• Journal of the Korean Chemical Society
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• v.31 no.6
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• pp.534-541
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• 1987

The study of reaction mechanism for the substitution of ethylenediamine (en) for Cl and Hedta from $[CoCl(Hedta)]^-$ in the presence of $Hg^{2+}$ ion was carried out by uv and CD spectra. From the kinetic data, we proposed that the first ethylenediamine be substituted through the associative reaction path by means of interaction of $Hg^{2+}$ ion with Co(III), and that the second and the third ethylenediamine be substituted stepwise. From the optical purities of $[Co(en)_3]^{3+}$ which was formed after reaction, we suggested the critical stereochemical step and new substitution reaction paths.

• Journal of the Korean institute of surface engineering
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• v.48 no.3
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• pp.105-109
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• 2015

We studied emission characteristics of blue fluorescent multi-tandem OLEDs using $Al/MoO_x$ as charge generation layer(CGL). Threshold voltage for 2, 3, 4, and 5 units tandem OLEDs was 8, 11, 14 and 18 V, respectively. The threshold voltage in multi-tandem OLEDs was lower than multiple of 4 V for the single OLED. Maximum current efficiency and maximum quantum efficiency of single OLED were 7.6 cd/A and 5.5%. Maximum current efficiency for 2, 3, 4, and 5 units tandem OLEDs was 22.6, 31.4, 41.2, and 46.6 cd/A, respectively. Maximum quantum efficiency for 2, 3, 4, and 5 units tandem OLEDs was 11.8, 15.8, 21.8, and 25.6%, respectively. The maximum current efficiency and maximum quantum efficiency in multi-tandem OLEDs were higher than multiple of those for the single OLED. The intensity for 508 nm peak was changed and the peak wavelength was red shift by increase of tandem unit in electroluminescent emission spectra. These phenomena can be caused by micro-cavity effect with increasing of organic layer thickness.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.3
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• pp.105-110
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• 2002

J-aggregates in the mutual mixing LB films of [6Me-DS]$_{1-x}$ [DO]$_{x}$,[DS]$_{1-x}$ [DO]$_{x}$ and [DSe]$_{1-x}$ [DO]$_{x}$ have been studied by optical absorption, fluorescence and surface pressure-area isotherms. In [6Me-DS]$_{1-x}$ [DO]$_{x}$ films, sharp J-band absorption and fluorescence of [6Me-DS] are linearly shifted to the longer wavelength for the replacement of [6Me-DS] by [DO]. According to the x, a smooth shift of the limited area has been cleared. In the [DS]-[DO] system, the J-band is enhanced at 1:1 composition and strong fluorescence is also observed. Also, the presence of phase separation was suggested in the [DSe]-[DO] system, because the absorption spectra were decomposed into [DSe] and [DO] spectra. On the other hand, in the pressure-area isothermal study, reduction in the molecular occupying area of monolayers has been clarified. This could be ascribed to the enhancement of molecular ordering in J-aggregates. These facts are also believed to reflect the most closely packed arrangement of chromophores in the merocyanine dye monolayers. Thus, it was confirmed that the interaction between mixed dye molecules and the CdC1$_2$+KHCO$_3$subphases affected the J-aggregates of the LB films. Also. it is thought that the J-aggregates are formed non-dimensionally in LB films, such as solution synthesized [DX:DO] assemblies on mixing.s on mixing.

• Journal of the Korean Magnetic Resonance Society
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• v.20 no.3
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• pp.95-101
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• 2016

