• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.711-714
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• 2004

Peroxynitrite enters erythrocytes through band 3 anion exchanger and oxidizes cytosolic proteins therein. As a protein associated with band 3, carbonic anhydrase II may suffer from peroxynitrite-induced oxidative damages. Esterase activity of carbonic anhydrase II decreased as the concentration of peroxynitrite increased. Neither hydrogen peroxide nor hypochlorite affected the enzyme activity. Inactivation of the enzyme was in parallel with the release of zinc ion, which is a component of the enzyme's active site. SDS-PAGE of peroxynitrite-treated samples showed no indication of fragmentation but non-denaturing PAGE exhibited new bands with lower positive charges. Western analysis demonstrated that nitration of tyrosine residues increased with the peroxynitrite concentration but the sites of nitration could not be determined. Instead MALDI-TOF analysis identified tryptophan-245 as a site of nitration. Such modification of tryptophan residues is responsible for the decrease in tryptophan fluorescence. These results demonstrate that peroxynitrite nitrates tyrosine and tryptophan residues of carbonic anhydrase II without causing fragmentation or dimerization. The peroxynitrite-induced inactivation of the enzyme is primarily due to the release of zinc ion in the enzyme's active site.

• Journal of Applied Biological Chemistry
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• v.54 no.3
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• pp.184-189
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• 2011

Polysaccharide (PS) was fractionated from hot-water extract of Artemisia iwayomogi Kitamura stems. PS showed considerably higher hydroxyl radical scavenging activity than caffeic acid and glutathione. PS showed lower superoxide anion radical scavenging activity than hydroquinone and ascorbic acid. The scavenging activity of PS on the reactive oxygen species (ROS) induced by human neutrophils with zymosan was determined by the lucigenin-enhanced chemiluminescence assay. The scavenging effect of the PS on ROS as determined by the chemiluminescence assay was about 2-fold stronger than that of ascorbic acid at the same concentration. PS significantly decreased protein carbonyl and malonaldehyde contents in UVB irradiated skin homogenates, which was comparable to glutathione at the same concentration. This result suggested that PS derived from A. iwayomogi Kitamura stems may be a potent candidate as functional compound for the protection on UVB induced skin damage in cosmetics.

• Journal of the Korean Society of Visualization
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• v.16 no.1
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• pp.61-69
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• 2018

Ion exchange membrane can transfer only cation or anion in electrically conductive fluids. Recent studies have revealed that such selective ion transport can initiate electroconvective instability, resulting vortical fluid motions on the membrane. This so-called electroconvective vortex (a.k.a. electroconvection (EC)) has been in the spotlight for enhancing an ion flux in electrochemical systems. However, EC under shear flow has not been investigated yet, although most related systems operate under pressure-driven flows. In this study, we present the direct visualization platform of EC under shear flow. On the transparent silicone rubber, microscale channels were fabricated between ion exchange membranes, while allowing microscopic visualization of fluid flow and ion concentration changes on the membranes. By using this platform, not only we visualize the existence of EC under shear flow, its unique characteristics are also identified: i) unidirectional vortex pattern, ii) its advection along the shear flow, and iii) shear-sheltering of EC vortices.

• Mycobiology
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• v.34 no.3
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• pp.124-127
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• 2006

This study was aimed at evaluating the antioxidant activities of methanol extract of Thamnolia vermicularis. The antioxidant activity, reducing power, superoxide anion radical scavenging and free radical scavenging activities were studied. The antioxidant activity of the extract correlated with its concentration ($0.2{\sim}2\;mg/ml$) in the reaction mixtures containing linoleic acid. Upto 67% of lipid peroxidation was inhibited by 2 mg/ml of the lichen extract. The extract showed strong free radical scavenging activity similar to that of BRA (positive control) in a manlier of concentration dependent. The lichen extract also showed moderate effects on superoxide anoin scavenging activity and reducing power, which was not so effective as that of Quercetin and BHA used as positive controls. This study suggests that T. vermicularis lichen can be used as a novel source of natural antioxidant.

• Journal of the Korean Ceramic Society
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• v.17 no.2
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• pp.75-79
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• 1980

The effect of the additive on the dielectric property of $TiO_2$ containing 0-2.5wt %. $Sb_2O_3$ was investigated as a function of frequency from $5{\times}10^4$ to $6.3{\times}10^7$ cps and temperature from 25 to 375$^{\circ}C$. The dielectric constant increased with increasing $Sb_2O_3$ concentration from 0.25 to 0.5wt.% It is due to space charge polarization caused by increasing anion vacanices. The dielectric constant decreased for further increase in $Sb_2O_3$ concentration. It can be explained by increasing grain size effect rather than space charge polarization.

• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1832-1838
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• 2006

The present paper is focused on sorption concentration of silver (I) on some complex-forming ion exchangers in the initial thiocyanate form and subsequent determination of Ag(I) in the phase of anion exchanger AN-25 by diffuse reflectance spectroscopy. The sorption and kinetic characteristics of the sorbents were investigated. The apparent stability constants of thiocyanate silver complexes in the ion exchanger phase were calculated. The sorption-spectroscopic method is proposed for Ag(I) determination in aqueous solutions. The calibration curve is linear in the concentration range of 10-200 mg/L (sample volume is 10.0 mL) and the detection limit is 2 $\mu$g/mL. The presence of $Na^+,\;K^+,\;Mg^{2+}$ (macrocomponents) as well as of Ni (II), Co (II), Cu (II) do not hinder the determination of silver (I).

