Inorganic Peroxides Research Articles

Activation of inorganic peroxides with magnetic graphene for the removal of antibiotics from wastewater.

Magnetic graphene catalysts were prepared for the removal of antibiotics (sulfamethoxazole, norfloxacin, tetracycline and flumequine) from water. Different proportions of magnetite-graphene from 1:0 to 0:1 were considered to study the catalytic activation of inorganic peroxides, i.e. peroxymonosulfate (PMS), peroxydisulfate and hydrogen peroxide. The presence of graphene was mainly responsible for the activation, which was most effective in the presence of PMS. A ratio of 20% of magnetite in the solid was enough to achieve complete degradation of antibiotics with high recovery by application of a magnetic field. The performance of the catalyst was further evaluated in a simulated urban wastewater, studying the main parameters affecting the process and the stability in sequential reuses. The non-radical mechanism during the catalytic activation of PMS was hypothesized from kinetic scavenging probes tests. The electron transfer was suggested as the mechanism of the reaction from electron paramagnetic resonance analysis in the presence of D2O. The prepared magnetic catalyst showed high catalytic activity and stability to remove antibiotics from water.

Chemoreactive Nanotherapeutics by Metal Peroxide Based Nanomedicine.

The advances of nanobiotechnology and nanomedicine enable the triggering of in situ chemical reactions in disease microenvironment for achieving disease‐specific nanotherapeutics with both intriguing therapeutic efficacy and mitigated side effects. Metal peroxide based nanoparticles, as one of the important but generally ignored categories of metal‐involved nanosystems, can function as the solid precursors to produce oxygen (O2) and hydrogen peroxide (H2O2) through simple chemical reactions, both of which are the important chemical species for enhancing the therapeutic outcome of versatile modalities, accompanied with the unique bioactivity of metal ion based components. This progress report summarizes and discusses the most representative paradigms of metal peroxides in chemoreactive nanomedicine, including copper peroxide (CuO2), calcium peroxide (CaO2), magnesium peroxide (MgO2), zinc peroxide (ZnO2), barium peroxide (BaO2), and titanium peroxide (TiOx) nanosystems. Their reactions and corresponding products have been broadly explored in versatile disease treatments, including catalytic nanotherapeutics, photodynamic therapy, radiation therapy, antibacterial infection, tissue regeneration, and some synergistically therapeutic applications. This progress report particularly focuses on the underlying reaction mechanisms on enhancing the therapeutic efficacy of these modalities, accompanied with the discussion on their biological effects and biosafety. The existing gap between fundamental research and clinical translation of these metal peroxide based nanotherapeutic technologies is finally discussed in depth.

Solid peroxides in Fenton-like reactions at near neutral pHs: Superior performance of MgO2 on the accelerated reduction of ferric species

Fenton-like reactions at near neutral pHs are limited by the slow reduction of ferric species. Enhancing generation of ▪ from solid peroxides is a promising strategy to accelerate the rate-limiting step. Herein, the H2O2 release and Fenton-like reactions of four solid peroxides, MgO2, CaO2, ZnO2 and urea hydrogen peroxide (UHP), were investigated. Results indicated that UHP can release H2O2 instantly and show a similar behavior as H2O2 in the Fenton-like reactions. MgO2 released H2O2 quickly in phosphate buffered solutions, which was comparable to CaO2 but faster than ZnO2. Metal peroxides induced higher initial phenol degradation rates than UHP and H2O2 when the same theoretic H2O2 dosages and Fe(III)-EDTA were used. MgO2 displayed a superior performance for phenol degradation at pH 5, resulting in more than 93% phenol reduction at 1.5 h. According to kinetic analyses, the generation rate of ▪ in the MgO2 system was 18 and 3.4 times higher than those in ZnO2 and CaO2 systems, respectively. The addition of MgO2 significantly promoted H2O2 based Fenton-like reactions by increasing production of ▪, and the mixture of MgO2 and H2O2 had an improved utilization efficiency of active oxygen than the MgO2 system. The findings suggested the critical roles of metal peroxides in favoring Fenton-like reactions and inspired strategies to simultaneously accelerate Fenton-like reactions and improve utilization efficiency of active oxygen.

