Cu 기판위에 성장한 MgO, MgAl₂O₄와 MgAl₂O₄/MgO 박막의 집속이온빔을 이용한 스퍼터링수율 측정과 이차전자방출계수 측정

정강원(K. W. Jung),이혜정(H. J. Lee),정원희(W. H. Jung),오현주(H. J. Oh),박철우(C. W. Park),최은하(E. H. Choi),서윤호(Y. H. Seo),강승언(S. O. Kang) 한국진공학회(ASCT) 2006 Applied Science and Convergence Technology Vol.15 No.4

MgAl₂O₄ 막은 MgO 보호막 보다 단단하며 수분 흡착 오염문제에 상당히 강한 특성을 가진다. 본 연구에서 AC-PDP의 유전체보호막으로 사용되는 MgO 보호막의 특성을 개선하기 위해 MgAl₂O₄/MgO 이중층 보호막을 제작하여 특성을 조사하였다. 전자빔 증착기를 사용하여 Cu 기판에 MgO와 MgAl₂O₄을 각각 1000 Å 두께로 증착, MgAl₂O₄/MgO을 200/800 Å 두께로 적층 증착 후, 이온빔에 의한 충전현상을 제거하기 위해 Al을 1000 Å 두께로 증착하였다. 집속 이온빔(focused ion beam ; FIB)장치를 이용하여 10 ㎸에서 14 ㎸까지 이온빔 에너지에 따라 MgO는 0.364 ~ 0.449 값의 스퍼터링 수율에서 MgAl₂O₄/MgO을 적층함으로 24 ~ 30 % 낮아진 0.244 ~ 0.357 값의 스퍼터링 수율이 측정되었으며, MgAl₂O₄는 가장 낮은 0.088 ~ 0.109 값의 스퍼터링 수율이 측정되었다. g-집속이온빔(g-FIB)장치를 이용하여 Ne? 이온 에너지를 50 V에서 200 V까지 변화 시켜 MgAl₂O₄/MgO와 MgO는 0.09 ~ 0.12의 비슷한 이차전자방출 계수를 측정 하였다. AC-PDP셀의 72시간 열화실험 후 SEM 및 AFM으로 열화된 보호막의 표면을 관찰하여 기존의 단일 MgO 보호막과 MgAl₂O₄/MgO의 적층보호막의 열화특성을 살펴보았다. It is known that MgAl₂O₄ has higher resistance to moisture than MgO, in humid ambient MgO is chemically unstable. It reacts very easily with moisture in the air. In this study, the characteristic of MgAl₂O₄ and MgAl₂O₄/MgO layers as dielectric protection layers for AC-PDP (Plasma Display Panel) have been investigated and analysed in comparison for conventional MgO layers. MgO and MgAl₂O₄ films both with a thickness of 1000 Å and MgAl₂O₄/MgO film with a thickness of 200/800 Å were grown on the Cu substrates using the electron beam evaporation. 1000 Å thick aluminium layers were deposited on the protective layes in order to avoid the charging effect of Ga? ion beam while the focused ion beam(FIB)is being used. We obtained sputtering yieds for the MgO, MgAl₂O₄ and MgAl₂O₄/MgO films using the FIB system. MgAl₂O₄/MgO protective layers have been found th show 24 ~ 30% lower sputtering yield values from 0.244 up to 0.357 than MgO layers with the values from 0.364 up to 0.449 for irradiated Ga? ion beam with energies ranged from 10 ㎸ to 14 ㎸. And MgAl₂O₄ layers have been found to show lowest sputtering yield values from 0.88 up to 0.109. Secondary electron emission coefficient(g) using the γ-FIB. MgAl₂O₄/MgO and MgO have been found to have similar g values from 0.09 up to 0.12 for indicated Ne+ ion with energies ranged from 50 V to 200 V. Observed images for the surfaces of MgO and MgAl₂O₄/MgO protective layers, after discharge degradation process for 72 hours by SEM and AFM. It is found that MgAl₂O₄/MgO protective layer has superior hardness and degradation resistance properties to MgO protective layer.

