• Bulletin of the Korean Chemical Society
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• v.30 no.3
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• pp.599-607
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• 2009

A series of conjugated cyclic and linear enkephalin analogs, Tyr-c[D-A2bu-Gly-Phe-Asp(NH-X)], where X = methyl, stearyl or$ PEG_350$, and Tyr-D-Ala-Gly-Phe-Cys(S-X), where X = methyl, octyl, or farnesyl, were synthesized in solution to investigate the receptor selectivity of opioids based on Schwyzer's membrane compartment $concepts.^{5,6}$ Cyclizations of the target compounds were achieved in high yields (> 60%) employing BOP, $NaHCO_3$ in DMF despite the steric hindrance of the bulky pendant groups. In the binding assay, the hydrophobic fatty acyl conjugates retained $\mu$-receptor selectivity. The unsaturated farnesyl conjugate exhibited the increased binding affinity than the saturated stearyl conjugate for both $\mu$-and $\delta$-opioid receptors. The PEG conjugates displayed the $\delta$-receptor selectivity. The low molecular weight $PEG_350$ conjugate exhibited the increase selectivity than the high molecular weight $PEG_5000$ conjugate to the $\delta$-receptor. The results of this study support the membrane compartment concepts.

• Bulletin of the Korean Chemical Society
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• v.24 no.5
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• pp.627-632
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• 2003

The pH dependence of the kinetic parameters of recombinant acetohydroxy acid synthase catalyzed reaction was determined in order to obtain information about the chemical mechanism, particularly acid-base chemistry. The maximum velocity and V/K for pyruvate were bell-shaped with estimated pK values of 6.5-6.7 and 8.6-8.9, respectively. The maximum velocity and V/K for 2-ketobutyrate were also bell-shaped with estimated pK values of 6.6-7.0 and 8.4-8.6. The pH dependence of 1/Ki for 3-bromopyruvate, a competitive inhibitor of pyruvate, was also bell-shaped, giving pK values almost identical with those obtained for pyruvate. Since the same pK values were observed in the $pK_{i 3-bromopyruvate}$, V/K pH profiles and $V_{max}$ profiles, both enzyme groups must be in their optimum protonation state for efficient binding of reactants. These results reflect that two enzyme groups are necessary for binding of substrate and/or catalysis.

• Bulletin of the Korean Chemical Society
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• v.24 no.5
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• pp.579-582
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• 2003

Norfloxacin, that inhibits the action of topoisomerase Ⅱ, binds to wide variety of DNA. The binding mode of this drug to double- and super-coiled DNA (ds- and scDNA) is compared in this study by various spectroscopic methods, including absorption, fluorescence, and circular dichroism(CD) spectroscopy. Hypochromism in the absorption band, negative and positive induced CD bands (respectively in 240-260 nm and 270-300 nm region) are apparent for the norfloxacin that bound to both the dsDNA and scDNA. A decrease in fluorescence is also noticed in the presence of both DNAs. Since the spectroscopic characteristics are the same for both complexes, it is imperative that the binding mode of the norfloxacin is similar in ds- and scDNA. In the presence of $Mg^{2+}$, which is a cofactor in the topoisomerase Ⅱ action, the fluorescence intensity of the scDNA-norfloxacin complex increased and the resulting fluorescence intensity and shape was identical to that in the absence of scDNA. Therefore, the addition of an excess amount of $Mg^{2+}$ may result in the extrusion of norfloxacin from scDNA.

• Transactions on Electrical and Electronic Materials
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• v.14 no.6
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• pp.329-333
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• 2013

SiOC films were prepared by capacitively coupled plasma chemical vapor deposition, and the correlation between the binding energy by X-ray photoelectron spectroscopy and Arrhenius equation for ionization energy was studied. The ionization energy decreased with increase of the potential barrier, and then the dielectric constant also decreased. The binding energy decreased with increase of the potential barrier. The dielectric constant and electrical characteristic of SiOC film was obtained by Arrhenius equation. The dielectric constant of SiOC film was decreased by lowering the polarization, which was made from the recombination between opposite polar sites, and the dissociation energy during the deposition. The SiOC film with the lowest dielectric constant had a flat surface, which depended on how carbocations recombined with other broken bonds of precursor molecules, and it became a fine cross-linked structure with low ionization energy, which contributed to decreasing the binding energy by Si 2p, C 1s electron orbital spectra and O 1s electron orbital spectra. The dielectric constant after annealing decreased, owing to the extraction of the $H_2O$ group, and lowering of the polarity.

• Journal of Microbiology and Biotechnology
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• v.25 no.7
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• pp.963-977
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• 2015

The well-characterized gram-positive bacterium Bacillus subtilis is an outstanding industrial candidate for protein expression owing to its single membrane and high capacity of secretion, simplifying the downstream processing of secretory proteins. During the last few years, there has been continuous progress in the illustration of secretion mechanisms and application of this robust host in various fields of life science, such as enzyme production, feed additives, and food and pharmaceutical industries. Here, we review the developments of Bacillus subtilis as a highly promising expression system illuminating strong chemical- and temperatureinducible and other types of promoters, strategies for ribosome-binding-site utilization, and the novel approach of signal peptide selection. Furthermore, we outline the main steps of the Sec pathway and the relevant elements as well as their interactions. In addition, we introduce the latest discoveries of Tat-related complex structures and functions and the countless applications of this full-folded protein secretion pathway. This review also lists some of the current understandings of ATP-binding cassette transporters. According to the extensive knowledge on the genetic modification strategies and molecular biology of Bacillus subtilis, we propose some suggestions and strategies for improving the yield of intended productions. We expect this to promote striking future developments in the optimization and application of this bacterium.

