Peroxide Ions Research Articles

(Europe Section Alessandro Volta Medal) Alzheimer Disease and Oxidative Stress: Thou Shalt not Breathe nor Think!

Oxidative stress is an essential metabolic outcome in aerobic organisms due to the activity of mitochondria in providing the basic energy of cells or during the operation of several enzymatic pools (NADH-oxidases, NADPH-oxidases, NO-synthases, etc.) in recycling or producing important molecules. It also serves to regulate the size and shape of organs or restructure them during foetal development by apoptosis. The same occurs in organs (e.g., liver, bones) at the adult stage to control cell populations. Oxidative stress is also indispensable to the immune system by allowing macrophages to eliminate virus, bacteria and impaired or dead cells through phagocytosis. In fact, no aerobic organism could live without oxidative stress. Albeit these numerous benefits of oxidative stress explain why evolution maintain these essential mechanisms in aerobic organisms, they are associated to highly negative issues. Indeed, oxidative stress mechanisms provide a variety of life-harmful radicals and species called generically Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS) whose fluxes need to be finely controlled to avoid the destruction of most organic molecules (e.g., lipids in cell membranes, enzymes, etc.) and biological ones (DNA, proteins, etc.) in cells. Thus, under normal conditions, a panoply of dedicated antioxidants and specific enzymatic systems (e.g., superoxide dismutase, catalase, etc.) is present in cells and ensures a fine homeostatic balance. However, rupture of this delicate balance is frequent and may provoke severe damages in cells and tissues that are important causative factors in many human pathologies (aging, cancers, AIDS, hearth and brain strokes, Parkinson and Alzheimer’ diseases, etc.) when their rates of occurrence exceed the capabilities of repairing systems. All these important issues are well documented in medicine and biology but only through their long and middle terms outcomes in cells, tissues and organisms. However, investigations of the primary nature and effects of ROS and RNS remained impossible for long time because of the lack of analytical methods with adequate time and space resolutions. Using platinized carbon fiber ultramicroelectrodes positioned in an “artificial synapse” configuration we could establish that the so-called “oxidative stress cellular bursts” consist into the release of a reproducible cocktail involving a few femtomoles of hydrogen peroxide, nitric oxide, peroxynitrite and nitrite ions per cell. Our results have quantitatively confirmed that these species stem from the simultaneous and coupled initial production of superoxide and NO° by two separated pre-existing enzymatic pools: NADPH-oxidases (O2°-) and NO-synthases (NO°). The same methodology also allows a precise kinetic and analytical characterization of the nature of functional hyperemia, viz., of the fine-tuning mechanism coupling neuronal activity and local blood flux supply in the brain. Besides its functions in supplying oxygen, glucose, etc., to the active brain areas, this mechanism underlies the present imaging methods (f-IRM, PET scans) used in investigating the working brain or for medical purposes. We investigated this process on single stellate neurons from perfused rat cerebellum slices and could establish for the first time that active neurons signal their need for increased blood supplies by emitting pulses of locally important concentrations of NO° (up to 500 nM). These fluxes were shown to develop over ca 50 µm around the active neuron to induce the opening of vascular constrictions in nearby capillaries allowing them to deliver oxygen and nutrients to the active brain cells. This process is extremely intense but specifically tailored to only activate blood capillaries in the near vicinity of active neurons. Since neurons act cooperatively along chains, it is inferred that under normal physiological conditions, a whole brain area may be irrigated by larger blood flows while being active, which is precisely what is reported by f-IRM or PET-scans. Therefore, two fluxes (O2 and NO°) coexist in active parts of the brain. As such, this is not a problem. However, when free copper(II)-containing Amyloid-beta and ascorbate molecules are also present this ought to initiate a dangerous radical-chain process leading to the fast Cu(I)/Cu(II)-catalyzed production of protonated peroxynitrite (HO-ONO). This lipophilic species has enough stability to diffuse over several tens of a micrometer. When penetrating into neuron membranes, it spontaneously decomposes into OH° and NO2°. OH° leads to the fast creation of nanopores in the cell membrane, disrupting it and provoking apoptosis. We could fully establish the validity of this mechanism based on our analytical measurements and DFT investigations. Though overseen by the medical community, this mechanism may thus contribute to installing Alzheimer disease.

