• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1998년도 Proceedings of UNESCO-internetwork Cooperative Regional Seminar and Workshop on Bioassay Guided Isolation of Bioactive Substances from Natural Products and Microbial Products
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• pp.134-134
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• 1998

The modulation of glycosidase activity by inhibitors is of great interest. Such compounds have been shown to be important tools in mechanistic studies on glycohydrolase as well as having promising therapeutic application. An ${\alpha}$-glucosidase inhibitor was isolated from culture filterates of Penicillium sp. The inhibitor was active against ${\alpha}$-glucosidase isolated from yeast and porcine small intestine. However, it showed no inhibition to Aspergillus ${\alpha}$-galactosidase, Escherichia coli ${\beta}$-galactosidase, and jack bean ${\alpha}$-mannosidase. The inhibitor was highly soluble in ether, methanol and chloroform. The inhibitor was purified using silica gel, Sephadex LH-20 column chromatography and reverse-phase HPLC. The inhibitory compound designated PA-7(IC$\sub$50/=35$\mu\textrm{g}$) was obtained as white powder. The structure of PA-7 was determined with spectroscopic data of EI-MS, FAB-MS, $^1$H, and $\^$13/C NMR. The inhibitor has a diketopiperazine moiety.

• Journal of Pharmaceutical Investigation
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• 제20권3호
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• pp.135-144
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• 1990

The effects of bile salts (BS) on the stability of dioleoylphosphatidylethanolamine (DOPE) liposomes were investigated, observing apparent absorbance of vacant liposomes and calcein release from entrapped liposomes. Unilamellar liposomes were prepared by using a small quantity of palmitoly-immunoglobulin G(IgG) ($2.5{\times}10^{-4}$ mo1/lipid mol) to stabilize the bilayer phase of the unsaturated DOPE which by itself does not form stable liposomes. The destabilization of PE immunoliposomes by papain, clearly demonstrates that the IgG is essential for stabilization of PE bilayer. Approximately 4% of the entrapped calcein was released from the PE liposomes after 1 hr from liposome formation. Calcein release and absorbance of liposomes depended on the BS/lipid ratio because of the solubilization of lipid molecule in bilayer and the formation of mixed micelles. At very low BS concentrations, the incorporation of BS induced BS/lipid aggregates in the outer vesicles monolayer, while high BS concentrations, mixed micelles were formed. Chelate and its conjugates as $3{\alpha},\;7{\alpha},\;12{\alpha}-trihydroxy$ BS induce the concentration of the $3{\alpha}$, $12{\alpha}-dihydroxy$ BS at half-maximal solubilization of immunoliposomes to approximately 2.5-, or 5-fold. Conjugation of BS with glycine or taurine slightly enhanced their capacities to perturb membranes.

• 대한수의학회지
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• 제35권3호
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• pp.447-458
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• 1995

This study was carried out to characterize nonadrenergic, noncholinergic(NANC) relaxation of porcine retractor penis(PRP) muscle induced by electrical field stimulation(EFS) and to investigate the actions of niric oxide(NO) and vasoactive intestinal polypeptide(VIP) as candidates for NANC neurotransmitters. Biphasic relaxations of PRP muscle were induced by EFS to NANC nerve. Rapid-phase relaxation was observed at low frequency(0.5-16Hz) and slow-phase relaxation followed during high frequency(8-60Hz). Both relaxations were frequency-dependent and TTX($1{\times}10^{-6}M$)-sensitive. L-NAME($2{\times}10^{-5}M$) inhibited the rapid-phase relaxation, but not the slow-phase relaxation. The inhibition of the rapid-phase relaxation with L-NAME was reversed by L-arginine ($1{\times}10^{-3}M$) but not by D-arginine($1{\times}10^{-3}M$). Methylene blue($4{\times}10^{-5}M$) reduced the rapid-phase relaxation. Exogenous No(ExoNO, $1{\times}10^{-5}-1{\times}10^{-4}M$) induced dose-dependent relaxations of PRP muscle. Oxyhemoglobin($5{\times}1^{-5}M$) blocked the relaxation induced by ExoNO and inhibited EFS-induced relaxation. Hydroquinone($1{\times}10^{-4}M$) also abolished the relaxation induced by ExoNO, but did not affect EFS-induced relaxation. L-NAME resistant slow-phase relaxation to EFS was inhibited by ${\alpha}$-chymotrypsin(2.5 U/ml). Both methylene blue($4{\times}10^{-5}M$) and Nethylmaleimide($1{\times}10^{-4}M$) reduced the slow-phase relaxation by EFS. [4-Cl-D-$Phe^6$, $Leu^{17}$]-VIP($3{\times}10^{-6}M$) inhibited the slow-phase relaxation by EFS. External applications of VIP ($1{\times}10^{-7}M$) caused relaxations that were simillar to the L-NAME resistant slow-phase relaxations induced by EFS, and relaxant effects of exogenous VIP were blocked by ${\alpha}$-chymotrypsin(2.5 U/ml).

