• Bulletin of the Korean Chemical Society
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• 제35권10호
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• pp.2906-2910
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• 2014

This report introduces Gaussian electrostatic models (GEMs) to account for charge penetration effects in water-water interactions, allowing electrostatic interactions to be accurately described. Three different Gaussian electrostatic models, GEM-3S, GEM-5S, and GEM-6S are designed with s-type Gaussian functions. The coefficients and exponents of the Gaussian functions are optimized using the electrostatic potential (ESP) fitting procedure based on that of the MP2/aug-cc-pVTZ method. The electrostatic energies of ten different water dimers that were calculated with GEM-6S agree well with the results of symmetry-adapted perturbation theory (SAPT), indicating that this designed model can be effectively applied to future water models.

• Bulletin of the Korean Chemical Society
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• 제24권1호
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• pp.55-59
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• 2003

This work is focused on analyzing ion-pair interactions and showing the effect of solvent induced inter-atomic attractions in various dielectric environments. To estimate the stability of ion-pairs, SCI-PCM ab initio MO calculations were carried out. We show that the solvent-induced attraction or ‘cavitation' energy of the ion-pair interactions in solution that arises mainly from the stabilization of the water molecules by the generation of an electrostatic field. In fact, even the strong electrostatic interaction characteristic of ion-pair interactions in the gas phase cannot overcome the destabilization or reorganization of the water molecules around solute cavities that arise from cancellation of the electrostatic field. The solvent environment, possibly supplemented by some specific solvent molecules, may help place the solute molecule in a cavity whose surroundings are characterized by an infinite polarizable dielectric medium. This behavior suggests that hydrophobic residues at a protein surface could easily contact the side chains of other nearby residues through the solvent environment, instead of by direct intra-molecular interactions.

• 한국수산과학회지
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• 제49권6호
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• pp.815-822
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• 2016

The cationic biopolymer chitosan has several applications in medicine. Chitosan is the deacetylated derivative of chitin, the second most abundant naturally occurring polymer. Recent studies have investigated the relationship between chitosan and antibacterial activity. However, the molecular interactions and mechanisms have not been detailed. This study used molecular dynamics simulations to study interactions between chitosan and anionic bacterial membranes (POPE-POPG) and electrically neutral non-bacterial membranes (POPC). We calculated the free energy using umbrella sampling to compare the interactions between membranes and chitosan in different protonation states. Fully protonated chitosan interacted most strongly with the bacterial membranes, but weakly with non-bacterial membranes. These results suggest that electrostatic interactions are the main mechanism of the antibacterial activity of chitosan, and they provide insights into the design of novel antibacterial and antimicrobial agents.

• 약학회지
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• 제35권6호
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• pp.461-465
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• 1991

Silica-based gel filtration chromatography has been used to characterize molecular weight of proteins. However, the molecular weight measured by this method was distorted by protein-silica interactions like hydrophobic and electrostatic forces. Therefore, we characterized protein-silica interaction using two forms of phytochrome (124 kDa) having different hydrophobicity and surface charge. PH and ionic strength affected the retention time of phytochrome suggesting that electrostatic force is the major interaction between protein and silica surface.

• 대한화학회지
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• 제58권6호
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• pp.560-568
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• 2014

단백질 폴딩 반응에서 정전기적 상호작용의 역할을 라이신 29를 알라닌으로 치환한 변이 유비퀴틴을 사용하여 탐색하였다. 유비퀴틴의 입체구조에서 라이신 29의 곁사슬은 글루탐산 16과 아스파르산 21의 곁사슬과 근접한 거리에 있어서 곁사슬끼리 정전기적 상호작용을 통하여서 삼차원 입체구조를 안정화시킬 것으로 예측되었다. 라이신을 알라닌으로 치환하여 정전기적 상호작용을 제거하였을 때 유비퀴틴의 native state의 구조적 안정성이 ~20% 감소한 점은 라이신 29에 의한 정전기적 상호작용이 단백질 삼차구조의 안정성에 상당히 기여하고 있다는 점을 시사하였다. 폴딩 반응의 진행 과정을 stopped-flow 장치로 측정한 folding kinetics 실험은 이전에 관찰된 것과 마찬가지로 unfolded state에서 native state로 진행하는 과정에 중간단계를 거치는 three-state on-pathway 메커니즘을 따르는 것으로 나타났다. 더욱이 라이신 29에 의한 정전기적 상호작용이 중간단계의 구조적 안정성에 기여하는 정도가 native state의 구조적 안정성에 기여하는 정도의 ~55%인 것으로 나타났다. 이는 유비퀴틴 폴딩의 중간단계의 구조도 라이신 29에 의한 정전기적 상호작용에 의하여 상당히 안정화 된다는 것을 의미하며 따라서 정전기적 상호작용이 단백질 삼차원 입체구조의 골격이 완성된 폴딩의 마지막 단계에 형성되어 단백질 native state의 안정성에만 기여하는 것이 아니라 중간단계가 형성되는 폴딩 반응의 초기에도 형성되어 폴딩 반응을 이끌어가는데도 기여한다는 것을 의미한다.

