• Journal of the Korean Chemical Society
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• v.48 no.3
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• pp.229-235
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• 2004

For the study of hydrogen bonding phenomenon of high energetic compounds, we have been carried out a theoretical calculations for the nitromethane with the program Gaussian-98. The calculations at levels of restricted BLYP/6-311++G(d,p), B3LYP/6-311++G(d,p) and MP2/6-311++G have been performed to obtain molecular structures, hydrogen bonding effects and vibrational spectra of nitromethane monomer and dimer. The results show nitromethane is favored to make two hydrogen bonds between molecules and the nitromethane dimer is more stable than the monomer about 15.2, 19.4 and 32.6 kJ/mol for the BLYP, B3LYP, and MP2 level calculations, respectively.

• The Microorganisms and Industry
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• v.27 no.1
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• pp.2-17
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• 2001

Cyclomaltodextrinase(CDase, EC 3.2.1.54), maltogenic amylase(EC 3.2.1.133). neopullulanase(EC 3.2.1.135)는 cyclomaltodextrin(CD), pullulan 및 전분을 가수분해하는 효소들이다. 이 효소들은 $\alpha$-1,4-Ο-glycosidic 결합에 작용하여 CD와 전분을 말토오스로 pullulan을 panose로 가수분해할 뿐만 아니라 올리고당들을 다양한 당 수용체 분자들의 C-3, C-4. C-6 수산기로 전이시키는 활성도 갖고 있다. 이러한 특성들은 기존의 $\alpha$-amylase를 비롯한 판수화물 분해효소들과 뚜렷이 구별되는 것으로 전분 분해효소들의 분류체계에 새로운 기준점을 제시한다고 하겠다. 본 총설에서는 CDase, maltogenic amylase, neopullulanase처럼 pullulan이나 전분보다 CD를 훨씬 더 잘 분해하는 효소들과 Thermoactinomyces vulgaris amylase II(TVA II)처럼 CD를 분해하기는 하나 pullulan을 더 잘 분해하는 효소들의 생화학적, 효소적, 구조적 특성들을 종합하여 소개하고자 하였다. 이 효소들은 40~60% 정도로 아미노산 서열이 동일하고, 세포 내에 존재하며, 분자량이 62~90 kDa로 $\alpha$-amylase보다 다소 크다. 아미노산 서열 비교분석 및 maltogenic amylase와 TVA II 등의 3차구조 분석 결과, 이 효소들은 아미노 말단에 보통 $\alpha$-amylase에는 존재하지 않는 약 130개 아미노산으로된 영역을 갖고 있어 이를 매개로 이합체를 형성할 수 있는 것으로 나타났다. 이합체-단위체 평형은 염 농도, 효소 농도, 산도 등에 의해 조절되고 단위체와 이합체 모두 효소환성을 갖고 있으나, 기질 특이성이 다르며 단위체는 전분을, 이합체는 CD를 선호하는데 이는 이합체 형성 시 활성부위의 구조적 변화에 따른 것으로 분석되었다. 본 총설에서는 CD 분해효소들의 다양한 기질 특이성을 올리고머 형성 등의 구조적 특성과 관련하여 논함으로써 관련 효소들의 분류체계를 보다 명확히 할 수 있는 자료를 제공하고자 하였으며, 이러한 효소들의 생리적 기능 및 산업적 이용에 대해 제안하고자 하였다.

• Journal of Life Science
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• v.15 no.6 s.73
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• pp.928-934
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• 2005

ATF2 is a cellular transcription factor which belongs to the CREB/ATF class and it is leucine zipper protein which generally binds to DNA as dimers. This paper presents the procedure for subcloning the ATF2 gene and the results of experiment used the expressed ATF2. The pET expression vector was used since it produced 6xHis fusion protein for easy purification using affinity column. The Nickel chelating chromatography was used for Purifying the expressed ATE2 from E- codi BL2l. Subsequen시y In vitro binding pull-down assay showed the binding specificity of ATF2 with AP-1 family factors such as BATF, c-Fos, c-Jun and ATF2 itselgf. ATF2 forms homodimer as well as strong heterodimer with BATF. It also forms stable dimer with c-Jun but barely binds with c-Fos.

• Analytical Science and Technology
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• v.5 no.3
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• pp.285-294
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• 1992

Structures of dimers of the acetonitrile and DMF diluted by carbon-tetrachloride and xenon matrices at 80K were studied with infrared absorption spectroscopy. Sample and matrix materials were codeposited onto a KBr cold trapping window. Infrared absorption spectra of pure samples and diluted samples were compared to explain the structures of dimers. The acetonitrile dimer showed the antiparallel shape and the DMF dimer showed the linear shape. After annealing, the infrared spectrum of the diluted sample showed the same shape with that of the pure sample.

• Applied Chemistry for Engineering
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• v.20 no.1
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• pp.75-79
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• 2009

The ratio of aniline dimer (p-aminodiphenylamine), which is a nucleation site of chain growth in a chemical polymerization of aniline monomer, to aniline monomer was controlled to synthesize polyaniline with the molecular weight ($M_w$) between 10000 and 20000 g/mol. The result of OCP measurement showed that the reaction rate of polymerization was increased as the mole ratio of dimer was increased. The increase in the molar ratio of dimer resulted in the shift of absorption wavelength of polyaniline to the short wavelength region on measurement of UV/Vis and the decrease of molecular weight on the measurement of GPC.

