• Journal of Astronomy and Space Sciences
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• 제23권2호
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• pp.117-126
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• 2006

지상에서 우주선 측정기(NM, Neutron Monitor)로 관측되는 우주선 세기의 일변화는 일평균 값의 $1{\sim}2%$ 정도의 진폭을 갖는 사인곡선의 형태를 보인다. 본 연구는 NM 관측소에서 우주선 일변화의 최대 및 최소 세기가 관측되는 지방시 변화의 통계적 경향 분석을 수행하였다. 우주선 일변화 최대 및 최소 세기 시각의 분포에 영향을 주는 우주선 중성자 관측소의 위치(cut-off rigidity)와 태양활동도의 영향을 분석해 보기 위해서 저위도 지방의 Haleakala(위도: 20.72N, cut-off rigidity: 12.91Gev)와 고위도 지방의 Oulu(위도: 65.05N, cut-off rigidity: 0.81Gev) 우주선 중성자 관측소의 1996년(태양활동 극소기) 및 2000년(태양활동 극대기) 우주선 관측 자료를 분석하였다. 태양활동 극대기의 우주선 일변화 최대 및 최소 세기 시각은 태양활동 극소기에 비해 약 $2{\sim}3$시간 정도 늦은 시각에 나타난다. 우주선 중성자 관측소의 위치 즉 위도별 분포(rigidity의 크기)에 따른 영향을 살펴보면, cut-off. rigidity가 Haleakala보다 작은 Oulu에서 우주선 일변화 최대 및 최소 세기 시각이 약 $2{\sim}3$시간 정도 늦게 나타나며, 이러한 현상은 극대기에 더욱 뚜렷하게 나타났다. 태양활동에 따른 행성간 자기장 세기의 변화와 위도에 따른 cut-off rigidity의 크기에 따라 우주선 세기 일변화 위상이 결정된다고 볼 수 있다.

• Journal of Applied Biological Chemistry
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• 제54권1호
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• pp.63-66
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• 2011

The bark of Machilus thunbergii was extracted with 80% aqueous methanol (MeOH), and the concentrated extract was partitioned using ethyl acetate (EtOAc), butanol (n-BuOH), and $H_2O$, successively. From the EtOAc fraction, five lignans were isolated through the repeated silica gel, octadecyl silica gel (ODS) and, Sephadex LH-20 column chromatography. Based on nuclear magnetic resonance (NMR), mass spectroscopy (MS), and infrared spectroscopy (IR) spectroscopic data, the chemical structures of the compounds were determined to be machilin A (1), machilin F (2), licarin A (3), nectandrin A (4), and nectandrin B, (5). This study presents comparative account of five lignans from M. thunbergii bark contributing inhibition of low density lipoprotein (LDL), ACAT-1, and ACAT-2. Compounds 2-5 showed varied degree of antioxidant activity on LDL with $IC_{50}$ values of 2.1, 11.8, 15.3, and $4.1{\mu}M$. Compounds 1, 2, and 3 showed inhibition activity on ACAT-1 with values $63.4{\pm}6.9%$ ($IC_{50}=66.8{\mu}M$), $53.7{\pm}0.9%$ ($IC_{50}=109.2{\mu}M$), and $78.7{\pm}0.2%$ ($IC_{50}=40.6{\mu}M$), respectively, at a concentration of 50 mg/mL, and on ACAT-2 with values $47.3{\pm}1.5%$ ($IC_{50}=149.7{\mu}M$), $39.2{\pm}0.2%$ ($IC_{50}=165.2{\mu}M$), and $52.1{\pm}1.0%$ ($IC_{50}=131.0{\mu}M$, respectively, at a concentration of 50 mg/mL.

