• Journal of Korean Society of Environmental Engineers
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• v.28 no.10
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• pp.1046-1054
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• 2006

The raw water DOC contained 39.3% of hydrophilics, 42.9% of hydriophobic, and 17.8% of transphilic. The hydrophobic fraction in this raw water was mostly fulvic acid. Fulvic acid comprised of 62% and the rest was humic acid(38%). There was more carboxylic acid functional group(64%) than phenolic group(36%). HPI-N and HPI-C comprised of 17% and 22% in the hydrophilic portion, respectively. The fouling mechanisms on the membrane surface and into its porous structure were analyzed in terms of several kinetic models. In order to analyze the fouling kinetics, the various kinetic models described in this paper were used to fit the experimental results. The kinetic models and kinetic constants obtained for each operation condition. The permeate flux was rapidly declined by simultaneous pore blocking and cake formation. Also, the permeate flux declined with decreasing internal pore size resulted from organic deposition into the membrane pore. The results of the membrane fouling test using UF membrane according to NOM fractions. HPI-N caused more fouling than HPI-C. Humic acid caused more fouling than fulvic acid probably due to higher adsorption capacity. Since humic acid has higher adsorption capacity than fulvic acid, it would be more adsorbed onto the membrane pores.

• Journal of Applied Biological Chemistry
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• v.52 no.1
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• pp.28-32
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• 2009

The bacterial toxin, tolaasin, causes brown blotch disease on the cultivated mushrooms by collapsing fungal and fruiting body structure of mushroom. Cytotoxicity of tolaasin was evaluated by measuring hemolytic activity because tolaasins form membrane pores on the red blood cells and destroy cell structure. While we investigated the inhibitions of hemolytic activity of tolaasin by $Zn^{2+}$ and $Cd^{2+}$, we found that $Ni^{2+}$ is another antagonist to block the toxicity of tolaasin. $Ni^{2+}$ inhibited the tolaasin-induced hemolysis in a dose-dependent manner and its Ki value was $\sim10$ mM, implying that the inhibitory effect of $Ni^{2+}$ is stronger than that of $Cd^{2+}$. The hemolytic activity was completely inhibited by $Ni^{2+}$ at the concentration higher than 50 mM. The effect of $Ni^{2+}$ was reversible since it was removed by the addition of EDTA. When the tolaasin-induced hemolysis was suppressed by the addition of 20 mM $Ni^{2+}$, the subsequent addition of EDIA immediately initiated the hemolysis. Although the mechanism of $Ni^{2+}$ -induced inhibition on tolaasin toxicity is not known, $Ni^{2+}$ could inhibit any of fallowing processes of tolaasin action, membrane binding, molecular multimerization, pore formation, and massive ion transport through the membrane pore. Our results indicate that $Ni^{2+}$ inhibits the pore activity of tolaasin, the last step of the toxic process.

• Korean Chemical Engineering Research
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• v.43 no.2
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• pp.236-242
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• 2005

Membrane fouling by protein mixtures during microfiltration has been investigated for binary mixtures of bovine serum albumin (BSA), casein, lysozyme, pepsin, and ovalbumin. Filtration experiments were carried out using $0.2{\mu}m$ polycarbonate track-etched (PCTE) membrane in a stirred cell under constant transmembrane pressure (14 kPa) and concentration of hydrogen ion (pH=11) to study the effect of mixture composition on filtrate flux decline. Flux decline data were analyzed using a pore blockage-cake formation model developed recently. It was found that the model is in a good agreement with the experimental data. Fouling parameters such as the rate of pore blockage(${\alpha}$), the initial resistance of the protein deposit ($R_{po}$) and the increasing rate of the protein layer resistance(${\beta}$) were used to evaluate the rate of filtrate flow by membrane fouling in the binary mixture system. Generally, the trend of ${\alpha}$ is comparable with that of filtrate flux decline. It was also found that fast flux decreasing was observed over the binary mixture containing casein. The result is due to high value of the initial resistance of the protein deposit ($R_{po}$) over casein.

• Applied Biological Chemistry
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• v.49 no.4
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• pp.281-286
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• 2006

Tolaasin, a pore-forming toxin, is a 1,985 Da peptide produced by Pseudomonas tolaasii and causes a brown blotch disease on cultivated mushrooms. Tolaasin forms pores on the plasma membrane of various cells including fungi, bacteria, plant as well as erythrocytes, and destroys cell structure. $Zn^{+2}$ has been known to block the tolaasin activity by an unknown mechanism. Thus, we investigated the inhibitory effects of $Zn^{+2}$ on the tolaasin-induced hemolysis to understand the molecular mechanism of tolaasin-induced pore formation. $Zn^{+2}$ and $Cd^{+2}$ inhibited the tolaasin-induced hemolysis in a dose-dependent manner and their Ki values were 170 ${\mu}M$ and 20 mM, respectively. The effect of $Zn^{+2}$ was reversible since the subsequent addition of EDTA chelates $Zn^{+2}$ and removes the inhibitory effect of $Zn^{+2}$. When an osmotic protectant, PEG 2000, was added, the tolaasin-induced hemolysis was not observed. After the removal of osmotic protectant by centrifugation, resuspended erythrocytes with fresh medium were immediately hemolyzed, while the addition of $Zn^{+2}$ prevented from hemolysis, implying that tolaasin-induced pores on the membrane were already formed in the medium containing osmotic protectant. These results suggest that $Zn^{+2}$ inhibits the activity of tolaasin pores and it has minor effects on the membrane binding of tolaasin and the formation of pore.

