• Journal of Microbiology and Biotechnology
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• v.30 no.1
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• pp.109-117
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• 2020

Cre recombinase is widely used to manipulate DNA sequences for both in vitro and in vivo research. Attachment of a trans-activator of transcription (TAT) sequence to Cre allows TAT-Cre to penetrate the cell membrane, and the addition of a nuclear localization signal (NLS) helps the enzyme to translocate into the nucleus. Since the yield of recombinant TAT-Cre is limited by formation of inclusion bodies, we hypothesized that the positively charged arginine-rich TAT sequence causes the inclusion body formation, whereas its neutralization by the addition of a negatively charged sequence improves solubility of the protein. To prove this, we neutralized the positively charged TAT sequence by proximally attaching a negatively charged poly-glutamate (E12) sequence. We found that the E12 tag improved the solubility and yield of E12-TAT-NLS-Cre (E12-TAT-Cre) compared with those of TAT-NLS-Cre (TAT-Cre) when expressed in E. coli. Furthermore, the growth of cells expressing E12-TAT-Cre was increased compared with that of the cells expressing TAT-Cre. Efficacy of the purified TAT-Cre was confirmed by a recombination test on a floxed plasmid in a cell-free system and 293 FT cells. Taken together, our results suggest that attachment of the E12 sequence to TAT-Cre improves its solubility during expression in E. coli (possibly by neutralizing the ionic-charge effects of the TAT sequence) and consequently increases the yield. This method can be applied to the production of transducible proteins for research and therapeutic purposes.

• Environmental Engineering Research
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• v.16 no.2
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• pp.81-90
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• 2011

Different weight percentages of Ag, Pt, and Au doped nano $TiO_2$ were synthesized using the acetic acid hydrolyzed sol-gel method. The crystallite phase, surface morphology combined with elemental composition and light absorption properties of the doped nano $TiO_2$ were comprehensively examined using X-ray diffraction (XRD), $N_2$ sorption analysis, transmission electron microscopic (TEM), energy dispersive X-ray, and DRS UV-vis analysis. The doping of noble metals stabilized the anatase phase, without conversion to rutile phase. The formation of gold nano particles in Au doped nano $TiO_2$ was confirmed from the XRD patterns for gold. The specific surface area was found to be in the range 50 to 85 $m^2$/g. TEM images confirmed the formation a hexagonal plate like morphology of nano $TiO_2$. The photocatalytic activity of doped nano $TiO_2$ was evaluated using 4-chlorophenol as the model pollutant. Au doped (0.5 wt %) nano $TiO_2$ was found to exhibit higher photocatalytic activity than the other noble metal doped nano $TiO_2$, pure nano $TiO_2$ and commercial $TiO_2$ (Degussa P-25). This enhanced photocatalytic activity was due to the cathodic influence of gold in suppressing the electron-hole recombination during the reaction.

• Journal of the Korean Applied Science and Technology
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• v.17 no.2
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• pp.120-125
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• 2000

The tfTZ(4,4',4''-trifluoro-triazine) was used as a hole blocking material for the electroluminescent devices(ELDs) in this study. In general, the holes are outnumbered the electrons in hole transport and emitting layers because the hole transport is more efficient in most organic ELDs. The hole blocking layer are expected to control the excess holes to increase the recombination of holes and electrons and to decrease current density. The former study using the 2,4,6-triphenyl-1,3,5-triazine(TTA) as hole blocking layer showed that the TTA did not form stable films with vapor deposition technique. The tfTZ can generate stable evaporated films, moreover the fluorine group can lower the highest occupied molecular orbital(HOMO) level, which produces the energy barrier for the holes. The tfTZ has high electron affinities according to the data by the Cyclic-Voltammety(CV) method, which is developed for the measurement of HOMO and lowest occupied molecular orbital(LUMO) level of organic thin films. The lowered HOMO level is made the tfTZ to be applied for a hole blocking layer in ELDs. We fabricated multilayer ELDs with a structure of ITO/hole blocking layer(HBL)/hole transporting layer(HTL)/emitting layer/electrode. The hole blocking properties of this devices is confirmed from the lowered current density values compared with that without hole blocking layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.116-117
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• 2006

We investigated selective emitter effect of Porous Silicon (PSI) as antireflection coatings (ARC). The thin PSi layer, less than 100nm, was electrochemically formed by electrochemical method in about $3{\mu}m$ thick $n^+$ emitter on single crystalline silicon wafer (sc-Si). The appropriate PSi formations for selective emitter effect were carried out a two steps. A first set of samples allowed to be etched after metal-contact processing and a second one to evaporate Ag front-side metallization on PSi layer, by evaluating the I-V features The PSi has reflectance less than 20% in wavelength for 450-1000nm and porosity is about 60%. The cell made after front-contact has improved cell efficiency of about in comparison with the one made after PSi. The observed increase of efficiency for samples with PSi coating could be explained not only by the reduction of the reflection loss and surface recombination but also by the increased short-circuit current (Isc) within selective emitter. The assumption was confirmed by numerical modeling. The obtained results point out that it would be possible to prepare a solar cell over 15% efficiency by the proposed simple technology.

