• YAKHAK HOEJI
• /
• v.54 no.4
• /
• pp.288-294
• /
• 2010

Three dimensional quantitative-structure relationships (3D-QSARs) models between structures of phenoxy, phenylthio or benzyloxy substituted quinolone analogues and their antitrypanosomal activity against Chagas disease (Trypanosoma cruzi) were derived and discussed quantitatively using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) methods. The optimized CoMFA 1 model ($q^2$=0.528 and $r^2$=0.964) showed the best statistical results. According to the optimized CoMFA 1 model, the antitrypanosomal activities were dependent on the steric (60.0%) and electrostatic (36.2%) factors of quinolone derivatives. From the contour maps, it is predicted that the activity will be increased when sterically favored groups were located in $R_4$ and $R_5$ position and sterically disfavored groups were located in $R_2$ position. Also, the positively charged groups on $R_2$ would be able to increase the antitrypanosomal activities.

• Korean Journal of Materials Research
• /
• v.20 no.9
• /
• pp.478-482
• /
• 2010

A series of molecular dynamic (MD), finite element (FE) and ab initio simulations are carried out to establish suitable modeling schemes for the continuum-based analysis of aluminum matrix nanocomposites reinforced with carbon nanotubes (CNTs). From a comparison of the MD with FE models and inferences based on bond structures and electron distributions, we propose that the effective thickness of a CNT wall for its continuum representation should be related to the graphitic inter-planar spacing of 3.4${\AA}$. We also show that shell element representation of a CNT structure in the FE models properly simulated the carbon-carbon covalent bonding and long-range interactions in terms of the load-displacement behaviors. Estimation of the effective interfacial elastic properties by ab initio simulations showed that the in-plane interfacial bond strength is negligibly weaker than the normal counterpart due to the nature of the weak secondary bonding at the CNT-Al interface. Therefore, we suggest that a third-phase solid element representation of the CNT-Al interface in nanocomposites is not physically meaningful and that spring or bar element representation of the weak interfacial bonding would be more appropriate as in the cases of polymer matrix counterparts. The possibility of treating the interface as a simply contacted phase boundary is also discussed.

• Macromolecular Research
• /
• v.15 no.4
• /
• pp.324-329
• /
• 2007

An octa-functional alkoxyamine initiator, with the 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO) free radical, was synthesized based on resorcinarene, with its efficiency to initiate the nitroxide-mediated free radical copolymerization of styrene and methyl methacrylate (MMA) described. A difunctional analogue of this initiator was also synthesized, using resorcinol as the core molecule. The structures of the resulting initiators were confirmed by homolysis studies based on electron spin resonance spectroscopy and molecular modeling. The polymerization behavior and characteristics of the polymers obtained using these two initiators were also compared. Well-defined star-shaped and linear random copolymers, with low polydispersities and controlled molecular weights, were prepared. The efficiencies of these initiators towards copolymerization, as well as the parameters permitting the formation of well-defined polymers, were also investigated. The reactivity ratios were $r_a=0.42(a=styrene)\;and\;r_b=0.33(b=MMA)$ for the octa-functional initiator system and $r_a=0.45\;and\;r_b=0.39$ for the difunctional initiator system.

• Korean Journal of Optics and Photonics
• /
• v.21 no.4
• /
• pp.161-167
• /
• 2010

We suggest an effective expression of transmission coefficients between uniaxial anisotropic media. To study the transmission of oblique incident light by stratified anisotropic planar structures, we included an imaginary isotropic layer sandwiched between those anisotropic media, and then considered multiple reflection within the imaginary layer. The adequacy of this expression is confirmed by comparing the polarization analysis of light passing through the anisotropic medium and the multi.layered anisotropic media.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.8
• /
• pp.2158-2162
• /
• 2010

Studies on the molecular construction and structures of $M(NO_3)_2$ (M = Cu(II), Ni(II)) complexes with 1,2-bis(dimethyl-3-pyridylsilyl)ethane (L) have been carried out. Formation of each molecular skeleton appears to be primarily associated with a suitable combination of bidentate N-donors of L and coordinating nature of octahedral metal(II) ions: [$Cu(NO_3)_2(L)_2$] yields a 2-dimensional sheet structure consisting of 44-membered $Cu_4L_4$ skeleton whereas $[Ni(L)_2(H_2O)_2](NO_3)_2$ produces an interpenetrated 3-dimensional structure consisting of 66-membered cyclohexanoid ($M_6L_6$) skeleton. The Cu(II) ion prefers nitrate whereas the Ni(II) ion prefers water molecules as the fifth and the sixth ligands.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.8
• /
• pp.2219-2222
• /
• 2010

A density functional theory (DFT) study of $CO_2$ adsorption on barium oxide (BaO) adsorbents is conducted to understand the chemical activity of the oxygen site on the BaO (100) surface. This study evaluated the adsorption energies and geometries of a single $CO_2$ molecule and a pair of $CO_2$ molecules on the BaO (100) surface. A quantum calculation was performed to obtain information on the molecular structures and molecular reaction mechanisms; the results of the calculation indicated that $CO_2$ was adsorbed on BaO to form a stable surface carbonate with strong chemisorption. To study the interactive $CO_2$ adsorption on the BaO (100) surface, a pair of $CO_2$ molecules was bound to neighboring and distant oxygen sites. The interactive $CO_2$ adsorption on the BaO surface was found to slightly weaken the adsorption energy, owing to the interaction between $CO_2$ molecules.

