The contamination of wastewater with organic pollutants and nitrogen compounds poses significant environmental challenges.The primary objective of wastewater treatment is the simultaneous denitrification and decarboni...The contamination of wastewater with organic pollutants and nitrogen compounds poses significant environmental challenges.The primary objective of wastewater treatment is the simultaneous denitrification and decarbonization of ammonia nitrogen and organics into harmless by-products.This study presents a novel method for the directional generation of chlorine radical species like·ClO and·Cl using electro-reactive membranes(EMs)known as RuO_(2)@PbO_(2)-M,which were fabricated using an electro-deposition coupled template approach.This method facilitates the rapid and efficient conversion of ammonia to nitrogen and concurrently reduces the chemical oxygen demand in the effluent.Our system achieved ultra-efficient simultaneous denitrification and decarbonization with minimal energy consumption in single-filtration mode,thereby eliminating the need for chemical precursors.We elucidate the formation pathway of·ClO and·Cl during the electrochemical oxidation process involving RuO_(2)@PbO_(2)-M,where·Cl generated from RuO_(2)reacts with·OH from PbO_(2)under hypochlorous acid conditions,thereby enhancing nitrogen and carbon removal.These findings highlight a novel electro-filtration and an innovative reactive membrane design for·ClO synthesis,which provides a new research framework for the concurrent removal of nitrogen and carbon,and offers a promising solution to enhance wastewater treatment efficiency.展开更多
The generation of reactive intermediates is a pivotal step during photocatalytic redox elimination of organic micropollutants in water.The UV/S(Ⅳ)-based water treatment system has garnered significant attention as an...The generation of reactive intermediates is a pivotal step during photocatalytic redox elimination of organic micropollutants in water.The UV/S(Ⅳ)-based water treatment system has garnered significant attention as an efficient advanced reduction process for pollutant abatement.However,as a reductive system,the conventional UV/S(Ⅳ)approach exhibits limited efficacy in removing electron-rich micropollutants.Our study uncovered that meso–tetrakis(4-chlorophenyl)porphyrin-Fe(Ⅲ)chloride(TPPFe,a typical iron(Ⅲ)porphyrin)catalyzed the conversion of SO_(3)^(2-)into SO_(3)^(·-)under UV365irradiation without generating of eaq-and H·,leading to the formation of diverse oxidizing species.Additionally,the introduction of TPPFe induced an absorption redshift,broadening the range of applicable UV wavelengths.An in-depth photocatalytic cycle mechanism for TPPFe^(Ⅲ)Cl-[TPPFe^(Ⅱ)Cl]-was introduced and verified by density functional theory(DFT)calculations.Furthermore,quantum chemistry calculations via transition state were conducted to assess the oxidizing reactivity of the reactive species with micropollutants.Both·OH and SO_(4)^(·-)demonstrate a strong propensity to react with carbamazepine(CMZ,a model micropollutant).Meanwhile,1O2exhibits a distinct reaction mechanism with CMZ.Consequently,the radical-and ^(1)O_(2)-mediated distinct degradation pathways were elucidated.This study provides an experimental/theoretical exploration of reactive intermediate generation and their interactions with CMZ,shedding valuable insights into the mechanisms of electron-shuttling photosensitizers catalyzing the UV/S(Ⅳ)oxidation process.展开更多
Objective: To observe the effect of acupuncture on blood oxygen free radical (OFR) and nitric oxide (NO) levels in the treatment of apoplectic sequelae. Methods: A total of 61 cases of apoplectic patients were subject...Objective: To observe the effect of acupuncture on blood oxygen free radical (OFR) and nitric oxide (NO) levels in the treatment of apoplectic sequelae. Methods: A total of 61 cases of apoplectic patients were subjected into this study and randomly divided into "JIN San Zhen" group (n=30) and control group (n=31). Blood lipid peroxidase (LPO), superoxide dismutase (SOD), glutathione peroxidase(GSH Px) and nitric oxide (NO) contents before and after acupuncture treatment were determined with radioimmunoassay. In both groups, acupuncture was given once daily, six times a week, with 4 weeks being a therapeutic course and with the interval between two weeks being a week, 3 courses all together. In "JIN San Zhen" group, acupoints of "JIN San Zhen" were used predominately, while in control group, scalp point Motor Sensory Area (MS 8) was used as the main point. Results: Self comparison showed that after 3 courses of treatment, in both groups, LPO and NO levels decreased significantly (P<0.05-0.01), SOD and GST Px values increased considerably (P<0.05-0.01). Comparison between two groups indicated that the effects of "JIN San Zhen" group are significantly superior to those of control group in raising blood SOD and GST Px levels (P<0.05-0.01) and in lowering blood NO content (P<0.01). Analysis on the correlation between the restoration of neural function and the changes of LPO, SOD and GST Px levels suggested that the effect of acupuncture in improving neural function may be related to changes of the aforementioned indexes. Conclusion: Acupuncture therapy can significantly lower blood LPO and NO levels and evidently raise blood SOD and GST Px levels in stroke patients.展开更多
BACKGROUND It is known that under conditions of tissue tolerance to insulin,observed during type 2 diabetes mellitus(DM2),there is an increased production of reactive oxygen species.Moreover,the free radicals can init...BACKGROUND It is known that under conditions of tissue tolerance to insulin,observed during type 2 diabetes mellitus(DM2),there is an increased production of reactive oxygen species.Moreover,the free radicals can initiate lipid peroxidation(LPO)in lipoprotein particles.The concentration of LPO products can influence the state of insulin receptors,repressing their hormone connection activity,which is expressed as a reduction of the glucose consumption by cells.It is possible that reduction in glucose concentration during administration of 10-(6-plastoquinonyl)decyltriphenylphosphonium(SkQ1)to rats with DM2 may be related to the antioxidant properties of this substance.AIM To establish the influence of SkQ1 on free-radical homeostasis in the heart and blood serum of rats with streptozotocin-induced hyperglycemia.METHODS To induce hyperglycemia,rats were fed a high-fat diet for 1 mo and then administered two intra-abdominal injections of streptozotocin with a 7-d interval at a 30 mg/kg of animal weight dose with citrate buffer equal to pH 4.4.SkQ1 solution was administered intraperitoneally at a 1250 nmol/kg dose per day.Tissue samples were taken from control animals,animals with experimental hyperglycemia,rats with streptozotocin-induced glycemia that were administered SkQ1 solution,animals housed under standard vivarium conditions that were administered SkQ1,rats that were administered intraperitoneally citrate buffer equal to pH 4.4 once a week during 2 wk after 1-mo high-fat diet,and animals that were administered intraperitoneally with appropriate amount of solution without SkQ1(98%ethanol diluted eight times with normal saline solution).To determine the intensity of free radical oxidation and total antioxidant activity,we used the biochemiluminescence method.Aconitate hydratase(AH),superoxide dismutase,and catalase activities were estimated using the Hitachi U-1900 spectrophotometer supplied with software.The amount of citrate was determined by means of the Natelson method.Real-time polymerase chain reaction was carried out using an amplifier ANK-32.RESULTS It was found that the mitochondrial-directed antioxidant elicits decrease of biochemiluminescence parameter values that increase by pathology as well as the levels of primary products of LPO,such as diene conjugates and carbonyl compounds,which indicate intensity of free radical oxidation.At the same time,the activity of AH,considered a crucial target of free radicals,which decreased during experimental hyperglycemia,increased.Apparently,increasing activity of AH influenced the speed of citrate utilization,whose concentration decreased after administering SkQ1 by pathology.Moreover,the previously applied antioxidant during hyperglycemia influenced the rate of antioxidant system mobilization.Thus,superoxide dismutase and catalase activity,as well as the level of gene transcript under influence of SkQ1 at pathology,were changing to the direction of control groups values.CONCLUSION According to the results of performed research,SkQ1 can be considered a promising addition to be included in antioxidant therapy of DM2.展开更多
