• Asian Pacific Journal of Cancer Prevention
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• v.15 no.12
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• pp.4745-4751
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• 2014

Oxidative stress is caused by an imbalance in the redox status of the body. In such a state, increase of free radicals in the body can lead to tissue damage. One of the most important species of free radicals is reactive oxygen species (ROS) produced by various metabolic pathways, including aerobic metabolism in the mitochondrial respiratory chain. It plays a critical role in the initiation and progression of various types of cancers. ROS affects different signaling pathways, including growth factors and mitogenic pathways, and controls many cellular processes, including cell proliferation, and thus stimulates the uncontrolled growth of cells which encourages the development of tumors and begins the process of carcinogenesis. Increased oxidative stress caused by reactive species can reduce the body's antioxidant defense against angiogenesis and metastasis in cancer cells. These processes are main factors in the development of cancer. Bimolecular reactions cause free radicals in which create such compounds as malondialdehyde (MDA) and hydroxyguanosine. These substances can be used as indicators of cancer. In this review, free radicals as oxidizing agents, antioxidants as the immune system, and the role of oxidative stress in cancer, particularly breast cancer, have been investigated in the hope that better identification of the factors involved in the occurrence and spread of cancer will improve the identification of treatment goals.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2003.11a
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• pp.69-69
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• 2003

There are now increasing evidences that free radicals and reactive oxygen species are involved in a variety of pathological events. Reactive Oxygen Species (ROS) are produced during normal cellular function. ROS lead to lipid peroxidation, massive protein oxdiation and degradation. Under normal conditions, antioxidant are substnaces that either directly or indirectly protect cell against adverse effect of ROS. several biologically important compound include ${\beta}$-carotene, taruine and flavonoids reported have antioxidant function. The various antioxidant either scavange superoxide and free radicals or stimulate the detoxification mechanisms within cells resulting in increased detoxification of free radicals formation and thus in prevention of many pathophysiologic processes. This study carried out to investigate the antioxidant activity of flavonoids, myricetin with other antioxidants, ${\beta}$-carotene and taurine on B16Fl0. In order to investigate the efficacy of antioxidant activity, we measured cell viability, antioxidant enzyme activity (SOD, GPX, CAT) and intracellular reactive oxygen intermediate (ROI). In this results, we show that these flavonoids with other antioxidant substrates are increased antioxidant activity level.

• Journal of Microbiology
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• v.44 no.4
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• pp.466-471
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• 2006

In this study, we attempted to characterize the biomolecular effects of an atmospheric-pressure cold plasma (APCP) system which utilizes helium/oxygen $(He/O_2)$. APCP using $He/O_2$ generates a low level of UV while generating reactive oxygen radicals which probably serve as the primary factor in sterilization; these reactive oxygen radicals have the advantage of being capable to access the interiors of the structures of microbial cells. The damaging effects of plasma exposure on polypeptides, DNA, and enzyme proteins in the cell were assessed using biochemical methods.

• Journal of Life Science
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• v.6 no.1
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• pp.48-55
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• 1996

Oxygen free radicals are highly reactive molecules with unpaired electrons, which are produced with in aerobic cells in the course of normal metabolic events. Normally, aerobic cells are protected from the damage of free radicals by antioxidative enzymes such as superoxide dismutase (SOD), catalase, glutathione (GSH) peroxidase, GSH S-transferase and GSH reductase which scabvenge free radicals as well as nonenzymatic antioxidants such as ceruloplasmin, albumin and nontioxidants in order to elucidate antioxidative mechanisms of red ginseng. The treatment with total saponin of red ginseng significantly devreased the contents of malondialdehyde and total free radicals in the liver. On the other hand, total saponin of red ginseng significantly increased the activities of SOD, catalase and GSH reductase and nonprotein-SH level. These results suggest that total saponin of red ginseng exerts an antioxidative effect by increasing endogenous antioxidants.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.10 no.S_3
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• pp.127-137
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• 2001

The sonochemical Process has been applied as a treatment method and was investigated its effect on the decomposition of humic substances(HS). The reaction kinetics and mechanisms in the Process of sonochemical treatment for humic substances(HS) in wastewater have also been discussed. It was observed that the metal ions such as Fe(II) and Mn(II) showed catalytic effects, while Al(III), Ca(II), and Mg(II) had inhibitory effects on the decomposition of humic substances in sonochemical reaction with hydrogen peroxide. Experimental results also showed factors such as hydrogen peroxide dose affected the formation of disinfection by-products. Two trihalomethanes, chloroform and dichlorobromomethane were formed as major disinfection by-products during chlorination. The mechanism of radical reaction is controlled by an oxidation process. The radicals are so reactive that most of them are consumed by HS radicals and hydroxyl radicals can be acted on organic solutes by hydroxyl addition, hydrogen abstraction, and electron transfer. The depolymerization and the radical reaction of HS radicals appear to occur simultaneously. The final steps of the reaction are the conversion of organic acids to carbon dioxide.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.93-93
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• 2010

In this talk, I will introduce a reactive force field (ReaxFF) molecular dynamics (MD) simulation. In contrast to common MD simulations with empirical FFs, we can predict chemical reactions (bond breaking and formation) in large scale systems with the ReaxFF simulation where all of the ReaxFF parameters are from quantum mechanical calculations such as density functional theory to provide high accuracy. Accordingly, the ReaxFF simulation provides both accuracy of quantum mechanical calculations and description of large scale systems of atomistic simulations at the same time. Here, I will first discuss a theory in the ReaxFF including the differences from other empirical FFs, and then show several applications for studying chemical reactions of SiHx radicals on Si surfaces, which is an important issue in Si process.

