• Journal of Microbiology and Biotechnology
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• v.24 no.6
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• pp.771-780
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• 2014

A putative lipolytic enzyme gene, named as est9x, was obtained from a marine microbial metagenome of the South China Sea. Sequence analysis showed that Est9X shares lower than 27% sequence identities with the characterized lipolytic enzymes, but possesses a catalytic triad highly conserved in lipolytic enzymes of the ${\alpha}/{\beta}$ hydrolase superfamily. By phylogenetic tree construction, Est9X was grouped into a new lipase/esterase family. To understand Est9X protein in depth, it was recombinantly expressed, purified, and biochemically characterized. Within potential hydrolytic activities, only lipase/esterase activity was detected for Est9X, confirming its identity as a lipolytic enzyme. When using p-nitrophenol esters with varying lengths of fatty acid as substrates, Est9X exhibited the highest activity to the C2 substrate, indicating it is an esterase. The optimal activity of Est9X occurred at a temperature of $65^{\cric}C$, and Est9X was pretty stable below the optimum temperature. Distinguished from other salt-tolerant esterases, Est9X's activity was tolerant to and even promoted by as high as 4 M NaCl. Our results imply that Est9X is a unique esterase and could be a potential candidate for industrial application under extreme conditions.

• Analytical Science and Technology
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• v.5 no.4
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• pp.465-469
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• 1992

An analytical procedure is presented for the quantitative determination of lactose, glucose, and galactose in the hydrolyzate of lactose by ${\beta}$-galactosidase with high-performance liquid chromatography. An Aminex HPX-87C column at $85^{\circ}C$ and refractive index detector were used to resolve lactose, glucose, and galactose in only 12 minutes with distilled and deionized water as a mobile phase. The validity of high-performance liquid chromatography as a method for the assay of ${\beta}$-galactosidase was supported by recovery experiments and comparision of results with those by ONPG method, a spectrophotometric assay. The procedure was appropriate for determination of sugars in the enzyme reaction mixture and could by applied to analysis of ${\beta}$-galactosidase activity.

• Korean Journal of Microbiology
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• v.43 no.4
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• pp.279-284
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• 2007

Two bacterial strains isolated from soil (Bacillus subtilis strains: PS2 and RFO41) were evaluated to determine their promoting effect on the growth of tomato seedling under axonic and pot conditions. The production of phytohormone, such as indole-3-acetic acid, indole-3-butyric acid, gibberellin and zeatin by these two strains was investigated as possible mechanisms for plant growth stimulation. Both PS2 and RFO41 were shown to produce various phytohormones, and. the production of phytohormones was stimulated by the addition of peptone-rich brain heart broth medium. In addition, these bacteria exhibited high levels of phosphatase activity, which ranged from 2.18 to $2.7\;{\mu}\;{\rho}-nitrophenol/ml/hr$. PS2 and RFO41 were applied to the pot test for growth of tomato seed with phosphate. Root and shoot lengths of germinated tomato after 15 days were 45.5% and 36.5% longer than that of control in RFO41 treated samples, respectively. Baciller sp. PS2 and RFO41 may have a potential for biofertilizer in the agriculture.

• Korean Journal of Acupuncture
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• v.23 no.4
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• pp.177-186
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• 2006

목적 : 약침액(藥鐵液)의 지질과산화 예방 및 cytocome P450과의 상호 작용에 있어서 대계의 역할은 과거 연구가 거의 없었다. 따라서 본 실험에서는 대계 약침액이 지질과산화를 예방하고, 심혈관계질환 유발에 밀접한 연관이 있는 cytochrome P450의 직접적인 저해 효과를 검토 하고자 한다. 방법 : 대계 약침액이 지질과산화를 억제하는 정도를 평가하기 위하여 세포막을 구성하는 불포화지방산의 일종인 linoleic acid를 대상으로 지질과산화 진행 시간과 대계 약침액의 농도에 의존적인 저해 효과를 실험하였다. 또한 실험쥐의 간조직을 이용하여, 강제적인 과산화를 유도한 후 이를 방어하는 효능을 검토하였다. 그리고 cytochrome P450을 구성하는 그룹의 1A1, 1A2 및 2E1의 활성을 각각 EROD, MROD, p-nitrophenol, aniline 방법으로 측정하였다. 결과 및 결론 : 대계 약침액은 세포막 구성의 불포화 지방산인 linoleic acid의 산화를 시간 및 처리 농도에 의존적으로 억제하였고, 실험쥐의 조직 과산화를 유의성 있게 저해하였다. 또한 aryl hydrocarbon receptor (AHR)을 활성화 시켜 polycyclic aromatic hydrocarbons (PAHs)에 의한 심혈관계 질환 유발 인자로 알려진 cytochrome P450 1A1 및 1A2의 발현을 일부 저해하였으며, 특히 체내에 흡수된 알콜 대사에 관여하는 P450 2E1을 강하게 억제 시켰다.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2220-2231
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• 2018

