• Journal of Microbiology and Biotechnology
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• v.19 no.12
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• pp.1582-1589
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• 2009

Bacterial UDP-N-acetylglucosamine enolpyruvyl transferase (MurA) catalyzes the transfer of enolpyruvate from phosphoenolpyruvate (PEP) to uridine diphospho-N-acetylglucosamine (UNAG), which is the first step of bacterial cell wall synthesis. We identified thimerosal, thiram, and ebselen as effective inhibitors of Haemophilus influenzae MurA by screening a chemical library that consisted of a wide range of bioactive compounds. When MurA was preincubated with these inhibitors, their 50% inhibitory concentrations ($IC_{50}s$) were found to range from 0.1 to $0.7\;{\mu}M$. In particular, thimerosal suppressed the growth of several different Gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhimurium at a concentration range of $1-2\;{\mu}g/ml$. These inhibitors covalently modified the cysteine residue near the active site of MurA. This modification changed the open conformation of MurA to a more closed configuration, which may have prevented the necessary conformational change from occurring during the enzyme reaction.

• Advances in nano research
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• v.4 no.4
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• pp.281-294
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• 2016

The advantages of nano-scale materials (size 1-99 nm in at least in one dimension) could be realized with their potential applications in diversified avenues. Herein, we report for the first time on the successful synthesis of homogeneous epoxy coatings containing phytogenic silver nanoparticles (Ag) on PVC and glass substrates by room-temperature curing of fully mixed epoxy slurry diluted by acetone. Alstonia scholaris bark extract was used to reduce and stabilize the silver ions. The surface morphology and mechanical properties of these coatings were characterized using the techniques like, UV-Vis (UV-Visible) spectrophotometry, X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FT-IR), Epifluorescence microscopy and scanning electron microscopy (SEM). The effect of incorporating Ag nanoparticles on the biofilm (scale) resistant epoxy-coated PVC was investigated by total viable counts ($CFU/cm^2$) from epoxy coating from (Initial) $1^{st}$ day to $25^{th}$ days. The phytogenic Ag nanoparticles were found to be significantly improving the microstructure of the coating matrix and thus enhanced the anti-biofilm performance of the epoxy coating. In addition, the antimicrobial mechanism of Ag nanoparticles played an important role in improving the anti-biofilm performance of these epoxy coatings.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.44.2-45
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• 2021

As implied by the zodiacal light and spacecraft impact measurements, the space between large bodies in our Solar System is filled with interplanetary dust particles (IDPs). IDPs give us deeper insight into the composition and evolution of the Solar System, as well as being a crucial reference for extrasolar research. IDPs can be interpreted as bearers of carbon and organic materials, and thus, their interaction with Earth can be considered as important factors for the birth of terrestrial life. One of the key routes of IDPs entering Earth is via meteoroid streams (Love and Brownlee 1993). The Geminid meteoroid stream is a notable example. Together with its source asteroid (3200) Phaethon, the Phaethon-Geminid stream complex (PGC) (Whipple 1983; Gustafson 1989) can potentially provide information on the properties and evolution of IDPs in near-Earth space. DESTINY+* is a JAXA/ISAS spacecraft planned to launch in 2024 to explore the physical and chemical features of near-Earth IDPs and uncover the dust ejection mechanism of active near-Earth asteroids, especially Phaethon (Arai et al. 2018). Previous studies on the dust ejection mechanism of Phaethon have various degrees of success in explaining the ejection of submillimeter particles and try to recreate the dust replenishment rate of the Geminid stream. However, none of them are satisfactory for explaining the observed Geminid stream, especially for larger particles of a millimeter and centimeter scales. Inspired by the discovery of rotational mass shedding in the Main Belt region (Jewitt et al., 2014), we investigate a dust ejection scenario by rotational instability on Phaethon. Using the N-body integrator MERCURY6 (Chambers 1999; modified by Jeong 2014), we performed a long-term integration of dust particles of various sizes ejected at ~1 m/s. Through this process, we discuss the implications Phaethon's rotation may have on its ejection, the formation and evolution of IDP by this mechanism, and contribute to the DESTINY+ mission.