Selective depression of pyrite remains a major bottleneck in copper flotation,particularly when high-pyrite ores are processed and saline water is used.In such environments,conventional approaches using lime and inert...Selective depression of pyrite remains a major bottleneck in copper flotation,particularly when high-pyrite ores are processed and saline water is used.In such environments,conventional approaches using lime and inert grinding media often fail to discriminate ef-fectively between pyrite and valuable copper minerals due to strong copper activation on pyrite surfaces.This study introduced a novel approach using inorganic radicals generated from peroxymonosulfate(PMS)to selectively oxidize and depress pyrite.Flotation tests with synthetic high-pyrite ore blends showed that PMS significantly reduced pyrite recovery while maintaining or improving chalcopyrite flot-ation.Ethylenediaminetetraacetic acid(EDTA)extraction confirmed selective oxidation of pyrite,and electron paramagnetic resonance(EPR)spectroscopy identified hydroxyl(·OH)and sulfate(SO_(4)^(·-))radicals as the dominant reactive species.Iron ions from grinding me-dia and mineral surfaces were identified as key activators of PMS.A major insight was pyrite’s dual role,acting both as a radical scav-enger and an activator,which made it highly reactive and susceptible to radical-induced oxidation.This process converted surface copper-sulfur species into copper hydroxides,effectively suppressing pyrite flotation.While previous studies have applied EPR to detect radicals in simplified activator/precursor systems,this study provides the first direct mechanistic evidence of radical-driven selectivity in flotation by detecting inorganic radicals in a complex flotation slurry,thereby demonstrating their persistence under industrially relevant conditions and establishing a foundation for more effective and targeted flotation strategies.展开更多
Phenol degradation in photochemically enhanced Fenton process was investigated in this work. UV-VIS spectra of phenol degradation showed the difference between photo-Fenton process and UV/H2O2, which is a typical hydr...Phenol degradation in photochemically enhanced Fenton process was investigated in this work. UV-VIS spectra of phenol degradation showed the difference between photo-Fenton process and UV/H2O2, which is a typical hydroxyl radical process. A possible pathway diagram for phenol degradation in photo-Fenton process was proposed, and a mathematical model for chemical oxygen demand (COD) removal was developed. Operating parameters such as dosage of H2O2 and ferrous ions, pH, suitable carrier gas were found to impact the removal of COD significantly. The results and analysis of kinetic parameters calculated from the kinetic model showed that complex degradation of phenol was the main pathway for removal of COD: while hydroxyl radicals acted weakly in the photo-Fenton degradation of phenol.展开更多
Fenton oxidation is generally inhibited in the presence of a high concentration of chloride ions.This study investigated the feasibility of using benzoquinone（BQ） and hydroxylamine hydrochloride（HA） as Fenton enha...Fenton oxidation is generally inhibited in the presence of a high concentration of chloride ions.This study investigated the feasibility of using benzoquinone（BQ） and hydroxylamine hydrochloride（HA） as Fenton enhancers for the removal of glycerin from saline water under ambient temperature by accelerating the ferric system.It was found that organics removal was not obviously affected by chloride ions of low concentration（less than 0.1 mol/L）,while the mineralization rate was strongly inhibited in the presence of a large amount of chloride ions.In addition,ferric hydrolysis-precipitation was significantly alleviated in the presence of HA and BQ,and HA was more effective in reducing ferric ions into ferrous ions than HA,while the H_2O_2 decomposition rate was higher in the BQ-Fenton system.Electron spin resonance analysis revealed that OH production was reduced in high salinity conditions,while it was enhanced after the addition of HA and BQ（especially HA）.This study provided a possible solution to control and alleviate the inhibitory effect of chloride ions on the Fenton process for organics removal.展开更多
Ozonation of oxalate in aqueous phase was performed with a commercial activated carbon（AC）in this work. The effect of AC dosage and solution pH on the contribution of hydroxyl radicals（HOU） in bulk solution and ox...Ozonation of oxalate in aqueous phase was performed with a commercial activated carbon（AC）in this work. The effect of AC dosage and solution pH on the contribution of hydroxyl radicals（HOU） in bulk solution and oxidation on the AC surface to the removal of oxalate was studied. We found that the removal of oxalate was reduced by tert-butyl alcohol（tBA） with low dosages of AC,while it was hardly affected by tBA when the AC dosage was greater than 0.3 g/L. tBA also inhibited ozone decomposition when the AC dosage was no more than 0.05 g/L, but it did not work when the AC dosage was no less than 0.1 g/L. These observations indicate that HOUin bulk solution and oxidation on the AC surface both contribute to the removal of oxalate. HOU oxidation in bulk solution is significant when the dosage of AC is low, whereas surface oxidation is dominant when the dosage of AC is high. The oxalate removal decreased with increasing pH of the solution with an AC dosage of 0.5 g/L. The degradation of oxalate occurs mainly through surface oxidation in acid and neutral solution, but through HOUoxidation in basic bulk solution. A mechanism involving both HOUoxidation in bulk solution and surface oxidation was proposed for AC enhanced ozonation of oxalate.展开更多
Degradation of bisphenol A（BPA） in aqueous solution using sulfate radicals was investigated using the Fe（II）-activated peroxydisulfate（PDS） process, electrochemical process, electrochemical process with 2.5 mmol...Degradation of bisphenol A（BPA） in aqueous solution using sulfate radicals was investigated using the Fe（II）-activated peroxydisulfate（PDS） process, electrochemical process, electrochemical process with 2.5 mmol/L Na2S2O8 without Fe（II）, and electrochemical assistant Fe（II）-activated PDS process. It was found that the electrochemical assistant Fe（II）-activated PDS process performed best in the degradation of BPA.The variables considered to influence the degradation efficiency of BPA were the initial concentration of Fe2 t, the initial concentration of Na2S2O8, and the current density. More than 97% of the BPA removals were achieved within 120 min under the optimum operational condition.The degradation of BPA was accompanied by the formation of phenol, hydroquinone, and small-molecule compounds such as succinic acid. The electron transfer was the principal step in the oxidation of BPA.展开更多