• 한국미생물·생명공학회지
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• 제17권5호
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• pp.412-420
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• 1989

Bacillus amyloliquefaciens의 extracellular $\alpha$-amylase는 세포질막에 결합된 ribosome에서 합성되며 이 때 ribosome은 nascent polypeptide쇄에 의해 막에 부착된 것으로 추측된다. $\alpha$-amylase 생산균주인 E. amyioiiquefaciens 야생주의 정상단백(MW, 58kDa)과 이 균주의 $\alpha$-amylase 구조유전자에 변이가 일어나 carboxy 말단이 결실된 변이주의 이상단백 (33kDa)은 동일조건하의 배양외액에서 그 효소활성이 검출됨을 볼 때, $\alpha$-amylase의 carboxy 말단에는 막 투과의 신호가 없는 것으로 생각된다. 그러나 이들 양균주의 대수증식기 세포에 puromycin을 20$\mu\textrm{g}$/$m\ell$까지 가하여 6시간 동안 처리한 결과 균의 사멸에는 영향을 미치지 않았으나 extracellular $\alpha$-amylase 활성은 10$\mu\textrm{g}$/$m\ell$의 농도에서도 동일양상으로 감소하였다. 이 감소요인은 puromycin 처리시 막결합 ribosome에서의 막과 ribosome의 가교로 작용할 것으로 예상되는 nascent poly peptide 합성이 중단되므로 막으로부터 ribosome이 해리되어 $\alpha$-amylase의 분비가 억제된 것으로 추측된다. 이 현상은 50mM의 magnesium의 첨가효과 가 약하게 나타났기 때문에 ribosome은 nascent Polypeptide의 가교로 막에 부착되어 있는 것으로 생각된다. 또 Iysozyme 처리에 의해 세포벽을 분해한 protoplas가 trypsin을 함께 처리하므로서 세포외액의 $\alpha$-amylase 활성이 상실됨은 막의 외부로 protruding되는 nascent polypeptide가 trypsin에 의해 분해되기 때문으로 생각된다. 3차 구조를 형성한 extracellular $\alpha$-amylase의 경우 trypsin 내성임을 감안할 때 이 분자가 세포막 통과 직후, 세포벽을 통과하기 이전에 folding이 이루어져서 그 후 성숙된 단백으로서 세포벽을 통과하는 것으로 믿어진다.

• 열처리공학회지
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• 제27권3호
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• pp.115-120
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• 2014

Microstructural features were comparatively investigated in AZ91 (Mg-9%Al-1%Zn) and AZ91-0.5%Sn alloys, in order to clarify the reason for the enhancement in room temperature tensile properties by the addition of small amount of Sn in Mg-Al-based alloy. In as-cast state, the Sn-containing alloy showed increased YS, UTS and elongation than the Sn-free alloy. The microstructural examination revealed that various factors including finer cell size, reduction of lamellar (${\alpha}+{\beta}$) phase and morphological change of bulky ${\beta}$ phase from partially divorced shape to fully divorced shape, are likely to be responsible for the improvement in tensile properties for the Sn-containing alloy. It is noted that two alloys showed similar tensile properties after solution treatment. This implies that microstructural evolution related to the ${\beta}$ phase plays a key role in better tensile properties in the Sn-containing alloy.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권3호
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• pp.264-271
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• 2014

Virtual synchronous generator (VSG) in single-phase to interface distributed renewable energy resources is investigated in this paper. Mathematical models and numerical analysis are utilized to illustrate the features of the VSG. Enhanced control strategy is presented to ensure the performance of the VSG. Besides, a second order generalized integer (SOGI) is employed to calculate the instantaneous output power of the VSG in virtual ${\alpha}{\beta}$ frame. By the means of a phase-locked loop based scheme, the VSG can seamlessly transform between islanded and grid-tied modes, which can meet the requirements of micro-grid. At last, the validation and the proposed approach are verified by the simulated results using PSCAD/EMTDC.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.482-483
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• 2006

Synthesis of iron nanopowder by room-temperature electrochemical reduction process of ${\alpha}-Fe_2O_3$ nanopowder was investigated in terms of phase evolution and microstructure. As process variables, reduction time and applied voltage were changed in the range of $1{\sim}20$ h and $30{\sim}40$ V, respectively. From XRD analyses, it was found that volume of Fe phase increased with increasing reduction time and applied voltage, respectively. The crystallite size of Fe phase in all powder samples was less than 30 nm, implying that particle growth was inhibited by the reaction at room temperature. Based on the distinct equilibrium shape of crystalline particle, phase composition of nanoparticles was identified by TEM observation.

