Peroxide Molecules Research Articles

Systemic changes in photosynthesis and reactive oxygen species homeostasis in shoots of Arabidopsis thaliana infected with the beet cyst nematode Heterodera schachtii.

Photosynthetic efficiency and redox homeostasis are important for plant physiological processes during regular development as well as defence responses. The second-stage juveniles of Heterodera schachtii induce syncytial feeding sites in host roots. To ascertain whether the development of syncytia alters photosynthesis and the metabolism of reactive oxygen species (ROS), chlorophyll a fluorescence measurements and antioxidant responses were studied in Arabidopsis thaliana shoots on the day of inoculation and at 3, 7 and 15 days post-inoculation (dpi). Nematode parasitism caused an accumulation of superoxide and hydrogen peroxide molecules in the shoots of infected plants at 3 dpi, probably as a result of the observed down-regulation of antioxidant enzymes. These changes were accompanied by an increase in RNA and lipid oxidation markers. The activities of antioxidant enzymes were found to be enhanced on infection at 7 and 15 dpi, and the content of anthocyanins was elevated from 3 dpi. The fluorescence parameter Rfd , defining plant vitality and the photosynthetic capacity of leaves, decreased by 11% only at 7 dpi, and non-photochemical quenching (NPQ), indicating the effectiveness of photoprotection mechanisms, was about 16% lower at 3 and 7 dpi. As a result of infection, the ultrastructure of chloroplasts was changed (large starch grains and plastoglobules), and more numerous and larger peroxisomes were observed in the mesophyll cells of leaves. We postulate that the joint action of antioxidant enzymes/molecules and photochemical mechanisms leading to the maintenance of photosynthetic efficiency promotes the fine-tuning of the infected plants to oxidative stress induced by parasitic cyst nematodes.

OXIDATION OF FERRIC XYLENOL ORANGE CHELATES BY HYDROGEN PEROXIDE IN AQUEOUS SOLUTION: CONCEPTION OF OXYGEN SINGLET ATOMS GENERATION FROM HYDROGEN PEROXIDE

We observed for the first time the reaction of oxidation of ferric xylenol orange chelates by hydrogen peroxide in aqueous solution. The reaction is accompanied with decoloration of the violet aqueous solution. Based on generally accepted conception, there is a process of free radical chain oxidation of indicator molecule in the solution. However, after investigating the final colorless solution by 1H NMR-spectroscopy we found the modified but not broken structure in which the initial hydrocarbon core remained mainly unchanged. We concluded that kind of reaction was an oxyfunctionalization by hydrogen peroxide versus free radical chain destruction. We argued steps of the reaction such as N-oxidation, Cope’s elimination, and certain rearrangements with possible products oligomerization. There was a need to explain the mechanism of interaction between the ferric iron ion and the hydrogen peroxide molecule and to argue the nature of intermediate reactive oxygen species. There is similarity between the ferric-catalyzed hydroperoxide xylenol orange oxidation and the peroxygenase-catalyzed biochemical oxyfunctionalization reactions. However, based on literature data and molecular orbital modeling, we proposed another mechanism of interaction between the ferric iron ion and the hydrogen peroxide molecule instead the tetravalent iron generation. Concretely, we proposed the hydrogen peroxide zwitter-ionization (isomerization to oxywater molecule) and subsequent intramolecular disproportionation with generation of a water molecule and a singlet oxygen atom as a reactive oxygen species. In this view, the iron ion oxidation state is unchanged during the reaction and remains ferric. An oxyfunctionalization of any organic substrate by hydrogen peroxide in the presence of ferric iron ions is promising approach in organic synthesis. However, the usage of organic ligands for ferric iron ions as components of catalysts is limited and requires only non-oxidizable compounds. On the other hand, one can choose an oxidation substrate as a ligand for ferric iron ions that is the formation of chelate complex of ferric catalyst with an organic substrate.Forcitation:Chumakov A.A., Kotelnikov O.A., Slizhov Yu.G. Oxidation of ferric xylenol orange chelates by hydrogen peroxide in aqueous solution: conception of oxygen singlet atoms generation from hydrogen peroxide. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 2. P. 15-22

