• 대한화학회지
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• 제33권4호
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• pp.357-365
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• 1989

제올라이트 A($Na_{12}Al_{12}Si_{12}O_{48}$ ; $Na_{12}-A$)를 $Mg^{2+}$, $Ca^{2+}$, $Zn^{2+}$ 및 $Co^{2+}$ 등의 2가 이온으로 치환하여 얻어진 $Mg_4Na_4Al_{12}Si_{12}O_{48}$($Mg_4Na_4-A$), $Ca_6Al_{12}Si_{12}O_{48}$($Ca_6-A$), $Zn_5Na_2Al_{12}Si_{12}O_{48}$($Zn_5Na_2-A$) 및 $Co_4Na_4Al_{12}Si_{12}O_{48}$($Co_4Na_4-A$)의 수화구조와 탈수구조에 있어서 골조원자, 양이온 및 물분자들의 위치와 에너지를 몇가지 퍼텐셜 함수를 써서 계산하여 구하였다. 탈수가 될 때 양이온은 수화구조에서의 6-ring이나 8-ring의 골조산소 쪽으로 이동하였으며 일반적으로 2가 이온치환 제올라이트 A가 완전탈수될 때는 그 골조가 제올라이트 A의 골조보다 불안정하였다. 수화상태의 경우 골조내에는 인접물분자 또는 골조산소원자와 수소결합하는 물; W(III), $Na^+$ 이온에 배위된 물; W(II) 및 2가 이온에 배위되는 물; W(I) 등이 존재하였으며 이들 세 그룹의 물분자들의 탈수에 대응하는 세개의 DTA 흡열피크를 관측하였다.

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 1999년도 학술발표회 진행표 및 논문초록
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• pp.26-27
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• 1999

Ionic currents through many different cation channels are specifically reduced by internal and/or external $Mg^{2＋}$ within a concentration range of physiological relevance. Although there are many ways for a divalent cation to reduce channel currents, the current blockade by directly binding to a conduction pore has been most well studied.(omitted)

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 2001년도 학술 발표회 진행표 및 논문초록
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• pp.37-37
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• 2001

Cyclic nucleotide-gated (CNG) channels are composed of homo or hetero tetramer of ${\alpha}$ and ${\beta}$ subunits. The a subunits of these channels have a conserved glutamate residue within the pore-forming region. This residue determines the selectivity as well as the affinity for the extracellular divalent cations. Using the high affinity mutant (E363D) of bovine retinal CNG channel in which the Glu was replaced to Asp at position 363, we constructed tandem dimers and investigated the binding symmetry of divalent cation to the site.(omitted)

• 광물과 암석
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• 제35권3호
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• pp.345-353
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• 2022

본 연구는 합성 모데나이트(Na_6.6Al_6.6Si_41.4O₉₆·20.4H₂O, Na-MOR)를 이용한 다양한 중금속의 포획 연구를 하기 위한 기초 단계로, 고분해능 X-선 분말 회절을 이용하여 치환체의 격자상수 및 부피 변화를 이해하기 위한 목적으로 실험을 진행하였다. 열중량 분석법(Thermogravimetric analysis, TGA)으로 측정한 결과, 1가 양이온 치환체(Cs-MOR, Na-MOR)는 단위포 당 19.4, 20.4개의 물분자가 존재하였으며, 2가 양이온 치환체(Pb-MOR, Sr-MOR, Cd-MOR)는 단위포 당 21, 23.1, 23.2개가 존재하는 것을 확인하였다. 측정한 모든 물질은 사방정계에 속하는 Cmcm의 공간군을 가지는 것으로 확인할 수 있었다. 치환 전 물질인 Na-MOR과 비교했을 때, 치환체의 (110)면과 (200)면의 회절강도가 명확하게 변화하였으나, 전체적인 피크의 위치는 거의 유사하게 나타나는 것을 확인할 수 있었다. 또한 Na-MOR에서는 확인이 되지 않았던 (220)면의 피크가 Pb-, Cd-, Sr-MOR에서 뚜렷하게 관찰되었다. 이를 통해서 양이온 치환에 따른 원자들의 분포 변화가 주로 ab-평면상에서 나타나지만, 격자상수의 변화는 미세할 것으로 짐작할 수 있었다. Whole profile fitting 방법을 사용하여 치환된 모데나이트의 미세한 격자상수의 변화를 관찰하였다. 치환체의 격자상수 및 격자부피의 변화는 치환된 양이온의 반경 및 전하수에 따라 서로 다른 경향성을 보였다. 1가 양이온의 경우, 이온반경이 증가할수록 a-축의 길이는 증가하지만, 반면에 b- 및 c-축의 길이는 감소하였다. 2가 양이온의 경우, 이온반경이 증가할수록 대체적으로 a-축의 길이가 감소하고, b- 및 c-축의 길이는 증가하였다. 격자부피는 1가 또는 2가 양이온 치환체들이 각각 독립된 경향성을 가지며, 이온반경에 따라 증가하는 것을 확인할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2669-2674
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• 2012