On hydrolysis of Ba–Bi–O and K–Ba–Bi–O oxide systems

Fundamentally different behavior of Ba–Bi–O (Ba : Bi = 11 : 4, 1 : 1, 2: 3, and 1 : 5 mol/mol) and K n Ba m Bi m+n O y (m = n = 1, 2,...; exhibiting superconducting properties with T c = 28–32 K) oxides and BaO2 in hydrolysis reactions has been revealed by means of potentiometry and chemical analysis. Products of the oxides treatment with water do not contain H2O2, evidencing the absence of peroxide ions in their structure. The perovskite-type barium-bismuth(III) oxides are completely hydrolyzed into Ba(OH)2 and Bi2O3 at room temperature.

Redox active and inactive binuclear cobalt(II) and zinc(II) complexes with N6O/N3O coordinating ligands: synthesis, biological activities and cytotoxicity

Four complexes, namely [Zn2L1(OAc)2](PF6) (1); [Zn2L1(OAc)2](BPh4) (2); [Co2L1Cl2](PF6) (3); and [Zn2L2(PhCOO)2Cl] (4) (L1 = 2,6‐bis(((2‐(dimethylamino)ethyl)(pyridine‐2‐ylmethyl)amino)methyl)‐4‐methoxyphenol; L2 = 2‐(((2‐(dimethylamino)ethyl)(pyridin‐2‐ylmethyl)amino)methyl)‐4‐methoxyphenol), have been synthesized. Single‐crystal diffraction reveals that the metal atoms in the four complexes are in different coordination environments. The interactions of the complexes with calf thymus DNA (CT‐DNA) have been investigated using UV absorption, fluorescence and circular dichroism spectroscopies and viscosity measurements, and the modes of CT‐DNA binding for the complexes have been proposed. Further experiments show that the Zn(II)/H2O2 system displays significant oxidative cleavage of supercoiled DNA attributed to the peroxide ion coordinated to the Zn(II) ions enhancing their nucleophilicity. This is a rare phenomenon. DNA cleavage mechanism shows that the complexes examined here may be capable of promoting DNA cleavage through an oxidative DNA damage pathway, which is indicative of the involvement of singlet oxygen in the cleavage process. In vitro cytotoxicity of complexes against three human tumor cell lines (HeLa, MCF‐7 and HepG2) demonstrates that these complexes have the potential to act as effective metal‐based anticancer drugs. Copyright © 2016 John Wiley & Sons, Ltd.

Inhibition of phagocytic activity of ARPE-19 cells by free radical mediated oxidative stress

Oxidative stress is a main factor responsible for key changes leading to the onset of age-related macular degeneration (ARMD) that occur in the retinal pigment epithelium (RPE), which is involved in phagocytosis of photoreceptor outer segments (POS). In this study, hydrogen peroxide (H2O2), H2O2 and iron ions (Fe) or rose Bengal (RB) in the presence of NADH and Fe were used to model free radical mediated oxidative stress to test if free radicals and singlet oxygen have different efficiency to inhibit phagocytosis of ARPE-19 cells. Free radical mediated oxidative stress was confirmed by HPLC-EC(Hg) measurements of cholesterol hydroperoxides in treated cells. Electron paramagnetic resonance (EPR) spin trapping was employed to detect superoxide anion. Cell survival was analyzed by the MTT assay. Specific phagocytosis of fluorescein-5-isothiocyanate-labeled POS and non-specific phagocytosis of fluorescent beads were measured by flow cytometry. HPLC analysis of cells photosensitized with RB in the presence of NADH and Fe indicated substantial increase in formation of free radical-dependent 7α/7β-hydroperoxides. EPR spin trapping confirmed the photogeneration of superoxide anion in samples enriched with RB, NADH and Fe. For all three protocols sub-lethal oxidative stress induced significant inhibition of the specific phagocytosis of POS. In contrast, non-specific phagocytosis was inhibited only by H2O2 or H2O2 and Fe treatment. Inhibition of phagocytosis was transient and recoverable by 24 h. These results suggest that free radicals may exert similar to singlet oxygen efficiency in inhibiting phagocytosis of RPE cells, and that the effect depends on the location where initial reactive species are formed.