Molecular dynamics of reactions between (4,0) zigzag carbon nanotube and hydrogen peroxide under extreme conditions

ABSTRACTSingle-wall carbon nanotubes (CNTs) have been suggested as potential materials for use in next-generation gas sensors. The sidewall functionalisation of CNTs facilitates gas molecule adsorption. In this study, density functional theory (DFT)-based ab initio molecular dynamics simulations are performed for a periodic zigzag single-wall (4,0) CNT surrounded by a monolayer of hydrogen peroxide molecules in an attempt to find conditions that favour sidewall functionalisation. The dependency of dynamics on charge states of the system is examined. It is found negative charges favour reactions that result in the functionalisation of the CNT. First principles molecular dynamics of defect formation yields chemically reasonable structure of stable defects, which can be reproduced in CNTs of any diameter and chirality. The explored hydroxyl and hydroperoxyl defects increase conductivity in a large diameter (10,0) CNT, while decrease conductivities in a small diameter (4,0) CNT.

Complexes of hydrogen peroxide and DNA phosphate group in quantum chemical calculations

Background: Molecules of hydrogen peroxide (H2O2) can be formed during radiolysis process in water medium after irradiation. A hypothesis about the possible role of hydrogen peroxide in blocking of processes of nonspecific DNA recognition by proteins is proposed in [1]. As one of the most long-living products, H2O2 molecules can diffuse considerable distances in the intracellular medium and reach DNA in the cell nucleus and form complexes with macromolecule phosphate groups. To confirm this hypothesis, the quantum chemical calculations of complexes structure of hydrogen peroxide molecule with atomic groups of the DNA backbone are performed. Objectives: To determine the optimal geometries and formation energies of stable complexes of hydrogen peroxide with DNA phosphate group. To perform a comparative analysis of hydrogen peroxide and water molecules binding to phosphate group based on quantum chemical calculations. Materials and Methods: The complexes which consist of phosphate group, hydrogen peroxide, water molecules, and sodium counterion are analyzed. The optimization of complex geometry and energy calculations is performed using the methods of quantum chemistry within Gaussian 03 software: HF/6-31+G(d,p), MP2/6-31+G(d,p), B3LYP/6-31+G(d,p). Results: This research shows that the hydrogen peroxide molecule as well as water molecule can form stable complexes with phosphate group, especially with the presence of sodium counterion Na+. The results of complex formation calculations with atom-atom potential functions method are confirmed. It is shown that the presence of sodium counterion significantly influences the geometry of the hydrogen peroxide complex with the phosphate group. The performed calculations indicate the possibility of hydrogen peroxide geometry change in the processes of complex formation. Conclusions: The obtained results confirm the possibility of stable complexes forming for hydrogen peroxide and phosphate group. Prolonged situation of H2O2 molecule near the DNA backbone may block the nucleic-protein recognition processes as well as damage the macromolecule via decay into OH-radicals in close proximity to double helix.

Зміна провідності структур «пористий кремній з наночастинками срібла — кремній» при детектуванні перекису водню

The authors investigate the influence of hydrogen peroxide concentration on the conductivity of the porous silicon with silver nanoparticles / crystalline silicon system. A simple resistive sensor with Ag nanoparticles was used as a catalyst in order to study processes occuring in porous silicon during hydrogen peroxide detection. Porous silicon was formed using a two-stage metal-assisted chemical etching with Ag nanoparticles. It was shown that two simultaneous processes are involved here: carrier extraction to porous silicon caused by interaction with hydrogen peroxide molecules and heating caused by hydrogen peroxide decomposition in presence of Ag nanoparticles. Dimensions of the investigated sensor structure were comparable with a drop of the solution, thus at 30‰ concentration heating could reach 10°C. As porous silicon/crystalline silicon system has a negative temperature coefficient, two above mentioned processes counteract which leads to a maximum, or saturation, on the graph of the dependence of resistivity on hydrogen peroxide concentration at 10—11‰. Sensitivity declines from 0.001—0.02 to 0.0001—0.0003%/‰. To prove these thesis resistivity-concentration dependences were adjusted taking into account calculated heating caused by hydrogen peroxide decomposition. It was shown that in this case the slope of the dependence curve remains stable up to 30 ‰ and sensitivity remains about 0.001—0.02%/‰.

