• Analytical Science and Technology
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• v.21 no.4
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• pp.245-258
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• 2008

Five triterpenic acids as marker compounds were extracted and isolated from Prunellae Spica by column chromatography and reversed-phase high-performance liquid chromatography (HPLC), and their purity was determinated by HPLC (purity ${\geq}90%$). Molecular weight and elemental compositions of the five marker compounds were determined by fast atom bombardment high-resolution mass spectrometry (FAB-HRMS). The structural determination of the five marker compounds was carried out fast atom bombardment collision-induced dissociation tandem mass spectrometry (FAB-CID-MS/MS). The collision-induced dissociation (CID) of protonated molecules $[M+H]^+$ and deprotonated molecules $[M-H]^-$ produced diverse product ions due mainly to retro Diels-Alder reaction (RDA), dehydration and decarboxylation. Moreover, the CID-MS/MS spectra of the $[M-H]^-$ ions were observed charge-remote fragmentation (CRF) patterns. On the basis of interpretation of CID-MS/MS spectra, structural elucidation of triterpenic acids isolated from Prunellae Spica was clearly performed.

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.274-278
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• 2003

New banana-shaped achiral compounds, 1,3-phenylene bis [4-{4-(alkenyloxy) phenyliminomethyl}benzoate]s were synthesized by varying the length of alkenyl group; their ferroelectric properties are described. The smectic mesophases, including a switchable chiral smectic C $(Sm\;C^*)$ phase, were characterized by differential scanning calorimetry, polarizing optical microscopy and triangular wave method. The presence of vinyl groups at the terminals of linear side wings in the banana-shaped achiral molecules containing Schiff's base mesogen induced a decrease in melting temperature and formation of the switchable $(Sm\;C^*)$ phase in the melt. The smectic phases having the octenyloxy group such as $(CH_2)_6CH=CH_2$ showed ferroelctric switching, and their values of spontaneous polarization on reversal of an applied electric field were 120 nC/cm² (X=H) and 225 nC/ cm² (X=F), respectively. We could obtain ferroelectric phases by controlling the number of carbon atom in alkenyloxy chain of a bent-core molecule.

• Analytical Science and Technology
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• v.10 no.5
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• pp.315-324
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• 1997

The retention behaviors of 16 PAHs and 4 nitro-PAHs were studied with several parameters involved numbers of carbon atoms, F factor, aqueous solubility, L/B ratio, and numbers of interfering hydrogen atom pairs on the chemical structures of PAHs by using reversed-phase liquid chromatography/diode array detection method (RPLC/DAD) and gradient elution method. It was obtain that the log k' for most of PAHs with increasing the number of carbon and the F factor in their molecules. Chromatographic retention of PAH isomers and nitro-PAHs were examined with aqueous solubility, L/B ratio and number of interfering hydrogen atom pairs. As a result of comparison with these factors and retention times, it was found that those solutes having larger aqueous solubilities and greater L/B ratios were retained longer on stationary phase. This tendency was also occured in the molecules having the more number of interfering hydrogen atom pairs. Detection limits of PAHs which were obtained with three times measurements by RPLC/DAD were in the range of 100~500ng/mL and method detection limit(MDL) for water sample were in the range of 0.1~0.5ng/mL.

• Natural Product Sciences
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• v.21 no.2
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• pp.111-121
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• 2015