• Korean Journal of Plant Resources
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• v.23 no.3
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• pp.207-213
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• 2010

Hovenia dulcis Thunb fruits were successively extracted with hot water, water, methanol, ethyl acetate, and chloroform. The crude extracts were investigated for potential antioxidant by measuring scavenging against DPPH free radicals, reducing power, superoxide radicals, and protection of protein damage and cultured cells from a lethal dose of hydrogen peroxide ($H_2O_2$). In all chemical assays used, the hot water extract of H. dulcis fruits, which contained $61.14{\pm}2.57$ (Tannic acid mg/g extract, n=3) of total phenolic compounds contents exhibited highest activity in in vitro models of DPPH free radical scavenging activity, reducing power assay, superoxide radical scavenging activity and protection of protein damage. In addition, the hot water extract protected cultured RAW 264.7 macrophages from a lethal dose of $H_2O_2$ and reduced reactive oxygen species level in RAW 264.7 cells.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.336-339
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• 1999

Photo-excited $TiO_2$ surface has a strong ability to induce various chemical reactions. Our study concentrates mainly on the utilisation of light energy to induce reactive radicals for environmental protection application. For instance, we have successfully used TiO$_2$ to break down foul smelling substances in air. In order to retain and separate the $TiO_2$ catalyst from the reactants and products, $TiO_2$ was immobilised by fixing onto various substrates. $TiO_2$ catalyst coated onto glass, wall paper and painted panel was found to show significant deodorising effect. The deodorising effect continues as long as$TiO_2$ is exposed to light irradiation.

• Applied Biological Chemistry
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• v.47 no.3
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• pp.293-299
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• 2004

Antioxidant activity of ethanolic extract of two giant embryonic rices, Nampung giant embryonic rice and Hwachung giant embryonic rice, were investigated mainly focusing on their ability to inhibit lipid peroxidation and scavenge reactive oxygen species in comparison with those of general rice. The results showed that germination process increased reducing power, inhibitory activity on lipid peroxidation and scavenging ability either on superoxide or hydroxyl radicals. Among the cultivars tested, increase in antioxidative action was found to be most prominent for Hwachung giant embryonic rice cultivar. For scavenging of superoxide radicals, the extract from Nampung giant embryonic rice has the most potent activity, however, increasing rate of scavenging activity by germination process was also found to be the greatest for Hwachung giant embryonic rice. We found that the scavenging mechanism for superoxide radicals was attributed to the direct scavenging of the radicals. The scavenging of hydroxyl radicals, the most toxic oxygen radical to biological system, by the rice extracts were also examined, and the results showed that either overall activity or the increasing rate of the activity to scavenge hydroxyl radicals by germination process was the greatest for Hwachung giant embryonic rice. Moreover, the results suggested that the scavenging action to hydroxyl radicals might be mediated by direct quenching of the radicals, not by chelating $Fe^{2+}$. Further studies showed that the antioxidant action of the rice extracts tested in vitro was also operative for suppressing ROS production induced in TPA-stimulated HL-60 cells.

• The Korean Journal of Pharmacology
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• v.21 no.1
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• pp.34-48
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• 1985

In vitro effects of nitrofurantoin, an antimicrobial agent for acute and chronic urinary tract infection, on the lung microsomal lipid peroxidation and the generation of reactive oxygen radicals were investigated to elucidate the biochemical mechanisms of its in vivopulmonary toxicity. The interaction of nitrofurantoin with porcine lung microsome resulted in significant lipid peroxidation. In addition, nitrofurantoin stimulated the generation of reactive oxygen radicals, $O^{-}_{2}{\cdot},\;H_2O_2$ as well as a highly reactive secondary oxygen species, $OH{\cdot}$. The stimulation of lipid peroxidation was inhibited not only by superoxide dismutase and catalase, but also by hydroxyl radical scavengers, mannitol and thiourea. Neither singlet oxygen $({^1}O_{2})$ was detected during the incubation of microsome with nitrofurantoin, nor lipid peroxidation was inhibited by singlet oxygen scavengers. When incubated anaerobically under the nitrogen atmosphere, the ability of nitrofurantoin to stimulatle lipid peroxidation was abolished. It appears that NADPH-dependent metaboliam of nitrofurantoin in pulmonary microsome under aerobic condition is accompanied by the stimulation of lipid peroxidation through the mediation of reactive oxygen radicals, particularly hydroxyl radical. It is strongly suggested from these results that the stimulation of pulmonary microsomal lipid peroxidation by the reactive oxygen radical may be a in vivo mechanism of pulmonary toxicity caused by nitrofurantoin.