Lipase from Candida rugosa was immobilized on $MgO{\cdot}SiO_2$ hybrid grafted with amine, thiol, cyano, phenyl, epoxy and carbonyl groups. The products were analyzed using Fourier transform infrared spectroscopy, nuclear magnetic resonance, low-temperature $N_2$ sorption and elemental analysis. Additionally, the degree of coverage of the oxide material surface with different functional groups and the number of surface functional groups were estimated. The Bradford method was used to determine the quantity of immobilized enzyme. The largest quantity of enzyme (25-28 mg/g) was immobilized on the hybrid functionalized with amine and carbonyl groups. On the basis of hydrolysis reaction of p-nitrophenyl palmitate to p-nitrophenol, it was determined how the catalytic activity of the obtained biocatalysts is affected by pH, temperature, storage time, and repeated reaction cycles. The best results for catalytic activity were obtained for the lipase immobilized on $MgO{\cdot}SiO_2$ hybrids with amine and carbonyl groups. The biocatalytic system demonstrated activity above 40% in the pH range 4-10 and in the temperature range $30-70^{\circ}C$. Lipase immobilized on the $MgO{\cdot}SiO_2$ systems with amine and epoxy groups retains, respectively, around 80% and 60% of its initial activity after 30 days of storage, and approximately 60-70% after 10 reaction cycles.

• Analytical Science and Technology
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• v.17 no.5
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• pp.393-400
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• 2004

Nitrosation of phenol (POH) was studied by adding hydrochloric acid and sodium nitrite to phenol solution with reaction temperature and time change. The optimum condition of nitrosation was found from the effects of hydrochloric acid and sodium nitrite concentration, reaction temperature, and reaction time changes on the production of nitrosophenol (POHNO). As a result, it was found that the optimum conditions were $5.0{\times}10^{-4}{\sim}2.0{\times}10^{-3}M$ range of $NO{_2}^-$ concentration, more than 0.10 M of HCl concentration, temperature of $80^{\circ}C$, and 3 hrs. of reaction time. In this condition, 10 U.S. E.P.A. classified priority environmental pollutant, phenols, were nitrosated. Nitrosated phenols were: POH, 2-Chlorophenol (2ClPOH), 2,4-diChlorophenol (2ClPOH), 2,4-dimethylphenol (24diMPOH), and 4-Chloro -3-methylphenol (4Cl3MPOH), and a small part of 2-nitrophenol (2NPOH). The ${\lambda}_{max}$ values of nitrosated phenols in acidic solution were around 300 nm, and those in basic solution were around 400 nm. Molar absorptivities (${\varepsilon}$) at the 400 nm of the nitrosated phenols in the basic solution were 1.5~2.0 times larger than those at 300 nm in acidic solution. It was also found by Capillary-HPLC chromatograms of the nitrosated phenol solutions that the production of the nitrosophenols were interfered by the excess concentration of nitrite (more than $3.0{\times}10^{-3}M$).

• Carbon letters
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• v.23
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• pp.38-47
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• 2017

In this study, magnetite ($Fe_3O_4$) nanoparticles were electrochemically synthesized in an aqueous electrolyte at a given potential of -1.3 V for 180 s. Scanning electron microscopy revealed that dendrite-like $Fe_3O_4$ nanoparticles with a mean size of < 80 nm were electrodeposited on a glassy carbon electrode (GCE). The $Fe_3O_4/GCE$ was utilized for sensing chloramphenicol (CAP) by cyclic voltammetry and square wave voltammetry. A reduction peak of CAP at the $Fe_3O_4/GCE$ was observed at 0.62 V, whereas the uncoated GCE exhibited a very small response compared to that of the $Fe_3O_4/GCE$. The electrocatalytic ability of $Fe_3O_4$ was mainly attributed to the formation of Fe(VI) during the anodic scan, and its reduction to Fe(III) on the cathodic scan facilitated the sensing of CAP. The effects of pH and scan rate were measured to determine the optimum conditions at which the $Fe_3O_4/GCE$ exhibited the highest sensitivity with a lower detection limit. The reduction current for CAP was proportional to its concentration under optimized conditions in a range of $0.09-47{\mu}M$ with a correlation coefficient of 0.9919 and a limit of detection of $0.09{\mu}M$ (S/N=3). Moreover, the fabricated sensor exhibited anti-interference ability towards 4-nitrophenol, thiamphenicol, and 4-nitrobenzamide. The developed electrochemical sensor is a cost effective, reliable, and straightforward approach for the electrochemical determination of CAP in real time applications.

