CuCl-catalyzed oxidative N-demethylation of arylamines proceeded in the presence of tert-butyl hydroperoxide. The one-electron transfer route of oxidative N-demethylation competed favorably with the H-atom abstraction...CuCl-catalyzed oxidative N-demethylation of arylamines proceeded in the presence of tert-butyl hydroperoxide. The one-electron transfer route of oxidative N-demethylation competed favorably with the H-atom abstraction route.展开更多
AIM: To investigate catalase(Kat A) and alkyl hydroperoxide reductase(Ahp C) antibodies of Helicobacter pylori as biomarkers for gastric cancer(GC).METHODS: This study included 232 cases and 264 controls. Recombinant ...AIM: To investigate catalase(Kat A) and alkyl hydroperoxide reductase(Ahp C) antibodies of Helicobacter pylori as biomarkers for gastric cancer(GC).METHODS: This study included 232 cases and 264 controls. Recombinant Kat A and Ahp C proteins were constructed and the levels of antibodies were tested by indirect enzyme-linked immunosorbent assay(ELISA). Logistic regression was applied to analyze the relationships between Kat A, Ahp C and GC. The χ2 trend test was used to evaluate the dose-response relationships between serum Kat A and Ahp C antibody levels and GC. Receiver operating characteristic(ROC) curve was used to evaluate the screening accuracy of Kat A and Ahp C as biomarkers. Combined analysis was used to observe screening accuracy of predictors for GC.RESULTS: In all subjects, the association between Kat A and Ahp C and GC risk was significant(P < 0.001) with odds ratio(OR) = 12.84(95%CI: 7.79-21.15)and OR = 2.4(95%CI: 1.55-3.73), respectively. Kat A and Ahp C antibody levels were strongly related to GC risk with a dose-dependent effect(P for trend < 0.001). The area under the ROC(AUC) for Kat A was 0.806, providing a sensitivity of 66.81% and specificity of 86.36%; and the AUC for Ahp C was 0.615, with a sensitivity of 75.65% and specificity of 45.49%. The AUC was 0.906 for Kat A and flagella protein A(Fla A) combined analysis.CONCLUSION: Serum Kat A and Ahp C antibodies are associated with GC risk and Kat A may serve as a biomarker for GC. Kat A/Fla A combined analysis improved screening accuracy.展开更多
The potential of carrying out oxidative desulfurization(ODS) using oxygen as an oxidant was explored in this work. n-Octane firstly reacted with oxygen to produce hydroperoxides in-situ, which were then used as oxidan...The potential of carrying out oxidative desulfurization(ODS) using oxygen as an oxidant was explored in this work. n-Octane firstly reacted with oxygen to produce hydroperoxides in-situ, which were then used as oxidants to oxidize the dibenzothiophene(DBT) in the absence of catalysts. The hydroperoxides generated in-situ were effective in oxidizing DBT to its corresponding dibenzothiophene sulfone(DBTO_2) which was characterized by FT-IR and ~1H-NMR. The removal rate of DBT could reached 98.4% under conditions covering a temperaure of 140℃, a rection duration of 4 h, and an oxygen partial pressure of 0.4 MPa. The influences of different hydrocarbon components in diesel on DBT removal were investigated. The results showed that cyclohexane and n-dodecane had no effect on the removal of DBT, but xylene had a slight negative effect on DBT removal. A possible oxidation mechanism was proposed and the concentration of hydroperoxides in both O_2-oxidized octane and model diesel were detected.展开更多
AIM: To identify alkyl hydroperoxide reductase subunit C(AhpC) homologs in Bacillus subtilis(B. subtilis) and to characterize their structural and biochemical properties. AhpC is responsible for the detoxification of ...AIM: To identify alkyl hydroperoxide reductase subunit C(AhpC) homologs in Bacillus subtilis(B. subtilis) and to characterize their structural and biochemical properties. AhpC is responsible for the detoxification of reactive oxygen species in bacteria.METHODS: Two AhpC homologs(AhpC_H1 and AhpC_H2) were identified by searching the B. subtilis database; these were then cloned and expressed in Escherichia coli. AhpC mutants carrying substitutions of catalytically important Cys residues(C37S, C47 S, C166 S, C37/47 S, C37/166 S, C47/166 S, and C37/47/166 S for AhpC_H1; C52 S, C169 S, and C52/169 S for AhpC_H2) were obtained by site-directed mutagenesis and purified, and their structure-function relationship was analyzed. The B. subtilis ahp C genes were disrupted by the short flanking homology method, and the phenotypes of the resulting AhpC-deficient bacteria were examined.RESULTS: Comparative characterization of AhpC homologs indicates that AhpC_H1 contains an extra C37, which forms a disulfide bond with the peroxidatic C47, and behaves like an atypical 2-Cys AhpC, while AhpC_H2 functions like a typical 2-Cys AhpC. Tryptic digestion analysis demonstrated the presence of intramolecular Cys37-Cys47 linkage, which could be reduced by thioredoxin, resulting in the association of the dimer into higher-molecular-mass complexes. Peroxidase activity analysis of Cys→Ser mutants indicated that three Cys residues were involved in the catalysis. AhpC_H1 was resistant to inactivation by peroxide substrates, but had lower activity at physiological H2O2 concentrations compared to AhpC_H2, suggesting that in B. subtilis, the enzymes may be physiologically functional at different substrate concentrations. The exposure to organic peroxides induced AhpC_H1 expression, while AhpC_H1-deficient mutants exhibited growth retardation in the stationary phase, suggesting the role of AhpC_H1 as an antioxidant scavenger of lipid hydroperoxides and a stress-response factor in B. subtilis. CONCLUSION: AhpC_H1, a novel atypical 2-Cys AhpC, is functionally distinct from AhpC_H2, a typical 2-Cys AhpC.展开更多
