRh-Ph-NO NPs showed augmented RNS-potentiated gas therapy, demonstrating excellent biocompatibility and effective tumor inhibition guided by real-time FUCL imaging. Collectively, this versatile strategy defines the targeted RNS-mediated cancer therapy.

Nonhost Resistance of Thinopyrum ponticum to Puccinia graminis f. sp. tritici and the Effects of the Sr24, Sr25, and Sr26 Genes Introgressed to Wheat

The damage to wheat crops by stem rust poses a threat to the food security of the world’s population. The species Thinopyrum ponticum (Podpěra, 1902) (Z.-W. Liu and R.-C. Wang, 1993) is a non-host for the stem rust fungus Puccinia graminis f. sp. tritici Eriks. and Henn. (Pgt). The Sr24, Sr25, and Sr26 genes, transferred from the Th. ponticum to the wheat gene pool, protect cultivars from the disease in different regions of the world. The study of the non-host resistance (NHR) of Th. ponticum and the effects of the introgressed Sr24, Sr25, and Sr26 genes in wheat is important for breeding cultivars with durable resistance to stem rust. The aim of the research is to study the interaction of Pgt with Th. ponticum and common wheat lines with the Sr24, Sr25, and Sr26 genes, in addition to determining the role of ROS in resistance. Wheat lines with Sr24, Sr25, and Sr26 were resistant to the West Siberian Pgt population. Using cytological methods, it was found that the NHR of Th. ponticum and Sr24, Sr25, and Sr26 led to inhibition of the most inoculumdevelopment on the plant surface. This was mainly due to the suppression of the appressoria development and their death at the stage of penetration into the stomata. Upon contact of Pgt appressoria with stomatal guard cells, the generation of the superoxide anion O2•− was revealed. This interaction is similar to the stomatal immunity of Arabidopsis thaliana to non-pathogenic bacteria. The results of our studies show that the Sr24, Sr25, and Sr26 genes reproduce the action of some NHR mechanisms in wheat.

Computational Modeling of the Interaction of Molecular Oxygen with the miniSOG Protein—A Light Induced Source of Singlet Oxygen

Interaction of molecular oxygen 3O2 with the flavin-dependent protein miniSOG after light illumination results in creation of singlet oxygen 1O2 and superoxide O2●−. Despite the recently resolved crystal structures of miniSOG variants, oxygen-binding sites near the flavin chromophore are poorly characterized. We report the results of computational studies of the protein−oxygen systems using molecular dynamics (MD) simulations with force-field interaction potentials and quantum mechanics/molecular mechanics (QM/MM) potentials for the original miniSOG and the mutated protein. We found several oxygen-binding pockets and pointed out possible tunnels bridging the bulk solvent and the isoalloxazine ring of the chromophore. These findings provide an essential step toward understanding photophysical properties of miniSOG—an important singlet oxygen photosensitizer.

Methylcyclopropene treatment retards the yellowing in pak choi (Brassica rapa subsp. Chinensis) through modulating the programmed cell death during storage at 20°C

