• Polymer(Korea)
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• v.35 no.6
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• pp.520-525
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• 2011

Superporous hydrogels (SPHs) with fast swelling and superabsorbent properties are useful materials in various biomedical fields, by improving the swelling properties of conventional hydrogels based on their unique porous structure. In this study, Eudragit polymers were used as coating materials to control the swelling properties of poly(acrylic acid-co-acrylamide) based SPHs by environmental pH. The SPHs were coated with Eudragit L100 and S100 that have different pH characteristics as enteric coating materials by a dip coating method, and their pH dependent swelling behaviors were observed in various pH environments. The swelling of SPHs was inhibited at a low pH range, but significantly enhanced above a characteristic pH of Eudragit polymers. This pH dependent swelling behavior of hydrogels could be modulated by the characteristics of the enteric coating polymers.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.739-742
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• 2003

Curdlan acetate was prepared from hydrophilic curdlan by chemical modification and it was used for pH-sensitive drug delivery system. Curdlan acetate microspheres were prepared by the solvent evaporation method. The size of the curdlan acetate microspheres was below $200\;{\mu}m$. The drug loading efficiency of microspheres was approximately 58.44%. In the swelling test, curdlan acetate microspheres were showed pH-sensitive behavior. The swelling capacity of microspheres at pH 7.4 was much greater than at pH 1.4. Also, Release rate of indomethacin (IND) at pH 7.4 from curdlan acetate microspheres was faster than that at pH 1.4. A pH-sensitive drug release pattern was due to the disintegrating after swelling.

• Journal of the Mineralogical Society of Korea
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• v.7 no.2
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• pp.91-96
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• 1994

중.저준위 방사성 폐기물의 대표적인 핵종인 137Cs, 90Sr에 대한 캐올리나이트의 흡착특성을 수용액의 이온강도와 pH의 영양하에서 알아보았다. 흡착실험은 회분식으로 하였고, 사용한 수용액은 NaCl, CaCl2, MgSO4, KCL 각각을 10-1, 10-2, 10-3, 10-4 mole/$\ell$로 하였다. 수용액광물 평형상태의 pH를 4.5, 7.0, 10.5로 조절하였다. 실험결과 캐올리나이트의 Cs, Sr 흡착은 이온강도와 pH에 상당한 영향을 받으며, Sr 흡차에 양이온들의 경쟁은 Ca2+ Mg2+>K+>Na+ 순을 보이고, Cs의 경우에는 K+>Ca2+ Mg2+>Na+의 순을 보인다. 이는 수용액상에서 이온들의 수호에너지와 관련되며, 광물입자와 이온들의 물구조변환특성에 의해 설명된다. Cs과 Sr 사이에 흡착우선성은 산성 내지 약알카리에서는 Cs이 Sr보다 흡착이 잘 되나, 강알칼리성 환경에서는 Sr이 Cs보다 흡착이 잘 되는 pH 의존성을 보였다. 수용액의 pH가 증가함에 따라 핵종의 흡착량이 증가하는데, 이는 캐올리나이트의 흡착자리인 실라놀과 알루미놀에 의한 제타전위가 pH에 의존함과 잘 일치한다.

• The Korean Journal of Physiology
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• v.22 no.2
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• pp.281-293
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• 1988

The effect of pH on the rate of PAH uptake was studied in rabbit renal basolateral membrane vesicles (BLMV) and brush border membrane vesicles (BBMV). In the absence of Na in incubation medium, a decrease in external $pH(pH_0)$ led to an increase in probenecid-sensitive PAH uptake by BLMV. In the presence of Na, the probenecid-sensitive PAH uptake was unaltered when the $pH_0$ decreased from 8.0 to 6.0 but further decrease in $pH_0$ to 5.5 increased significantly the uptake. The probenecid-sensitive PAH uptake was not affected by an alteration in pH per se in the absence of a pH gradient with or without the presence of Na. However, the presence of Na stimulated the probenecid-sensitive PAH uptake in all pH ranges tested over that measured in the absence of Na. A similar pattern of pH dependence on the PAH uptake was observed in BBMV but the presence of Na did not alter the probenecid-sensitive PAH uptake in the presence and absence of a pH gradient. Kinetic analysis for BLMV showed that Na or pH gradient increased Vmax of the probenecid-sensitive PAH uptake without a change in Km value. These results suggest that PAH is transported by $OH^-/PAH$ exchange process in the luminal membrane, but the pH dependence in the BLMV is not unequivocally consistent with an anion exchange process. The PAH transport is dependent on Na in BLMV but not in BBMV.