• Journal of the Korean Ceramic Society
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• v.29 no.11
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• pp.905-911
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• 1992

Model equations for the gas permeation through a ceramic composite membrane were derived for examining the existence of crack, the reproducibility, and the microstructural properties of composite membranes. From the results of analyzing the nitrogen permeability data through alumina-tube supported TiO2 and SiO2 composite membranes, the extent of cracking, and the formation and structure of membrane top-layers were modelled. It was proved that the crack-free and reproducible composite membranes could be easily prepared only by the pore-filled coating within pores of the support in the sol-gel coating process.

• Membrane and Water Treatment
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• v.7 no.4
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• pp.327-339
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• 2016

Nanofiltration is useful to concentrate propolis extract. During the selection of membrane, both compound rejection and permeate flux are important indicators of process economy. Brazilian green propolis extract was studied to evaluate the separation performance of Startmen 122 and NF270 membranes. Compared to Starmen 122, NF270 membrane showed better rejection of bioactive compounds. The flux decline patterns were further studied using Hermia's model. Cake formation is the major fouling mechanism on the hydrophobic surface of Starmen 122. While the fouling mechanism for NF270 is pore blocking. The fouled membranes were further characterized using SEM and FT-IR to confirm on the predicted fouling mechanisms.

• Bulletin of the Korean Chemical Society
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• v.16 no.12
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• pp.1167-1172
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• 1995

A coverage of about 1 μm-sized pores of a membrane filter by four monolayers of maleic acids copolymers and poly(allylamine) (PAA) was attained by Langmuir-Blodgett (LB) technique through a covalent cross-linking followed a polyion complexation at the air-water interface. The copolymers were prepared to have side chains of hydrocarbon tail, carboxyl, and/or oligoether in the repeat unit. The surface pressure-area isotherms showed that the monolayers on an aqueous PAA have more expanded area than on pure water. The monolayers were transferable on a calcium fluoride substrate and a fluorocarbon membrane filter as Y deposition type, and the resulting LB films were characterized by FT-IR spectroscopy and scanning electron microscopy. A polymer network produced through interchain amide formation was confirmed in as-deposited films. The films were heat-treated in order to complete the cross-linking. SEM observation of the heat-treated film on a porous membrane filter showed that the four layer film was sufficiently stable to cover the filter pore of about 1 μm. Immersion of the film in water or in chloroform did not cause any change in its appearance on SEM and in FT-IR spectra.

• BMB Reports
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• v.32 no.3
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• pp.273-278
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• 1999

Cytolysin produced by Vibrio vulnificus has been known to be lethal to mice by increasing vascular permeability and neutrophil sequestration in the lung. In the present study, a cytotoxic mechanism of V. vulnificus cytolysin on the neutrophil was investigated. Cytolysin rapidly bound to neutrophils and induced cell death, as determined by the trypan blue exclusion test. V. vulnificus cytolysin caused the depletion of cellular ATP without the release of ATP or lactate dehydrogenase. Formation of transmembrane pores was evidenced by the rapid efflux of potassium and 2-deoxy-D-[$^3H$]glucose from cytolysin-treated neutrophils. It was further confirmed by the rapid flow of monovalent ions in the patch clamp of cytolysin-treated neutrophil membrane. The pore formation was accompanied by the oligomerization of cytolysin monomers on the neutrophil membrane as demonstrated by immunoblot, which exhibited a 210 kDa band corresponding to a tetramer of the native cytolysin of $M_r$ 51,000. These findings indicate that V. vulnificus cytolysin rapidly binds to the neutrophil membrane and oligomerizes to form small transmembrane pores, which induce the efflux of potassium and the depletion of cellular ATP leading to cell death without cytolysis.

• Journal of Periodontal and Implant Science
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• v.34 no.3
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• pp.683-698
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• 2004

One of the bone substitutes now in routine use, deproteinized bovine bone mineral(DBBM), is regarded as resorbable and osteoconductive, but some studies refute this. The present study was performed to evaluate the effects of DBBM on guided bone regeneration using titanium membrane on the calvaria of rabbit. At 2 weeks, 4 weeks, 8 weeks, and 12 weeks after surgery, the animal was scrificed. Non-decalcified specimens were produced for histologic analysis. The results of this study were as follows : 1. Titanium membrane was biocompatible and capable of space-maintaining, but there was ingrowth of soft tissue through the pore of titanium membrane. 2. There was no resorption or reduction of DBBM with time. 3. Some of the DBBM particles were combined with newly formed bone. But, apart from host bone, a great part of the particles were surrounded by connective tissue. 4. The bone formation was slight vertically and restricted to superficial area of host bone. Whithin the above results, DBBM dose not appear to contribute to bone formation. DBBM may disturb the migration and proliferation of mesenchymal cell derived from host bone and increase the growth of connective tissue. Therefore, careful caution is needed on selection of bone graft material and surgical protocol at guided bone regeneration for implant placement.

• Membrane and Water Treatment
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• v.7 no.6
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• pp.539-553
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• 2016

As a novel hydrophobic monomer, polytetrahydrofuran diacrylate (PTMGDA) was synthesized by the esterification reaction between polyethylene tetrahydrofuran (PTMG) and acryloyl chloride (AC). In situ free radical polymerization reaction method was utilized to fabricate poly (vinylidene fluoride) (PVDF)-PTMGDA-poly(ethylene oxide) dimethacrylate (PEGMA) ulrafiltration (UF) membranes. The performances of PVDF-PTMGDA-PEGMA UF membranes in terms of morphologies, mechanical properties, separation properties and hydrophilicities were investigated. The introduction of the PTMGDA-PEGMA dopants not only increased the membranes' pure water flux, but also improved their mechanical properties and the dynamic contact angles. The addition of the PTMGDA/PEGMA dopants led to the formation of the finger-like structure in the membrane bulk. With the increase concentration of PTMGDA/PEGMA dopants, the porosity and the mean effective pore size increased. Those performances were coincide with the physicochemical properties of the casting solutions.