Apolipoprotein B-100 (Apo-B100) is a major component of low density lipoprotein (LDL). Apo B-100 protein has 4,536 amino acid sequence and these amino acids are classified into peptide groups A to G with subsequent 20 amino acids (P1-P302). The peptide groups were act as immunoglobulin (Ig) antigens which oxidized via malondialdehyde (MDA). The mimetic peptide P1 (EEEMLENVSLVCPKDAT RFK) out of D-group peptides carrying the highest value of IgG antigens were selected for structural studies that may provide antigen specificity. Circular Dichroism (CD) spectra were measured for peptide secondary structure in the range of 190-250 nm. Experimental results show that P1 exhibit partial of ${\beta}-sheet$ and random coil structure. Homonuclear (COSY, TOCSY, NOESY) 2D-NMR experiments were carried out for NMR signal assignments and structure determination for P1. On the basis of these completely assigned NMR spectra and distance data, distance geometry (DG) and Molecular dynamics (MD) were carried out to determine the structures of P1. The proposed structure was selected by comparisons between experimental NOE spectra and back calculated 2D NOE results from determined structure showing acceptable agreement. The total Root-Mean-Square-Deviation (RMSD) value of P1 obtained upon superposition of all atoms was in the range $0.33{\AA}$. The solution state P1 has mixed structure of ${\beta}-sheet$ (Glu[1] to Cys[12]) and random coil (Pro[13] to Lys[20]). These NMR results are well consistent with secondary structure from experimental results of circular dichroism. Structural studies based on NMR may contribute to the studies of atherosclerosis and observed conformational characteristics of apo B-100 in LDL using monoclonal antibodies.

• Journal of the Korean Magnetic Resonance Society
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• v.24 no.4
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• pp.136-142
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• 2020

Apolipoprotein B-100 (apo B-100), the main protein component that makes up LDL (Low density lipoprotein), consists of 4,536 amino acids and serves to combine with the LDL receptor. The oxidized LDL peptides by malondialdehyde (MDA) or acetylation in vivo were act as immunoglobulin (Ig) antigens and peptide groups were classified into 7 peptide groups with subsequent 20 amino acids (P1-P302). The biomimetic peptide P99 (KGTYG LSCQR DPNTG RLNGE) out of B-group peptides carrying the highest value of IgM antigens were selected for structural studies that may provide antigen specificity. Circular Dichroism (CD) spectra were measured for peptide secondary structure in the range of 190-260 nm. Experimental results show that P99 has pseudo α-helice and random coil structure. Homonuclear (COSY, TOCSY, NOESY) 2D-NMR experiments were carried out for NMR signal assignments and structure determination for P99. On the basis of these completely assigned NMR spectra and proton distance information, distance geometry (DG) and molecular dynamic (MD) were carried out to determine the structures of P99. The proposed structure was selected by comparisons between experimental NOE spectra and back-calculated 2D NOE results from determined structure showing acceptable agreement. The total Root-Mean-Square-Deviation (RMSD) value of P99 obtained upon superposition of all atoms were in the set range. The solution state P99 has mixed structure of pseudo α-helix and β-turn(Gln[9] to Thr[13]). These NMR results are well consistent with secondary structure from experimental results of circular dichroism. Structural studies based on NMR may contribute to the prevent oxidation studies of atherosclerosis and observed conformational characteristics of apo B-100 in LDL using monoclonal antibodies.

• Molecules and Cells
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• v.26 no.2
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• pp.206-211
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• 2008

HI0381 of Haemophilus influenzae was investigated by circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy. HI0381 is a 153-residue peptidoglycan-associated outer membrane lipoprotein, and a part of the larger Tol/Pal network. Here, we report its backbone $^1H$, $^{15}N$, and $^{13}C$ resonance assignments, and secondary structure predictions. About 97% of all of the $^1HN$, $^{15}N$, $^{13}CO$, $^{13}C{\alpha}$, and $^{13}C{\beta}$ resonances covering 131 non-proline residues of the 134 residue, mature protein, were clarified by sequential and specific assignments. CSI and TALOS analyses revealed that HI0381 contains five ${\alpha}$-helices and five ${\beta}$-strands. To characterize the structure of HI0381, the effects of pH and salt concentration were investigated by CD. In addition, the structural changes occurring when HI0381 was in a membranous environment were investigated by comparing its HSQC spectra and CD data in buffer and in DPC micelles; the results showed that helix ${\alpha}4$ and strand ${\beta}4$ became aligned with the membrane. We conclude that the conformation of HI0381 is affected by the membrane environment, implying that its folded state is directly related to its function.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.729-732
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• 2012

Herein we report the in-situ synthesis and direct decoration of chalcogenide naoparticles (NPs) onto multiwalled carbon nanotubes (MWCNTs) through an ionic liquid-assisted sonochemical method (ILASM). The as-obtained MWCNT/$BMimBF_4$/CdTe, MWCNT/$BMimBF_4$/ZnTe and MWCNT/$BMimBF_4$/ZnSe nanocomposites were characterized by TEM images and EDS spectra. In particular, the morphologies of nanocomposites such as bump-like, rough, and smooth core-shell structures were strongly influenced by the type of precursors and the interactions with MWCNT. This synthetic strategy opens a new way to directly synthesize and deposit semiconducting NPs (s-NPs) onto CNTs, which consist of binary components obtained from two precursors with different reaction rates.

