• 한국자기공명학회논문지
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• 제22권4호
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• pp.139-143
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• 2018

Short antimicrobial peptide, A4W, have been studied by molecular dynamics (MD) simulation in an explicit dodecylphosphocholine (DPC) micelle. Peptide was aligned with DPC micelle and transferred new peptide-micelle coordinates within the same solvent box using specific micelle topology parameters. After initial energy minimization and equilibration, the conformation and orientation of the peptide were analyzed from trajectories obtained from the RMD (restrained molecular dynamics) or the subsequent free MD. Also, the information of solvation in the backbone and the side chain of the peptide, hydrogen bonding, and the properties of the dynamics were obtained. The results showed that the backbone residues of peptide are either solvated using water or in other case, they relate to hydrogen bonding. These properties could be a critical factor against the insertion mode of interaction. Most of the peptide-micelle interactions come from the hydrophobic interaction between the side chains of peptide and the structural interior of micelle system. The interaction of peptide-micelle, electrostatic potential and hydrogen bonding, between the terminal residues of peptide and the headgroups in micelle were observed. These interactions could be effect on the structure and flexibility of the peptide terminus.

• 대한화학회지
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• 제19권1호
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• pp.11-15
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• 1975

Carbonyl 탄소원자의 반응성에 대한 연구의 일환으로 N,N-dimehtylcarbamoyl chloride와 N,N-diethylcarbamoyl chloride의 할로겐 교환반응을 아세톤 용매속에서 방사성 할라이드 이온을 사용하여 두 온도에서 속도론적으로 연구하였다. 그 결과를 alkylchloroformate의 경우와 비교하면, 친핵성의 순서는 비슷한 경향을 나타내나, 반응속도는 가용매분해나 alkylchloroformate의 경우보다 느리다. 활성화 피라미터 ${\Delta}H^*$나${\Delta}S^*$는$Cl^{\rightarrow}Br^{\rightarrow}I^-$는순서로 감소한다. 이 결과를 용매화 효과, bond-breaking, bond-formation 및 electronic requirment로 설명하였다.

• Bulletin of the Korean Chemical Society
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• 제29권2호
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• pp.431-437
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• 2008

The solvent effects on the relative free energies of binding of K+ and Na+ ions to 12-crown-4 and Dlog Ks (the difference of stability constant of binding) have been investigated by a Monte Carlo simulation of statistical perturbation theory (SPT) in several solvents. Comparing the relative free energies of binding of K+ and Na+ ions to 12-crown-4, in CH3OH of this study with experimental works, there is a good agreement among the studies. We have reported here the quantitative solvent-polarity relationships (QSPR) studied on the solvent effects the relative free energies of binding of K+ and Na+ ions to 12-crown-4. We noted that DN(donor number) dominates the differences in relative solvation Gibbs free energies of K+ and Na+ ions and DN dominates the negative values in differences in the stability constant (Dlog Ks) as well as the relative free energies of binding of K+ and Na+ ions to 12-crown-4 and p* (Kamlet-Tafts solvatochromic parameters) dominates the positive values in differences in the stability constant (Dlog Ks) as well as the relative free energies of binding of K+ and Na+ ions to 12-crown-4.

• 통합자연과학논문집
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• 제3권4호
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• pp.231-236
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• 2010

Partial charge is an important and fundamental concept which can explain many aspects of chemistry. Since a molecule can be regarded as neclei surrounded by electron cloud, there is no way to define a partial charge accurately. Nevertheless, there have been many attempts to define these seemingly impossible parameters, since they would facilitate the understanding of molecular properties such as molecular dipole moment, solvation, hydrogen bonding, molecular spectroscopy, chemical reaction, etc. Common methods are based on the charge equalization, orbital occupancy, charge density, and electric multipole moments, and electrostatic potential fitting. Methods based on the charge equalization using electronegativity are very fast, and therefore they have been used to study many compounds. Methods to subdivide orbital occupancy using basis set conversion, relies on the notion that molecular orbitals are composed of atomic orbitals. The main idea is to reduce overlap integral between two nuclei using converted orthogonal basis sets. Using some quantum mechanical observables like electrostatic potential or charge multipole moments. Using potential grids obtained from wavefunction, partial charges can be fitted. these charges are most useful to describe intermolecular electrostatic interactions. Methods to using dipole moment and its derivatives, seems to be sensitive the level of theory, Dividing electron density using density gradient being the most rigorous theoretically among various schemes, bears best potential to describe the charge the most adequately in the future.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.279-286
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• 2020

