• BMB Reports
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• v.34 no.5
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• pp.402-407
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• 2001

Based on the currently proposed toxicity model for the different Bacillus thuringiensis Cry $\delta$-endotoxins, their pore-forming activity involves the insertion of the ${\alpha}4-{\alpha}5$ helical hairpin into the membrane of the target midgut epithelial cell. In this study, a number of polar or charged residues in helix 4 within domain I of the 65-kDa dipteranactive Cry11A toxin, Lys-123, Tyr-125, Asn-128, Ser-130, Gln-135, Arg-136, Gln-139 and Glu-141, were initially substituted with alanine by using PCR-based directed mutagenesis. All mutant toxins were expressed as cytoplasmic inclusions in Escherichia coli upon induction with IPTG. Similar to the wild-type protoxin inclusion, the solubility of each mutant inclusion in the carbonate buffer, pH 9.0, was relatively low When E. coli cells, expressing each of the mutant proteins, were tested for toxicity against Aedes aegypti mosquito-larvae, toxicity was completely abolished for the alanine substitution of arginine at position 136. However, mutations at the other positions still retained a high level of larvicidal activity Interestingly, further analysis of this critical arginine residue by specific mutagenesis showed that conversions of arginine-136 to aspartate, glutamine, or even to the most conserved residue lysine, also abolished the wild-type activity The results of this study revealed an important determinant in toxin function for the positively charged side chain of arginine-136 in helix 4 of the Cry11A toxin.

• Mycobiology
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• v.47 no.4
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• pp.368-377
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• 2019

The genus Macrolepiota (Agaricales, Basidiomycota) is easy to recognize at the genus level because of big, fleshy basidiocarps with squamules covering the pileus; a single or double annulus; and big, thick-walled basidiospores with a germ pore. However, morphological identification is often unreliable in Macrolepiota due to similar morphological features among species. Due to the uncertainty of previous morphological identification in the genus Macrolepiota, it is necessary to re-examine Korean Macrolepiota using molecular data. We reexamined 34 Macrolepiota specimens collected from 2012 to 2018 in Korea using a reverse taxonomic approach, whereby species identification was first done based on the internal transcribed spacer (ITS) region analysis, followed by morphological confirmation. We identified the presence of four species: M. detersa, M. mastoidea, M. procera, and M. umbonata sp. nov. Two species (M. detersa and M. mastoidea) were previously unrecorded from Korea and M. umbonata is a new species. Detailed descriptions of all four species and taxonomic key are provided in this study. Macrolepiota procera and M. umbonata are distributed through the country, but M. detersa and M. mastoidea are distributed only in limited areas. According to our results, the combination of ITS locus and morphology proved to be a robust approach to evaluate the taxonomic status of Macrolepiota species in Korea. Additional surveys are needed to verify the species diversity and clarify their geographic distribution.

• Membrane Journal
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• v.21 no.3
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• pp.236-246
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• 2011

In this study, we used prepared a cylindrical module consisting 100 hollow fibers of commercialized (hydrophobic) polyethylene membrane of $0.4{\mu}m$ pore size and systematically studied performance of direct contact membrane distillation (DCMD) and sweep gas membrane distillation (SGMD) in terms of variation of permeate flux and salt rejection with respect to temperature drop across the membrane, salt concentrations in feed, and flow rates of cooling water and sweep gas. SGMD was regarded as DCMD with a sweep gas layer between permeate-side membrane surface and cooling water. Sweep gas flow decreases the permeate flux from that of DCMD by providing an additional gas-layer resistance. We compared DCMD and SGMD performance by using mass balance with a fitting parameter (${\omega}$), indicating fraction of permeate flow rate.

• Membrane Journal
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• v.29 no.6
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• pp.308-313
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• 2019

In this study, the Fe₃O₄/porous carbon composite was synthesized by hydrothermal method for removal of Cu²⁺ ions and the characteristic of Cu²⁺ ions removal was performed. The Fe₃O₄/porous carbon composite was investigated via using SEM, XRD for its morphology and structure. BET analysis was conducted to conform a specific area and pore size distribution of the composite. For the investigation of the performance for removal of Cu²⁺ ions in the solution, UV-vis spectrometer was used. It suggests that a synergetic effect between magnetic Fe₃O₄ and porous carbon shows an improvement for removal of Cu²⁺ ions.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.275-280
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• 2009

The direct incorporation of vanadium into the three-dimensional(3-D) cubic Ia3d mesostructure designated as V-KIT-6 was carried out hydrothermally using a Pluronic P123 and n-butanol as the structure-directing mixture, tetraethylorthosilicate(TEOS) as the silica source and $NH_4VO_3$ as the vanadium source. The obtained V-KIT-6 showed a very high specific surface area ${\sim}1,000m^2/g$ with tunable pore diameters in narrow distribution of sizes ~6.0 nm. The coordination and nature of V sites in V-KIT-6 are characterized by $^{51}V$-spin-echo NMR analysis. The calcined V-KIT-6 materials showed excellent catalytic activity in the direct oxidation of styrene using tert-butyl hydroperoxide(TBHP) as an oxidant.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.2
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• pp.89-96
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• 2012

Based on the hydroelastic theory and the matched eigenfunction expansion method(MEEM), the dynamic behavior of the porous flexible net sheet and wave forces have been investigated in monochromatic waves. The net sheet is installed vertically with the submergence depth. Top end of a net sheet is fixed and its lower end is attached by a clump weight. It is assumed that the initial tension is sufficiently large so that the effects of dynamictension variation can be neglected. The boundary condition on the porous flexible net sheet is derived based on Darcy's fine-pore model and body boundary condition. The developed analytic model can be extended to the impermeable/permeable vertical plate and the impermeable flexible membrane. The analytical model was used to study the influence of design parameters(wave characteristics, porosity, submergence depth, initial tension) on the response characteristics and wave load of the net sheet.