Electrocatalytic Activities of Graphene/Nile Blue Nanocomposite Toward Determination of Hydrogen Peroxide and Nitrite Ion

AbstractElectrocatalytic activities of graphene nanosheets/Nile blue nanocomposite, synthesized and adsorbed simultaneously on the glassy carbon (GC−GNs−NB) electrode, are investigated. The nanocomposite was characterized by ATR−FTIR, FESEM and voltammetry. Activity of the electrode toward reduction of H2O2 and oxidation of NO2− was studied electrochemically. Values of 1.95 and 0.730 mM are found for the Michaelis−Menten constant of the electrode toward H2O2 and NO2−, respectively. Wide dynamic response ranges were observed for the electrode, with DLs of 0.22 μM H2O2 and 1.1 μM NO2−. Effect of interferences was studied. The sensor was successfully tested for H2O2 and NO2− contents in real samples, respectively.

Electrochemical behavior of a number of bispyridyl-substituted porphyrins and their electrocatalytic activity in molecular oxygen reduction reaction

The investigation of electrochemical properties of active layers containing 5,15-bis(pyrid-3-yl)-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphine, [5,15-bis(pyrid-3-yl)-3,7,13,17-tetramethyl-2,8,12, 18-tetraethylporphinato]cobalt(II), bispyridine[5,15-bis(pyrid-3-yl)-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphinato]cobalt(III), [5,15-bis(pyrid-4-yl)-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphinato]cobalt(II) and bispyridine[5,15-bis(pyrid-4-yl)-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphinato]cobalt(III) in 0.1 M KOH aqueous solution has been carried out by cyclic voltammetry. The potential ranges of redox processes related to the transformation of the porphyrin macrocycle, pyridyl substituents and central metal have been established. The electrochemical parameters of oxygen electroreduction reaction (the half-wave potential — E[Formula: see text](O[Formula: see text]), the maximum potential — E[Formula: see text](O[Formula: see text]), the current density — j, the activation energy — Eact) have been determined. It was shown that all porphyrins exhibit the catalytic activity. The electroreduction process of oxygen on electrode with the porphyrin-ligand occurs via 2-electron mechanism to give hydrogen peroxide ion HO2-, and on ones with the cobalt porphyrins — via parallel-sequential pathway including 2-electron and 4-electron processes to give HO2-, OH-. The presence of pyridine axial ligands in Co-complexes leads to a significant increase of the electrocatalytic activity in molecular oxygen reduction reaction.

Study of the Influence of the Operational Parameters on the Photo-Electro-Fenton Performance of an Industrial Waste-Water Treatment Prototype

A design of experiments (DOE) was used to characterize the influence of the operational parameters of an industrial prototype for waste-water treatment that was designed and built to operate using the Photo-Electro-Fenton technology. Since the approach under study is based on the photo-assisted Fenton reaction, which in turn is based on the production of hydroxyl radical species via electro-generated hydrogen peroxide (H2O2) and iron ions (Fe2+), the reaction was carried out in a prototype conceived in two reactor chambers. While in the first chamber hydrogen peroxide (H2O2) is produced via oxygen reduction using carbon cloth electrodes, the aqueous solution passes to a second chamber containing an iron-loaded resin in which a UV lamp promotes not only the oxidant species production but also iron reduction. The performance of the industrial prototype was followed by the absorbance decrease of a commercial dye aqueous solution ( (4-(2-Hydroxy-1-naphthylazo) benzene sulfonic acid, sodium salt, ≥98.0%) considering the applied current, the amount of iron-loaded resin, the flow rate and the pH as the operational variables to be characterized and eventually optimized for the operation of the prototype. In this way, a 24 factorial design was considered with two levels for each variable, central points and duplicate and randomized experiments. Variable interactions from the DOE were assessed using variance analysis and parameter estimation (ANOVA) using the statistical software JMP 7.0.2, SAS Institute Incorporated. The results revealed that the interactions for which the Prob >ltl being 0.05 or less are those corresponding to pH, resin and the pH-current-resin interaction parameters. From this information and the corresponding analysis it was possible to obtain an empirical equation that describes the reactor´s performance, along with a series of surface response curves that provide information on the relationship of the different operational variables that control the generation of oxidant species and the performance of the prototype under study.

