Showing papers on "Hydrogen peroxide published in 2016"

Involvement of Hydrogen Peroxide in the Regulation of

Abstract: Endogenous peroxide levels in pear fruit (Pyrus communis) were measured using a titanium assay method, and were found to increase during senescence in both Bartlett and Bosc varieties. Application of glycolic acid or xanthine, serving as substrates for the formation of H202, increased the peroxide content of the tissue and accelerated the onset of ripening, as measured by increased softening and ethylene evolution. Application of ethylene also induced increased peroxide levels. Ripening processes were similarly promoted when peroxides were conserved by inhibiting the activity of catalase with hydroxylamine or potassium cyanide. By comparison, the inhibition of glycolate oxidase with alphahydroxy-2-pyridinemethanesulfonic acid decreased the peroxide content of the tissue and delayed the onset of ripening. These results indicate that the onset of ripening correlates with the peroxide content of fruit tissues as occurring under normal conditions or as influenced by the treatments. Hydrogen peroxide may be involved in oxidative processes required in the initiation and the promotion of ripening.

Role of oxidative stress in Alzheimer's disease (Review)

Abstract: Alzheimer's disease (AD) is the most common cause of disability in individuals aged >65 years worldwide. AD is characterized by the abnormal deposition of amyloid β (Aβ) peptide, and intracellular accumulation of neurofibrillary tangles of hyperphosphorylated τ protein and dementia. The neurotoxic oligomer Aβ peptide, which is the neuropathological diagnostic criterion of the disease, together with τ protein, are mediators of the neurodegeneration that is among the main causative factors. However, these phenomena are mainly initiated and enhanced by oxidative stress, a process referring to an imbalance between antioxidants and oxidants in favour of oxidants. This imbalance can occur as a result of increased free radicals or a decrease in antioxidant defense, free radicals being a species that contains one or more unpaired electrons in its outer shell. The major source of potent free radicals is the reduction of molecular oxygen in water, that initially yields the superoxide radical, which produces hydrogen peroxide by the addition of an electron. The reduction of hydrogen peroxide produces highly reactive hydroxyl radicals, termed reactive oxygen species (ROS) that can react with lipids, proteins, nucleic acids, and other molecules and may also alter their structures and functions. Thus, tissues and organs, particularly the brain, a vulnerable organ, are affected by ROS due to its composition. The brain is largely composed of easily oxidizable lipids while featuring a high oxygen consumption rate. The current review examined the role of oxidative stress in AD.

Reactive Oxygen Species and Neutrophil Function

Abstract: Neutrophils are essential for killing bacteria and other microorganisms, and they also have a significant role in regulating the inflammatory response. Stimulated neutrophils activate their NADPH oxidase (NOX2) to generate large amounts of superoxide, which acts as a precursor of hydrogen peroxide and other reactive oxygen species that are generated by their heme enzyme myeloperoxidase. When neutrophils engulf bacteria they enclose them in small vesicles (phagosomes) into which superoxide is released by activated NOX2 on the internalized neutrophil membrane. The superoxide dismutates to hydrogen peroxide, which is used by myeloperoxidase to generate other oxidants, including the highly microbicidal species hypochlorous acid. NOX activation occurs at other sites in the cell, where it is considered to have a regulatory function. Neutrophils also release oxidants, which can modify extracellular targets and affect the function of neighboring cells. We discuss the identity and chemical properties of the specific oxidants produced by neutrophils in different situations, and what is known about oxidative mechanisms of microbial killing, inflammatory tissue damage, and signaling.

Effective photocatalytic H2O2 production under visible light irradiation at g-C3N4 modulated by carbon vacancies

Abstract: Hydrogen peroxide (H2O2) is of great significance in biological and environmental processes as well as in chemical industry. Even though anthraquinone autoxidation (AO) process has been the major artificial way to produce H2O2, its energy cost and non-green nature have been motivating people to develop more efficient, economic and green technologies as alternatives. Here we demonstrated that photocatalytic H2O2 production at g-C3N4 could be improved by as much as 14 times in the absence of organic scavenger through a carbon vacancy-based strategy. Both the experimental and theoretical calculation results indicated that the creation of carbon vacancies could reduce the symmetry of g-C3N4 and produce the effect of electron delocalization. This will allow g-C3N4 to possess more excitable electrons and a narrower band gap. On the other hand, carbon vacancies provided more sites to adsorb molecular oxygen and thereby help electrons transfer from g-C3N4 to the surface adsorbed O2. More interestingly, the presence of carbon vacancies changed the H2O2 generation pathway from a two-step single-electron indirect reduction to an one-step two-electron direct reduction. This study could not only develop a novel strategy to improve the H2O2 production activity of semiconductors, but also shed light on the deep understanding of the role played by surface defect structure on photocatalytic activity of semiconductor photocatalysts.