• Journal of the Korean Chemical Society
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• v.24 no.1
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• pp.86-89
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• 1980

• Korean Journal of Microbiology
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• v.37 no.4
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• pp.259-264
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• 2001

It has been well known that the expression of S. typhimurium cadBA operon requires at least two extracellular signals: low pH and high concentration of lysine. To better understand the nature of pH-dependent and lysine dependent signal transduction, mutants were isolated in JF2238(cadA-lacZ) by Tn10 insertion, spontaneous mutagenesis, and EMS treatment. Two mutants were isolated from JF2238, expressed as a cadA-lacZ operon fusion in various growth conditions, and analyzed to have mutations in cadC, a gene encoding a function necessary for transcriptional activation of cadBA. One isolate (cadC6) conferred pH-independent and lysine-independent cadBA expression and the other(cadC4) showed pH-independent and lysine-dependent cadBA expression. cadR::Tn10 and cadR4 mutants were expressed in the absence of exogenously added lysine. They were also resistant to thiosine and complemented by lysP clone from E. coli. Thus, in the absence of exogenous lysine, cadR is a negative regulator of cadBA expression. Cadaverine, the product of lysine decarboxylation, was shown to inhibit expression of cadA-lacZ fusion in cad $C^+$ cell.

• Nuclear Engineering and Technology
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• v.27 no.1
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• pp.25-32
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• 1995

Batch sorption experiments were conducted to investigate the sorption characteristics of $^{137}$ Cs, known for the primary target of safety assessment in low-level radwaste disposal, onto domestic rocks such as Granite and Tuff. A response surface analysis method was applied to quantify the effect of 3 independent variables (［Cs］, ［Vol/Wt］, ［pH］) on the sorption. Ac a result, initial Cs concentration appeared to be the most important variable within the range of the study. A significant effect of ［Vol/Wt］ on Kd was observed. The sorption of Cs was pH-insignificant. The sorption extent of nuclides onto tuff was more significant than that onto granite. The pH-insignificant sorption behavior of Cs was discussed in terms of the surface electrical properties and the solution chemistry. The sorption tendency of nuclides onto geomedia studied was interpreted by adopting the water structure modification theory.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.2
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• pp.135-143
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• 2004

An experimental study on the sorption of U(VI) onto a Korean granite was performed as a function of the geochemical parameters such as contact time, pH, ionic strength, and carbonate concentration using a batch procedure. The distribution coefficient,$K_d$, was about 1-200 mL/g depending on the experimental conditions. The sorption of U(VI) onto granite particles was greatly dependent upon the contact time, pH, and carbonate concentration, but insignificantly dependent on the ionic strength. It was noticed that the sorption of U(VI) onto granite particles was highly correlated with the uranium speciation in the solution, which was dependent on the pH and carbonate concentrations. It was deduced from the kinetic sorption experiment that a two-step first-order kinetic behavior could dominate the kinetic sorption of U(VI) onto granite particles. In the alkaline range of a pH above 7, U(VI) sorption was greatly decreased and this might be due to the formation of anionic U(VI)-carbonate aqueous complexes as predicted by the speciation calculations.

• Textile Coloration and Finishing
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• v.5 no.4
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• pp.92-100
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• 1993

1.8 기능성 색소 1.8.1 pH 지시약 수용액 중의 수소 이온 농도 [H$\^$+/]([]는 농도를 의미한다)를 간단하게 조사하기 위해 pH지시약을 이용하고 있다. 지시약은 일반적으로 유기약산이라든지 약염기로 용액의 pH에 의존하여 수소 이온(프로톤)이나 수산화물 이온이 부가된다든지 탈리 한다든지하여 색이 변화한다. [H$\^$+/]의 값은 작기 때문에 pH = -log[H$\^$+/]의 값으로 표시하며, pH 지시약에 담근 시험지나 pH meter로 측정한다. 예를 들면 페놀프탈레인은 무색의 약산으로 [HIn]으로 표시된다. 그 수용액은 조금만 전리하며, 그 공역 염기 [In$\^$-/]은 적색을 띈다.

• Applied Biological Chemistry
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• v.50 no.4
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• pp.257-261
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• 2007

Tolaasin, a peptide toxin produced by Pseudomonas tolaasii, causes a serious disease on the cultivated mushrooms, known as brown blotch disease. Hemolysis using red blood cells was designed to measure the cytotoxicity of tolaasin molecules. Since tolaasin has two amine groups near the C-terminus, its membrane binding will be dependent on the ionic states of the amine groups. When the tolaasin peptide was titrated, its titration curve indicated the presence of titratable amine(s) at pH ranges from 7.0 to 9.6. When the pH-dependence of tolaasin-induced hemolysis was measured at various pHs, hemolysis was more efficient at alkaline pHs. In order to measure the membrane binding activity of tolaasin at different pHs, RBCs were incubated with tolaasin molecules for short time periods and washed out with fresh buffer. Because of the tolaasin binding during the preincubation period, fast hemolyses were observed at pH 8 or higher. These results imply that non-charged or less positively charged states of tolaasin molecules easily bind to membrane and show high hemolytic activity.