• 제목/요약/키워드: molecular charge

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Adsorption of Three Chlorinated Herbicides on Two Activated Carbons: An Example of the Effect of Surface Charge, Pore Diameter and Molecular Size on the Adsorption Process

  • Pila Matias N.;Colasurdo Diego D.;Simonetti Sandra I.;Dodero Gabriela A.;Allegretti Patricia E.;Ruiz Danila L.;Laurella Sergio L.
    • Korean Chemical Engineering Research
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    • 제61권1호
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    • pp.97-108
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    • 2023
  • Two carbonaceous adsorbents CAT and CARBOPAL were tested for reducing the concentration of the three herbicides in water: 2,4-D (2,4-dichlorophenoxyacetic acid), TCP (2,4,6-trichlorophenol) and metolachlor. Textural and chemical characterization of the adsorbents include nitrogen isotherms, FTIR, titration and thermogravimetric analyses. Adsorption was studied in discontinuous adsorption experiments at different pH values. The experimental adsorption isotherms data were fitted to four theoretical models. Adsorbent characterization reveals that CAT has higher micropore area, lower pore diameter and lower acidity than CARBOPAL. The adsorption is a second-order process and the isotherms best fitted to Sips model. The efficiency of the process depends mainly on the charge of the adsorbate for TCP and 2,4-D, but it depends on the charge of the surface for metolachlor. Adsorption capacity is higher on CAT for 2,4-D and TCP (small molecules), and it is higher on CARBOPAL for metolachlor (large molecules). Theoretical calculations clearly support this assumption.

알루미늄 허니컴(HC) 구조재 적용 주조형 복합화약 (Structural Support of Aluminum Honeycomb on Cast PBX)

  • 김성한;이근득;박하늘;한민구
    • 한국군사과학기술학회지
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    • 제27권2호
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    • pp.222-229
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    • 2024
  • As the operating condition for the penetrating missile has been more advanced, the survivability of main charge has been strongly required when the warhead impacts the target. Lots of efforts to desensitize explosives such as the development of insensitive molecular explosives or optimizing plastic-bonded explosives(PBX) systems has been made to enhance the survivability of main charge. However, these efforts face their limits as the weapon system require higher performance. Herein, we suggest a new strategy to secure the survivability of main charge. We applied structurally supportable aluminum honeycomb(HC) structure to cast PBX. The aluminum HC structure reinforces the mechanical strength of cast PBX and helps it to withstand external pressure without the reaction like detonation. In this study, impact resistance character, shock sensitivity and internal blast performance of PBXs reinforced with HC structure were investigated according to the application of aluminum HC structure. The newly suggested aluminum HC structure applied to cast PBX was proved to be a promising manufacturing method available for high-tech weapon systems.

Analysis of the solution structure of the human antibiotic peptide dermcidin and its interaction with phospholipid vesicles

  • Jung, Hyun-Ho;Yang, Sung-Tae;Sim, Ji-Yeong;Lee, Seung-Kyu;Lee, Ju-Yeon;Kim, Ha-Hyung;Shin, Song-Yub;Kim, Jae-Il
    • BMB Reports
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    • 제43권5호
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    • pp.362-368
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    • 2010
  • Dermcidin is a human antibiotic peptide that is secreted by the sweat glands and has no homology to other known antimicrobial peptides. As an initial step toward understanding dermcidin's mode of action at bacterial membranes, we used homonuclear and heteronuclear NMR to determine the conformation of the peptide in 50% trifluoroethanol solution. We found that dermcidin adopts a flexible amphipathic $\alpha$-helical structure with a helix-hinge-helix motif, which is a common molecular fold among antimicrobial peptides. Spin-down assays of dermcidin and several related peptides revealed that the affinity with which dermcidin binds to bacterial-mimetic membranes is primarily dependent on its amphipathic $\alpha$-helical structure and its length (>30 residues); its negative net charge and acidic pI have little effect on binding. These findings suggest that the mode of action of dermcidin is similar to that of other membrane-targeting antimicrobial peptides, though the details of its antimicrobial action remain to be determined.

Fabrication and Characterization of Dye-sensitized Solar Cells based on Anodic Titanium Oxide Nanotube Arrays Sensitized with Heteroleptic Ruthenium Dyes