How do extreme wet events affect rice quality in a changing climate?

Lee, M.S.,Kang, B.M.,Lee, J.E.,Choi, W.J.,Ko, J.,Choi, J.E.,An, K.N.,Kwon, O.D.,Park, H.G.,Shin, H.R.,Lee, I.,Kim, J.K.,Kim, H.Y. Elsevier 2013 Agriculture, ecosystems & environment Vol.171 No.-

Despite the growing body of evidence that ongoing warming modifies the cereal quality of several crop species, little is known about how it interacts with other climate change drivers. Here, we examined how elevated [CO<SUB>2</SUB>], warming, and extreme wet events (EWEs) would affect the grain quality of a temperate rice (Oryza sativa L.). In 2009 and 2010, plants were grown at two levels of [CO<SUB>2</SUB>] (c. 390 and 650μll<SUP>-1</SUP>) and three levels of warming (ambient, +1.2<SUP>o</SUP>C and +2.2/2.4<SUP>o</SUP>C) over the seasons in six independent temperature gradient field chambers (three each for ambient and elevated [CO<SUB>2</SUB>]). From 20 days after heading, plants were exposed to EWE with a simulated rainfall of 30mm a day and cloud cover by shading (c. 18% of full sunlight) for 10 consecutive days. There were also control plots, which were non-treated (NT) in terms of EWE. We found that warming and EWE, both independently and in their interaction, lead to a significant reduction in the percentages of sound grains, whereas elevated [CO<SUB>2</SUB>] does not seem to do so. Not only warming and EWE, but also elevated [CO<SUB>2</SUB>] resulted in a significant increase of immature chalky grains (ICGs), which mostly consisted of milky-white chalky grains, degrading the grain quality. In addition, warming interacted positively with elevated [CO<SUB>2</SUB>] on ICGs, whereas the warming sensitivity of IGCs was moderated in EWEs: e.g., on average, the % of ICGs in ambient vs. elevated [CO<SUB>2</SUB>] were 8.5% vs. 9.4%, 10.7% vs. 18.1% and 17.8% vs. 29.8% at ambient (24.7<SUP>o</SUP>C), +1.2<SUP>o</SUP>C and +2.4<SUP>o</SUP>C, respectively, whereas they in NT vs. EWE were 1.2% vs. 16.6%, 7.7% vs. 21.1% and 19.4% vs. 28.2%. Our results tightly confirmed that elevated [CO<SUB>2</SUB>] leads to a significant reduction in rice grain protein content (PC). While warming had little effect on the PC, EWE had a significant positive effect, and the EWE-induced increase in PC was smaller in elevated (+3.3%) than in ambient [CO<SUB>2</SUB>] (+10.9%). Given the rice quality predictor of ICGs and PC, our findings imply that expected climate change and weather extremes have a great potential to degrade the quality of rice, in terms of its milling, cooking, eating, and nutritional quality, as well as market value.

Magnetic resonance imaging of macrophage activity in atherosclerotic plaques of apolipoprotein E-deficient mice by using polyethylene glycolated magnetic fluorescent silica-coated nanoparticles

Lee, K.,Moon, H.Y.,Park, C.,Kim, O.R.,Ahn, E.,Lee, S.Y.,Park, H.E.,Ihm, S.H.,Seung, K.B.,Chang, K.,Yoon, T.J.,Lee, C.,Cheong, C.,Hong, K.S. Elsevier 2009 Current Applied Physics Vol.9 No.1