Production of Reactive Oxygen Species by Photosystem II as a Response to Light and Temperature Stress.

Abstract: The effect of various abiotic stresses on photosynthetic apparatus is inevitably associated with formation of harmful reactive oxygen species (ROS). In this review, recent progress on ROS production by photosystem II (PSII) as a response to high light and high temperature is overviewed. Under high light, ROS production is unavoidably associated with excitation energy transfer and electron transport in PSII. Singlet oxygen is produced by the energy transfer form triplet chlorophyll to molecular oxygen formed by the intersystem crossing from singlet chlorophyll in the PSII antennae complex or the recombination of the charge separated radical pair in the PSII reaction center. Apart to triplet chlorophyll, triplet carbonyl formed by lipid peroxidation transfers energy to molecular oxygen forming singlet oxygen. On the PSII electron acceptor side, electron leakage to molecular oxygen forms superoxide anion radical which dismutes to hydrogen peroxide which is reduced by the non-heme iron to hydroxyl radical. On the PSII electron donor side, incomplete water oxidation forms hydrogen peroxide which is reduced by manganese to hydroxyl radical. Under high temperature, dark production of singlet oxygen results from lipid peroxidation initiated by lipoxygenase, whereas incomplete water oxidation forms hydrogen peroxide which is reduced by manganese to hydroxyl radical. The understanding of molecular basis for ROS production by PSII provides new insight into how plants survive under adverse environmental conditions.

Different Modes of Hydrogen Peroxide Action During Seed Germination.

Abstract: Hydrogen peroxide was initially recognized as a toxic molecule that causes damage at different levels of cell organization and thus losses in cell viability. From the 1990s, the role of hydrogen peroxide as a signaling molecule in plants has also been discussed. The beneficial role of H2O2 as a central hub integrating signaling network in response to biotic and abiotic stress and during developmental processes is now well established. Seed germination is the most pivotal phase of the plant life cycle, affecting plant growth and productivity. The function of hydrogen peroxide in seed germination and seed aging has been illustrated in numerous studies; however, the exact role of this molecule remains unknown. This review evaluates evidence that shows that H2O2 functions as a signaling molecule in seed physiology in accordance with the known biology and biochemistry of H2O2. The importance of crosstalk between hydrogen peroxide and a number of signaling molecules, including plant phytohormones such as abscisic acid, gibberellins and ethylene and reactive molecules such as nitric oxide and hydrogen sulfide acting on cell communication and signaling during seed germination, is highlighted. The current study also focuses on the detrimental effects of H2O2 on seed biology, i.e., seed aging that leads to a loss of germination efficiency. The dual nature of hydrogen peroxide as a toxic molecule on one hand and as a signal molecule on the other is made possible through the precise spatial and temporal control of its production and degradation. Levels of hydrogen peroxide in germinating seeds and young seedlings can be modulated via pre-sowing seed priming/conditioning. This rather simple method is shown to be a valuable tool for improving seed quality and for enhancing seed stress tolerance during post-priming germination. In this review, we outline how seed priming/conditioning affects the integrative role of hydrogen peroxide in seed germination and aging.

Non-Thermal Plasma in Contact with Water: The Origin of Species.

Abstract: Non-thermal atmospheric pressure plasma has attracted considerable attention in recent years due to its potential for biomedical applications Determining the mechanism of the formation of reactive species in liquid treated with plasma is thus of paramount importance for both fundamental and applied research In this work, the origin of reactive species in plasma-treated aqueous solutions was investigated by using spin-trapping, hydrogen and oxygen isotopic labelling and electron paramagnetic resonance (EPR) spectroscopy The species originating from molecules in the liquid phase and those introduced with the feed gas were differentiated by EPR and 1H NMR analysis of liquid samples The effects of water vapour and oxygen admixtures in the feed gas were investigated All the reactive species detected in the liquid samples were shown to be formed largely in the plasma gas phase It is suggested that hydrogen peroxide (determined by UV/Vis analysis) is formed primarily in the plasma tube, whereas the radical species ⋅OOH, ⋅OH and ⋅H are proposed to originate from the region between the plasma nozzle and the liquid sample