Crown ether is one of well-known host molecules and able to selectively sequester metal cation. We employed M06-2X density functional theory with IEFPCM and SMD continuum solvation models to study selectivity of dibenzo-18-crown-6-ether (DB18C6) for alkaline earth dications, $Ba^{2+}$, $Sr^{2+}$, $Ca^{2+}$, and $Mg^{2+}$ in the gas phase and in aqueous solution. $Mg^{2+}$ showed predominantly strong binding affinity in the gas phase because of strong polarization of CO bonds by cation. In aqueous solution, binding free energy differences became smaller among these dications. However, $Mg^{2+}$ had the best binding, being incompatible with experimental observations in aqueous solution. The enthalpies of the dication exchange reaction between DB18C6 and water cluster molecules were computed as another estimation of selectivity in aqueous solution. These results also demonstrated that $Mg^{2+}$ bound to DB18C6 better than $Ba^{2+}$. We speculated that the species determining selectivity in water could be 2:1 complexes of two DB18C6s and one dication.

• 한국동물학회지
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• 제22권4호
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• pp.141-152
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• 1979

고양이 백혈병 바이러스에서 reverse transcriptase를 분리하여 생화학적 및 면역학적 연구를 하였다. 분자량은 72,000이고, DNA polymerase와 RNase H의 활성은 0.05-1 mM $M_n^2+$와 50-80 mM KCl에서 가장 좋았다. DNA polymerase와 RNase H는 같은 단백질 분자에 있으며, chymotrypsin 처리로서 RNase H를 쪼개낼 수 있으며, 이 RNase H도 reverse transcriptase의 항체에 의해서 활성이 거의 억제 된다. Reverse transcriptase의 항체 결합위치와 활성을 내는 위치는 다른 것 같다.

• 한국물환경학회지
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• 제21권3호
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• pp.242-247
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• 2005

In this study, we investigated the removal efficiencies of pollutants and permeate fluxes depending on chemistry of feed water, various molecular weight cut-offs (MWCOs) and materials of membrane, operating pressure. We used seven MWCO membranes of YC0.5, YM1, YM3, YM10, YM30, YM100 and PM30, humic acid solution and surface water as feed water, and examined variation in permeate flux. Results of TOC removal experiment demonstrate that MWCO lower 1,000daltons could remove humic acid effectively. As increasing solution pH and decreasing divalent cations ($Ca^{2+}$) concentration, TOC removal increased. But $UV_{254}$ removal efficiency increased with higher divalent cation concentration and solution pH. Membrane fouling increased with increasing electrolyte (NaCl), divalent cation concentration and decreasing solution pH. In spite of initial permeate flux of the hydrophobic membrane (PM30) was higher than that of the hydrophilic membrane (YM30), flux decline of PM30 was significant during operation. At higher operating pressure, compactness of the cake layer on the membrane surface increased, resulting in gradual increase in hydraulic resistance.

• International Journal of Industrial Entomology and Biomaterials
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• 제27권2호
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• pp.326-328
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• 2013

Sericin undergoes gelation by the structural transition from random coil to b-sheet transition. In the present study, the gelation time of sericin solution was investigated in the presence of NaCl, KCl and $CaCl_2$. The addition of salts delayed the gelation time, and $CaCl_2$ had the most pronounced effect, which delayed about 8 h at maximum. The gelation time increased with the concentration of salt. The transition of secondary structure of sericin was retarded in the presence of salt. The effect of salts on the gelation time of sericin might be due to the solvation effect of relevant cation.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3681-3689
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• 2013

This study explored a direct SET-photochemical strategy to construct a new family of thioene conjugated-naphthalamide fluorophore based lariat-crown ethers which show strong binding properties towards heavy metal ions. Irradiations of designed nitrogen branched (trimethylsilyl)methylthio-terminated polyethylenoxy-tethered naphthalimides in acidic methanol solutions have led to highly efficient photocyclization reactions to generate naphthalamide based lariat type thiadiazacrown ethers directly in chemo- and regio-selective manners which undergo very facile secondary dehydration reactions during separation processes to produce their corresponding amidoenethio ether cyclic products tethered with electron donating diethyleneoxy- and diethyenethio-side arm chains. Fluorescence and metal cation binding properties of the lariat type enamidothio products were examined. The photocyclized amidoenethio products, thioene conjugated naphthalamide fluorophore containing lariat-thiadiazacrowns exhibited strong fluorescence emissions in region of 330-450 nm along with intramolecular exciplex emissions in region of 450-560 nm with their maxima at 508 nm. Divalent cation $Hg^{2+}$ and $Pb^{2+}$ showed strong binding to sulfur atom(s) in side arm chain and atoms in enethiadiazacrown ether rings which led to significant enhancement of fluorescence from its chromophore singlet excited state and concomitant quenching of exciplex emission. The dual fluorescence emission responses towards divalent cations might provide a new guide for design and development of fluorescence sensors for detecting those metals.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.1024-1027
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• 2002

In this study, we have investigated the substitutional effects of In ions with divalent ones in the $Srln_2O_4:Pr^{3+}$ phosphors and the relative change of the red and blue emissions. The substitutional Zn ions greatly intensified the blue emission band at 492 nm, but the red emission band at 608 nm was relatively less changed. On the other hand, Cd ions have no effect on the relative intensities. We explained the phenomena in connection with the distance of Pr-D, i.e., covalency experienced by a $Pr^{3+}$ion.