As one of the most toxic heavy metals, the oxidation of inorganic arsenic has drawn great attention among environmental scientists. However, little has been reported on the solar photochemical behavior of arsenic spec...As one of the most toxic heavy metals, the oxidation of inorganic arsenic has drawn great attention among environmental scientists. However, little has been reported on the solar photochemical behavior of arsenic species on top-soil. In the present work, the influencing factors（p H, relative humidity（RH）, humic acid（HA）, trisodium citrate, and additional iron ions） and the contributions of reactive oxygen species（ROS, mainly HO^- and HO2^-/O2^-） to photooxidation of As（Ⅲ） to As（Ⅴ） on kaolinite surfaces under UV irradiation（λ = 365 nm）were investigated. Results showed that lower p H facilitated photooxidation, and the photooxidation efficiency increased with the increase of RH and trisodium citrate.Promotion or inhibition of As（Ⅲ） photooxidation by HA was observed at low or high dosages, respectively. Additional iron ions greatly promoted the photooxidation, but excessive amounts of Fe^2＋competed with As（Ⅲ） for oxidation by ROS. Experiments on scavengers indicated that the HOUradical was the predominant oxidant in this system.Experiments on actual soil surfaces proved the occurrence of As（Ⅲ） photooxidation in real topsoil. This work demonstrates that the photooxidation process of As（Ⅲ） on the soil surface should be taken into account when studying the fate of arsenic in natural soil newly polluted with acidic wastewater containing As（Ⅲ）.展开更多
Sprague-Dawley neonatal rats within 7 days after birth were used in this study. The left common carotid artery was occluded and rats were housed in an 8% O2 environment for 2 hours to establish a hypoxic-ischemic brai...Sprague-Dawley neonatal rats within 7 days after birth were used in this study. The left common carotid artery was occluded and rats were housed in an 8% O2 environment for 2 hours to establish a hypoxic-ischemic brain damage model. 17β-estradiol （1 × 10-5 M） was injected into the rat abdominal cavity after the model was successfully established. The left hemisphere was obtained at 12, 24, 48, 72 hours after operation. Results showed that malondialdehyde content in the left brain of neonatal rats gradually increased as modeling time prolonged, while malondialdehyde content of 17β-estrodial-treated rats significantly declined by 24 hours, reached lowest levels at 48 hours, and then peaked at 72 hours after injury. Nicotinamide-adenine dinucleotide phosphate histochemical staining showed the nitric oxide synthase-positive cells and fibers dyed blue/violet and were mainly distributed in the cortex, hippocampus and medial septal nuclei. The number of nitric oxide synthase-positive cells peaked at 48 hours and significantly decreased after 17β-estrodial treatment. Our experimental findings indicate that estrogen plays a protective role following hypoxic-ischemic brain damage by alleviating lipid peroxidation through reducing the expression of nitric oxide synthase and the content of malondialdehyde.展开更多
While the cause of dopaminergic neuronal cell death in Parkinson＇s disease（PD）is not yet understood,many endogenous molecules have been implicated in its pathogenesis.β-phenethylamine（β-PEA）,a component of vari...While the cause of dopaminergic neuronal cell death in Parkinson＇s disease（PD）is not yet understood,many endogenous molecules have been implicated in its pathogenesis.β-phenethylamine（β-PEA）,a component of various food items including chocolate and wine,is an endogenous molecule produced from phenylalanine in the brain.It has been reported recently that long-term administration ofβ-PEA in rodents causes neurochemical and behavioral alterations similar to that produced by parkinsonian neurotoxins.The toxicity ofβ-PEA has been linked to the production of hydroxyl radical（.OH）and the generation of oxidative stress in dopaminergic areas of the brain,and this may be mediated by inhibition of mitochondrial complex-I.Another significant observation is that administration ofβ-PEA to rodents reduces striatal dopamine content and induces movement disorders similar to those of parkinsonian rodents.However,no reports are available on the extent of dopaminergic neuronal cell death after administration ofβ-PEA.Based on the literature,we set out to establishβ-PEA as an endogenous molecule that potentially contributes to the progressive development of PD.The sequence of molecular events that could be responsible for dopaminergic neuronal cell death in PD by consumption ofβ-PEA-containing foods is proposed here.Thus,long-term over-consumption of food items containingβ-PEA could be a neurological risk factor having significant pathological consequences.展开更多
Objective:To examine the effects of hydroalcoholic extract and fractions of Hordeum vulgare Linn.(H.vulgare,Da Mai)on streptozotocin(STZ)-induced diabetic nephropathy in Sprague-Dawley rat models.Methods:The study inv...Objective:To examine the effects of hydroalcoholic extract and fractions of Hordeum vulgare Linn.(H.vulgare,Da Mai)on streptozotocin(STZ)-induced diabetic nephropathy in Sprague-Dawley rat models.Methods:The study involved preliminary phytochemical screening of extract and fractions,estimation of secondary metabolites,chromatographic studies using high performance liquid chromatography(HPLC),antioxidant potential using 1,1-diphenyl-2-picrylhydrazyl(DPPH),nitric oxide radical scavenging and reducing power methods along with the determination of potential against diabetic nephropathy in STZ-induced rat models.Results:The phytochemical evaluation of the hydroalcoholic extract of H.vulgare and fractions revealed the presence of various phytoconstituents such as alkaloids,saponins,tannins,flavonoids,and glycosides.The chromatographic analysis indicated the peak complementing marker compound epicatechin and significant antioxidant activity in the extract and aqueous fraction.STZ-induced rats showed abnormal levels of serum albumin,creatinine,total cholesterol,blood urea nitrogen(BUN),and triglycerides,and urine albumin and creatinine,which returned to normal after 8 weeks of treatment with hydroalcoholic extract(400 mg/kg)and aqueous fraction(50 mg/kg)of H.vulgare.Conclusion:Hydroalcoholic extract(400 mg/kg)and aqueous fraction(50 mg/kg)of H.vulgare have significant antioxidant potential and positive effects on diabetic nephropathy.The fractionation and optimization increase the concentration of polyphenols in aqueous extract,causing a decrease in the dose required for effects against diabetic nephropathy.展开更多
The fate of 2-nitrobenzaldehyde(2-NBA)is of interest in atmospheric chemistry as it is a semi-volatile organic compound with high photosensitivity.This study presents a quantum chemical study of the gas-phase reaction...The fate of 2-nitrobenzaldehyde(2-NBA)is of interest in atmospheric chemistry as it is a semi-volatile organic compound with high photosensitivity.This study presents a quantum chemical study of the gas-phase reactions of 2-NBA photo-excitation and OH-oxidation in the absence and presence of small TiO_(2) clusters.To further understand the unknown photolysis mechanism,the photo-reaction pathways of ground singlet state and the lying excited triplet state of 2-NBA were investigated including the initial and subsequent reactions of proton transfer,direct CO,NO_(2),and HCO elimination routes in the presence of O_(2) and NO.Meanwhile,the OH-mediated degradation of 2-NBA proceeded via five H-extraction and six OH-addition channels by indirect mechanism,which follows a succession of reaction steps initiated by the formation of weakly stable intermediate complexes.The H-extraction from the-CHO group was the dominant pathway with a negative activation energy of-1.22 kcal/mol.The calculated rate coefficients at 200–600 K were close to the experimental data in literature within 308-352 K,and the kinetic negative temperature independence was found in both experimental literature and computational results.Interestingly,2-NBA was favored to be captured onto small TiO_(2) clusters via six adsorption configurations formed via various combination of three types of bonds of Ti…O,Ti…C,and O…H between the molecularly adsorbed 2-NBA and TiO_(2) clusters.Comparison indicted that the chemisorptions of aldehyde oxygen have largest energies.The results suggested adsorption conformations have a respectable impact on the catalysis barrier.This study is significant for understanding the atmospheric chemistry of 2-nitrobenzaldehyde.展开更多
