• Natural Product Sciences
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• v.4 no.3
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• pp.153-157
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• 1998

The aqueous ethanolic leaf extract of Ailanthus altissima was found to contain the new natural product, $luteolin\;7-O-{\beta}-(6"-galloylglucopyranoside)$, 13, along with fourteen known phenolic metabolites (1-12, 14 and 15). Structures of all compounds (1-15) were established by conventional methods of analysis and confirmed by FAB-MS, $^1H-\;and\;^{13}C-NMR$ spectral analysis.

• Journal of Microbiology and Biotechnology
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• v.27 no.4
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• pp.775-784
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• 2017

A neutral xylanase (CcXyn) was identified from Coprinus cinereus. It has a single GH10 catalytic domain with a basic amino acid-rich extension (PVRRK) at the C-terminus. In this study, the wild-type (CcXyn) and C-terminus-truncated xylanase ($CcXyn-{\Delta}5C$) were heterologously expressed in Pichia pastoris and their characteristics were comparatively analyzed with aims to examine the effect of this extension on the enzyme function. The circular dichorism analysis indicated that both enzymes in general had a similar structure, but $CcXyn-{\Delta}5C$ contained less ${\alpha}-helices$ (42.9%) and more random coil contents (35.5%) than CcXyn (47.0% and 32.8%, respectively). Both enzymes had the same pH (7.0) and temperature ($45^{\circ}C$) optima, and similar substrate specificity on different xylans. They all hydrolyzed beechwood xylan primarily to xylobiose and xylotriose. The amounts of xylobiose and xylotriose accounted for 91.5% and 92.2% (w/w) of total xylooligosaccharides (XOS) generated from beechwood by CcXyn and $CcXyn-{\Delta}5C$, respectively. However, truncation of the C-terminal 5-amino-acids extension significantly improved the thermostability, SDS resistance, and pH stability at pH 6.0-9.0. Furthermore, $CcXyn-{\Delta}5C$ exhibited a much lower $K_m$ value than CcXyn (0.27 mg/ml vs 0.83 mg/ml), and therefore, the catalytic efficiency of $CcXyn-{\Delta}5C$ was 2.4-times higher than that of CcXyn. These properties make $CcXyn-{\Delta}5C$ a good model for the structure-function study of $({\alpha}/{\beta})_8$-barrel-folded enzymes and a promising candidate for various applications, especially in the detergent industry and XOS production.

• Korean Journal of Materials Research
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• v.21 no.3
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• pp.180-185
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• 2011

This study is aimed to increase the activity of cathodic catalysts for PEMFCs(Polymer Electrolyte Membrane Fuel Cells). we investigated the temperature effect of 20wt% Pt/C catalysts at five different temperatures. The catalysts were synthesized by using chemical reduction method. Before adding the formaldehyde as reducing agent, process was undergone for 2 hours at the room temperature (RT), $40^{\circ}C$, $60^{\circ}C$, $80^{\circ}C$ and $100^{\circ}C$, respectively. The performances of synthesize catalysts are compared. The electrochemical oxygen reduction reaction (ORR) was studied on 20wt% Pt/C catalysts by using a glassy carbon electrode through cyclic voltammetric curves (CV) in a 1M H2SO4 solution. The ORR specific activities of 20wt% Pt/C catalysts increased to give a relative ORR catalytic activity ordering of $80^{\circ}C$ > $100^{\circ}C$ > $60^{\circ}C$ > $40^{\circ}C$ > RT. Electrochemical active surface area (EAS) was calculated with cyclic voltammetry analysis. Prepared Pt/C (at $80^{\circ}C$, $100^{\circ}C$) catalysts has higher ESA than other catalysts. Physical characterization was made by using X-ray diffraction (XRD) and transmission electron microscope (TEM). The TEM images of the carbon supported platinum electrocatalysts ($80^{\circ}C$, $100^{\circ}C$) showed homogenous particle distribution with particle size of about 2~3.5 nm. We found that a higher reaction temperature resulted in more uniform particle distribution than lower reaction temperature and then the XRD results showed that the crystalline structure of the synthesized catalysts are seen FCC structure.