  • Shen, Chien-Hung;Chang, Yu-Cheng;Wu, Po-Ting;Diau, Eric Wei-Guang
    • Rapid Communication in Photoscience
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    • 제3권1호
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    • pp.16-19
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    • 2014
  • Anodic self-organized titania nanotube (TNT) arrays have a great potential as efficient electron-transport materials for dye-sensitized solar cells (DSSC). Herewith we report the photovoltaic and kinetic investigations for a series of heteroleptic ruthenium complexes (RD16-RD18) sensitized on TNT films for DSSC applications. We found that the RD16 device had an enhanced short-circuit current density ($J_{SC}/mAcm^{-2}=15.0$) and an efficiency of power conversion (${\eta}=7.2%$) greater than that of a N719 device (${\eta}=7.1%$) due to the increasing light-harvesting and the broadened spectral features with thiophene-based ligands. However, the device made of RD17 (adding one more hexyl chain) showed smaller $J_{SC}(14.1mAcm^{-2})$ and poorer ${\eta}(6.8%)$ compare to those of RD16 due to smaller amount of dye-loading and less efficient electron injection for the RD17 device than for the RD16 device. For the RD18 dye (adding one more thiophene unit and one more hexyl chain), we found that the device showed even lower $J_{SC}(13.2mAcm^{-2}) $ that led to a poorest device performance (${\eta}=6.2%$) for the RD18 device. These results are against to those obtained from the same dyes sensitized on $TiO_2$ nanoparticle films and they can be rationalized according to the electron transport kinetics measured using the methods of charge extraction and transient photovoltage decays.

비스 방향족 ${\alpha},{\beta}$ 불포화 케톤 유도체 중 2-thienyl 및 2-furyl 치환체의 항균활성에 관한 비교분자장 분석(CoMFA) (Comparative molecular field analysis(CoMFA) on the fungicidal activity of 2-thienyl and 2-furyl substituents in bis-aromatic ${\alpha},{\beta}$-unsaturated ketone derivatives)

  • 성낙도;유성재;임치환;적송미기
    • 농약과학회지
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    • 제2권2호
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    • pp.16-21
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    • 1998
  • 비스 방향족 ${\alpha},{\beta}$-불포화 케톤 유도체의 헤테로 방향족고리($R_{1}$) 치환체중 치환 phenyl backbone($R_{2}$)들의 구조변환에 따른 벼도열병균(Pyricularia oryzae)과 토마토역병균(Phytophthora irifestans)에 대한 in vivo에서의 항균활성 관계(SAR)를 3-D QSAR 방법인 비교분자장 분석(CoMFA)으로 해석하였다. 두 식물병원균에 대한 항균활성을 설명하는 CoMFA결과는 2-D QSAR에서 검토된 결과와 유사한 경향이었으며 입체효과(Es)와 전자효과(${\sigma}$)로 설명할 수 있었다. 즉, 벼도열병균은 aryl group에 bulky한 치환기(Es>0)가 도입되어야 하며 ${\beta}$탄소원자의 양하전이 증가할수록 강한 항균활성을 나타낼것으로 기대되었다. 반면, 토마토역병균의 경우에는 aryl group에 체적이 작은 치환기가 도입될수록, 그리고 ${\beta}$ 탄소원자의 양하전이 감소할수록 강한 항균활성을 나타낼 것으로 기대 되었다. 또한, 입체효과와 전자효과를 등 고도로 나타낸 CoMFA결과가 기존의 2-D QSAR보다 항균활성에 미치는 화합물의 구조적 요인을 보다 구체적으로 제시할 수 있었다.

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RF 스퍼터링에 의해 제조된 Li-Ni-O 박막의 전기변색 특성 (RF Sputtered Lithium Nickel Oxide Films and Their Electrochromism)

  • 김영일;김배환;최진호;;박남규
    • 대한화학회지
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    • 제41권11호
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    • pp.594-599
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    • 1997
  • RF 스피터링법을 써서 $Li_{2x}Ni_{1-x}O$ 박막을 제조하였으며, 그 과정에서 기판의 온도$(50/230^{\circ}C)와$ 분위기 $(Ar/O_2)$를 변수로써 막의 미세구조를 조절하였다. 투과전자현미경을 이용한 막 구조 분석에 의해 낮은 기판 온도와 $O_2$ 조건에서 막의 조성입자가 작아짐을 관찰하였고, $50^{\circ}C/O_2$ 하에서 얻이진 $Li_{2x}Ni_{1-x}O$ 박막은 약 $80\AA$ 크기의 입자로 이루어져 있었다. 전기화학적 조건 하에서 $Li_{2x}Ni_{1-x}O$ 박막의 변색현상을 조사한 결과, 박막의 미세구조 발달에 의해 $Li^+$ 이온의 가역적 수용량이 증가하고, 결과적으로 전기변색 기능이 향상됨을 알 수 있엇다. 50 $^{\circ}C/O_2$ 하에서 얻어진 170 nm 두께의 $Li_{2x}Ni_{1-x}O$ 박막은 30 mC/$cm^2$$Li^+$ 이온 수용력과 함께 약 1.3의 흡광밀도(OD)를 나타내었다.

