• Journal of Microbiology and Biotechnology
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• v.3 no.2
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• pp.123-128
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• 1993

The polyesters (polyhydroxyalkanoates; PHAs) production capability in a two-step cultivation of Alcaligenes eutrophus H16(ATCC 17699) was investigated by using various organic carbon sources. The carbon sources used included linear $C_2~C_10$ monocarboxylic acids, $C_3~C_10$ dicarboxylic acids, crotonic acid, and several linear vicinal and $\omega$-diols. The polyesters synthesized were characterized by 500 MHz $^1 H-NMR$ spectroscopy, intrinsic viscosity$[\eta]$ measurement in chloroform and differential scanning calorimetry (DSC). The PHAs synthesis data showed that the use of C-odd ($C_3, C_5, and C_7$) monocarboxylic acids resulted in poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(P(3HB-co-3HV) (3HV content ranging 40 to 70 mol%) while the use of $C_9$ substrate gave the copolyester containing only 4 mol% of 3HV. All culture products obtained on $C_3$~C$_{10}$ dicarboxylic acids gave exclusively P(3HB). 500 MHz $^1 H-NMR$ analysis showed that all polyesters synthesized generally contained 1~2 mol% 3HV even for the unrelated substrates such as the carboxylic acids with even number of carbon. When $\alpha, \omega$-diols with even number of carbon were used as substrates, 4-hydroxybutyrate(4HB) was inserted into the polyester chain composed of P(3HB-co-4HB). Vicinal diols were generally not utilized by the bacterium for polyester production.n.

• Journal of the Korean Magnetics Society
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• v.12 no.5
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• pp.179-183
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• 2002

Fe-Si-C alloy system has been made by mechancial alloying process. The structural and magnetic properties were analysed as a function of processing times. The structural properties were investigated by X-ray diffraction and EXAFS experiments. The magnetic properties were measured by vibrating sample magnetometer and M ssbauer spectroscopy. As processing time increases, Si and C atoms diffuse into a ${\alpha}$-Fe structure and then bcc solid solution is formed after 12 hours of the processing time. The magnetization and the hyper fine field decreased steeply up to 4 hours and then it changed slowly. After 12 hours of the processing time, it almost saturated. These results were agreed with the structural variation.

• BMB Reports
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• v.46 no.5
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• pp.282-287
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• 2013

Cecropin A and papiliocin are novel 37-residue cecropin-like antimicrobial peptides isolated from insect. We have confirmed that papiliocin possess high bacterial cell selectivity and has an ${\alpha}$-helical structure from $Lys^3$ to $Lys^{21}$ and from $Ala^{25}$ to $Val^{35}$, linked by a hinge region. In this study, we demonstrated that both peptides showed high antimicrobial activities against multi-drug resistant Gram negative bacteria as well as fungi. Interactions between these cecropin-like peptides and phospholipid membrane were studied using CD, dye leakage experiments, and NMR experiments, showing that both peptides have strong permeabilizing activities against bacterial cell membranes and fungal membranes as well as $Trp^2$ and $Phe^5$ at the N-terminal helix play an important role in attracting cecropin-like peptides to the negatively charged bacterial cell membrane. Cecropin-like peptides can be potent peptide antibiotics against multi-drug resistant Gram negative bacteria and fungi.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.69.1-69.1
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• 2015

Classical T Tauri star DG Tau is suggested as the driving source of parsec-scale jet which expands up to 650" (0.4 pc). To investigate the kinematics and physical properties of the jet, we have obtained the optical emission lines of $H{\alpha}$, [O I] ${\lambda}{\lambda}$6300, 6363, [N II] ${\lambda}{\lambda}$6548,6584, and [S II] ${\lambda}{\lambda}$6716, 6731 from HH 158 ad HH 702. The radial velocity of HH 158 is in the range of -50 to $-250km\;s^{-1}$. For HH 702, located at 650" from the source, it shows ~ $-80km\;s^{-1}$. In HH 158, the electron density ($n_e$) close to the star is ${\sim}10^4cm^{-3}$ and it decreases to ${\sim}10^2cm^{-3}$ at 14" away from the star. Electron temperature ($T_e$) is decreasing from >15,000 K to ~5,000 K with distance. Ionization fraction ($x_e$) is increasing from almost zero to > 0.4 along the distance. In HH 702, the values of $n_e$, $T_e$, and $x_e$ are similar to those estimated at 14" from source, where knot C of HH 158 is located. This may imply that the physical properties of the knot could persist through such a long distance in the space, and the gas could be re-excited by the shock during propagation of the jet. On the other hand, we cannot avoid the possibility that HH 702 is driven by another source rather than DG Tau because HH 158 and HH 702 show somewhat large difference in their inclination angles (${\Delta}i=21-35^{\circ}$).

