• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.355-362
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• 2009

The chemical modification of multi-wall carbon nanotubes (MWNTs) is an emerging area in material science. In the present study, hydroxyl functionalized oxovanadium(IV) Schiff-base; N,N'-bis(4-hydroxysalicylidene)-ethylene-1, 2-diamineoxovanadium(IV), [VO($(OH)_2$-salen)]; has been covalently anchored on modified MWNTs. The new modified MWNTs ([VO($(OH)_2$-salen)]-MWNTs]) have been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron (XPS), UV-Vis, Diffuse reflectance (DRS), FT-IR spectroscopy and elemental analysis. The analytical data indicated a composition corresponding to the mononuclear complex of tetradentate Schiff-base ligand. The characterization of the data showed the absence of extraneous complex, retention of MWNTs and covalently anchored on modified MWNTs. Liquid-phase oxidation of cyclohexane with $H_2O_2$ to a mixture of cyclohexanone, cyclohexanol and cyclohexane-1,2-diol in $CH_3$CN have been reported using oxovanadium(IV) Schiff-base complex covalently anchored on modified MWNTs as catalysts. This catalyst is more selective toward cyclohexanol formation.

• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.136-138
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• 2005

High-performance frontal analysis (HPFA) was used for the determination of the binding constant of Sibuprofen to human serum albumin (HSA). This experiment was based on an Inertsil 100 Diol 5 column and sodium phosphate buffer (pH 7.4 and ionic strength of 0.17) as the mobile phase. The mixture of S-ibuprofen and HSA (70 $\mu$M) solution were directly injected into the HPFA column. An injection volume of 200 $\mu$L and a “estricted injection”method were applied to ensure the drug to be eluted as a zonal peak with a plateau. The unbound drug concentration was calculated from the peak height of the zonal peak. Scatchard analysis was used for evaluation of the binding constant (K) and binding affinity (nK) of S-ibuprofen to HSA, and the results were K = 2.833 ${\times}$ 10$^4$ [L mol$^{-1}$], nK = 4.935 ${\times}$ 10$^4$ [L mol$^{-1}$], respectively.

• Bulletin of the Korean Chemical Society
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• 제24권10호
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• pp.1475-1477
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• 2003

Three monoterpene glucosides (1-3), including one new compound (3), have been isolated from the methanol extract of Portulaca oleracea. Structures of these compounds were determined to be (3S)-3-O-( ${\Beta}$-Dglucopyranosyl)-3,7-dimethylocta-1,6-dien-3-ol (1), (3S)-3-O-( ${\beta}$-D-glucopyranosyl)-3,7-dimethylocta-1,5-dien-3,7-diol (2) and (3S)-3-O-( ${\beta}$-D-glucopyranosyl)-3,7-dimethyl-7-hydroperoxyocta-1,5-dien-3-ol (3), respectively, by a combination of spectral analyses. Their stereochemistries were established by measurement of NOE and vicinal proton-proton coupling constants as well as comparisons of spectral data with those of previously related compounds.

• Elastomers and Composites
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• 제50권4호
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• pp.297-303
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• 2015

Ammonium polyphosphate-polyurethane foam composite (APP-PUF) was prepared from poly(adipate)diol/ammonium polyphosphate composite (f = 2), polyether polyol (f = 4.6), and PMDI (f = 2.5). As a blowing agent, $H_2O$ was used at various concentrations. The thermal decomposition behavior, morphology, closed-cell content, and density of APP-PUF were characterized. At the $H_2O$ concentrations lower than 3.5 php, the cell size of pure polyurethane foams (PUF) and APP-PUFs were close each other. As the $H_2O$ concentration became greater than 5.0 php, the cell size of the PUFs greatly increased compared to that of APP-PUFs. Addition of 1.5~1.9 wt% ammonium polyphosphate to the PUFs greatly enhanced the thermal stability of the PUFs, so 50 wt% residual temperature of APP-PUFs increased to $380{\sim}488^{\circ}C$, which were $30{\sim}70^{\circ}C$ higher than those of the PUFs. Thermal stability of the PUFs and APP-PUFs increased with $H_2O$ content and then decreased once $H_2O$ content exceeded 5 php.

• 약학회지
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• 제36권2호
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• pp.129-136
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• 1992

The effects of ginseng saponins, gypsophila saponin, sodium dodecyl sulfate(SDS), and Triton X-100 on membrane $K^+-dependent$ phosphatase activity which is lipid dependent and represents dephosphorylation step of the complete Na+, $K^+-ATPase$ reaction were investigated in this study to elucidate whether the effects of ginseng saponins are due to the detergent action, using sarcolemma enriched preparation isolated from dog ventricle. $Na^+$, $K^+-ATPase$ and $K^+-dependent$ phosphatase activities of cardiac sarcolemma were about $143\;{\mu}mol$ Pi/mg protein/hr and $34\;{\mu}mol$ p-nitrophenol/mg protein/hr, respectively. While ginseng saponins (triol>total>diol) inhibited $K^+-dependent$ phosphatase activity, gypsophila saponin, and low dose of SDS($0.4\;{\mu}g/{\mu}g$ protein), and Triton X-100 ($0.6\;{\mu}g/{\mu}g$ protein) increased the enzyme activity, indicating disruptive effect of detergents on membrane barriers. The activating effect of low doses of Triton X-100 on membrane $K^+-dependent$ phosphatase appeared at concentration decreasing light scattering. However, the inhibitory effect of ginseng saponin appeared before a decrease in light scattering. These results suggest that low concentrations of ginseng saponins inhibit the membrane $K^+-dependent$ phosphatase by interacting directly with enzyme before membrane disruption.

