• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.240.1-240.1
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• 2012

We performed simultaneous observations of SiO v=1, 2, $^{29}SiO$ v=0, J=1-0 and $H_2O$ $6_{16}-5_{23}$ maser lines toward 252 OH/IR stars using the Korean VLBI Network 21m telescopes. The observations were carried out from 2011 November to 2012 July for studying SiO and $H_2O$ maser properties associated with the evolutionary stages of OH/IR stars. Both $H_2O$ and SiO masers were detected from 49 sources, one-side maser of SiO and $H_2O$ was detected from 109 and 11 sources, respectively. Mutual relations between SiO and $H_2O$ maser properties are investigated based on statistical analyses. We also investigate these maser properties in the IRAS two-color diagram related with stellar evolutionary sequence.

• Applied Chemistry for Engineering
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• v.21 no.4
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• pp.391-395
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• 2010

This study presents the effect of CO in flue gas on the $H_2$ SCR by Pt/$TiO_2$ catalyst. Coexisting CO which has characteristics of competitive adsorption with $H_2$ as a reductant on the active sites showed the decrease of catalytic activity. Competitive adsorption with NO, CO and $H_2$ also caused the reduction of activity and $H_2$, CO slip simultaneously. With increasing the inlet CO concentration, such phenomenon became more pronounced. Adding $PdO_2$ and $CeO_2$ on the catalyst to avoid the inhibition by coexisting CO, $CeO_2$ added catalyst exhibited the durability against CO which fed 100 ppm under.

• BMB Reports
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• v.39 no.4
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• pp.452-456
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• 2006

To elaborate the peroxidase activity of cytochrome c in the generation of free radicals from $H_2O_2$, the mechanism of DNA cleavage mediated by the cytochrome c/$H_2O_2$ system was investigated. When plasmid DNA was incubated with cytochrome c and $H_2O_2$, the cleavage of DNA was proportional to the cytochrome c and $H_2O_2$ concentrations. Radical scavengers, such as azide, mannitol, and ethanol, significantly inhibited the cytochrome c/$H_2O_2$ system-mediated DNA cleavage. These results indicated that free radicals might participate in the DNA cleavage by the cytochrome c and $H_2O_2$ system. Incubation of cytochrome c with $H_2O_2$ resulted in a time-dependent release of iron ions from the cytochrome c molecule. During the incubation of deoxyribose with cytochrome c and $H_2O_2$, the damage to deoxyribose increased in a time-dependent manner, suggesting that the released iron ions may participate in a Fenton-like reaction to produce $\cdot$OH radicals that may cause the DNA cleavage. Evidence that the iron-specific chelator, desferoxamine (DFX), prevented the DNA cleavage induced by the cytochrome c/$H_2O_2$ system supports this mechanism. Thus we suggest that DNA cleavage is mediated via the generation of $\cdot$OH by a combination of the peroxidase reaction of cytochrome c and the Fenton-like reaction of free iron ions released from oxidatively damaged cytochrome c in the cytochrome c/$H_2O_2$ system.

• The Journal of Korean Medicine
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• v.21 no.4
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• pp.193-203
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• 2000

Objectives : Hindered barrier function of vascular endothelium has been implicated in the initiation and progression of degenerative vascular diseases such as atherosclerosis. In this study, the effect of Sunghyangchungisan(SHCS) as a protectant against oxidant-induced destruction of endothelial barrier function was assessed. Methods : Toward this end, endothelial cells derived from the human umbilical vein were cultured as monolayers on permeable membrane filters. Endothelial permeability was monitored by measuring transendothelial electrical resistance and movement of low density lipoprotein (LDL) across the endothelial monolayer. Results : Along with increased movement of LDL, $H_2O_2$-induced increase in endothelial permeability was paralleled by a decrease in transendotheliaI electrical resistance. The effect of $H_2O_2$ was mimicked by phorbol 12-myristate 13-acetate (PMA), a potent activator of proteinkinase C. Calphostin-C, a protein kinase C inhibitor, effectively blocked the increase in endothelial permeability induced by $H_2O_2$ or PMA, indicating that activation of protein kinase C is associated with the $H_2O_2-induced$ permeability change. SHCS effectively protected the endothelial monolayer against $H_2O_2-induced$ increase in permeability, whereas, it did not affect PMA-induced change. Forskolin, a potent activator of adenylyl cyclase, antagonized $H_2O_2$ to increase endothelial permeability. In addition, in ${H_2O_2}-treated$ cens, intracenular cAMP concentration was significantly decreased, indicating that impaired cAMP production as well as activation of proteinkinase C is a mechanism underlying ${H_2O_2}>-induced$$H_2O_2$ with regard to its effect on intracellular cAMP content. However, SHCS itself did not affect resting cAMP concentration in endothelial cells. Conclusions : These results suggest that SHCS might operate as an effective protectant against oxidant-induced destruction of endothelial barrier function. The mechanism does not appear to involve direct interaction with protein kinase C- or cAMP-associated signaling mechanism.