Substantiation for Oxywater Zwitterions and Singlet Oxygen Atoms Generation from Hydrogen Peroxide Molecules in Aqueous Solutions

Hydrogen peroxide is widely used as an oxidant. The results of thermodynamic calculations indicate the impossibility of spontaneous generation of hydroxyl and hydroperoxyl radicals from hydrogen peroxide in aqueous solutions. Hydrogen peroxide spontaneously decomposes in ferrous, ferric, and cupric Fenton reaction systems. Ferric xylenol orange and ferric pyridoxine complexes are oxidized rapidly and spontaneously by this oxidant. Hydrogen peroxide in aqueous solutions spontaneously oxidizes the sulfur atoms of hyposulfite anions and benzylpenicillin molecules. Thus, a hydrogen peroxide molecule generates another intermediate that differs from hydroxyl and hydroperoxyl radicals. Theoretical modeling shows that hydrogen peroxide can participate in the proton transfer reactions. Its isomerization to oxywater zwitterion with subsequent oxywater intramolecular disproportionation is a process that is very suitable for explaining all events of hydrogen peroxide decomposition and oxidative reactivity in aqueous systems. The oxywater zwitterion is a bipolar ion in which the opposite charges are localized on neighboring oxygen atoms. This determines the displacement of electron density from the negatively charged atom to the positively charged atom. As a result, the interoxygen bond heterolytically dissociates with liberation of a water molecule and formation of an oxygen atom (oxene) in a singlet quantum state. This atom has a vacant atomic orbital. The S-oxidation of benzylpenicillin and hyposulfite occurs via targeting of electron pairs of the sulfur atoms by the vacant atomic orbitals of the singlet oxygen atoms. We substantiate an oxene-mediated pathway of hydrogen peroxide disproportionation. A singlet oxygen atom interacts with a second hydrogen peroxide molecule through targeting the unshared electron pair of the oxygen atom by a vacant atomic orbital. The process may be called O-oxidation of hydrogen peroxide; it results in trioxidane (dihydrogen trioxide) formation. Hydrogen trioxide rapidly decomposes and produces water and singlet dioxygen. We have suggested a mechanism of the electron spin rotation during the singlet dioxygen quenching into the triplet quantum state. We have assumed the formation of a dimeric associate from singlet dioxygen antipodes by orbital parameter. Two simultaneous redox reactions (the electron exchange interaction) result in generation of two triplet dioxygen molecules. The first triplet molecule has +1 total electron spin, and the second one has –1 total electron spin. For Fenton reaction systems, the zwitterionization of hydrogen peroxide in Lewis acid-base complexes with metal ions is followed by intramolecular disproportionation of oxywater. The singlet oxene remains in complex with a metal ion. Ferrous iron ion changes its oxidation state to ferric due to rapid and inevitable one-electron transfer within the iron(II)-oxene complex. The ferric-oxyl complex is known as alpha-oxygen complex. In our opinion, the classic Fenton reaction occurs through alpha-complex formation. We maintain such view that is alternative to widespread conceptions of the hydroxyl radical generation or oxoferryl(IV) formation. We have reproduced electro-Fenton reactions of transition metal ions with electrogenerated hydrogen peroxide and presumably observed voltammetric signals for the singlet oxene atoms and oxyl radical anions (alpha-oxygen particles). The oxywater-oxene concept is successfully applicable to explain the catalytic activity of redox-inactive substances. We have used our oxywater-oxene concept for explanation of hydroperoxide monooxygen and dioxygen oxidative functionalization mechanisms in organic synthesis.