• Molecules and Cells
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• 제38권5호
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• pp.409-415
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• 2015

Low-barrier hydrogen bonds (LBHBs) have been proposed to have important influences on the enormous reaction rate increases achieved by many enzymes. ${\Delta}^5$-3-ketosteroi isomerase (KSI) catalyzes the allylic isomerization of ${\Delta}^5$-3-ketosteroid to its conjugated ${\Delta}^4$-isomers at a rate that approache the diffusion limit. Tyr14, a catalytic residue of KSI, has been hypothesized to form an LBHB with the oxyanion of a dienolate steroid intermediate generated during the catalysis. The unusual chemical shift of a proton at 16.8 ppm in the nuclear magnetic resonance spectrum has been attributed to an LBHB between Tyr14 $O{\eta}$ and C3-O of equilenin an intermediate analogue, in the active site of D38N KSI. This shift in the spectrum was not observed in Y30F/Y55F/D38N and Y30F/Y55F/Y115F/D38N mutant KSIs when each mutant was complexed with equilenin, suggesting that Tyr14 could not form LBHB with the intermediate analogue in these mutant KSIs. The crystal structure of Y30F/Y55F/Y115F/D38N-equilenin complex revealed that the distance between Tyr14 $O{\eta}$ and C3-O of the bound steroi was within a direct hydrogen bond. The conversion of LBHB to an ordinary hydrogen bond in the mutant KSI reduced the binding affinity for the steroid inhibitors by a factor of 8.1-11. In addition, the absence of LBHB reduced the catalytic activity by only a factor of 1.7-2. These results suggest that the amount of stabilization energy of the reaction intermediate provided by LBHB is small compared with that provided by an ordinary hydrogen bond in KSI.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1997년도 춘계학술대회
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• pp.86-86
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• 1997

Human annexin I is a member of annexin family of calcium dependent phospholipid binding proteins, which have been implicated in various physiological roles including phospholipase A$_2$ (PLA$_2$) inhibition, membrane fusion and calcium channel activity. In this work, the structure of N-terminally truncated human annexin I (Δ-annexin I) and its interactions with Ca$\^$2+/, ATP and cAMP were studied at atomic level by using $^1$H, $\^$15/N, $\^$l3/C NMR (nuclear magnetic resonance) spectroscopy. The effect of Ca$\^$2+/ binding on the structure of Δ-annexin I was investigated, and compared with that of Mg$\^$2+/ binding. The addition of Ca$\^$2+/ to Δ-annexin I caused some changes in the high field and low field regions of $^1$H NMR spectra. Whereas, upon addition of Mg$\^$2+/ to Δ-annexin I, almost no change could be observed. Also we found that the binding ratio of ATP to Δ-annexin I is 1. Because Δ-annexin I is a large protein with 35 kDa molecular weight, site-specific (carbonyl-$\^$l3/C, amide-$\^$15/N) labeling technique was used to determine the interaction sites of Δ-annexin I with Ca$\^$2+/ and ATP. Assignments of all the histidinyl carbonyl carbon resonances have been completed by using Δ-annexin I along with its specific 1,2-subdomain. The carbonyl carbon resonances originating from His52 and His246 of Δ-annexin I were significantly affected by Ca$\^$2+/ binding, and some Tyr and Phe resonances were also affected. The carbonyl carbon resonances originating from His52 is significantly affected by ATP binding, therefore His52 seems to be involved in the ATP binding site of Δ-annexin I.

• The Korean Journal of Ceramics
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• 제6권3호
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• pp.315-317
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• 2000

A magnetoplumbite type of Ba ferrite(BaM) layers were deposited on Pt(111) and Pt(200) layers, and their c-axis orientation and magnetic characteristics were compared each other. The as-deposited BaM layer on Pt(111) one at the substrate temperature $T_s$ above $500^{\circ}C$ revealed remarkable c-axis orientation. The saturation magnetization 4$\piM_s$ and the perpendicular coercivity $H_{c⊥}$ of the films as-deposited at $T_s$ of $600^{\circ}C$ were 4.0kG and 2.5kOe, respectively. On the other hand, BaM ferrite layer deposited on Pt(200) layer at $T_s$ as relatively low as $500^{\circ}C$ also revealed weak c-axis orientation as well as (107) one and the films as-deposited at $T_s$ of $600^{\circ}C$ exhibited 4$\piMs_{and}$ $H_{c⊥}$ of 2.8kG and 2.5kOe, respectively. It was suggested that although chemical activity of Pt surface was effective for the formation of BaM crystallites, the lattice matching was also important for obtaining BaM layer with good c-axis orientation and large perpendicular anisotropy.sotropy.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
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• pp.267-272
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• 2007

