• Bulletin of the Korean Chemical Society
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• 제31권6호
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• pp.1573-1576
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• 2010

Bacillus subtilis PerR is a metal-dependent peroxide-sensing transcription factor which uses metal-catalyzed histidine oxidation for peroxide-sensing. PerR contains two metal binding sites, one for structural $Zn^{2+}$ and the other for the regulatory/peroxide-sensing metal. Here we investigated the effect of mutations at both the structural and regulatory metal binding sites on the oxidation of either H37 or H91, two of the peroxide-sensing ligands. All four serine substitution mutants at the structural $Zn^{2+}$ site (C96S, C99S, C136S and C139S) exhibited no detectable oxidation at histidine residues. Two of the alanine substitution mutants at regulatory metal site (H37A and D85A) exhibited selective oxidation preferentially at the H91-containing tryptic peptide, whereas no oxidation was detected in the other mutants (H91A, H93A and D104A). Our results suggest that the cysteine residues coordinating structural $Zn^{2+}$ are essential for peroxide sensing by PerR, and that the C-terminal regulatory metal binding site composed of H91, H93 and D104 can bind $Fe^{2+}$, providing a possible explanation for the peroxide sensing mechanisms by PerR.

• Journal of Ecology and Environment
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• 제41권9호
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• pp.235-245
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• 2017

Background: Loading of excess nutrient via bioremediation of polluted sediment to overlying water could trigger anoxia and eutrophication in coastal area. The aim of this research was to understand the changes of overlying water features such as dissolved oxygen (DO); pH; oxidation reduction potential (ORP); $chlorophyll-{\alpha}$ ($Chl-{\alpha}$); and nitrogen nutrients ammonia ($N-NH_4{^+}$), nitrate ($N-NO_3{^-}$), and nitrite ($N-NO_2^-$) when the sediment was not treated (control) and treated by calcium peroxide for 5 weeks. Methods: The water samples were analyzed for measuring physical and chemical properties along with the sediment analyzed by polymerase chain reaction (PCR) including denaturing gradient gel electrophoresis (DGGE) for identifying the phylogenetic affiliation of microbial communities. Results: Results showed that due to the addition of calcium peroxide in sediment, the overlying water exposed the rise of dissolve oxygen, pH, and ORP than control. Among the nitrogen nutrients, ammonia inhibition was higher in calcium peroxide treatment than control but in case of nitrate inhibition, it was reversed than control. $Chlorophyll-{\alpha}$ was declined in treatment column water by 30% where it was 20% in control column water. Actibacter and Salegentibacter group were detectable in the calcium-peroxide-treated sediment; in contrary, no detectable community ware found in control sediment. Both phylogenetic groups are closely related to marine microflora. Conclusions: This study emphasizes the importance of calcium peroxide as an oxygen release material. Interaction with peroxide proved to be enhancing the formation of microbial community that are beneficial for biodegradation and spontaneity of nutrient attenuation into overlying water.

• Restorative Dentistry and Endodontics
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• 제19권1호
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• pp.114-123
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• 1994

The purpose of this study was to examine the shear bond strength of resin-enamel bond formed at specific time intervals after the termination ov vital bleaching. A total of 72 human extracted maxillary premolars were divided into nine groups : untreated control (group 1) ; enamel treated with 35% hydrogen peroxide(group 2, 3, 4, 5) ; and enamel reated with 15% carbamide peroxide gel (group 6, 7, 8, 9). After the treatment with 35% hydrogen peroxide for 2 hours and 15% carbamide peroxide for 24 hours, adhesion of a resin to bleached enamel was formed at 1 hour (group 2, 6) and 24 hours(group 3, 7) ; 3days(group 4, 8) and 7 days(group 5, 9) post-termination of bleaching treatment. A $3{\times}3mm$ mold was filled with Scotchbond Multi-Purpose and Z100. After 24 hours later, the specimens were shear-tested at crosshead speed 1mm/min and analyzed statistically. Fractured specimens from group 1,2, 6 were gold-coated with Eiko ion coater and observed under Scanning electron microscope at 25KV. The following results results were obtained : 1. Bonds formed at 1 hour post-termination of 35 % hydrogen peroxide(P<0.01) and 15 % carbamide peroxide bleaching treatment groups(P<0.05) showed significantly lower shear bond strength than untreated group. 2. Bonds formed at 24 hours, 3 days and 7 days post-termination of 35% hydrogen peroxide and 15 % carbamide peroxide bleaching treatment groups showed no significant differences in shear bond strength with untreated group(p>0.05). 3. SEM examinations of the untreated fracture specimen indicated cohesive fracture within enamel and exposed enamel prisms, but the bleached fracture specimens indicated adhesive fracture.

• Restorative Dentistry and Endodontics
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• 제25권2호
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• pp.289-298
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• 2000

Carbamide peroxide is usually used for vital teeth bleaching at home. Complications such as tooth hypersensitivity and/or gingival irritation are frequently reported. Therefore, this study was performed to evaluate any possible histological changes in pulp and periodontal tissue by carbamide peroxide bleaching gel in rats. 10% and 15% carbamide peroxide containing nightguard for upper molar were worn for 4 hours a day. The rats were sacrificed after 1 day, 2 days, 3 days, 4 days and 6 days application of carbamide peroxide respectively. The results were as follows : Mild infiltration of inflammatory changes below the junctional epithelium and hyperplasia of epithelium were observed in both 10% and 15% carbamide peroxide treated groups. In all experimental groups, odontoblasts were changed from columnar to cuboidal shape and/or obliterated and the focal loss of predentin was observed in pulp horn. With increasing time of application, these changes were more remarkable, but limited in pulp horn. Inflammatory reactions, vacuolar changes and hyaline degenerations of the pup tissue were also observed in some cases. These results suggested that carbamide peroxide gel used in home bleaching could cause reversible pulpal irritation.

