• Journal of Microbiology and Biotechnology
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• 제30권4호
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• pp.615-621
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• 2020

Laccases are multicopper oxidases with important industrial value. In the study, a novel laccase gene (mco) in a Staphylococcus haemolyticus isolate is identified and heterologously expressed in Escherichia coli. Mco shares less than 40% of amino acid sequence identities with the other characterized laccases, exhibiting the maximal activity at pH 4.0 and 60℃ with 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) as a substrate. Additionally, the Mco is tolerant to a wide range of pH, heavy metal ions and many organic solvents, and it has a high decolorization capability toward textile dyes in the absence of redox mediators. The characteristics of the Mco make this laccase potentially useful for industrial applications such as textile finishing. Based on BLASTN results, mco is found to be widely distributed in both the bacterial genome and bacterial plasmids. Its potential role in oxidative defense ability of staphylococci may contribute to the bacterial colonization and survival.

• Journal of Microbiology and Biotechnology
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• 제9권2호
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• pp.173-178
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• 1999

The extracellular cytosine deaminase (EC 3.5.4.1) from Chromobacterium violaceum YK 391 was purified 264.7-fold with an overall yield of 14.3%. The enzyme was for the first time homogeneous by the criteria of polyacrylamide gel electrophoresis performed in the absence and in the presence of sodium dodecyl sulfate. The molecular weight of the purified enzyme was estimated to be about 156 kDa. The enzyme consisted of two identical subunits of approximate molecular weight 78 kDa. The isoelectric point of the enzyme was pH 5.55. The enzyme had a pH optimum of 7.5 and a temperature optimum of around 40 to $45^{\circ}C$. Besides cytosine, the enzyme deaminated 5-fluorocytosine, cytidine, 5-methylcytosine, and 6-azacytosine, but not 5-azacytosine. The extracellular cytosine deaminase is believed to be unique because it was active not only on cytosine but also on cytidine. The apparent $K_m$ values for cytosine, 5-fluorocytosine, cytidine, and 5-methylcytosine were determined to be 1.55 mM, 5.52 mM, 10.4 mM, and 67.2 mM, respectively. The enzyme activity was strongly inhibited by heavy metal ions such as $Fe^{2+},Pb^{2+},Cd^{2+},Zn^{2+}, Hg^{2+}, and Cu^{2+}$ at 1 mM, and completely by $\alpha,\alpha$'-dipyridyl, and $\rho$-chloromercuribenzoate at 1 mM, and weakly inhibited by 1mM ο-phenanthroline. The enzyme activity was not affected by various nucleosides and nucleotides.

• 한국항공우주학회지
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• 제42권11호
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• pp.981-987
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• 2014

DC/DC 컨버터는 임의의 직류전원을 부하가 요구하는 형태의 직류전원으로 변환시키는 효율이 높은 전력변환기이다. DC/DC 컨버터는 MOSFET(산화물-반도체 전계 효과 트랜지스터), PWM-IC(펄스폭 변조 집적회로) 제어기, 인덕터, 콘덴서 등으로 구성되어있다. MOSFET는 스위치 기능을 수행하는데 코발트 60 ($^{60}Co$) 저준위 감마발생기를 이용한 TID 실험에서 방사선의 영향으로 문턱전압과 항복전압의 변화와 SEGR 실험에 적용된 5종류의 중이온 입자는 MOSFET의 게이트(gate)에 영향을 주어 게이트가 파괴된다. MOSFET의 TID 실험은 40 Krad 까지 수행하였으며, SEGR 실험은 제어보드를 구현한 후 LET(MeV/mg/$cm^2$)별 cross section($cm^2$)을 연구하는데 있다.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.144-144
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• 2017

Micronutrients such as zinc (Zn), iron (Fe), manganese (Mn) have important roles for development and growth in plants but it also have roles in animals and humans. In previous studies, a Korean weedy rice, KH2J was selected to have tolerance to heavy metal, lead (Pb) compared with a cultivar, Milyang23. To identify QTLs for micronutrients concentration in grain, an F2 population (120 plants) were developed from a cross between KH2J and an indica rice cultivar, Milyang23. To measure the concentration of eight ions, Zn, Fe, Mn, Pb, calcium (Ca), copper (Cu), cadmium (Cd) and arsenic (As), grains were collected and digested with 65% nitric acid, and the ion contents were measured using inductively coupled plasma mass spectrometry. A total 27 putative quantitative trait loci (QTLs) were detected on 12 chromosomes by single point analysis and 22 putative QTLs were detected by composite interval mapping. The co-locations of QTL for Zn, Fe and Mn were observed on chromosome 5. The QTLs for Cd, Cu and Zn were co-localized on chromosome 10, and QTLs for Zn, As and Mn was on chromosome 12. The Zn concentration in F2 generation showed significant correlation with concentrations of As (r = -0.4), Cu (r = 0.5) and Fe (r = 0.2) (P < 0.01). Also, the Ca concentration was significantly related with Mn and Fe concentrations (P < 0.01). Fine mapping of these QTLs is underway to analyze their functional relationship.

