• Bulletin of the Korean Chemical Society
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• 제31권9호
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• pp.2479-2482
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• 2010

Using a pinhole-type glass nozzle equipped for a corona-excited supersonic expansion (CESE), precursor 2,6-dichlorotoluene seeded in a large amount of inert carrier gas helium was discharged to produce jet-cooled but electronically excited benzyl-type radicals. The visible vibronic emission spectrum was recorded with a long-path monochromator to observe vibronic bands in the $D_1{\rightarrow}D_0$ electronic transition of benzyl-type radicals. The spectral analysis revealed the generation of not only the 2,6-dichlorobenzyl radical as a typical product, but also the o-chlorobenzyl radical as an unexpected species, which indicates the possible molecular rearrangement in eliminating a chlorine atom from the benzene ring. A possible mechanism is proposed for the formation of the o-chlorobenzyl radical from the precurs or in the gas phase.

• 약학회지
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• 제45권1호
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• pp.101-107
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• 2001

Green tea catechins (GTC) and its major component, (-)-epigallocatechin gallate (EGCG) were studied for their protective effects against reactive oxygen species (ROS)-induced oxidative stress. GTC and EGCG skewed the strong antioxidative effects on the lipid peroxidation of ethyl linolate with Fenton's reagent and free radical scavenging effect to DPPH radical generation. They also protected $H_2O$$_2$- or KO$_2$-induced cytotoxicity in CHL cells or mouse splenocytes. These results indicate that GTC and EGCG are capable of protecting the lipid peroxidation, flee radical generation and cytotoxicity induced by ROS. The mechanism of inhibition in ROS-induced cytotoxicity may be due to their antiofidative and free radical scavenging properties. Therefore, GTC and EGCG may be useful chemopreventive agents by protecting the free radical generation which are involved in cancer and aging.

• Bulletin of the Korean Chemical Society
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• 제9권1호
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• pp.44-48
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• 1988

The feasibility of the reduction of nortricyclanone (1) as a chemical probe for testing the proposed radical mechanism for NAD-dependent horse liver alcohol dehydrogenase (HLADH) reactions has been examined using computer graphics modeling. The resutls of this study suggest that the radical ring-opening of this probe molecule may involve too substantial a geometry reorganization for the molecule to serve as a chemical probe in detecting the possible presence of the radical intermediates in the HLADH reactions. This result suggests that one should exercise caution in extrapolating results obtained from chemically based radical probes in the solution phase to the topologically constrained systems such as enzyme-substrate reactions.

• Korean Chemical Engineering Research
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• 제51권4호
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• pp.523-526
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• 2013

본 연구에서는 수질정화 기술개발을 위하여 수산화라디칼 및 오존 발생기를 이용하여 수중에 존재하는 천연 지방산 분해 제거 연구를 수행하였다. 천연 지방산은 수산화라디칼 및 오존에 의하여 1차 분해반응 형태로 제거되었으며, 천연 지방산의 분해반응에서 수산화라디칼 단독으로 사용하는 것 보다 오존과 함께 사용한 경우 분해 효율을 크게 향상시킬 수 있음을 알 수 있었다. 또한, 천연 지방산이 수산화라디칼과 오존에 의해 분해되는 화학반응 기구를 제안하였다.

• Environmental Analysis Health and Toxicology
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• 제8권3_4호
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• pp.33-41
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• 1993

This study was designed to determine the hemolytic mechanism of antitumor agent tetraphosphine platinum (II) complex (RC-1), which was synthesized recently. Erythrocytes treated with RC-1 showed concentration and time dependent lipid peroxydation, methemoglobin synthesis and hemolysis. And also treatment of radical scavengers showed the inhibitory effect of hemolysis and the decrease of malondialdehyde levels in RC-1 treated erythrocytes. So, the mechanism of hemolysis was considered to be the generation of free radicals, methemoglobin synthesis and the lipid peroxidation of phospholipid which composed of erythrocyte membrane.