Marine environmental protection: An application of the nanometer photo catalyst method on decomposition of benzene

Bioremediation is currently extensively employed in the elimination of coastal oil pollution, but it is not very effective as the process takes several months to degrade oil.Among the components of oil, benzene degradation is difficult due to its stable characteristics. This paper describes an experimental study on the decomposition of benzene by titanium dioxide (TiO2) nanometer photocatalysis. The photocatalyst is illuminated with 360-nm ultraviolet light for generation of peroxide ions. This results in complete decomposition of benzene, thus yielding CO2 and H2O. In this study, a nonwoven fabric is coated with the photocatalyst and benzene. Using the Double-Shot Py–GC system on the residual component, complete decomposition of the benzene was verified by 4h of exposure to ultraviolet light. The method proposed in this study can be directly applied to elimination of marine oil pollution. Further studies will be conducted on coastal oil pollution in situ.

Phase transitions in mayenite

This paper was devoted to explanation of the phase transitions nature in Ca12Al14O33±δ which were studied by a combination of methods: simultaneous thermal analysis, high-temperature X-ray diffraction analysis, Raman spectroscopy. One of the phase transitions is assumed to be connected with peroxide ions appearance/disappearance in mayenite at 922 K. The peroxide ions appearance reduces the system’s energy. Peroxide ions are responsible for the interaction of mayenite with water giving hydroxyl ions. Another phase transition at 1268 K is caused by changing in stability of electronic defects in mayenite. This paper enlightens correlations between the electronic defects state, the peroxide ions existence and chemical properties of Ca12Al14O33±δ.

Accessing alkali-free NASICON-type compounds through mixed oxoanion sol–gel chemistry: Hydrogen titanium phosphate sulfate, H1−xTi2(PO4)3−x(SO4)x (x=0.5–1)

We report a direct sol–gel synthesis and characterization of new proton-containing, rhombohedral NASICION-type titanium compounds with mixed phosphate and sulfate oxoanions. The synthetic conditions were established by utilizing peroxide ion as a decomposable and stabilizing ligand for titanyl ions in the presence of phosphates in a strong acidic medium. Thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), induction-coupled plasma optical emission spectroscopic (ICP-OES) elemental analysis, and Raman and 1H magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopic studies have determined the presence of sulfate and proton ions in the structure, for which the compositional range has been found to be H1−xTi2(PO4)3−x(SO4)x (x=0.5–1). The particulate products exhibit a nanocrystalline nature observed through characterization with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The N2 sorption isotherm measurements and subsequent Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) analyses confirmed the presence of the textural meso- and macropores in the materials. Future studies would determine the potential of the new compounds in various applications as battery materials, proton conductors and solid acid catalysts.

Simultaneous fluorescence visualization of mitochondrial hydrogen peroxide and zinc ions in live cells and in vivo.

We report simultaneous fluorescence imaging of hydrogen peroxide and zinc ions within mitochondria using two fluorescent probes termed M-H2O2 and M-Zn.

Neutrophil myeloperoxidase and its substrates: formation of specific markers and reactive compounds during inflammation.

