• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.167-172
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• 2011

In this work, the effect of surface treatment on mesoporous carbons (MCs) supports was investigated by analyzing surface functional groups. MCs were prepared by a conventional templating method using mesoporous silica (SBA-15) for using catalyst supports in direct methanol fuel cells (DMFCs). The MCs were treated with different phosphoric acid ($H_3PO_4$) concentrations i.e., 0, 1, 3, 4, and 5 M at 343 K for 6 h. And then Pt-Ru was deposited onto surface treated MCs (H-MCs) by chemical reduction method. The characteristics of Pt-Ru catalysts deposited onto H-MCs were determined by specific surface area and pore size analyzer, X-ray diffraction, X-ray photoelectron, transmission electron microscopy, and inductive coupled plasma-mass spectrometer. The electrochemical properties of Pt-Ru/H-MCs catalysts were also analyzed by cyclic voltammetry experiments. From the results of surface analysis, an oxygen functional group was introduced to the surface of carbon supports. From the results, the H4M-MCs carbon supports surface treated with 4 M $H_3PO_4$ led to uniform dispersion of Pt-Ru onto H4M-MCs, resulting in enhancing the electro-catalytic activity of Pt-Ru catalysts.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.224-224
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• 2012

For decades, carbon fiber has expanded their application fields from reinforced composites to energy storage and transfer technologies such as electrodes for super-capacitors and lithium ion batteries and gas diffusion layers for proton exchange membrane fuel cell. Especially in fuel cell, water repellency of gas diffusion layer has become very important property for preventing flooding which is induced by condensed water could damage the fuel cell performance. In this work, we fabricated superhydrophobic network of carbon fiber with high aspect ratio hair-like nanostructure by preferential oxygen plasma etching. Superhydrophobic carbon fiber surfaces were achieved by hydrophobic material coating with a siloxane-based hydrocarbon film, which increased the water contact angle from $147^{\circ}$ to $163^{\circ}$ and decreased the contact angle hysteresis from $71^{\circ}$ to below $5^{\circ}$, sufficient to cause droplet roll-off from the surface in millimeter scale water droplet deposition test. Also, we have explored that the condensation behavior (nucleation and growth) of water droplet on the superhydrophobic carbon fiber were significantly retarded due to the high-aspect-ratio nanostructures under super-saturated vapor conditions. It is implied that superhydrophobic carbon fiber can provide a passage for vapor or gas flow in wet environments such as a gas diffusion layer requiring the effective water removal in the operation of proton exchange membrane fuel cell. Moreover, such nanostructuring of carbon-based materials can be extended to carbon fiber, carbon black or carbon films for applications as a cathode in lithium batteries or carbon fiber composites.

• Journal of the Korean Vacuum Society
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• v.14 no.3
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• pp.165-170
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• 2005

There is an increasing interest in developing novel coating to improve the blood compatibility of medical implants. Diamond-like carbon(DLC) and titanium nitride(TiN) films have been proposed as potential biomedical coatings due to their chemical k physical properties and moderate biocompatibility. To study the correlation between blood compatibility and physical properties of the films, the fibrinogen adsorption on the surface as well as morphology & wettability were investigated. The quantity of fibrinogen adsorption are Tower for TiN than DLC, which correlates with a higher hydrophilicity of TiN film. To reduce the quantity of fibrinogen adsorption on the film, plasma treatment and furnace annealing were performed, respectively. With the use of oxygen plasma and furnace annealing, the amount of fibrinogen adsorption on TiN film was remarkably reduced, while there was no decrease of the quantity with DLC.

