• Bulletin of the Korean Chemical Society
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• v.12 no.2
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• pp.143-148
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• 1991

In the unhydrated and hydrated states, conformational free energies of L-ascorbic acid anion (AAA) were computed with an empirical potential function and the hydration shell model (a program CONBIO). The conformational energy was minimized from possible starting conformations expressed with five torsion angles of the molecule. The conformational entropy of each low energy conformation in both states was computed using a harmonic approximation. As found in L-ascorbic acid (AA), intramolecular hydrogen bonds (HBs) are proved to be of significant importance in stabilizing the overall conformations of AAA in both states, and give the folded conformations, which are quite different from those in crystal. There are competitions between HBs and hydration around O3 atom of the lactone ring and hydroxyls of the acyclic side chain. Especially, the whole conformation of AAA is strongly dependent on the water-accessibility of O3 atom. Though there is a significant effect of the hydration on conformational surface, the lowest energy conformation of the unhydrated AAA is conserved. The different patterns of HBs and hydration result in the conformations of AAA in both states being different from those of AA. It can be drawn by several feasible conformations obtained in the hydrated state that there exists an ensemble of several conformations in aqueous solution.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.10a
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• pp.145-146
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• 2005

• Bulletin of the Korean Chemical Society
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• v.20 no.9
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• pp.1017-1020
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• 1999

The aminolysis reactions of thiophenyl phenylacetates with benzylamines are investigated in acetonitrile at 55.0℃. Relatively large selectivity parameters, βx≒ 1.5, βz = -1.5~-1.8 and βxz = 0.92 together with the valid reactivity-selectivity principle are consistent with stepwise acyl transfer mechanism with rate limiting expulsion of the leaving group, thiophenolate anion, from the tetrahedral intermediate, T ± . The first order kinetics with respect to the benzylamine concentration and the realtively large secondary kinetic isotope effect (kH / kD = 1.2-1.7) involving deuterated benzylamine nucleophiles suggest a four center type transition state in which concurrent leaving group departure and proton transfer are involved.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1198-1202
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• 1998

Aminolysis of aryl thiol-2-furoates and thiol-2-thiophenates with benzylainines are investigated in acetonitrile at 50.0 ℃. Relatively large selectivity parameters, ρx(βx), ρz(βx) and ρxz (> 0) together with the valid reactivity-selectivity principle are consistent with a stepwise acyl transfer mechanism with rate-limiting expulsion of the leaving group, thiophenolate anion, from the tetrahedral intermediate, T±. The first-order kinetics with respect to the benzylamine concentration and the relatively large secondary kinetic isotope effect involving deuterated benzylamine nucleophiles suggest a four-center type transition state in which concurrent leaving group departure and proton transfer are involved.

• Bulletin of the Korean Chemical Society
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• v.10 no.2
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• pp.148-151
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• 1989

The hydrophobic interaction between tetraphenylborate (TPB$^-$) or tetrakis (4-fluorophenyl)borate (TFB$^-$) and crystal violet has been investigated in aqueous solutions by absorption spectrophotometry. Both of the anions promote the aggregation of the ion pairs formed between crystal violet and TPB$^-$ or TFB$^-$. When crystal violet and borate anion are nearly equimolar, insoluble floating aggregates can be observed. Based on the relative absorbance of H and J bands and on the effect of TX-100, TFB$^-$ is found to be more hydrophobic than TPB$^-$.

• 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.

• Journal of Korea Soil Environment Society
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• v.2 no.2
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• pp.25-33
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• 1997

To investigate the effects of cow manure compost(CMC) on soil and water environment as non-point source, the elution patterns of anions were determined in muti-layered soil columns which were consisted of one top and one bottom in combination. The top soil columns were uniformly packed with Ap horizon soils amended with air-dried CMC at different ratios(0, 2, 4, 6%, wt/wt), the bottom ones were packed with of B horizon soils of 15, 30, and 45cm in length. After saturating the each soil column, the leachate were collected from the bottom of the column while the double-ionized water was applied from the surface of the column by constant head method. From the hydraulic conductivity and anion eluted were measured in the leachate. Each saturated hydraulic conductivities for top and the bottom soils were 3$\times$$10^{-4}$sec and 1.6$\times$$10^{-3}$cm/sec. Most of water soluble chloride and sulfate, having non-specific adsorption characteristics onto the soil particles, were eluted within 1 PV, showing that there was no apparent retardation of anion movement with increasing CMC contents in the top soils. The effect of soil depths on anion movement were similar to the results of CMC contents. Sulfate of having both of non-specific and specific adsorption characteristics was also recovered in the effluent within 1 PV, while the elution curves were slightly skewed to the right showing that the CMC affected the movement of sulfate. Phosphate of specific adsorption characteristics was hardly eluted within 5 PV.