• The Korean Journal of Physiology and Pharmacology
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• v.7 no.6
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• pp.357-362
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• 2003

Carbon monoxide (CO) is low molecular weight oxide gas that is endogenously produced under physiological conditions and interacts with another gas, nitric oxide (NO), to act as a gastrointestinal messenger. The aim of this study was to determine the effects of exogenous CO on L-type calcium channel currents of human jejunal circular smooth muscle cells. Cells were voltage clamped with 10 mM barium ($Ba^{2+}$) as the charge carrier, and CO was directly applied into the bath to avoid perfusion induced effects on the recorded currents. 0.2% CO was increased barium current ($I_{Ba}$) by $15{\pm}2$% ($mean{\pm}S.E.$, p<0.01, n=11) in the cells. To determine if the effects of CO on barium current were mediated through the cGMP pathway, cells were pretreated with 1-H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, $10{mu}M$), a soluble guanylyl cyclase inhibitor, and exogenous CO (0.2%) had no effect on barium currents in the presence of ODQ ($2{\pm}1$% increase, n=6, p>0.05). CO mediates inhibitory neurotransmission through the nitric oxide pathway. Therefore, to determine if the effects of CO on L-calcium channels were also mediated through NO, cells were incubated with $N^G-nitro-L-arginine$ (L-NNA, 1 mM), a nitric oxide synthase inhibitor. After L-NNA pretreatment, 0.2 % CO did not increase barium current ($4{\pm}2$% increase, n=6, p>0.05). NO donor, SNAP ($20{\mu}M$) increased barium current by $13{\pm}2$% (n=6, p<0.05) in human jejunal smooth muscle cells. These data suggest that CO activates L-type calcium channels through NO/cGMP dependant mechanism.

• Journal of Korean society of Dental Hygiene
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• v.11 no.3
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• pp.301-311
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• 2011

Objectives : In order to identify the awareness of influenza A (H1N1) having currently high frequency and risk as an infectious disease, to find problems and to reflect them on curriculum improvements from students before/after clinical practices. Methods : The data was collected from 279 dental hygiene students of 1st and 2nd years at G health college university from December 6th 2010 to December 10th 2010. The questionnaire were consisted of awareness of influenza A (H1N1), preventive attitude, sociodemographic characteristics. Results : 1. 1st year was 51.6%, the case having dental experience was 51.2%, in the infection control training experience 'had' was 46.6%. In the route acquiring the information, the mass media was 70.6%, in obtained information, personal hygiene was 82.1%. In the impact on human body, 'great impact' was 58.1%. In terms of the most need for response and preparedness, vaccination was the highest, 67.4%. People who experienced influenza A (H1N1) were 10.7%. 2. Awareness of influenza A (H1N1) was 0.71 points, and treatment and spreading mechanism was 0.78 points, prevention was 0.63 points, causes and definition was 0.53 points. 3. In the attitude for infection prevention of influenza A (H1N1), 'washing hands before practice' was the highest, 0.99 points and 'wear the mask only in case of contact with patient within 1~2 meters upon occurrence of no aerosol' was the lowest, 0.72 points. 4. Awareness of influenza A (H1N1) according to sociodemographic characteristics showed the significant differences upon the impacts on systemic health (p<0.05). Preventive attitude didn't show a significant difference in grade, clinical experience, experience in infection control training, acquiring rmation routes, the possibility for occurrence, impact on systemic health, the most need for prevention, experience in influenza A (H1N1) (p>0.05). 5. The significantly correlated between awareness of influenza A (H1N1) and preventive attitude(p<0.01). Conclusions : Information and preventive attitude for influenza A (H1N1) as well as systematic training programs to identify actual affecting factors and to improve the practice are needed. Also government's institutional support is needed.

• Journal of the Korean Chemical Society
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• v.23 no.6
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• pp.339-348
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• 1979

The kinetics of the solvolysis of 2-furoyl chloride and 2-thenoyl chloride in $MeOH-H_2O,\;EtOH-H_2O,\;(Me)_2CO-H_2O,\;MeCN-H_2O$ and MeCN-MeOH has been investigated. The rates were faster in protic solvents than in aprotic solvents. This was caused by the bond breaking of leaving group through hydrogen-bonding solvation of protic solvents. In MeCN-M$\'{e}$OH the rate in MeOH rich solvents was faster than in MeCN rich solvents by the specific solvation of alcoholic hydrogen and there was a maximum rate of reaction at MeOH mole fraction of 0.8. The reaction rates of solvolysis were considerably slower than those of benzoyl chloride owing to the electron withdrawing effect of thienyl and furyl groups. It was concluded that solvolytic reaction proceeds via a dissociative $S_N2$ mechanism in which bond-breaking precedes bond-formation at the transition state.

• Journal of the Korean Chemical Society
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• v.29 no.1
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• pp.15-22
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• 1985

Kinetic studies of nucleophilic substitution reaction of substituted benzoyl cyanides and benzoyl chlorides with pyridines were conducted at 25$^{\circ}C$ in pure acetone solvent. Results showed that (ⅰ) magnitudes of $_{\rho}_S$, $_{\rho}_N$ and ${\beta}$ associated with a change of substituent in the nucleophile indicate relatively advanced bond-formation in the transition state, (ⅱ) the potential energy surface model is able to predict the reaction mechanism, but it is unable to predict the transition state variation to a more product-like transition state, where bond-formation is much more progressed than bond breaking, upon changing the leaving group to that with better leaving ability (ⅲ) the quantum mechanical model predicted the product-like transition state and slightly better leaving ability of CN- as compared with Cl-.