• Journal of the Korean Electrochemical Society
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• v.2 no.4
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• pp.183-189
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• 1999

A study on the destruction of organic cation and anion exchange resins by electro-generated Ag(II) as a mediator was carried out to develop the ambient-temperature aqueous process, known as Ag(II)-mediated electro-chemical oxidation (MEO) process, for the treatment of a large quantity of spent organic ion exchange resins as the low and Intermediated-level radioactive wastes arising from the operation, maintenance and repairs of nuclear facilities. The effects of controllable process parameters such as applied current density, temperature, and nitric acid concentration on the MEO of organic ion exchange resins were investigated. The cation exchange resin was completely decomposed to $CO_2$. The current efficiency increased with a decrease in applied current density while nitric acid concentration and temperature on the MEO of cation exchange resin did not affect the MEO. On the other hand, anion exchange resins were decomposed to CO and $CO_2$. The ultimate conversion to CO was about $10\%$ regardless of temperature. The destruction efficiencies to $CO_2$ were dependent upon temperature and the effective destruction of anion exchange resin could be obtained above $60^{\circ}C$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.39 no.6
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• pp.783-788
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• 2010

The purpose of this study is to investigate the antioxidative activity and digestive enzyme inhibition of grape seed extract (GSE). The GSE was tested for its effect on various antioxidative potentials (scavenging activities of DPPH radical, superoxide anion radical and hydroxyl radical) and inhibitory effect of various digestive enzymes (trypsin, $\alpha$-chymotrypsin, $\alpha$-amylase, $\beta$-glucosidase and lipase). DPPH radical scavenging activity ($SC_{50}$, 50% scavenging concentration) of GSE was 4.76${\pm}$0.27 ppm while those of positive controls (EGCG and vitamin C) were 2.22${\pm}$0.12 ppm and 9.50${\pm}$0.72 ppm, respectively. $SC_{50}$ value of GSE against superoxide anion radical and hydroxyl radical were 3.82${\pm}$0.07 ppm and 803.23${\pm}$27.16 ppm, respectively. In addition, $IC_{50}$ values of GSE against trypsin, $\alpha$-chymotrypsin, $\alpha$-amylase, $\alpha$-glucosidase and lipase were 2.17${\pm}$0.59 ppm, 7.46${\pm}$1.25 ppm, 18.25${\pm}$3.54 ppm, 12.30${\pm}$1.12 ppm, and 653.23${\pm}$79.34 ppm, respectively. These results suggest that GSE may be useful for the prevention or treatment of obesity.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.33 no.3
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• pp.181-187
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• 2007

In this study, we measured the anti-oxidative activity of Cirsium setidens and investigated its effect on UVA-induced MMP-1 expression in human dermal fibroblats. And then we examined possible improvement in skin elasticity by topical treatment with fomular including Cirsium setidens extract. The ethanol extract of C. setidens showed free anion radical scavenging effect(87.47 % at 1 mg/mL) and superoxide anion radical scavenging effect(61.71 % at 1 mg/mL) in the xanthine/xanthine oxidase system, respectively. At the concentration of 100 ${\mu}g/mL$, C. setidens extract showed 95.54% inhibition on lipid peroxidation of linoleic acid. UVA-induced MMP-1 expression in human dermal fibroblasts was reduced to 54.69 % by treatment with 100 ${\mu}g/mL$ of C. setidens extract. A human clinical study, in which oil-in-water emulsion with C. setidens extract was topically applied, showed significant increase in skin elasticity. These results suggest that the C. setidens extract can be effective anti-aging ingredient for cosmetics applications.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.5
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• pp.419-430
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• 1987

The damage of plasmid DNA by lipid peroxidation and its inhibition were investigated through the model system of DNA and linoleic acid at $37^{\circ}C$. The degree of DNA damage increased in proportion to the increase of concentration and peroxidation of linoleic acid. DNA damage induced from linoleic acid peroxidation was greatly inhibited by the addition of active oxygen scavengers, especially, singlet of oxygen scavenge$(\alpha-tocopherol,\;cysteine)$ and superoxide anion scavenger(superoxide dismutase, ascorbic acid) in reaction system. These active oxygens, such as superoxide anion and hydrogen peroxide were rapidly generated in the early stage of peroxidation (POV below 100 mg/kg) and also scanvenged by the addition of superoxide dismutase and catalase, respectively. Hydroperoxide isolated from autoxidised linoleic acid showed DNA damage. Hydroperoxide induced-DNA damage was not inhibited by active oxygen scavengers. Lipid oxidation products, malonaldehyde and hexanal, also influenced on the DNA damage. Accordingly, it is speculated that DNA damage by lipid oxidation products is due to active oxygens such as singlet oxygen and superoxide anion formed in the early stage of peroxidation, direct action of hydroperoxide and formation of low molecular carbonyl compound-DNA complex. Furthermore, DNA damage induced by lipid peroxidation was remarkably inhibited by the addition of active oxygen scavengers and natural antioxidative fractions extracted from garlic and ginger. These antioxidative fractions also suppressed the generation of active orygens and linoleic acid oxidation. It is assumed that the inhibition of DNA damage by garlic and ginger extracts is due to the scavenging effect of active oxygens and the inhibition of hydroperoxide and oxidation products formation.