A novel strategy for site-selective benzylic C–H oxidation has been developed through mediated electrolysis.A bulky maleimide N-oxyl radical(MINO)generated by proton-coupled electrochemical oxidation of N-hydroxymale...A novel strategy for site-selective benzylic C–H oxidation has been developed through mediated electrolysis.A bulky maleimide N-oxyl radical(MINO)generated by proton-coupled electrochemical oxidation of N-hydroxymaleimide(NHMI),serves as a hydrogen atom-transfer mediator.Good-to-excellent site selectivity was observed among different substrates,providing a practical approach for site-selective benzylic C–H oxidation.Additionally,the hydrogen-atom transfer mechanism for C–H electrochemical oxidation allows the oxidation to proceed at much lower anode potentials relative to direct electrolysis and with minimal reliance on the substrate's electronic properties.展开更多
It remains unclear whether dicofol should be defined as a persistent organic pollutant. Its environmental persistence has gained attention. This study focused on its degradation by cellulase. Cellulase was separated u...It remains unclear whether dicofol should be defined as a persistent organic pollutant. Its environmental persistence has gained attention. This study focused on its degradation by cellulase. Cellulase was separated using a gel chromatogram, and its degradation activity towards dicofol involved its endoglucanase activity. By analyzing the kinetic parameters of cellulase reacting with mixed substrates, it was shown that cellulase reacted on dicofol and carboxyl methyl cellulose through two different active centers. Thus, the degradation of dicofol was shown to be an oxidative process by cellulase. Next, by comparing the impacts of tert-butyl alcohol（a typical OH free-radical inhibitor） on the removal efficiencies of dicofol under both cellulase and Fenton reagent systems, it was shown that the removal of dicofol was initiated by OH free radicals produced by cellulase. Finally, 4,4′-dichlorodibenzophenone and chloride were detected using gas chromatography mass spectrometry and ion chromatography analysis, which supported our hypothesis. The reaction mechanism was analyzed and involved an attack by OH free radicals at the orthocarbon of dicofol, resulting in the degradation product 4,4′-dichloro-dibenzophenone.展开更多
In this article, the NO3 radical-initiated atmospheric oxidation degradation of DDT was theoretically investigated using molecular orbital theory calculations. All the calculations of intermediates, transition states ...In this article, the NO3 radical-initiated atmospheric oxidation degradation of DDT was theoretically investigated using molecular orbital theory calculations. All the calculations of intermediates, transition states and products were performed at the MPWB1K/6-311＋G（3df,2p）//MPWB1K/6- 31＋G（d,p） level of theory. Several energetically favorable reaction pathways were revealed. The formation mechanisms of secondary pollutants were presented and discussed. The rate constants were deduced over the temperature range of 273-333 K using canonical variational transition-state （CVT） theory with the small curvature tunneling （SCT） method. Our study shows that H abstraction from the alkyl group and NO3 addition to the Ca atom of the benzene ring are the dominant reaction pathways. The rate-temperature formula of the overall rate constants is k（T）（DDT＋NO3） = （7.21 ~ 10-15）exp（-153.81/T） cm3/（mol.sec） over the possible atmospheric temperature range of 273-333 K. The atmospheric lifetime of DDT determined by NO3 radical is about 52.5 days, which indicates that it can be degraded in the gas phase within several months.展开更多
Conventional heme enzymes utilize iron-oxygen intermediates to activate substrates and drive reactions.Re-cently,Chen et al.discovered a novel NADPH-independent superoxide mechanism of heme catalase EasC,which facilit...Conventional heme enzymes utilize iron-oxygen intermediates to activate substrates and drive reactions.Re-cently,Chen et al.discovered a novel NADPH-independent superoxide mechanism of heme catalase EasC,which facilitates an O_(2)-dependent radical oxidative cyclization reaction during ergot alkaloid biosynthesis.This en-zyme coordinates superoxide-mediated catalysis by connecting spatially distinct NADPH-binding pocket and heme pocket via a slender tunnel,offering a novel perspective on the catalytic mechanisms of heme enzymes in nature.展开更多
The age-dependent peculiarities of stimulation of free radical processes in subcellular fractions of skeletal muscle of rats subjected to long-term immobilization stress were studied in order to improve knowledge abou...The age-dependent peculiarities of stimulation of free radical processes in subcellular fractions of skeletal muscle of rats subjected to long-term immobilization stress were studied in order to improve knowledge about changes of muscular tissue during ontogenesis. It is found that adult animals do not show accumulation of proteins carbonyls, TBA-reactive substances, and Schiff bases in subcellular fractions of the thigh muscle when immobUized. Long-term immobilization causes apparent manifestation of oxidative stress only in mitochondrial fraction in pubertal rats. Mitochondrial oxidative stress defense systems are sufficiently effective, however, direction of pathways of free radical oxidation carbonyl products catabolism alters in the cytoplasm of myocytes in old rats under long-term immobilization conditions.展开更多
BACKGROUND： Oxidative stress is an extremely widespread condition manifested in an increased rate of free-radical processes and accumulation of reactive oxygen species （ROS） in the tissues. It appears in different ...BACKGROUND： Oxidative stress is an extremely widespread condition manifested in an increased rate of free-radical processes and accumulation of reactive oxygen species （ROS） in the tissues. It appears in different physiologic states and pathological processes accompanied by stimulation of the sympathetic adrenal system or tissue hypoxia or under stress. However, until now, there is still no clarity on the issue of the significance of oxidative stress in the development of adaptation processes in the organism. OBJECTIVE： In the present work we will review the most recent finding about physiologic role of oxidative stress and its participation in adaptation of an organism to effect of different adverse factors. METHODS： A systematic literature search was performed using the Pubmed search engine. Studies published over past 18 years, i.e. between 1998 and 2015 were considered for review. Followed keywords were used： ＂oxidative stress,＂ ＂free radical oxidation,＂ ＂ROS,＂ ＂endogenous aldehydes,＂ ＂adaptation.＂ RESULTS： The article cites arguments supporting the notion that oxidative stress serves as a nonspecific link in the adaptation of the human body to the effects of injurious factors. Oxidative stress exerts regulatory effects by changing the redox state of the cell. Oxidative stress affects on various intracellular proteins containing cysteine residues, e.g., enzymes, chaperones, and transcription factors, etc. For this reason, the use of antioxidants for the treatment and prophylaxis of a wide range of diseases is not recommended. CONCLUSION： Further investigation is needed in this field. The most attention should be paid to careful experimental verification aimed at quantitative assessment of the ROS level in tissues under oxidative stress, as well as at the study of possibility of enhancing the catabolism of free radical oxidation carbonyl products in order to prevent tissue damage under oxidative stress.展开更多
基金supported by the National Natural Science Foundation of China(52270043)the National Key Research and Development Program of China(2023YFE0113800 and 2024YFC3715000)the Natural Science Foundation of Beijing Municipality(8242030).
