• Polymer(Korea)
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• v.30 no.1
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• pp.56-63
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• 2006

We have synthesized two types of diamine monomers containing various chain length to prepare polyimides with layered structure. By using these diamines, homo-polyimides and co-polyimides having hydrophobic and hydrophilic segment of flexible side chain were synthesized. The segregated layered structures were formed by repulsive force with main chain as the side chains reach a critical length because the rigid main chains are packed into layered structure with the flexible side chains occupying the space between layers. As a result, the gallery space of each homo-polyimide was increased at spacing of $32.7\~48{\AA}\;or\;7\~10.5{\AA}$ as the increased hydrophobic or hydrophilic side chain length through X-ray diffraction. The gallery space of co-polyimides was also showed similar phenomenon by repulsive force of side chains with different properties. We have also confirmed that gallery space and molar volume were significantly depended on length of flexible side chain via molecular modeling.

• Bulletin of the Korean Chemical Society
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• v.26 no.2
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• pp.309-311
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• 2005

Single crystals of the new pentanary thiophosphate, $K_{0.5}Ag_{0.5}Nb_2PS_{10}$ has been prepared through reactions of the elements with halide fluxes. The structure of $K_{0.5}Ag_{0.5}Nb_2PS_{10}$ has been analyzed by single crystal X-ray diffraction technique. The structure of $K_{0.5}Ag_{0.5}Nb_2PS_{10}$ is made up of one-dimensional ${^{\infty}_1}[Nb_2PS_{10}]$ chains along the [001] direction and these chains are separated from one another by $Ag^+$ and disordered $K^+$ ions. This chain is basically built up from bicapped trigonal prismatic [Nb2S12] units and tetrahedral [PS4] groups. The [$Nb_2S_{12}$] units are connected together to form the linear chain, ${^{\infty}_1}[Nb_2S_9]$ by sharing the S-S prism edge. Short (2.885(2) $\AA$ or 2.888(2) $\AA$) and long (3.743(1) $\AA$) Nb-Nb distances are alternating along the chain, and the $S_2{^2-}]\;and\;S^{2-}$anionic species are observed. The distorted octahedral coordination around the $Ag^+$ ion can be described as [2+4] bonding interaction.

• Journal of the Korean Society of Clothing and Textiles
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• v.7 no.2
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• pp.11-17
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• 1983

There have been two supposition that the decrement of fatty soil removal at high temperature was caused by surfactants and by the structure of fibers and Fabrics. To study the effect of temperature on the removal of fatty soil, the following variables were selected: Sodium n-alkylsulfates having various chain lengths of alkyl groups as surfactants, cotton and cuprammonium rayon as cellulose fibers having different fiber structure, and two types of soil having different melting points. Experiment was carried out with radiotagged soil and detergency was estimated by liquid scintillation counting. The results were as following: the detergency of tripalmitin on cotton was increased with elevating temperature up to $60\~70^{\circ}C$ and decreased above $70^{\circ}C$ regardless of alkyl chain length of sodium n-alkylsulfates. In distilled water without surfactant, the detergency of tripalmitin on cotton was also decreased above $70^{\circ}C$, but the detergency of tripalmitin on cuprammonium rayon was not decreased above $70^{\circ}C$. effects seemed to be caused by fiber structure. Though the melting point of mixture of tripalmitin and dodecane was lower than that of tripalmitin, the optimum and decrement temperature of detergency were not altered. Finally the results of this study were shown that the surfactant and characteristics of soil did not affect on the mode of detergency vs temperature, but the fiber structure.

• Journal of the Korean Magnetics Society
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• v.19 no.3
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• pp.81-84
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• 2009

We examine the effect of U term (U = 3 eV) describing the Coulomb interactions between electrons on the results of electronic band structure calculations carried out for bcc Fe bulk, monolayer, and chain. We investigated the properties of the three Fe structures by using the all-electron total-energy full-potential linearized augmented plane wave method. The U term was included in the exchange - correlation functionals constructed on the basis of local density approximation (LDA) and general gradient approximation (GGA). We found that in the case of bcc Fe bulk structure inclusion of the U term leads to the overestimated values of magnetic moment on Fe atom. The values of magnetic moment calculated for Fe in monolayer and chain are in accordance with calculations in which the U term was not included. In general, for each system the calculated values of magnetic moment on Fe sites were larger when the U term was incorporated in the energy functional. In Fe bulk, the value of magnetic moment $2.54{\mu}_B$ for LDA+U larger than $2.25{\mu}_B$ for LDA.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.828-832
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• 2012

We performed replica exchange molecular dynamics (REMD) simulations of the tripzip2 peptide (betahairpin) using the GB implicit and TI3P explicit solvation models. By comparing the resulting free energy surfaces of these two solvation model, we found that the GB solvation model produced a distorted free energy map, but the explicit solvation model yielded a reasonable free energy landscape with a precise location of the native structure in its global free energy minimum state. Our result showed that in particular, the GB solvation model failed to describe the tryptophan packing of trpzip2, leading to a distorted free energy landscape. When the GB solvation model is replaced with the explicit solvation model, the distortion of free energy shape disappears with the native-like structure in the lowest free energy minimum state and the experimentally observed tryptophan packing is precisely recovered. This finding indicates that the main source of this problem is due to artifact of the GB solvation model. Therefore, further efforts to refine this model are needed for better predictions of various aromatic side chain packing forms in proteins.

