• Mass Spectrometry Letters
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• 제12권4호
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• pp.146-151
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• 2021

In this study, the hydrogen/deuterium (HDX) exchange mechanism of active hydrogen, nitrogen, and sulfur-containing polycyclic aromatic hydrocarbon (PAH) dissolved in toluene and deuterated methanol by atmospheric pressure photoionization (APPI) is investigated. The comparison of the data obtained using APPI suggests that aniline and benzene-1,2-dithiol contain two exchanging hydrogens. The APPI HDX that best explains the experimental findings was investigated with the use of quantum mechanical calculations. The HDX mechanism is composed of a two-step reaction: in the first step, analyte radical ion gets deuterated, and in the second step, the hydrogen transfer occurs from deuterated analyte to de-deuterated methanol to complete the exchange reaction. The suggested mechanism provides fundamentals for the HDX technique that is important for structural identification with mass spectrometry. This paper is dedicated to Professor Seung Koo Shin for his outstanding contributions in chemistry and mass spectrometry.

• 한국환경과학회지
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• 제21권7호
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• pp.845-853
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• 2012

Diethyl phthalate (DEP) is widely spread in the natural environment as an endocrine disruption chemicals (EDs). Therefore, in this study, ultrasound (US) and ultraviolet (UVC), including various applied power density (10-40 W/L), UV wavelengths (365 nm, 254 nm and 185 nm) and frequencies (283 kHz, 935 kHz) were applied to a DEP contaminated solution. The pseudo-first order degradation rate constants were in the order of $10^{-1}$ to $10^{-4}\;min^{-1}$ depending on the processes. Photolytic and sonophotolytic DEP degradation rate also were high at shortest UV wavelength (VUV) due to the higher energy of photons, higher molar absorption coefficient of DEP and increased hydroxyl radical generation from homolysis of water. Sonolytic DEP degradation rate increased with increase of applied input power and the dominant reaction mechanism of DEP in sonolysis was estimated as hydroxyl radical reaction by the addition of t-BuOH, which is a common hydroxyl radical scavenger. Moreover, synergistic effect of were also observed for sonophotolytic degradation with various UV irradiation.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.267-270
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• 2002

Photodissociations of o-, m-, and p-iodotoluene radical cations were investigated by using Fourier-transform ion cyclotron resonance (FT-ICR) spectrometry. Iodotoluene radical cations were prepared in an ICR cell by a photoionization charge-transfer method. The time-resolved one-photon dissociation spectra were obtained at 532 nm and the identities of $C_7H_7^+$ products were determined by examining their bimolecular reactivities toward toluene-$d_8$. The two-photon dissociation spectra were also recorded in the wavelength range 615-670 nm. The laser power dependence, the temporal variation, and the identities of $C_7H_7^+$ were examined at 640 nm. The mechanism of unimolecular dissociation of iodotoluene radical cations is elucidated: the lowest barrier rearrangement channel leads exclusively to the formation of the benzyl cation, whereas the direct C-I cleavage channel yields the tolyl cations that rearrange to both benzyl and tropylium cations with dissimilar branching ratios among o-, m-, and p-isomers. With a two-photon energy of 3.87 eV at 640 nm, the direct C-I cleavage channel results in the product branching ratio, [tropylium cation]/[benzyl cation], in descending order, 0.16 for meta >0.09 for ortho >0.05 for para.

• Advances in Traditional Medicine
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• 제4권3호
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• pp.179-185
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• 2004

The ethanol extract of Indigofera cordifolia was studied for in vivo gastroprotective activity, cytotoxic activity against oral tumor and normal cells, multidrug resistance (MDR) reversal activity, anti-human immunodeficiency virus (HIV) activity and radical scavenging activity. The extract of I. cordifolia showed potent gastric mucosal protective activity against stomach injury induced by HCl/EtOH solution. However, the gastroprotective activity could not be related to the radical mechanism, because the extract weakly scavenged both OH radical and $O_2*^-$. The extract also showed promising levels of MDR-reversing activity. This study demonstrates the tumor-specific cytotoxic action of the plant extract. However, the extract had no anti-HIV activity. From above results, the study suggests the medicinal importance of I. cordiforia extract.

• 한국수소및신에너지학회논문집
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• 제18권2호
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• pp.157-163
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• 2007

During PEMFC operation, low current and low humidity conditions accelerate the degradation of perfluorosulfonic acid membrane. But, there have been no studies that clearly explain why these conditions accelerate the membrane degradation. In this study, the hydrogen permeability through the membrane, I-V polarization of MEA, fluoride emission rate(FER) in effluent water were measured during cell operation under low current densities and low relative humidity(RH). The experimental results were evaluated with oxygen radical mechanism the most commonly known for membrane degradation. It seems that low RH of anode is a good condition for $H{\cdot}$ radical formation on the Pt catalyst and the low current condition accelerates the $H{\cdot}$ to form $HO_2{\cdot}$ radical attacking the polymer membrane.

