• 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.

• 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

• 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.

• 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.

• 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.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.379-384
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• 2012

It is investigated that that the physical properties of Glutathione layer formed on gold surfaces may make an effect on the distribution of either gold particle adsorbed to the $TiO_2$ surface or vice versa with the adjustment of the electrostatic interactions. For the investigation, the atomic force microscope (AFM) was used to measure the surface forces between the surfaces as a function of the salt concentration and pH value. With the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the forces were quantitatively analyzed to acquire the surface potential and charge density of the surfaces for each salt concentration and each pH value. The surface potential and charge density dependence on the salt concentration was described with the law of mass action, and the pH dependence was explained with the ionizable groups on the surface. The salt concentration dependence of the surface properties, found from the measurement at pH 8 and 11, was consistent with the prediction from the law. It was found that the Glutathione layer had higher values for the surface charge densities and potentials than the titanium dioxide surfaces at pH 8 and 11, which may be attributed to the ionized-functional-groups of the Glutathione layer.

• 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.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.538-543
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• 2014

It is investigated that that the physical properties of Glutathione layer formed on gold surfaces may make an effect on the distribution of either gold particle adsorbed to the $ZrO_2$ surface or vice versa with the adjustment of the electrostatic interactions. For the investigation, the atomic force microscope (AFM) was used to measure the surface forces between the surfaces as a function of the salt concentration and pH value. The forces were quantitatively analyzed with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory to estimate the surface potential and charge density of the surfaces for each condition of salt concentration and pH value. The estimated-value dependence on the salt concentration was described with the law of mass action, and the pH dependence was explained with the ionizable groups on the surface. The salt concentration dependence of the surface properties, found from the measurement at pH 4 and 8, was consistent with the prediction from the law. It was found that the Glutathione layer had higher values for the surface charge densities and potentials than the zirconium dioxide surfaces at pH 4 and 8, which may be attributed to the ionized-functional-groups of the Glutathione layer.