• 약학회지
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• 제43권6호
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• pp.703-708
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• 1999

The effect of antioxidants on photochemical reaction of pefloxacin by UVB (290~320 nm) was investigated and the possible mechanism of phototoxicity on the skin was also studied. The photo-degradation of pefloxacin by UVB was suppressed by cysteine, reduced glutathione and ascorbic acid, but was promoted by ${\alpha}-tocopherol$. Squalene, accounts for more than 10% of skin surface lipids, was peroxidized by pefloxacin through both radical and singlet oxygen mechanism.

• Journal of Photoscience
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• 제8권2호
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• pp.67-69
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• 2001

Radical cations of DPBEY and PPCB were generated by ${\gamma}$-radiolysis and pulse radiolysis in halogenated solvents. The radical cation PPCB+ shows 505 (shoulder) and 520 nm absorption peaks with 700 ns lifetime in agreement with the laser flash photolysis work and strongly support the exciplex mechanism proposed for the photoreaction of PPCB and dimethylfumarate.

• 한국환경보건학회지
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• 제35권6호
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• pp.532-537
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• 2009

The tropospheric ozone production mechanism for the gas phase additive oxidation reaction of hydroxyl radical (OH) with isoprene (2-methyl-1,3-butadiene) has been studied using cavity ring-down spectroscopy (CRDS) at total pressure of 50 Torr and 298 K. The applicability of CRDS was confirmed by monitoring the shorter (~4%) ringdown time in the presence of hydroxyl radical than the ring-down time without the photolysis of hydrogen peroxide. The reaction rate constant, $(9.8{\pm}0.1){\times}10^{-11}molecule^{-1}cm^3s^{-1}$, for the addition of OH to isoprene is in good agreement with previous studies. In the presence of $O_2$ and NO, hydroxyl radical cycling has been monitored and the simulation using the recommended elementary reaction rate constants as the basis to OH cycling curve gives reasonable fit to the data.

• 한국연소학회지
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• 제4권1호
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• pp.27-38
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• 1999

We constructed a wire-cylinder type pulsed corona discharge system for $NO_x$ removal, which was operated in room temperature. A emission spectrometer was built with a boxcar averager and monochrometer equipped with photo-multiplier tube detector. The sensitivity of the emission spectrometer was greatly improved by synchronizing the emission spectrometer with pulsed corona discharge system using a triggered spark-gap switch. $N_2$ spectrum($c^3{\Pi}_u{\rightarrow}X^1{\Sigma}_g{^+}$) was measured in the range of 300 - 450 nm and oxidizing OH radical emission($A^2{\Sigma}^+{\rightarrow}X^2{\Pi}$) was measured in case $N_2$ was supplied with water bubbling. As wet gas composition of inlet $N_2$ supplied in the discharge system increased, the intensity of OH emission was increased and saturated at wet gas composition 50%. We also investigated additive effect of $C_2H_4,\;H_2O,\;H_2O_2$ on the intensity of OR emission and $NO/NO_2/NO_x$ reduction and analysed the related reaction mechanism in corona discharge process. $H_2O_2$ additive increased the intensity of OH emission and $NO/NO_x$ reduction.

• International Journal of Oral Biology
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• 제33권4호
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• pp.137-141
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• 2008

The present study reports the protective properties of a total methanol extract of B. platyphylla var. japonica against ultraviolet (UV)-C irradiation. Pretreatment of Chinese hamster fibroblast (V79-4) cells with a total methanol extract significantly increased cell survival following $300\;J/m^2$ of UV-C irradiation. The total methanol extract was further fractionated into 5 fractions: n-hexane, dichloromethane, ethylacetate, n-butanol and water fractions. Among these fractions, B. platyphylla var. japonica ethylacetate, butanol and water fractions showed significant protective effects against the cellular damage induced by UV-C irradiation. In order to elucidate the mechanism underlying this protective effect, DPPH (Editor note: abbreviations should be spelled out at first use.) radical scavenging and lipid peroxidation inhibitory activity were measured. Significant radical scavenging and lipid peroxidation inhibitory activities were observed for the ethylacetate fraction. In summary, the present data demonstrate that an extract of B. platyphylla var. japonica has a significant protective effect against UV-C irradiation. The underlying mechanism of this protective effect may involve radical scavenging and inhibition of lipid peroxidation by the B. platyphylla var. japonica extract.