• Journal of Microbiology and Biotechnology
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• v.22 no.4
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• pp.470-478
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• 2012

Recent genome comparisons of E. coli B and K-12 strains have indicated that the makeup of the cell envelopes in these two strains is quite different. Therefore, we analyzed and compared the envelope proteomes of E. coli BL21(DE3) and MG1655. A total of 165 protein spots, including 62 nonredundant proteins, were unambiguously identified by two-dimensional gel electrophoresis and mass spectrometry. Of these, 43 proteins were conserved between the two strains, whereas 4 and 16 strain-specific proteins were identified only in E. coli BL21(DE3) and MG1655, respectively. Additionally, 24 proteins showed more than 2-fold differences in intensities between the B and K-12 strains. The reference envelope proteome maps showed that E. coli envelope mainly contained channel proteins and lipoproteins. Interesting proteomic observations between the two strains were as follows: (i) B produced more OmpF porin with a larger pore size than K-12, indicating an increase in the membrane permeability; (ii) B produced higher amounts of lipoproteins, which facilitates the assembly of outer membrane ${\beta}$-barrel proteins; and (iii) motility- (FliC) and chemotaxis-related proteins (CheA and CheW) were detected only in K-12, which showed that E. coli B is restricted with regard to migration under unfavorable conditions. These differences may influence the permeability and integrity of the cell envelope, showing that E. coli B may be more susceptible than K-12 to certain stress conditions. Thus, these findings suggest that E. coli K-12 and its derivatives will be more favorable strains in certain biotechnological applications, such as cell surface display or membrane engineering studies.

• Environmental Engineering Research
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• v.25 no.4
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• pp.536-544
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• 2020

To address organic dye wastewater, economic and effective adsorbents are required. Here, magnetic biochar from alkali-activated rice straw (AMBC) was successfully synthesized using one-step magnetization and carbonization method. The alkaline activation caused the large specific surface area, high pore volume and abundant oxygen-containing groups of the AMBC, and the magnetization gave the AMBC a certain degree of electropositivity and fast equilibrium characteristics. These characteristics collectively contributed to a relative high adsorption capacity of 53.66 mg g^-1 for this adsorbent towards rhodamine B (RhB). In brief, RhB can spontaneously adsorb onto the heterogeneous surface of the AMBC and reach the equilibrium in 60 min. Although the initial pH, ionic strength and other substances of the solution affected the adsorption performance of the AMBC, it could be easily regenerated and reused with considerable adsorption content. Based on the results, H-bonds, π-π stacking and electrostatic interactions were speculated as the primary mechanisms for RhB adsorption onto the AMBC, which was also demonstrated by the FTIR analysis. With the advantageous features of low cost, easy separation, considerable adsorption capacity and favorable stability and reusability, the AMBC would be a potential adsorbent for removing organic dyes from wastewater.

• Analytical Science and Technology
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• v.8 no.2
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• pp.205-213
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• 1995

Counter-diffusion of coronene desorbed from alumina with addition of tetra-phenylporphine was studied by spectrophotometry. The counter-diffusion processes of adsorbing and desorbing materials in liquid phase were simulated by counter-diffusion model based on Fritz's binary component isotherm under an assumption of equimass diffusion. The counter-diffusivities of desorbed coronene with addition of tetra-phenylporphine were as ${\sim}10^{-15}m^2/sec$ and that of adsorbed tetra-phenylporphine as ${\sim}10^{-11}m^2/sec$. The counter-diffusivity of coronene determined from desorption process was smaller by ${\sim}10^5$ times than the diffusivity determined from adsorption process of a single species. The reduction of the determined counter-diffusivity of coronene in desorption process was explained by the cross of diffusion fluxes and build-up of high gradient of coronene in pore.

• Journal of environmental and Sanitary engineering
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• v.17 no.3
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• pp.99-109
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• 2002

Charcoal $tube/CS_2$ method are more popularly used than any other in the measurement of the working environment for the exposure evaluation of organic solvent, but it is some weak points that the lower accuracy can be obtained on the polar materials and within the range of the low concentration. Thus solvent desorption method has been developed to make accuracy higher and to overcome some weak points. However, because of high price of adsorption tube for thermal desorption and the short of study on its application to the working environment, it is not popularly used in the domestic industrial hygiene fields. This dissertation aims to develop thermal desorption and adsorption tubes for measuring organic solvents in the working environment, by comparing and analyzing breakthrough condition and adsorption capacity with ACF. Specific surface area of ACF used in this study is wider than the one of AC and micropore of ACF related with adsorption has been developed, and adsorption velocity and adsorption amount are very excellent by linking a pore of surface and an inside well into micropore. 1. Result of analysis on physical characteristics of adsorbent, the specific surface area of ACF was 1.3 times higher than that of AC. Distribution ratio of micropore related to adsorption was 94% on ACF and AC. Result of SEM, micropore of the AC is opened to the surface. In contrast, ACF shows that extremely fast adsorption speed. Because of micropore are exposed on the surface and penetrate through each other. 2. Breakthrough characteristics of adsorbents was not different from slop of breakthrough curve. The effluent concentration reaches 10% of initial concentration($C_{out}/C_{in}=0.1$, break point) of ACF was 30~316min longer than that of AC. Therefore, the adsorption capacities of ACF was 1.1~4.6 times higher than that of AC. ACF can be used as a proper adsorbent for measurement of organic solvent.