Presence Of Hydroxyl Radicals Research Articles

Hydroxyl radical oxidation of chemical contaminants on indoor surfaces and dust

Humans are widely exposed to semivolatile organic contaminants in indoor environments. Many contaminants have long lifetimes following partitioning to the large surface reservoirs present indoors, which leads to long exposure times to gas-phase oxidants and multiphase chemistry. Studies have shown selective multiphase oxidation of organics on indoor surfaces, but the presence of hydroxyl radicals with nonselective reactivity and evidence of multiphase OH radical reactivity toward common indoor contaminants indicates that there may be additional unknown transformation chemistry indoors. We screened genuine indoor samples for 60 OH radical oxidation products of the common plasticizer and endocrine-disrupting contaminant bis(2-ethylhexyl) phthalate (DEHP) identified in laboratory experiments using nontargeted high-resolution mass spectrometry. At least 30 and 10 of these products are observed in indoor dust and DEHP films exposed to ambient indoor conditions, respectively, indicating that multiphase OH reactions occur indoors. Using the PROTEX model and a multimedia indoor chemical fate model, we demonstrate that these products have long indoor lifetimes and cause a higher potential for human exposure than DEHP. Some of these products are more active endocrine disruptors than DEHP itself, but most have unknown toxicities. Coexposure to all oxidation products will likely have an additive effect, leading to higher human health risks from indoor organic contaminants than previously thought. Due to the nonselective reactivity of OH radicals, it is likely that most indoor contaminants follow similar chemistry, and further study is needed to understand the prevalence and human health implications of such multiphase chemistry.

Photochemical fate of nonionic polyacrylamide induced by hydroxyl radicals in the natural water: Mineralization mechanism exploration and half-life time evaluation

Water-soluble polyacrylamide (PAM) compounds have been used extensively in various sectors. The abundance of PAM in the environment raises concerns about its environmental impact. However, the mineralization of PAM in water under natural light irradiation remains insufficiently explored. This study utilizes nonionic PAM (nPAM) as a representative model to investigate both the mechanism and efficiency of nPAM degradation in water when exposed to ultraviolet (UV) light with hydrogen peroxide (H2O2) as the hydroxyl radical source. In the dark or with only UVA irradiation, negligible mineralization of nPAM occurred. In contrast, the presence of hydroxyl radicals (produced by the UVA/H2O2 system) produced 50 % nPAM mineralization over 7 days under our experimental conditions. The corresponding molecular weight (MW) of the nPAM was swiftly reduced from 1.58 ×106 Da to 1.59 ×103 Da in 3 days. Moreover, five carboxylic acids and nitrate ions were identified as the photodegradation intermediates of nPAM. The efficiencies of nPAM photodegradation by the UVA/H2O2 system in different natural waters and environmental conditions were assessed. The rate constant for the reaction between the hydroxyl radical and nPAM was 2.17 ×109 M-unit−1 s−1. The half-lives of nPAM in the sea and continental surface waters were determined to be several years and dozens of days, respectively. The application of UVB obviously accelerated the mineralization of nPAM in ultrapure water (71 % degradation in 7 days). Moreover, mineralization of concentrated nPAM (200 mg/L) in sea water was more efficient when both UVA- and UVB-activated H2O2 were used. Additionally, toxic acrylamide was not generated during nPAM photodegradation. Moreover, the photodegradation intermediates from nPAM were found to be neither acutely nor chronically toxic to aquatic organisms. This comprehensive study sheds light on the photochemical fate of nPAM in natural waters and provides essential insight for practical treatment of PAM in water systems.

Effectively accelerated degradation of bisphenol A in Fe3O4/PMS system by caffeic acid

