• Proceedings of the Korean Magnetic Resonance Society Conference
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• 2002.08a
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• pp.38-39
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• 2002

• Molecules and Cells
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• v.28 no.5
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• pp.473-477
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• 2009

Previously, the 9-mer analog peptides, 9Pbw2 and 9Pbw4, were designed based on a defensin-like peptide, protaetiamycine isolated from Protaetia brevitarsis. In this study, antifungal effects of the analog peptides were investigated. The antifungal susceptibility testing exhibited that 9Pbw4 contained more potent antifungal activities than 9Pbw2. A PI influx assay confirmed the effects of the analog peptides and demonstrated that the peptides exerted their activity by a membrane-active mechanism, in an energy-independent manner. As the noteworthy potency of 9Pbw4, the mechanism(s) of 9Pbw4 were further investigated. The membrane studies, using rhodamine-labeled giant unilamellar vesicle (GUV) and fluorescein isothiocyanate (FITC)-dextran loaded liposome, suggested that the membrane-active mechanism of 9Pbw4 could have originated from the pore-forming action and the radii of pores was presumed to be anywhere from 1.8 nm to 3.3 nm. These results were confirmed by 3D-flow cytometric contour-plot analysis. The present study suggests a potential of 9Pbw4 as a novel antifungal peptide.

• Proceedings of the Korean Biophysical Society Conference
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• 2002.06b
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• pp.41-41
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• 2002

Tolaasin, a pore-forming 1.9 kDa peptide toxin released by Pseudomonas tolaasii, produces brown blotch disease on cultivated oyster mushrooms. To investigate the mechanism of tolaasin-induced cell disruption, we studied the effect of temperature on the hemolytic process. In the kinetic analyses, single exponential function was fitted to the data obtained from temperature-dependent velocity of hemolysis(1/t$\_$50/, implying that there is a major time-limiting factor on the temperature-dependent hemolysis.(omitted)

• Journal of Applied Biological Chemistry
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• v.59 no.3
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• pp.221-225
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• 2016

Tolaasin is a pore-forming peptide toxin produced by Pseudomonas tolaasii and causes a brown blotch disease by disrupting membrane structures of cultivated mushrooms. The mechanism and characteristics of tolaasin pore formation are not known in detail; however, tolaasin pores have been demonstrated in the artificial lipid bilayer. Since the tolaasin pore appeared less frequently and unstable in lipid bilayer, a mismatch between the length of tolaasin pore and the thickness of lipid membrane had been suggested. Therefore, tolaasin-induced hemolyses were measured by the additions of phospholipids composed of various fatty acids with different carbon numbers. When phosphatidylethanolamines made with two decanoic acids (C10:0, 1,2-didecanoyl-sn-glycero-3-phosphoethanolamine; DDPE), myristic acids (C14:0, 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine), and stearic acids (C18:0, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine) were added to the buffer containing RBCs and tolaasin peptides, DDPE facilitated the tolaasin-induced hemolysis while the other two phospholipids showed no effects. At various concentrations of DDPE, the tolaasin-induced hemolysis was stimulated as a dose-dependent manner. The phospholipids composed of mediumchain fatty acids stabilize the tolaasin pore probably by binding between the pore structure and membrane phospholipids and making the membrane thickness thinner around the pore. These results showed that tolaasin molecules make more stable pores in the membrane made with phospholipids composed of medium length fatty acids, suggesting that the length of tolaasin pore is a little shorter than the thickness of RBC membrane.

• Journal of Environmental Science International
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• v.27 no.2
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• pp.109-122
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• 2018