Flavonoids are a major component in the traditional Chinese medicine Radix Ilicis Pubescentis.Previous studies have shown that the administration of Radix Ilicis Pubescentis total flavonoids is protective in cerebral ...Flavonoids are a major component in the traditional Chinese medicine Radix Ilicis Pubescentis.Previous studies have shown that the administration of Radix Ilicis Pubescentis total flavonoids is protective in cerebral ischemia.However,to our knowledge,no studies have examined whether the total flavonoids extracted from Radix Ilicis Pubescentis prevent or ameliorate neuronal damage following transient ischemic attacks.Therefore,Radix Ilicis Pubescentis total flavonoids question and the potential underlying mechanisms.Thus,beginning 3 days before the induction of a mouse model of transient ischemic attack using tert-butyl hydroperoxide injections,mice were intragastrically administered 0.3,0.15,or 0.075 g/kg of Radix Ilicis Pubescentis total flavonoids daily for 10 days.The results of spectrophotometric analyses demonstrated that Radix Ilicis Pubescentis total flavonoids enhanced oxygen free radical scavenging and reduced pathological alterations in the brain.Hematoxylin-eosin staining results showed that Radix Ilicis Pubescentis total flavonoids reduced hippocampal neuronal damage and cerebral vascular injury in this mouse model of transient ischemic attack.These results suggest that the antioxidant effects of Radix Ilicis Pubescentis total flavonoids alleviate the damage to brain tissue caused by transient ischemic attack.展开更多
Five fucoidan fractions from Laminaria japonica with different sulfate content and molecular weight were prepared by anion-exchange chromatography and mild acid hydrolysis. Their antioxidant effects on azo radicals 2-...Five fucoidan fractions from Laminaria japonica with different sulfate content and molecular weight were prepared by anion-exchange chromatography and mild acid hydrolysis. Their antioxidant effects on azo radicals 2-2'-Azobis (2-amidinopropane) dihydrochloride (AAPH) induced oxidation of human low-density lipoprotein (LDL) were evaluated by monitoring cholesteryl ester hydroperoxides (CHL-OOH) formation kinetics through reverse-phase high performance liquid chromatography (RP-HPLC) analysis. Fucoidan F - C with a low molecular mass of 2 000 ~8 000 and a sulfate content of 24.3% had much stronger protective antioxidant effect than other four fucoidan fractions on the hydrophilic radical AAPH induced LDL oxidation. However, the highly sulfated fucoidan fraction L - B with a molecular mass of 20 000 was completely ineffective in protecting LDL from the AAPH induced oxidation. The results suggested that both molecular mass and sulfate content of fucoidan played very important roles in their effects on the AAPH induced LDL oxidation.展开更多
Some 1-imino-3,3-disubstituted-1,3-dihydro isobenzofuran and 2-(1,1-disubstituted hydroxymethyl) benzamide derivatives have been obtained by the aminolysis of phthalide in the presence of triethylamine/aluminum chlori...Some 1-imino-3,3-disubstituted-1,3-dihydro isobenzofuran and 2-(1,1-disubstituted hydroxymethyl) benzamide derivatives have been obtained by the aminolysis of phthalide in the presence of triethylamine/aluminum chloride. 1-Benzylimino-3,3-disubstituted-1,3-dihydro isobenzofuran can be peroxidized to the corresponding hydroperoxides on exposure to the air for a long period. The structure was characterized by single crystal X-ray diffraction and the possible mechanism was suggested.展开更多
Phospholipid hydroperoxide glutathione peroxidase is an antioxidant enzyme that has the highest capability of reducing membrane-bound hydroperoxy lipids as compared to free organic and inorganic hydroperoxides amongst...Phospholipid hydroperoxide glutathione peroxidase is an antioxidant enzyme that has the highest capability of reducing membrane-bound hydroperoxy lipids as compared to free organic and inorganic hydroperoxides amongst the glutathione peroxidases.In this study,urea-induced effects on the inactivation and unfolding of a recombinant phospholipid hydroperoxide glutathione peroxidase(PHGPx)from Oryza sativa were investigated by means of circular dichroism and fluorescence spectroscopy.With the increase of urea concentration,the residual activity of OsPHGPx decreases correspondingly.When the urea concentration is above 5.0 mol/L,there was no residual activity.In addition,the observed changes in intrinsic tryptophan fluorescence,the binding of the hydrophobic fluorescence probe ANS,and the far UV CD describe a common dependence on the concentration of urea suggesting that the conformational features of the native OsPHGPx are lost in a highly cooperative single transition.The unfolding process comprises of three zones:the native base-line zone between 0 and 2.5 mol/L urea,the transition zone between 2.5 and 5.5 mol/L urea,and the denatured base-line zone above 5.5 mol/L urea.The transition zone has a midpoint at about 4.0 mol/L urea.展开更多