• Molecules and Cells
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• v.39 no.1
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• pp.65-71
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• 2016

A challenge in the redox field is the elucidation of the molecular mechanisms, by which $H_2O_2$ mediates signal transduction in cells. This is relevant since redox pathways are disturbed in some pathologies. The transcription factor OxyR is the $H_2O_2$ sensor in bacteria, whereas Cys-based peroxidases are involved in the perception of this oxidant in eukaryotic cells. Three possible mechanisms may be involved in $H_2O_2$ signaling that are not mutually exclusive. In the simplest pathway, $H_2O_2$ signals through direct oxidation of the signaling protein, such as a phosphatase or a transcription factor. Although signaling proteins are frequently observed in the oxidized state in biological systems, in most cases their direct oxidation by $H_2O_2$ is too slow ($10^1M^{-1}s^{-1}$ range) to outcompete Cys-based peroxidases and glutathione. In some particular cellular compartments (such as vicinity of NADPH oxidases), it is possible that a signaling protein faces extremely high $H_2O_2$ concentrations, making the direct oxidation feasible. Alternatively, high $H_2O_2$ levels can hyperoxidize peroxiredoxins leading to local building up of $H_2O_2$ that then could oxidize a signaling protein (floodgate hypothesis). In a second model, $H_2O_2$ oxidizes Cys-based peroxidases that then through thiol-disulfide reshuffling would transmit the oxidized equivalents to the signaling protein. The third model of signaling is centered on the reducing substrate of Cys-based peroxidases that in most cases is thioredoxin. Is this model, peroxiredoxins would signal by modulating the thioredoxin redox status. More kinetic data is required to allow the identification of the complex network of thiol switches.

• Korean Journal of Pharmacognosy
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• v.27 no.4
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• pp.328-335
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• 1996

Effects of hydrogen peroxide$(H_2O_2)$ on polyphenol oxidase (PPO) in Perillae Folium were investigated. The inactivation of this enzyme was dependent on $H_2O_2$ concentration. and the initial lag period was not shown. Preincubation of Perillae Folium PPO with $H_2O_2$ in the absence of a substrate resulted in rapid loss of enzymatic activity. The inactivation of PPO by $H_2O_2$ dependents temperature and pH. OH radical scavengers such as mannitol and sodium formate did not protect the enzyme against inactivation by $H_2O_2$. Substrate analogue such as phenylalanine protected the enzyme against inactivation by $H_2O_2$. and copper chelator such as sodium azide also protected the enzyme.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.585-590
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• 1998

Fibrous $Na_xTi_nO_{2n+1}$ whisker was prepared by $H^+/Na^+$ ion-exchange on layered hydrous titanium dioxide ($H_2Ti_4O_9{\cdot}nH_2O$). The ion-exchange reaction was proceeded at 0.5~2.0 M NaOH solution. In the ion-exchange at 2.0 M NaOH solution, 73% of sodium was exchanged and the prepared $Na_xTi_nO_{2n+1}$ whisker was a fibrous crystal of about $10{\sim}20{\mu}m$ of length and about $0.7{\mu}m$ of diameter. The phase transition of the ion-exchange phases identified by the thermal analysis. The result showed that the $Na_xTi_nO_{2n+1}$ whisker was decomposed into $Na_2Ti_6O_{13}$ and $TiO_2$ in the temperature of $200{\sim}600^{\circ}C$.

• The Korean Journal of Physiology
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• v.20 no.1
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• pp.53-63
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• 1986

