• Archives of Pharmacal Research
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• v.26 no.12
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• pp.1047-1054
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• 2003

Molecular chaperones have a crucial role in the folding of nascent polypeptides in endoplasmic reticulum. Some of them are known to be sensitive to the modification by electrophilic metabolites of organic pro-toxicants. In order to identify chaperone proteins sensitive to alkyators, ER extract was subjected to alkylation by 4-acetamido-4 -maleimidyl-stilbene-2,2 -disulfonate (AMS), and subsequent SDS-PAGE analyses. Protein spots, with molecular mass of 160, 100, 57 and 36 kDa, were found to be sensitive to AMS alkylation, and one abundant chaperon protein was identified to be protein disulfide isomerase (PDI) in comparison with the purified PDI. To see the reactivity of PDI with cysteine alkylators, the reduced form ($PDI_{red}$) of PDI was incubated with various alkylators containing Michael acceptor structure for 30 min at $38^{\circ}C$ at pH 6.3, and the remaining activity was determined by the insulin reduction assay. Iodoacetamide or N-ethylmaleimide at 0.1 mM remarkably inactivated $PDI_{red}$ with N-ethylmaleimide being more potent than iodoacetamide. A partial inactivation of $PDI_{oxid}$ was expressed by iodoacetamide, but not N-ethylmaleimide (NEM) at pH 6.3. Of Michael acceptor compounds tested, 1,4-benzoquinone ($IC_{50}, 15 \mu$ M) was the most potent, followed by 4-hydroxy-2-nonenal and 1,4-naphthoquinone. In contrast, 1,2-naphthoquinone, devoid of a remarkable inactivation action, was effective to cause the oxidative conversion of $PDI_{red}$ to $PDI_{oxid}$. Thus, the action of Michael acceptor compounds differed greatly depending on their structure. Based on these, it is proposed that POI, one of chaperone proteins in ER, could be susceptible to endogenous or xenobiotic Michael acceptor compounds in vivo system.

• Journal of Veterinary Clinics
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• v.28 no.5
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• pp.473-478
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• 2011

The study evaluated the antioxidant effects of ascorbic acid (AA) against oxidative stress during laparotomy in dogs under general anesthesia using isoflurane. Twelve dogs were randomly assigned to either the ascorbic acid group (AAG) or the sham group (SG). AAG received intravenous dosage of 100 mg/animal of standard AA 10 minutes before anesthesia. Plasma levels of cortisol, glucose, total oxidant status (TOS), total antioxidant status (TAS), and oxidative stress index (OSI) were measured. Cortisol level increased significantly with time in both groups (p < 0.05). The change of glucose levels was not significantly different between both groups. TOS and OSI increased significantly with time in the SG (p < 0.05), whereas it did not significantly change with time in the AAG. The TOS and OSI of the AAG were significantly lower than in the SG (p < 0.05). However, TAS did not significantly change between both groups. The results suggest that the decrease of TOS in the AAG might be related to the conversion of antioxidants to oxidants. The decrease of OSI indicates that the decrease of reactive oxygen species (i.e., oxidative stress) produced at the site of injury is able to decrease surgical side effects of abnormal blood circulation, organ failure, and inflammation. Therefore, AA can be used to protect a surgical patient from oxidative stress in canine laparotomy.

• Carbon letters
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• v.28
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• pp.38-46
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• 2018

Modified pitch A (MPA) and modified pitch B (MPB) were prepared by oxidative polymerization and thermal polycondensation reaction with refined pitch as the raw material, respectively. The toluene soluble components (TS-1 and TS-2) were obtained by solvent extraction from MPA and MPB, separately. The Flynn-Wall-Ozawa method and Kissinger-Akahira-Sunose method were used to calculate the pyrolysis activation energy of TS. The Satava-Sestak method was used to investigate the pyrolysis kinetic parameters of TS. Moreover, the optical microstructure of the thermal conversion products (TS-1-P and TS-2-P) by calcination shows that TS-1-P has more contents of mosaic structure and lower contents of fine fiber structure than TS-2-P. The research result obtained by a combination of X-ray diffraction and the curve-fitting method revealed that the ratios of ordered carbon crystallite (Ig) in TS-1-P and TS-2-P were 0.3793 and 0.4417, respectively. The distributions of carbon crystallite on TS-1-P and TS-2-P were calculated by Raman spectrum and curve-fitting analysis. They show that the thermal conversion product of TS-2 has a better graphite crystallite structure than TS-1.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.3009-3016
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• 2012