Thermal hazard analysis of inorganic peroxide initiators with varying water concentrations

Inorganic peroxide (IP) initiators are widely used as initiators in polymerization reactions. However, if IP initiators are in contact with water due to moisture or storage issues, they decompose and release large amounts of heat quickly that can cause severe fires and explosions. In this study, sodium persulfate and ammonium persulfate were selected to investigate the effects of water content on the thermal decomposition of IP initiators. Accelerating rate calorimetry (ARC) was used to quantitatively study the IP initiators reacting with different concentrations of water, and the thermal decomposition parameters were corrected to calculate the kinetic parameters. Thermokinetic models based on numerical simulations were implemented to evaluate the thermal hazard characteristics, with the time to maximum rate under adiabatic conditions and the self-accelerating decomposition temperature obtained. The results indicate that the effects of water on IP initiators must be taken into account during their production, transportation, and storage in order to prevent fires and explosions.

Comparative Study of Protective Action of Exogenous 2-Cys Peroxiredoxins (Prx1 and Prx2) Under Renal Ischemia-Reperfusion Injury.

The pathogenesis of ischemia-reperfusion (I/R) injuries is based on oxidative stress caused by a sharp increase in the concentration of free radicals, reactive oxygen species (ROS) and secondary products of free radical oxidation of biological macromolecules during reperfusion. Application of exogenous antioxidants lowers the level of ROS in the affected tissues, suppresses or adjusts the course of oxidative stress, thereby substantially reducing the severity of I/R injury. We believe that the use of antioxidant enzymes may be the most promising line of effort since they possess higher efficiency than low molecular weight antioxidants. Among antioxidant enzymes, of great interest are peroxiredoxins (Prx1–6) which reduce a wide range of organic and inorganic peroxide substrates. In an animal model of bilateral I/R injury of kidneys (using histological, biochemical, and molecular biological methods) it was shown that intravenous administration of recombinant typical 2-Cys peroxiredoxins (Prx1 and Prx2) effectively reduces the severity of I/R damage, contributing to the normalization of the structural and functional state of the kidneys and an almost 2-fold increase in the survival of experimental animals. The use of recombinant Prx1 or Prx2 can be an efficient approach for the prevention and treatment of renal I/R injury.

Synthesis, Characterization, and Reactivity of a Series of Homo‐ and Hetero‐dinuclear Complexes based on an Asymmetric FloH Ligand System

In a previous communication we reported the site‐directed generation of a heterodinuclear FeIIICuII complex (1) by using an asymmetric dinucleating ligand FloH. The iron(III) ion was introduced first on the preferential metal‐binding site of the ligand that led to the formation of the thermodynamically favored five‐membered chelate ring upon metal‐binding. Copper(II) was introduced in the next step. The stepwise metalation strategy reported previously has now been extended to synthesize a series of heterodinuclear FeIIIMII [M = Mn (2), Fe (3), Co (4), and Ni (5)] and FeIICuI (1a) as well as the homodinuclear CuICuI (6) complexes. The complexes were characterized by X‐ray crystallography (except for 1a and 6), and by a limited number of spectroscopic methods. Complex 1 with a labile solvent binding site at FeIII reacted with H2O2 to form a transient intermediate that showed reactivity typical of metal peroxide complexes. The metal centers in the complexes 2–5 are coordinatively saturated, and hence they showed no reactivity with H2O2. Complex 1a reacted with O2 via an intermolecular pathway to form a μ‐oxo bridged tetrameric complex 1b, which was structurally characterized. This is in contrast to the homodinuclear CuICuI and heme FeIICuI cores, which prefer an intramolecular pathway for O2 activation.