• 한국응용과학기술학회지
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• 제30권2호
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• pp.356-361
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• 2013

Lead (II) ion selective poly(aniline) solid contact electrode based on Tetramethylthiuram monosulfide ionophore as a sulfur containing sensing material is successfully developed. The electrode exhibits good linear response of 25.6 mV / decade (at $20{\pm}0.2^{\circ}C$, r2=0.995) within the concentration range of $1.0{\times}10^{-1}{\sim}4.0{\times}10^{-7}$ M Pb (II). The composition of this electrode was Ionophore : PVC : dioctylphthalate : potassiumtetrakis(4-chlorophenyl)borate : Oleic acid = 5.0 : 20.0 : 25.0 : 4.0 : 5.0. When we consider the results of using different composition electrodes based on only one potassiumtetrakis(4-chlorophenyl)borate or Oleic acid liphophlic additive, poly(aniline) solid contact electrode based on Tetramethylthiuram monosulfide ionophore with potassiumtetrakis(4-chlorophenyl)borate and Oleic acid liphophlic additive had the best result in response characteristics. The electrode shows good selectivity for lead (II) ion in comparison with alkali, alkaline earth, transition and heavy metal ions. This electrode is suitable for use with aqueous solutions of pH 3.0 ~ 7.0 and their standard deviation in the measured emf differences was ${\pm}2.94$ mV at Tris buffered lead sample solution of $1.0{\times}10^{-2}$ M and ${\pm}2.82$ mV at Tris buffered lead sample solution of $1.0{\times}10^{-3}$ M. Their stabilization time was less than 710 s. and response time was less than 16 s.

• 미생물학회지
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• 제30권4호
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• pp.305-309
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• 1992

Bacillus stearothermophilus 의 cytosine deaminase (EC 3. 5. 4.1 )를 수율 52.7% 로 7.2배 부분정제했다. 부분정제된 cytosine deaminase 는 cytosine 을 유일한 기질로 이용하였으머 5-methylcytosine 과 5-fluorocytosine 은 기질고 이용되지 못햇으며 cytosine 에 대한 Michaelis 정수 Km 값은 5.9 mM 이었다. 본효소는 pH 4.0 에서 7.0 까지의 폭 넓은 pH 영역에서 안정했으며 80.deg.C 에서 10 분간 열처리하여도 75% 이상의 효소활성이 잔존하여 높은 내열성 효소였다. 본 효소의 반응최적 pH 는 7.0-7.5 였으며 반응 최적 온도는 35. 37.deg.C 였다. 그리고 Arrhenium plot 에 의하여 계산된 활성화 에너지 값(Ea value) 은 26 Kcal/mol 이었다. 본 효소는 중금속인 1 mM의 $Cd^{2+}$ , $Hg^{2+}$ 및 $Cu^{2+}$ 에 의하여 완정히 실활되었으며 GMP 와 CMP 에 의해서는 효소활성이 촉진되었다. 특히 본 효소는 p-chloromercuribenzoate 에 의하여 효소 활성이 강하게 저해되어 thiol 효소임을 추정할 수 있었다.

• 한국방사선학회논문지
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• 제11권3호
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• pp.101-108
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• 2017

DC/DC 컨버터는 임의의 직류전원을 부하가 요구하는 형태의 직류전원으로 변환시키는 효율이 높은 전력변환기이다. 고급형 DC/DC 컨버터는 MOSFET(산화물-반도체 전계 효과 트랜지스터)를 제어하기 위해 OP-Amp.(연산 증폭기)를 실장한 PWM-IC(펄스폭 변조 집적회로)를 사용한다. OP-Amp.는 증폭기 기능을 수행하는데 방사선 영향으로 전기적 특성이 변화하는데 본 논문에서는 코발트 60 (60Co) 저준위 감마발생기를 이용한 TID실험과 5종류의 중이온 입자를 이용하여 SEL 실험을 수행하는데 바이어스(bias) 전류가 순간적으로 과전류가 흘러 SEL이 발생된다. OP-Amp.의 TID 실험은 조사율은 5 rad/sec.로 전체 조사량을 30 krad 까지 수행하였으며, SEL 실험은 제어보드를 구현한 후 LET($MeV/mg/cm^2$)별 cross section($cm^2$)을 이용하여 성능평가를 하는데 있다.