• 한국결정성장학회지
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• 제28권3호
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• pp.135-139
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• 2018

본 연구에서는 HVPE 성장법을 이용하여 사파이어 기판 위에 알파 갈륨옥사이드를 성장시키며 VI/III 비의 변화에 따른 효과를 확인하였다. 성장된 알파 갈륨옥사이드의 표면은 평평하고 crack 없이 성장되었다. 성장된 갈륨옥사이드의 광학적 특성을 분석하기 위해 투과율을 측정하고 광학 밴드갭을 얻었다. 광학 밴드갭은 약 5.0 eV로 나타났고 VI/III 비가 증가함에 따라 비례하여 증가하는 결과를 보여주었다. 이론적 광학 밴드갭에 가장 근접한 VI/III 비가 23인 조건에서 성장된 알파 갈륨옥사이드의 결정성을 확인하기 위해 HR-XRD를 이용하여 FWHM을 측정하였고 이를 바탕으로 전위밀도를 계산하였을 때 나선형 전위밀도는 $1.5{\times}10^7cm^{-2}$, 칼날 전위 밀도는 $5.4{\times}10^9cm^{-2}$로 계산되었다.

• 한국전기전자재료학회논문지
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• 제32권5호
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• pp.426-431
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• 2019

In this study, we report the effect of pre-treatment of alpha-$Ga_2O_3$ grown on a sapphire substrate by halide vapor phase epitaxy (HVPE). During the pre-treatment process, 10 sccm of GaCl gas was injected to the sapphire substrate at $470^{\circ}C$. The surface morphologies of the alpha-$Ga_2O_3$ layers grown with various pre-treatment time (3, 5, and 10 min) were flat and crack-free. The transmittance of the alpha-$Ga_2O_3$ epi-layers was measured to analyze their optical properties. The transmittance was over 80% within the range of visible light. The strain in the alpha-$Ga_2O_3$ grown with a pre-treat 5 min was measured, and was found to be close to the theoretical XRD peak position. This can be explained by the reduction of strain having caused a lattice mismatch between the alpha-$Ga_2O_3$ layer and sapphire substrate. The calculated dislocation density of the screw and edge were $2.5{\times}10^5cm^{-2}$ and $8.8{\times}10^9cm^{-2}$, respectively.

• 한국축산식품학회지
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• 제28권5호
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• pp.637-644
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• 2008

식품 중 HCAs을 검출하기 위한 최적 전처리 방법을 확립하기 위해 가열 조리된 돼지고기 패티를 이용하여 서로 다른 4가지 SPE(solid-phase extraction)방법을 비교하였다. 4가지 전처리 방법을 통해 얻은 15가지 HCAs 회수율은 3.0%(방법 A, Tri-P-1)-74.7%(방법A, Tri-P-2)이었다. 그 중 $MeA{\alpha}C$가 평균적으로 73.4%로 가장 높은 회수율을 보였으며 Tri-MeIQx가 15.2%의 가장 낮은 회수율을 보였다. 4가지 전처리 방법 중 방법A와 방법D가 가장 높은 회수율과 검출빈도를 보였으며 방법B와 방법C는 Harman(14.8%)을 제외하고는 전혀 검출되지 않았고 회수율을 구할 수 없었다 발암 가능 물질인 IQ, $A{\alpha}C$, $MeA{\alpha}C$, Glu-P-1, Glu-P-2, MeIQ, MeIQx, PhIP 등을 검출하는 방법에는 방법A(48.7-74.6%)가 4가지 방법 중 가장 유리하다. HCAs는 극성에 따라 polar amines과 less-polar amines으로 구분할 수 있는데 방법A는 less-polar amines검출에 유리하고 방법D는 polar amines검출에 유리하다. 방법A와 방법D의 chromatogram을 비교한 결과 방법A와 방법D 모두 15가지 HCAs가 깨끗하게 분리되었지만 Tri-MeIQx 등을 검출하는데 방법A가 더욱 유리하다. SPE 전처리 방법 및 LC/MS 분석방법에 대한 유효성을 확인하기 위해 LOD(0.2-2.1 ng/mL)와 LOQ(0.8-9.7 ng/mL), 표준 편차(0.2-8.6)를 구하였다.