Uiseong subbasin belonging to Kyungsang basin resulted from volcanic activity in the late Cretaceous. In this study, we carry out MT and gravity survey at the Hwasan caldera, which was formed of volcanic and abyssal rocks complex, then analyze and identify geological substructure. Potential survey such as gravity and magnetic survey has been mainly carried out in former studies, so depth information for understanding substructure was not enough. To complement a potential survey, we use MT method, which has high vertical resolution. Moreover we make a simple 2D model comparing with former study. The result of MT and gravity 2D modeling shows that this area is roughly composed of 3 layers; The bottom layer is a basement. In the second layer, intrusive rocks having high resistivity is placed along the ring faults and the sedimentary layer of low resistivity is inside caldera. The highest layer is alluvium. To comprehend the 3D structure of the Hwasan caldera, we perform 3D gravity inversion, and construct the 3D model from the result of 3D gravity inversion. MT responses are calculated by using the constructed 3D model and the 3D model of the Hwasan caldera's structure is suggested after comparing the calculated values with the observed values at MT line.

• Molecules and Cells
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• 제38권2호
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• pp.180-186
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• 2015

Escherichia coli AcrAB-TolC is a multidrug efflux pump that expels a wide range of toxic substrates. The dynamic nature of the binding or low affinity between the components has impeded elucidation of how the three components assemble in the functional state. Here, we created fusion proteins composed of AcrB, a transmembrane linker, and two copies of AcrA. The fusion protein exhibited acridine pumping activity, suggesting that the protein reflects the functional structure in vivo. To discern the assembling mode with TolC, the AcrBA fusion protein was incubated with TolC or a chimeric protein containing the TolC aperture tip region. Three-dimensional structures of the complex proteins were determined through transmission electron microscopy. The overall structure exemplifies the adaptor bridging model, wherein the funnel-like AcrA hexamer forms an intermeshing cogwheel interaction with the ${\alpha}$-barrel tip region of TolC, and a direct interaction between AcrB and TolC is not allowed. These observations provide a structural blueprint for understanding multidrug resistance in pathogenic Gram-negative bacteria.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.40-44
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• 2003

Soil-borne infectious disease including Pythium aphanidermatum and Rhizoctonia solani causes severe damage to plants, such as cucumber. This soil-borne infectious disease was not controlled effectively by chemical pesticide. Since these diseases spread through the soil, chemical agents are usually ineffective. Instead, biological control, including antagonistic microbe can be used as a preferred control method. An efficient method was developed to select an antagonistic strain to be used as a biological control agent strain. In this new method, surface tension reduction potential of an isolate was included in the ‘decision factor’ in addition to the other factors, such as growth rate, and pathogen inhibition rate. Considering these 3 decision factors by a statistical method, an isolate from soil was selected and was identified as Bacillus sp. GB16. In the pot test, this strain showed the best performance among the isolated strains. The lowest disease incidence rate and fastest seed growth was observed when Bacillus sp. GB16 was used. Therefore this strain was considered as plant growth promoting rhizobacteria (PGPR). The action of surface tension reducing component was deduced as the enhancement of wetting, spreading, and residing of antagonistic strain in the rhizosphere. This result showed that new selection method was significantly effective in selecting the best antagonistic strain for biological control of soil-borne infectious plant pathogen. The antifungal substances against P. aphanidermatum and R. solani were partially purified from the culture filtrates of Bacillus sp. GB16. In this study, lipopeptide possessing antifungal activity was isolated from Bacillus sp. GB16 cultures by various purification procedures and was identified as a surfactin-like lipopeptide based on the Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), high performance liquid chromatography mass spectroscopy (HPLC-MS), and quadrupole time-of-flight (Q-TOF) ESI-MS/MS data. The lipopeptide, named GB16-BS, completely inhibited the growth of Pythium aphanidermatum, Rhizoctonia solani, Penicillium sp., and Botrytis cineria at concentrations of 10 and 50 mg/L, respectively. A novel method to prevent the foaming and to provide oxygen was developed. During the production of surface active agent, such as lipopeptide (surfactin), large amount of foam was produced by aeration. This resulted in the carryover of cells to the outside of the fermentor, which leads to the significant loss of cells. Instead of using cell-toxic antifoaming agents, low amount of hydrogen peroxide was added. Catalase produced by cells converted hydrogen peroxide into oxygen and water. Also addition of corn oil as an oxygen vector as well as antifoaming agent was attempted. In addition, Ca-stearate, a metal soap, was added to enhance the antifoam activity of com oil. These methods could prevent the foaming significantly and maintained high dissolved oxygen in spite of lower aeration and agitation. Using these methods, high cell density, could be achieved with increased lipopeptide productivity. In conclusion to produce an effective biological control agent for soil-borne infectious disease, following strategies were attempted i) effective screening of antagonist by including surface tension as an important decision factor ii) identification of antifungal compound produced from the isolated strain iii) novel oxygenation by $H_2O_2-catalase$ with vegetable oil for antifungal lipopeptide production.