This study was conducted to investigate the removal characteristics of heavy metals and sulfate ion from acid mine drainage by porous zeolite-slag ceramics (ZS ceramics) that was prepared by adding wood flour as pore-foaming agent while calcining the mixtures of natural zeolite and converter slag. The batch test showed that the removal efficiency of heavy metals by pellet-type porous ZS ceramics increased as the particle size of wood flour was decreased and as the weight mixing ratio of wood flour to ZS ceramics was increased. The optimal particle size and weight mixing ratio of wood flour were measured to be $75{\mu}m$ and 7~10%, respectively. The removal test with the porous ZS ceramics prepared in these optimal condition showed very high removal efficiencies: more than 98.4% for all heavy metals and 73.9% for sulfate ion. Relative to nonporous ZS ceramics, the increment of removal efficiency of heavy metals by porous ZS ceramics with $75{\mu}m$ and 10% wood flour was 5.8%, 60.5%, 36.9%, 87.7%, 10.3%, and 57.4% for Al, Cd, Cu, Mn, Pb, and Zn, respectively. The mechanism analysis of removal by the porous ZS ceramics suggested that the heavy metals and sulfate ion from acid mine drainage are eliminated by multiple reactions such as adsorption and/or ion exchange as well as precipitation and/or co-precipitation.

• Journal of Microbiology and Biotechnology
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• v.20 no.8
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• pp.1185-1188
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• 2010

Previously, papiliocin was isolated from the swallowtail butterfly Papilio xuthus and its antimicrobial activity was suggested. In this study, the antifungal mechanism of papiliocin against Candida albicans was investigated. Confocal laser scanning microscopy (CLSM) and 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence analysis indicated that papiliocin disturbed the fungal plasma membrane. Moreover, the assessment of the release of FITC-dextran (FD) from liposomes further demonstrated that the antifungal mechanism of papiliocin could have originated from the pore-forming action and that the radius of the pores was presumed to be anywhere from 2.3 to 3.3 nm.

• Journal of the Korean Ceramic Society
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• v.30 no.3
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• pp.189-198
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• 1993

A new pressurized sol-gel coating technique forming membrane layers inside pores of the porous support by the simple operation has been developed. Crack-free and reproducible nanoparticulate silica membranes supported on the porous $\alpha$-alumina tube are synthesized by pressurized coating at 600kPa for 2hr. The pore radius and N2 gas permiability at the room temperature of silica membrane layers are 8$\AA$ and 7.0$\times$10-7mol/$m^2$.s.Pa, respectively. The mechanism of N2 gas transfer through synthesized membrane layers is the perfect Knudeen flow, and the thermal stability of the silica composite membranes is excellent upto 40$0^{\circ}C$.

• 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 Microbiology and Biotechnology
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• v.25 no.6
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• pp.918-929
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• 2015

Microbial enhanced oil recovery (MEOR) is being used more widely, and the biological contributions involved in MEOR need to be identified and quantified for the improvement of field applications. Owing to the excellent interfacial activity and the wide distribution of producing strains in oil reservoirs, lipopeptides have proved to be an essential part of the complex mechanisms in MEOR. In this study, crude lipopeptides were produced by a strain isolated from an indigenous community in an oil reservoir. It was found that crude lipopeptides can effectively reduce the IFT (interfacial tension) to 10^-1~10^-2 mN/m under high salinity without forming stable emulsions, and the wettability of natural sandstone can be enhanced (Amott index, from 0.36 to 0.48). The results of core flooding experiments indicate that an additional 5.2% of original oil in place can be recovered with a 9.5% reduction of injection pressure. After the shut-in period, the wettability of the core, the reduction of injection pressure, and the oil recovery can be improved to 0.63, 16.2% and 9.6%, respectively. In the microscopic flooding experiments, the crude oil in membrane, cluster, and throat states contribute nearly 90% in total of the additional oil recovery, and the recovery of membranestate oil was significantly enhanced by 93.3% after shut in. Based on the results in macro and pore scale, the IFT reduction and the wettability alteration are considered primary contributors to oil recovery, while the latter was more dominant after one shut-in period.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.5
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• pp.210-216
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• 2007

Porous nickel membrane far high precision gas filter was prepared by in-situ reduced/sintered process of NiO with an addition of polymer(PMMA; polymethyl methacrylate). It showed that the porosity of Ni membrane was approximately 52%. It is similar to metal membrane which prepared using metal fiber as raw materials. The average pore diameter and porosity of Ni membrane increased as content of added polymer and decreased as elevating reduced/sintered temperature from $800^{\circ}C$ to $1000^{\circ}C$. Increase of porosity at $800^{\circ}C$ was associated with surface diffusion mechanism that leads to initial sintering, while decrease of porosity at $1000^{\circ}C$ was associated with lattice diffusion and grain boundary diffusion.