In 2019 the 150 kt/a unit for production of propylene oxide(PO)by the cumene hydroperoxide(CHP)process,the development of which is led by the SINOPEC Shanghai Research Institute of Petrochemical Technology(SRIPT),has ...In 2019 the 150 kt/a unit for production of propylene oxide(PO)by the cumene hydroperoxide(CHP)process,the development of which is led by the SINOPEC Shanghai Research Institute of Petrochemical Technology(SRIPT),has been envisaged in SINOPEC’s“Ten Key Technological Research Projects”to usher in a new phase for the R&D of this project.展开更多
Injury to mitochondria of macrophages caused by oxidized low density lipoprotein (Ox-LDL) and the role of lipid hydroperoxides (LOOH). lipid and protein in Ox-LDL on the injury were studied by measuring mito-chondrial...Injury to mitochondria of macrophages caused by oxidized low density lipoprotein (Ox-LDL) and the role of lipid hydroperoxides (LOOH). lipid and protein in Ox-LDL on the injury were studied by measuring mito-chondrial membrane potential (MMP) on ACAS570. The results showed that MMP decreased when macrophageswere treated by Ox-LDL. If LOOH in Ox-LDL was pre cleared by ebselen plus GSH. the decreased MMP could be recovered by about 20 %. Lipid moiety alone had no effect on IMP, but protein moiety could cause decrease ofMMP, the extent of the decrease was equivalent to that caused by Ox-LDL in which LOOH was pre-cleared by ebselen plus GSH.展开更多
The family of glutathione peroxidases encompasses, as far, three tetrameric glutathione'peroxidases (GPx) and the monomeric PHGPx. Although the overall homology between tetrameric enzymes and PHGPx is less than 30...The family of glutathione peroxidases encompasses, as far, three tetrameric glutathione'peroxidases (GPx) and the monomeric PHGPx. Although the overall homology between tetrameric enzymes and PHGPx is less than 30%, a pronounced similarity has been detected on clusters involved in the active site and a common catalytic triad (selenocysteine glutamine and tryptophan) has been defined by structural and kinetic data.A major peculiar feature of the reaction catalyzed by PHGPx is the possibility to accommodate large lipophilic substrates. This accounts for the observed dramatic antiperoxidant effect and the synergism with vitamin E.Moreover, the reduction of lipid hydroperoxides accounts also for the observed modulation of cycloxygenase and inhibition of 15-lipoxygenase.On the other hand, structural and kinetic data indicate that also the specificity of PHGPx for the donor substrate is not restricted to GSH and the recent observation the PHGPx binds to specific mitochondrial proteins, from which it is released by ionic strength and thiols, suggests a possible fole of this seleooenzyme'in catalyzing the specific oxidation of protein thiols,thus modulating the activity of cellular regulatory elements. on this light, the selenium mojety of PHGPx, reacting much faster that thiols with a peroxide, and then oxidizing specific protein thiols, would channel the oxidation toward protein targets, thus providing, by protein-protein interaction, the specificity of the redox transition展开更多
An unexpected compound, hydroperoxide (4) formed from (3), the exo-cycloaddition product, which was synthesized through the Lewis acid catlyzed intramolecular Diels-Alder (IMDA) reaction. Its structure was confirmed b...An unexpected compound, hydroperoxide (4) formed from (3), the exo-cycloaddition product, which was synthesized through the Lewis acid catlyzed intramolecular Diels-Alder (IMDA) reaction. Its structure was confirmed by spectra and X-Ray diffraction analysis, An 1O2oxidation mechanism was proposed.展开更多
Oxidative stress has been implicated in the pathophysiology of liver injury during xenobiotic and alcohol metabolism, ischemia/reperfusion injury. In this study we examined if ethanol acted as a pro-oxidant making cel...Oxidative stress has been implicated in the pathophysiology of liver injury during xenobiotic and alcohol metabolism, ischemia/reperfusion injury. In this study we examined if ethanol acted as a pro-oxidant making cells become more sensitive to tert-butylhydroperoxide (tBH) killing. Cell viability was determined in a rat hepatoma cell line (FTO2B) and rat primary hepatocytes in culture in the presence or absence of ethanol pretreatment. To elucidate the contribution of labile iron, deferoxamine (DF, an iron chelator) or lipid free radicals, N,N-diphenyl-p-phenylenediamine (DPPD, a lipid scavenger) were added to the ethanol tBH co-treatment. The levels of glutathione (GSH) and glutathione disulfide (GSSG) in the hepatocytes were also measured. Ethanol treatment (both pretreatment and co-treatment during the 3-hr tBH exposure) increased cell killing dramatically in both FTO2B cells and primary rat hepatocytes. Both DF and DPPD decreased ethanol-enhanced tBH cell killing in hepatocytes. These results demonstrated that co-treatment of FTO2B cells and primary rat hepatocytes with ethanol and tBH increased cell killing. The GSH level was dramatically reduced while GSSG level rose. Both DFP and DPPD reversed or protected the cells from this insult, indicating that ethanol was a pro-oxidant.展开更多