The deterioration of post-harvest quality in plants has been shown to be connected with the occurrence of programmed cell death (PCD). Our previous research indicated that 5 μL L−1 1-Methylcyclopropene (1-MCP) delays the yellowing of post-harvest pak choi leaves. However, whether 1-MCP alleviates pak choi yellowing through regulating PCD process, and the regulatory mechanism of 1-MCP on PCD are still unclear. Results showed that 5 μL L−1 1-MCP could retard the PCD process of pak choi as proved by the maintenance of lower cytochrome C content and caspase-3 activity. The results of cell mortality and trypan blue staining further confirmed this view. Forty-five differentially expressed genes (DEGs) involving PCD of pak choi were identified in the transcriptome data. The treatment suppressed the over-accumulation of reactive oxygen species (ROS) (superoxide anion O2·− and hydrogen peroxide H2O2), lipid membrane oxidation, ethylene production, and expression of their related genes (BcRBOHC, BcRBOHD, BcLOX1/3/5, BcACO, BcACO4 and BcEIN3)) during senescence. This relationship was also connected to the preservation of higher level in antioxidant capacity of antioxidase and antioxidants (ascorbate-glutathione (AsA-GSH)), as well as high expression of their related genes (BcSOD, BcAPX, and BcGR) in 1-MCP-treated pak choi. Moreover, 1-MCP down-regulated the transcript of genes involved in PCD, regulated the expression of genes associated with mitochondrial membrane transport, respiration and signaling, and chloroplast membrane transport and REDOX, thereby contributing to the inhibition of PCD. The correlation analysis revealed that pak choi yellowing was positively related with the process of PCD. Taken together, the present study indicated that 1-MCP could delay the yellowing of pak choi through mitigating PCD process, involving the regulation of ROS metabolism, membrane lipid degradation, antioxidant status and ethylene production.

Superoxide Anion Chemistry-Its Role at the Core of the Innate Immunity.

Classically, superoxide anion O2•- and reactive oxygen species ROS play a dual role. At the physiological balance level, they are a by-product of O2 reduction, necessary for cell signalling, and at the pathological level they are considered harmful, as they can induce disease and apoptosis, necrosis, ferroptosis, pyroptosis and autophagic cell death. This revision focuses on understanding the main characteristics of the superoxide O2•-, its generation pathways, the biomolecules it oxidizes and how it may contribute to their modification and toxicity. The role of superoxide dismutase, the enzyme responsible for the removal of most of the superoxide produced in living organisms, is studied. At the same time, the toxicity induced by superoxide and derived radicals is beneficial in the oxidative death of microbial pathogens, which are subsequently engulfed by specialized immune cells, such as neutrophils or macrophages, during the activation of innate immunity. Ultimately, this review describes in some depth the chemistry related to O2•- and how it is harnessed by the innate immune system to produce lysis of microbial agents.

Enhancement of oxygen vacancy sites of La2-xMxCe2O7-δ (M = Ca, Ba, Sr) catalyst for the low temperature oxidative coupling of Methane: A combined DFT and experimental study

This study investigated the effect of different alkaline earth metals doped La2-xMxCe2O7-δ (M = Ca, Sr, Ba and x = 0.30) catalysts prepared by one-step hydrothermal method for the low-temperature methane oxidative coupling (OCM) to olefins. The presence of a disordered cubic fluorite phase of synthesized catalysts was detected by powder XRD and Raman analysis. The surface analysis by XPS and Raman shows the presence of oxygen vacancy sites, which are responsible for the formation of electrophilic superoxide O2– species in presence of molecular oxygen. We observed that the ratio of active oxygen species (O2− and O22−) to lattice oxygen (O2–) was linearly correlated with the number of basic sites. The catalytic activity of different catalysts for the OCM reactions follows the order: La1.7Ca0.3Ce2O7-δ > La1.7Sr0.3Ce2O7-δ > La1.7Ba0.3Ce2O7-δ > La2Ce2O7. The reactivity order follows the same trend as the amount of basic sites and reactive oxygen species. According to this study, the best catalyst is La1.7Ca0.3Ce2O7-δ, which gives the highest C2 yield and C2 selectivity of 23.6 % and 78.8 %, respectively, at 650 °C. DFT studies revealed that substitution of La by Ca in the La2Ce2O7 catalyst significantly reduces the oxygen vacancy formation energy by about 100 kJ/mol compared to the undoped LaCe-oxide. We believe that the superior activity of La1.7Ca0.3Ce2O7-δ catalyst is attributed to the higher amount of basicity and electrophilic oxygen content, which are the governing factors in OCM for CH4 conversion and C2 product selectivity as well.