• KSBB Journal
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• v.31 no.4
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• pp.263-269
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• 2016

For decades, the microorganisms in arctic soils have been newly discovered according to the climate change and global warming. In this study, the chemical structure of a lipid A molecule from Pseudomonas sp. strain PAMC 28615 which was newly discovered from arctic soils was characterized by mass spectrometric approaches such as matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and MALDI multi-stage tandem mass spectrometry (MS). First, lipopolysaccharide (LPS) from Pseudomonas sp. strain PAMC 28615 was extracted and subsequently hydrolyzed to obtain the lipid A. The parent ion peak at m/z 1632 was determined by MALDI-TOF MS, which also can validate our lipid A purification method. For detailed structural determination, we performed the multiple-stage tandem mass analysis ($MS^4$) of the parent ion, and subsequently the abundant fragment ions in each MS stage are tested. The fragment ions in each MS stage were produced from the loss of phosphate groups and fatty acyl groups, which could be used to confirm the composition or the position of the lipid A components. Consequently, the mass spectrometry-based lipid A profiling method could provide the detail chemical structure of lipid A from the Pseudomonas sp. strain PAMC 28615 as an arctic bacterium from the frozen arctic soil.

• Korean Chemical Engineering Research
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• v.45 no.4
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• pp.410-413
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• 2007

The effect of internal donor(ID) in the heterogeneous Ziegler-Natta catalyst on the ethylene-1-butene copolymerization and the molecular structure of the resulting copolymer was investigated. $SiO_2$-supported $TiCl_4$ catalysts having ID/Ti molar ratio of 0.5 were prepared with ethyaluminium dichloride, magnesium alkyl, 2-ethyl-1-hexanol and $TiCl_4$. Three different IDs were employed such as ethylbenzoate(EB), diisobuylphthalate(DIBP) and dioctylphthalate(DOP). ID-added catalyst showed a larger fraction of Ti(+3) compared to that of no ID-added catalyst. The EB-added catalyst showed the highest activity in copolymerization. Xylene soluble value decreased by more than 50 % with ID-added catalysts compared to that of no ID-added catalyst. Crystaf analysis showed the chemical compositional distribution of PE copolymer was improved in the case of DIBP-added catalyst significantly. It could be explained that the presence of ID could make more even active sites and block the non-stereospecific active sites.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2535-2541
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• 2009

Prebiotic isomaltooligosaccharide preparations contain $\alpha$-D-glucooligosaccharides comprising isomaltooligosaccharides (IMOs) and non-prebiotic maltooligosaccharides (MOs). They are both glucose oligosaccharides characterized by their degree of polymerization (DP) value (from 2 to $\sim$10), linkages types and positions (IMOs: $\alpha$-(1$\rightarrow$2, 3, 6 and in a lower proportion internal 1$\rightarrow$4) linkages, MOs: α-(1$\rightarrow$4) linkages). Their structure is the key factor for their prebiotic potential. In order to determine and elucidate the exact structure of unknown IMOs and MOs, unambiguous assignments of $^{13}C$ and $^1H$ chemical shifts of commercial standards, representative of IMOs and MOs diversity, have been determined using optimized standard one and two-dimensional experiments such as $^1H$ NMR, $^{13}C$ NMR, APT and ${^1}H-{^1}H$ COSY, TOCSY, NOESY and <$^1H-{^{13}}C$ heteronuclear HSQC, HSQC-TOCSY, and HMBC. Here we point out the differential effect of substitution by a glucose residue at different positions on chemical shifts of anomeric as well as ring carbons together with the effect of the reducing end configuration for low DP oligosaccharides and diasteroisotopic effect for H-6 protons. From this study, structural $^{13}C$ specific spectral features can be identified as tools for structural analysis of isomaltooligosaccharides.