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Molecular Dynamics Simulation and Density Functional Theory Investigation for Thiacalix[4]biscrown and its Complexes with Alkali-Metal Cations

  • Hong, Joo-Yeon;Lee, Che-Wook;Ham, Si-Hyun
    • Bulletin of the Korean Chemical Society
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    • 제31권2호
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    • pp.453-456
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    • 2010
  • The structural and energetic preferences of thiacalix[4]biscrown-5 with and without alkali metal ions ($Na^+$, $K^+$, $Rb^+$, and $Cs^+$) have been theoretically investigated for the first time using molecular dynamic (MD) simulations and density functional theory (MPWB1K/6-31G(d)//B3LYP/6-31G(d)) methods. The formation of the metal ion complex by the host is mainly driven by the electrostatic attraction between crown-5 oxygens and a cation together with the minor contribution of the cation-$\pi$ interaction between two facing phenyl rings around the cation. The computed binding energies and the atomic charge distribution analysis for the metal binding complexes indicate the selectivity toward a potassium ion. The theoretical results herein explain the experimentally observed extractability order by this host towards various alkali metal ions. The physical nature and the driving forces for cation recognition by this host are discussed in detail.

Self-Assembled and Alternative Porphyrin-Phthalocyanine Array

  • Kwag, Gwang-Hoon;Park, Eun-Joo;Kim, Sung-Hyun
    • Bulletin of the Korean Chemical Society
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    • 제25권2호
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    • pp.298-300
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    • 2004
  • An alternative molecular porphyrin-phthalocyanine aggregate was prepared and characterized with UV-visible and X-ray absorption spectroscopies. UV-visible experiments evidence 1-dimensional porphyrin-phthalo-cyanine array formed by mixing $SnTPPCl_2 ({\lambda}_{max}=429,\;{\varepsilon}=2.4{\times10^ 5 /M{\cdot}cm)\;and\;NiPc(OBu)_8({\lambda}_{max}=744 nm,\;{\varepsilon}= 2.0{\times}10^ 5 /M{\cdot}cm)$ in solution. In the UV-visible spectrum of the porphyrin-phthalocyanine array, $(SnPNiPc)_n$, a new Q-band appeared at 844 nm with decrease of the Q-band peak of $NiPc(OBu)_8$ at 744 nm. The red-shift of Q-band evidences an alternative porphyrin-phthalocyanine array formed in solution through metal-halide interaction rather than ${\pi}-{\pi}$ facial interaction, in which nickel of $NiPc(OBu)_8$ coordinates with chloride of $SnTPPCl_2$ through self assembly. Ni K-edge XANES (X-ray absorption near edge structure) spectra also support the axial ligation of nickel to chloride. The square planar structure of $NiPc(OBu)_8$ turns to an octahedral structure in (SnPNiPcSnP) by axial ligation. A higher energy-shift (0.2 eV) of the preedge peak of (SnPNiPcSnP) indicaties partial oxidation of nickel by charge transfer from NiPc$(OBu)_8$ to SnTPPCl$_2$.

EFFECT OF THE WATER-WALL INTERACTION POTENTIALS ON THE PROPERTIES OF AQUEOUS SOLUTIONS CONFINED WITHIN A UNIFORMLY CHARGED NANO-CHANNEL

  • Hoang, H.;Kang, S.;Suh, Y.K.
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2009년 춘계학술대회논문집
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    • pp.368-376
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    • 2009
  • Studies on the effect of the wall-ion, wall-water, water-ion and ion-ion interaction on properties of water and ions in nano-channels have been performed through the use of different kinds of ions or different models of potential energy between wall-ion or wall-water. On this paper, we address the effect of water-wall interaction potential on the properties of confined aqueous solution by using the molecular dynamics (MD) simulations. As the interaction potential energies between water and wall we employed the models of the Weeks-Chandler-Andersen (WCA) and Lennard-Jones (LJ). On the MD simulations, 680 water molecules and 20 ions are included between uniformly charged plates that are separated by 2.6 nm. The water molecules are modeled by using the rigid SPC/E model (simple point charge/Extended) and the ions by the charged Lennard-Jones particle model. We compared the results obtained by using WCA potential with those by LJ potential. We also compared the results (e.g. ion density and electro-static potential distributions) in each of the above cases with those provided by solving the Poisson-Boltzmann equation.

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Histone Deacetylase in Carcinogenesis and Its Inhibitors as Anti-cancer Agents

  • Kim, Dong-Hoon;Kim, Min-Jung;Kwon, Ho-Jeong
    • BMB Reports
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    • 제36권1호
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    • pp.110-119
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    • 2003
  • The acetylation state of histone is reversibly regulated by histone acetyltransferase (HAT) and deacetylase (HDAC). An imbalance of this reaction leads to an aberrant behavior of the cells in morphology, cell cycle, differentiation, and carcinogenesis. Recently, these key enzymes in the gene expression were cloned. They revealed a broad use of this modification, not only in histone, but also other proteins that involved transcription, nuclear transport, and cytoskeleton. These results suggest that HAT/HDAC takes charge of multiple-functions in the cell, not just the gene expression. HDAC is especially known to play an important role in carcinogenesis. The enzyme has been considered a target molecule for cancer therapy. The inhibition of HDAC activity by a specific inhibitor induces growth arrest, differentiation, and apoptosis of transformed or several cancer cells. Some of these inhibitors are in a clinical trial at phase I or phase II. The discovery and development of specific HDAC inhibitors are helpful for cancer therapy, and decipher the molecular mode of action for HDAC.