• Journal of Microbiology and Biotechnology
• /
• v.17 no.6
• /
• pp.928-933
• /
• 2007

Cameleon is a genetically engineered $Ca^{2+}$ sensing molecule consisting of two variants of the green fluorescent protein (GFP), calmodulin and calmodulin-binding protein, M13. HEK-293 cells stably expressing three types of cameleons, yellow cameleon-2, cameleon-3er, and cameleon-2nu, were constructed, and the expression and localization of these cameleons were confirmed by fluorescent imaging. Among the cameleons, the yellow cameleon-2 was selected for analyzing the change in $Ca^{2+}$ induced by the olfactory receptor-mediated signal transduction, because it is localized in the cytosol and binds to cytosolic $Ca^{2+}$ ions. Cells stably expressing yellow cameleon-2 were transfected with each of the test olfactory receptor genes, odr-10 and 17, and the expression of the olfactory receptor genes were examined using immunocytochenmical methods and RT-PCR. Stimulating each olfactory receptor with its specific odorant caused an increase in the intracellular $Ca^{2+}$ level, which was measured using yellow cameleon-2. These results demonstrate that yellow cameleon-2 can be conveniently used to examine the function of the olfactory receptors expressed in heterologous cells.

• Journal of the Korean Chemical Society
• /
• v.28 no.4
• /
• pp.238-243
• /
• 1984

Three component $Ag_2S-PbS-PbMoO_4$ electrodes have been prepared and evaluated for sensitivity to molybdate. The 64.5 : 14.0 : 21.5(w/w%) composition is superior in terms of potentiometric response, stability, rapidity of response and reproducibility. Testing was done over the concentration range of $10^{-1}{\sim}10^{-5}M\;MoO_4^{2-}\;in\;0.1F\;NH_4Ac-NH_4OH$ buffer solution at pH 7.95 with constant ionic strength. $I^-,\;Cl^-,\;Br^-\;and\;CN^-$, etc. interfere.

• Journal of the Korean Chemical Society
• /
• v.36 no.5
• /
• pp.753-759
• /
• 1992

It is shown that receptacle tissue of the rose of sharon can serve as an effective biocatalyst by the construction of a potentiometric membrane electrode with response and selectivity for arginine. Electrodes using this tissue in conjunction with $NH_3$ gas sensing probes yield good response to arginine in $10^{-1}M to 10^{-3}M$ range and retain activity for a least 1 weeks. The arginine-selective membrane electrode using tissue slices of the rose of sharon have good selectivity in presence of other amino acids. The optimum conditions are pH 8.0, $25^{\circ}C$ and $20 {\mu}m$ thickness of slices in 0.1 M phosphate buffer solution and $K_m$ values is $6.4 {\times} 10^{-6}(M)$.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.12
• /
• pp.3427-3432
• /
• 2014

This study introduces a new method of combining Imaging Differential Optical Absorption Spectroscopy (Imaging-DOAS) data and plume dispersion formulas for power plant emissions to determine the three-dimensional structure of a dispersing pollution plume and the spatial distributions of trace gas volume mixing ratios (VMRs) under conditions of negligible water droplet and aerosol effects on radiative transfer within the plume. This novel remote-sensing method, applied to a power plant stack plume, was used to calculate the two-dimensional distributions of sulfur dioxide ($SO_2$) and nitrogen dioxide ($NO_2$) VMRs in stack emissions for the first time. High $SO_2$ VMRs were observed only near the emission source, whereas high $NO_2$ VMRs were observed at locations several hundreds of meters away from the initial emission. The results of this study demonstrate the capability of this new method as a tool for estimating plume dimensions and trace gas VMRs in power plant emissions.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.157-157
• /
• 2011

Graphene has generated significant interest in the recent years as a functional material for electronics, sensing, and energy applications due to its unique electrical, optical, and mechanical properties. Much of the considerable interest in graphene stems from results obtained for samples mechanically exfoliated from graphite. Practical applications, however, require reliable and well-controlled methods for fabrication of large area graphene films. Recently high quality graphene layers were fabricated using chemical vapor deposition (CVD) on nickel and copper with methane as the source of the carbon atoms. Here, we report a simple and efficient method to synthesize graphene layers using solid carbon source. Few-layer graphene films are grown using filtered vacuum arc source (FVAS) technique by evaporation of carbon atom on Ni catalytic metal and subsequent annealing of the samples at 800$^{\circ}$C. In our system, carbon atoms diffuse into the Ni metal layer at elevated temperatures followed by their segregation as graphene on the free surface during the cooling down step as the solubility of carbon in the metal decrease. For a given annealing condition and cooling rate, the number of graphene layers is easily controlled by changing the thickness of the initially evaporated amorphous carbon film. Based on the Raman analysis, the quality of graphene is comparable to other synthesis methods found in the literature, such as CVD and chemical methods.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.11
• /
• pp.3128-3132
• /
• 2010