Peroxidase-like activity of the Co3O4 nanoparticles used for biodetection and evaluation of antioxidant behavior

Abstract: Nanostructured enzyme mimics are of great interest as promising alternatives to artificial enzymes for biomedical and catalytic applications. Studying the chemical interactions between antioxidants and nano-enzymes may result in a better understanding of the antioxidant capability of antioxidants and may help improve the function of artificial enzymes to better mimic natural enzymes. In this study, using Co3O4 nanoparticles (NPs) as peroxidase mimics to catalyze the oxidation of chromophoric substrates by H2O2, we developed a platform that acts as a biosensor for hydrogen peroxide and glucose and that can study the inhibitory effects of natural antioxidants on peroxidase mimics. This method can be applied specifically to glucose detection in real samples. Three natural antioxidants, gallic acid (GA), tannic acid (TA), and ascorbic acid (AA), were compared for their antioxidant capabilities. We found that these three antioxidants efficiently inhibit peroxidase-like activity with concentration dependence. The antioxidants showed different efficiencies, in the following order: tannic acid > gallic acid > ascorbic acid. They also showed distinct modes of inhibition based on different interaction mechanisms. This study serves as a proof-of-concept that nano-enzyme mimics can be used to evaluate antioxidant capabilities and to screen enzyme inhibitors.

Mitochondria-Targeted Fluorescent Probe for Imaging Hydrogen Peroxide in Living Cells.

Abstract: Hydrogen peroxide (H2O2), as a type of reactive oxygen species (ROS), can be endogenously produced from the mitochondrial electron transport chain in aerobic respiration and plays important roles in several physiological processes. However, the design and synthesis of fluorescent probes, which can detect mitochondrial H2O2 in living cells, still remain rare. Herein, we report the preparation of a novel cationic probe 1 (Mito-H2O2), which targets the mitochondria in living cells and is sensitive to the presence of H2O2. The probe Mito-H2O2 displays desired properties such as high specificity, “Turn-On” fluorescence response with suitable sensitivity, appreciable water solubility, and rapid response time (within 5 min). The sensing mechanism was confirmed by high-resolution mass spectroscopy analysis, and the mechanism of “Turn-On” fluorescent response was also determined using a density functional theory (DFT) calculation method. Moreover, as a biocompatible molecule, the probe Mito-H2O2 has been successfu...

New Trends in Oxidative Functionalization of Carbon–Hydrogen Bonds: A Review

Abstract: This review describes new reactions catalyzed by recently discovered types of metal complexes and catalytic systems (catalyst + co-catalyst). Works of recent years (mainly 2010–2016) devoted to the oxygenations of saturated, aromatic hydrocarbons and other carbon–hydrogen compounds are surveyed. Both soluble metal complexes and solid metal compounds catalyze such transformations. Molecular oxygen, hydrogen peroxide, alkyl peroxides, and peroxy acids were used in these reactions as oxidants.

Activation of Oxygen and Hydrogen Peroxide by Copper(II) Coupled with Hydroxylamine for Oxidation of Organic Contaminants.

Abstract: This study reports that the combination of Cu(II) with hydroxylamine (HA) (referred to herein as Cu(II)/HA system) in situ generates H2O2 by reducing dissolved oxygen, subsequently producing reactive oxidants through the reaction of Cu(I) with H2O2. The external supply of H2O2 to the Cu(II)/HA system (i.e., the Cu(II)/H2O2/HA system) was found to further enhance the production of reactive oxidants. Both the Cu(II)/HA and Cu(II)/H2O2/HA systems effectively oxidized benzoate (BA) at pH between 4 and 8, yielding a hydroxylated product, p-hydroxybenzoate (pHBA). The addition of a radical scavenger, tert-butyl alcohol, inhibited the BA oxidation in both systems. However, electron paramagnetic resonance (EPR) spectroscopy analysis indicated that •OH was not produced under either acidic or neutral pH conditions, suggesting that the alternative oxidant, cupryl ion (Cu(III)), is likely a dominant oxidant.