Influence of Bleach Activators in Removing Different Soils from Cotton Fabric

The influence of adding Sodium Perborate Tetrahydrate (NaPB) and tetraacetylethylenediamine (TAED) on the efficiency of removing soils from cotton fabric was evaluated in the study. NaPB as inorganic peroxide and TAED as a bleach activator were added to a commercial washing powder agent. Four standard soils applied on cotton fabric (EMPA standard soiled fabrics) were used in the study, i.e. 101 – carbon black/olive oil, 114 – red wine, 116 – blood/ milk/ink and 160 – chocolate. The washing of fabrics was conducted in accordance with the SIST EN ISO 105-C06 standard at 40, 60 and 90 °C in Launder-Ometer apparatus. The washing efficiency was evaluated by determining the CIE L* colour coordinates of the unwashed and washed fabric samples, and the difference in ΔL* colour coordinates among them. The results showed that NaPB and TAED improve the efficiency of washing for two standard soils, have no effect on one, and deteriorate the washing results of one standard soil.

Simple Method for the Assessment of Peroxiredoxin Activity in Biological Samples

Abstract The current study describes a simple spectrophotometric protocol for the assessment of peroxiredoxin (Prx) activity and demonstrates its reproducibility, accuracy, and precision. The dissociation of organic or inorganic peroxide represents the rate-limiting step for reactions regulated by the Prx enzyme. In the current protocol, Prx enzyme activity was assessed by incubating enzyme samples with 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer, containing suitable concentrations of the substrates, organic or inorganic peroxide and 1,4-dithio-DL-threitol (DTT). At the end of the incubation period, a solution containing sulfosalicylic acid (SSA) and ammonium ferrous sulfate was added to stop the enzymatic reaction. SSA acts as a ligand to link the ferric ion formed by the reaction between ferric ammonium sulfate (FAS) and residual peroxide, producing a maroon-colored ferrisulfosalicylate complex, which was spectrophotometrically measured at 500 nm. This method does not require the use of strong acids at high concentrations to stop the enzymatic reaction. Also, the novel method was validated against a Bland–Altman plot analysis of Prx activity using the thiocyanate method in matched samples. The comparison between the sulfosalicylate and thiocyanate methods resulted in a correlation coefficient equal to 0.9976, demonstrating that the novel sulfosalicylate method is on par with the reference method.

Magnetism-Vanishing Stabilizes the Pyrite-Type 3d Transition Metal Peroxides at High Pressures

Extensive AO2-type transition metal (TM) oxides are experimentally determined or theoretically predicted to adopt the pyrite-type (Pa3) structure at different pressures, but their physical and che...

A peroxiredoxin of Thermus thermophilus HB27: Biochemical characterization of a new player in the antioxidant defence

To fight oxidative damage due to reactive oxygen species (ROS), cells are equipped of different enzymes, among which Peroxiredoxins (Prxs) (EC 1.11.1.15) play a key role. Prxs are thiol-based enzymes containing one (1-Cys Prx) or two (2-Cys Prx) catalytic cysteine residues. In 2-Cys Prxs the cysteine residues form a disulfide bridge following reduction of peroxide which is in turn reduced by Thioredoxin reductase (Tr) /Thioredoxin (Trx) disulfide reducing system to regenerate the enzyme. In this paper we investigated on Prxs of Thermus thermophilus whose genome contains an ORF TT_C0933 encoding a putative Prx, belonging to the subfamily of Bacterioferritin comigratory protein (Bcp): the synthetic gene was produced and expressed in E. coli and the recombinant protein, TtBcp, was biochemically characterized. TtBcp was active on both organic and inorganic peroxides and showed stability at high temperatures. To get insight into disulfide reducing system involved in the recycling of the enzyme we showed that TtBcp catalically eliminates hydrogen peroxide using an unusual partner, the Protein Disulfide Oxidoreductase (TtPDO) that could replace regeneration of the enzyme. Altogether these results highlight not only a new anti-oxidative pathway but also a promising molecule for possible future biotechnological applications.

Synthesis, Iodometric Analysis, and IR Spectroscopy of the Peroxide Double Salt [Zn(NH3)4][Mo(O2)4

This paper describes an upper-division undergraduate exercise involving the synthesis and iodometric and infrared spectroscopic analysis of the peroxide double salt [Zn(NH3)4][Mo(O2)4]. Here, iodometric methods are employed to determine the peroxide content of the compound, a procedure widely used for the industrial analysis of peroxides. The exercise increases student proficiency in synthesis, the handling of reactive chemicals, and titrimetry, while introducing aspects of metal peroxide chemistry and key chemical concepts related to high-coordination number complexes, kinetic versus thermodynamic stability, and group theoretical treatments of vibration spectroscopy.