Bisphenol A (BPA) is an endocrine disruptor widely used in industry and the increased incidence of many cancers has been shown to be related to their exposure. Effective removal of BPA is causing concern. In this article, it was found that the introduction of caffeic acid (CFA) might significantly improve BPA degradation in Fe3O4/PMS system. The use of Fe3O4/CFA/PMS system offers a number of advantages compared to previously used homogeneous systems, including a wider pH range for application, ease of production, and minimal biotoxicity. Based on the analysis and discussion of the experimental data, it is clear that BPA can be almost completely degraded within 40 minutes under the most efficient conditions of 0.4 mM PMS, 0.5 g/L Fe3O4, and 0.05 mM CFA. BPA was successfully removed over a broad pH range of 3.0–9.0. Due to the presence of reactants in different states, the inhomogeneous system is less significantly disturbed by H+ and OH- compared to the homogeneous system. The presence of Cl-, HCO3-, NO3- and humic acid influences the removal of BPA. The intermediate product (benzoquinone) of CFA was found to be involved in the reaction and effectively promoted the recycling of Fe(II) and Fe(III). By the formation of CFA-Fe chelates, the reducing and chelating ability of CFA accelerates Fe(III)/Fe(II) cycling and thus promotes the activation of PMS. Ethanol scavenging studies and chemical probe experiments showed that the presence of hydroxyl radicals (HO·), sulphate radicals (SO4．-) and singlet oxygen (1O2) plays a role in the elimination of BPA in Fe3O4/CFA/PMS system. The contribution rate is found to be SO4．->HO·>1O2. The current research provides a low-cost, environmentally friendly method to remove BPA.

Design of FeWO4@N-TiO2 nanocomposite and its enhanced photocatalytic activity in decomposing methylene blue and phenol under visible light

Effluents from textile industries contain high levels of methylene blue (MB) and phenol from other industries, which are serious health hazard and a threat to biodiversity as well as the environment. Nitrogen (N) doped TiO2 modified by iron tungstate (FeWO4) composite photocatalyst (FeWO4 @N-TiO2) working under visible light (λ ≥ 420 nm) could be a suitable candidate to degrade this pollutant. X-ray diffractometry (XRD) and X-ray Photoelectron Spectroscopy (XPS) study suggested that the N was introduced as substitutional doping into TiO2 lattice which leads to narrowing band gap of TiO2 nanoparticles. The prepared FeWO4 @N-TiO2 was utilized to measure efficiency in decomposing the methylene blue (MB) and phenol in aqueous phase under visible light (λ ≥ 420 nm) irradiation. The FeWO4 @N-TiO2 showed better catalytic efficiency to degrade MB and phenol in several compositions of FeWO4. The composite demonstrated 77% and 85% removal of MB and phenol from aqueous medium after 2 h of visible light illumination, respectively. Interestingly, radical-hole hunting identifying tests indicated the presence of hydroxyl radical (°OH) in the photocatalytic decomposition reaction medium. The higher efficiency of FeWO4 @N-TiO2 was originated from absorption of visible energy as well as the relative energy band positions of the components FeWO4 and N-TiO2. Thus, photoexcited electron (e‾) and hole (h+) could take part by inter-particle transfer through the formation of °OH radical which was experimentally confirmed and a photocatalytic reaction mechanism has been proposed to mineralize organics.

Catalytic Ozonation of Tartrazine Dye Wastewater Using NiAl2O4/NiO@γ-Al2O3: Catalyst Preparation and Performance

ABSTRACT In this study, a novel NiAl2O4/NiO@γ-Al2O3 catalyst was prepared by the impregnation-calcination method and used for the catalytic ozonation of tartrazine wastewater. The NiAl2O4/NiO@γ-Al2O3 catalyst were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption experiments. It was found that NiAl2O4/NiO@γ-Al2O3 significantly improved the removal of chemical oxygen demand of the dye wastewater from 40% for the direct ozone oxidation to 65%, and the ozone concentration depletion for catalytic ozonation was 120% of that for ozone alone. The catalytic activity of the catalyst did not significantly decrease after reuse for six cycles and leaching concentration of metal ions less than 1%. However, the toxicity of the dye wastewater was greatly reduced after the catalytic ozonation. The pyridine Fourier transform infrared spectroscopy showed the catalytic ozonation reaction was related with Lewis acid sites. The presence of hydroxyl radicals, superoxide anion radicals, and singlet oxygen was verified by an electron paramagnetic resonance, and the quenching experiments confirmed that the removal of organic pollutants from the tartrazine wastewater mainly relied on hydroxyl radicals and singlet oxygen. Therefore, the NiAl2O4/NiO@γ-Al2O3 could be an effective catalyst for the rapid catalytic ozonation of dye wastewater.