• Journal of the Korean Chemical Society
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• v.39 no.12
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• pp.918-924
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• 1995

THMs and PCBs were separated and analysed with elution on Novapak ODS or $\mu-Bondapak$ phenyl column by an eluent containing p-nitrophenol (p-NP). THMs studied were CHCl3, CHBrCl2, CHBr2Cl, and CHBr3, and PCBs used were Aroclor 1221, 1242, 1248, $\alpha-$ and $\beta-BHC.$ It was thought that the retention on the stationary phase and sensitivities of the samples are related to the interaction between the sample and stationary phase or p-NP. THMs were separated completely on the ODS column by elution with MeOH-water (30 : 70) containing $1.0{\times}10^{-4}$ M p-NP and some of PCBs were separated on the phenyl column by elution with $CH_3CN$-water(50 : 50) containing $1.0{\times}10^{-4}$ M p-NP. Detection limits of THMs were from $1.0{\times}10^{-4}$ g to $1.0{\times}10^{-6}$ g. Aroclors were $2{\times}10^{-6}$ g, and $\alpha-$ and $\beta-BHC$ were $2{\times}10^{-4}$ g and $1.0{\times}10^{-4}$ g respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.588-588
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• 2013

Nanoscale noble-metals have attracted enormous attention from researchers in various fields of study because of their unusual optical properties as well as novel chemical properties. They have possible uses in diverse applications such as devices, transistors, optoelectronics, information storages, and energy converters. It is well-known that nanoparticles of noble-metals such as silver and gold show strong absorption bands in the visible region due to their surface-plasmon oscillation modes of conductive electrons. Silver nanocubes stand out from various types of Silver nanostructures (e.g., spheres, rods, bars, belts, and wires) due to their superior performance in a range of applications involvinglocalized surface plasmon resonance, surface-enhanced Raman scattering, and biosensing. In addition, extensive efforts have been devoted to the investigation of Gold-based nanocomposites to achieve high catalytic performances and utilization efficiencies. Furthermore, as the catalytic reactivity of Silver nanostructures depends highly on their morphology, hollow Gold nanoparticles having void interiors may offer additional catalytic advantages due to their increased surface areas. Especially, hollow nanospheres possess structurally tunable features such as shell thickness, interior cavity size, and chemical composition, leading to relatively high surface areas, low densities, and reduced costs compared with their solid counterparts. Thus, hollow-structured noblemetal nanoparticles can be applied to nanometer-sized chemical reactors, efficient catalysts, energy-storage media, and small containers to encapsulate multi-functional active materials. Silver nanocubes dispersed in water have been transformed into Ag@Au nanoboxes, which show highly enhanced catalytic properties, by adding $HAuCl_4$. By using this concept, $SiO_2$-coated Ag@Au nanoboxes have been synthesized via galvanic replacement of $SiO_2$-coated Ag nanocubes. They have lower catalytic ability but more stability than Ag@Au nanoboxes do. Thus, they could be recycled. $SiO_2$-coated Ag@Au nanoboxes have been found to catalyze the degradation of 4-nitrophenol efficiently in the presence of $NaBH_4$. By changing the amount of the added noble metal salt to control the molar ratio Au to Ag, we could tune the catalytic properties of the nanostructures in the reduction of the dyes. The catalytic ability of $SiO_2$-coated Ag@Au nanoboxes has been found to be much more efficient than $SiO_2$-coated Ag nanocubes. Catalytic performances were affected noteworthily by the metals, sizes, and shapes of noble-metal nanostructures.

• Toxicological Research
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• v.24 no.1
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• pp.37-44
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• 2008

The in vitro cell transformation assays (CTA) were performed using BALB/3T3 murine fibroblasts and HaCaT human keratinocytes in order to evaluate concordance between both in vitro CTAs and carcinogenicity with compounds differing in their genotoxic and carcinogenic potential. Six test articles were evaluated, two each from three classes of compounds: genotoxic carcinogens (2-amino-5-nitrophenol and 4-nitroquinoline-N-oxide), genotoxic noncarcinogens (8-hydroxyquinoline and benzyl alcohol), and nongenotoxic carcinogens (methyl carbamate and N-nitrosodiphenylamine). Any foci of size $\geq$2 mm regardless of invasiveness and piling was scored as positive in CTA with BALB/3T3. As expected, four carcinogens regardless of their genotoxicity had positive outcomes in two-stage CTA using BALB/3T3 cells. However, of the two genotoxic noncarcinogens, benzyl alcohol was positive CTA finding. We concluded that, of the 6 chemicals tested, the sensitivity for BALB/3T3 system was reasonably high, being 100%. The respective specificity for BALB/3T3 assay was 50%. We also investigated the correlation between results of BALB/3T3 assay and results from HaCaT assay in order to develop a reliable human cell transformation assay. However, evaluation of staining at later time points beyond the confluency stage did not yield further assessable data because most of HaCaT cells were detached after $2{\sim}3$ days of confluency. Thus, after test article treatment, HaCaT cells were split before massive cell death began. In this modified protocol for this HaCaT system, growing attached colonies were counted instead of transformed foci 3 weeks since last subculture. Compared to BALB/3T3 assay, HaCaT assay showed moderate low sensitivity and high specificity. Despite these differences in specificity and sensitivity, both cell systems did exhibit same good concordance between in vitro CTA and rodent carcinogenicity findings (overall 83% concordant results). At present the major weakness of these in vitro CTA is lack of validation for regulatory acceptance and use. Thus, more controlled studies will be needed in order to be better able to assess and quantitatively estimate in vitro CTA data.