• Polymer(Korea)
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• 제39권1호
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• pp.165-168
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• 2015

Thermoresponsive polymers were successfully synthesized by a combination of atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed 1,3-dipolar cycloaddition of azide and alkynes (click chemistry). Poly(2-hydroxyethyl methacrylate) (PHEMA) was synthesized by ATRP, followed by introduction of alkyne groups using pentynoic acid, leading to HEMA-alkyne. Homopolymers having secondary amine groups, tertiary amines with hydroxyethyl and hydroxypropyl groups were synthesized by adding 2-azido-N-ethyl-ethanamine, 2-[(2-azidoethyl)amino]ethanol, and 2-[(2-azidoethyl)amino]propanol, respectively, to the PHEMA-alkyne backbone using click chemistry. Molecular weight (MW), molecular weight distribution (MWD), and click reaction efficiency were determined by gel permeation chromatography (GPC) and $^1H$ NMR spectroscopy. The transmission spectra of the 1.0 wt% aqueous solutions of the resulting polymers at 650 nm were measured as a function of temperature. Results showed that the lower critical solution temperature (LCST) could be easily controlled by the length of the hydroxyalkyl groups.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1869-1874
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• 2010

By reducing PVP with $H_2NOH$.HCl and NaOH 2:2:1 mass ratios in aqueous ethanol, poly-N-vinyl pyrrolidone oxime [PVPO] was prepared with 92% yield. Applying the sol-gel concept, orthosilicic acid [OSA] was made by hydrolyzing TEOS with ethanol in 1:0.5 molar ratios using 1 N KOH aqueous solution as a catalyst. The OSA + PVPO + $_L$-Valine ($\alpha$-amino acid) were mixed with pure ethanolic medium in 1:2:2 mass ratios and refluxed at $78^{\circ}C$ and 6 pH for 6.5 h. A white residue of poly-N-vinyl pyrrolidone oximo-L-valyl-siliconate [POVS] appeared after 5 h. The heating of reaction mixture was stopped and the contents were brought to NTP. The residue formation of POVS was intensified with lowering a temperature and completely solidified within 5 h, was filtered using a vacuum pump with Whatmann filter paper no. 42. The residue of POVS was washed several times with 20% aqueous cold ethanolic solution and dried in vacuum chamber at $25^{\circ}C$ for 24 h. The MP was noted above $350^{\circ}C$. Structural and internal morphology were analyzed with IR and $^1H$-NMR, and SEM respectively. A drug loading and transporting ability of the POVS in water and at pH = 5 and 8 was determined chromatographically.

• BMB Reports
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• 제38권5호
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• pp.550-554
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• 2005

YKR049C is a mitochondrial protein in Saccharomyces cerevisiae that is conserved among yeast species, including Candida albicans. However, no biological function for YKR049C has been ascribed based on its primary sequence information. In the present study, NMR spectroscopy was used to determine the putative biological function of YKR049C based on its solution structure. YKR049C shows a well-defined thioredoxin fold with a unique insertion of helices between two $\beta$-strands. The central $\beta$-sheet divides the protein into two parts; a unique face and a conserved face. The 'unique face' is located between ${\beta}2$ and ${\beta}3$. Interestingly, the sequences most conserved among YKR049C families are found on this 'unique face', which incorporates L109 to E114. The side chains of these conserved residues interact with residues on the helical region with a stretch of hydrophobic surface. A putative active site composed by two short helices and a single Cys97 was also well observed. Our findings suggest that YKR049C is a redox protein with a thioredoxin fold containing a single active cysteine.

• BMB Reports
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• 제33권3호
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• pp.268-275
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• 2000

In contrast to the pyrimidine (6-4)pyrimidone photoproduct [(6-4) adduct], its Dewar valence isomer (Dewar product) is low mutagenic and produces a broad range of mutations with a 42 % replicating error frequency. In order to determine the origin of the mutagenic property of the Dewar product, we used experimental NMR restraints and molecular dynamics to determine the solution structure of a Dewar·lesion DNA decamer duplex, which contains a mismatched base pair between the 3'-T residue and an opposed G residue. The 3'-T of the Dewar lesion forms stable hydrogen bonds with the opposite G residue. The helical bending and unwinding angles of the DW/GA duplex, however, are much higher than those of the DW/AA duplex. The stable hydrogen bonding of the G 15 residue does not increase the thermal stability of the overall helix. It also does not restore the distorted backbone conformation of the DNA helix that is caused by the forming of a Dewar lesion. These structural features implicate that no thermal stability, or conformational benefits of G over A opposite the 3'-T of the Dewar lesion, facilitate the preferential incorporation of an A. This is in accordance with the A rule during translesion replication and leads to the low frequent $3'-T{\rightarrow}C$ mutation at this site.