In the blood fluke Schistosoma mansoni a functionally active, monomeric, phospholipid hydroperoxide glutathione peroxidase (PHGPx) has been purified and characterized. This enzyme contains a catalytically active selen...In the blood fluke Schistosoma mansoni a functionally active, monomeric, phospholipid hydroperoxide glutathione peroxidase (PHGPx) has been purified and characterized. This enzyme contains a catalytically active selenocysteine. The protein has been shown to be the product of a cloned gene, previously referred to as a glutathione peroxidase gene. S. mansoni PHGPx has been found 5 times more abundant in female than in male worm extract. As in vertebrate PHGPx, homology alignment indicates that the residues involved in the glutathione binding by the tetrameric cellular glutathione peroxidase are mutated in the S. mansoni enzyme. Thus, this aspect appears a landmark of the PHGPx-type of glutathione peroxidases,which might be of functional relevance展开更多
On the model of Cu-induced liver fibrosis, the relationship between the activity of prooxidant-antioxidant system, immune system parameters, liver morphology and several physiological parameters (body temperature and ...On the model of Cu-induced liver fibrosis, the relationship between the activity of prooxidant-antioxidant system, immune system parameters, liver morphology and several physiological parameters (body temperature and performance ability of the animals, taking into account their ages) was investigated. Classical biochemical, immunological, histological and physiological methods of investigation were used. The subjects of the study were male Wistar rats of 3-month (young) and 20-month (old) age. For the induction of liver fibrosis, experimental animals were successively injected with copper sulfate (three times at intervals of 24 hours at a dose corresponding to 33% of the lethal one). It was shown that after five days of sulfate copper administration inflammatory reactions in the liver, damage of the vessel epithelium, an increase in collagen content, and other morphological changes were detected. At this time, the content of lipid hydroperoxides in the liver and blood serum was increased, the activity of a number of antioxidant enzymes was reduced, and the activity of aconitase was two times less compared to values in the control group. These changes correlated with a decrease in the amount and activity of phagocytic cells in the blood of experimental animals. Inhibition of the general metabolism was accompanied by a decrease in body temperature, loss of body weight and performance ability. The relationship between a specific metabolic pattern in animals with Cu-induced fibrosis was age-dependent. The formed specific adaptive metabolic pattern is unstable, and in the future it can be realized in one of three possible adaptive strategies, the choice of which is influenced by age.展开更多
The cardiovascular effects of vitamin C (VitC) could be mediated by epoxyeicosatrienoic acids (EETs). We aimed to study the mechanism of VitC-dependent microsomal formation of cis- and trans-EETs and the regulation of...The cardiovascular effects of vitamin C (VitC) could be mediated by epoxyeicosatrienoic acids (EETs). We aimed to study the mechanism of VitC-dependent microsomal formation of cis- and trans-EETs and the regulation of EET levels in rat isolated perfused kidneys and in vivo. VitC biphasically stimulated rat kidney microsomal cis- and trans-EET formation in a ratio of 1:2, involving the participation of lipid hydroperoxides (LOOHs), Fe2+ , and cytochrome P450 (CYP). Levels of LOOHs correlated with microsomal EET production. LOOH stimulation of CYP isoforms resulted in preferred trans- over cis-EET formation from arachidonic acid and was associated with the cleavage of LOOHs, which indicated a CYP peroxy-genase activity. EETs contributed to VitC-induced vasodilator responses in rat isolated perfused kidneys. VitC (1 mg/ml) given in the drinking water for 9 days doubled rat urinary EET excretion, increased plasma levels of EETs, mostly trans-EETs, by 40%, and reduced plasma levels of 20-hydroxyeicosatetraenoic acid. Depletion of VitC in brain cortex and kidney tissues by more than 20- and 50-fold, respectively, in gulonolactone oxidase-knockout mice was associated with mild increases in tissue EETs. These data suggest that LOOHs are a determinant factor for EET formation in vivo in which VitC exerts a key regulatory effect. VitC-activated CYP peroxygenase activity may represent a CYP interaction with lipoxygenases and cyclooxygenases to mediate the cardiovascular effects of VitC via formation of EETs.展开更多
Objectives: Smoking increases oxidative modification of LDL, associated with lower HDL plasma levels, systemic inflammatory response and endothelial dysfunction. We tested the hypothesis that the risk status for coron...Objectives: Smoking increases oxidative modification of LDL, associated with lower HDL plasma levels, systemic inflammatory response and endothelial dysfunction. We tested the hypothesis that the risk status for coronary atherosclerosis disease (CAD) of cigarettes smokers might be identified by means of serum oxidative levels and vascular inflammation determination. Design and Methods: Oxidative stress levels, cytokines, and the metabolic status were investigated on 499 subjects admitted to our institute. The association between biomarkers and smoking habits in the presence/absence of disease and with the number of vessel affected, was studied. Results: Oxidative stress and inflammatory levels (p < 0.001) were strongly induced by smoking habits. Serum values of the subjects categorised as CAD, non CAD and healthy subjects