• BMB Reports
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• v.39 no.6
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• pp.717-721
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• 2006

In vitro analyses of type I signal peptidase activities require protein precursors as substrates. Usually, these pre-proteins are expressed in vitro and cleavage of the signal sequence is followed by SDS polyacrylamide gel electrophoresis coupled with autoradiography. Radioactive amino acids have to be incorporated in the expressed protein, since the amount of the in vitro expressed protein is usually very low and processing of the signal peptide cannot be followed by SDS polyacrylamide gel electrophoresis alone. Here we describe a rapid and simple method to express large amounts of a protein precursor in E. coli. We have analyzed the effect of ionophors as well as of azide on the accumulation of expressed protein precursors. Azide blocks the function of SecA and the ionophors dissipate the electrochemical gradient across the cytoplasmic membrane of E. coli. Addition of azide ions resulted in the formation of inclusion bodies, highly enriched with pre-apo-plastocyanine. Plastocyanine is a soluble copper protein, which can be found in the periplasmic space of cyanobacteria as well as in the thylakoid lumen of cyanobacteria and chloroplasts, and the pre-protein contains a cleavable signal sequence at its N-terminus. After purification of cyanobacterial pre-apo-plastocyanine, its signal sequence can be cleaved off by the E. coli signal peptidase, and protein processing was followed on Coomassie stained SDS polyacrylamide gels. We are optimistic that the presented method can be further developed and applied.

• Progress in Superconductivity and Cryogenics
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• v.1 no.1
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• pp.7-14
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• 1999

Wekk oriented $Bi_{2} Sr_{2} CaCu_{2} O_{8}$ suppercondcting thick films were fabricared on copper tape by LiReac-PreCu (liquid reaction between a Cu-free precousor and Cu tape) method. Cu-free precursor power which is composed of $Bi_{2}Sr_{2}Ca_{5}$ was printed on a copper tape by screen printing and was heat-treated. The speciment were partially in a molten state at the heat treatment temperature (85$0^{\circ}C$~87$0^{\circ}C$). The heat heat treatments for the reaction were performed in air or low oxygen pressure in several stages. XRD analyses of the resulting Bi2Sr2CaCu2O8 superconducting tapes show that the $Bi_{2} Sr_{2} CaCu_{2} O_{8}$ phase is dominant and a small amount of $Bi_{2} Sr_{2} Cu_{2} O_{6}$ phase is detected. Both phases are aligned in the c-axis direction.

• Transactions on Electrical and Electronic Materials
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• v.13 no.6
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• pp.305-309
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• 2012

In this study, ZnO nanorods and $SnO_2$-CuO heterogeneous oxide were grown on membrane-type gas sensor platforms and the sensing characteristics for carbon monoxide (CO) were studied. Diaphragm-type gas sensor platforms with built-in Pt micro-heaters were made using a conventional bulk micromachining method. ZnO nanorods were grown from ZnO seed layers using the hydrothermal method, and the average diameter and length of the nanorods were adjusted by changing the concentration of the precursor. Thereafter, $SnO_2$-CuO heterogeneous oxide thin films were grown from evaporated Sn and Cu thin films. The average diameters of the ZnO nanorods obtained by changing the concentration of the precursor were between 30 and 200 nm and the ZnO nanorods showed a sensitivity value of 21% at a working temperature of $350^{\circ}C$ and a carbon monoxide concentration of 100 ppm. The $SnO_2$-CuO heterogeneous oxide thin films showed a sensitivity value of 18% at a working temperature of $200^{\circ}C$ and a carbon monoxide concentration of 100 ppm.

• Bulletin of the Korean Chemical Society
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• v.35 no.10
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• pp.2917-2921
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• 2014

Cerium-activated yttrium aluminate ($Y_3Al_5O_{12}:Ce^{3+}$) exhibiting a garnet structure has been widely utilized in the production of light emitting diodes (LEDs) as a yellow emitting phosphor. The commercialized yttrium aluminum garnet (YAG) phosphor is typically synthesized by a solid-state reaction, which produces irregular shape particles with a size of several tens of micrometers by using the top-down method. To control the shape and size of particles, which had been the primary disadvantage of top-down synthetic methods, we synthesized YAG:Ce nanoparticles with a diameter of 500 nm using a coprecipitation method under the atmospheric pressure without the use of template or special equipment. The precursor particles were formed by refluxing an aqueous solution of the nitrate salts of Y, Al, and Ce, urea, and polyvinylpyrrolidone (55 K) at $100^{\circ}C$ for 12 h. YAG:Ce nanoparticles were formed by the calcination of precursor particles at $1100^{\circ}C$ for 10 h under atmospheric conditions. The phase identification, microstructure, and photoluminescent properties of the products were evaluated by X-ray powder diffraction, scanning electron microscopy, absorption spectrum and photoluminescence analyses.