PS-BPB01-6: PROTECTIVE NOX4 EFFECT IN ENDOTHELIAL CELLS INVOLVES ACTIVATION OF TRANSIENT RECEPTOR POTENTIAL MELASTATIN 2 (TRPM2) CATION CHANNEL

Objective: In endothelial cells, Nox4 is the most prevalent isoform and, in contrast to other Noxes, which generate superoxide O2, Nox4 produces mainly H2O2. Low H2O2 levels have been described to lower blood pressure, which suggests that a certain level of reactive oxygen species (ROS) can have protective effects on the cardiovascular system. We demonstrated that TRPM2 is a target of H2O2 in vascular cells. TRPM2 is a redox-sensitive Ca2+ channel and once activated leads to Ca2 influx. Endothelial dysfunction involves a reduction in eNOS activation by Ca2+ and is potentiated in the absence of Nox4. As TRPM2 channel is a H2O2 sensor and regulates Ca2+ entry, we questioned whether protective Nox4 effect in endothelial cells involves the H2O2-TRPM2-Ca2+ axis, with consequent regulation of NO signalling. Design and Methods: WT and TTRhRen hypertensive mice were crossed with Nox4 KO mice. Vascular function was measured by wire myograph in resistance arteries. ROS and H2O2 generation were assessed by lucigenin and amplex red, and Ca2+ influx by fluorescence microscopy in rat aortic endothelial cells (RAEC). eNOS activation was assessed by immunoblotting. Results: Blood pressure was significantly increased in TTRhRen (130.3 ± 7.0 mmHg) and TTRhRen/Nox4 KO mice (141.3 ± 18 mmHg) versus control mice (98.1 ± 8.0 mmHg). TTRhRen mice had reduced endothelium-dependent relaxation (Emax: WT 83.5 ± 4.03 vs TTRhRen 59.1 ± 3.5); an effect worsened by Nox4 KO (37.9 ± 5.4), p &lt; 0.05. The TRPM2 activator, ADPR, improved vascular relaxation in TTRhRen/Nox4 KO mice (75.9 ± 7.7); an effect recapitulated by H2O2 (74.2 ± 15.4), p &lt; 0.05. Ang II-induced ROS and H2O2 generation in RAEC, effect reversed by Nox4 siRNA and followed by increased Ca2+ influx (AUC - Ca2+: 20440.3333 ± 1870.9), important in eNOS activation. Ang II-induced Ca2+ influx in endothelial cells was reduced by TRPM2 siRNA, TRPM2 inhibitors (AUC - Ca2+: 8-br-cADPR 15232.2 ± 1052.1; Olaparib 14952.6 ± 843.2 and 2-APB 13270.8333 ± 277.4, p &lt; 0.05) and by Nox4 siRNA and Nox4 inhibitor GKT137831 (AUC - Ca2+: GKT 15067.5 ± 255.6). Ang II-induced eNOS activation (Ser1177) (%: 72.3 ± 24.7) and NO release were blocked by Nox4 and TRPM2 sirNA, GKT137831, PEG-catalase and the TRPM2 inhibitor 8-br-cADPR (p &lt; 0.05). Conclusions: We defined a novel molecular pathway in endothelial cells, where Nox4-induced H2O2 production activates PARP/TRPM2 signalling followed by Ca2+ influx, eNOS activation and NO release. The absence of Nox4 impairs Ca2+ homeostasis leading to endothelial dysfunction, an effect exacerbated in hypertension. The protective role of Nox4 corroborates the idea that the use of antioxidants based on the sole evidence that decreased oxidative stress is cardioprotective, it is not effective.