• Journal of the Korean Chemical Society
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• v.42 no.6
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• pp.629-637
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• 1998

The HF-SCF, MP2 and B3LYP calculations have been performed on the two conceivable clusters $(HF)_2(CO)$ trimers as well as their dimer complexes FH…FH, FH…CO and FH…OC applying $6-31+G^{\ast}^{\ast}$, and $6-311+G^{\ast}^{\ast}$ basis sets. A variety of ground state properties of these trimer complexes have been listed, and compared with corresponding properties of isolated monomers and combined dimers. It was calculated that FH…CO is more stable than FH…OC by average 0.85 kcal/mol and F-H…F-H…C≡O is more stable than F-H…F-H…O≡C by 1-2 kcal/mol. The C≡O stretching bands of the F-H…F-H…C≡O and F-H…F-H…O≡C were red shifted by 24, $37\;cm^{-1}$ compared with the FH…CO and FH…OC respectively. Also, H-F stretching bands were red shifted by 54 and $353\;cm^{-1}$.

• Journal of the Korean Chemical Society
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• v.32 no.1
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• pp.37-47
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• 1988

The electrochemical behavior of 2-Amino-1-cyclopentene-1-dithiocarboxylate (acdc) was investigated by the use of polarography, cyclic voltammetry and cathodic stripping voltammetry at glassy carbon electrode. In this study, it was found that the dimer of the acdc was deposited on the glassy carbon electrode via one-electron oxidation process at +0.25V vs. SCE. The ring formation between two dithio group occurs along with the elimination of one sulfur atom. The elimination of sulfur atom occurs via two electron oxidation process at +0.8V vs. SCE. The most sensitive cathodic stripping peak due to the formation of the dimer was observed at -0.85V vs. SCE. The peak relationship between current and concentration was fairly linear in the range of 3${\times}10^{-5}{\sim}1.0{\times}10^{-6}$M. The preconcentration procedure enhanced the sensitivity about 100 times for the analysis of acdc using diffusion current. Detection limit was found to be $2.5{\times}10^{-7}$M and relative standard deviation was ${\pm}$4.1 % at $5.0{\times}10^{-6}$M DC polarography.

• Clean Technology
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• v.29 no.2
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• pp.79-86
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• 2023

The homogeneous catalyst, Ru-MACHO-BH, selectively performs hydrogenation reactions only on the carbonyl group of α, β-unsaturated aldehyde compounds with extremely high reactivity and selectivity. However, the hydrogenation of α, β-unsaturated aldehydes involves a heterogeneous Diels-Alder reaction, resulting in the formation of significant amounts of byproducts, such as dimers. In this study, we used the Ru-MACHO-BH catalyst (Carbonyl hydrido (tetrahydroborato) [bis (2-diphenyl phosphino ethyl) amino] ruthenium(II)) to selectively hydrogenate the carbonyl group of a specific type of α, β-unsaturated aldehyde called methacryl aldehyde, leading to the synthesis of methallyl alcohol. Simultaneously, we applied diols to inhibit the formation of byproducts. The results demonstrate that monoethylene glycol can significantly reduce the formation of diols. Based on these results, we effectively suppressed the formation of dimers containing vinyl groups in methacryl aldehyde by using hydroquinone, which can efficiently inhibit the chemical interaction of vinyl groups. Consequently, the conversion rate of methacryl aldehyde was increased. Ultimately, by reducing the amount of the expensive homogeneous catalyst Ru-MACHO-BH to 1/10, we achieved a selectivity of over 90% and a yield of over 80% for the desired product, methallyl alcohol. These results provide a method to minimize yield reduction while reducing the usage of expensive catalysts, thereby improving cost-effectiveness. We expect that the reaction could be applied to various kinds of selective hydrogenation and has been successfully run on an industrial scale.

• Journal of the Korean Chemical Society
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• v.39 no.10
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• pp.776-782
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• 1995

A theory of the helix/coil transition for $\alpha$ helical dimer such as $\alpha$ tropomycin and paramycin is developed. The treatment differs from those formulated previously for oligopeptide dimer which is explained by the matrix method using Zimm-Bragg parameter: In the present treatement, it is explained by the zipper model which can account for the dangling H-bond. We calculate the fractional helicity in $\alpha$ helical dimer as a function of helix initiation $constant(\sigma)$, helix stability constant(${\xi}$) and hydrophobic interaction parameter(w). For $\alpha$ tropomycin, the helix stability profile is also calculated. The transitions of this oligomer due to the change of temperature and the concentration of oligopeptide involve simultaneous dissociation of the dimer. The transitions of dimers which have cross-linked S-S bonds or have long chains don't occur, because they keep always helical structures. The transitons due to the concentration of the oligopeptides are steeper than those due to the chain length or temperature.

• Journal of the Korean Applied Science and Technology
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• v.38 no.4
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• pp.1003-1009
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• 2021

A study on the associative properties of sodium hyaluronate (NaHA) and Alkane-bis (dimethylalkylammonium bromide) surfactants in aqueous solution was investigated in relation to the chemical structure of surfactants. As a result of measuring the interfacial tension, a parabolic graph showing the minimum value (c_min) at a specific concentration was shown. Above this minimum concentration the increase in interfacial tension is thought to be related to the formation of aggregates of NaHA chains and dimeric surfactants. The plot of viscosity vs surfactant concentration shows a slight maxium at c_min and a viscosity decrease at high surfactant concentrations. Viscosity nonlinear behavior is related to the size increase due to the complex growth and to the size shrinkage following from the interaction with electrolyte ions and free micelles. The results of surface tension measurements show a broad region of surface tension decrease, indicating the NaHA-surfactant interaction. The increase in surface tension above c_min may be related to the adsorption of clusters, consisting of free NaHA chains and dimeric surfactant. The strong adsorption of surfactant is observed at high concentrations.