A disposable solid-state pH sensor was realized by utilizing two nanoporous Pt (npPt) electrodes and a copolyelectrolytic junction. One nanoporous Pt electrode was to measure the pH as an indicating electrode (pH-IE) and the other assembled with copolyelectrolytic junction was to maintain constant open circuit potential ($E_{oc}$) as a solid-state reference electrode (SSRE). The copolyelectrolytic junction was composed of cationic and anionic polymers immobilized by photo-polymerization of N,N'-methylenebisacrylamide, making buffered electrolytic environment on the SSRE. It was expected to make. The nanoporous Pt surrounded by a constant pH excellently worked as a solid state reference electrode so as to stabilize the system within 30 s and retain the electrochemical environment regardless of unknown sample solutions. Combination between the SSRE and the pH-IE commonly based on nanoporous Pt yielded a complete solid-state pH sensor that requires no internal filling solution. The solid state pH sensing chip is simple and easy to fabricate so that it could be practically used for disposable purposes. Moreover, the solid-state pH sensor successfully functions in calibration-free mode in a variety of buffers and surfactant samples.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.11
• /
• pp.3357-3361
• /
• 2013

Alumina microfibers with porous structures were prepared through hydrothermal reaction, and then used to modify the surface of carbon paste electrode (CPE). After modification with alumina microfibers, the electrochemical activity of CPE was found to be greatly improved. On the surface of alumina microfibers-modified CPE, the oxidation peak current of salvianolic acid B, a main bioactive compound in Danshen with anti-oxidative and anti-inflammatory effects, was remarkably increased compared with that on the bare CPE surface. The influences of pH value, amount of alumina microfibers and accumulation time were studied. Based on the strong signal amplification effects of alumina microfibers, a novel electrochemical method was developed for the detection of salvianolic acid B. The linear range was from 5 ${\mu}gL^{-1}$ to 0.3 mg $L^{-1}$, and the detection limit was 2 ${\mu}gL^{-1}$ (2.78 nM) after 1-min accumulation. The new method was successfully used to detect salvianolic acid B in ShuangDan oral liquid samples, and the recovery was over the range from 97.4% to 102.9%.

• Journal of the Korean Chemical Society
• /
• v.36 no.4
• /
• pp.496-503
• /
• 1992

An ISFET urea sensor was fabricated by immobilizing the urease using photosensitive polymer, poly(vinyl alcohol)-SbQ on the H$^+$ sensing $Si_3$$N_4$ thin film of pH-ISFET. The sensor could determine the urea concentration in the range of 1∼50 mg/dl with fast response and good repeatability. For its application to clinical analysis, the interferences of the various materials which cause inhibition in urease catalytic reactions in blood was investigated. The results of the urea measurements in blood plasma using the ISFET urea sensor were compared with these of conventional spectrophotometric method.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.2
• /
• pp.489-493
• /
• 2014

A phenylbenzimidazole derivatized sensor (L) that behaves as a ratiometric fluorescent receptor for $Zn^{2+}$ in water has been described. In HEPES buffer at pH 7.4, sensor L displays a weak fluorescence emission band at 367 nm. Upon addition of $Zn^{2+}$, the emission intensity at 367 nm is decreased, concomitantly, a new emission band centered at 426 nm is developed, thus facilitates a ratiometric $Zn^{2+}$ sensing behavior. Sensor L binds $Zn^{2+}$ through a 1:1 binding stoichiometry with high selectivity over other metal cations. Sensor L displays a linear response to $Zn^{2+}$ concentration from 0 to $6.0{\times}10^{-5}M$, sensor L also exhibits high sensitivity to $Zn^{2+}$ with a detection limit of $3.31{\times}10^{-7}M$.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.7
• /
• pp.1323-1325
• /
• 2008

The acetylene black (AB) was dispersed into water in the presence of dihexadecyl hydrogen phosphate (DHP) via ultrasonication, resulting in a stable and well-distributed AB/DHP suspension. After evaporation of water, an AB/DHP composite film-modified electrode was prepared. The electrochemical responses of $K_3$[Fe$(CN)_6$] at the unmodified electrode, DHP film-modified electrode and AB/DHP film-modified electrode were investigated. It is found that the AB/DHP film-modified electrode possesses larger surface area and electron transfer rate constant. Furthermore, the electrochemical behaviors of 1-naphthylacetic acid (NAA) were examined. At the AB/DHP film-modified electrode, the oxidation peak current of NAA remarkably increases. Based on this, a sensitive and convenient electrochemical method was proposed for the determination of NAA. The linear range is in the range from $4.0 {\times} 10^{-8}\;to\;5.0 {\times} 10^{-6}$ mol $L^{-1}$, and the detection limit is $1.0 {\times} 10^{-8}$ mol $L^{-1}$. Finally, this new sensing method was employed to determine NAA in several soil samples.