Ultrasonic-assisted synthesis of TiO2/MWCNT/Pani nanocomposite: Photocatalyst characterization and optimization of efficient variables in the degradation of benzene via RSM-CCD

Nowadays, volatile organic compounds (VOCs) are the primary cause of rising contamination in groundwater, surface water, and wastewater. On the other hand, photocatalysis technology is among the best ways to treat wastewater because of its ability to rapidly mineralize a range of pollutants into non-toxic chemicals using sunlight as an energy source and its ecological friendliness. Herein, the TiO2/MWCNT/Pani nanocomposite was synthesized by combining ultrasonic and in-situ polymerization methods to decompose benzene, a prevalent and harmful VOC. The nanocomposite was characterized by XRD, FTIR, BET, SEM, and UV–Vis analysis. The response surface methodology (RSM), based on Central Composite Design (CCD), was used to investigate and optimize the effects of the independent factors on photocatalytic degradation, including initial benzene concentration, catalyst dosage, pH, and light irradiation time. The optimal conditions (benzene concentration = 700 mg. L−1, pH = 6, irradiation time = 80 min, and photocatalyst dosage = 1.5 g. L−1) resulted in maximum benzene degradation (84.90%). Trapping test and EPR analysis were also utilized to detect reactive species, and the findings indicated that the breakdown of benzene through photocatalysis is caused by the presence of hydroxyl radicals (•OH) and superoxide radicals (•O2−). Furthermore, the kinetics of the reaction and the stability of the nanocomposite (4 cycles) were examined. Finally, the results of this study provide convincing evidence for using TiO2/MWCNT/Pani as highly efficient and promising photocatalysts for removing benzene from aqueous solutions.

Determining Conditions for the Fenton Reaction through Spectroscopy of FeSCN2+ and Methyl Orange

Exposure to radiation can lead to the breakdown of water into reactive oxygen species (ROS), such as hydroxyl radicals (OH·), through a process called radiolysis. The presence of hydroxyl radicals (OH·) and other ROS can cause mutations to DNA in the human body. While hydrogen peroxide (H₂O₂), a product of radiolysis, may not be a strong ROS on its own, it can react with certain metal ions such as iron(II) to produce hydroxyl radicals in a process called the Fenton reaction. This study investigates the optimal conditions for the Fenton reaction using a cost-effective spectroscopic analysis of ferric thiocyanate and degradation of methyl orange to detect the presence of Fe3+ and OH·. Understanding conditions and methods of detection for the Fenton reaction is relevant due to the carcinogenic nature of the hydroxyl radicals produced (Kumar et al., 2021). The results of the spectroscopic analysis suggest that the Fenton reaction occurs ideally in acidic environments (p = 0.00354) with low temperature dependence. Additionally, both spectroscopic methods are effective for detecting the efficiency of Fenton processes. This study provides valuable insights for future research on the Fenton reaction and its potential applications.

Natural Antioxidants and Tissue Inflammation

The phenolic compounds present in food cover a wide range of structures that have different biological properties. Highlighting its antioxidant properties and the presence mainly of spices, herbs and other foods. Some compounds present in spices can be listed for their antioxidant activity, such as: cloves have eugenol, pinene in their composition, cinnamon also has eugenol, limonene, pinene, catechins and other phenolic compounds in their composition, anise has pinene, rutin, apigenin, oregano has apigenin, quercecin, rosmarinic, caffeic, p-coumaric acids, and others. Rosemary presents the carnosic, rosmarinic, caffeic and hydroxycinnamic. The tissue inflammatory process normally starts with the presence of free radicals that are associated with the oxidative process activated by reactive oxygen species represented by peroxides, superoxide ion, presence of hydroxyl radical, singlet oxygen, among others. The highlighted phenolic compounds have in their structure one or more hydroxyls that have the property of donating a hydrogen atom to free radical structures, which can block the triggering of the oxidative process and thus inflammation.

