• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.749-753
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• 1998

Methoxy polyoxyethylene dodecanoates, kinds of nonionic surfactants, could be obtained from addition of ethylene oxide (5, 7, 9, and 12mol) with fatty acid methyl ester utilizing solid catalyst, metal oxide. Because ethylene oxide (EO) couldn't react directly in acid or alkali catalyst with dodecanoic acid methyl ester (DME) that had no active hydrogen, the reaction to add EO was carried out using active solid catalyst. By using IR, HPLC and $^1H$ NMR analysis, structural confirmation of methyl polyoxy ethylene dodecanate showed high yield ranging from 93 to 97%. EO unit mol number of reacted products was 5.2, 7.1, 9.2 and 12.1 mol respectively. Also, EO adduct distrobution of ethoxylated methyl laurate (MPD) had normal distribution curve like polyoxyethylene alkyl ether (AE).

• 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.

• Korean Journal of Metals and Materials
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• v.50 no.5
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• pp.401-406
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• 2012

When viewed using a magnetic resonance imaging (MRI) system, invasive materials inside the human body, in many cases, severely distort the MR image of human tissues. The degree of the MR image distortion increases in proportion not only to the difference in the susceptibility between the invasive material and the human tissue, but also to the intensity of the magnetic field induced by the MRI system. In this study, by blending paramagnetic Ti particles with diamagnetic graphite, we synthesized $Ti_{100-x}C_x$ composites that can reduce the artifact in the MR image under the high-strength magnetic field. Of the developed composites, $Ti_{70}C_{30}$ showed the magnetic susceptibility of ${\chi}=67.6{\times}10^{-6}$, which corresponds to 30% of those of commercially available Ti alloys, the lowest reported in the literature. The level of the MR image distortion in the vicinity of the $Ti_{70}C_{30}$ composite insert was nearly negligible even under the high magnetic field of 4.7 T. In this paper, we reported on a methodology of designing new structural materials for bio-applications, their synthesis, experimental confirmation and measurement of MR images.

• Bulletin of the Korean Chemical Society
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• v.18 no.10
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• pp.1061-1066
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• 1997

The complexes M(CO)4-1,2-(PPh2)2-1,2-C2B10H10 (M=Cr 2a, Mo 2b, W 2c) have been prepared in good yields from readily available bis-diphenylphosphino-o-carboranyl ligand, closo-1,2-(PPh2)2-1,2-C2B10H10 (1), by direct reaction with Group Ⅵ metal carbonyls. The infrared spectra of the complexes indicate that there is an octahedral disposition of chelate bis-diphenylphosphino-o-carboranyl ligand around the metal atom. The crystal structure of 2a was determined by X-ray diffraction. Complex 2a crystallizes in the monoclinic space group P21/n with cell parameters a = 12.2360(7), b = 17.156(1), c = 16.2040(6) Å, V = 3354.1(3) Å3, and Z =4. Of the reflections measured a total of 2514 unique reflections with F2 > 3σ(F2) was used during subsequent structure refinement. Refinement converged to R1 = 0.066 and R2 = 0.071. Structural studies showed that the chromium atom had a slightly distorted pseudo-octahedral configuration about the metal center with two phosphine groups of o-carborane occupying the equatorial plane cis-orientation to each other. These metal carbonyl complexes are rapidly converted to the corresponding metal carbene complexes, [(CO)3M=C(OCH3)(CH3)]-1,2-(PPh2)2-1,2-C2B10H10 (M= Cr 3a, Mo 3b, W 3c), via alkylation with methyllithium followed by O-methylation with CF3SO3CH3.

• Advances in materials Research
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• v.2 no.2
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• pp.77-91
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• 2013

High quality nanoparticles of neodymium barium niobium ($NdBa_2NbO_6$) perovskites have been synthesized using an auto ignition combustion technique for the first time. The nanoparticles thus obtained have been characterized by powder X-ray diffraction, thermo gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, Raman spectroscopy and transmission electron microscopy. UV-Visible absorption and photoluminescence spectra of the samples are also recorded. The structural analysis shows that the nano powder is phase pure with the average particle size of 35 nm. The band gap determined for $NdBa_2NbO_6$ is 3.9 eV which corresponds to UV-radiation for optical inter band transition with a wavelength of 370nm. The nanopowder could be sintered to 96% of the theoretical density at $1325^{\circ}C$ for 2h. The ultrafine cuboidal nature of nanopowders with fewer degree of agglomeration improved the sinterability for compactness at relatively lower temperature and time. During the sintering process the wide band gap semiconducting behavior diminishes and the material turns to a high permittivity dielectric. The microstructure of the sintered surface was examined using scanning electron microscopy. The striking value of dielectric constant ${\varepsilon}_r=43$, loss factor tan ${\delta}=1.97{\times}10^{-4}$ and the observed band gap value make it suitable for many dielectric devices.

• Korean Journal of Materials Research
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• v.31 no.9
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• pp.525-531
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• 2021

Carbon-encapsulated Ni catalysts are synthesized by an electrical explosion of wires (EEW) method and applied for CO₂ methanation. We find that the presence of carbon shell on Ni nanoparticles as catalyst can positively affect CO₂ methanation reaction. Ni@5C that is produced under 5 % CH₄ partial pressure in Ar gas has highest conversions of 68 % at 350 ℃ and 70 % at 400 ℃, which are 73 and 75 % of the thermodynamic equilibrium conversion, respectively. The catalyst of Ni@10C with thicker carbon layer shows much reduced activity. The EEW-produced Ni catalysts with low specific surface area outperform Ni catalysts with high surface area synthesized by solution-based precipitation methods. Our finding in this study shows the possibility of utilizing carbon-encapsulated metal catalysts for heterogeneous catalysis reaction including CO₂ methanation. Furthermore, EEW, which is a highly promising method for massive production of metal nanoparticles, can be applied for various catalysis system, requiring scaled-up synthesis of catalysts.