• Journal of the Korean Chemical Society
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• 제22권1호
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• pp.25-29
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• 1978

Cobalt(III) complex containing ethylenediamine-triacetate and trimethylenediamine has been isolated from the reaction of ethylenediamine-tetraacetatocobaltate(III) with trimethylene-diamine in aqueous solution by Dowex 50W-X8, cation exchange resin in $H^+$ form. The ethylenediamine-triacetate($EDTRA^{3-}$) ligand coordinates to the cobalt(III) ion as a quadridentate with a free acetate branch. It has been observed that the complex has trans(O-O) (1) structure via the elemental analysis, UV, IR and NMR data.

• Korean Journal of Environmental Agriculture
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• 제11권2호
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• pp.125-132
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• 1992

This study was conducted to know degradation products of the synthetic pyrethroid insecticide bifenthrin under soil, aqueous solution and UV-light irradation, and know its movement by leaching in soil. The major degradation product of bifenthrin was identified with 2-methylbiphenyl -3-y1 methanol by HPLC, UV, Mass and NMR under soil, aqueous solution and UV-light irradiation, The main degradation route was hydrolysis of the ester linkage. On exposure to UV-light, bifenthrin was decomposed almost completely in concentrations of 10 and 100 ppm in 24 hr but decomposed about 80% in 1,000 ppm. Bifenthrin was immobile in soil column system and on soil thin-layer chromatography system. Mostly bifenthrin remained in the 0-2.0㎝ layer of soil column and soil TLC.

• Transactions of the Korean hydrogen and new energy society
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• 제27권5호
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• pp.562-570
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• 2016

At the carbon dioxide capture process using the aqueous amine solution, degradation of absorbents is main factor to reducing the process performance. Also, degradation mechanism of absorbent is important for understanding the environmental risk, route of degradation products, health risk etc. In this study, the degradation products of MEA were studied to clarify mechanism in thermal degradation process. The degradation products were analyzed using a $^1H$ NMR (nuclear magnetic resonance) and $^{13}C$ NMR. The analysis methods used in this study provide guidelines that could be used to develop a degradation inhibitor of absorbent and a corrosion inhibitor.

• Bulletin of the Korean Chemical Society
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• 제13권5호
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• pp.556-559
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• 1992

Hydrocarbon solution of $(PPh_3)_2(CO)MOSO_2CF_3$ (M= Rh, Ir) reacts rapidly with 1,4-dicyanobenzene or 1,4-dicyano-2-butene to yield dinuclear metal complexes $[(PPh_3)_2(CO)M({\mu}-dicyanobenzene)M(CO)(PPh_3)_2](SO_3CF_3)_2$ (I: M = Rh; II: M = Ir) or $[(PPh_3)_2(CO)M({\mu}-dicyano-2-benzene)M(CO)(PPh_3)_2](SO_3CF_3)_2$ (III: M = Rh; IV: M = Ir), respectively. Compounds I, II, III, and IV were characterized by $^1H$-NMR, $^{31}P$-NMR, and infrared spectrum. Dichloromethane solution of II and IV reacts with $H_2\;and\;I_2$ to yield oxidative addition complexes $[(PPh_3)_2(CO)IrX_2({\mu}-E)X_2Ir(CO)(PPh_3)_2](SO_3CF_3)_2$ (V; E = 1,4-dicyanobenzene, $X_2$ = $H_2$; VI : E = 1,4-dicyano-2-butene, $X_2$ = $H_2$; VII; E = 1,4-dicyanobenzene, $X_2$ = $I_2$). All metal complexes are bridged by the cyanide groups. Compounds Ⅴ, Ⅵ, and Ⅶ are characterized by conventional methods.

