• 한국결정학회지
• /
• 제9권1호
• /
• pp.21-29
• /
• 1998

현재까지 알려진 마이크로 레이저 호스트용 물질 중에서 가장 우수한 물리적 특성을 갖고 잇는 LaSc3(BO3)4를 융액 인상법 조건하에서 단결정으로 육성시킬 수 있는 최적 성장조건을 규명하고자 하였다. 우선 LaSc3(B(3)4의 융융특성을 규명하기 위해 DTA에 의해 La(BO3)-Sc(BO3)계의 상평형도를 작성한 결과, 이 2성분계에서 LaSc3(BO3)4는 유일한 중간상(Intermediate phase)이었으며, 용융 전에 1495 ±2℃에서 Sc(BO3)와 융액으로 분리되는 비조화 분해반응(peritectic reaction)을 나타내었다 : LaSc3(BO3)4=Sc(BO3)+melt 히타 및 도가니의 상호관계와 단열 혹은 보온상태를 적절히 조절함으로써, 성장로의 열구조를 단결정 성장에 적합하게 하기 위해 열전대를 애프터히타 최상부로부터 융체 내부까지 상승 또는 하강시키면서 4개의 열 구조에 대해 온도분포와 온도구배를 측정 및 산출하였으며, 장단점을 비교하여 최적 성장조건을 확립하였다. LaSc3(BO3)4는 부조화 용융특성이 있으므로 화학양론적 조성에 La(BO3)를 다소 추가하여 특성 성분의 융액을 만들고, 인상속도를 0.7mm/hr이하, 회전속도는 7-10rpm의 환원조건 하에서 단결정을 성장시킬 수 있었다. 또한 결정성장때, Ir 및 백금 도가니를 사용할 수 있으나, 도가니의 수명은 가열/용융/냉각 주기가 최대 8-10회이다. 실험 결과 배플판 직경 등의 애프터 히타의 구조를 변화시킴으로써, 도가니 상부의 온도를 50-100℃ 증가시키는 것이 가능하였으며, 수직 및 수평적 온도구배는 배플판의 직경에 정비례하여 증감하였고, 특히 수평적 온도구배는 열구조에 의한 의존성이 크다는 것이 확인되었다.

• 한국산학기술학회:학술대회논문집
• /
• 한국산학기술학회 2012년도 춘계학술논문집 1부
• /
• pp.182-186
• /
• 2012

human tyrosinase (hTyr) catalyzes first and the rate limiting step in the synthesis of polymerized pigment, melanin which determines skin, hair and eye colors. Mutation of hTyr often brings about decrease of melanin production and further albinism. Meanwhile, a number of cosmetic companies providing skincare products for woman in Asia-Pacific region have tried to develop inhibitors to bright skin color for several decades. In this study, we built a 3D structure by comparative modeling technique based on the crystal structure of tyrosinase from bacillus megaterium as a template to serve structural information of hTyr. According to our model and sequence analysis of type 3 copper protein family proteins, two copper atoms of active site located deep inside are coordinated with six strictly conserved histidine residues coming from four-helix-bundle. Cavity which accommodates substrates was like funnel shape of which entrance was wide and expose to solvent. In addition, protein-substrate and protein-inhibitor complex were modeled with the guide of van der waals surface generated by in house software. Our model suggested that only phenol group or its analogs can fill the binding site near nuclear copper center because inside of binding site has narrow shape relatively. In conclusion, the results of this study may provide helpful information for designing and screening new anti-melanogensis agents.

• 한국음향학회지
• /
• 제6권4호
• /
• pp.5-11
• /
• 1987

본 연구에서는 압전 세라믹에서 탄성 표면파의 속도 측정에 대한 실험 방법을 제시한다. Oscilloscope와 Pulse Generator만으로 실시할 수 있으며 특히 feed-through에 의한 신호가 있는 경우에도 측정 가능한 방법이다. IDT응답이 Convolution 이론에 따르는 것에 주목하여 파가 진행한 거리를 정확히 산출하여 속도를 구할 수 있었다. 본 연구의 방법으로 측정한 결과 상온에서 $YZ-LiNbO_3$에 대하여 3,480m/sec를 구할 수 있었으며 feed-through가 큰 $PbTiO_3$계 압전 세라믹에 대해서는 2,770m/sec를 측정하였다.