Reaction of Chromium(VI) with Glutathione or with Hydrogen Peroxide: Identification of Reactive Intermediates and Their Role in

Abstract: The types of reactive intermediates generated upon reduction of chromium(VI) by glutathione or hydrogen peroxide and the resulting DNA damage have been determined. In vitro, reaction of chromium(VI) with glutathione led to formation of two chromium(V) complexes and the glutathione thiyl radical. When chromium(VI) was reacted with DNA in the presence of glutathione, chromium-DNA adducts were obtained, with no DNA strand breakage. The level of chromium-DNA adduct formation correlated with chromium(V) formation. Reaction of chromium(VI) with hydrogen peroxide led to formation of hydroxyl radical. No chromium(V) was detectable at 24?C (297 K); however, low levels of the tetraperoxochromium(V) complex were detected at 77 K. Reaction of chromium(VI) with DNA in the presence of hydrogen peroxide produced significant DNA strand breakage and the 8-hydroxydeoxyguanosine adduct, whose formation correlated with hydroxyl radical production. No significant chromium-DNA adduct formation was detected. Thus, the nature of chromium(VI)-induced DNA damage appears to be dependent on the reactive intermediates, i.e., chromium(V) or hydroxyl radical, produced during the reduction of chromium(VI).

Effects of Atmospheric-Pressure N2, He, Air, and O2 Microplasmas on Mung Bean Seed Germination and Seedling Growth.

Abstract: Atmospheric-pressure N2, He, air, and O2 microplasma arrays have been used to investigate the effects of plasma treatment on seed germination and seedling growth of mung bean in aqueous solution. Seed germination and growth of mung bean were found to strongly depend on the feed gases used to generate plasma and plasma treatment time. Compared to the treatment with atmospheric-pressure O2, N2 and He microplasma arrays, treatment with air microplasma arrays was shown to be more efficient in improving both the seed germination rate and seedling growth, the effect attributed to solution acidification and interactions with plasma-generated reactive oxygen and nitrogen species. Acidic environment caused by air discharge in water may promote leathering of seed chaps, thus enhancing the germination rate of mung bean, and stimulating the growth of hypocotyl and radicle. The interactions between plasma-generated reactive species, such as hydrogen peroxide (H2O2) and nitrogen compounds, and seeds led to a significant acceleration of seed germination and an increase in seedling length of mung bean. Electrolyte leakage rate of mung bean seeds soaked in solution activated using air microplasma was the lowest, while the catalase activity of thus-treated mung bean seeds was the highest compared to other types of microplasma.

Identification of ROS Produced by Nanobubbles and Their Positive and Negative Effects on Vegetable Seed Germination

Abstract: Exogenous reactive oxygen species (ROS) produced by nanobubble (NB) water offer a reasonable explanation for NBs’ physiological promotion and oxidation effects. To develop and exploit the NB technology, we have performed further research to identify the specific ROS produced by NBs. Using a fluorescent reagent APF, a Fenton reaction, a dismutation reaction of superoxide dismutase and DMSO, we distinguished four types of ROS (superoxide anion radical (O2·–), hydrogen peroxide (H2O2), hydroxyl radical (·OH), and singlet oxygen (1O2)). ·OH was confirmed to be the specific ROS produced by NB water. The role of ·OH produced by NB water in physiological processes depends on its concentration. The amount of exogenous ·OH has a positive correlation with the NB number density in the water. Here, spinach and carrot seed germination tests were repeatedly performed with three seed groups submerged in distilled water, high-number density NB water, and low-number density NB water under similar dissolved oxygen concentr...

Rational Design of an α-Ketoamide-Based Near-Infrared Fluorescent Probe Specific for Hydrogen Peroxide in Living Systems

Abstract: Hydrogen peroxide, an important biomolecule, receives earnest attention because of its physiological and pathological functions. In this Article, we present the rational design, characterization, and biological application of a mitochondria-targetable NIR fluorescent sensor, Mito-NIRHP, for hydrogen peroxide visualization. Mito-NIRHP utilizes a unique reaction switch, α-ketoamide moiety, to turn on a highly specific, sensitive, and rapid fluorescence response toward hydrogen peroxide coupled with the intramolecular charge transfer strategy. Mito-NIRHP is competent to track endogenously produced hydrogen peroxide in both living cells and living animals. In addition, utilizing Mito-NIRHP, overgeneration of hydrogen peroxide during ischemia-reperfusion injury was directly visualized at both cell and organ levels.