Detection of simple inorganic and organic molecules over Cu-decorated circumcoronene: a combined DFT and QTAIM study.

Nowadays graphene materials have attracted a considerable attention because of their potential utilization as gas sensors, biosensors, or adsorbents. Doping or decorating the graphene surface with transition metals can significantly tune its electronic properties and chemical reactivity. Circumcoronene, being a polyaromatic hydrocarbon composed of 19 benzene rings, can be used as a model system of a tiny graphene quantum dot. The adsorption of a set of small molecules (water, hydrogen peroxide, methanol, ethanol, and oxygen) over the copper-decorated circumcoronene was theoretically investigated using density functional theory (DFT) and Bader's quantum theory of atoms in molecules (QTAIM). Following the obtained B3LYP energies, the adsorption of O2 and the chemisorption of H2O2 were found to be energetically the most favorable, with energetic outcomes of -3.6 eV and -3.7 eV, respectively. Moreover, an H2O2 molecule was decomposed during the chemisorption on the Cu atom to form a neutral Cu(OH)2 molecule. Changes in the electronic structure of the studied systems, in particular the oxidation of copper, after the adsorption were investigated within the framework of QTAIM (e.g., charges, bond critical points, and delocalization indices) and partial density of states (PDOS) analysis. The results of this study suggest the suitability of the Cu-decorated graphene materials as adsorbents and/or gas sensors in practical applications.

Green Synthesis of CoFe2O4 and Investigation of its Catalytic Efficiency for Degradation of Dyes in Aqueous Medium

Abstract The catalytic wet oxidation is one the methods used for elimination of dyes from aqueous medium in which various metal based materials can be used as heterogeneous catalysts. Bimetallic oxides as heterogeneous catalysts have gained much attention as bimetallization improve the catalytic properties of the resulting particles. The biosynthetic green method is the most viable and simple method for synthesis of bimetallic oxides nanoparticles. Here, we report the green synthesis of CoFe2O4 particles using Azadirachata indica leaves extract as reducing and stabilizing agent. The synthesized particles were characterized using X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy and scanning electron microscopy. The synthesized CoFe2O4 particles were tested as a catalyst for mineralization of rhodamine B and methylene blue dyes in the presence of hydrogen peroxide in aqueous media. More than 95% dyes degraded in 120 min. The reaction kinetics was described in terms of Langmuir–Hinshelwood mechanism which suggests that molecules of dye and hydrogen peroxide adsorbed surface of CoFe2O4 and then react together.

On the stability of Al13 Keggin cation in aqueous hydrogen peroxide solutions

We report the first attempt to study the behavior of the [AlO4Al12(OH)25(H2O)11]6+ (Al13) Keggin cation (KC) in water–peroxide solutions. Addition of hydrogen peroxide into an aqueous solution containing the Al13 KC reduces pH due to the acidity of hydrogen peroxide. According to the 27Al NMR studies of water–peroxide solutions prepared just before the NMR experiment, with their pH adjusted to the initial value of 5.5 with aqueous NaOH, the Al13 KC concentration decreases immediately once hydrogen peroxide is added to the initial system. Addition of 18.2 wt % hydrogen peroxide to the initial 0.88 mM Al13 solution gives rise to a fourfold decline in Al13 polyoxo cation concentration to 0.22 mM. Then, the KC concentration in the test system remains unchanged for 1 week. Large hydrogen peroxide amounts (27.9 wt % or higher) added to the initial system almost completely degrade the KC. Sodium sulfate added to the initial water–peroxide solution of Al13 chloride where the hydrogen peroxide concentration is 5.5 wt % precipitates the earlier described Al13 sulfate [AlO4Al12(OH)25(H2O)11](SO4)3 · 16H2O, where the aluminum polyoxo cation does not contain coordinated hydrogen peroxide molecules, peroxo or hydroperoxo groups as shown by X-ray diffraction.