We have recently synthesized organic dye-incorporated silica-coated core-shell magnetic nanoparticles (MFSNs) that enable the detection of both fluorescence and magnetic properties in cells and tissues by using magnetic resonance imaging (MRI). Furthermore, polyethylene glycolation of the surface of these MFSNs would render them more stable and biocompatible, and thus allow their in vivo use as a circulating agent with a long half-life. Atherosclerotic vascular diseases are the leading cause of death worldwide. A noninvasive diagnostic imaging method is required to identify vulnerable plaques prior to the occurrence of a clinical event. Macrophages are the key cellular mediators in the pathogenesis of plaque inflammation and vulnerability. We evaluated whether the use of polyethylene glycolated (PEGylated) MFSNs could help in effectively detecting the macrophage activity in the aorta of apolipoprotein E (apoE)-deficient mice. PEGylated MFSNs (Fe, 30mg/kg) were injected via the tail vein in 1.2% cholesterol-fed 30-week-old apoE-deficient mice. After 24h, ex vivo MRI was carried out. The atheromas were then observed by confocal laser scanning microscopy (CLSM), and immunohistochemical staining targeted toward the macrophages was performed. Ex vivo MRI demonstrated robust enhancement of the atherosclerotic plaques along the aortic wall. CLSM images showed accumulation of PEGylated MFSNs in the atherosclerotic plaques, and histological examination revealed the localization of MFSNs in the macrophages present in the lesion. Therefore, PEGylated MFSNs could function as an effective multimodal imaging agent in the identification of macrophage activity in atherosclerotic plaques.

Efficient proteolytic cleavage by insertion of oligopeptide linkers and its application to production of recombinant human interleukin-6 in Escherichia coli

Lee, E.G.,Baek, J.E.,Lee, S.H.,Kim, T.W.,Choi, J.H.,Rho, M.C.,Ahn, J.O.,Lee, H.W.,Jung, J.K. IPC Science and Technology Press ; Elsevier Scienc 2009 Enzyme and microbial technology Vol.44 No.5

Efficient expression and purification of bioactive recombinant human interleukin-6 (hIL6) was successfully achieved in Escherichia coli (E. coli) by fusion of the maltose-binding protein (MBP) with hIL6 and the insertion of oligopeptide linkers. MBP/hIL6 was over-expressed in the soluble form at a concentration of approximately 2.5g/L. For hIL6 recovery, enterokinase, factor Xa, and thrombin were employed to cleavage MBP from the fusion constructs. However, undesired and non-specific cleavage fragments as well as rhIL6 were obtained following the cleavage. The introduction of oligopeptide linkers at the C-terminal end of the fusion construct could improve the efficiency and the rate of the enzymatic cleavage reaction, and the rhIL6 purification was achieved by using MBP affinity chromatography, factor Xa cleavage, and reverse-phase chromatography, resulting in an overall yield as high as 33% (equivalent to 0.27ghIL6/L) at purity over 98%. The biological activity of the purified recombinant hIL6 was demonstrated by confirming the presence of the signal transducer and activator of transcription 3 (STAT3) signaling pathway. This study suggests that the optimized peptide linker specifically designed for both fusion partner and target molecule has a great potential for efficient recombinant protein production.

An albumin nanocomplex-based endosomal pH-activatable on/off probe system

Lee, C.,Lee, S.,Thao, L.Q.,Hwang, H.S.,Kim, J.O.,Lee, E.S.,Oh, K.T.,Shin, B.S.,Choi, H.G.,Youn, Y.S. Elsevier 2016 Colloids and Surfaces B Vol.144 No.-

<P>Albumin has gained considerable interest as a material for fabricating nanoparticulate systems due to its biomedical advantages, such as biocompatibility and chemical functionality. Here, we report a new pH-sensitive albumin nanocomplex prototype with a zinc-imidazole coordination bond. Albumin was conjugated with 1-(3-aminopropyl)imidazole and mPEG(10kDa)-NHS, and the resulting albumin conjugate (PBI) was then modified with either Cy5.5 or BHQ-3. The newly formed albumin nanocomplex (C/BQ-PBI Zn NCs: similar to 116 nm) system was facilely self-assembled around pH 7.4 in the presence of Zn2+, but it quickly disassembled in an acidic environment (similar to pH 5.0). Based on this pH-sensitivity, C/BQ-PBI Zn NCs emitted strong near-infrared fluorescence and released Zn2+, turning 'off' at pH similar to 7.4 (e.g., plasma) and 'on' at pH similar to 5.0 (e.g., endo/lysosomes in tumor cells) on account of fluorescence resonance energy transfer. C/BQ-PBI Zn NCs displayed significant cytotoxicity due to an increase in cellular. Zn2+ in response to endosomal pH (similar to 5.0) in breast cancer MCF-7 cells and lung adenocarcinoma A549 cells. Particularly, confocal laser scanning microscopic images showed a strong fluorescence signal caused by the disassembly of C/BQ-PBI Zn NCs in the endosomal region of MCF-7 cells. Based on these results, we believe that this albumin nanocomplex is an attractive biocompatible tumor targeting probe carrier for the theranostic purpose. (C) 2016 Elsevier B.V. All rights reserved.</P>