文摘The contamination of wastewater with organic pollutants and nitrogen compounds poses significant environmental challenges.The primary objective of wastewater treatment is the simultaneous denitrification and decarbonization of ammonia nitrogen and organics into harmless by-products.This study presents a novel method for the directional generation of chlorine radical species like·ClO and·Cl using electro-reactive membranes(EMs)known as RuO_(2)@PbO_(2)-M,which were fabricated using an electro-deposition coupled template approach.This method facilitates the rapid and efficient conversion of ammonia to nitrogen and concurrently reduces the chemical oxygen demand in the effluent.Our system achieved ultra-efficient simultaneous denitrification and decarbonization with minimal energy consumption in single-filtration mode,thereby eliminating the need for chemical precursors.We elucidate the formation pathway of·ClO and·Cl during the electrochemical oxidation process involving RuO_(2)@PbO_(2)-M,where·Cl generated from RuO_(2)reacts with·OH from PbO_(2)under hypochlorous acid conditions,thereby enhancing nitrogen and carbon removal.These findings highlight a novel electro-filtration and an innovative reactive membrane design for·ClO synthesis,which provides a new research framework for the concurrent removal of nitrogen and carbon,and offers a promising solution to enhance wastewater treatment efficiency.
基金financially supported by the National Key R&D Program of China(No.2023YFE0112100)the XMU Training Program of Innovation and Entrepreneurship of Undergraduates(No.2024Y1328)。
文摘The generation of reactive intermediates is a pivotal step during photocatalytic redox elimination of organic micropollutants in water.The UV/S(Ⅳ)-based water treatment system has garnered significant attention as an efficient advanced reduction process for pollutant abatement.However,as a reductive system,the conventional UV/S(Ⅳ)approach exhibits limited efficacy in removing electron-rich micropollutants.Our study uncovered that meso–tetrakis(4-chlorophenyl)porphyrin-Fe(Ⅲ)chloride(TPPFe,a typical iron(Ⅲ)porphyrin)catalyzed the conversion of SO_(3)^(2-)into SO_(3)^(·-)under UV365irradiation without generating of eaq-and H·,leading to the formation of diverse oxidizing species.Additionally,the introduction of TPPFe induced an absorption redshift,broadening the range of applicable UV wavelengths.An in-depth photocatalytic cycle mechanism for TPPFe^(Ⅲ)Cl-[TPPFe^(Ⅱ)Cl]-was introduced and verified by density functional theory(DFT)calculations.Furthermore,quantum chemistry calculations via transition state were conducted to assess the oxidizing reactivity of the reactive species with micropollutants.Both·OH and SO_(4)^(·-)demonstrate a strong propensity to react with carbamazepine(CMZ,a model micropollutant).Meanwhile,1O2exhibits a distinct reaction mechanism with CMZ.Consequently,the radical-and ^(1)O_(2)-mediated distinct degradation pathways were elucidated.This study provides an experimental/theoretical exploration of reactive intermediate generation and their interactions with CMZ,shedding valuable insights into the mechanisms of electron-shuttling photosensitizers catalyzing the UV/S(Ⅳ)oxidation process.
文摘Objective: To observe the effect of acupuncture on blood oxygen free radical (OFR) and nitric oxide (NO) levels in the treatment of apoplectic sequelae. Methods: A total of 61 cases of apoplectic patients were subjected into this study and randomly divided into "JIN San Zhen" group (n=30) and control group (n=31). Blood lipid peroxidase (LPO), superoxide dismutase (SOD), glutathione peroxidase(GSH Px) and nitric oxide (NO) contents before and after acupuncture treatment were determined with radioimmunoassay. In both groups, acupuncture was given once daily, six times a week, with 4 weeks being a therapeutic course and with the interval between two weeks being a week, 3 courses all together. In "JIN San Zhen" group, acupoints of "JIN San Zhen" were used predominately, while in control group, scalp point Motor Sensory Area (MS 8) was used as the main point. Results: Self comparison showed that after 3 courses of treatment, in both groups, LPO and NO levels decreased significantly (P<0.05-0.01), SOD and GST Px values increased considerably (P<0.05-0.01). Comparison between two groups indicated that the effects of "JIN San Zhen" group are significantly superior to those of control group in raising blood SOD and GST Px levels (P<0.05-0.01) and in lowering blood NO content (P<0.01). Analysis on the correlation between the restoration of neural function and the changes of LPO, SOD and GST Px levels suggested that the effect of acupuncture in improving neural function may be related to changes of the aforementioned indexes. Conclusion: Acupuncture therapy can significantly lower blood LPO and NO levels and evidently raise blood SOD and GST Px levels in stroke patients.
文摘BACKGROUND It is known that under conditions of tissue tolerance to insulin,observed during type 2 diabetes mellitus(DM2),there is an increased production of reactive oxygen species.Moreover,the free radicals can initiate lipid peroxidation(LPO)in lipoprotein particles.The concentration of LPO products can influence the state of insulin receptors,repressing their hormone connection activity,which is expressed as a reduction of the glucose consumption by cells.It is possible that reduction in glucose concentration during administration of 10-(6-plastoquinonyl)decyltriphenylphosphonium(SkQ1)to rats with DM2 may be related to the antioxidant properties of this substance.AIM To establish the influence of SkQ1 on free-radical homeostasis in the heart and blood serum of rats with streptozotocin-induced hyperglycemia.METHODS To induce hyperglycemia,rats were fed a high-fat diet for 1 mo and then administered two intra-abdominal injections of streptozotocin with a 7-d interval at a 30 mg/kg of animal weight dose with citrate buffer equal to pH 4.4.SkQ1 solution was administered intraperitoneally at a 1250 nmol/kg dose per day.Tissue samples were taken from control animals,animals with experimental hyperglycemia,rats with streptozotocin-induced glycemia that were administered SkQ1 solution,animals housed under standard vivarium conditions that were administered SkQ1,rats that were administered intraperitoneally citrate buffer equal to pH 4.4 once a week during 2 wk after 1-mo high-fat diet,and animals that were administered intraperitoneally with appropriate amount of solution without SkQ1(98%ethanol diluted eight times with normal saline solution).To determine the intensity of free radical oxidation and total antioxidant activity,we used the biochemiluminescence method.Aconitate hydratase(AH),superoxide dismutase,and catalase activities were estimated using the Hitachi U-1900 spectrophotometer supplied with software.The amount of citrate was determined by means of the Natelson method.Real-time polymerase chain reaction was carried out using an amplifier ANK-32.RESULTS It was found that the mitochondrial-directed antioxidant elicits decrease of biochemiluminescence parameter values that increase by pathology as well as the levels of primary products of LPO,such as diene conjugates and carbonyl compounds,which indicate intensity of free radical oxidation.At the same time,the activity of AH,considered a crucial target of free radicals,which decreased during experimental hyperglycemia,increased.Apparently,increasing activity of AH influenced the speed of citrate utilization,whose concentration decreased after administering SkQ1 by pathology.Moreover,the previously applied antioxidant during hyperglycemia influenced the rate of antioxidant system mobilization.Thus,superoxide dismutase and catalase activity,as well as the level of gene transcript under influence of SkQ1 at pathology,were changing to the direction of control groups values.CONCLUSION According to the results of performed research,SkQ1 can be considered a promising addition to be included in antioxidant therapy of DM2.