Heterostructured Au@Pt/Nb2C-MXene nanocomposite as a colorimetric sensor with peroxidase-like activity for reactive oxygen species of H2O2

Bioinspired nanozymes based on two-dimensional (2D) transition metal carbide nanosheets are receiving attention because of their peroxidase-mimicking catalytic applications in bioanalysis. Herein, we report the Nb2C/Au@Pt nanocomposite-based heterostructured nanozymes for the detection of reactive oxygen species in a biological environment. The nanocomposites were fabricated by decorating 2D Nb2C-MXene with Au@Pt core–shell nanoparticles via interfacial electrostatic attraction between the transition metal carbide and noble metals. The nanocomposites were characterized using field emission scanning electron microscope, X-ray diffraction, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV–vis absorption spectroscopy, and zeta potential. The Nb2C-MXene with inherent electron and photothermal effects exhibited enhanced surface plasmon properties when adorned with Au@Pt. The Nb2C/Au@Pt nanocomposites demonstrated a synergistically enhanced peroxidase-like activity and efficiently catalyzed the 3,3′,5,5′-tetramethylbenzidine (TMB) reaction in the presence of hydroxyl radicals using H2O2. The Michaelis-Menten kinetics measurements revealed high catalytic activity of Nb2C/Au@Pt nanocomposites for TMB. Accordingly, a suitable label-free colorimetric sensing platform was established, considering an inhibitory effect on the specific detection of H2O2 in a linear range of 0.3–2.75 M. This study presents an effective strategy to design and fabricate MXene-based peroxidase-like nanozymes and demonstrates their potential in the fields of catalysis and biomedicine.

Development of a novel ReaxFF reactive potential for organochloride molecules.

This article presents a new reactive potential in the ReaxFF formalism. It aims to include the chlorine element and opens up the fields of use of ReaxFF to the whole class of organochloride compounds including conjugated or aromatic groups. Numerous compounds in this family raise global awareness due to their environmental impact, and such a reactive potential will help investigate their degradation pathways. The new force field, named CHONCl-2022_weak, belongs to the aqueous branch. The force field parameters were fitted against high-level quantum chemistry calculations, including complete active space self-consistent field/NEVPT2 calculations and density functional theory calculations, and their accuracy was evaluated using a validation set. The root means square deviation against quantum mechanics energies is 0.38eV (8.91kcal mol-1). From a structural point of view, the root means square deviation is about 0.06 Å for the bond lengths, 11.86° for the angles, and 4.12° for the dihedral angles. With CHONCl-2022_weak new force field, we successfully investigated the regioselectivity for nucleophilic or electrophilic attacks on polychlorinated biphenyls, which are toxic and permanent pollutants. The rotation barriers along the bond linking the two benzene rings, which is crucial in the toxicity of these compounds, are well reproduced by CHONCl-2022_weak. Then, our new reactive potential is used to investigate the chlorobenzene reactivity in the presence of hydroxyl radicals in atmospheric condition or in aqueous solution. The reaction pathways computed with ReaxFF agree with the quantum mechanics results. We showed that, in the presence of dioxygen molecules, in atmospheric condition, the oxidation of chlorobenzene likely leads to the formation of highly oxygenated compounds after the abstraction of hydrogen radicals. In water, the addition of a hydroxyl radical leads to the formation of chlorophenol or phenol molecules, as already predicted from plasma-induced degradation experiments.

Influence of acid-base equilibria on the rate of the chemical reaction in the advanced oxidation processes: Coumarin derivatives and hydroxyl radical

The decomposition and chemical manipulation of stable aromatic pollutants into less toxic products is an important topic for wastewater management and natural water remediation. The mechanism of the Advanced Oxidation Process (AOPs) of 4,7-dihydroxycoumarin (4,7-DHC) and 7-hydroxycoumarin (7-HC), as examples of stable naturally-occurring industrially-important compounds, in the presence of hydroxyl radical (HO) in the aqueous solution has been analyzed using Electron Paramagnetic Resonance spectroscopy (EPR) and Quantum Mechanics-based test for Overall Free Radical Scavenging Activity (QM-ORSA). The effect of pH values of the medium on the investigated reaction mechanisms has been fully investigated. The rate constants were estimated by the conventional transition state theory (TST) and Eckart's method (ZCT_0). Estimated values of the overall rate constant (koverall) higher than >4.06 × 109 M−1 s−1 at all pH values showed that both compounds undergo a chemical transformation when exposed to HO. When pH increased in the range of 0–14, the koverall increased from 4.06 × 109 to 1.11 × 1010 (4.7-DHC) and 2.09 × 109 to 1.76 × 1010 M−1s−1 (7-HC). At physiological pH = 7.4 value, 7-HC was ∼1.5 times more prone to radical action, as shown by EPR and QM-ORSA, due to the dominant anionic form. Both compounds were more reactive towards HO than Trolox at this pH value. The ecotoxicity assessment of the starting compounds, intermediates and oxidation products indicated that the formed products show lower acute and chronic toxicity effects on aquatic organisms than starting compounds, which is a prerequisite for the development of novel AOPs procedures.