• 제어로봇시스템학회논문지
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• 제11권10호
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• pp.857-863
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• 2005

A yeast strain utilizing styrene epoxide as a sole carbon and energy source was isolated from soil samples for the production of enantiopure of styrene epoxide by kinetic resolution. The strain, identified as a Rhodosporidium toruloides SJ-4, expressed an epoxide hydrolase which preferentially converted (R)-styrene epoxide into the corresponding diol. A maximum activity of 135 U/L was observed when biomass (dry cell mass) reached 6.7 g/L at 21 h of batch culture. Under the partially optimized reaction conditions ($35^{\circ}C$ and pH 8.0), the optically pure (S)-styrene epoxide was obtained with the yield of 21% when the initial substrate concentration was 100 mM. The reaction was completed at 9 h.

• 대한화학회지
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• 제57권3호
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• pp.311-315
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• 2013

The geometry structures of hexa-coordinated [NiLX]X complexes ($X=Cl^-,\;Br^-,\;I^-$) {L = 8,9,18,19-tetrahydro-7H,17H-dibenzo[f,o] [1,5,9,13]dioxadiaza cyclohexadecine-8,18-diol} are optimized by density functional theory (DFT) using B3LYP/LANL2DZ. The calculated geometric parameters are in good agreement with the corresponding experimental values. Calculation results about these complexes show that dipole moment decreases, and the energy levels of HOMOs descend from iodo-complex to chloro-complex. The energy levels of HOMOs descend gently from iodo-complex to chloro-complex, while the energy levels of LUMOs in the present complexes are almost similar; therefore the energy gapes between HOMOs and LUMOs increased from iodo-complex to chloro-complex.

• Archives of Pharmacal Research
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• 제19권6호
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• pp.551-553
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• 1996

A genuine dammarane glycoside, named ginsenoside $Rg_{5}$, has been isolated by repeated column chromatography and preparative HPLC from the MeOH extract of Korean red ginseng (Panax ginseng C.A. Meyer). The chemical structure of ginsenoside$ Rg_{5}$ was determined as $3-O-[{\beta}-D-glucopyranosyl (1{\rightarrow}2)-{\beta}-D-glucopyranosyl]$ dammar-20(22), $24-diene-3{\beta},12{\beta}-diol$ by spectral and chemical methods. The stereostructure of a double bond at C-20(22) of ginsenoside $Rg_{5}$ was characterized as (E) from the chemical shift of C-21 in the $^{13}C-NMR $and a NOESY experiment in the $^{1}H-NMR$.

• Fibers and Polymers
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• 제5권4호
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• pp.289-296
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• 2004

The kinetic parameters, including the activation energy E, the reaction order n, and the pre-exponential factor Z, of the degradation of the copolymers based on the poly(L-lactide) (PLLA) or poly(p-dioxanone-co-L-lactide) (PDO/PLLA) and diol-terminated poly(ethylene glycol) (PEG) segments have been evaluated by the single heating methods of Friedman and Freeman-Carroll. The experimental results showed that copolymers exhibited two degradation steps under nitrogen that can be ascribed to PLLA or PDO/PLLA and PEG segments, respectively. However, copolymers exhibited almost single degradation step in air. Although the values of initial decomposition temperature were scattered, copolymers showed the lower maximum weight loss rate and degradation-activation energy in air than in nitrogen whereas the higher value of temperature at the maximum rate of weight loss was observed in air.

• Membrane and Water Treatment
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• 제6권4호
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• pp.277-292
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• 2015

The extraction of lactic acid by an emulsion liquid membrane (ELM), in batch and continuous mode, has been reported. On the basis of preliminary experiments, the optimum composition of the organic phase (membrane) is determined. When the SPan 80 is used as surfactant, the emulsion breakage exceeds 50%, but only 10% is obtained when the ECA4360 is used. The effects of surfactant, carrier and solute concentrations, phase volume ratio, and stirring speed on the extraction yield were examined and optimized. Surfactant, carrier and diluent used were ECA4360, trilaurylamine (TLA) and dodecane, respectively; 2-ethylhexane-1,3-diol (EHD) is used as a co-surfactant. Under optimal conditions, emulsion breaking is very low and the swelling is kept at its lowest level. Under the pH conditions of fermentation medium, the extraction yield is lower. A mixer-settler continuous system was used for testing these conditions. The residence time, the number of extraction stages and the stability of the emulsion were studied and optimized. The extraction yield obtained exceeds 90%.