基金support from the Australian Research Council(ARC)Linkage Project(No.LP230100166).
文摘Selective depression of pyrite remains a major bottleneck in copper flotation,particularly when high-pyrite ores are processed and saline water is used.In such environments,conventional approaches using lime and inert grinding media often fail to discriminate ef-fectively between pyrite and valuable copper minerals due to strong copper activation on pyrite surfaces.This study introduced a novel approach using inorganic radicals generated from peroxymonosulfate(PMS)to selectively oxidize and depress pyrite.Flotation tests with synthetic high-pyrite ore blends showed that PMS significantly reduced pyrite recovery while maintaining or improving chalcopyrite flot-ation.Ethylenediaminetetraacetic acid(EDTA)extraction confirmed selective oxidation of pyrite,and electron paramagnetic resonance(EPR)spectroscopy identified hydroxyl(·OH)and sulfate(SO_(4)^(·-))radicals as the dominant reactive species.Iron ions from grinding me-dia and mineral surfaces were identified as key activators of PMS.A major insight was pyrite’s dual role,acting both as a radical scav-enger and an activator,which made it highly reactive and susceptible to radical-induced oxidation.This process converted surface copper-sulfur species into copper hydroxides,effectively suppressing pyrite flotation.While previous studies have applied EPR to detect radicals in simplified activator/precursor systems,this study provides the first direct mechanistic evidence of radical-driven selectivity in flotation by detecting inorganic radicals in a complex flotation slurry,thereby demonstrating their persistence under industrially relevant conditions and establishing a foundation for more effective and targeted flotation strategies.
文摘Phenol degradation in photochemically enhanced Fenton process was investigated in this work. UV-VIS spectra of phenol degradation showed the difference between photo-Fenton process and UV/H2O2, which is a typical hydroxyl radical process. A possible pathway diagram for phenol degradation in photo-Fenton process was proposed, and a mathematical model for chemical oxygen demand (COD) removal was developed. Operating parameters such as dosage of H2O2 and ferrous ions, pH, suitable carrier gas were found to impact the removal of COD significantly. The results and analysis of kinetic parameters calculated from the kinetic model showed that complex degradation of phenol was the main pathway for removal of COD: while hydroxyl radicals acted weakly in the photo-Fenton degradation of phenol.
基金supported by the National Natural Science Foundation of China(Nos.51025830,41201498 and 51178360)
文摘Fenton oxidation is generally inhibited in the presence of a high concentration of chloride ions.This study investigated the feasibility of using benzoquinone（BQ） and hydroxylamine hydrochloride（HA） as Fenton enhancers for the removal of glycerin from saline water under ambient temperature by accelerating the ferric system.It was found that organics removal was not obviously affected by chloride ions of low concentration（less than 0.1 mol/L）,while the mineralization rate was strongly inhibited in the presence of a large amount of chloride ions.In addition,ferric hydrolysis-precipitation was significantly alleviated in the presence of HA and BQ,and HA was more effective in reducing ferric ions into ferrous ions than HA,while the H_2O_2 decomposition rate was higher in the BQ-Fenton system.Electron spin resonance analysis revealed that OH production was reduced in high salinity conditions,while it was enhanced after the addition of HA and BQ（especially HA）.This study provided a possible solution to control and alleviate the inhibitory effect of chloride ions on the Fenton process for organics removal.
基金supported by the National Natural Science Foundation of China (No. 21177130)the National Key Technology R&D Program (No. 2011BAC06B09)the Chinese Academy of Sciences Visiting Professorships for Senior International Scientists (No. 2009G2-28)
文摘Ozonation of oxalate in aqueous phase was performed with a commercial activated carbon（AC）in this work. The effect of AC dosage and solution pH on the contribution of hydroxyl radicals（HOU） in bulk solution and oxidation on the AC surface to the removal of oxalate was studied. We found that the removal of oxalate was reduced by tert-butyl alcohol（tBA） with low dosages of AC,while it was hardly affected by tBA when the AC dosage was greater than 0.3 g/L. tBA also inhibited ozone decomposition when the AC dosage was no more than 0.05 g/L, but it did not work when the AC dosage was no less than 0.1 g/L. These observations indicate that HOUin bulk solution and oxidation on the AC surface both contribute to the removal of oxalate. HOU oxidation in bulk solution is significant when the dosage of AC is low, whereas surface oxidation is dominant when the dosage of AC is high. The oxalate removal decreased with increasing pH of the solution with an AC dosage of 0.5 g/L. The degradation of oxalate occurs mainly through surface oxidation in acid and neutral solution, but through HOUoxidation in basic bulk solution. A mechanism involving both HOUoxidation in bulk solution and surface oxidation was proposed for AC enhanced ozonation of oxalate.
基金supported by the Natural Science Foundation of Jilin Province(Grant No.20140101215JC)the Key Program in Science and Technologies of Jilin Province(Grant No.20150204049SF)the Key Laboratory of Industrial Ecology and Environmental Engineering,the Ministry of Education of China(Grant No.KLIEEE-13-07)
文摘Degradation of bisphenol A（BPA） in aqueous solution using sulfate radicals was investigated using the Fe（II）-activated peroxydisulfate（PDS） process, electrochemical process, electrochemical process with 2.5 mmol/L Na2S2O8 without Fe（II）, and electrochemical assistant Fe（II）-activated PDS process. It was found that the electrochemical assistant Fe（II）-activated PDS process performed best in the degradation of BPA.The variables considered to influence the degradation efficiency of BPA were the initial concentration of Fe2 t, the initial concentration of Na2S2O8, and the current density. More than 97% of the BPA removals were achieved within 120 min under the optimum operational condition.The degradation of BPA was accompanied by the formation of phenol, hydroquinone, and small-molecule compounds such as succinic acid. The electron transfer was the principal step in the oxidation of BPA.