In this article, we develop a reactive distillation (RD) column configuration for the production of hydrogen. This RD column is in the HI decomposition section of the sulphur - iodine (SI) thermochemical cycle, in which HI decomposition and H₂ separation take place simultaneously. The section plays a major role in high hydrogen production efficiency (that depends on reaction conversion and separation efficiency) of the SI cycle. In the column simulation, the rigorous thermodynamic phase equilibrium and reaction kinetic model are used. The tuning parameters involved in phase equilibrium model are dependent on interactive components and system temperature. For kinetic model, parameter values are adopted from the Aspen flowsheet simulator. Interestingly, there is no side reaction (e.g., solvation reaction, electrolyte decomposition and polyiodide formation) considered aiming to make the proposed model simple that leads to a challenging prediction. The process parameters are determined on the basis of optimal hydrogen production as reflux ratio = 0.87, total number of stages = 19 and feeding point at 8th stage. With this, the column operates at a reasonably low pressure (i.e., 8 bar) and produces hydrogen in the distillate with a desired composition (H₂ = 9.18 mol%, H₂O = 88.27 mol% and HI = 2.54 mol%). Finally, the results are compared with other model simulations. It is observed that the proposed scheme leads to consume a reasonably low energy requirement of 327 MJ/kmol of H₂.

• 공업화학
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• 제10권5호
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• pp.718-725
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• 1999

Inverse gas chromatography(IGC) 방법은 고분자-용매 계의 열역학적 특성을 신속하고 정확하게 결정할 수 있는 신뢰할 만한 방법 중 하나이다. 본 연구에서는 유한 농도에서의 IGC 방법을 사용하여 poly(dimethylsiloxane)(PDMS)과 물, 에탄올, 그리고 이소프로판올과의 상호작용을 정량적으로 결정하였다. 이를 위하여 고정상 내 용매의 체류시간으로부터 Flory-Huggins의 상호작용 계수를 산출하여 PDMS와 용매간의 소수성 상호작용을 의미하는 큰 양의 값(2$2.0{\times}10^{-3}mol/g$이었다. 또한 선형고분자에 대한 Kirkwood-Buff-Zimm(KBZ) 적분을 행하여 고분자와 용매의 분자분포 구조를 추정하였다. 이로부터 물분자는 PDMS에 대하여 용매화되지 않고 자체 분자끼리 부분적인 클러스트를 형성하며, 에탄올과 이소프로판올에서는 탄소수가 증가함에 따라 균일한 혼합에 가까운 분자분포의 구조적 성질을 추정할 수 있었다.

• Asian Pacific Journal of Cancer Prevention
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• 제14권12호
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• pp.7473-7482
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• 2013

The G-protein coupled receptor 87 (GPR87) is a recently discovered orphan GPCR which means that the search of their endogenous ligands has been a novel challenge. GPR87 has been shown to be overexpressed in squamous cell carcinomas (SCCs) or adenocarcinomas in lungs and bladder. The 3D structure of GPR87 was here modeled using two templates (2VT4 and 2ZIY) by a threading method. Functional assignment of GPR87 by SVM revealed that along with transporter activity, various novel functions were predicted. The 3D structure was further validated by comparison with structural features of the templates through Verify-3D, ProSA and ERRAT for determining correct stereochemical parameters. The resulting model was evaluated by Ramachandran plot and good 3D structure compatibility was evidenced by DOPE score. Molecular dynamics simulation and solvation of protein were studied through explicit spherical boundaries with a harmonic restraint membrane water system. A DRY-motif (Asp-Arg-Tyr sequence) was found at the end of transmembrane helix3, where GPCR binds and thus activation of signals is transduced. In a search for better inhibitors of GPR87, in silico modification of some substrate ligands was carried out to form polar interactions with Arg115 and Lys296. Thus, this study provides early insights into the structure of a major drug target for SCCs.