• Journal of Adhesion and Interface
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• v.22 no.1
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• pp.8-15
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• 2021

In this study, a polyol was prepared using Jeffamine D-400 as a propylene glycol-based diamine to impart flexibility to the urethane-modified epoxy, and a urethane-modified epoxy was synthesized using the polyol. Urethane-modified epoxy synthesized with existing Bisphenol A diglycidyl ether (BADGE) epoxy, a curing agent, and a curing accelerator are mixed to prepare an epoxy adhesive, and shear strength is measured by measuring adhesion strength. As a result, shear strength and shear elongation tended to increase. These results are due to the high crosslinking density. It is believed that it can be applied to structural adhesives that are restricted in use.

• Journal of the Korean Chemical Society
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• v.65 no.2
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• pp.93-105
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• 2021

Mononuclear Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Fe(III), Ru(III), and UO2(II) complexes of 2-hydroxy-4-(p-tolyldiazenyl)benzylidene)-2-(p-tolylamino)acetohydrazide (H2L) were prepared by direct method. The ligand and its complexes were isolated in solid state and characterized by analytical techniques such as elemental and thermal analyses, molar conductance, magnetic susceptibility measurements and spectroscopic techniques such as UV-Visible, IR, 1H-NMR and 13C-NMR. The spectral data indicated that the ligand acted as neutral/monobasic bidentate or monobasic/dibasic tridentate ligand bonded to the metal ions through the oxygen atom of ketonic or enolic carbonyl group, azomethine nitrogen atom and deprotonated/protonated phenolic oxygen atom forming either tetragonally distorted octahedral or octahedral. Antimicrobial activities of the ligand and its complexes were evaluated against Escherichia coli, Bacillus subtilis and Aspergillus niger by well diffusion method. The results of antifungal activity showed that the Fe(III) complex (10) exhibited higher antifungal against Aspergillus niger than the other complexes. However, the results of antibacterial activity revealed that Cu(II) complex (4) is the most active against Escherichia coli while the Cu(II) complex (5) and Fe(III) complex (10) exhibited higher antibacterial effect on Bacillus subtilis than the other complexes.

• Korean Journal of Materials Research
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• v.29 no.6
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• pp.356-362
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• 2019

$BaSiO_3:RE^{3+}$ (RE = Sm or Eu) phosphor powders with different concentrations of activator ions are synthesized using the solid-state reaction method. The effects of the concentration of activator ions on the structural, photoluminescent, and morphological properties of the barium silicate phosphors are investigated. X-ray diffraction data reveals that the crystal structure of all the phosphors, regardless of the type and the concentration of the activator ions, is an orthorhombic system with a main (111) diffraction peak. The grain particles agglomerate together to form larger clusters with increasing concentrations of activator ions. The emission spectra of the $Sm^{3+}$-doped $BaSiO_3$ phosphors under excitation at 406 nm consist of an intense orange band at 604 nm and three weak bands centered at 567, 651, and 711 nm, respectively. As the concentration of $Sm^{3+}$ increases from 1 to 5 mol%, the intensities of all the emission bands gradually increase, reach maxima at 5 mol% of $Sm^{3+}$ ions, and then decrease significantly with further increases in the $Sm^{3+}$ concentration due to the concentration quenching phenomenon. For the $Eu^{3+}$-doped $BaSiO_3$ phosphors, a strong red emission band at 621 nm and several weak bands are observed. The optimal orange and red light emissions of the $BaSiO_3$ phosphors are obtained when the concentrations of $Sm^{3+}$ and $Eu^{3+}$ ions are 5 mol% and 15 mol%, respectively.

• Journal of Microbiology and Biotechnology
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• v.29 no.8
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• pp.1288-1298
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• 2019

Bacterial ATP synthases drive ATP synthesis by a rotary mechanism, and play a vital role in physiology and cell metabolism. Corynebacterium glutamicum is well known as an industrial workhorse for amino acid production, and its ATP synthase operon contains eight structural genes and two adjacent genes, cg1360 and cg1361. So far, the physiological functions of Cg1360 (GenBank CAF19908) and Cg1361 (GenBank CAF19909) remain unclear. Here, we showed that Cg1360 was a hydrophobic protein with four transmembrane helices (TMHs), while no TMH was found in Cg1361. Deletion of cg1360, but not cg1361, led to significantly reduced cell growth using glucose and acetic acid as carbon sources, reduced F1 portions in the membrane, reduced ATP-driven proton-pumping activity and ATPase activity, suggesting that Cg1360 plays an important role in ATP synthase function. The intracellular ATP concentration in the ${\Delta}cg1360$ mutant was decreased to 72% of the wild type, while the NADH and NADPH levels in the ${\Delta}cg1360$ mutant were increased by 29% and 26%, respectively. However, the ${\Delta}cg1361$ mutant exhibited comparable intracellular ATP, NADH and NADPH levels with the wild-type strain. Moreover, the effect of cg1360 deletion on L-valine production was examined in the L-valine-producing V-10 strain. The final production of L-valine in the $V-10-{\Delta}cg1360$ mutant reached $9.2{\pm}0.3g/l$ in shake flasks, which was 14% higher than that of the V-10 strain. Thus, Cg1360 can be used as an effective engineering target by altering energy metabolism for the enhancement of amino acid production in C. glutamicum.