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.131-133
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• 2017

We present the latest results from the Mission Program NIRLT (PI: I.Yamamura), the near-infrared spectroscopy of brown dwarfs using the AKARI/IRC grism mode with the spectral resolution of ~ 120. The near-infrared spectra in the wavelength range between 2.5 and $5.0{\mu}m$ are especially important to study the brown dwarf atmospheres because of the presence of major molecular bands, including $CH_4$ at $3.3{\mu}m$, $CO_2$ at $4.2{\mu}m$, CO at $4.6{\mu}m$, and $H_2O$ around $2.7{\mu}m$. We observed 27 sources, and obtained 16 good spectra. Our model fitting reveals deviations between theoretical model and observed spectra in this wavelength range, which may be attributed to the physical condition of the upper atmosphere. The deviations indicate additional heating, which we hypothesize to be due to chromospheric activity. We test this effect by modifying the brown dwarf atmosphere model to artificially increase the temperature of the upper atmosphere, and compare the revised model with observed spectra of early- to mid-L type objects with $H{\alpha}$ emission. We find that the chemical structure of the atmosphere changes dramatically, and the heating model spectra of early-type brown dwarfs can be considerably improved to match the observed spectra. Our result suggests that chromospheric activity is essential to understand early-type brown dwarf atmospheres.

• Korean Journal of Materials Research
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• v.10 no.3
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• pp.241-245
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• 2000

Thick GaN films were grown on (0001) sapphire substrates using the direct reaction gallium and ammonia. The GaN films grew dominantly along [0002] direction, but included the growth of GaN(1010) planeq with V-shaped facetted surfaces at low temperature. With increasing growth temperature, however, the growth of GaN (1010) and (1011) planes was appeared from the films, which gives rise to the growth of hexagonal crystal with pyramid-shaped surface. The growth rate of GaN films increased with increasing growth temperature, but decreased at $1270^{\circ}C$ because the GaN films began to decompose into Ga and N at the temperature. It seemed that the crystal and optical qualities of the GaN films improve with increasing $NH_3$ flow rate. From X-ray diffraction (XRD) and photoluminescence (PL) measurements, it was observed that the yellow luminescence (YL) appeared to be significant as the peak intensity of (1010) plane of XRD spectra increased.

• Journal of the Korean Magnetic Resonance Society
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• v.11 no.1
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• pp.30-41
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• 2007

The backbone molecular dynamics of the C-terminal part of the mouse Cdt1 protein (tCdt1, residues 420-557) was studied by high field NMR spectroscopy. The Secondary structure of this protein was suggested by analyzing of chemical shift of backbone atoms with programs TALOS and PECAN, together with NOE connectivities from 3D $^{15}N-HSQC-NOESY$ data. Measurement of dynamic parameters $T_1,\;T_2$ and NOE and limited proteolysis experiment provided information for domain organization of tCdt1(420-557). Analysis of the experimental data showed that the C-terminal part of the tCdt1 has well folded domain for residues 455-553. The residues 420-453 including ${\alpha}-helix$ (432-441) are flexible and probably belong to other functional domain in intact full length Cdt1 protein.

• Journal of the Korean Magnetic Resonance Society
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• v.18 no.1
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• pp.30-35
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• 2014

The transcription factor CP2 regulates various biological systems at diverse tissues and cells. However, none of the four CP2 isoforms has been solved in structure yet. In particular, two different regions of the CP2b isoform have been characterized to interact with the PIAS1 in nucleus to regulate the ${\alpha}$-globin gene expression. Among them, in this study, the region encompassing residues 251-309 of CP2b was prepared as a recombinant protein and its solution structure was characterized by NMR spectroscopy. The results indicated that the CP2b(251-309) fold belongs to typical IDRs (intrinsically disordered regions), likely to facilitate promiscuous interactions with various target proteins. Unfortunately, however, its interaction with the N-terminal domain of PIAS1 (residues 1-70), which has been identified as one of the CP2b-binding sites, was not observed in the NMR-based titration experiments. Therefore, it could be postulated that the 251-309 region of CP2b would not contact with the PIAS1(1-70), but alternatively interact with another CP2b-binding region that encompasses residues 400-651 of PIAS1.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.200-200
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• 2013