• 공업화학
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• 제5권1호
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• pp.90-98
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• 1994

구연산-초산-유산계에서 구연산의 반응추출에 영향을 미치는 여러 인자를 규명하기 위하여 추출제로 2급과 3급아민 및 용매화추출제를, 용매로 n-butylacetate, MIBK, kerosine 및 xylene 등을, modifier로서 tributyl-phosphate(TBP)와 isodecanol이 이용되었다. 그 외에 수용액상의 pH와, 온도의 영향을 연구하였고 평형상수도 얻었다. NaOH, $Na_2CO_3$ 및 $K_2HPO_4$ 알칼리 수용액에 의한 재추출 실험도 하였다. 실험결과 구연산의 추출에서 2급아민인 di-isotridecylamine(DITDA)이 추출도와 선택성에서 가장 좋았고 용매로서는 n-butylacetate가, modifier로서는 TBP가 우수하였다. 이외에도 수용액의 pH와 추출계의 온도가 낮을수록 추출도가 높았다. 재추출도는 stripping상의 염기도와 온도가 낮을수록 높아졌고 알카리 농도가 커질수록 높아졌다.

• Bulletin of the Korean Chemical Society
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• 제27권12호
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• pp.2011-2018
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• 2006

We have investigated the solvent effects on $\Delta log\;K_s $(the difference of stability constant of binding) and the different free energies of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6, i.e., the selectivity of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6 using a Monte Carlo simulation of statistical perturbation theory (SPT) in diverse solvents. The stability constant ($\Delta log\;K_s $) of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6, in $CH_3OH$ was calculated in this study as -1.06 agrees well with the different experimental results of -0.44~-0.6, respectively. We have reported here the quantitative solvent-polarity relationships (QSPR) studied on the solvent effects the relative free energies of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6. From the calculated coefficients of QSPR, we have noted that solvent polarity (ET) and Kamlet -Tafts solvatochromic parameters (b ) dominate the differences in relative solvation Gibbs free energies of $Nd^{3+}$ and $Eu^{3+}$ ions but basicity (Bj) dominates the negative values in differences in the stability constant ($\Delta log\;K_s $) as well as the relative free energies of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6 and acidity (Aj) dominates the positive values in differences in the stability constant ($\Delta log\;K_s $) as well as the relative free energies of binding of $Nd^{3+}$ and $Eu^{3+}$ ions to 18-crown-6.

• 대한화학회지
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• 제40권5호
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• pp.327-332
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• 1996

이성분혼합용매내에서 Methyl-, Phenyl Chloroformate와 1-adamantyl 유도체들의 가용매분해반응속도를 여러 온도와 압력하에서 전도도방법에 의하여 측정하였다. 이들 속도상수로부터 활성화 부피(${\Delta}V_o^{\neq}$), 활성화 엔탈피(${Delta}H^{\neq}$), 활성화 엔크로피 (${\Delta}S^{\neq}$) 값을 구하였다. 이때 모든 혼합물내에서 ${\Delta}V_o^{\neq}$와 ${\Delta}V_s^{\neq}$는 음의 값을 나타내었으며, ${\Delta}H^{\neq}$는 양의 값을 얻었다. 이 현상을 용매구조변화에 대하여 논의하였다. 또한 활성화 부피와 활성화 엔트로피 값들을 플로트하여 본 반응에 대한 반응 경향성을 조사하였다. 이들 결과로부터 Methyl-, Phenyl Chloroformate와 1-adamantyl fluoroformate(알코올수용액)는 이분자반응이, 1-adamantyl fluoromate(TFE수용액)와 1-adamantyl tosylate는 일분자반응이 일어나는 것으로 추정할 수 있었다.