Exogenous melatonin ameliorates yellowing of postharvest pak choi (Brassica rapa subsp. chinensis) by modulating chlorophyll catabolism and antioxidant system during storage at 20 °C

The objective of this study was to investigate the regulatory mechanism of melatonin (MT) treatment on leaf yellowing of pak choi during storage at 20 °C. Results showed that 500 μmoL L−1 MT alleviated the yellowing process of pak choi as proved by the maintenance of high level of leaf colour, chlorophyll content and chlorophyll fluorescence parameters (Fo, Fm and Fv/Fm), and the market life of pak choi was extended by 2 d compared to the control. The weight loss and respiration rate were effectively alleviated by MT treatment. MT treatment restrained chlorophyll breakdown by down-regulating the activity of chlorophyll-degrading enzymes (chlorophyllase CLH, pheophytinase PPH and Mg-dechelatase MDS) and expression of their related genes (BcCLH, BcPPH1/2, BcSGR, BcHCAR, BcNYC1 and BcCAO). Meanwhile, MT suppressed the over-accumulation of reactive oxygen species (ROS) (superoxide anion O2·− and hydrogen peroxide H2O2), and lipid membrane oxidation and associated gene (BcLOX) expression during senescence, thus helping to keep green colour of pak choi. This relationship was also connected to the maintenance of higher level in antioxidant ability of antioxidase (superoxide dismutase SOD, ascorbate peroxidase APX, peroxidase POD and catalase CAT) and antioxidants (ascorbate-glutathione (AsA-GSH)), as well as high expression of their related genes (BcSOD, BcPOD, BcCAT, BcGPX and BcAPX) in pak choi treated with MT. In conclusion, these findings suggested that MT could delay the yellowing of pak choi, involving the regulation of chlorophyll metabolism, ROS metabolism, membrane lipid degradation, and antioxidant capacity. The results provide a possible target for delaying the yellowing of green vegetables.

Coexpression modules constructed identifies regulation pathways of winter jujube (Ziziphus jujuba Mill. 'Dongzao') following postharvest treatment with ozone

Winter jujube (Ziziphus jujuba Mill. 'Dongzao') is a member of the Rhamnaceae family known for its favorable nutritional and flavor profile. It has been considered a unique and excellent cultivar in China. Nevertheless, fresh winter jujube fruit is sensitive to diseases because of microbial decay and mechanical damage. Ozone treatment (OT) is reported to prevent fruit decay in many fruit during postharvest storage. In the present study, we first found that postharvest winter jujube fruit treated with 2.14 mg m −3 ozone concentration exhibited decreased accumulation of superoxide anion O2− generation rate, H2O2 content and MDA content and increased activities of aseorbate peroxidase (APX), catalase(CAT), peroxidase (POD), superoxide dismutase (SOD) and GSH content in the antioxidant bioactive compounds or enzymes, which was beneficial to the enhancement of antioxidant capacity over the entire storage period compared with the other three groups. Then, label-free quantification proteomics and weighted gene coexpression network analysis (WGCNA) of winter jujube fruit revealed black module (containing 94 differentially expressed proteins with increased and decreased levels of abundance respectively) was of greatest importance to study mechanisms of ozone preservation on winter jujube. Gene Ontology (GO) and KEGG annotation and enrichment analysis showed that the black module included ribosomal and glutathione metabolism pathways, suggesting the involvement of these pathways in ozone-mediated antisenescence. There are 26 hub proteins in the black module, and 6 intersecting proteins through protein–protein interaction (PPI) network analysis and KEGG annotation and enrichment analysis, a 60 S acidic ribosomal protein P2B, a 60 S ribosomal protein L12, a 40 S ribosomal protein S19–3, and a phospholipid hydroperoxide glutathione peroxidase, and others. Our qRT-PCR results were consistent with the RNA sequencing results, confirming our findings. We propose a link between protein profiles and physiological traits important for preservation, which identified the WGCNA modules, the hub proteins, and the important pathways, and provided new insights into the molecular mechanisms of OT as the method of storage and preservation of fresh fruit at the proteomic level.