The root of Panax ginseng, is a Korea traditional medicine, which is used in both raw and processed forms due to their different pharmacological activities. As part of a continued chemical investigation of ginseng, the focus of this research is on the isolation and identification of compounds from Panax ginseng root by open column chromatography, medium pressure liquid chromatography, semi-preparative-high performance liquid chromatography, Fast atom bombardment mass spectrometric, and nuclear magnetic resonance. Dammarane-type triterpenoid saponins were isolated from Panax ginseng root by open column chromatography, medium pressure liquid chromatography, and semi-preparative-high performance liquid chromatography. Their structures were identified as protopanaxadiol ginsenosides [gypenoside-V (1), ginsenosides-Rb1 (2), -Rb2 (3), -Rb3 (4), -Rc (5), and -Rd (6)], protopanaxatriol ginsenosides [20(S)-notoginsenoside-R2 (7), notoginsenoside-Rt (8), 20(S)-O-glucoginsenoside-Rf (9), 6-O-[$\alpha$-L-rhamnopyranosyl(1$\rightarrow$2-$\beta$-D-glucopyranosyl]-20-O-$\beta$-D-glucopyranosyl-$3\beta$,$12\beta$, 20(S)-dihydroxy-dammar-25-en-24-one (10), majoroside-F6 (11), pseudoginsenoside-Rt3 (12), ginsenosides-Re (13), -Re5 (14), -Rf (15), -Rg1 (16), -Rg2 (17), and -Rh1 (18), and vinaginsenoside-R15 (19)], and oleanene ginsenosides [calenduloside-B (20) and ginsenoside-Ro (21)] through the interpretation of spectroscopic analysis. The configuration of the sugar linkages in each saponin was established on the basic of chemical and spectroscopic data. Among them, compounds 1, 8, 10, 11, 12, 19, and 20 were isolated for the first time from P. ginseng root.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.21-21
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• 2011

A series of Quasi-Elastic Neutron Scattering (QENS) experiments helps us to understand the single-particle (hydrogen atom) dynamics of a globular protein and its hydration water and strong coupling between them. We also performed Molecular Dynamics (MD) simulations on a realistic model of the hydrated hen-egg Lysozyme powder having two proteins in the periodic box. We found the existence of a Fragile-to-Strong dynamic Crossover (FSC) phenomenon in hydration water around a protein occurring at TL=$225{\pm}5K$ by analyzing Intermediate Scattering Function (ISF). On lowering of the temperature toward FSC, the structure of hydration water makes a transition from predominantly the High Density Liquid (HDL) form, a more fluid state, to predominantly the Low Density Liquid (LDL) form, a less fluid state, derived from the existence of a liquid?liquid critical point at an elevated pressure. We showed experimentally and confirmed theoretically that this sudden switch in the mobility of the hydration water around a protein triggers the dynamic transition (so-called glass transition) of the protein, at a temperature TD=220 K. Mean Square Displacement (MSD) is the important factor to show that the FSC is the key to the strong coupling between a protein and its hydration water by suggesting TL${\fallingdotseq}$TD. MD simulations with TIP4P force field for water were performed to understand hydration level dependency of the FSC temperature. We added water molecules to increase hydration level of the protein hydration water, from 0.30, 0.45, 0.60 and 1.00 (1.00 is the bulk water). These confirm the existence of the FSC and the hydration level dependence of the FSC temperature: FSC temperature is decreased upon increasing hydration level. We compared the hydration water around Lysozyme, B-DNA and RNA. Similarity among those suggests that the FSC and this coupling be universal for globular proteins, biopolymers.

• Journal of the Korean Chemical Society
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• v.42 no.4
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• pp.443-448
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• 1998

The thermodynamic parameters for the interaction of metal ions with dibenzo-16-crown-5 and its derivatives have been determined by solution calorimetry in methanol at 25$^{\circ}C$. Thermodynamic properties of log K, ${\Delta}H$, and $T{\Delta}S$ have been determined for the complexation of metal cations by dibenzo-16-crown-5 and its derivatives. Dibenzo-16-crown-5 and its derivatives have been studied as metal cations carrier in bulk liquid membrane (BLM) and supported liquid membrane (SLM) system. $Ag^+$ has been much more transported using dibenzo-16-crown-5 derivatives as carriers and several other metal cations have been small transported using carrier in BLM and SLM system. Ligand structure, the length of side arm, donor atom, stability constant, and carrier concentration are also important parameters in the transport of cations.