Unconventional stable stoichiometry of vanadium peroxide.

Peroxides have attracted considerable attention due to their intriguing electronic properties and diverse applications. However, only a few transition metal peroxides have been known thus far, limiting the variety of peroxide examples. Here, we demonstrate the stabilization of peroxides in the O-rich V-O system through first-principles calculations coupled with a swarm-intelligence structure search. As well as reproducing the known stoichiometries of VO, V2O3, VO2, and V2O5, two hitherto unknown V2O and VO4 stoichiometries are predicted to be thermodynamically stable at megabar pressures. VO4 has the highest oxygen content among the known peroxides to date. More interestingly, its electronic band gap increases with pressure, originating from the pressure-induced decrease of O-O bonding length in the peroxide group. V-rich V2O exhibits superconductivity, becoming the first example in the V-O system. Our work not only unravels the unusual vanadium peroxide, but also provides further insight into the diverse electronic properties of vanadium oxides under high pressure.

In-situ growth of magnesium peroxide on the edge of magnesium oxide nanosheets: Ultrahigh photocatalytic efficiency based on synergistic catalysis

Magnesium oxide (MgO) nanosheets and hydrogen peroxide (H2O2) are respectively employed as a photocatalyst and an oxidant to enhance the photocatalytic efficiency for photo-degradation of methylene blue (MB). During the photocatalytic process, highly-oxidizing magnesium dioxide (MgO2) is generated by reacting with H2O2 on the edge of MgO nanosheets, which is verified by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HR-TEM). The synergistic catalysis of H2O2, MgO2 (highly-oxidizing) and MgO (photocatalysis) has significantly improved the photocatalytic efficiency. The photocatalytic efficiency of MgO nanosheets with H2O2 under visible-light irradiation reaches 98.1%, which is 3.2 times greater than that without H2O2 under visible light (30.5%). Moreover, the photocatalytic efficiency is comparable with that of traditional photocatalysts, such as titanium dioxide (TiO2), graphitic carbon nitride (g-C3N4), etc. This study indicates that the synergistic effect of the homologous oxide catalyst (MgO) effectively improves photo-degradation efficiency via in-situ generating a highly-oxidizing metal peroxide (MgO2) during the photocatalytic process.

Near-Surface Layer during the Heterogeneous Heterophase Oxidation of Metals and Alloys and the Related Chemical and Technological Aspects

In many cases, when metals and alloys are oxidized under the continuous regeneration of the direct oxidant taken in the amounts comparable with catalytic amounts, the near-surface layer of surface deposits of the products of oxidation of the metal and the reduction of the oxidant of the metal can be considered as a local zone of the macrocyclic stage of regeneration of the oxidant of the metal. The transfer of this stage to the volume phase is admissible and sometimes reasonable if the product of the reduction of the direct oxidant of the metal is soluble in the volume phase to a sufficient extent and the metal oxide is almost insoluble in the volume phase, where the metal exists in a higher oxidation state, or metal peroxide is used as an oxidant. If the indicated solubility of the reduction product of the primary oxidant of the metal is too low or entirely absent, its transfer to the volume phase due to the mechanical failure of the near-surface layer results in progressive self-retardation and also, in many cases, in the nearly entire termination of the oxidation process. The facts of the presence and mechanical failure of the near-surface layer on the metal and alloy favorable from the viewpoint of chemistry and technology are considered.

Ab initioinsight into the formation of small polarons: A study across four metal peroxides

In this ab initio study, we investigate the initial stages of small polaron formation across four metal peroxides. By separating out electronic and lattice energy contributions to the formation of electron polarons, we find both large and small formation barriers directly correlated with an electronic relaxation delay. Further analysis of the electronic structure evolution during polaron formation, within the constraints set by the generalized form of Koopmans' theorem, reveals that hybridization between the polaron anchoring orbital and the conduction band minimum determines the electronic relaxation delay. This hybridization physics is shown to play a dominant role in the magnitude of a polaron formation barrier and the adiabaticity of polaron charge localization. Weaker hybridization is correlated with larger more diabatic formation barriers, while stronger hybridization is correlated with smaller more adiabatic formation barriers. These ab initio insights may lead to new approaches towards tailoring the formation of small polarons in energy and electronic materials.