Owner-Borrower Model for Recommenders in O2O Services

Lee, O-Joun,Jung, Jai E. Springer-Verlag 2018 MOBILE NETWORKS AND APPLICATIONS Vol.23 No.4

Development of Escherichia coli MG1655 strains to produce long chain fatty acids by engineering fatty acid synthesis (FAS) metabolism

Jeon, E.,Lee, S.,Won, J.I.,Han, S.O.,Kim, J.,Lee, J. IPC Science and Technology Press ; Elsevier Scienc 2011 Enzyme and microbial technology Vol.49 No.1

The goal of this research was to develop recombinant Escherichia coli to improve fatty acid synthesis (FAS). Genes encoding acetyl-CoA carboxylase (accA, accB, accC), malonyl-CoA-[acyl-carrier-protein] transacylase (fabD), and acyl-acyl carrier protein thioesterase (EC 3.1.2.14 gene), which are all enzymes that catalyze key steps in the synthesis of fatty acids, were cloned and over-expressed in E. coli MG1655. The acetyl-CoA carboxylase (ACC) enzyme catalyzes the addition of CO<SUB>2</SUB> to acetyl-CoA to generate malonyl-CoA. The enzyme encoded by the fabD gene converts malonyl-CoA to malonyl-[acp], and the EC 3.1.2.14 gene converts fatty acyl-ACP chains to long chain fatty acids. All the genes except for the EC 3.1.2.14 gene were homologous to E. coli genes and were used to improve the enzymatic activities to over-express components of the FAS pathway through metabolic engineering. All recombinant E. coli MG1655 strains containing various gene combinations were developed using the pTrc99A expression vector. To observe changes in metabolism, the in vitro metabolites and fatty acids produced by the recombinants were analyzed. The fatty acids (C16) from recombinant strains were produced 1.23-2.41 times higher than that from the wild type.

Disulfonated poly(arylene ether sulfone) random copolymer thin film composite membrane fabricated using a benign solvent for reverse osmosis applications

Lee, C.H.,McCloskey, B.D.,Cook, J.,Lane, O.,Xie, W.,Freeman, B.D.,Lee, Y.M.,McGrath, J.E. Elsevier Scientific Pub. Co 2012 Journal of membrane science Vol.389 No.-

High performance thin film composite (TFC) membranes for reverse osmosis applications were fabricated by coating solutions of highly chlorine-tolerant disulfonated directly copolymerized poly(arylene ether sulfone) random copolymers (BPS-XX, e.g., BPS-20 and 32) on a commercially available porous polysulfone (e.g., Udel<SUP>(</SUP>R)) support. Solvents used in the formation of the TFCs must dissolve the sulfonated polysulfones used as the skin materials, while not harming the non-sulfonated polysulfone support membrane. For this purpose, environmentally friendly solvents were selected via a systematic screening process using a triangular solubility diagram. However, these benign solvents [e.g., di(ethylene glycol)] generally have high boiling points (>∼190<SUP>o</SUP>C). Thus, they necessitate the use of a special TFC formation process, since solvent evaporation at high temperatures caused pore shrinkage in the polysulfone support membrane and could lead to a catastrophic decrease in membrane water permeance. Support membranes were initially immersed in an IPA/glycerin mixture, after which the IPA was allowed to evaporate, leaving glycerin within the membrane pore structure. After a repeated coating procedure using dilute BPS-XX solutions, the TFC membranes were dried under vacuum at elevated temperatures. During this process, the glycerin reduced pore penetration of BPS-XX and prevented pore collapse during the drying procedures. Finally, water-miscible glycerin was eliminated via water treatment. The newly developed coating method formed ultra-thin and defect-free BPS-XX layers on a micro-porous Udel<SUP>(</SUP>R) support membrane. For example, BPS-32 TFC membranes showed NaCl rejection (∼97%), similar to that of its dense membranes. Furthermore, decreasing the amount of coating solution and, therefore, the BPS-32 coating thickness, resulted in improved pure water flux. The TFC water flux was further improved and was accompanied by small reduction in salt rejection after various TFC membrane treatments (e.g., in situ acidification or IPA treatment).