• Journal of Microbiology and Biotechnology
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• 제22권5호
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• pp.690-698
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• 2012

Cr-B2, a Gram-negative hexavalent chromium [Cr(VI)] reducing bacteria, was isolated from the aerator water of an activated sludge process in the wastewater treatment facility of a dye and pigment based chemical industry. Cr-B2 exhibited a resistance for 1,100 mg/l Cr(VI) and, similarly, resistance against other heavy metal ions such as $Ni^{2+}$ (800 mg/l), $Cu^{2+}$ (600 mg/l), $Pb^{2+}$ (1,100 mg/l), $Cd^{2+}$ (350 mg/l), $ZN^{2+}$ (700 mg/l), and $Fe^{3+}$ (1,000 mg/l), and against selected antibiotics. Cr-B2 was observed to efficiently reduce 200 mg/l Cr(VI) completely in both nutrient and LB media, and could convert Cr(VI) to Cr(III) aerobically. Cr(VI) reduction kinetics followed allosteric enzyme kinetics. The $K_m$ values were found to be 43.11 mg/l for nutrient media and 38.05 mg/l for LB media. $V_{max}$ values of 13.17 mg/l/h and 12.53 mg/l/h were obtained for nutrient media and LB media, respectively, and the cooperativity coefficients (n) were found to be 8.47 and 3.49, respectively, indicating positive cooperativity in both cases. SEM analysis showed the formation of wrinkles and depressions in the cells when exposed to 800 mg/l Cr(VI) concentration. The organism was seen to exhibit pleomorphic behavior. Cr-B2 was identified on the basis of morphological, biochemical, and partial 16S rRNA gene sequencing chracterizations and found to be Acinetobacter sp.

• 한국식품영양과학회지
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• 제8권1호
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• pp.25-30
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• 1979

공장지역(工場地域) 폐수(廢水)로부터 cadmium에 대(對)한 내성균(耐性菌)을 분리(分離)하였으며 이것은 Staphylococcus aureus로 동정(同定)되었다. 동(同) 균주(菌株)는 cadmium 이외(以外)의 중금속(重金屬)($Cr^{3+},\;Hg^{2+},\;Zn^{2+},\;Pb^{2+},\;Cu^{2+}$ 등(等))에 의(依)하여서는 10ppm의 농도(濃度)에서 평균(平均) 약(約) 30%의 증식(增殖)이 저해(沮害)되었으나 cadmium에 의(依)해서는 50ppm까지는 저해(沮害)되지 아니 하였다. 동(同) 균주(菌株)의 증식(增殖)을 완전(完全)히 저해(沮害)하기 위(爲)하여 500ppm의 cadmium농도(濃度)가 필요(必要)하였으나 동(同) 균주(菌株)를 10ppm의 cadmium 또는 $Pb^{2+}$ 존재하(存在下)에서 15시간(時間) 배양(培養)한 세균(細菌)은 500ppm의 cadmium 존재하(存在下)에서도 증식(增殖)이 가능(可能)하였다. 이상(以上)의 결과(結果)로부터 분리(分離)한 균주(菌株)는 타중금속(他重金屬)에 의(依)해서는 생육(生育)이 쉽게 저해(沮害)되나 cadmium에 의(依)해서는 상당한 농도(濃度)까지 생육(生育)이 저해(沮害)되지 아니하는 균체(菌體), 즉(卽) cadmium에 특이적(特異的)인 내성균(耐性菌)으로 판단(判斷)되었다.

• 분석과학
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• 제11권1호
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• pp.1-7
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• 1998

본 논문은 현장에서 미량 원소분석을 수행할 수 있는 휴대용 원자방출분광계인 HCGD-AES(Hollow Cathode Glow Discharge-Atomic Emission Spectrometer)1에 적용할 분석 및 제어용 프로그램의 제작에 관한 연구결과를 요약하였다. 단색화 장치의 부피를 최소화할 수 있도록 분석할 원소의 선 필터(line filter)를 사용하여 제작된 검출계에서 실시간 분석이 가능한 소프트웨어의 개발이 이루어 졌으며, 원소 분석 및 검량선 작성의 자동화를 바탕으로 쉽게 사용할 수 있는 노트북용 소프트웨어를 Windows 95 환경에서 구현하였다. 사용한 주 언어인 Delphi 2.0을 바탕으로 그밖의 프로그램 언어도 복합적으로 사용되었다. 특히 측정된 자료들은 데이터 베이스를 구축하여 최적 실험 환경 조건을 얻을 수 있도록 하였으며 보고서 작성 기능도 추가되었다. 본 프로그램은 분석 수행에 있어서 사용자 편의를 위해 디자인되었으므로 빠르게 배우고 분광분석의 다른 분야에도 적용할 수 있도록 개발되어 응용성과 활용성이 대폭 확대될 수 있다는 이점이 있다.