• Journal of the Korean Magnetic Resonance Society
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• v.21 no.3
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• pp.109-113
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• 2017

The hepatitis C virus (HCV) internal ribosome entry site (IRES) is an RNA structure located in the 5'-UTR of the HCV RNA genome. The HCV IRES consists of four domains I, II, III, and IV, where domains II - IV are recognized by 40S ribosomal subunit and the domain III is bound to eukaryotic initiation factor 3 (eIF3) for translation initiation. Here, we have characterized the tertiary interaction between an L-/K- rich peptide and the HCV IRES domain IV. To probe the peptide binding interface in RNA, we synthesized $^{13}C$- and $^{15}N$-double labeled RNA and the binding site was identified by using the chemical shift perturbation (CSP) NMR methods. Our results showed that the peptide binds to the upper stem of the IRES domain IV, indicating that the tertiary interaction between the IRES domain IV and the peptide would disrupt the initiation of translation of HCV mRNA by blocking the start codon exposure. This study will provide an insight into the new peptide-based anti-viral drug design targeting HCV IRES RNA.

• Journal of the Korean Magnetic Resonance Society
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• v.10 no.2
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• pp.163-174
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• 2006

Luteinizing Hormone Releasing Hormone(LHRH) is a decapeptide neurotransmitter known to be regulated by metal ions in the hyperthalamus. Zn-binding LHRH complex was systhesized, and zinc-LHRH complex was studied to understand what kinds of structural modifications would be critical in the LHRH releasing mechanism. Both nonexchangeable and exchangeable $^1H-NMR$ signal assignments were accomplished by pH-dependent and COSY NMR experiments. In addition, $^1H-NMR$ chemical shift changes of a-proton and peptide NH NMR signals at different pH condition, and $^1H-NMR$ signal differences between metal free and metallo-LHRH complex was monitored. NMR signals exhibit that primary metal-binding sites are nitrogens donor of imidazole ring and Arg, and peptide oxygen of Pro-His in the sequence. Structure obtained in this study has a cyclic conformation which is similar to that of energy minimized, and exhibits a specific a-helical turn with residue numbers $(2{\sim}7)$ out of 10 amino acids.

• Journal of the Korean Magnetic Resonance Society
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• v.1 no.1
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• pp.31-44
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• 1997

The effect of the binding of CRP to the symmetrically synthetic 22, 28, and 30 bp lac promoter was investigated by 1H NMR. The binding of cAMP*CRP to the 22 bp DNA did not bring about any changes in the chemical shift values, but did cause selective line broadening of imino proton resonances of specific base pairs. However, The binding of cAMP*CRP to the 28 and 30 bp DNA brought about large changes on the imino proton resonances that seems to be induced by DNA bending. We studied also the role of cAMP as an activator of DNA/CRP complex formation by gel mobility shift assay. Gel mobility shift assay revealed that the cAMP*CRP complex was not able to bind to the 22 bp DNA fragment, but was able to bind to the 28 bp DNA fragment of lac promoter region.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.704-710
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• 2017

Although the desalination technique using gas hydrate formation is at a development stage compared to the commercially well-established reverse osmosis (RO), it still draws attention because of its simplicity and moderate operational conditions especially when using refrigerants for guest gases. In this study, DFT (density functional theory)-based molecular modeling was employed to explain the energetics of the gas hydrate formation using HFC (hydrofluorocarbon) and HCFC (hydrochlorofluorocarbon) refrigerants. For guest gases, R-134a, R-227ea, R-236fa, and R-141b were selected and three cavity structures ($5^{12}$, $5^{12}6^2$, and $5^{12}6^4$) composed of water molecules were constructed. The geometries of guest gas, cavity, and cavity encapsulating guest gas were optimized by molecular modeling respectively and their located energies were then used for the calculation of binding energy between the guest gas and cavity. Finally, the comparison of binding energies was used to propose which refrigerant is more favorable for the gas hydrate formation energetically. In conclusion, R-236fa was the best choice in terms of thermodynamic spontaneity, less toxicity, and low solubility in water.

• Journal of the Korean Chemical Society
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• v.37 no.5
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• pp.491-495
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• 1993

Synthesis of polymer-supported azacrown ether ion exchanger, {(4,5): (13,14)-dibenzo-6,9,12-trioxa-3,15,21-triazazabicyclo[15.3.1]heneicosa-1(21),17,19-triene-2,16-dione : DBPDA ion exchanger}, and its ion binding ability to alkali metal $(Li^+,\;Na^+,\;K^+)$ picrates were studied. The binding constants $(K_b)$ of DBPDA ion exchanger to the alkali metal picrates in ether type solvents were obtained by spectrophotometry. Binding constants of alkali metal ions were in the order to Li < Na < K, and alkali metal ions were formed 1 : 1 complexes with ligands of DBPDA ion exchanger. Also, $K_b$ was found to depend on the variables such as solvent and temperature. The binding constants for the complexes were obtained in the ranges of $2{\times}10^3{\sim}4{\times}10^4M^{-1}$. In order to obtain the enthalpy (${\Delta}$H) and entropy changes (${\Delta}$S)n the complexation process, Kb were plotted against the temperature in the ranges of 10∼40$^{\circ}C$ according to the van't Hoff theory. Enthalphy and entropy changes were found in the ranges of -2.71∼-3.79 kcal/mol, and -16.52∼-20.57 eu, respectively.