• 한국전산유체공학회지
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• 제13권4호
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• pp.58-65
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• 2008

In the present study, a numerical analysis on electrohydrodynamics (EHD) of the flow and the collection mechanisms inside a electrostatic precipitator with a spiral spike electrode were investigated. The phenomena of the electrostatic precipitator include complex interactions between the electric field, the fluid flow and the particle motion. To validate the numerical method, the numerical computation for the electric field of a simple wire-pipe type electrostatic system having an analytic solution were performed. Using this numerical method, the electric field of the spiked electrostatic precipitator was simulated. And the fluid flow and the particle motion inside the spiked electrostatic precipitator were numerically analyzed.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.276-282
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• 2008

In the present study, a numerical analysis on electrohydrodynamics (EHD) of the flow and the collection mechanism inside a electrostatic precipitator were investigated. The phenomena of the electrostatic precipitator include complex interactions between the electric field, the fluid flow and the particle motion. To validate the numerical method, the numerical computation for the electric field of a simple wire-pipe type electrostatic system having an analytic solution were performed. Using this numerical method, the electric field of the spiked electrostatic precipitator was simulated. And the fluid flow and the particle motion inside the spiked electrostatic precipitator were numerically analyzed.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.276-282
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• 2008

In the present study, a numerical analysis on electrohydrodynamics (EHD) of the flow and the collection mechanism inside a electrostatic precipitator were investigated. The phenomena of the electrostatic precipitator include complex interactions between the electric field, the fluid flow and the particle motion. To validate the numerical method, the numerical computation for the electric field of a simple wire-pipe type electrostatic system having an analytic solution were performed. Using this numerical method, the electric field of the spiked electrostatic precipitator was simulated. And the fluid flow and the particle motion inside the spiked electrostatic precipitator were numerically analyzed.

• 대한기계학회논문집
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• 제18권12호
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• pp.3270-3275
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• 1994

Particle trajectory visualization using laser sheet was performed to investigate the corona wind flow interactions in the one-wire and two-wire type electrostatic precipitators. The corona wind generated by corona discharge was not negligible, and strong flow interactions took place owing to the induced circulatory cells. In the case of one-wire type, as the applied voltage was increased and the cross-section mean velocity was decreased, the effect of corona wind became active. In the case of two-wire type, if upstream discharge voltage was relatively higher than downstream discharge voltage, the effect of upstream corona wind was reduced.

• Membrane and Water Treatment
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• 제14권3호
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• pp.121-128
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• 2023

This study introduces a NaOH/Zn-assisted hydrothermal method for the synthesis of zeolites derived from coal ash (CA). A zeolite/Zn adsorbent is successfully prepared by the activation of CA with NaOH and Zn; it is characterized by a high surface area and a negative surface charge.Methylene blue (MB) and methyl orange (MO) are selected as dye pollutants, and their adsorption onto the zeolite/Zn adsorbent is investigated. Results show the high adsorption capacities of MB and MO and that the negative surface charge facilitates electrostatic interactions between the adsorbates and adsorbents. The zeolite/Zn adsorbents shows the selective adsorption of positively charged dye MB via electrostatic interactions between the =NH+ group (positive dipole) and the oxygen functional group of the adsorbents (negative dipole). The selectivity for the positively charged dye is sufficiently high, with the removal efficiency reaching 99.41% within 10 min. By contrast, the negatively charged dye MO exhibits negligible absorption. These findings confirm the role of electrostatic interactions in the adsorption of MB, in addition to the effect of a large surface area. The results of this study are expected to facilitate the development of simple, eco-friendly, and cost-effective zeolite-based adsorptive composites from CA residuals for the selective removal of dye pollutants from CA waste.