• Journal of Hydrogen and New Energy
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• v.33 no.4
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• pp.372-382
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• 2022

In this study, anion exchange membranes were prepared by synthesizing the main chain into a poly(arylene ether) (PAE) structure, and the structures capable of improving the physical and chemical stability of the membrane by introducing a heterocyclic quaternary ammonium functional groups were studied. The chemical structure and thermal properties of the prepared polymer were confirmed by ¹H-NMR, FT-IR, TGA, and DSC, and surface analysis was performed through AFM measurement. Additionally, dimensional stability and chemical properties was studied by measuring water uptake and swelling ratio, IEC and ionic conductivity. At 90℃, the quaternized poly(arylene ether) (QPAE)/1-methylpiperidine (MP) membrane exhibited the highest ionic conductivity of 27.2 mS cm^-1, while the QPAE/1-methylimidazole (MI) membrane and QPAE/1-methylmorpholine (MM) membrane exhibited values of 14.5 mS cm^-1 and 11.5 mS cm^-1, respectively. In addition, the prepared anion exchange membrane exhibited high chemical stability in alkaline solution.

• Clean Technology
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• v.16 no.4
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• pp.297-303
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• 2010

Effect of interconnect structure on the cell performance in anode-supported tubular solid oxide fuel cell (SOFC) has been investigated in this study, employing the Fluent CFD solver. For the robust and reliable theoretical analysis corroborating experimental results, it is of great importance to elucidate the role of interconnect which is electrically connected with electrodes on the cell characteristics. From the fact that the thin interconnect provides the enhanced cell performance, it is revealed that the interconnect thickness is a key parameter that is able to effectively control the ohmic resistance. Under the constant thickness condition, the cell performance does not considerably change with the variation of interconnect width. This is because the current passage along with circumferential direction is not effectively altered by the change of interconnect width in tubular SOFC system.

• Economic and Environmental Geology
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• v.27 no.6
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• pp.507-521
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• 1994

Bentonite occurs in the Janggi Conglomerate of Tertiary age and consists mainly of montmorillonite with Mg as predominant interlayer cations. The bentonite was reacted with various concentrations of sulfuric acid (0.8~1.5M) for various reaction time (1-10h) at $103^{\circ}C$. Cation exchange capacity, exchangeable cations, surface area and solid acidity of the original bulk and acid activated bentonites were measured. Chemical analysis, X-ray diffraction, differential thermal analysis and infrared spectroscopy were used to characterize the changes in structure and properties of the acid activated bentonite. The dissolution of octahedral cations occurs not only from the edge of the clay platelets but also throughout the whole clay structure creating vacant octahedral sites. These lattice defects are created by $H^+$ diffused into the smectite layers. The cations leached possibly from the octahedral sheets are adsorbed on the interlayer exchange sites. They are exchanged with hydronium ions again by stronger acid attack. These reactions create wedge-shaped pores resulting in the increase of the surface area and the changes the morphology in the lattice structure.

• Archives of Pharmacal Research
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• v.16 no.2
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• pp.134-139
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• 1993

The molecular structure of acemetacin, 1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid carboxymethyl ester, was determined by single cystal X-ray diffraction analysis. The compound was recrystallized from a mixture of acetone and water in triclinic, space group P1, with a=7.796(1), b=10.245(2), c=13.542(3)$\AA,\;\alpha=97.35(1),\;\beta=96.34(1),\;\gamma=107.06(1)^\circ$, and Z=2. The calculated density is 1.422; the observed value is $1.42\;g/cm^3$. The structure was solved by the direct method and refined by full matrix least-squares procedure to the final R value of 0,037 for 2960 independent reflections. There are water molecules, which are thought to be co-crystallized during the evaporation procedure, with the ratio of one water per compound molecule in the crystal. The conformation of the compound is found to be very similar to that of indomethacin. The molecules are stabilized by three O-H.....O type intermolecular hydrogen bonds between the oxygen of water molecule and those of the compound.