differed significantly (p < 0.001) only for the degree of oxidative stress. Glycaemia was able to affect C-reactive protein serum levels with a positive association (p < 0.05). The analysis of the study population indicated that serum oxidative stress levels significantly increased with increasing number of vessels affected (p < 0.01). When statistical analysis was performed separately in both smoking groups, smokers did not show any particular difference for both oxidative stress and inflammation markers between the two groups of cardiovascular patients (CAD and non CAD) and the control group, while for non smokers, the differences were evident. Conclusion: These findings indicate that the considered biomarkers, especially oxidative stress, can be useful to predict the biological damage caused by cigarette smoking, as well as to identify subjects characterised by a higher risk of cardiovascular event, but cannot evaluate the presence of disease in subjects with smoking habit.展开更多
It is demonstrated that (3Z)-nonenal (NON) and (3Z)-hexenal (HEX) are oxidized in a cascade by lipoxygenase (LOX) and hydroperoxide peroxygenase (HP peroxygenase) into (2E)-4-hydroxy-2- nonenal (HNE) and (2E)-4-hydrox...It is demonstrated that (3Z)-nonenal (NON) and (3Z)-hexenal (HEX) are oxidized in a cascade by lipoxygenase (LOX) and hydroperoxide peroxygenase (HP peroxygenase) into (2E)-4-hydroxy-2- nonenal (HNE) and (2E)-4-hydroxy-2-hexenal (HHE), respectively. In turn, HNE inactivates LOX terminating the cascade. The hydroxy-alkenals produced serve to inhibit plant pathogens, which initiated the cascade. In addition to LOX, other unknown oxygenases may be involved in the cascade.展开更多
Antioxidant activity of interaction products of the studied compounds with tret-Butyl hydroperoxide is studied. New, more active acceptors of free radicals are formed in the process of oxidative transformations of ini...Antioxidant activity of interaction products of the studied compounds with tret-Butyl hydroperoxide is studied. New, more active acceptors of free radicals are formed in the process of oxidative transformations of initial compounds. It is investigated that the products have high inhibiting properties. The parameter fk, characterizing inhibitory effect of an inhibitor is studied.展开更多
基金Supported by the National Natural Science Foundation of China(No.20572058)
文摘CuCl-catalyzed oxidative N-demethylation of arylamines proceeded in the presence of tert-butyl hydroperoxide. The one-electron transfer route of oxidative N-demethylation competed favorably with the H-atom abstraction route.
基金Supported by the National Natural Science Foundation of China,No.81573219Heilongjiang Province Office of Education Foundation,No.12541288
文摘AIM: To investigate catalase(Kat A) and alkyl hydroperoxide reductase(Ahp C) antibodies of Helicobacter pylori as biomarkers for gastric cancer(GC).METHODS: This study included 232 cases and 264 controls. Recombinant Kat A and Ahp C proteins were constructed and the levels of antibodies were tested by indirect enzyme-linked immunosorbent assay(ELISA). Logistic regression was applied to analyze the relationships between Kat A, Ahp C and GC. The χ2 trend test was used to evaluate the dose-response relationships between serum Kat A and Ahp C antibody levels and GC. Receiver operating characteristic(ROC) curve was used to evaluate the screening accuracy of Kat A and Ahp C as biomarkers. Combined analysis was used to observe screening accuracy of predictors for GC.RESULTS: In all subjects, the association between Kat A and Ahp C and GC risk was significant(P < 0.001) with odds ratio(OR) = 12.84(95%CI: 7.79-21.15)and OR = 2.4(95%CI: 1.55-3.73), respectively. Kat A and Ahp C antibody levels were strongly related to GC risk with a dose-dependent effect(P for trend < 0.001). The area under the ROC(AUC) for Kat A was 0.806, providing a sensitivity of 66.81% and specificity of 86.36%; and the AUC for Ahp C was 0.615, with a sensitivity of 75.65% and specificity of 45.49%. The AUC was 0.906 for Kat A and flagella protein A(Fla A) combined analysis.CONCLUSION: Serum Kat A and Ahp C antibodies are associated with GC risk and Kat A may serve as a biomarker for GC. Kat A/Fla A combined analysis improved screening accuracy.
基金the Undergraduate Innovation and Entrepreneurship Training Project (201710057009) for providing funding and support for this research
文摘The potential of carrying out oxidative desulfurization(ODS) using oxygen as an oxidant was explored in this work. n-Octane firstly reacted with oxygen to produce hydroperoxides in-situ, which were then used as oxidants to oxidize the dibenzothiophene(DBT) in the absence of catalysts. The hydroperoxides generated in-situ were effective in oxidizing DBT to its corresponding dibenzothiophene sulfone(DBTO_2) which was characterized by FT-IR and ~1H-NMR. The removal rate of DBT could reached 98.4% under conditions covering a temperaure of 140℃, a rection duration of 4 h, and an oxygen partial pressure of 0.4 MPa. The influences of different hydrocarbon components in diesel on DBT removal were investigated. The results showed that cyclohexane and n-dodecane had no effect on the removal of DBT, but xylene had a slight negative effect on DBT removal. A possible oxidation mechanism was proposed and the concentration of hydroperoxides in both O_2-oxidized octane and model diesel were detected.