• Molecules and Cells
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• v.44 no.10
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• pp.758-769
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• 2021

Calcium homeostasis modulator 1 (CALHM1) is a membrane protein with four transmembrane helices that form an octameric ion channel with voltage-dependent activation. There are four conserved cysteine (Cys) residues in the extracellular domain that form two intramolecular disulfide bonds. We investigated the roles of C42-C127 and C44-C161 in human CALHM1 channel biogenesis and the ionic current (I_CALHM1). Replacing Cys with Ser or Ala abolished the membrane trafficking as well as I_CALHM1. Immunoblotting analysis revealed dithiothreitol-sensitive multimeric CALHM1, which was markedly reduced in C44S and C161S, but preserved in C42S and C127S. The mixed expression of C42S and wild-type did not show a dominant-negative effect. While the heteromeric assembly of CALHM1 and CALHM3 formed active ion channels, the co-expression of C42S and CALHM3 did not produce functional channels. Despite the critical structural role of the extracellular cysteine residues, a treatment with the membrane-impermeable reducing agent tris(2-carboxyethyl) phosphine (TCEP, 2 mM) did not affect I_CALHM1 for up to 30 min. Interestingly, incubation with TCEP (2 mM) for 2-6 h reduced both I_CALHM1 and the surface expression of CALHM1 in a time-dependent manner. We propose that the intramolecular disulfide bonds are essential for folding, oligomerization, trafficking and maintenance of CALHM1 in the plasma membrane, but dispensable for the voltage-dependent activation once expressed on the plasma membrane.

• Food Engineering Progress
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• v.14 no.3
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• pp.202-207
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• 2010

Low-pressure plasmas (LPPs) were generated with different gases such as air, oxygen and nitrogen, and their inactivation effects against Escherichia coli were compared in order to evaluate the potential as a non-thermal microbial disinfection technology. Homogeneous plasmas were generated under low pressure below 1 Torr at gas flow rate of 350 mL/min regardless the types of gases. Temperature increases by LPPs were not detrimental showing less than ${10^{\circ}C}$ and ${25^{\circ}C}$ increases after 5 and 10 min treatments, respectively. The smallest temperature increase was observed with air LPP, and followed by oxygen and nitrogen LPPs. More than 5 log reduction in E. coli was achieved by 5 min LPP treatment but the destruction effect was retarded afterward. The LPP inactivation was represented by a iphasic first order reaction kinetics. The highest inactivation rate constant was achieved in air LPP and followed by oxygen and nitrogen LPPs. The small D-values of the LPP also supported its potentialities as a non-thermal food surface disinfection technology in addition to the substantial microbial reduction of more than 5 logs.

• Journal of Life Science
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• v.23 no.9
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• pp.1163-1169
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• 2013

Insulin induces glucose transporter 4 (GLUT4) translocation to the muscle cell surface. As fagopyritol has insulin-like effects, the effects of fagopyritol on GLUT4 translocation and filamentous (F) actin remodeling in L6-GLUT4myc skeletal muscle cells were investigated. Fagopyritol significantly increased plasma membrane GLUT4 levels compared with the basal control in L6-GLUT4myc myoblast cells. Phosphatidylinositol (PI) 3-kinase inhibitor (LY294002) treatment prevented GLUT4 translocation to the plasma membrane in the myoblasts. Fagopyritol treatment apparently stimulates F-actin remodeling in myoblasts. In addition, fagopyritol treatment induced GLUT4 translocation and F-actin remodeling in myotubes. Taken together, these results suggest that fagopyritol promotes GLUT4 translocation and F-actin remodeling by activating the PI 3-kinase-dependent signaling pathway.

• Translational and Clinical Pharmacology
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• v.26 no.4
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• pp.160-165
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• 2018