Glutathione is Involved in Detoxification of Peroxide and Root Nodule Symbiosis of Mesorhizobium huakuii.

Legumes interact with symbiotic rhizobia to produce nitrogen-fixation root nodules under nitrogen-limiting conditions. The contribution of glutathione (GSH) to this symbiosis and anti-oxidative damage was investigated using the M. huakuii gshB (encoding GSH synthetase) mutant. The gshB mutant grew poorly with different monosaccharides, including glucose, sucrose, fructose, maltose, or mannitol, as sole sources of carbon. The antioxidative capacity of gshB mutant was significantly decreased by these treatments with H2O2 under the lower concentrations and cumene hydroperoxide (CUOOH) under the higher concentrations, indicating that GSH plays different roles in response to organic peroxide and inorganic peroxide. The gshB mutant strain displayed no difference in catalase activity, but significantly lower levels of the peroxidase activity and the glutathione reductase activity than the wild type. The same level of catalase activity could be associated with upregulation of the transcriptional activity of the catalase genes under H2O2-induced conditions. The nodules infected by the gshB mutant were severely impaired in abnormal nodules, and showed a nodulation phenotype coupled to a 60% reduction in the nitrogen fixation capacity. A 20-fold decrease in the expression of two nitrogenase genes, nifH and nifD, is observed in the nodules induced by gshB mutant strain. The symbiotic deficiencies were linked to bacteroid early senescence.

Inactivation of the Agrobacterium tumefaciens ActSR system affects resistance to multiple stresses with increased H2O2 sensitivity due to reduced expression of hemH.

The Agrobacterium tumefaciens ActSR two-component regulatory system is a member of a homologous group of global redox-responsive regulatory systems that adjust the expression of energy-consuming and energy-supplying metabolic pathways in order to maintain cellular redox balance. In this study, the transcriptional organization of the hrpB-actSR locus was determined and the effect of actSR system inactivation on stress resistance was investigated. It was found that hrpB is transcribed as a monocistronic mRNA and actS is transcribed along with actR as a bicistronic mRNA, while actR is also transcribed as a monocistronic message. Each message is initiated from a separate promoter. Inactivation of actR resulted in decreased resistance to membrane stress (sodium dodecyl sulfate), acid stress (pH 5.5), iron starvation (bipyridyl) and iron excess (FeCl3), and antibiotic stress (tetracycline and ciprofloxacin). Resistance to oxidative stress in the form of organic peroxide (cumene hydroperoxide) increased, while resistance to inorganic peroxide (H2O2) decreased. An actR insertion mutant displayed reduced catalase activity, even though transcription of katA and catE remained unchanged. Complementation of the actR inactivation mutant with plasmid-encoded actR or overexpression of hemH, encoding ferrochelatase, restored wild-type catalase activity and H2O2 resistance levels. Gel mobility shift and hemH promoter-lacZ fusion results indicated that ActR is a positive regulator of hemH that binds directly to the hemH promoter region. Thus, inactivation of the A. tumefaciens ActSR system affects resistance to multiple stresses, including reduced resistance to H2O2 resulting from a reduction in catalase activity due to reduced expression of hemH.

Peroxide impact on the fate of veterinary drugs in fertilizers

The presence of veterinary medicines in organic manure causes soil contamination which contributes to increasing resistance of indigenous microflora to drugs and results in greater susceptibility of people to allergies. The main aim of the study was to assess the efficiency of inorganic peroxide mixtures (PM) with calcium peroxide content (CaO2) in the stabilization process of manure contaminated with antiparasitic agents: albendazole (ALB) and levamisole (LEV). As a solid, CaO2 is relatively stable against decomposition. In contact with water, however, it hydrolyzes with release of oxygen. The hydrolyzation of CaO2 proceeds very slowly in soil, which guarantees the constant release of hydrogen peroxide that subsequently becomes the source of free radicals (chemical oxidation) and oxygen (aerobic conditions for the microbes). It may contribute to continuous elimination of drugs from manure. The study has demonstrated that there were significant differences in ALB and LEV conversion stimulated by the PM addition. PM supplementation increased the drug availability (on average 15% and 25% increase in the initial concentration for ALB and for LEV, respectively), thereby increasing the initial rate of reaction. Elimination of ALB and LEV from the manure sorption complex is followed by Ca2+ saturation. The initial degradation rate was affected by PM for both drugs, but the mechanisms of decomposition have been modified only for ALB. The loss of ALB in the peroxide supplemented samples was 92%, and in the samples, without the PM, it did not exceed 61%. Loss of LEV was over 90% irrespective of PM supplementation.Graphic abstract