This study evaluated the use of iron-impregnated SBA-15 (Fe/SBA-15) as a catalyst for the oxidative degradation of persistent phenol analogues, such as 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), 2-nitrophenol (2-NP), 4-nitrophenol (4-NP) and 2,4,6-trichlorophenol (2,4,6-TCP) in water. The oxidation reactions were carried out with reaction time, concentration of the phenols, amount of the catalysts, reaction temperature, pH of the reaction mixture as the process variables with or without using hydrogen peroxide as the oxidizing agent. The conversion achieved with Fe/SBA-15 at 353 K for 2-CP, 4-CP, 2-NP, 4-NP, 2,4,6-TCP was 80.2, 71.2, 53.1, 62.8, 77.3% in 5h with a reactant to $H_2O_2$ mole ratio of 1:1, and 85.7, 65.8, 61.9, 63.7, 78.1% in the absence of $H_2O_2$, respectively. The reactions followed pseudo first order kinetics. The leachability study indicated that the catalyst released very little iron into water and therefore, the possibility of secondary pollution is negligible.

• YAKHAK HOEJI
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• v.53 no.6
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• pp.314-320
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• 2009

We examined metabolic conversion of cysteine into glutathione (GSH) and taurine in rat liver under oxidative stress. Administration of tert-butylhydroperoxide (t-BHP) into the portal vein of male rats resulted in a rapid elevation of serum sorbitol dehydrogenase, alanine aminotransferase, and aspartate aminotransferase activities, which decreased gradually in 24 hr. Hepatic cysteine concentration was reduced in 3 hr, and recovered progressively, reaching a level greater than 200% of the normal value in 24 hr. GSH was increased both in liver and blood at 9 hr after t-BHP challenge, whereas hypotaurine or taurine was not altered. $\gamma$-Glutamylcysteine synthetase (GCS) activity was increased from 9 hr after t-BHP treatment, but protein expression of the GCS-heavy subunit was not changed in liver. Activity or expression of cysteine dioxygenase was not affected by t-BHP treatment. Taken together, these data show that an acute oxidant challenge to the rats may induce upregulation of cysteine availability and GCS activity, resulting in an enhancement of hepatic GSH synthesis, but the increased cysteine level does not stimulate taurine synthesis via cysteine sulfinate pathway. It is indicated that the regulation of GSH and taurine biosynthesis from cysteine is not solely dependent on the cysteine concentration in rat liver under oxidative stress.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.225-230
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• 2013

A new heteropolyanion-based ionic ($[Hmim]_5PMo_{10}V_2O_{40}$) was synthesized by the reaction of molybdovanadophosphoric acid ($H_5PMo_{10}O_{40}$) with N-methylimidazole. [$[Hmim]_5PMo_{10}V_2O_{40}$ showed a high catalytic activity in the oxidative desulfurization of sulfur-containing compounds in 1-methylimidazolium tetrafluoroborate ($[Hmim]BF_4$) ionic liquid using 30% aqueous $H_2O_2$ as the oxidant. The catalytic system was of high activity, simplified workup and flexible recyclability. The catalytic oxidation reactivity of sulfur-containing compounds decreased in the order dibenzothiophene (DBT) > 4,6-dimethyldibenzothiophene (4,6-DMDBT) > benzothiophene (BT). The influences of various parameters including reaction time (t) and temperature (T), catalyst dosage, and oxidant to sulfur molar ratio n(O)/n(S) on the desulfurization of model oil were investigated in details. 99.1% of DBT conversion in the model oil was achieved at atmospheric pressure under the optimal conditions: n(O)/n(S) = 4:1, $60^{\circ}C$, 100 min and molar ratio of catalyst to sulfur of 0.062. The ionic liquid can be recycled six times without significant decrease in activity.

• Environmental Mutagens and Carcinogens
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• v.16 no.1
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• pp.13-18
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• 1996

One mechanism of free-radical production by ethanol is suggested to be through the intracellular conversion of XDH to XO by increased ratio of NADH to NAD. The major mechanism for physiological compensation of cytosolic NADH/NAD balance is the malate/aspartate shutfie. Therefore, it is important to develop the method to improve the efficiency of malate/aspartate shuttle in ethanol metabolism. In the present study, various amino acids and organic acid involved in the shuttle were tested for their functional efficiency in modulating shuttle in the ethanol-perfused rat liver. The rate of ethanol oxidation in the liver perfused with aspartate alone or aspartate in combination with pyruvate, respectively, was increased by about 10% compared to control liver, but not in the tissues perfused with glummate, cysteine or pyruvate alone. Though glummate, cysteine and pyravate did not affect the ethanol oxidation significanfiy, they showed some suppresive effect on the ethanol-induced radical generation monitored by protein carbonylation analysis. Among the tested components, aspartate is confirmed to be the most efficient as a metabolic regulator for both ethanol oxidation and ethanol-induced oxidative stress in our perfusion system. These effects of aspartate would result from NAD recycling by its supplementation through the coupled aspartate aminotransferase/malate dehydrogenase reactions and the malate-aspartate shuttle.

