• Journal of the Korean Magnetic Resonance Society
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• v.9 no.2
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• pp.110-121
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• 2005

E.coli methionyl tRNA synthetase consist of 676 amino acids and plays a key role in initiation of protein synthesis. The native form of this enzyme is a homodimer, but the monomeric enzyme truncated approximately C-terminal 120 amino acids retains the full enzymatic activities. X-ray crystal structure of the active monomeric enzyme shows that it has two domains. The N-terminal domain is thought to be a binding site for acceptor stem of tRNA, ATP, and methionine. The C-terminal domain is mainly a-helical and makes an interaction with the anticodon of $tRNA^{Met}$. Especially it is suggested that the region of helix-loop-helix including the tryptophan residue at the position 461 may be the essential for the interaction with anticodon of $tRNA^{Met}$. In this work the structure and function of E. coli methionyl-tRNA synthetase was studied by spectroscopic method (NMR, CD, Fluorescence). The importance of tryptophan residue at the position 461 was investigated by fluorescence spectroscopy. Tryptophan 461 is expected to be an essential site for the interaction between E. coli methionyl-tRNA synthetase and E. coli $tRNA^{Met}$. Proton and heteonuclear 2-dimensional NMR spectroscopy were also used to elucidate the protein-tRNA interaction.

• Bulletin of the Korean Chemical Society
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• v.16 no.2
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• pp.112-120
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• 1995

The conformational study on malonic acid, hydrogen malonate, malonate, malonyl methyl sulfide, and malonyl methyl sulfide anion, as the model compounds of malonyl-CoA, was carried out using the semiempirical MO methods (MNDO, AM1, and PM3) and hydration shell model. On the whole, the feasible conformations of malonic acid, hydrogen malonate, and malonate seem to be similar to each other. In malonic acid and malonate, two carboxyl groups are nearly perpendicular to the plane of the carbon skeleton, despite of different orientation of two carboxyl groups themselves. In particular, two carboxyl groups of hydrogen malonate are on the plane formed by carbon atoms with an intramolecular hydrogen bond. The calculated results on the geometry and conformation of three compounds are reasonably consistent with those of X-ray and spectroscopic experiments as well as the previous calculations. The orientation of two carbonyl groups of malonyl methyl sulfide is quite similar to that of malonic acid, but different from that of its anion. Especially, the computed probable conformations of the sulfide anion by the three methods are different from each other. The role of hydration seems not to be crucial in stabilizing the overall conformations of malonic acid, hydrogen malonate, malonate, and malonyl methyl sulfide. However, the probable conformations of the unhydrated sulfide anion obtained by the MNDO and AM1 methods become less stabilized by including hydration. The AM1 method seems to be appropriate for conformational study of malonyl-CoA and its model compounds because it does not result in the formation of too strong hydrogen bonds and significant change in conformational energy from one compound to another.

• Korean Journal of Optics and Photonics
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• v.2 no.4
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• pp.209-213
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• 1991

Recently, the developments in generating and amplifying ultrashort optical pulses $(ps=10^{-12}s or fs=10^{-15}s)$ have imposed on great advances in the time-resolved laser spectroscopy. Especially, the transient absorption spectroscopy has a wide application range and the main idea of this technique is pump & probe method. After the pump pulse makes the material an excited or a transient states, the probe pulse is sent through the material to measure the absorbance change due to the transient states. Here, if the absorbance change was measured by the time delay between pump & probe pulses, the dynamic information of the excited or the transient states (the transient abnsorption changes by time & wavelength) can be obtained. At our laboratory, the ultrashort optic1 pulse (

• Journal of Sericultural and Entomological Science
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• v.53 no.2
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• pp.118-123
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• 2015

The structural transition of silk protein has been induced by various method including alcohol treatment. To know the effect of alcohol concentration on silk beads conformation, silk beads were prepared in different alcohol concentration (100%, 70%, and 50%) and then examined the infrared spectra of silk beads. Silk beads prepared in 100% alcohol showed at $1265cm^{-1}$ attributed ${\beta}-sheet$ conformation and did not showed a characteristic absorption peak from model drug. However, silk beads in 70% and 50% alcohol showed some peaks originated from model drug including $2933cm^{-1}$, $1069cm^{-1}$, and $973cm^{-1}$. These results means that the micro-environment of silk beads was affected by alcohol concentration.