• 한국전기전자재료학회논문지
• /
• 제11권4호
• /
• pp.274-280
• /
• 1998

Polycrystalline $Sr_2Nb_2O_7$ ceramics with very high Curie temperature were sintered using the powder derived by the chemical coprecipitation method (CCP). The phase evolution and grain-orientation of sintered samples were examined by XRD, while sintering behavior, dielectric properties and polarization were studied by SEM and ferroelectric tester. Extremely high degree of grain-orientation was observed along the (0k0) direction, which resulted in anisotropic dielectric properties of the sintered samples, with the dielectric constant values approaching those for single crystal. Thin film fabrication of $Sr_2Nb_2O_7$ in the pyroniobate family was also attempted on $SiO_2$/Si(100), Pt/$SiO_2$/Si(100), Pt/Ti/$SiO_2$/Si(100) and Pt/$ZrO_2/SiO_2/Si_2(100)$ substrates, using metalorganic decomposition (MOD) process. Neodecanoate precursor solution was prepared by mixing strontium neodecanoate with niobium neodecanoate synthesized from niobium ethoxide. It was found that $Sr_2Nb_2O_7$ single phase appeared in XRD patterns the samples annealed above $950^{\circ}C$. The effect of substrate type on film microstructure and dielectric properties was observed.

• Journal of Microbiology and Biotechnology
• /
• 제17권2호
• /
• pp.369-372
• /
• 2007

O-Methyltransferases (OMTs), one of the ubiquitous enzymes in plants, bacteria, and humans, catalyze a methyl-transfer reaction using S-adenosylmethionine and a wide range of phenolics as a methyl donor and acceptor, respectively. Substrates for most bacterial OMTs have largely remained elusive, but recent investigation using BcOMT2, an OMT from Bacillus cereus, suggested that ortho-dihydroxyflavonoids could serve as substrates. To elucidate the functional and structural features of BcOMT2, we expressed, and purified BcOMT2, and crystallized an apoenzyme and its ternary complex in the presence of a flavonoid and S-adenosylhomocysteine. Each crystal diffracted to $1.8{\AA}$ with its space group of C2 and $P2_{1}2_{1}2_{1}$, respectively. Structural analysis of apo-BcOMT2 and its ternary complex will provide the structural basis of methyl transfer onto (iso)flavonoids in a regiospecific manner.

• Journal of Preventive Medicine and Public Health
• /
• 제52권4호
• /
• pp.265-271
• /
• 2019

Objectives: The Samsung Ombudsperson Commission was launched as an independent third-party institution following an agreement among Samsung Electronics, Supporters for Health and Right of People in Semiconductor Industry (Banolim in Korean, an independent NGO), and the Family Compensation Committee, in accordance with the industry accident prevention measure required by the settlement committee to address the issues related to employees who allegedly died from leukemia and other diseases as a result of working at Samsung's semiconductor production facilities. Methods: The Commission has carried out a comprehensive range of activities to review and evaluate the status of the company's occupational accidents management system, as well as occupational safety and health risk management within its facilities. Results: Based on the results of this review, termed a comprehensive diagnosis, the Commission presented action plans for improvement to strengthen the company's existing safety and health management system and to effectively address uncertain risks in this area going forward. Conclusions: The Commission will monitor the execution of the suggested tasks and provide advice and guidance to ensure that Samsung's semiconductor and liquid crystal display production lines are safer.

• Bulletin of the Korean Chemical Society
• /
• 제33권8호
• /
• pp.2508-2512
• /
• 2012

Cold shock proteins (CSPs) are a family of proteins induced at low temperatures. CSPs bind to single-stranded nucleic acids through the ribonucleoprotein 1 and 2 (RNP 1 and 2) binding motifs. CSPs play an essential role in cold adaptation by regulating transcription and translation via molecular chaperones. The solution nuclear magnetic resonance (NMR) or X-ray crystal structures of several CSPs from various microorganisms have been determined, but structural characteristics of psychrophilic CSPs have not been studied. Therefore, we optimized the purification process to obtain highly pure Lm-Csp and determined the three-dimensional structure model of Lm-Csp by comparative homology modeling using MODELLER on the basis of the solution NMR structure of Bs-CspB. Lm-Csp consists of a ${\beta}$-barrel structure, which includes antiparallel ${\beta}$ strands (G4-N10, F15-I18, V26-H29, A46-D50, and P58-Q64). The template protein, Bs-CspB, shares a similar ${\beta}$ sheet structure and an identical chain fold to Lm-Csp. However, the sheets in Lm-Csp were much shorter than those of Bs-CspB. The Lm-Csp side chains, E2 and R20 form a salt bridge, thus, stabilizing the Lm-Csp structure. To evaluate the contribution of this ionic interaction as well as that of the hydrophobic patch on protein stability, we investigated the secondary structures of wild type and mutant protein (W8, F15, and R20) of Lm-Csp using circular dichroism (CD) spectroscopy. The results showed that solvent-exposed aromatic side chains as well as residues participating in ionic interactions are very important for structural stability. Further studies on the three-dimensional structure and dynamics of Lm-Csp using NMR spectroscopy are required.

