• Journal of Photoscience
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• 제9권2호
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• pp.33-36
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• 2002

In vertebrate rhodopsins the glutamic acid at position 113 serves as a counterion to stabilize the protonated retinylidene Schiff base linkage and to shift the spectrum to the visible region. Invertebrate rhodopsins and retinochrome have the amino acid residue different from glutamic acid or asparatic acid at this position and therefore, these pigments may have a counterion at different position. We first investigated the counterion in retinochrome by site specific mutagenesis. The results showed that the counterion is the glutamic acid at position 181, where almost of all the pigments including vertebrate and invertebrate rhodopsins in the rhodopsin family have a glutamic acid or an aspartic acid. In vertebrate rhodopsins, however, Glu 181 does not act as a counterion, and the red-sensitive cone pigments have a histidine at this position, which serves as a chloride-binding site for red-shift of the absorption spectrum. These findings suggested that the role of Glu181 as a counterion may be weakened by the newly acquired counterion at position 113. Taken together with our recent studies on an invertebrate-type rhodopsin, the rhodopsin diversity was discussed from viewpoint of counterion.

• Bulletin of the Korean Chemical Society
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• 제12권4호
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• pp.411-413
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• 1991

The effects of electrolyte on the critical micelle concentration (cmc) and bromide counterion binding in the micelles of cetylpyridinium bromide (CPB) have been investigated by UV spectroscopy and conductance measurements. Salts used in this study decreased cmc in the order $Cl^-\;<\;Br^-\;<\;NO3^-$ (which parallels the lyotropic series for the inorganic anions) and the effects on cmc followed the equation proposed by Shinoda: log cmc = A - B log (cmc + [NaX]). In the equation, constant B represents the counterion binding to the micelles at cmc and for the micelle of CPB at $25^{\circ}C$, B=80.76%. The association constant for the binding of counterions to long chain cations within micelles was also derived from the cmc values and counterion binding constant to the micelles.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.142.1-142.1
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• 2003

Sensitive and safe method for visualization of DNA in agarose gels using visible dye is described. To improve the sensitivity, we studied a counterion-dye staining method using methyl orange as a counterion-dye which contributes to reduce excessive background staining by indoine blue. Dye concentrations, PH of staining solution, mixing molar ratio of two dyes, and staining times were optimized for the counterion-dye staining. By the staining with a mixed solution of 0.005% indoine blue and 0.00165% methyl orange in 10% ethanol 0.2M sodium acetate, 8 ng of the 3 kb DNA in an agarose gel was detected within 1hr. (omitted)

• 폴리머
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• 제24권6호
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• pp.802-809
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• 2000

Poly(L-glutamic acid) (PLGA)와 PVA 블렌드막을 제조한 후, ethanol 수용액중에서 막증의 polypeptide 사슬의 2차구조 전이거동에 미치는 용매조성 및 대이온종의 영향과 알칼리 금속 이온 (Li, na, K, Cs)에 대한 투과특성을 조사하였다. 막중 PLG 알칼리 금속염의 helix 형성거동에 있어 대이온 선택성은 Li>Na>K>Cs의 순으로 관찰되었고, 이와 같은 특이성은 탈용매화 에너지와 정전에너지의 감소에 따른 고분자 하전기와 대이온과의 contact ion-pair 형성에 의한 것으로 설명하였다. 또한 PLGA/PVA 블렌드막의 ethanol 수용액 중에서의 알칼리 금속이온의 투과거동을 살펴보면, ethanol 농도가 점차 증가함에 따라 K, Cs의 경우는 투고도가 증가한, Li, Na의 경우에는 감소하였다. K, Cs 이온의 경우 대이온과 염소이온간의 ion-pair (M$^{+}{\cdot}$Cl$^{-}$)형성에 의한 Donnan배제효과의 감소와 중성염 형태로의 분배량 증가때문인 것으로, Li, Na 이온의 경우 막중의 coil-helix 구조전이에 따른 자유체적의 감소와 고분자 하전기와의 상호작용이 증가하여 확산성이 크게 감소하였기 때문인 것으로 생각된다.

• Bulletin of the Korean Chemical Society
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• 제33권11호
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• pp.3719-3726
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• 2012

Formation of Z-DNA, a left-handed double helix, from B-DNA, the canonical right-handed double helix, occurs during important biological processes such as gene expression and DNA transcription. Such B-Z transitions can also be induced by high salt concentration in vitro, but the changes in the relative stability of B-DNA and Z-DNA with salt concentration have not been fully explained despite numerous attempts. For example, electrostatic effects alone could not account for salt-induced B-Z transitions in previous studies. In this paper, we propose that the B-Z transition can be explained if counterion entropy is considered along with the electrostatic interactions. This can be achieved by conducting all-atom, explicit-solvent MD simulations followed by MM-PBSA and molecular DFT calculations. Our MD simulations show that counterions tend to bind at specific sites in B-DNA and Z-DNA, and that more ions cluster near Z-DNA than near B-DNA. Moreover, the difference in counterion ordering near B-DNA and Z-DNA is larger at a low salt concentration than at a high concentration. The results imply that the exclusion of counterions by Z-DNA-binding proteins may facilitate Z-DNA formation under physiological conditions.