• Journal of Microbiology and Biotechnology
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• v.29 no.11
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• pp.1769-1776
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• 2019

Ethyl (S)-3-hydroxy-3-(2-thienyl) propanoate ((S)-HEES) acts as a key chiral intermediate for the blockbuster antidepressant drug duloxetine, which can be achieved via the stereoselective bioreduction of ethyl 3-oxo-3-(2-thienyl) propanoate (KEES) that contains a 3-oxoacyl structure. The sequences of the short-chain dehydrogenase/reductases from Chryseobacterium sp. CA49 were analyzed, and the putative 3-oxoacyl-acyl-carrier-protein reductase, ChKRED12, was able to stereoselectively catalyze the NADPH-dependent reduction to produce (S)-HEES. The reductase activity of ChKRED12 towards other substrates with 3-oxoacyl structure were confirmed with excellent stereoselectivity (>99% enantiomeric excess) in most cases. When coupled with a cofactor recycling system using glucose dehydrogenase, the ChKRED12 was able to catalyze the complete conversion of 100 g/l KEES within 12 h, yielding the enantiopure product with >99% ee, showing a remarkable potential to produce (S)-HEES.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.191-191
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• 2006

The structures of the mesophases and their subunits of PS-b-P4VP in a toluene solution were studied by using SAXS, TEM and GIFT methods. The hierarchical structures of PS-b-P4VP, such as the individual micelle, the face-centered cubic (fcc) and body-centered cubic (bcc) structures and the lamellar structure, were identified for the first time. The diameter of the micelle core was ${\sim}80\;%$ of the most extended chain length of the core chain, suggesting that the core chains were quite stretched. The stretched chain in the core caused the core of the micelle to be not homogenous with a higher density at the center than at the outer part. As the concentration level increases, the fcc and both fcc and bcc appear for the packing of the micelles of PS(3.3k)-b-P4VP(4.7K) and PS(12K)-b-P4VP(11.8K), respectively. The lamellar structure was also identified, with a further increase in the concentration for PS(3.3k)-b-P4VP(4.7K). These hierarchical structures were also identified via TEM images.

• Journal of the Korean Applied Science and Technology
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• v.16 no.3
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• pp.255-262
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• 1999

The new copolymers which contain flexible spacers in main chain were prepared and their properties were studied. the copolymers were synthesized in the melt polymerization melted from diacetoxynaphthalene isomers, ${\alpha},{\omega}bis(4-carboxyphenoxy)$ alkanes and p-acetoxy benzoic acid in the molar ratio of 1:1:2 and characterized for the effects of structure of naphthalenediol isomer moieties and the spacers on thermal crystalline and liquid crystalline properties of the resulting polymers. Diacetoxy naphthalene isomers were used 1. 5-,1. 6-,2. 6-and 2. 7-disubstituted ones and the spacers was either tetramethylene or decamethylene. The polymer was characterized by elemental and spectropic analysis, differential scanning calorimetry (DSC) on a polaring microscope, wide-angle X-ray diffractometry and thermogravimetry (TGA). There glass transition temperatures (Tg) and melting temperature (Tm) on the structure of the naphthalenediol isomer moieties and the length of the spacers. The presence of spacers was found to the helpful in crystallization of 1. 6-naphthalenediol copolyesters. The presence of amide group in the backbone chain of polymer was found to increase transition temperature, crystallization, thermal stability of polymers but to decreas solubility.

• Journal of Information Management
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• v.20 no.1
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• pp.66-85
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• 1989

The purpose of this study is to verify the following two hypotheses by using a test collection of 3.815 documents on the subject of chemistry. First hypothesis is that a Markov chain model can be used t9 describe and predict authors' movements among subareas of a discipline. Second hypothesis is that a transition matrix of the Markov chain can be applied to describ the intellectual structure of a discipline en the multidimensional space. The results of this study have shown that the Markov chain is a good model to be used to study the movement of korean chemists in 7 subtopics in chemistry and understand the intellectual structure of chemistry.

• Polymer(Korea)
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• v.26 no.4
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• pp.439-444
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• 2002

Several monomeric benzilidene anhydrides (2a~d) haying n-alkyloxy groups with various n-alkyl chain lengths were prepared by Stobbe condensation of diethyl succinate with 4-(n-alkyloxy)benzaldehyde (1a,b) followed by hydrolysis by the succinates and cyclodehydration of the benzilidenated succinic acids. Configurational isomerism of the monomer was investigated by spectroscopic means. It was found that monomers (2a~d) exist in (Z,Z)-isomeric structure. Polymerization was carried out in bulk at 150~$210^{\circ}C$ range in nitrogen flow. The chemical structure and thermal properties of the polymers were characterized by spectroscopic means, TGA and DSC. Their properties highly depended on their chemical structures in accordance with a side chain length.