Correlation between Photocatalytic Properties of ZnO and Generation of Hydrogen Peroxide—Impact of Composite ZnO/TiO2 Rutile and Anatase

The generation of hydrogen peroxide on commercial and synthesized ZnO from different precursors was studied using two model molecules, formic acid (FA) and phenol (Ph), as well as phenolic intermediates, hydroquinone (HQ), benzoquinone (BQ), and catechol (CAT). The samples were characterized using X-ray Diffraction (XRD), Transmission Electronic Microscopy (TEM), RAMAN, and Electron Paramagnetic Resonance (EPR) before evaluating their photocatalytic properties. We found that the improved efficiency is accompanied by a high level of H2O2 production, fewer oxygen vacancies, and that the number of moles of H2O2 formed per number of carbon atoms removed is similar to the degradation of FA and Ph with a factor of 1. Moreover, a comparative study on the formation of H2O2 was carried out in the presence of TiO2 rutile and TiO2 anatase, with commercial ZnO. Our results exhibit the impact of the presence of TiO2 on the decomposition of hydrogen peroxide and the formation of phenolic intermediates, which are much lower than those of ZnO only, which is in agreement with the formation of hydroxyl radicals °OH and superoxide O2°− degrading significantly hydroquinone (HQ), benzoquinone (BQ), and cathecol (CAT).

On the Problem of Optimal Microbiological Decontamination of Air Environment and Surfaces

Modern civilization, providing economic and social progress, at the same time objectively creates—sometimes close to ideal—conditions for the spread of various infections. The catastrophic consequences of the SARS-CoV-2 pandemic clearly indicate that homo sapiens appeared to be unable to effectively resist the onslaught of the coronavirus. The purpose of this publication is an attempt to fill the gap in the development of effective methods and means for microbiological decontamination that are optimal in terms of critical parameters. The observational data indicate that a significant number of SARS-CoV-2 coronavirus infections occur by air without a direct contact with the source, including over a long time interval. Precipitation helps to cleanse the air from pollutants and viruses, reducing noncontact contamination, which additionally brings up to date the problem of optimal microbiological decontamination of the air environment and surfaces. A thermodynamic approach has been used to optimize microbiological sterilization. It is shown that irreversible chemical oxidation reactions are the shortest way to achieve sterility, and they are capable of providing high reliability of decontamination. It has been established that oxygen is an optimal oxidant, including from the point of view of ecology, since its reactive forms harmoniously fit into natural exchange cycles. The optimal method for obtaining reactive oxygen species for disinfection is the use of low-temperature (“cold”) plasma, which provides the energy-efficient generation of oxidative reactive forms: atomic oxygen (O), ozone (O3), hydroxyl radical (•OH), hydrogen peroxide (H2O2), superoxide ({text{O}}_{2}^{ - }), and singlet oxygen O2(a1Δg). Due to a short lifetime for most of the above forms outside the plasma applicator, objects remote from the plasma generator should be sterilized with ozone (O3), the minimum lifetime of which is quite long. It has been substantiated that the microwave method of generating oxygen plasma is optimal for energy-efficient ozone production. A modular principle of generation is proposed for varying the productivity of ozone-generating units over a wide range. The module has been developed on the basis of an adapted serial microwave oven, in which a non-self-sustaining microwave discharge is maintained thanks to ionizers (igniters), including those based on radiating radionuclides-emitters. In case of massive contamination of surfaces, it is advisable—in addition to ozone (O3) air disinfecting—to use aqueous solutions of hydrogen peroxide (H2O2). It is essential that these reactive oxygen species for disinfecting objects remote from the plasma generator are highly efficient and, at the same time, environmentally neutral. Reliable and affordable personal protective equipment is proposed for activities in zones of increased ozone concentration. The considered optimal means of disinfection can be applicable not only in medicine but also adapted for numerous practices in agriculture, industry, and everyday life.