Indobufen ($Ibustrin^{(R)}$), a reversible inhibitor of platelet aggregation, exists in two enantiomeric forms in 1:1 ratio. Here, we characterized the anti-platelet effect of S- and R-indobufen using response surface modeling using $NONMEM^{(R)}$ and predicted the therapeutic doses exerting the maximal efficacy of each enantioselective S- and R-indobufen formulation. S- and R-indobufen were added individually or together to 24 plasma samples from drug-naïve healthy subjects, generating 892 samples containing randomly selected concentrations of the drugs of 0-128 mg/L. Collagen-induced platelet aggregation in platelet-rich plasma was determined using a Chrono-log Lumi-Aggregometer. Inhibitory sigmoid $I_{max}$ model adequately described the anti-platelet effect. The S-form was more potent, whereas the R-form showed less inter-individual variation. No significant interaction was observed between the two enantiomers. The anti-platelet effect of multiple treatments with 200 mg indobufen twice daily doses was predicted in the simulation study, and the effect of S- or R-indobufen alone at various doses was predicted to define optimal dosing regimen for each enantiomer. Simulation study predicted that 200 mg twice daily administration of S-indobufen alone will produce more treatment effect than S-and R-mixture formulation. S-indobufen produced treatment effect at lower concentration than R-indobufen. However, inter-individual variation of the pharmacodynamic response was smaller in R-indobufen. The present study suggests the optimal doses of R-and S-enantioselective indobufen formulations in terms of treatment efficacy for patients with thromboembolic problems. The proposed methodology in this study can be applied to the develop novel enantio-selective drugs more efficiently.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.441-441
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• 2011

$TiO_2$ nanoparticles were grown on carbon fiber by atomic later deposition (ALD) with TTIP $(Ti(OCH(CH_3)_2)_4$ and $H_2O$ precusors. After sampe surfaces were treated by electron beam (1 MeV, 5 KGy), an improvement in the photocatalytic reacitivity of $TiO_2$ nanoparticles on carbon fiber was observed. An increase in the population of hydroxyl group on $TiO_2$ particles and the oxidation of carbon fiber were found upon e-beam exposure, whereas there was no noticeable changes of their morphology. It implies that those changes in O and C 1s state of $TiO_2$ particles/carbon fiber induced by e-beam treatment could be related to the enhancement of the photocatalytic activity. In contrast, when carbon fiber fully covered with $TiO_2$ thick films was treated with high-energy electron beam under same conditions, the improvement of photocatalytic activity as well as any changes in XPS spectra (Ti 2p, O 1s and C 1s) could not be found.

• Proceedings of the Korean Society of Food Science and Nutrition Conference
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• 2004.11a
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• pp.185-197
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• 2004

Type 2 diabetes is characterized by hyperglycemia and hyperinsulinemia, features of insulin resistance. In vivo treatment of ob/ob mice with hydrolyzed fibroin reverses these pathological attributes (6). To explore the mechanism underlying this effect, we have used the 3T3-Ll adipocytes as a cell type which would represent the periphery, in vivo. Exposure of 3T3-Ll adipocytes to chronic insulin leads to the a 50% loss of insulin-stimulated glucose uptake. Chronic exposure to fibroin blocked, in part, the response to chronic insulin but also increased the sensitivity of control cells to the acute action of insulin. The later effect was most robust at physiological concentrations of insulin. Fibroin did not prevent the insulin-induced down-regulation of the insulin receptor or the tyrosine kinase activity associated with the receptor. Further, fibroin had no affect on the loss in activity of the insulin-sensitive down-stream kinase, Akt. Interestingly, fibroin accelerated glucose metabolism and glycogen turnover independent of insulin action. In addition, fibroin up-regulated GLUT1 which increased its expression at the cell surface and caused the redistribution of GLUT4 to the plasma membrane. Together, these later effects would lead to an improvement in hyperglycemia in vivo which would in turn reduce the need for insulin.

• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.475-480
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• 2003

Nanocomposite of Au doped ZrO$_2$ films was prepared, which could be used as non-linear optic materials, selective absorption and transmission films. After heat treatment of prepared thin film by dip-coating method, the characteristics were investigated by X-ray diffraction, UV-VIS Spectrometer, Atomic Force Microscopy (AFM) and Scanning Electron Microscope (SEM). Film thickness was about 150 nm, the Au particle size was 15~35 nm. The thin film had a smooth surface roughness about 1.06 nm. Nonlinearity optics was found that films showed absorption peak at 600~650 nm visible region by plasma resonance of Au metal particles.