Continuous Fe(II)-dosing scheme for persulfate activation: Performance enhancement mechanisms in a slurry phase reactor

Mechanisms involved in the superior performance of the continuous Fe2+ dosing scheme over the single Fe2+ dosing scheme was thoroughly investigated. The kinetics and stoichiometry of the phenol removal/persulfate consumption strongly depended on the volumetric or molar Fe2+ feeding rate, Fe2+ concentration in the feed solution, and Fe2+ feeding mode (continuous or single dose). The process performance was determined by the molar Fe2+ feeding rate rather than the volumetric Fe2+ feeding rate or the Fe2+ concentration in the feed solution. The phenol degradation rate increased as the molar Fe2+ feeding rate increased to 2.77 mmol/min but decreased as the Fe2+ feeding rate increased further. The sulfate radical was predominant radical species formed in continuous Fe2+ dosing mode. The hydroxyl and sulfate radicals were both important in single Fe2+ dose mode. The presence of hydroxyl radicals in single Fe2+ dosing mode decreased the amount of phenol oxidation that occurred, probably because the hydroxyl radicals were readily scavenged by soil organic matter. Continuous Fe2+ dosing facilitated phenol mineralization, which was indicated by total organic carbon measurements and toxicity tests performed using Hyalella azteca.

Metal-ligand cooperation in the catalytic oxidation of (R)-carvone by Ga(NO3)3/H2O2

In this work, the catalytic epoxidation of (R)-carvone by the Ga(NO3)3/H2O2 system was studied alongside the metal-ligand cooperation by exploring 17 different ligands. It was observed that the acidic ligands such as acetic acid mostly favor the epoxidation of the endocyclic double bond of (R)-carvone (22% yield, 1 h), while nitrogen heterocycles direct the epoxidation to the exocyclic double bond, especially the ones that are unsubstituted or have electron-donating groups, such as pyrazine (28% yield, 5 h), 4-dimethylaminopyridine (28% yield, 8 h), and 1-methyimidazole (43% yield, 8 h). Pyrazinecaboxylic acid favored the epoxidation of the exocyclic double bond (25%, 3 h). EPR analysis of both Ga(NO3)3/H2O2 and Ga(NO3)3/PCA/H2O2 systems indicates the presence of hydroxyl radicals in the reaction medium, although these do not determine the epoxidation rate that is likely regulated by the interaction of Ga-peroxo complexes with (R)-carvone. This study contributes to widening the application of the cooperating ligand concept in molecular catalysis toward further development of more selective and efficient epoxidation reactions catalyzed by non-transition metal centers.

Comparative study of ozonation and ozonation catalyzed by Fe-loaded biochar as catalyst to remove methylene blue from aqueous solution

Ozone-based processes gained much attention in recent years. However, due to low oxidative stability and utilization rate, single ozonation process (SOP) is insufficient for complete mineralization of pollutants. As a result, the single ozonation process is performed in the presence of a catalyst, a process known as catalytic ozonation process (COP). A promising catalyst (Fe/BC) was prepared by impregnating iron on biochar surface to remove methylene blue from aqueous solution via heterogeneous catalytic ozonation process (HCOP). The prepared Fe/BC features were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller method (BET) before and after HCOP. Furthermore, the effect of various operating parameters such as ozone dose, catalyst dose, initial dye concentration, initial pH on the efficiency of SOP and HCOP were compared. In comparison to single ozonation process, the experimental study found that heterogeneous catalytic ozonation process has the highest efficiency. At pH 7.0, approximately 76% of methylene blue is removed during single ozonation process in 60 min. Heterogeneous catalytic ozonation process showed 95% methylene blue elimination from aqueous solution. The efficiency of heterogeneous catalytic ozonation process was decreased by 52% in the presence of hydroxyl radical (●OH) scavenger, indicating that hydroxyl is the major oxidant during heterogeneous catalytic ozonation process for the removal of methylene blue from aqueous solution. Fe/BC catalyst appears to have a lot of industrial promise, as well as the ability to remove methylene blue from aqueous solution via heterogeneous catalytic ozonation process.