• Journal of the Korean Chemical Society
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• v.48 no.5
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• pp.499-503
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• 2004

We designed and synthesized compounds which have negative dielectric anisotropy (N type) for VA-LCD mode. Due to the large dipole moments toward the minor axis of molecule and anisotropy of polarizability, they can be used as N type LC. F atom and NCS group and propyl group were introduced as substituents on bicyclohexylbenzene core unit and alkyl chains (propyl~heptyl) were introduced on terminal part. All of the synthesized compounds showed negative dielectric anisotropy as expected.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.445-448
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• 2002

New banana-shaped achiral compounds, 1,3-phenylene bis [4-{4-(7-octenyloxy)phenyliminomethyl}benzoate](PBOEB), 1,3-phenylene bis [4-{3-fluoro-4-(7-octenyloxy)phenyliminomethyl}benzoate] (PBFOEB), 1,3-phenylene bis [4-{4-(10-undecyloxy)phenyliminomethyl}benzoate](PBEUB), and 1,3phenylene bis [4-{3-fluoro-4-(10-undecyloxy)phenyliminomethyl}benzoate](PBFEUB) were obtained by general synthetic methods. PBOEB and PBFOEB having the octenyloxy groups such as $-(CH_2)_6CH=CH_2$ showed ferroelectric switching, and their values of spontaneous polarization on reversal of an applied electric field were 120 nC/$cm^2$ and 225 nC/$cm^2$, respectively. PBEUB and PBFEUB having the undecyloxy groups such as $-{CH_2)_9CH=CH_2$ showed antiferroelectric switching, and their values of spontaneous polarization on reversal of an applied electric field were 120 nC/$cm^2$ and 140 nC/$cm^2$, respectively. We could obtain ferroelectric and antiferroelectric phases by controlling the number of carbon atom in alkenyloxy chains of bent-core molecules.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.237-240
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• 2002

Micro catalytic reactors are alternative propulsion device that can be used on a nano satellite. When used with a monopropellant, $H_2O_2$, a micro catalytic reactor needs only one supply system as the monopropellant reacts spontaneously on contact with catalyst and releases heat without external ignition, while separate supply lines for fuel and oxidizer are needed for a bipropellant rocket engine. Additionally, $H_2O_2$ is in liquid phase at room temperature, eliminating the burden of storage for gaseous fuel and carburetion of liquid fuel. In order to design a micro catalytic reactor, an appropriate catalyst material must be selected. Considering the safety concern in handling the monopropellants and reaction performance of catalyst, we selected hydrogen peroxide at volume concentration of 70% and perovskite redox catalyst of lantanium cobaltate doped with strondium. Perovskite catalysts are known to have superior reactivity in reduction-oxidation chemical processes. In particular, lantanium cobaltate has better performance in chemical reactions involving oxygen atom exchange than other perovskite materials. In the present study, a process to prepare perovskite type catalyst, $La_{0.8}Sr_{0.2}CoO_3$, and measurement of its propellant decomposition performance in a test reactor are described.

• Journal of Welding and Joining
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• v.20 no.5
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• pp.93-98
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• 2002

The effect of bonding misfit on single crystallization of transient liquid phase (TLP) bonded joints of single crystal superalloy CMSX-2 was investigated using MBF-80 insert metal. The bonding misfit was defined by (100) twist angle (rotating angle) at bonded interface. TLP bonding of specimens was carried out at 1523K for 1.8ks in vacuum. The post-bond heat treatment consisted of the solution and sequential two step aging treatment was conducted in the Ar atmosphere. The crystallographic orientation analysis across the TLP bonded joints was conducted three dimensionally using the electron back scattering pattern (EBSP) method. EBSP analyses f3r the bonded and post bonded heat treated specimens were conducted. All bonded joints had misorientation centering around the bonded interface for as-bonded and post-bond heat treated specimens with rotating angle. The average misorientation angle between both solid phases in bonded interlayer was almost identical to the rotating angle at bonded interface. HRTEM observation revealed that the atom arrangement of both solid phases in bonded interlayer was quite different across the bonded interface. It followed that grain boundary was formed in bonded interface. It was confirmed that epitaxial growth of the solid phase occurred from the base metal substrates during TLP bonding and single crystallization could not be achieved in joints with rotating angle.