• Korean Journal of Materials Research
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• v.12 no.5
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• pp.391-397
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• 2002

Synthesis and process development of nano-size Ti powder by SFE(Sodium/halide Flame Encapsulation) method were investigated. Four concentric coflow burner was used and its flame configuration was $TiCl_4/Ar/Na/Ar$ in order from the center. Flame has been controlled by the various processing parameters such as temperature of burner and flow rates of both $TiCl_4$(g) precursor and Na(g). It was found that yellow-colored flame was shown in the flow rates of 70cc/min of $TiCl_4$(g) precursor and 2 $\ell$ /min of Na(g) which were regarded as optimum flame condition. The powders encapsuled by NaCl were produced having the average powder size of 250nm. The results of X-ray diffraction showed that powders from the optimized condition consisted of pure Ti and NaCl. TEM analysis confirmed that the several Ti powders of 20-100nm were encapsulated with NaCl. After removing sodium chloride by heat treatment, the spherical Ti powders with the size range of 80 to 150nm were obtained.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.9
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• pp.561-564
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• 2015

Nano-size $BaTiO_3$ powder was synthesized by relatively simple hydrothermal reaction method. Finely dispersed Ti hydroxide precursor was first precipitated using $Ti(SO_4)_2$ and NaOH solution by applying ultrasonic power and washed thoroughly to remove $SO_4{^{2-}}$ and $Na^+$ ion. Then hydrothermal reaction was done at $160^{\circ}C$ for 6 hrs using solution prepared by washed Ti hydroxide precursor slurry and $Ba(OH)_2{\cdot}8H_2O$ with Ti:Ba mole ratio of 1:1. 200 ~ 500 nm size and uniform size distributed $BaTiO_3$ powder was synthesized by relatively low temperature and simple process.

• Journal of Mechanical Science and Technology
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• v.20 no.6
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• pp.819-827
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• 2006

The stress-strain relation of aluminum (Al) alloy foam cell wall was evaluated by the instrumented sharp indentation method. The indentation in a few micron ranges was performed on the cell wall of Al-alloy foam having a composition or Al-3wt.%Si-2wt.%Cu-2wt.%Mg as well as its precursor (material prior to foaming). To extract the stress-stram relation in terms of yield stress ${\sigma}_y$, strain hardening exponent n and elastic modulus E, the closed-form dimensionless relationships between load-indentation depth curve and elasto-plastic property were used. The tensile properties of precursor material of Al-alloy foam were also measured independently by uni-axial tensile test. In order to verify the validity of the extracted stress-strain relation, it was compared with the results of tensile test and finite element (FE) analysis. A modified cubic-spherical lattice model was proposed to analyze the compressive behavior of the Al-alloy foam. The material parameters extracted by the instrumented nanoindentation method allowed the model to predict the compressive behavior of the Al-alloy foam accurately.

• Journal of Surface Science and Engineering
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• v.52 no.1
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• pp.6-15
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• 2019

Metal-halide perovskite (MHP) solar cell is a promising candidate for next-generation flexible devices and the BIPV (Building-integrated photovoltaics) because it can exhibit high power conversion efficiencies over 23%, good bendability and low processing cost. However, MHP solar cells are commonly fabricated by the spin coating that is not a reliable method to produce large-scale commercial solar cells. A shear coating can be one of the potential candidates for the large-scale deposition method of MHP films. In this work, the influences of the process parameters such as solvents of precursor solution, substrate temperature, concentrations of precursor solution, and annealing time on the thin film growth of MHP were investigated for the shear coating process. This study presents the possibility of the shear coating process for large-scaled perovskite film fabrication and reveals the role of process condition in the thin film growth of perovskites.

• Current Photovoltaic Research
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• v.9 no.4
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• pp.137-144
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• 2021

In this study, the microstructure of the CVD-fabricated Cu(In,Ga)Se₂ (CIGSe) absorber layer by simulating the stacking sequence used in a co-evaporation method, and changes solar cell performance were investigated. The absorber layer prepared by stacking CuSe and (In,Ga)Se between InSe is separated into Ga-free CuInSe₂ and Ga-rich CIGSe, and transformed to CIGSe by selenization heat treatment with slight improvement in the the solar cell efficiency. However, in CVD, since the supply of liquid Cu-Se is not as active as in the co-evaporation method, the nanoocrystalline layer containing a large amount of Ga remained independently in the absorption layer, which acted as a cause of the loss of J_SC and FF. Therefore, by using a precursor structure in which CuGa is sputter-deposited on a single layer of InSe deposited by CVD, performance parameters of V_OC, J_SC, and FF could be greatly improved.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.6 no.2
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• pp.69-74
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• 2020

PIB is the first amyloid plaque PET image tracer reported for the first time in 2003, and is considered to be the best and is still being utilized due to its very high uptake and kinetic properties. Initially, it was synthesized by radioisotope labeling using a precursor containing a methoxy methyl protection group, but now it is synthesized using a 6-OH precursor that can be easily synthesized in one step using [¹¹C]methyl triflate. Carbon-11 has several limitations in clinical studies using PET because its half-life is as short as 20 minutes. In this study, in order to overcome the difficulty of this half-life, a rapid method using Sep-Pak was adopted instead of HPLC purification to significantly reduce the burden of the purification process and attempted synthesis. As a result, the synthesis time was shortened by more than 50%, and the yield of the final compound was higher than the previous result and showed relatively high specific radioactivity, confirming that it is a strategic method with high applicability for various precursors having primary amines.