• 대한화학회지
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• 제15권1호
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• pp.37-44
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• 1971

The reaction of amino acids and the reactive hydroxyl radical generated by $Ti^{3+}-H_2O_2$ system was studied using fast flow techniques coupled with ESR. Upon adding methionine to the 0.2M $H_2O_2$ solution (0.05M methionine after addition) and mixing with 0.01M $TiCl_3$, the low field component of the two incompletely resolved peaks, in the spectrum of $Ti^{3+}-H_2O_2$ system alone, vanished completely whereas the high field component remained almost constant and superimposed on the secondary spectrum of the methionine free radical. Similar results were obtained for other amino acids and proteins. The results strongly demonstrate that the $T^{3+}-H_2O_2$ flow system generates two different radical species, only one of which, giving rise to the low field component, is alone responsible for abstracting hydrogen atoms from substrate molecules. The effects of HCl, $H_2SO_4$ and NaOH on the system were also studied with widely varying results.

• Clinical and Experimental Pediatrics
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• 제48권9호
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• pp.920-923
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• 2005

Epilepsy is a neurological disorder from many molecular and biochemical responses. In the underlying mechanism, free radicals play an important role in seizure initiation and seizure-induced brain damage. Excessive production of oxygen free radicals and other radical species have been implicated in the development of seizures under pathological conditions and linked to seizure-induced neurodegeneration.

• International Journal of Automotive Technology
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• 제6권6호
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• pp.555-561
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• 2005

This experimental study was executed to obtain basic data for actual engine operation using radical induced ignition method (RI) which can achieve emission reduction and high efficiency due to the rapid bulk combustion. In this study, a direct injection diesel engine was converted into SI type engine with a sparkplug. The modified SI type engine can be divided into two classes. One is the SI engine with a sparkplug only at the cylinder head, and the other is the SI engine with the sparkplug which is enveloped in a sub-chamber. Also, a basic experimental was conducted in order to investigate combustion mechanism of radical induced injection before the experiment execution for actual engine using the modified SI engine. The bulk combustion phenomenon of radical induced ignition method was analyzed from the basic experiment by using a constant volume chamber. Volume value of sub-chamber used in this experiment is approximately $0.2\%$ of one of the main combustion chamber. In this paper, combustion characteristics using radical induced injection method was compared with that of using spark ignition method according to change in the engine speed and equivalence ratio. As a result, in the case of the radical induced injection engine, the combustion duration and cycle variation were respectively reduced ranged from $\Phi$(equivalence ratio)=0.8 (lean mixture ratio) to $\Phi$=1.0 (stoichiometric ratio).

• Toxicological Research
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• 제11권2호
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• pp.205-213
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• 1995

This study was undertaken to investigate the effects of organic solvents on xenobiotic metabollzing enzyme system in vivo by meaas of experimental conditions i.e. (1) single group which was treated by benzene (B), toluene (T) and xylene (X), respectively, (2) combination group which was treated by mixture of benzene+toluene (BT), benzene+xylene (BX), and toluene+xylene (TX), respectively, (3) mixture group which was treated by benzene+ toluene+xylene mixture (M), and to interpreat the interaction between the organic solvents metabolizing enzymes. 1. The contents of cytochrome P-450 in liver microsomes were increased (p < 0.01) in organic solvents treated groups, and the contents of cytochrome P-450 were increased by following order of B < T < M < BT=BX < X < TX. 2. The activity of cytochrome P-450 dependent AHHase was significantly higher in organic solvents treated groups than in control group (p < 0.01), and the activity of AHHase was increased by following order of B < T < BT=BX=TX=xylene < M. 3. The activity of NADPH P-450 reductase was significantly higher in organic solvents treated groups than in control group (p < 0.01), and the order of M < combinated group < X < T

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2019년도 추계학술대회
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• pp.88-88
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• 2019

Antioxidants are involved in the defense mechanism against the attack of free radicals. This study was carried out to determine the antioxidant activity of new variety of Glycyrrhiza cultivar radix, Wongam and Sinwongam. Dissolved freeze dried Wongam and Sinwongam extracts were filtered by $0.2{\mu}m$ filter and serially diluted at the concentrations of $10{\mu}g/mL$, $50{\mu}g/mL$, $100{\mu}g/mL$, $500{\mu}g/mL$, and $1000{\mu}g/mL$. The antioxidant potential was determined by DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity, ABTS (2,2-azino-bis (3-rthylbenzthiazoline-6-sulfonic acid) diammonium salt) radical cation decolorization assay, nitrite radical scavenging assay, and ferric reducing antioxidant power (FRAP) assay. DPPH radical scavenging activities (i.e. the highest value $50.9{\pm}0.8%$ by Wongam and $82.6{\pm}1.1%$ by Sinwongam), ABTS radical scavenging activities (i.e. the highest value $88.1{\pm}1.8%$ by Wongam and $98.6{\pm}0.1%$ by Sinwongam), and nitrite radical scavenging activities (i.e. the highest value $87.3{\pm}1.6%$ by Wongam and $89.8{\pm}0.8%$ by Sinwongam) increased in a dose-dependent manner. In addition, ferric reducing power activities also increased in a dose-dependent manner. The FRAP value of Wongam and Sinwongam extracts were $0.72{\pm}0.03$ and $0.99{\pm}0.06$ compared to ascorbic acid, as a positive control, was $1.32{\pm}0.02$. These results suggested that Wongam and Sinwongam have beneficial effects as a potent antioxidant.