• Korean Journal of Crystallography
• /
• v.10 no.1
• /
• pp.1-8
• /
• 1999

Two conformational isomers of p-tert-butylcalix[4]arene hexanoate were prepared from the reaction of-p-tert-butylcalix[4]arene and hexanoly chloride in the presence of AlCl3 in CH2Cl2 and their structures were determined by NMR spectra and X-ray diffraction as a cone and a 1,3-alternate conformer, respectively. The crystal of cone conformer (C68H96O8·(CH3)2CO) is triclinic, P, a=15.066(1) , b=16.063(1) , c=16.365(1) , α=79.75(2)o, β=109.95(2)o, γ=80.32(0)o, V=3602.7(4) 3, Z=2. The intensity data were collected on Simens SMART diffractometer/CCD area detector. The structure was solved by direct method and refined by least-squares calculations to a final R value of 0.144 for 4638 observed reflections. The molecular conformation is distorted symmetric cone with the flattening A and D phenyl rings. The crystal of 1,3-alternate conformer (C68H96O8·2CHCl3) is orthorhombic, Pca21, a=34.586(5) , b=10.207(3) , c=20.394(4) , V=7199(3) 3, Z=4. The intensity data were collected on an Enraf-Noninus CAD-4 Diffractometer with a graphite monochromated Mo-K radiation. The structure was solved by direct method and refined by least-squares calculations to a final R value of 0.152 for 2241 observed reflections. The molecule has a pseudo mirror symmetric 1,3-alternate conformation.

• Journal of the Korea Convergence Society
• /
• v.9 no.6
• /
• pp.89-98
• /
• 2018

To confirm the feasibility as raw materials for cosmetic formulation, ethanol, n-hexane, ethylacetate and normal butyl alcohol were extracted from 1kg of Ginko leaves. Ultimately, investigated chemical structure and physicochemical properties of ginkgetin and isoginkgetin. The purity of those two components have been evaluated higher than 99%. They are isomers with molecular weight as 566 and a molecular formular, $C_{32}H_{22}O_{10}$. Flavonoid's frame and NMR spectrum exhibited the existence of aromatic proton and the proper ratio of the carbon, which were expected structures exactly corresponded to the reported references.

• Parasites, Hosts and Diseases
• /
• v.45 no.3
• /
• pp.181-190
• /
• 2007

The phylogenie relationships existing among 14 parasitic Platyhelminthes in the Republic of Korea were investigated via the use of the partial 28S ribosomal DNA (rDNA) D1 region and the partial mitochondrial cytochrome c oxidase subunit 1 (mCOI) DNA sequences. The nucleotide sequences were analyzed by length, G + C %, nucleotide differences and gaps in order to determine the analyzed phylogenie relationships. The phylogenie patterns of the 28S rDNA D1 and mCOI regions were closely related within the same class and order as analyzed by the PAUP 4.0 program, with the exception of a few species. These findings indicate that the 28S rDNA gene sequence is more highly conserved than are the mCOI gene sequences. The 28S rDNA gene may prove useful in studies of the systematics and population genetic structures of parasitic Platyhelminthes.

• Molecules and Cells
• /
• v.24 no.1
• /
• pp.60-68
• /
• 2007

Microsatellites, also called simple sequence repeats (SSR), are very useful molecular genetic markers commonly used in crop breeding, species identification and linkage analysis. In the present study, we constructed a microsatellite-enriched genomic library of Panax ginseng, and identified 251 novel microsatellite sequences. Tri-nt repeat units were the most abundant (46.6%), followed by di-nt repeats (35.5%). The $(AG)_n$ motif was most common (23.1%), followed by the $(AAC)_n$ motif (22.3%). From the genotyping of 94 microsatellites using marker-specific primer sets, we identified 11 intraspecific polymorphic markers as well as 14 possible interspecific polymorphic markers differing between P. ginseng and P. quinquefolius. The exact allele structures of the polymorphic markers were determined and the alleles were named. This study represents the first report of the bulk isolation of microsatellites by screening a microsatellite-enriched genomic library in P. ginseng. The microsatellite markers could be useful for linkage analysis, genetic breeding and authentication of Panax species.