Myeloperoxidase is an inflammatory enzyme that generates reactive hypochlorous acid in the presence of hydrogen peroxide and chloride ion. However, this enzyme also uses bromide ion or thiocyanate as a substrate to form hypobromous or hypothiocyanous acid, respectively. These species play important roles in host defense against the invasion of microorganisms. In contrast, these enzyme products modify biomolecules in hosts during excess inflammation, indicating that the action of myeloperoxidase is both beneficial and harmful. Myeloperoxidase uses other endogenous compounds, such as serotonin, urate, and l-tyrosine, as substrates. This broad-range specificity may have some biological implications. Target molecules of this enzyme and its products vary, including low-molecular weight thiols, proteins, nucleic acids, and lipids. The modified products represent biomarkers of myeloperoxidase action. Moderate inhibition of this enzyme might be critical for the prevention/modulation of excess, uncontrolled inflammatory events. Some phytochemicals inhibit myeloperoxidase, which might explain the reductive effect caused by the intake of vegetables and fruits on cardiovascular diseases.

Effects of bicarbonate and alpha-ketoglutarate on sensitivity of Saccharomyces cerevisiae yeast to hydrogen peroxide and iron ions

Effects of bicarbonate and alpha-ketoglutarate on sensitivity of Saccharomyces cerevisiae yeast to hydrogen peroxide and iron ions

Methane activation by gold-doped titanium oxide cluster anions with closed-shell electronic structures.

The reactivity of closed-shell gas phase cluster anions AuTi3O7- and AuTi3O8- with methane under thermal collision conditions was studied by mass spectrometric experiments and quantum chemical calculations. Methane activation was observed with the formation of AuCH3 in both cases, while the formation of formaldehyde was also identified in the reaction system of AuTi3O8-. The cooperative effect of the separated Au+ and O2- ions on the clusters induces the cleavage of the first C-H bond of methane. Further activation of the second C-H bond by a peroxide ion O22- leads to the formation of formaldehyde. This study shows that closed-shell species on metal oxides can be reactive enough to facilitate thermal H-CH3 bond cleavage and the subsequent conversion.

Oxidative consequences of UV irradiation on isolated milk proteins: Effects of hydrogen peroxide and bivalent metal ions

β-Casein (β-CN), β-lactoglobulin (β-LG), and α-lactalbumin (α-LA), were subjected to UV irradiation, alone or in the presence of hydrogen peroxide, hydrogen peroxide plus copper, or iron. Disappearance of tryptophan (Trp) was fastest for α-LA and slowest for β-CN. Hydrogen peroxide accelerated loss of Trp, while addition of iron did not further increase the speed of Trp reduction, but the addition of copper did. Oxidation products were higher for β-CN than for β-LG following UV irradiation alone or in the presence of hydrogen peroxide or hydrogen peroxide plus iron. In the presence of copper, oxidation rates were similar for both proteins. UV photo-oxidation caused the loss of the native polypeptides, the rate of this being faster for β-LG than for β-CN. These results are compatible with the concept that formation of dityrosine and N-formylkynurenine were favoured by mobility in the native protein.

Oxidation of captopril by hydrogen peroxide and peroxomonosulfate ion catalyzed by a ruthenium(III) complex: kinetic and mechanistic studies

The complex [RuIII(edta)(H2O)]− (edta4− = ethylenediaminetetraacetate) catalyzes the oxidation of captopril (CapSH) using primary oxidants, hydrogen peroxide (H2O2) and peroxomonosulfate (\( {\text{HSO}}_{5}^{ - } \)). The kinetics of the oxidation reaction were studied as a function of both oxidant (H2O2, \( {\text{HSO}}_{5}^{ - } \)) and substrate (CapSH) concentrations using stopped-flow and rapid scan stopped-flow techniques. Spectral and kinetic data are suggestive of a pathway involving rapid formation of the intermediate complex [RuIII(edta)(CapS)]2− followed by direct attack of the oxidant (H2O2 or \( {\text{HSO}}_{5}^{ - } \)) at the S atom of the coordinated CapS−. ESI–MS and HPLC analysis of the reaction products showed that captopril disulfide (CapSSCap) is the major oxidation product. A probable mechanism in agreement with the spectral and kinetic data is presented.