• Bulletin of the Korean Chemical Society
• /
• 제32권6호
• /
• pp.2008-2014
• /
• 2011

Serotonin or 5-hydroxytryptamine subtype 2C ($5-HT_{2C}$) receptor belongs to class A amine subfamily of G-protein-coupled receptor (GPCR) super family and its ligands has therapeutic promise as anti-depressant and -obesity agents. So far, bovine rhodopsin from class A opsin subfamily was the mostly used X-ray crystal template to model this receptor. Here, we explained homology model using beta 2 adrenergic receptor (${\beta}$2AR), the model was energetically minimized and validated by flexible ligand docking with known agonists and antagonists. In the active site Asp134, Ser138 of transmembrane 3 (TM3), Arg195 of extracellular loop 2 (ECL2) and Tyr358 of TM7 were found as important residues to interact with agonists. In addition to these, V208 of ECL2 and N351 of TM7 was found to interact with antagonists. Several conserved residues including Trp324, Phe327 and Phe328 were also found to contribute hydrophobic interaction. The predicted ligand binding mode is in good agreement with published mutagenesis and homology model data. This new template derived homology model can be useful for further virtual screening based lead identification.

• Asian Pacific Journal of Cancer Prevention
• /
• 제17권4호
• /
• pp.2311-2314
• /
• 2016

Pistagremic acid (PA) is a bioactive triterpenoid isolated from various parts of Pistacia integerrima plants. The aim of this research was to investigate PA for reversion of multidrug resistant (MDR) mediated by P-glycoprotein using rhodamine-123 exclusion study on a multidrug resistant human ABCB1 (ATP-binding cassette, sub-family B, member 1) gene-transfected mouse T-lymphoma cell line in vitro. Results were similar to those with verapamil as a positive control. Docking studies of PA and standard Rhodamine123 were carried out against a P-gp crystal structure which showed satisfactory results. Actually, PA cannot bind exactly where co-crystallized ligand of P-gp is already present. However, the docking study predicted that if a compound gives a lesser score then it may have some potency. The docking scores of PA and Rhodamine were similar. Therefore, we can conclude that there are certain important chemical features of PA which are responsible for the inhibiting potency of P-gp.

• 한국인터넷방송통신학회논문지
• /
• 제15권6호
• /
• pp.147-154
• /
• 2015

최근 애자일 개발프로세스가 생산성 증대효과, 품질향상, 고객만족 등의 효용성이 입증되면서 프로젝트 추진 시 방법론 선택에 있어 전문가들에게 많은 관심을 갖게 되었다. 시대적 요구와 사용자 요구에 부응하기 위한 방법론 선정과 관련해서, 본 논문에서는 제품 기반의 Cross functional team의 문제점을 해결하고자 제안된 방법론이 Feature Team 모델이며, 이 모델이 Cross functional team을 조직하고, 이 팀이 결과물(프로덕트) 단위가 아니라, 기능단위로 여러 프로덕트에 걸쳐서 개발을 진행하는 모델이라는 점에 대해 조사하였으며, 가치-주도형 애자일 기법을 통해 계획-기반형 모델과 차이점을 제시하였다. Agile 성숙도 측정기준을 검토하였으며, PRINCE2 Agile Health-check 항목 연구를 통해 Agile 기법이 프로젝트 착수단계의 요구사항은 확정 본이 아닌 언제라도 변경될 수 있다는 것을 전제를 해서 객관적인 평가를 받는 방법에 대해 연구하고 프로젝트 팀 구성에 대해 향후 발전방향을 제시하였다.