• 한국막학회:학술대회논문집
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• 한국막학회 1997년도 추계 총회 및 학술발표회
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• pp.131-132
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• 1997

1. 서론 : 이온 복합막은 투과증발을 통한 유기수용액의 탈수에 있어서 높은 수투과유량과 선택도를 나타내는 것으로 알려져 있다. 그러나 장시간 운전시에 이온 복합막은 막표면에 있는 금속 counterion이 feed에 씻겨버리기 때문에 분리능의 급격한 감소를 띠게 된다. counterion이 유기물일 경우에는 막속으로 확산되어 우기농축물에 포함될 문제가 있다. counterion이 고분자이면, 막 효능의 안정성이 증가되지만 막 제조과정이 다소 어려워진다. 아크릴산과 스티렐폰산을 포함하고 있는 개질 PAN막을 이용한 피리딘 수용액의 탈수에 관한 이전의 연구에서, 피드내의 피리딘과 막내의 산 기능기 사이에 형성된 in-situ complex가 막의 투과물사이에 특별한 반응이 없거나 막과 주요 투과 물간에 수소결합이 있는 막보다 더 좋은 탈수 효능을 나타냄이 확인되었다. 본 연구에서는 포스페이트를 함유하고 있는 폴리아크릴로니트릴 막의 제조와 피리딘 수용액의 탈수 효능에 대해 언급할 것이다.

• Bulletin of the Korean Chemical Society
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• 제10권2호
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• pp.134-137
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• 1989

The reaction of $CpMo(CO)_3-M^+(M^+,\;Li^+,\;Na^+,\;K^+,\;PPN^{+a})$ with allyl halide was performed and the details of its counterion effects and solvent effect was investigated under the pseudo-first order conditions. The kinetic data from this reaction were compared with those from the reaction of the same anion with benzyl halides in terms of their inverse counterion effects.

• Biotechnology and Bioprocess Engineering:BBE
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• 제6권4호
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• pp.279-283
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• 2001

Cationic lipid emulsion system consisting of 1, 2-dioleoyl-sn-slycero-3-trimethyl-ammonium-propane(DOTAP) and plasmin DNA with various counterions in the lipid headgroups were prepared. The transfection activity of the cationic lipid emulsion systems was then investigated in vitro and in vivo. The complex formation of plasmid DNA lipid emulsion was affected by the counterions through charged headgroup repulsion and also by the salt concen-tration in the media. As such , the transfection activity of the DOTAP emulsion system can be controlled by changing the counterions.

• Bulletin of the Korean Chemical Society
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• 제31권9호
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• pp.2571-2574
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• 2010

We investigate the mechanism of $S_NAr$ fluorination reactions under the influence of protic solvents and ions. We find that counterion or protic solvent alone retards the $S_NAr$ reactions, but together they may promote the reaction. In this mechanism, the protic solvent acts on the counterion as a Lewis base, and the nucleophile reacts as an ion pair. We also show that an anion (mesylate) may exhibit catalytic effects, suggesting the role of ionic liquids for accelerating the $S_NAr$ reactions.

• 한국응용과학기술학회지
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• 제27권4호
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• pp.545-551
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• 2010

Hydrophobically monoendcapped poly(sodium acrylate)s formed hydrophobic microdomains in water. This was concluded on poly(sodium acrylate)s with a linear $C_{12}$-alkyl chain attached specifically at the end of the polymer. There was no well defined CMC (critical micelle concentration), but rather a gradual transition from a micelle free solution to a micelle solution. Steady state fluorescence spectroscopy indicates that the micro domains are rather hydrophobic. At pH 5 in the abscence of salt and at pH 9 in the prescence of 1 M sodium citrate the CAC (critical aggregation concentration) was in the range of 0.1 to 2.4 mM. However at pH 5 there was a linear increase in the transition concentration with a head-group size due to an increase in steric and electrostatic repulsions between polymer main chains. At pH 9 in the abscence of salt the transition concentration was in the range of 1 to 80 mM. For the larger polymers there was a effect which consisted of a concentration gradient of sodium counterion toward the hydrophobic domain. The effect was larger for the larger polymers because of the higher total sodium concentration and the less steep counterion concentration gradient.