• Journal of The Korean Astronomical Society
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• v.54 no.2
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• pp.37-47
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• 2021

Reverberation mapping (RM) is an efficient method to investigate the physical sizes of the broad line region (BLR) and dusty torus in an active galactic nucleus (AGN). The Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx) mission will provide multi-epoch spectroscopic data at optical and near-infrared wavelengths. These data can be used for RM experiments with bright AGNs. We present results of a feasibility test using SPHEREx data in the SPHEREx deep regions for torus RM measurements. We investigate the physical properties of bright AGNs in the SPHEREx deep field. Based on this information, we compute the efficiency of detecting torus time lags in simulated light curves. We demonstrate that, in combination with complementary optical data with a depth of ~ 20 mag in B-band, lags of ≤ 750 days for tori can be measured for more than ~ 200 bright AGNs. If high signal-to-noise ratio photometric data with a depth of ~ 21-22 mag are available, RM measurements are possible for up to ~ 900 objects. When complemented by well-designed early optical observations, SPHEREx can provide a unique dataset for studies of the physical properties of dusty tori in bright AGNs.

• Korean Journal of Pharmacognosy
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• v.50 no.2
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• pp.148-153
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• 2019

The lignan compound of Schisandra chinensis Baill. (Schizandraceae) has been reported to have a variety of biological activities such as liver protection, neuroprotection, anti-oxidant and anti-diabetes. In this study, we investigated a quantitative analytical method for schisandrin, gomisin A and gomisin $M_2$ isolated from S. chinensis by high-performance liquid chromatography-ultraviolet spectroscopy (HPLC-UV). The isolated compounds were identified by the analysis of 1H- and 13C-NMR spectroscopic data. The results showed that calibration curves of three compounds indicated great linearity with a correlation coefficient ($R^2$) of schisandrin 0.9983, gomisin A 0.9982 and gomisin $M_2$ 0.9986. The limits of detection (LOD) of schisandrin, gomisin A and gomisin $M_2$ were 0.14, 0.07 and $0.05{\mu}g/ml$ and the limits of quantification (LOQ) were 0.42, 0.22 and $0.14{\mu}g/ml$. Intra-day and inter-day precisions of schisandrin were 0.40~1.44%, 0.07~1.02% gomsin A were 0.22~0.52%, 0.10~0.63%, gomisin $M_2$ were 0.40~0.99%, 0.81~2.88%. In result, contents of schisandrin, gomisin A and gomisin $M_2$ in ethanol extract of S. chinensis were $25.95{\pm}0.15$, $2.51{\pm}0.02$ and $2.17{\pm}0.07mg/g$.

• Journal of Climate Change Research
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• v.7 no.3
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• pp.351-356
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• 2016

The carbon capture and storage (CCS), which collects and stores carbon dioxide in a geological site, is a promising option to mitigate climate change. However, there is the possibility of carbon dioxide leakage from the soil in the steps of collecting, transporting, and storing. To ensure the feasibility of this technology, it is important to monitor the leakage of carbon dioxide and to assess the potential impacts. As plants are sensitive to the changes in carbon dioxide in the soil environment, we can utilize plant parameter to detect the carbon dioxide leakage. Currently, chlorophyll a content is a conventional index indicating the changes in plants, however, this method is labor intensive and it only utilizes a small portion of leaves. To overcome its limitations, a simple spectroscopic parameter, DGCI (dark green color index), was suggested as an easy and quick indicator. In this study, we compared the values of chlorophyll a contents with DGCI from the experiment investigating the impacts of high underground $CO_2$ on grape plants. Results suggest that DGCI had high correlation with chlorophyll a contents and it has high potential to be utilized as an easy indicator to monitor plants' responses to $CO_2$ treatment.