• Journal of Applied Biological Chemistry
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• v.54 no.3
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• pp.171-177
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• 2011

This study was carried out to search for natural anti-oxidants and anti-inflammatory compounds from 5 medicinal plants (Carthamus tinctorius seed, Cyperus rotundus, Schizonepeta tenuifolia, Polygonatum odoratum var. pluriflorum, and Paeonia lactiflora). These plants were extracted with 70% ethanol. In order to measure total antioxidant activity of flavonoids, polyphenol content was measured. Radical scavenging activities of extracts were examined using a-a-Diphenyl-${\beta}$-picrylhydrazyl ($DPPH{\cdot}$), 2,2-azino-bis 3-ethylbenzthiazoline-6-sulfonic acid ($ABTS{\cdot}$), ferric reducing antioxidant power (FRAP) and superoxide anion radical assays. C. tinctorius seed extracts showed the highest polyphenol and flavonoid contents as well as strong $DPPH{\cdot}$, $ABTS{\cdot}$, FRAP, and superoxide anion radical scavenging activity. Also, C. tinctorius seed extracts showed the highest nitric oxide (NO) production inhibitory effect. Theses results indicate that the C. tinctorius seed extracts can be used as a functional material due to their effective anti-oxidative and antiinflammatory activities.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.4
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• pp.462-469
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• 2009

This study was conducted to investigate total polyphenolic contents and reactive oxygen species (ROS) scavenging effects of extracts from peels of ten Jeju native citrus fruits according to the harvest from August 2006 to February 2007. Total polyphenolic contents from methanol extracts of citrus peel were the highest in Jigak (Citrus aurantium) and Hongkyool (C. tachibana) by over 200 mg% in the unmatured period, from the late August to the late September, and all the citrus peels mostly decreased while ripening. Scavenging effect of superoxide anion radical showed good correlation with total polyphenolic contents. The unmatured periods of Hongkyool and Jigak were the highest with more than 60%. Hydrogen peroxide scavenging activity was the highest in Sadoogam (C. pseudogulgul) at 73.8% in late August and the second highest activity was observed in Jigak at near 70%, and all the citrus peels decreased during ripening. Hydroxy radical scavenging activity were the highest among all the ROS scavenging activities, especially in the Jigak and Dangyooja (C. grandis) at 75.1% and 74.6%, respectively, and not much affected by increased maturity of the fruits. Nitric oxide radical scavenging activity was the highest in Bungkyool (C. platymama) at 58.4% in late February, and increased with fruit ripening. In this study, Jigak was generally the highest in the polyphenolic contents and ROS scavenging activities, so the further studies are needed for industrial applications.

• Korean Journal of Environmental Agriculture
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• v.7 no.2
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• pp.96-101
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• 1988

It is important to assess the effects of ionic strength and type of anions when studying the adsorption of heavy metals on zeolite because the background salt may complex with heavy metals and compete for adsorption sites. This experiment was carried out to determine the effect of ionic strength and anion species($Cl^-$, $SO^{2-}\;_4$, and $ClO^-\;_4$) on heavy metal adsorption. Heavy metal adsorption by zeolite from solutions in the range of 10 to 50ppm was studied in the presence of NaCl, $Na_2SO_4$ and $NaClO_4$, with different concentrations. The ionic strength ranged from 0.01 to 1.00. Adsorption of heavy metal cations could be described by the Freundlich isotherm equation. Increasing the ionic strength of equilibrium solutions, the amounts of heavy metal adsorbed on the zeolite surfaces decreased in all three of the anion systems. This fact could be attributed to the competition of background salt cation and the decrease in initial activity of heavy metal cations. In the presence of Cl anion, less adsorption resulted than in the presence of $SO_4$ or $ClO_4$ anions of the same ionic strength, indicating the presence of uncharged and negatively charged complexes of heavy metal with Cl ligands.