基金supported by the National Natural Science Foundation of China(Nos.21077080,21477090)
文摘As one of the most toxic heavy metals, the oxidation of inorganic arsenic has drawn great attention among environmental scientists. However, little has been reported on the solar photochemical behavior of arsenic species on top-soil. In the present work, the influencing factors（p H, relative humidity（RH）, humic acid（HA）, trisodium citrate, and additional iron ions） and the contributions of reactive oxygen species（ROS, mainly HO^- and HO2^-/O2^-） to photooxidation of As（Ⅲ） to As（Ⅴ） on kaolinite surfaces under UV irradiation（λ = 365 nm）were investigated. Results showed that lower p H facilitated photooxidation, and the photooxidation efficiency increased with the increase of RH and trisodium citrate.Promotion or inhibition of As（Ⅲ） photooxidation by HA was observed at low or high dosages, respectively. Additional iron ions greatly promoted the photooxidation, but excessive amounts of Fe^2＋competed with As（Ⅲ） for oxidation by ROS. Experiments on scavengers indicated that the HOUradical was the predominant oxidant in this system.Experiments on actual soil surfaces proved the occurrence of As（Ⅲ） photooxidation in real topsoil. This work demonstrates that the photooxidation process of As（Ⅲ） on the soil surface should be taken into account when studying the fate of arsenic in natural soil newly polluted with acidic wastewater containing As（Ⅲ）.
基金supported by the Project of Nantong Application Plan,No.BK2011055the Project of Nantong University,No.09Z032
文摘Sprague-Dawley neonatal rats within 7 days after birth were used in this study. The left common carotid artery was occluded and rats were housed in an 8% O2 environment for 2 hours to establish a hypoxic-ischemic brain damage model. 17β-estradiol （1 × 10-5 M） was injected into the rat abdominal cavity after the model was successfully established. The left hemisphere was obtained at 12, 24, 48, 72 hours after operation. Results showed that malondialdehyde content in the left brain of neonatal rats gradually increased as modeling time prolonged, while malondialdehyde content of 17β-estrodial-treated rats significantly declined by 24 hours, reached lowest levels at 48 hours, and then peaked at 72 hours after injury. Nicotinamide-adenine dinucleotide phosphate histochemical staining showed the nitric oxide synthase-positive cells and fibers dyed blue/violet and were mainly distributed in the cortex, hippocampus and medial septal nuclei. The number of nitric oxide synthase-positive cells peaked at 48 hours and significantly decreased after 17β-estrodial treatment. Our experimental findings indicate that estrogen plays a protective role following hypoxic-ischemic brain damage by alleviating lipid peroxidation through reducing the expression of nitric oxide synthase and the content of malondialdehyde.
文摘While the cause of dopaminergic neuronal cell death in Parkinson＇s disease（PD）is not yet understood,many endogenous molecules have been implicated in its pathogenesis.β-phenethylamine（β-PEA）,a component of various food items including chocolate and wine,is an endogenous molecule produced from phenylalanine in the brain.It has been reported recently that long-term administration ofβ-PEA in rodents causes neurochemical and behavioral alterations similar to that produced by parkinsonian neurotoxins.The toxicity ofβ-PEA has been linked to the production of hydroxyl radical（.OH）and the generation of oxidative stress in dopaminergic areas of the brain,and this may be mediated by inhibition of mitochondrial complex-I.Another significant observation is that administration ofβ-PEA to rodents reduces striatal dopamine content and induces movement disorders similar to those of parkinsonian rodents.However,no reports are available on the extent of dopaminergic neuronal cell death after administration ofβ-PEA.Based on the literature,we set out to establishβ-PEA as an endogenous molecule that potentially contributes to the progressive development of PD.The sequence of molecular events that could be responsible for dopaminergic neuronal cell death in PD by consumption ofβ-PEA-containing foods is proposed here.Thus,long-term over-consumption of food items containingβ-PEA could be a neurological risk factor having significant pathological consequences.
基金supported by Rashtrsant Tukadoji Maharaj Memorial Fellowship from Rashtrasant Tukadoji Maharaj Nagpur University。
文摘Objective:To examine the effects of hydroalcoholic extract and fractions of Hordeum vulgare Linn.(H.vulgare,Da Mai)on streptozotocin(STZ)-induced diabetic nephropathy in Sprague-Dawley rat models.Methods:The study involved preliminary phytochemical screening of extract and fractions,estimation of secondary metabolites,chromatographic studies using high performance liquid chromatography(HPLC),antioxidant potential using 1,1-diphenyl-2-picrylhydrazyl(DPPH),nitric oxide radical scavenging and reducing power methods along with the determination of potential against diabetic nephropathy in STZ-induced rat models.Results:The phytochemical evaluation of the hydroalcoholic extract of H.vulgare and fractions revealed the presence of various phytoconstituents such as alkaloids,saponins,tannins,flavonoids,and glycosides.The chromatographic analysis indicated the peak complementing marker compound epicatechin and significant antioxidant activity in the extract and aqueous fraction.STZ-induced rats showed abnormal levels of serum albumin,creatinine,total cholesterol,blood urea nitrogen(BUN),and triglycerides,and urine albumin and creatinine,which returned to normal after 8 weeks of treatment with hydroalcoholic extract(400 mg/kg)and aqueous fraction(50 mg/kg)of H.vulgare.Conclusion:Hydroalcoholic extract(400 mg/kg)and aqueous fraction(50 mg/kg)of H.vulgare have significant antioxidant potential and positive effects on diabetic nephropathy.The fractionation and optimization increase the concentration of polyphenols in aqueous extract,causing a decrease in the dose required for effects against diabetic nephropathy.
基金supported by the National Natural Science Foundation of China(No.22006101)the Natural Science Foundation of Liaoning Province(No.2023-MS-250)+3 种基金the Basic Scientific Research Foundation Project of Liaoning Province(No.LJKQZ20222283)the National Natural Science Foundation of China-Liaoning Joint Fund(No.U1908204)the Doctoral Research Start-up Fund of Shenyang Normal University(No.BS202124,No.BS202016)the Basic Scientific Research Project of Universities in Liaoning Province(No.LQN202007)。
文摘The fate of 2-nitrobenzaldehyde(2-NBA)is of interest in atmospheric chemistry as it is a semi-volatile organic compound with high photosensitivity.This study presents a quantum chemical study of the gas-phase reactions of 2-NBA photo-excitation and OH-oxidation in the absence and presence of small TiO_(2) clusters.To further understand the unknown photolysis mechanism,the photo-reaction pathways of ground singlet state and the lying excited triplet state of 2-NBA were investigated including the initial and subsequent reactions of proton transfer,direct CO,NO_(2),and HCO elimination routes in the presence of O_(2) and NO.Meanwhile,the OH-mediated degradation of 2-NBA proceeded via five H-extraction and six OH-addition channels by indirect mechanism,which follows a succession of reaction steps initiated by the formation of weakly stable intermediate complexes.The H-extraction from the-CHO group was the dominant pathway with a negative activation energy of-1.22 kcal/mol.The calculated rate coefficients at 200–600 K were close to the experimental data in literature within 308-352 K,and the kinetic negative temperature independence was found in both experimental literature and computational results.Interestingly,2-NBA was favored to be captured onto small TiO_(2) clusters via six adsorption configurations formed via various combination of three types of bonds of Ti…O,Ti…C,and O…H between the molecularly adsorbed 2-NBA and TiO_(2) clusters.Comparison indicted that the chemisorptions of aldehyde oxygen have largest energies.The results suggested adsorption conformations have a respectable impact on the catalysis barrier.This study is significant for understanding the atmospheric chemistry of 2-nitrobenzaldehyde.