• Current Optics and Photonics
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• v.5 no.3
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• pp.229-237
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• 2021

The capabilities of the near-field scanning optical microscope (NSOM) for obtaining high resolution lateral topographical images as well as for mapping the spectroscopic and optical properties of a sample below the diffraction limit of light have made it an attractive research field for most researchers dealing with optical characteristics of materials in nano scales. The apertured NSOM technique involves confining light into an aperture of sub-wavelength size and using it to illuminate a sample maintained at a distance equal to a fraction of the sub-wavelength aperture (near-field region). In this article, we present a setup for developing NSOM using a cantilever with a sub-wavelength aperture at the tip. A single laser is used for both cantilever deflection measurement and near-field sample excitation. The laser beam is focused at the apex of the cantilever where a portion of the beam is reflected and the other portion goes through the aperture and causes local near-field optical excitation of the sample, which is then raster scanned in the near-field region. The reflected beam is used for an optical beam deflection technique that yields topographical images by controlling the probe-sample in nano-distance. The fluorescence emissions signal is detected in far-field by the help of a silicon avalanche photodiode. The images obtained using this method show a good correlation between the topographical image and the mapping of the fluorescence emissions.

• Fisheries and Aquatic Sciences
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• v.24 no.10
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• pp.319-329
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• 2021

In the search for antibiotic alternatives from safe and effective medicinal plants against fish pathogenic bacteria, we found that a combined extract (CE) of 1:1 (w/w) ratio of Angelica gigas Nakai roots and aerial parts of Artemisia iwayomogi Kitamura showed antibacterial activity against the fish pathogenic bacteria. By antibacterial activity-guided fractionations and isolations, five compounds were isolated and identified as decursinol angelate (1), decursin (2), xanthotoxin (3), demethylsuberosin (4), and 2,4-dihydroxy-6-methoxyacetophenone (5) through spectroscopic analyses, such as nuclear magnetic resonance (NMR) and mass spectrometry (MS). Among the compounds, 1 and 2 showed the highest antibacterial activities against Streptococcus iniae and Vibrio anguillarum, showing minimum inhibitory concentrations (MICs) of 62.5-250 ㎍/mL. Compounds 3, 4, and 5 were also found to be active, with MICs of 31.25-1,000 ㎍/mL for those strains. Furthermore, active compounds, 1 and 2 in CE were simultaneously quantified using high-performance liquid chromatography-tandem MS (HPLC-MS/MS). The average contents of 1 and 2 in CE was 3.68% and 6.14%, respectively. The established method showed reliable linearity (r² > 0.99), good precision, accuracy, and specificity with intra- and inter-day variations of < 2 % and recoveries of 90.13%-108.57%. These results may be helpful for establishing the chemical profile of CE for its commercialization as an antibiotic alternative in aquaculture.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.2
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• pp.164-175
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• 2022

In this work, sulfonated poly (ether ether ketone) (SPEEK) composite membranes including strontium zirconate (SrZrO₃) were fabricated by the electrospinning method. Fourier-transform infrared spectroscopic analysis and X-ray diffraction analysis were used to identify the chemical structure and the crystallinity of SrZrO₃ and electrospun composite membranes. The thermal stability of the pure SPEEK and SPEEK/SrZrO₃ electrospun composite membranes were investigated by using thermogravimetric analysis. The physicochemical properties and proton conductivity were enhanced with the addition of different weight ratio of SrZrO₃ nanofiller (2, 4 and 6 wt%) in SPEEK polymer. The optimized SPEEK/SrZrO₃-4 electrospun membrane containing 4 wt% of SrZrO₃ showed a high proton conductivity compared to other electrospun SPEEK/SrZrO₃ composite membranes. The results indicate that electrospun composite membranes incorporating these perovskite nanofillers should be explored as potential candidates for use in proton exchange membrane fuel cells.