Capture of Hydroxyl Radicals by Hydronium Cations in Water Microdroplets

AbstractDespite the high stability of bulk water, water microdroplets possess strikingly different properties, such as the presence of hydroxyl radicals (OH⋅) at the air–water interface. Previous studies exhibited the recombination of OH⋅ into H2O2 molecules and the capture of OH⋅ by oxidizing other molecules. By spraying pure water microdroplets into a mass spectrometer, we detected OH⋅ in the form of (H4O2)+ that is essentially OH⋅−H3O+, a hydroxyl radical combined with a hydronium cation through hydrogen bonding. We also successfully captured it with two OH⋅ scavengers, caffeine and melatonin, and key oxidation radical intermediates that bear important mechanistic information were seen. It is suggested that some previous reactions involving (H4O2)+ should be attributed to reactions with OH⋅−H3O+ rather than with the water dimer cation (H2O−OH2)+.

Antibiotics removal from aquaculture effluents by ozonation: chemical and toxicity descriptors

Antibiotics are often applied in aquaculture to prevent fish diseases. These substances can cause disturbances on receiving waters, when not properly eliminated from the aquaculture effluents. In this work, ozone (O3) was investigated as a possible oxidizing agent to remove fishery antibiotics from aquaculture effluents: florfenicol (FF), oxytetracycline (OTC), sulfadimethoxine (SDM), sulfamethoxazole (SMX), and trimethoprim (TMP). Batch experiments were performed using ultrapure water and aquaculture effluents spiked with a mixture of target antibiotics at relatively high concentrations (10 mg L-1 each). OTC, SMX and TMP were fully removed (< 30 min) regardless of the tested conditions, mainly by O3 direct attack. In contrast, FF was partially removed in 30 min (∼ 10 and 60%, in aquaculture effluents and ultrapure water, respectively), but only in the presence of hydroxyl radicals (HO•), the FF concentrations reaching levels below the detection limits in ultrapure water after 60 min. In the case of SDM, its degradation was highly influenced by the selected water matrix, but with removals always higher than 68%. In continuous-flow experiments applying more environmentally relevant antibiotic concentrations (100 ng L-1 each) and low O3 doses (1.5 mg L−1), ozonation highly removed (> 98%) all tested antibiotics from aquaculture effluents with a hydraulic retention time (HRT) of 10 min, except FF (68%). Although by-products were detected in treated samples, zebrafish (Danio rerio) embryotoxicity tests did not show a toxicity increase by applying this ozonation treatment. Ozonation is thus a possible solution to remove antibiotics from aquaculture effluents. Still, full-scale studies in aquaculture farms are needed, and generation of HO• may be favoured to readily oxidize the FF antibiotic.

The degradation of poloxamer 188 in buffered formulation conditions

Poloxamer 188 (P188) as a non-ionic surfactant is used in proteinaceous formulations to prevent protein adsorption to hydrophobic surfaces and unfolding at interfaces, preventing the formation of aggregates and particles. Its chemical intactness is crucial to the stability of drug products due to its protecting effects at interfaces. In order to identify and mitigate potential risks that might cause the degradation of P188 during the manufacturing process and storage, in the current work, the stability of P188 was investigated by forced degradation in buffered formulation conditions via oxidation and thermal stress conditions. The process of degradation was monitored through the dedicated liquid adsorption chromatography (LAC) with high sensitivity, and the degradants were characterized by high-resolution mass spectrometry. Results suggest that the vulnerability of P188 is largely related to the buffer conditions. Histidine promotes degradation in the presence of hydroxyl radicals but inhibits the degradation in the presence of H2O2 and alkyl radicals. In thermal stress conditions, histidine protects P188 from degradation at 40 °C, and activates its decay only at higher temperature, like 60 °C.