JBR(Jeju Island Bovine Rotavirus)의 Sequencing에 의한 Homology 비교에 관한 연구

이종익,谷口孝喜,김응률,류영수,박선오,송진욱,유제현,조홍찬,차광종,浦澤正三,이태협,김유성,이영건 건국대학교 동물자원연구센터 1998 動物資源硏究誌 Vol.19 No.-

본 연구는 PCR에 의해 로타바이러스의 serotype을 결정하고 염기배열의 유사성을 다른 지역에서 발견된 로타바이러스와 비교 분석하였으며 그 결과는 다음과 같다. 1. 제주도 목장에서 송아지 설사변을 채취하여 로타바이러스를 분리 후 MA104세포에 감염시켜 세포변성 효과(CPE)를 확인하였다. 2. 전자현미경에 의해 형태학적로 로타바이러스임이 판명되었으며 형광항체법에 의해 MA104세포에 감염된 것을 재확인 하였다. 3. 제주도 송아지 로타바이러스(JBR)RNA를 PAGE에 의해 genotype를 분석한 결과 bovine특유의 4:2:3:2 pattern이지만 일반 PAGE로 분석한 결과는 NCDV, UK, KK3, A5-37, 61A, B223와 차이가 있었으며, Ns-5, Nc-5, Kawatabi(Japan)와는 비슷한 경향을 보였다. 4. Plaquing 후 titer한 결과 NCDV, UK보다는 낮은 ??PFU/ml이었다. 5. RNA-RAN hybridization과 ELISA 및 VP7과 VP4의 1차, 2차 PCR 사물을 1% agarose(EtBr 1㎕의 TAE)에서 전기영동한 결과 G6P11의 serotype이었다. 6. JBR의 P serotype이 동일하게 나타난 B223과의 비교 결과 총 JVP8 750 bases 중에서 731개의 염기가 B223과 같은 것으로 나타나 염기배열의 유사성은 97.47%로 나타났고, 아미노산 배열의 유사성은 97.57%로 나타났다. This study was carried our to identify JBR's serotype by polymerase chain reaction(PCR) and to analyze homology of JBR' sequence. The results obtained in these experiments were as follows: 1. Fecal samples of calf diarrhea were taken on farms in Jeju island, rotavirus was isolated and cytopathic effect(CPE) was determined after infection to MA104 cell. 2. Morphological evaluation on electron microscopy proved it as rotavirus. Also, its infection to MA104 cell was reidentified using a fluorescence antibody method. 3. Genotype of Jeju island bovine rotavirus(JBR) analyzed thorough PAGE was 4:2:3:2 pattern, which was unique in bovine and that analyzed through general PAGE was somewhat different from NCDV, UK, KK3, A5-37, 61A, B223 and similar to Nstool-5, N cultrue-5 and Kawatabi(Japan). 4. By titration after plaquing, the level was ??PEU/ml, which was lower than those of NCDV and UK. 5. Electrophoresis analysis of RNA-RNA hybridization. ELISA, adn first and second PCR products of VP7 and VP4 in 1% agarose(TAE+1㎕ EtBr) revealed that the rotavirus was a serotype of G6P11. 6. Alignment of two(JBR and B223) amino acid sequences is 97.57% and nucleotide sequences is 97.47%.

한국의 HIV-1 감염의 분자역학

이주실,김은영,남정구,기미경,최병선,김성순,강춘,구본기,신영오 국립보건연구원 1998 국립보건원보 Vol.35 No.-