Candida Albicans FRE8 Encodes a Member of the NADPH Oxidase Family that Produces a Burst of ROS Important for Morphogenesis

NADPH oxidase (NOX) enzymes, which produce reactive oxygen species (ROS), were until recently thought to occur only in multicellular organisms. ROS have important physiological effects such as acting as signaling molecules in biological processes or as defense mechanisms against invading microbes through oxidative damage. In this work, we demonstrate that the unicellular fungus Candida albicans is capable of producing an extracellular ROS burst using a member of the NOX enzyme family identified as Fre8. C. albicans is an opportunistic human fungal pathogen which undergoes morphologic transition between yeast, pseudohyphal, and hyphal forms. During morphogenesis, FRE8 is induced to produce ROS specifically at the growing tip of the polarized cell. The extracellular superoxide dismutase, Sod5, is also induced during morphogenesis and our findings are consistent with a model in which Sod5 acts as a partner for Fre8, converting Fre8-derived superoxide to the diffusible hydrogen peroxide molecule. Fre8∆/∆ mutants exhibit a morphogenesis defect in vitro and are specifically impaired in the development or maintenance of elongated hyphae in high density cultures. A fre8∆/∆ defect in hyphal formation was similarly observed in a disseminated candidiasis model. Moreover, in a rat catheter model, C. albicans fre8∆/∆ mutants showed deficiencies in biofilm formation. Together these studies demonstrate that like multicellular organisms, the unicellular C. albicans expresses NOX to produce ROS and this signal helps drive fungal morphogenesis in the animal host.

Crystal structure of 2,3,5,6-tetra-kis-(pyridin-2-yl)pyrazine hydrogen peroxide 4.75-solvate.

The structure of the title co-crystal, C24H16N6·4.75H2O2, consists of a 2,3,5,6-tetra-kis-(pyridin-2-yl)pyrazine coformer and hydrogen peroxide solvent mol-ecules in an overall ratio of 1:4.75. Three of the six H2O2 mol-ecules modelled in the structure were found to be cross-orientationally disordered over two positions with occupancy ratios 0.846 (9):0.154 (9), 0.75 (2):0.25 (2), and 0.891 (9):0.109 (9). In the crystal, all of the peroxide mol-ecules are linked into hydrogen-bonded chains that propagate parallel to the a axis. These chains are further linked by O-H⋯N hydrogen bonds to the pyridine groups of the main mol-ecule.

Crystal structure of (Z)-N-benzylidene-1-phenylmethanamine oxide hydrogen peroxide monosolvate

The title adduct, C14H13NO·H2O2, consists of (Z)-N-benzyl-idene-1-phenyl-methanamine oxide and hydrogen peroxide mol-ecules in a 1:1 ratio. The organic coformer adopts a skew geometry with an inter-aryl-ring dihedral angle of 81.9 (2)°. In the crystal, the organic and peroxide mol-ecules are linked through both peroxide O-H donor groups to oxide O-atom acceptors, giving one-dimensional chains extending along the b axis. Present also are weak inter-molecular C-H⋯O hydrogen-bonding inter-actions.

A DFT and QTAIM study of the adsorption of organic molecules over the copper-doped coronene and circumcoronene

Graphene based materials are nowadays extensively studied because of their potential applications as gas sensors, biosensors or adsorbents. Doping the graphene surface with heteroatoms or transition metals can improve its electronic properties and chemical reactivity. Polyaromatic hydrocarbons coronene and circumcoronene can be used as models of tiny graphene quantum dots. The adsorption of a set of organic molecules (water, hydrogen peroxide, hydrogen sulfide, methanol, ethanol and oxygen molecule) over the copper-doped coronene and circumcoronene was theoretically studied using density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM). In the case of coronene, only one site was considered for the Cu-doping, whereas in the case of circumcoronene being a polyaromatic hydrocarbon composed of 54 carbon atoms, three different sites for Cu-doping were considered. For the systems under study, the adsorption of O2 was found energetically the most favorable, with energetic outcome ranging from –3.1 to −3.7eV related to the position of dopant Cu atom. Changes in the topology of charge densities at Cu and in its vicinity after the adsorption of studied molecules were investigated in the framework of QTAIM. In addition, QTAIM analysis of bond critical points (BCP) was employed to study the character of the newly formed chemical bonds. The results of this study point out the suitability of Cu-doped graphene materials as sensors and/or adsorbents in practical applications.