基金Supported by The Basic Science Research Program through the Korea Research Foundation Grant funded by the Ministry of Education,Science,and Technology(NRF-2011-0008913)Kim IH and Cha MK performed this work during their research sabbatical supported by Paichai University(2014-2015)
文摘AIM: To identify alkyl hydroperoxide reductase subunit C(AhpC) homologs in Bacillus subtilis(B. subtilis) and to characterize their structural and biochemical properties. AhpC is responsible for the detoxification of reactive oxygen species in bacteria.METHODS: Two AhpC homologs(AhpC_H1 and AhpC_H2) were identified by searching the B. subtilis database; these were then cloned and expressed in Escherichia coli. AhpC mutants carrying substitutions of catalytically important Cys residues(C37S, C47 S, C166 S, C37/47 S, C37/166 S, C47/166 S, and C37/47/166 S for AhpC_H1; C52 S, C169 S, and C52/169 S for AhpC_H2) were obtained by site-directed mutagenesis and purified, and their structure-function relationship was analyzed. The B. subtilis ahp C genes were disrupted by the short flanking homology method, and the phenotypes of the resulting AhpC-deficient bacteria were examined.RESULTS: Comparative characterization of AhpC homologs indicates that AhpC_H1 contains an extra C37, which forms a disulfide bond with the peroxidatic C47, and behaves like an atypical 2-Cys AhpC, while AhpC_H2 functions like a typical 2-Cys AhpC. Tryptic digestion analysis demonstrated the presence of intramolecular Cys37-Cys47 linkage, which could be reduced by thioredoxin, resulting in the association of the dimer into higher-molecular-mass complexes. Peroxidase activity analysis of Cys→Ser mutants indicated that three Cys residues were involved in the catalysis. AhpC_H1 was resistant to inactivation by peroxide substrates, but had lower activity at physiological H2O2 concentrations compared to AhpC_H2, suggesting that in B. subtilis, the enzymes may be physiologically functional at different substrate concentrations. The exposure to organic peroxides induced AhpC_H1 expression, while AhpC_H1-deficient mutants exhibited growth retardation in the stationary phase, suggesting the role of AhpC_H1 as an antioxidant scavenger of lipid hydroperoxides and a stress-response factor in B. subtilis. CONCLUSION: AhpC_H1, a novel atypical 2-Cys AhpC, is functionally distinct from AhpC_H2, a typical 2-Cys AhpC.
基金supported by the State"Major New Drug Creation"Major Science and Technology Project of China,No.2009ZX09103-324a grant from the Henan Provincial Science and Technology Innovation Team in University in China,No.2012IRTSTHN011
文摘Flavonoids are a major component in the traditional Chinese medicine Radix Ilicis Pubescentis.Previous studies have shown that the administration of Radix Ilicis Pubescentis total flavonoids is protective in cerebral ischemia.However,to our knowledge,no studies have examined whether the total flavonoids extracted from Radix Ilicis Pubescentis prevent or ameliorate neuronal damage following transient ischemic attacks.Therefore,Radix Ilicis Pubescentis total flavonoids question and the potential underlying mechanisms.Thus,beginning 3 days before the induction of a mouse model of transient ischemic attack using tert-butyl hydroperoxide injections,mice were intragastrically administered 0.3,0.15,or 0.075 g/kg of Radix Ilicis Pubescentis total flavonoids daily for 10 days.The results of spectrophotometric analyses demonstrated that Radix Ilicis Pubescentis total flavonoids enhanced oxygen free radical scavenging and reduced pathological alterations in the brain.Hematoxylin-eosin staining results showed that Radix Ilicis Pubescentis total flavonoids reduced hippocampal neuronal damage and cerebral vascular injury in this mouse model of transient ischemic attack.These results suggest that the antioxidant effects of Radix Ilicis Pubescentis total flavonoids alleviate the damage to brain tissue caused by transient ischemic attack.
基金supported by the National Natural Science Foundation of China under contract No.30471349Guangdong Natural Science Foundation under contract No.011256.
文摘Five fucoidan fractions from Laminaria japonica with different sulfate content and molecular weight were prepared by anion-exchange chromatography and mild acid hydrolysis. Their antioxidant effects on azo radicals 2-2'-Azobis (2-amidinopropane) dihydrochloride (AAPH) induced oxidation of human low-density lipoprotein (LDL) were evaluated by monitoring cholesteryl ester hydroperoxides (CHL-OOH) formation kinetics through reverse-phase high performance liquid chromatography (RP-HPLC) analysis. Fucoidan F - C with a low molecular mass of 2 000 ~8 000 and a sulfate content of 24.3% had much stronger protective antioxidant effect than other four fucoidan fractions on the hydrophilic radical AAPH induced LDL oxidation. However, the highly sulfated fucoidan fraction L - B with a molecular mass of 20 000 was completely ineffective in protecting LDL from the AAPH induced oxidation. The results suggested that both molecular mass and sulfate content of fucoidan played very important roles in their effects on the AAPH induced LDL oxidation.
基金the Postdoctoral Foundation of China for the tlnancial support.
文摘Some 1-imino-3,3-disubstituted-1,3-dihydro isobenzofuran and 2-(1,1-disubstituted hydroxymethyl) benzamide derivatives have been obtained by the aminolysis of phthalide in the presence of triethylamine/aluminum chloride. 1-Benzylimino-3,3-disubstituted-1,3-dihydro isobenzofuran can be peroxidized to the corresponding hydroperoxides on exposure to the air for a long period. The structure was characterized by single crystal X-ray diffraction and the possible mechanism was suggested.
基金Supported by the National Basic Research Program of China(No.2006CB101706)the Hi-tech Research and DevelopmentProgram of China(No.2007AA100604)the National Natural Science Foundation of China(Nos.30170080and39770078).