Remediation of PNP-contaminated groundwater using a modified CaO2/Fe(II) Fenton system: Reactive principles, degradation performance and potential pathways

Calcium peroxide (CP, CaO2), acting as a source of H2O2, was combined with Fe(II) to provide a novel modified Fenton system. The removal of p-nitrophenol (PNP) in groundwater as a model pollutant was investigated using this system while addressing effect of reagents on water quality, mechanism of reactive oxygen species formation, possible degradation pathways, impact of geochemistry and process parameters on the removal efficiency. The dissolved oxygen, oxidation-reduction potential, pH, electrical conductivity and H2O2 concentration in groundwater were all increased significantly due to the addition of CaO2 and Fe(II), especially in the early stage and under acidic conditions. Within 30 min, 96% of an initial 40 mg/L PNP contamination was removed using the optimum conditions, consisting of 250 mg/L CaO2, 50 mg/L Fe(II), an initial pH of 2.6, oscillation frequency of 170 rpm and temperature of 298 K. The batch experiments revealed that the initial pH and the Fe(II) and CaO2 concentrations all decisively affected removal efficiency, while the groundwater dynamics, temperature and illumination conditions had little effect. The presence of hydroxyl radicals (∙OH) and singlet oxygen (1O2) was confirmed by electron paramagnetic resonance spectroscopy. In addition, ∙OH quenching experiments indicated that the former rather than the latter played a major role in PNP removal. The generation of 1O2 in this system was also predicted by classical molecular orbital theory. These findings would provide useful technical support for the remediation of groundwater contamination.

Gut microbiota of bats: pro-mutagenic properties and possible frontiers in preventing emerging disease

Bats are potential natural reservoirs for emerging viruses, causing deadly human diseases, such as COVID-19, MERS, SARS, Nipah, Hendra, and Ebola infections. The fundamental mechanisms by which bats are considered “living bioreactors” for emerging viruses are not fully understood. Some studies suggest that tolerance to viruses is linked to suppressing antiviral immune and inflammatory responses due to DNA damage by energy generated to fly. Our study reveals that bats' gut bacteria could also be involved in the host and its microbiota's DNA damage. We performed screening of lactic acid bacteria and bacilli isolated from bats' feces for mutagenic and oxidative activity by lux-biosensors. The pro-mutagenic activity was determined when expression of recA increased with the appearance of double-strand breaks in the cell DNA, while an increase of katG expression in the presence of hydroxyl radicals indicated antioxidant activity. We identified that most of the isolated bacteria have pro-mutagenic and antioxidant properties at the same time. This study reveals new insights into bat gut microbiota's potential involvement in antiviral response and opens new frontiers in preventing emerging diseases originating from bats.

Synthesis, Spectral Characterisation and Pharmacological Studies on Co(II), Ni(II), Cu(II) and Zn(II) Bis-Schiff Base Complexes Derived From 4-hydroxybenzohydrazide

The transition metal(II) chelates were prepared by the reactions of bis-Schiff base ligands derived from 4-hydroxy benzohydrazide and isophthalaldehyde / o-phthaldehyde in 1:1 metal to ligand ratio. The formed ligands and their metal complexes have been investigated by the following spectroscopic tools i.e, elemental analysis, FT-IR spectra, molar conductance, 1H NMR, ESI-mass, electronic spectra, magnetic moments, ESR and thermal analyses. The low molar conductance values give the non- electrolytic nature of the metal(II) chelates. From that the spectroscopic observations of complexes having the molecular formula [M(Ln)2Cl2] (where M= Co(II), Ni(II), Cu(II) and Zn(II), n=1and 2) and act as tetradentate N2O2 donor sites of ligands. The docking results predicts that the protein with ligands having good interaction energy. All formed complexes have efficient antibacterial activity than ligand of tested pathogens. The mode of binding interaction of ct-DNA and Cu(II) complexes gives the intercalative binding with hypochromism shifts using electronic titrations method. In electrophoresis, cleavages of PUC18DNA to cleave effectively with Cu(II) complexes in the presence of hydroxyl radicals. The antioxidant assay of DPPH radical scavenging activity of tested compounds shows good results, when compared to ascorbic acid as standard. The anticancer MTT assay of Cu(II) complexes tested against MCF-7 cancerous cells gives the promising therapeutic activity.