Synthesis of Copper Peroxide Nanodots for H2O2 Self-Supplying Chemodynamic Therapy.

Chemodynamic therapy (CDT) employs Fenton catalysts to kill cancer cells by converting intracellular H2O2 into hydroxyl radical (•OH), but endogenous H2O2 is insufficient to achieve satisfactory anticancer efficacy. Despite tremendous efforts, engineering CDT agents with specific and efficient H2O2 self-supplying ability remains a great challenge. Here, we report the fabrication of copper peroxide (CP) nanodot, which is the first example of a Fenton-type metal peroxide nanomaterial, and its use as an activatable agent for enhanced CDT by self-supplying H2O2. The CP nanodots were prepared through coordination of H2O2 to Cu2+ with the aid of hydroxide ion, which could be reversed by acid treatment. After endocytosis into tumor cells, acidic environment of endo/lysosomes accelerated the dissociation of CP nanodots, allowing simultaneous release of Fenton catalytic Cu2+ and H2O2 accompanied by a Fenton-type reaction between them. The resulting •OH induced lysosomal membrane permeabilization through lipid peroxidation and thus caused cell death via a lysosome-associated pathway. In addition to pH-dependent •OH generation property, CP nanodots with small particle size showed high tumor accumulation after intravenous administration, which enabled effective tumor growth inhibition with minimal side effects in vivo. Our work not only provides the first paradigm for fabricating Fenton-type metal peroxide nanomaterials, but also presents a new strategy to improve CDT efficacy.

OhsR acts as an organic peroxide-sensing transcriptional activator using an S-mycothiolation mechanism in Corynebacterium glutamicum

BackgroundCorynebacterium glutamicum is a well-known producer of various l-amino acids in industry. During the fermenting process, C. glutamicum unavoidably encounters oxidative stress due to a specific reactive oxygen species (ROS) produced by consistent adverse conditions. To combat the ROS, C. glutamicum has developed many common disulfide bond-based regulatory devices to control a specific set of antioxidant genes. However, nothing is known about the mixed disulfide between the protein thiol groups and the mycothiol (MSH) (S-mycothiolation)-based sensor. In addition, no OhrR (organic hydroperoxide resistance regulator) homologs and none of the organic hydroperoxide reductase (Ohr) sensors have been described in the alkyl hydroperoxide reductase CF-missing C. glutamicum, while organic hydroperoxides (OHPs)-specific Ohr was a core detoxification system.ResultsIn this study, we showed that the C. glutamicum OhsR acted as an OHPs sensor that activated ohr expression. OhsR conferred resistance to cumene hydroperoxide (CHP) and t-butyl hydroperoxide but not H2O2, hypochlorous acid, and diamide; this outcome was substantiated by the fact that the ohsR-deficient mutant was sensitive to OHPs but not inorganic peroxides. The DNA binding activity of OhsR was specifically activated by CHP. Mutational analysis of the two cysteines (Cys125 and Cys261) showed that Cys125 was primarily responsible for the activation of DNA binding. The oxidation of Cys125 produced a sulfenic acid (C125-SOH) that subsequently reacted with MSH to generate S-mycothiolation that was required to activate the ohr expression. Therefore, OhsR regulated the ohr expression using an S-mycothiolation mechanism in vivo.ConclusionThis is the first report demonstrating that the regulatory OhsR specifically sensed OHPs stress and responded to it by activating a specific ohr gene under its control using an S-mycothiolated mechanism.