VERIFICATION OF NON-CATALYTIC HYDROGEN PEROXIDE DISPROPORTIONATION MECHANISM BY THERMODYNAMIC ANALYSIS OF ONE-ELECTRON REDOX REACTIONS

There is two-electron transfer during the process of hydrogen peroxide decomposition into water and oxygen. The detailed mechanism of non-catalytic hydrogen peroxide disproportionation is not verified until now. We assumed that any poly-electron redox process is a complex and consists of one-electron redox reactions. We have formulated equations of possible one-electron transfers during hydrogen peroxide disproportionation. Based on known laws and equations of thermochemistry we calculated standard thermodynamic functions for a total reaction and each one-elect-ron redox reaction using reference values of standard thermodynamic functions of reagents and products of reactions. Results show that the total reaction leads to significant decrease in Gibbs free energy -246.0 kJ/mol in gas phase but there is increase +39.9 kJ/mol in Gibbs free energy during the first proposed step. It is substantiation for known dependence of hydrogen peroxide dismutation kinetics at thermal, photochemical or catalytic activation. The first proposed step of non-catalytic process is one-electron plus one-proton transfer in thermally or photochemically activated dimeric hydrogen peroxide associate (H2O2)2 with simultaneous generation of hydroperoxyl HO2• and hydroxyl HO• free radicals and water molecule. There is thermodynamic argumentation for radical chain mechanism of hydrogen peroxide disproportionation after the activation. We made the graphic illustration of thermodynamically supported scheme of non-catalytic hydrogen peroxide decomposition. There is a cyclic alternation of two radical-molecular interactions during the hydrogen peroxide chain decomposition. The hydroxyl radical generates the hydroperoxyl radi-cal from a hydrogen peroxide molecule and then the hydroperoxyl radical interacts with a next hydrogen peroxide molecule followed by the hydroxyl radical generation. Interactions between the homonymic or heteronymic free radicals are the reactions of chain breaking.Forcitation:Chumakov A.A., Batalova V.N., Slizhov Yu.G., Minakova T.S. Verification of non-catalytic hydrogen peroxide disproportionation mechanism by thermodynamic analysis of one-electron redox reactions. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 6. P. 40-44.

Nitric Oxide and Hydrogen Peroxide Mediate Wounding-Induced Freezing Tolerance through Modifications in Photosystem and Antioxidant System in Wheat.

Mechanical wounding is a common stress caused by herbivores or manual and natural manipulations, whereas its roles in acclimation response to a wide spectrum of abiotic stresses remain unclear. The present work showed that local mechanical wounding enhanced freezing tolerance in untreated systemic leaves of wheat plants (Triticum aestivum L.), and meanwhile the signal molecules hydrogen peroxide (H2O2) and nitric oxide (NO) were accumulated systemically. Pharmacological study showed that wounding-induced NO synthesis was substantially arrested by pretreatment with scavengers of reactive oxygen species and an inhibitor of NADPH oxidase (respiratory burst oxidase homolog, RBOH). On the contrary, wounding-induced H2O2 accumulation was not sensitive to NO synthetic inhibitors or scavenger, indicating that H2O2 acts upstream of NO in wounding signal transduction pathways. Cytochemical and vascular tissues localizations approved that RBOH-dependent H2O2 acts as long-distance signal in wounding response. Transcriptome analysis revealed that 279 genes were up-regulated in plants treated with wounding and freezing, but not in plants treated with freezing alone. Importantly, freezing- and wounding-induced genes were significantly enriched in the categories of “photosynthesis” and “signaling.” These results strongly supported that primary mechanical wounding can induce freezing tolerance in wheat through the systemic accumulation of NO and H2O2, and further modifications in photosystem and antioxidant system.