• 대한본초학회지
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• 제37권5호
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• pp.53-61
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• 2022

Objectives : The aim of this study was to investigate the effect of Baicalein (BA) on the production of hydrogen peroxide in lipoteichoic acid-stimulated RAW 264.7 mouse macrophages. Methods : Lipoteichoic acid-stressed RAW 264.7 mouse macrophages were incubated with baicalein at concentrations of 50 and 100 µM. Incubation time is 30 minutes, 2 h, 12 h, and 18 h. After incubation, The production of hydrogen peroxide in RAW 264.7 mouse macrophages was measured with dihydrorhodamine 123 assay. Streptococcus aureus lipoteichoic acid and Streptococcus pyogenes lipoteichoic acid were used as cell-stimulating lipoteichoic acid. Cell viabilities were measured with a modified MTT assay. Berberine, indomethacin, and gallic acid were incubated for the same time as the comparative materials. Results : BA at the concentration of 50 and 100 µM did not show cytotoxicity on RAW 264.7 mouse macrophages for 24 h incubation. For 30 minutes, 2 h, 12 h, and 18 h incubation, BA at the concentration of 50 and 100 µM significantly inhibited the production of hydrogen peroxide in RAW 264.7 mouse macrophages stimulated by Streptococcus aureus lipoteichoic acid (p < 0.05); also, BA at the concentration of 50 and 100 µM also inhibited the productions of hydrogen peroxide in RAW 264.7 mouse macrophages stimulated by Streptococcus pyogenes lipoteichoic acid significantly (p < 0.05). Conclusions : BA might have anti-bacterial activity related to its inhibition of hydrogen peroxide production in lipoteichoic acid-stimulated RAW 264.7 mouse macrophages.

• 대한치과의사협회지
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• 제39권11호통권390호
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• pp.926-935
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• 2001

• Bulletin of the Korean Chemical Society
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• 제35권9호
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• pp.2704-2710
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• 2014

Catalase (CAT) decomposes hydrogen peroxide that is toxic to the body. In this study, simple and sensitive detector has been developed for observing catalase activity using liquid crystal droplet system. Microscale LC droplet patterns are formed by spreading aldehyde-doped nematic liquid crystal on pre-treated glass slides. When hydrogen peroxide is added, aldehyde is oxidized and amphiphiles are formed. Dodecanoates cause the pattern to transit from bright to dark as they self-assemble to form a carboxyalte monolayer at the interface. When a drop of pre-incubated CAT and hydrogen peroxide mixture is placed onto the pattern, bright fan-shape is observed. This planar optical appearance indicates that catalase has decomposed hydrogen peroxide. Compared to the detectors that have been previously developed, this system is more sensitive with detection limit of 1fM. This research suggests further studies to be on LC droplet patterning to develop highly sensitive and methodologically simple sensors for various chemicals.

• Biomolecules & Therapeutics
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• 제12권4호
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• pp.228-234
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• 2004

Brazilin shows hypoglycemic effect in diabetic animals through enhancement of glucose metabolisms in insulin responsive tissues. One of the major mechanisms of brazilin to enhance glucose metabolism is stimulation of glucose transport in adipocytes. In this study, the essential molecular moiety of brazilin for the stimulation of glucose transport was investigated. We found that brazilin undergoes a structural change in physiological buffer and produces hydrogen peroxide. Methylation of hydroxyl group of brazilin or addition of catalase along with brazilin resulted in the complete inhibition of brazilin-induced glucose transport in adipocytes. Because hydrogen peroxide increases glucose transport by inhibition of phosphatases, we examined the effect of brazilin on phosphatase activity. Brazilin inhibited phosphatases in a wide range of activity, and protein phosphatase 1 and 2A were also inhibited. These results suggest that the production of hydrogen peroxide by oxidation of catechol hydroxyl group of brazilin mediates glucose transport through inhibition of phosphatases which otherwise decrease glucose transport in adipocytes.

• 한국환경보건학회지
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• 제27권1호
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• pp.1-7
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• 2001

Ammonia is used in the manufacture of fertilizers, refrigerants, stabilizers and many household cleaning agents. These wide applications resulted in ammonia contamination in water. Ammonia can be removed from water by physical, biological, and chemical methods. Ozonation is effictive in the treatment of water with low concentration of ammonia. This study is undertaken to provide kinetic data for the ozonation of ammonia with or without hydrogen peroxide. The results were as follows; The destruction rate of ammonia increased gradually with the influent hydrogen peroxide concentration up to 0.23 mM and inhibited in the range of 0.23~11.4mM, and the maximum removal rate of ammonia achieved at 0.23mM of hydrogen peroxide, and the overall kinetics was first order. The combination effect of hydrogen and ozone to oxide ammonia in aqueous solution was better than ozone alone. The reacted ammonia was converted completely to nitrate ion.

• International Journal of Automotive Technology
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• 제8권4호
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• pp.413-419
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• 2007

Experimental study of additives on the ignition performance of a compression ignition natural gas engine is introduced, followed by results of a simulation of its working mechanism. From the experimental results, it is understood that engine ignition performance can be improved when a certain amount of Di-tertiary-butyl peroxide additive is added. If the mass fraction of Di-tertiary-butyl peroxide additive reaches as high as 14.2%, engine ignition can be realized at ambient temperatures with a glow plug temperature of about $750^{\circ}C$. From the simulation results, we verify that the Di-tertiary-butyl peroxide additive, by cracking its radicals at lower temperature, can accelerate reaction rate. Therefore, the additive is able to improve the ignition performance of natural gas significantly.