• Bulletin of the Korean Chemical Society
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• 제20권3호
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• pp.301-306
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• 1999

Hepatitis C virus (HCV) has been known to be an enveloped virus with a positive strand RNA genome and the major agent of the vast majority of transfusion associated cases of hepatitis. For viral replication, HCV structural proteins are first processed by host cell signal peptidases and NS2/NS3 site of the nonstructural protein is cleaved by a zinc-dependent protease NS2 with N-terminal NS3. The four remaining junctions are cleaved by a separate NS3 protease. The solution conformations of NS4B/5A, NS5A/5B substrates and NS5A/5B inhibitor have been determined by two-dimensional nuclear magnetic resonance (NMR) spectroscopy. NMR data suggested that the both NS5A/5B substrate and inhibitor appeared to have a folded tum-like conformation not only between P1 and P6 position but also C-terminal region, whereas the NS4B/5A substrate exhibited mostly extended conformation. In addition, we have found that the conformation of the NS5A/5B inhibitor slightly differs from that of NS5A/5B substrate peptide, suggesting different binding mode for NS3 protease. These findings will be of importance for designing efficient inhibitor to suppress HCV processing.

• Analytical Science and Technology
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• 제7권2호
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• pp.213-224
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• 1994

Several isotopomers of cyclooctanone were prepared by selective deuterium substitution. Intrinsic isotope effects on $^{13}C$ NMR chemical shifts of these isotopomers were investigated systematically at low temperature. These istope effects were discussed in relation to the preferred boat-chair conformation of cyclooctanone. Deuterium isotope effects on NMR chemical shifts have been known for a long time. Especially in a conformationally mobile molecule, isotope perturbation could affect NMR signals through a combination of isotope effects on equilibria and intrinsic effects. The distinction between intrinsic and nonintrinsic effects is quite difficult at ambient temperature due to involvement of both equilibrium and intrinsic isotope effects. However if equilibria between possible conformers of cyclooctanone are slowed down enough on the NMR time scale by lowering temperature, it should be possible to measure intrinsic isotope shifts from the separated signals at low temperature. $^{13}C$ NMR has been successfully utilized in the study on molecular conformation in solution when one deals with stable conformers or molecules were rapid interconversion occurs at ambient temperature. The study of dynamic processes in general requires analysis of spectra at several temperature. Anet et al. did $^1H$ NMR study of cyclooctanone at low temperature to freeze out a stable conformation, but were not able initially to deduce which conformation was stable because of the complexity of alkyl region in the $^1H$ NMR spectrum. They also reported the $^1H$ and $^{13}C$ NMR spectra of the $C_9-C_{16}$ cycloalkanones with changing temperature from $-80^{\circ}C$ to $-170^{\circ}C$, but they did not report a variable temperature $^{13}C$ NMR study of cyclooctanone. For the analysis of the intrinsic isotope effect with relation to cylooctanone conformation, $^{13}C$ NMR spectra are obtained in the present work at low temperatures (up to $-150^{\circ}C$) in order to find the chemical shifts at the temperature at which the dynamic process can be "frozen-out" on the NMR time scale and cyclooctanone can be observed as a stable conformation. Both the ring inversion and pseudorotational processes must be "frozen-out" in order to see separate resonances for all eight carbons in cyclooctanone. In contrast to $^1H$ spectra, slowing down just the ring inversion process has no apparent effects on the $^{13}C$ spectra because exchange of environments within the pairs of methylene carbons can still occur by the pseudorotational process. Several isotopomers of cyclooctanone were prepared by selective deuterium substitution (fig. 1) : complete deuterium labeling at C-2 and C-8 positions gave cyclooctanone-2, 2, 8, $8-D_4$ : complete labeling at C-2 and C-7 positions afforded the 2, 2, 7, $7-D_4$ isotopomer : di-deuteration at C-3 gave the 3, $3-D_2$ isotopomer : mono-deuteration provided cyclooctanone-2-D, 4-D and 5-D isotopomers : and partial deuteration on the C-2 and C-8 position, with a chiral and difunctional case catalyst, gave the trans-2, $8-D_2$ isotopomer. These isotopomer were investigated systematically in relation with cyclooctanone conformation and intrinsic isotope effects on $^{13}C$ NMR chemical shifts at low temperature. The determination of the intrinsic effects could help in the analysis of the more complex effects at higher temperature. For quantitative analysis of intrinsic isotope effects, the $^{13}C$ NMR spectrum has been obtained for a mixture of the labeled and unlabeled compounds because the signal separations are very small.