文摘A novel strategy for site-selective benzylic C–H oxidation has been developed through mediated electrolysis.A bulky maleimide N-oxyl radical(MINO)generated by proton-coupled electrochemical oxidation of N-hydroxymaleimide(NHMI),serves as a hydrogen atom-transfer mediator.Good-to-excellent site selectivity was observed among different substrates,providing a practical approach for site-selective benzylic C–H oxidation.Additionally,the hydrogen-atom transfer mechanism for C–H electrochemical oxidation allows the oxidation to proceed at much lower anode potentials relative to direct electrolysis and with minimal reliance on the substrate's electronic properties.
基金supported by the special fund provided by the State Key Joint Laboratory of Environmental Simulation and Pollution Control(Peking University,No.09Z02ESPCP)the Special Research Funding for Public Benefit Industries from National Ministry of Environmental Protection(No.201209020)
文摘It remains unclear whether dicofol should be defined as a persistent organic pollutant. Its environmental persistence has gained attention. This study focused on its degradation by cellulase. Cellulase was separated using a gel chromatogram, and its degradation activity towards dicofol involved its endoglucanase activity. By analyzing the kinetic parameters of cellulase reacting with mixed substrates, it was shown that cellulase reacted on dicofol and carboxyl methyl cellulose through two different active centers. Thus, the degradation of dicofol was shown to be an oxidative process by cellulase. Next, by comparing the impacts of tert-butyl alcohol（a typical OH free-radical inhibitor） on the removal efficiencies of dicofol under both cellulase and Fenton reagent systems, it was shown that the removal of dicofol was initiated by OH free radicals produced by cellulase. Finally, 4,4′-dichlorodibenzophenone and chloride were detected using gas chromatography mass spectrometry and ion chromatography analysis, which supported our hypothesis. The reaction mechanism was analyzed and involved an attack by OH free radicals at the orthocarbon of dicofol, resulting in the degradation product 4,4′-dichloro-dibenzophenone.
基金supported by the National Natural Science Foundation of China(No.21337001,21377073)the Independent Innovation Foundation of Shandong University(IIFSDU)(No.2012JC030)
文摘In this article, the NO3 radical-initiated atmospheric oxidation degradation of DDT was theoretically investigated using molecular orbital theory calculations. All the calculations of intermediates, transition states and products were performed at the MPWB1K/6-311＋G（3df,2p）//MPWB1K/6- 31＋G（d,p） level of theory. Several energetically favorable reaction pathways were revealed. The formation mechanisms of secondary pollutants were presented and discussed. The rate constants were deduced over the temperature range of 273-333 K using canonical variational transition-state （CVT） theory with the small curvature tunneling （SCT） method. Our study shows that H abstraction from the alkyl group and NO3 addition to the Ca atom of the benzene ring are the dominant reaction pathways. The rate-temperature formula of the overall rate constants is k（T）（DDT＋NO3） = （7.21 ~ 10-15）exp（-153.81/T） cm3/（mol.sec） over the possible atmospheric temperature range of 273-333 K. The atmospheric lifetime of DDT determined by NO3 radical is about 52.5 days, which indicates that it can be degraded in the gas phase within several months.
基金supported by the National Natural Science Foundation of China(32025001,32300021,32200017).
文摘Conventional heme enzymes utilize iron-oxygen intermediates to activate substrates and drive reactions.Re-cently,Chen et al.discovered a novel NADPH-independent superoxide mechanism of heme catalase EasC,which facilitates an O_(2)-dependent radical oxidative cyclization reaction during ergot alkaloid biosynthesis.This en-zyme coordinates superoxide-mediated catalysis by connecting spatially distinct NADPH-binding pocket and heme pocket via a slender tunnel,offering a novel perspective on the catalytic mechanisms of heme enzymes in nature.
文摘The age-dependent peculiarities of stimulation of free radical processes in subcellular fractions of skeletal muscle of rats subjected to long-term immobilization stress were studied in order to improve knowledge about changes of muscular tissue during ontogenesis. It is found that adult animals do not show accumulation of proteins carbonyls, TBA-reactive substances, and Schiff bases in subcellular fractions of the thigh muscle when immobUized. Long-term immobilization causes apparent manifestation of oxidative stress only in mitochondrial fraction in pubertal rats. Mitochondrial oxidative stress defense systems are sufficiently effective, however, direction of pathways of free radical oxidation carbonyl products catabolism alters in the cytoplasm of myocytes in old rats under long-term immobilization conditions.
文摘BACKGROUND： Oxidative stress is an extremely widespread condition manifested in an increased rate of free-radical processes and accumulation of reactive oxygen species （ROS） in the tissues. It appears in different physiologic states and pathological processes accompanied by stimulation of the sympathetic adrenal system or tissue hypoxia or under stress. However, until now, there is still no clarity on the issue of the significance of oxidative stress in the development of adaptation processes in the organism. OBJECTIVE： In the present work we will review the most recent finding about physiologic role of oxidative stress and its participation in adaptation of an organism to effect of different adverse factors. METHODS： A systematic literature search was performed using the Pubmed search engine. Studies published over past 18 years, i.e. between 1998 and 2015 were considered for review. Followed keywords were used： ＂oxidative stress,＂ ＂free radical oxidation,＂ ＂ROS,＂ ＂endogenous aldehydes,＂ ＂adaptation.＂ RESULTS： The article cites arguments supporting the notion that oxidative stress serves as a nonspecific link in the adaptation of the human body to the effects of injurious factors. Oxidative stress exerts regulatory effects by changing the redox state of the cell. Oxidative stress affects on various intracellular proteins containing cysteine residues, e.g., enzymes, chaperones, and transcription factors, etc. For this reason, the use of antioxidants for the treatment and prophylaxis of a wide range of diseases is not recommended. CONCLUSION： Further investigation is needed in this field. The most attention should be paid to careful experimental verification aimed at quantitative assessment of the ROS level in tissues under oxidative stress, as well as at the study of possibility of enhancing the catabolism of free radical oxidation carbonyl products in order to prevent tissue damage under oxidative stress.