Plasmonic effect and bandgap tailoring of Ag/Ag2S doped on ZnO nanocomposites for enhanced visible-light photocatalysis

Ag/Ag2S-ZnO nanocomposites were prepared via a simple hydrothermal process followed by a plasmonic Ag+ reduction through a photo-deposition method. Ag2S was introduced to narrow the overall composite bandgap and activate the surface plasmon resonance (SPR) effect of the Ag+ cation present. The physicochemical properties of the as-synthesised catalysts were characterised by X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM and TEM), Brunauer-Emmett-Teller (BET) analysis. Fourier-transform infrared spectroscopy (FTIR), Ultraviolet diffuse reflectance spectroscopy (UV–vis DRS), photoluminescence emission spectra (PL) and X-ray photoelectron spectroscopy (XPS) was conducted to investigate the photo-absorption and emission spectra of the nanocomposites. The degradation efficiency of all the synthesised catalysts (ZnO, Ag2S, Ag/ZnO and Ag2S/ZnO) prior to the final product, Ag/Ag2S/ZnO was tested and compared. Results showed that the ternary Ag/Ag2S/ZnO achieved a 98 % phenol removal compared to 50 %, 11 %, 64 % and 93 % for ZnO, Ag2S, Ag/ZnO and binary Ag2S/ZnO, respectively. The degradation kinetics followed the Langmuir-Hinshelwood model, which typically describes heterogeneous photocatalytic surface reactions. The linear fits had R2 values higher than 0.97, which confirms the degree of accuracy or statistical fitness to the kinetic model. Degradation scavenger test confirmed the holes (h+) as the main inhibitor and identified the superoxide O2•¯ radical as the main active specie responsible for the degradation. Total organic carbon analysis using the ternary Ag/Ag2S-ZnO catalyst only achieved a 74% phenol mineralization after 24 h of photocatalysis. Recyclability tests showed good phenol removal stability of Ag/Ag2S-ZnO at 41 % after five recycle runs. Hence, a synergistic degradation mechanism responsible for the efficient photo-degradation performance was proposed.

S-scheme ZIF-8/Ag2S heterojunction photocatalyst for degradation of organic pollutant using batch and external loop airlift reactors

The photocatalytic degradation of Rh.B was investigated using ZIF-8/Ag2S nanocomposite photocatalyst. In the present study, Ag2S NPs were dispersed on the surface of ZIF-8 forming a kind of a new high-efficiency heterogeneous photocatalyst ZIF-8/Ag2S nanocomposite via co-precipitation method. The crystal structure, optical properties and the morphology of ZIF-8, Ag2S and ZIF-8/Ag2S synthesized photocatalysts were examined using N2 adsorption–desorption, XRD, DRS, FE-SEM and TEM techniques.The degradation of Rh.B was performed under irradiation of visible light to examine the performance of ZIF-8/Ag2S nanocomposite in batch and external loop airlift reactors. The results demonstrated that the ZIF-8/Ag2S has excellent photodegradation efficiency (100%) compared with pure ZIF-8 (51.6%) and Ag2S (39.7%) due to the good dispersion of agglomerate Ag2S on the surface area of ZIF-8.Moreover, the photodegradation efficiency of Rh.B using ZIF-8/Ag2S nanocomposite photocatalyst in the external loop airlift reactor was more efficient and rapid (100% degradation efficiency within 75 min) than batch reactor (100% degradation efficiency within 120 min). This is due to the well mixing and the effect of the air flow rate containing O2 which greatly improved the photocatalytic activity by reacting with the electrons to produce the superoxide anions O2− in the airlift reactor. Also, the obtained findings from the airlift reactor showed a significant increase in the degradation efficiency with air flow rate up to 40 LPM, after which practically, the degradation efficiency decreases.Several factors influencing the photoactivity of the composite include the pH of the Rh.B solution, initial concentration of Rh.B, ZIF-8/Ag2S photocatalyst dose, initial Rh.B concentration, and dye type. The ZIF-8/Ag2S nanocomposite showed good stability and reusability after five reuse cycles.