• 한국식품과학회지
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• 제45권2호
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• pp.174-179
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• 2013

본 연구에서는 동양배에 함유된 유용성분을 분자수준에서 밝히고자, 우리나라에서 가장 많이 섭취되고 있는 품종 중의 하나인 추황배를 대상으로 배 과피의 MeOH 추출물을 해리성을 이용하여 용매분획하였다. 얻어진 획분들을 대상으로 항산화 활성에 초점을 맞추어 open column chromatography와 high performance liquid chromatography를 행하여 3종의 항산화 화합물을 단리하였다, 그 결과, BuOH 획분으로부터 화합물 1을, EtOAc-산성 획분으로부터 화합물 2를, 그리고 EtOAc-페놀성 획분으로부터 화합물 3을 단리하고, 각각 NMR 및 MS 분석을 행하여 구조해석을 행하였다. 그 결과, 화합물 1-3은 각각 2-carboxyl 4(1H)-quinolinone (kynurenic acid, 화합물 1), cis-coumaric acid (화합물 2), 그리고 vanillin(화합물 3)으로 동정되었다. 이 3종의 화합물 모두 본 연구에 의해 배로부터 처음 동정되었다. 본 연구결과가 배의 유용성 및 기능성 연구를 위한 기초자료로 활용되길 기대한다.

• Journal of Microbiology and Biotechnology
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• 제27권7호
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• pp.1249-1256
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• 2017

In our search for new sources of bioactive secondary metabolites from Streptomyces sp., the ethyl acetate extracts from endophytic Streptomyces SUK 25 afforded five active diketopiperazine (DKP) compounds. The aim of this study was to characterize the bioactive compounds isolated from endophytic Streptomyces SUK 25 and evaluate their bioactivity against multiple drug resistance (MDR) bacteria such as Enterococcus raffinosus, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa, and Enterobacter spp., and their cytotoxic activities against the human hepatoma (HepaRG) cell line. The production of secondary metabolites by this strain was optimized through Thornton's medium. Isolation, purification, and identification of the bioactive compounds were carried out using high-performance liquid chromatography, high-resolution mass liquid chromatography-mass spectrometry, Fourier transform infrared spectroscopy, and nuclear magnetic resonance, and cryopreserved HepaRG cells were selected to test the cytotoxicity. The results showed that endophytic Streptomyces SUK 25 produces four active DKP compounds and an acetamide derivative, which were elucidated as $cyclo-({\text\tiny{L}}-Val-{\text\tiny{L}}-Pro)$, $cyclo-({\text\tiny{L}}-Leu-{\text\tiny{L}}-Pro)$, $cyclo-({\text\tiny{L}}-Phe-{\text\tiny{L}}-Pro)$, $cyclo-({\text\tiny{L}}-Val-{\text\tiny{L}}-Phe)$, and N-(7-hydroxy-6-methyl-octyl)-acetamide. These active compounds exhibited activity against methicillin-resistant S. aureus ATCC 43300 and Enterococcus raffinosus, with low toxicity against human hepatoma HepaRG cells. Endophytic Streptomyces SUK 25 has the ability to produce DKP derivatives biologically active against some MDR bacteria with relatively low toxicity against HepaRG cells line.