• Preventive Nutrition and Food Science
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• v.20 no.1
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• pp.22-28
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• 2015

Phenolic rich ethyl acetate fraction (EAF) from lotus leaves was prepared and its bioactive components, antioxidant and cytoprotective effects were investigated. EAF showed high total phenolic content and flavonoid content and contained rutin ($11,331.3{\pm}4.5mg/100g\;EAF$), catechin ($10,853.8{\pm}5.8mg/100g\;EAF$), sinapic acid ($1,961.3{\pm}5.6mg/100g\;EAF$), chlorogenic acid ($631.9{\pm}2.3mg/100g\;EAF$), syringic acid ($512.3{\pm}2.5mg/100g\;EAF$), and quercetin ($415.0{\pm}2.1mg/100g\;EAF$). EAF exerted the $IC_{50}$ of $4.46{\mu}g/mL$ and $5.35{\mu}g/mL$ toward DPPH and ABTS cation radicals, respectively, and showed strong reducing power, which was better than that of ascorbic acid, a positive control. Additionally, EAF protected hydroxyl radical-induced DNA damage indicated by the conversion of supercoiled pBR322 plasmid DNA to the open circular form and inhibited lipid peroxidation of polyunsaturated fatty acid in a linoleic acid emulsion. In cultured hepatocytes, EAF exerted a cytoprotective effect against oxidative stress by inhibiting intracellular reactive oxygen species formation and membrane lipid peroxidation. In addition, depletion of glutathione under oxidative stress was remarkably restored by treatment with EAF. The results suggest that EAF have great potential to be used against oxidative stress-induced health conditions.

• Journal of Hydrogen and New Energy
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• v.29 no.4
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• pp.331-338
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• 2018

In this study, sulfonated PAES block copolymers have been synthesized via nucleophilic substitution reaction. Hydrophobic oligomer was prepared using 2,6-dihydroxynaphthalene and bis(4-chlorophenyl) sulfone, whereas hydrophilic oligomer was prepared using sulfonated bis(4-chlorophenyl) sulfone and bis(4-hydroxyphenyl) sulfone. The chemical structure of polymers was analyzed by $^1H$ NMR, FT-IR and GPC. The thermal properties of polymers were measured by TGA and DSC. The oxidative stability of membranes was investigated by Fenton's test. Furthermore, the proton conductivity of membrane was found to be 26 mS/cm at $90^{\circ}C$. All physiochemical properties suggest that fabricated membrane have a great potential for applications in PEMFC.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.97.2-97.2
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• 2011

Pt-Ru and Pt-Ni bimetallic catalysts were prepared and tested for heavy hydrocarbon reforming. Metals were supported on CGO($Ce_{0.8}Gd_{0.2}O_{2.0-x}$) by incipient wetness method. The prepared catalysts were characterized by Temperature programmed reduction(TPR). Oxidative steam reforming of n-dodecane was conducted to compare the activity of the catalysts. The reforming temperature was varied from $500^{\circ}C$ to $800^{\circ}C$ at fixed $O_2$/C of 0.3, $H_2O$/C of 3.0 and GHSV of 5,000/h.Reduction peaks of metal oxide, surface CGO and bulk CGO were detected. Reduction temperature of metal oxide decreased over the bi-metallic catalysts. It is considered that interaction between metals leads to decrease interaction between metal and oxygen. On the other hands, reduction temperatures of surface CGO were dectected in the order of Pt-Ru > Pt-Ni > Pt. low reduction temperatures of surface CGO indicates the low activation energy for oxygen ion conduction to metal. Oxygen ion conduction is known as de-coking mechanism of ionic conducting supports such as CGO. In activity test, fuel conversion was in the same order of Pt-Ru > Pt-Ni > Pt. Especially, 100% of fuel conversion was obtained over Pt-Ru catalysts at $500^{\circ}C$.