기존 메모리 반도체에 비교해 빠른 재생속도와 높은 집적도, 비휘발성 등의 특성을 가지는 MRAM (Magnetic Random Access Memory)은 DRAM, flash memory 등을 대체할 수 있는 차세대 기억 소자로서 CoFeB/MgO/CoFeB로 구성된 한 개의 MTJ (Magnetic Tunnel Junction)를 단위 메모리로 사용한다. 이 MTJ 물질들은 고밀도 플라즈마를 이용한 건식 식각공정시 Cl2, BCl3 등과 같은 chlorine 을 포함한 가스를 이용하여 왔으나 식각 후 sidewall에서 발생하는 부식과 식각 선택비 확보의 어려움 등으로 마스크 물질에 제약을 받고 소자 특성이 감소하게 되는 등의 문제가 있다. 따라서 이러한 식각 문제점을 해결하기 위한 대안으로 noncorrosive 가스인 CO/NH3, CH3OH, CH4 등을 이용한 MTJ 식각 연구가 진행되어 오고 있으며 이중 CO/NH3 혼합가스는 부식성이 없고 hard mask와의 높은 선택비를 가지는 기체로 CO gas에 NH3 gas를 첨가하게 되면 etch rate이 증가하는 특성을 보인다. 또한 rf pulse-biased power를 이용하여 이온의 입사를 시간에 따라 제어함으로써 pulse off time 때 etch gas와 MTJ 물질간의 chemical reaction을 향상시킬 수 있다. 따라서 본 연구에서는 CO/NH3 혼합가스를 이용하여 다양한 rf pulse-biased power 조건에서 MTJ 물질인 CoFeB, MgO와 hard mask 물질인 W을 식각 한 뒤 식각특성을 분석하였으며 MTJ surface의 chemical binding state, surface roughness 측정을 진행하였다. 식각 샘플의 측정은 Alpha step profiler, XPS (X-ray Photoelectron Spectroscopy), AFM (Atomic Force Microscopy)를 통해 진행되었다. Time-averaged pulse bias에서는 duty ratio가 감소할수록 etch rate의 큰 감소 없이 CoFeB/W, MgO/W 물질의 etch selectivity가 향상됨을 확인할 수 있었으며 pulse off time 구간에서의 chemical reaction 향상으로 인해 식각부산물의 재증착이 감소하고 CoFeB의 surface roughness가 감소하는 것을 확인하였다.

• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1250-1257
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• 2005

Two groups of exopolysaccharides (designated as Fr-I EPS and Fr-II EPS) were isolated from the culture filtrate of new fungal strain Trichoderma erinaceum DG-312 by Sepharose CL-6B chromatography. The structures of the exopolysaccharides were investigated using gas chromatography (GC), Fourier transform-infrared (FT-IR) spectroscopy, GCMS analysis, and NMR. GC analysis indicated that Fr-I EPS was composed of mainly mannose ($78.9\%$) and galactose ($21.1\%$), whereas Fr-II EPS contained mannose ($68.4\%$), galactose ($26.2\%$), and glucose ($5.4\%$). In the anomeric region ($950-700cm_{-1}$) of the FT-IR spectrum, both EPSs exhibited obvious characteristic absorption of $810\;cm_{-1}$, indicating the existence of mannose. The spectra of $\alpha-and\;\beta$-configurations were assigned at 880 and $914\;cm_{-1}$, respectively. The results of GC-MS analyses confirmed that both EPSs were complex heteropolysaccharides with a ($1{\rightarrow}3$)-linked mannan backbone. The C-1 region that appeared in the $^{13}C-NMR$ spectra of these EPSs indicated a typical anomeric carbon signal. The Fr-I EPS showed two anomeric carbon signals at 102.6 and 99.6 ppm, whereas the Fr-II EPS displayed four anomeric carbon signals at 102.5, 99.6, 98.5, and 94.3 ppm. The molecular characteristics of the EPSs were further investigated using a size exclusion chromatography/multi-angle laser light scattering (SEC/MALLS) system. The SEC/MALLS system revealed that the average molar masses of the EPSs were $6.592{\times}10^{4}$ (Fr-I EPS) and $1.920{\times}10^{4}$ (Fr-II EPS) g/mol, and the molecular conformation of both EPSs in aqueous solution was random coils.