文摘Phospholipid hydroperoxide glutathione peroxidase is an antioxidant enzyme that has the highest capability of reducing membrane-bound hydroperoxy lipids as compared to free organic and inorganic hydroperoxides amongst the glutathione peroxidases.In this study,urea-induced effects on the inactivation and unfolding of a recombinant phospholipid hydroperoxide glutathione peroxidase(PHGPx)from Oryza sativa were investigated by means of circular dichroism and fluorescence spectroscopy.With the increase of urea concentration,the residual activity of OsPHGPx decreases correspondingly.When the urea concentration is above 5.0 mol/L,there was no residual activity.In addition,the observed changes in intrinsic tryptophan fluorescence,the binding of the hydrophobic fluorescence probe ANS,and the far UV CD describe a common dependence on the concentration of urea suggesting that the conformational features of the native OsPHGPx are lost in a highly cooperative single transition.The unfolding process comprises of three zones:the native base-line zone between 0 and 2.5 mol/L urea,the transition zone between 2.5 and 5.5 mol/L urea,and the denatured base-line zone above 5.5 mol/L urea.The transition zone has a midpoint at about 4.0 mol/L urea.
文摘In 2019 the 150 kt/a unit for production of propylene oxide(PO)by the cumene hydroperoxide(CHP)process,the development of which is led by the SINOPEC Shanghai Research Institute of Petrochemical Technology(SRIPT),has been envisaged in SINOPEC’s“Ten Key Technological Research Projects”to usher in a new phase for the R&D of this project.
文摘Injury to mitochondria of macrophages caused by oxidized low density lipoprotein (Ox-LDL) and the role of lipid hydroperoxides (LOOH). lipid and protein in Ox-LDL on the injury were studied by measuring mito-chondrial membrane potential (MMP) on ACAS570. The results showed that MMP decreased when macrophageswere treated by Ox-LDL. If LOOH in Ox-LDL was pre cleared by ebselen plus GSH. the decreased MMP could be recovered by about 20 %. Lipid moiety alone had no effect on IMP, but protein moiety could cause decrease ofMMP, the extent of the decrease was equivalent to that caused by Ox-LDL in which LOOH was pre-cleared by ebselen plus GSH.
文摘The family of glutathione peroxidases encompasses, as far, three tetrameric glutathione'peroxidases (GPx) and the monomeric PHGPx. Although the overall homology between tetrameric enzymes and PHGPx is less than 30%, a pronounced similarity has been detected on clusters involved in the active site and a common catalytic triad (selenocysteine glutamine and tryptophan) has been defined by structural and kinetic data.A major peculiar feature of the reaction catalyzed by PHGPx is the possibility to accommodate large lipophilic substrates. This accounts for the observed dramatic antiperoxidant effect and the synergism with vitamin E.Moreover, the reduction of lipid hydroperoxides accounts also for the observed modulation of cycloxygenase and inhibition of 15-lipoxygenase.On the other hand, structural and kinetic data indicate that also the specificity of PHGPx for the donor substrate is not restricted to GSH and the recent observation the PHGPx binds to specific mitochondrial proteins, from which it is released by ionic strength and thiols, suggests a possible fole of this seleooenzyme'in catalyzing the specific oxidation of protein thiols,thus modulating the activity of cellular regulatory elements. on this light, the selenium mojety of PHGPx, reacting much faster that thiols with a peroxide, and then oxidizing specific protein thiols, would channel the oxidation toward protein targets, thus providing, by protein-protein interaction, the specificity of the redox transition
文摘An unexpected compound, hydroperoxide (4) formed from (3), the exo-cycloaddition product, which was synthesized through the Lewis acid catlyzed intramolecular Diels-Alder (IMDA) reaction. Its structure was confirmed by spectra and X-Ray diffraction analysis, An 1O2oxidation mechanism was proposed.
文摘Oxidative stress has been implicated in the pathophysiology of liver injury during xenobiotic and alcohol metabolism, ischemia/reperfusion injury. In this study we examined if ethanol acted as a pro-oxidant making cells become more sensitive to tert-butylhydroperoxide (tBH) killing. Cell viability was determined in a rat hepatoma cell line (FTO2B) and rat primary hepatocytes in culture in the presence or absence of ethanol pretreatment. To elucidate the contribution of labile iron, deferoxamine (DF, an iron chelator) or lipid free radicals, N,N-diphenyl-p-phenylenediamine (DPPD, a lipid scavenger) were added to the ethanol tBH co-treatment. The levels of glutathione (GSH) and glutathione disulfide (GSSG) in the hepatocytes were also measured. Ethanol treatment (both pretreatment and co-treatment during the 3-hr tBH exposure) increased cell killing dramatically in both FTO2B cells and primary rat hepatocytes. Both DF and DPPD decreased ethanol-enhanced tBH cell killing in hepatocytes. These results demonstrated that co-treatment of FTO2B cells and primary rat hepatocytes with ethanol and tBH increased cell killing. The GSH level was dramatically reduced while GSSG level rose. Both DFP and DPPD reversed or protected the cells from this insult, indicating that ethanol was a pro-oxidant.