Nonenzymatic electrochemical sensor based on Fe@Pt core–shell nanoparticles for hydrogen peroxide, glucose and formaldehyde

Abstract: Fe@Pt core–shell nanoparticles were synthetized by spontaneous replacement reaction, using Vulcan XC-72 carbon as support. The physical properties of the obtained Fe@Pt/C nanocomposites were characterized by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy, and the electrocatalytic performances of the Fe@Pt/C were evaluated by cyclic voltammetry and chronoamperometry. Compared with the Pt/C, the Fe@Pt/C exhibited preferable electrocatalytic activity towards the reduction of hydrogen peroxide, and the oxidation of glucose and formaldehyde. Amperometric sensing of hydrogen peroxide was linear to its concentration in the range from 2.5 μM to 41.605 mM, with a detection limit of 750 nM (S/N = 3) and a sensitivity of 218.97 μA mM−1 cm−2. At the same time, the sensor based on Fe@Pt/C showed a linear response range of 1–16 mM glucose, and of 12.5 μM–15.4 mM formaldehyde, with high sensitivities of 11.75 μA mM−1 cm−2 and 40.18 μA mM−1 cm−2, respectively.

Hydrogen Sulfide Donors Activated by Reactive Oxygen Species

Abstract: Hydrogen sulfide (H2 S) exhibits promising protective effects in many (patho)physiological processes, as evidenced by recent reports using synthetic H2 S donors in different biological models. Herein, we report the design and evaluation of compounds denoted PeroxyTCM, which are the first class of reactive oxygen species (ROS)-triggered H2 S donors. These donors are engineered to release carbonyl sulfide (COS) upon activation, which is quickly hydrolyzed to H2 S by the ubiquitous enzyme carbonic anhydrase (CA). The donors are stable in aqueous solution and do not release H2 S until triggered by ROS, such as hydrogen peroxide (H2 O2 ), superoxide (O2- ), and peroxynitrite (ONOO- ). We demonstrate ROS-triggered H2 S donation in live cells and also demonstrate that PeroxyTCM-1 provides protection against H2 O2 -induced oxidative damage, suggesting potential future applications of PeroxyTCM and similar scaffolds in H2 S-related therapies.

Hydrogen Peroxide Solvates of 2,4,6,8,10,12‐Hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane

Abstract: Two polymorphic hydrogen peroxide solvates of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20; wurtzitane is an alternative name to iceane) were obtained using hydrated α-CL-20 as a guide. These novel H2O2 solvates have high crystallographic densities (1.96 and 2.03 g cm−3, respectively), high predicted detonation velocities/pressures (with one solvate performing better than ϵ-CL-20), and a sensitivity similar to that of ϵ-CL-20. The use of hydrated materials as a guide will be important in the development of other energetic materials with hydrogen peroxide. These solvates represent an area of energetic materials that has yet to be explored.

Graphene oxide: a promising carbocatalyst for the regioselective thiocyanation of aromatic amines, phenols, anisols and enolizable ketones by hydrogen peroxide/KSCN in water

Abstract: Graphene oxide (GO), as a heterogeneous carbocatalyst, catalyzes the direct thiocyanation of a variety of arenes including aromatic amines, phenols, anisols and carbonyl compounds that possessing α-hydrogen in the presence of hydrogen peroxide and KSCN in water as a green media. This procedure is chemoselective, avoids the use of precious metals and toxic solvents and has a broad substrate scope. Easy removal from the reaction mixture and recyclability with no loss of activity are the key features of graphene oxide in this catalytic system.

Recovery of cobalt from spent lithium ion batteries using sulphuric acid leaching followed by solid–liquid separation and solvent extraction

Abstract: Herein, the method of hydrometallurgy is adopted to recycle the precious metal cobalt in spent lithium ion batteries (LIBs). The best experimental conditions for leaching cobalt ions in sulphuric acid–hydrogen peroxide system are studied. The best leaching operation condition is an H2SO4 concentration of 3.0 mol L−1, liquid–solid ratio of 7 : 1 and hydrogen peroxide dosage of 1.6 mL g−1 for 2.5 h at 70 °C. Using the extraction characteristics of D2EHPA (di-(2-ethylhexyl) phosphoric acid) and PC-88A (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) for a specific ion in different pH value leaching solutions, the best experimental conditions are D2EHPA and PC-88A saponification rates of 20% and 30%, respectively, sulfonated kerosene volume of 70%, oil–water (O/A) ratio of 1 : 1, and extraction time of 10 min. Two extractions are applied, the first extraction occurs at pH 2.70 and the second extraction is done at pH 2.60 using D2EHPA to remove copper and manganese ions. After the extraction operation, PC-88A is used to further extract the leaching solution and maintain the pH at 4.25, so that cobalt and nickel ions are effectively separated, then cobalt ions are separated by oxalic acid and cobalt oxalate is obtained. The purity of cobalt is as high as 99.50%.