DFT study of the adsorption of H2O2 inside and outside Al12N12 nano-cage

The adsorption of hydrogen peroxide (H2O2) molecule on the outer and inner surfaces of Al12N12 nano-cage in terms of energetic, geometric, and electronic properties has been investigated using the density functional theory (DFT) calculations by B3LYP-D and M06-2X methods and 6-31G** basis set. It has been found that H2O2 molecule can be strongly chemisorbed (−3.45 eV) over the outer surface of the Al12N12 nanocage, where the adsorption energy depending upon its orientation with the nano-cage. Moreover, the adsorption of two H2O2 molecules on the outside surface of adsorbent is about −2.05 eV, while the adsorption of the molecule trapped inside adsorbent is about −1.81 eV. It was found that the H2O2 adsorption on the outer and inner surfaces of Al12N12 nano-cage leads to slightly lower energy gap and increasing the dipole moment of adsorbent.

Role of peroxiredoxin2 downregulation in recurrent miscarriage through regulation of trophoblast proliferation and apoptosis

Peroxiredoxin (Prdx) 2 is an antioxidant protein that utilizes its redox-sensitive cysteine groups to reduce hydrogen peroxide molecules and protect cells against oxidative damage from reactive oxygen species (ROS). However, its function in trophoblasts at the maternal–fetal interface has not been clarified yet. In this study, significantly lower Prdx2 expression was found in the first-trimester villous cytotrophoblasts of patients with recurrent miscarriage (RM) than in cytotrophoblasts from healthy controls. Further, Prdx2 knockdown inhibited proliferation and increased apoptosis of trophoblast cells. The reason for this may be an increase in the level of cellular ROS after knockdown of Prdx2, which may subsequently lead to an increase in the expression of phosphorylated p53 (p-p53) and p38-MAPK/p21. Prdx2 knockdown also impaired the fusion of BeWo cells induced by forskolin. Bioinformatics analysis identified a c-Myc-binding site in the Prdx2 promoter region, and chromatin immunoprecipitation verified that c-Myc directly bound to a site in this locus. Suppression and overexpression of c-Myc resulted in reduction and increase of Prdx2 expression respectively. Furthermore, we demonstrated that c-Myc was downregulated in the first-trimester cytotrophoblasts of patients with RM, and its downregulation is also related with inhibited cell proliferation, increased apoptosis, as well as upregulated p21 expression and p-p53/p53 ratio. Our findings indicate that Prdx2 might have an important role in the regulation of trophoblast proliferation and apoptosis during early pregnancy, and that its expression is mediated by c-Myc. Thus, these two proteins may be involved in the pathogenesis of RM and may represent potential therapeutic targets.

Foliage‐applied sodium nitroprusside and hydrogen peroxide improves resistance against terminal drought in bread wheat

AbstractTerminal drought is threatening the wheat productivity worldwide, which is consumed as a staple food by millions across the globe. This study was conducted to examine the influence of foliage‐applied stress signalling molecules hydrogen peroxide (H2O2; 50, 100, 150 μm) and nitric oxide donor sodium nitroprusside (SNP; 50, 100, 150 μm) on resistance against terminal drought in two bread wheat cultivars Mairaj‐2008 and BARS‐2009. These stress signalling molecules were applied at anthesis stage (BBCH 61); drought was then imposed by maintaining pots at 35% water holding capacity. Terminal drought caused significant reduction in grain yield of both tested bread wheat cultivars; however, foliage application of both stress signalling molecules at either concentration improved the performance of both bread wheat cultivars. Maximum improvement in 100‐grain weight (12.2%), grains per spike (19.7%), water‐use efficiency (WUE; 19.8%), chlorophyll content index (10.7%), total soluble phenolics (21.6%) and free leaf proline (34.3%), and highest reduction in leaf malondialdehyde contents (20.4%) was recorded when H2O2 was foliage‐applied at 100 μm. Foliage application of SNP enhanced the grains per spike, 100‐grain weight and grain yield by 14.9%, 11.3% and 20.1%, respectively, than control. The foliage‐applied stress signalling molecules improved the accumulation of soluble phenolics, proline and glycine betaine with simultaneous reduction in malondialdehyde contents, which enabled wheat plants to sustain the biological membranes under stress resulting in better stay green (high chlorophyll contents) under drought. This helped improving the grain number, grain weight, grain yield, WUE and transpiration efficiency. In crux, foliage‐applied H2O2 and SNP, at pre‐optimized rate, may be opted to lessen the drought‐induced yield losses in bread wheat in climate change conditions.