• Fisheries and Aquatic Sciences
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• v.21 no.6
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• pp.16.1-16.7
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• 2018

Background: Matrix metalloproteinases (MMPs) are linked with several complications such as metastasis of cancer progression, oxidative stress, and hepatic fibrosis. Brown seaweeds are being extensively studied for their bioactive molecule content against cancer progression. In this context, Sargassum horneri was reported to possess various bioactivities including antiviral, antimicrobial, and anti-inflammatory partly due to its phenolic compound content. Methods: In this study, potential of S. horneri was evaluated through anti-MMP effect in HT1080 fibrosarcoma cells. S. horneri crude extract was fractionated with organic solvents, namely, water ($H_2O$), n-buthanol (n-BuOH), 85% aqueous methanol (85% aq. MeOH), and n-hexane. The non-toxicity of fraction samples (Sargassum horneri solvent-partitioned extracts (SHEs)) was confirmed by cell-viability assay. SHEs were tested for their ability to inhibit MMP enzymatic activity through gelatin digestion evaluation and cell migration assay. Expressions of MMP-2 and MMP-9 and tissue inhibitors of MMP (TIMPs) were evaluated by reverse transcription and Western blotting. Results: All fractions inhibited the enzymatic activities of MMP-2 and MMP-9 according to gelatin zymography. Except $H_2O$ fraction, fractions hindered the cell migration significantly. All tested fractions suppressed both mRNA and protein levels of MMP-2, MMP-9, TIMP-1, and TIMP-2. Conclusion: Overall, current results suggested that S. horneri has potential to be a good source for anti-MMP agents, and further investigations are underway for better understanding of the action mechanism and isolation and elucidation of the bioactive molecules.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.11a
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• pp.8-8
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• 2002

TiC core/(Ti,Mo)C rim structure in TiC-$Mo_2C$-Ni base cermet which is generally prepared by sintering below 145$0^{\circ}C$ had been believed to be generated by the solid diffusion of Mo atoms 1 into TiC grains (D. Moskowitz and M.Humenik, 1r.:1966). Afterward, it was clarified that the c core/rim structure is generated by solution/re-precipitation mechanism : (1) $Mo_2C$ grains and s small TiC grains dissolve into the Ni liquid, (2) the dissolved Mo, Ti and C atoms migrate to the s surface of TiC coarse grains, (3) the Mo, Ti and C precipitate on the surface of TiC coarse g grains and form (Ti,Mo)C solid solution rim, and (4) the Ostwald ripening (grain growth by s solution/re-precipitation mechanism) of TiC-core/(Ti,Mo)-rim grains continues, and thus the w width of (Ti,Mo)C rim (at the same time, the grain size) increases with sintering time, etc. ( (H.Suzuki, K.Hayashi and O.Terada: 1973). The TiC-core was found not to disappear even by s sintering at 190$0^{\circ}C$ (ibid.: 1974) Recently, FeSi core/$Fe_2Si_5$-rim structure in Fe-66.7at%Si thermoelectric aIloy was found to also h hardly shrink and disappear by long heating at an appropriate temperature (1999: M.Tajima and K K.hayashD. Then, the authors considered its cause, and clarified experimentaIly that the disappearance of FeSi-core/$Fe_2Ski_5$-rim structure could be attributed to the exhaustion of diffusion-contributable vacancies in core/rim structure (N.Taniguchi and K.Hayashi:2001). At p present, the authors and my coworker are investigating whether the non-disappearance of TiC c core can be explained also from the new hypothesis "Exhaustion of diffusion-contributable v vacancies in corelrim structure".ure".uot;.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.10a
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• pp.187-187
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• 1997

Silicon nitride is the most excellent materials among structural ceramics. It has been reported that fracture toughness was improved with adding second phase particles, whisker, fiber etc. However, containing of second phase particles enhanced fracture toughness, however flexural strength was degraded. As adding nanosize SiC particles into silicon nitride, the physical properties of fluxural strength, fracture toughness, the modulus of elasticity. In this study, 2wt% $Al_2$O$_3$ and 4 wt% $Y_2$O$_3$ were added into UBE E-10 and 0, 10, 20, 30, 40, 50 vol% nano-SiC powder (Sumitomo T1 powder) were added, respectively. It is hot pressed at 185$0^{\circ}C$ for 1 hour. Most of structural ceramics for engineering application are wear resistance. In this study, wear behaviors (in water) of silicon nitride with varying the amount of nano-size silicon carbide were investigated, and was compared to physical properties. Simultaneously wear mechanism will be found out.