• Journal of the Korean Magnetic Resonance Society
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• v.3 no.2
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• pp.100-108
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• 1999

Cop protein is the transcription repressor protein in rolling circle replication plasmid. With antisense RNA, Cop protein controls the copy number of plasmid. Cop family proteins have been found in various plasmids. Among Cop family proteins, Cop studied in this paper consists of 55 amino acids (Mw. 6,400), and was known to have trimer structure. Since no structural facts are elucidated, we have carried out preliminary experiments aimed at the elucidation of its three dimensional structure. The secondary structure of Cop is studied by CD and NMR. To solve the aggregation of Cop at high concentration, we tested various detergents and salts. The addition of detergents and salts could not solve the aggregation problem. However, we found that concentration is important in solving the aggregation problem. We knew that 0.18mM in 50mM potassium phosphate without any other ingredients is maximum concentration not to aggregate. Wa also investigated the pH dependence of Cop protein, and knew that Cop protein is more stable in acid state. At various temperatures, 15N-1H HSQC spectra were measured in order to find the optimal experimental condition. To enhance the peak resolution, 3D NOESY-HSQC spectrum is acquired. Since there are NOE peaks in the NH-NH region, we knew that Cop protein has $\alpha$-helical content, which was also confirmed by CD.

• Carbon letters
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• v.10 no.2
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• pp.114-122
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• 2009

Crushed, depitted peach stones were impregnated activated with 50% $H_3PO_4$ followed by pyrolysis at $500^{\circ}C$. Two activated carbons were produced, one under its own evolved gases during pyrolysis, and the second conducted with air flow throughout the carbonization stage. Physicochemical properties were investigated by several procedures; carbon yield, ash content, elemental chemical analysis, TG/DTG and FTIR spectra. Porosity characteristics were determined by the conventional $N_2$ adsorption at 77 K, and data analyzed to get the major texture parameters of surface area and pore volume. Highly developed activated carbons were obtained, essentially microporous, with slight effect of air on the porous structure. Oxygen was observed to be markedly incorporated in the carbon matrix during the air treatment process. Cation exchange capacity towards Cu (II) and Cd (II) was tested in batch single ion experimental mode, which proved to be slow and a function of carbon dose, time and initial ion concentration. Copper was up taken more favorably than cadmium, under same conditions, and adsorption of both cations was remarkably enhanced as a consequence of the air treatment procedure. Sequestration of the metal ions was explained on basis of the combined effect of the oxygen functional groups and the phosphorous-containing compounds; both contributing to the total surface acidity character.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1479-1484
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• 2010

Photosynthesis uses light energy to drive the oxidation of water at an oxygen-evolving catalytic site within photosystem II (PSII). Chlorophyll binding by the photosystem II subunit S protein, PsbS, was found to be necessary for energy-dependent quenching (qE), the major energy-dependent component of non-photochemical quenching (NPQ) in Arabidopsis thaliana. It is proposed that PsbS acts as a trigger of the conformational change that leads to the establishment of nonphotochemical quenching. However, the exact structure and function of PsbS in PSII are still unknown. Here, we clone and express the recombinant PsbS gene from Arabidopsis thaliana in E. coli and purify the resulting homogeneous protein. We used various biochemical and biophysical techniques to elucidate PsbS structure and function, including circular dichroism (CD), fluorescence, and DSC. The protein shows optimal stability at $4^{\circ}C$ and pH 7.5. The CD spectra of PsbS show that the conformational changes of the protein were strongly dependent on pH conditions. The CD curve for PsbS at pH 10.5 curve had the deepest negative peak and the peak of PsbS at pH 4.5 was the least negative. The fluorescence emission spectrum of the purified PsbS protein was also measured, and the ${\lambda}_{max}$ was found to be at 328 nm. PsbS revealed some structural changes under varying temperature and oxygen gas condition.