A study of the antioxidant and membranotropic activities of equinochrome a using different model systems

Echinochrome A (6-ethyl-2,3,5,7,8-pentahydroxy-1,4-naphthoquinone) isolated from the body of sand dollar Scaphechinus mirabilis is an active substance of cardioprotective medication Histochrome and exerts a wide spectrum of anti-inflammatory activities. In the present paper, we conducted a comparative study of the antioxidant (radical-scavengering) properties of echinochrome A in 2,2′-azobis(2-methylpropionamidine) dihydrochloride−luminol and hemoglobin−hydrogen peroxide−luminol systems and assessed its impact on permeability of planar bilayer lipid membranes. Trolox was used as a reference antioxidant and ascorbic acid and dihydroquercetin are taken as standards. Echinochrome A shows moderate antioxidant activity, possessing higher antioxidant capacity than Trolox and ascorbic acid, but exhibiting lower antioxidant potential compared with dihydroquercetin in tests for antioxidant activity in both investigated systems. The test substances can be arranged in the following order according to the effectiveness of the antioxidant effect: dihydroquercetin > echinochrome A > Trolox > ascorbic acid. Echinochrome A does not lead to significant changes in the permeability of planar bilayer membranes in a dose range of 1.5 to 30 μМ. Our data indicate that echinochrome A has a rather high level of radical-scavengering activity without a primary membranotropic effect. It is thought that the high levels of the cardioprotective and anti-inflammatory activities of echinochrome A may be due not only to the ability of this substance to neutralize reactive oxygen species, but also to its capacity to generate physiological concentrations of hydrogen peroxide molecules in biological systems as signaling messengers of various metabolic processes and biochemical pathways. The suspected mechanisms of the biological activity of echinochrome A are discussed.

Effects of Reactive Oxygen Species on Tubular Transport along the Nephron.

Reactive oxygen species (ROS) are oxygen-containing molecules naturally occurring in both inorganic and biological chemical systems. Due to their high reactivity and potentially damaging effects to biomolecules, cells express a battery of enzymes to rapidly metabolize them to innocuous intermediaries. Initially, ROS were considered by biologists as dangerous byproducts of respiration capable of causing oxidative stress, a condition in which overproduction of ROS leads to a reduction in protective molecules and enzymes and consequent damage to lipids, proteins, and DNA. In fact, ROS are used by immune systems to kill virus and bacteria, causing inflammation and local tissue damage. Today, we know that the functions of ROS are not so limited, and that they also act as signaling molecules mediating processes as diverse as gene expression, mechanosensation, and epithelial transport. In the kidney, ROS such as nitric oxide (NO), superoxide (O2−), and their derivative molecules hydrogen peroxide (H2O2) and peroxynitrite (ONO2−) regulate solute and water reabsorption, which is vital to maintain electrolyte homeostasis and extracellular fluid volume. This article reviews the effects of NO, O2−, ONO2−, and H2O2 on water and electrolyte reabsorption in proximal tubules, thick ascending limbs, and collecting ducts, and the effects of NO and O2− in the macula densa on tubuloglomerular feedback.