文摘In the blood fluke Schistosoma mansoni a functionally active, monomeric, phospholipid hydroperoxide glutathione peroxidase (PHGPx) has been purified and characterized. This enzyme contains a catalytically active selenocysteine. The protein has been shown to be the product of a cloned gene, previously referred to as a glutathione peroxidase gene. S. mansoni PHGPx has been found 5 times more abundant in female than in male worm extract. As in vertebrate PHGPx, homology alignment indicates that the residues involved in the glutathione binding by the tetrameric cellular glutathione peroxidase are mutated in the S. mansoni enzyme. Thus, this aspect appears a landmark of the PHGPx-type of glutathione peroxidases,which might be of functional relevance
文摘On the model of Cu-induced liver fibrosis, the relationship between the activity of prooxidant-antioxidant system, immune system parameters, liver morphology and several physiological parameters (body temperature and performance ability of the animals, taking into account their ages) was investigated. Classical biochemical, immunological, histological and physiological methods of investigation were used. The subjects of the study were male Wistar rats of 3-month (young) and 20-month (old) age. For the induction of liver fibrosis, experimental animals were successively injected with copper sulfate (three times at intervals of 24 hours at a dose corresponding to 33% of the lethal one). It was shown that after five days of sulfate copper administration inflammatory reactions in the liver, damage of the vessel epithelium, an increase in collagen content, and other morphological changes were detected. At this time, the content of lipid hydroperoxides in the liver and blood serum was increased, the activity of a number of antioxidant enzymes was reduced, and the activity of aconitase was two times less compared to values in the control group. These changes correlated with a decrease in the amount and activity of phagocytic cells in the blood of experimental animals. Inhibition of the general metabolism was accompanied by a decrease in body temperature, loss of body weight and performance ability. The relationship between a specific metabolic pattern in animals with Cu-induced fibrosis was age-dependent. The formed specific adaptive metabolic pattern is unstable, and in the future it can be realized in one of three possible adaptive strategies, the choice of which is influenced by age.
文摘The cardiovascular effects of vitamin C (VitC) could be mediated by epoxyeicosatrienoic acids (EETs). We aimed to study the mechanism of VitC-dependent microsomal formation of cis- and trans-EETs and the regulation of EET levels in rat isolated perfused kidneys and in vivo. VitC biphasically stimulated rat kidney microsomal cis- and trans-EET formation in a ratio of 1:2, involving the participation of lipid hydroperoxides (LOOHs), Fe2+ , and cytochrome P450 (CYP). Levels of LOOHs correlated with microsomal EET production. LOOH stimulation of CYP isoforms resulted in preferred trans- over cis-EET formation from arachidonic acid and was associated with the cleavage of LOOHs, which indicated a CYP peroxy-genase activity. EETs contributed to VitC-induced vasodilator responses in rat isolated perfused kidneys. VitC (1 mg/ml) given in the drinking water for 9 days doubled rat urinary EET excretion, increased plasma levels of EETs, mostly trans-EETs, by 40%, and reduced plasma levels of 20-hydroxyeicosatetraenoic acid. Depletion of VitC in brain cortex and kidney tissues by more than 20- and 50-fold, respectively, in gulonolactone oxidase-knockout mice was associated with mild increases in tissue EETs. These data suggest that LOOHs are a determinant factor for EET formation in vivo in which VitC exerts a key regulatory effect. VitC-activated CYP peroxygenase activity may represent a CYP interaction with lipoxygenases and cyclooxygenases to mediate the cardiovascular effects of VitC via formation of EETs.
文摘Objectives: Smoking increases oxidative modification of LDL, associated with lower HDL plasma levels, systemic inflammatory response and endothelial dysfunction. We tested the hypothesis that the risk status for coronary atherosclerosis disease (CAD) of cigarettes smokers might be identified by means of serum oxidative levels and vascular inflammation determination. Design and Methods: Oxidative stress levels, cytokines, and the metabolic status were investigated on 499 subjects admitted to our institute. The association between biomarkers and smoking habits in the presence/absence of disease and with the number of vessel affected, was studied. Results: Oxidative stress and inflammatory levels (p < 0.001) were strongly induced by smoking habits. Serum values of the subjects categorised as CAD, non CAD and healthy subjects differed significantly (p < 0.001) only for the degree of oxidative stress. Glycaemia was able to affect C-reactive protein serum levels with a positive association (p < 0.05). The analysis of the study population indicated that serum oxidative stress levels significantly increased with increasing number of vessels affected (p < 0.01). When statistical analysis was performed separately in both smoking groups, smokers did not show any particular difference for both oxidative stress and inflammation markers between the two groups of cardiovascular patients (CAD and non CAD) and the control group, while for non smokers, the differences were evident. Conclusion: These findings indicate that the considered biomarkers, especially oxidative stress, can be useful to predict the biological damage caused by cigarette smoking, as well as to identify subjects characterised by a higher risk of cardiovascular event, but cannot evaluate the presence of disease in subjects with smoking habit.
文摘It is demonstrated that (3Z)-nonenal (NON) and (3Z)-hexenal (HEX) are oxidized in a cascade by lipoxygenase (LOX) and hydroperoxide peroxygenase (HP peroxygenase) into (2E)-4-hydroxy-2- nonenal (HNE) and (2E)-4-hydroxy-2-hexenal (HHE), respectively. In turn, HNE inactivates LOX terminating the cascade. The hydroxy-alkenals produced serve to inhibit plant pathogens, which initiated the cascade. In addition to LOX, other unknown oxygenases may be involved in the cascade.
文摘Antioxidant activity of interaction products of the studied compounds with tret-Butyl hydroperoxide is studied. New, more active acceptors of free radicals are formed in the process of oxidative transformations of initial compounds. It is investigated that the products have high inhibiting properties. The parameter fk, characterizing inhibitory effect of an inhibitor is studied.