Carbon monoxide(CO) poisoning has been one of the major environmental problems because of the tissue hypoxia, especially brain tissue hypoxia, due to the great affinity of CO with hemoglobin. Inhalation of the pure oxygen$(0_2)$ under the high atmospheric pressure has been considered as the best treatment of CO poisoning by the supply of $0_2$ to hypoxic tissues with dissolved from in plasma and also by the rapid elimination of CO from the carboxyhemoglobin(HbCO). Hydrogen peroxide $(H_2O_2)$ was rapidly decomposed to water and $0_2$ under the presence of catalase in the blood, but the intravenous administration of $H_2O_2$ is hazardous because of the formation of methemoglobin and air embolism. However, it was reported that the enema of $H_2O_2$ solution below 0.75% could be continuously supplied $0_2$ to hypoxic tissues without the hazards mentioned above. This study was performed to evaluate the effect of $H_2O_2$ enema on the elimination of CO from the HbCO in the recovery of the acute CO poisoning. Rabbits weighting about 2.0 kg were exposed to If CO gas mixture with room air for 30 minutes. After the acute CO poisoning, 30 rabbits were divided into three groups relating to the recovery period. The first group T·as exposed to the room air and the second group w·as inhalated with 100% $0_2$ under 1 atmospheric pressure. The third group was administered 10 ml of 0.5H $H_2O_2$ solution per kg weight by enema immediately after CO poisoning and exposed to the room air during the recovery period. The arterial blood was sampled before and after CO poisoning ana in 15, 30, 60 and 90 minutes of the recovery period. The blood pH, $Pco_2\;and\;Po_2$ were measured anaerobically with a Blood Gas Analyzer and the saturation percentage of HbCO was measured by the Spectrophotometric method. The effect of $H_2O_2$ enema on the recovery from the acute CO poisoning was observed and compared with the room air group and the 100% $0_2$ inhalation group. The results obtained from the experiment are as follows: The pH of arterial blood was significantly decreased after CO poisoning and until the first 15 minutes of the recovery period in all groups. Thereafter, it was slowly increased to the level of the before CO poisoning, but the recovery of pH of the $H_2O_2$ enema group was more delayed than that of the other groups during the recovery period. $Paco_2$ was significantly decreased after CO poisoning in all groups. Boring the recovery Period, $Paco_2$ of the room air group was completely recovered to the level of the before CO Poisoning, but that of the 100% $O_2$ inhalation group and the $H_2O_2$ enema group was not recovered until the 90 minutes of the recovery period. $Paco_2$ was slightly decreased after CO poisoning. During the recovery Period, it was markedly increased in the first 15 minutes and maintained the level above that before CO Poisoning in all groups. Furthermore $Paco_2$ of the $H_2O_2$ enema group was 102 to 107 mmHg and it was about 10 mmHg higher than that of the room air group during the recovery period. The saturation percentage of HbCO was increased up to the range of 54 to 72 percents after CO poisoning and in general it was generally diminished during the recovery period. However in the $H_2O_2$ enema group the diminution of the saturation percentage of HbCO was generally faster than that of the 100% $O_2$ inhalation group and the room air group, and its diminution in the 100% $O_2$ inhalation group was also slightly faster than that of the room air group at the relatively later time of the recovery period. In conclusion, the enema of 0.5% $H_2O_2$ solution is seems to facilitate the elimination of CO from the HbCO in the blood and increase $Paco_2$ simultaneously during the recovery period of the acute CO poisoning.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.107-111
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• 2002

The OSS2 (Oj？me-Shavitt-Singer 2)[L. Oj？me et al., J. Chem. Phys. 109, 5547 (1998)] model for the solvated proton in water is examined for $H_2O,\;H_3O^+,\;H_5O_2^+,\;H_7O_3^+,\;and\;H_9O_4^-$ by molecular dynamics (MD) simulations. The equilibrium molecular geometries and energies obtained from MD simulations at 5.0 and 298.15 K agree very well with the optimized calculations.

• Journal of Periodontal and Implant Science
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• v.37 no.4
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• pp.655-669
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• 2007

Reactive oxygen species (ROS) have been implicated in the pathogenesis of various diseases. And vitamin C has shown a protective effect for the tissues. The aim of this study was to evaluate the effects of $H_2O_2$ and ascorbic acid on matrix metalloproteinase-1 (MMP-1), tissue inhibitor of metalloproteinase (TIMP: TIMP-1, TIMP-2), Type 1 collagen, fibronectin, and PDLs22 level in human periodontal ligament fibroblasts (hPDLF) via reverse transcription-polymerase chain reaction (RT-PCR). hPDLF was obtained from a healthy periodontium and cultured in Dulbecco's modified Eagles's medium plus 10% fetal bone serum. The concentration of ascorbic acid in hPDLF was $50{\mu}g/ml$, and that of $H_2O_2$ in hPDLF was 0.03% and 0.00003%. Ascorbic acid only, $H_2O_2$ only and mixture of ascorbic acid and $H_2O_2$ were applied with hPDLF for 1-, 3-, and 30-min. respectively. The gene expression of MMP-1-, TIMP-1-, TIMP-2-, Type 1 collagen-, fibronectin-, and PDLs22-mRNA in hPDLF was analysed via RT-PCR. The results were as follows; 1. hPDLF in response to 30-min. incubation with 0.03% $H_2O_2$ did not show any gene expression. 2. In all the experimental groups, the gene expression of fibronectin mRNA showed the decreased tendency compared to control. 3. In all the experimental groups, the gene expression of TIMP-1 mRNA showed the tendency similar to control. 4. hPDLF in response to 30-min. incubation with 0.03% $H_2O_2$ and ascorbic acid increased mRNA induction for MMP-1. 5. In all the experimental groups, hPDLF increased mRNA induction for PDLs22, collagen type 1, and TIMP-2 compared to control. Within the limited experiments, $H_2O_2$ and ascorbic acid increased mRNA induction for PDLs22, collagen type 1, TIMP-2 in hPDLF. More research will be needed in order to confirm the relative importance of the different roles of ROS and antioxidants in hPDLF from a periodontal regeneration or repair standpoint.