Improved performance of Co-doped Li2O cathodes for lithium-peroxide batteries using LiCoO2 as a dopant source

We recently proposed a new battery system based on the redox of lithium peroxide (Li2O2)/lithium oxide (Li2O) at the cathode (lithium-peroxide battery system). In this system, the use of Li2O with cobalt ions partially substituted for lithium ions (Co-doped Li2O) is key to its realization. In this study, to further improve the cell performance, we prepare various Co-doped Li2O samples by a mechanochemical process using different cobalt source materials (e.g., LiCoO2, Co3O4, and CoO) and comparatively investigate them. Amongst the investigated cathode materials, the Co-doped Li2O sample prepared using LiCoO2 with a Co/(Co + Li) ratio of 0.09 exhibits the best performance. Monitoring of the pressure in the cell reveals that this Co-doped Li2O cathode can be charged to 270 mAh g−1 without O2 evolution involving its decomposition. Charge and discharge at 270 mAh g−1 is repeated more than 50 times. In addition, the rate-capability tests reveals that the redox reaction between peroxide and oxide ions is fast and that the cathode can be discharged at a high current density of 1000 mA g−1.

Radiation chemical behavior of aqueous butanal oxime solutions irradiated with helium ion beams

Samples of butanal oxime in aqueous solution have been irradiated with the helion (4He2+) beam of the ARRONAX (Nantes) and the CEMHTI (Orléans) cyclotrons. The consumption yield of butanal oxime has been measured by gas-chromatography coupled with mass spectrometry. Yields of gaseous products (mainly H2) have also been measured by micro-gas-chromatography. Butanal oxime can react with H∙ radicals by abstraction mechanism to enhance H2 production. Yields of liquid phase products (hydrogen peroxide and nitrite ion) have been measured by colorimetric methods. Butanal oxime acts as a scavenger of OH∙ radical to inhibit the production of H2O2. The observation of the radiolytic products allows then to discuss a degradation mechanism of butanal oxime in aqueous solutions.

Rate-determining elementary step of oxygen reduction reaction at (La,Sr)CoO3-based cathode surface

In order to give insight into the guiding principle of further improvement in surface reactivity of mixed-conducting cathode materials of solid oxide fuel cells, electrochemical impedance spectroscopy study was carried out on various LaCoO3- and (La,Sr)CoO3-based dense thin film electrodes with emphasis on the effect of oxygen partial pressure, Po2. The area specific conductivity corresponding to the surface reactivity, which is evaluated from the major impedance component appearing at low frequency range, shows a Po2-exponent of 1/2 irrespective of electrode material. After examining a series of possible elementary reaction steps in the oxygen reduction reaction, the universally observed Po2 dependence can be explained only by assuming that the rate-determining step is the reaction where surface bidentate peroxide ion reacts with an oxide ion vacancy in the cathode to yield two O− ions, one left at the surface and the other in the cathode interior. The origin of the minor impedance component often observed at higher frequency range is also discussed on the basis of its independence on Po2, which leads the authors to suggest that this impedance can be associated with the redox reaction between the surface O− and O2− in the cathode.

Selective Oxidation of Methionine and Tryptophan Residues in a Therapeutic IgG1 Molecule

Oxidation of methionine and tryptophan are common degradation pathways for monoclonal antibodies and present major analytical challenges in biotechnology. Generally, protein oxidation is detectable in stability and/or stressed samples (e.g., exposed to hydrogen peroxide, UV light, or metal ions). The induced chemical modifications may impact the biological activity of antibodies and may have biological consequences. However, these effects and the contribution of individual protein modifications are difficult to delineate as different amino acids are often oxidized simultaneously and accompanied by other degradants such as aggregates, especially in forced degradation studies. Here, we report a new method to obtain selective oxidation of methionine or tryptophan by using oxidation reagents combined with large excess of free tryptophan or methionine, correspondingly. More specifically, using hydrogen peroxide or tert-butyl hydroperoxide in combination with addition of free tryptophan allowed for selective oxidation of methionine. Conversely, the use of 2,2-azobis(2-amidinopropane) dihydrochloride in combination with free methionine resulted in selective tryptophan oxidation, whereas methionine oxidation was not significantly altered. This novel stress model system may prove to be valuable tool in future mechanistic studies of oxidative degradation of protein therapeutics.