• Korean Journal of Microbiology
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• v.25 no.2
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• pp.122-128
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• 1987

Several bacterial isolates capable of degrading 4-chlorobiphenyl or 2,4,5-trichlorophenoxyacetic acid were isolated from industrial wastes by the agar plate method and studied for their biodegradabilities of the hydrocarbons and some biochemical characteristics. The isolates DJ-12, DJ-26 and TP-1 were identified as Pseudomonas spp. and they could not degrade 2,4-dichlorophenoxyacetic acid. The absorption spectra for 4-chlorobiphenyl and 2,4,5-trichlorophenoxyacetic acid showed the peaks at 253 and 292 nm, respectively. Biodegradability of the isolates was determined by decrease of the absorbance for the test hydrocarbons with a UV-scanning spectrophotometer. The plasmids of the isolates were studied to examine whether or not the hydrocarbon-degrading genes exist in the plasmids. Antibiotics resistance was also examined to search out a proper marker for the isolates in further experiments, such as curing test and genetic recombination.

• Journal of the Korean Chemical Society
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• v.25 no.5
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• pp.325-330
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• 1981

The electrochemical behavior of cadmium electrode for the nickel-cadmium battery system has been studied by cyclic voltammetry, controlled potential electrolysis and X-ray diffraction method. Cathodic polarization curve for cadmium hydroxide electrode prepared by electrochemical pretreatment of metallic cadmium showed two peaks. It has been found that cadmium hydroxide was reduced to cadmium metal at the first peak potential, whereas very activated metal of cadmium which was strongly oriented (002) rather than (101) was formed at the second peak potential. It was also found that the cadmium formed at the second peak potential reacted rapidly with oxygen. Therefore, it could be presumed that the cadmium recombination reaction with the oxygen was chemical, and could be represented as $2Cd + O_2 + 2H_2O\;{\longrightarrow}\;2Cd(OH)_2$.

• IMMUNE NETWORK
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• v.2 no.4
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• pp.248-255
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• 2002

Background: TAP1 and TAP2 are two ABC transporter genes located within the class II region of the human MHC. Their protein products form a heterodimer whose function is to transport peptides from the cytoplasm into the endoplasmic reticulum. This study was performed to examine the polymorphism of TAP genes and the distribution of HLA-TAP haplotypes in the Korean population through family analysis. Methods: The subjects used in this study were 50 healthy Korean families consisting of 233 individuals. TAP1 (codons 333 and 637) and TAP2 (codons 379, 565, 577, 651, 665, and 687) typings were carried out by the PCR-restriction fragment length polymorphism (RFLP) method. HLA-DRB1 and DQB1 genotyping results from a previous study were used for HLA-TAP haplotype analysis. Results: The number (gene frequency) of TAP1 and TAP2 alleles detected were 3 for TAP1 (A 81.5%, B 17.0%, and C 1.5%) and 8 for TAP2 (A1 32.0%, A2 12.5%, B 34.0%, Bky2 6.5%, C 7.0%, D 3.0%, E 4.5%, and G 0.5%). Eleven TAP1-TAP2 haplotypes were observed with $frequency{\geq}1%$, among which 4 haplotypes (A-B, B-A1, A-Bky2, and C-E) showed weak but significant positive linkage disequilibrium (P<0.05). When DRB1-DQB1 haplotypes were extended to TAP1 and TAP2 loci, much diversification of haplotypes was observed: 19 different DRB1-DQB1 haplotypes formed 58 different haplotypes extended to TAP1 and TAP2 loci. These results add more evidence to the view that recombination hotspot is present within and around TAP gene region. Conclusion: The allele frequencies of TAP1 and TAP2 genes and the distribution of TAP1-TAP2 and HLA-TAP haplotypes were studied in Koreans based on a family study.

• Applied Chemistry for Engineering
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• v.28 no.2
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• pp.245-251
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• 2017

In this study, ZnO, which is widely known as a non $TiO_2$ photocatalyst, was synthesized using coprecipitation method and Ag was added in order to improve the catalytic performance. The physicochemical characteristics of the synthesized ZnO and Ag/ZnO particles were checked using X-ray diffraction (XRD), UV-visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL), and photocurrent measurements. The performance of catalysts was tested by $H_2$ production using the photolysis of $H_2O$ with MeOH. By adding Ag which plays a role as an electron capture on the ZnO catalyst, the performance increased due to the recombination of excited electrons and holes. In particular, $8.60{\mu}mol\;g^{-1}$ $H_2$ was produced after 10 h reaction over the 0.50 mol% Ag/ZnO.

• Korean Journal of Materials Research
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• v.20 no.5
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• pp.246-251
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• 2010

The composite photocatalysts of a Fe-modified carbon nanotube (CNT)-$TiO_2$ were synthesized by a two-step sol-gel method at high temperature. Its chemical composition and surface properties were investigated by BET surface area, scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD) and ultraviolet-visible (UV-Vis) spectroscopy. The results showed that the BET surface area was improved by modification of Fe, which was related to the adsorption capacity for each composite. Interesting thin layer aggregates of nanosized $TiO_2$ were observed from TEM images, probably stabilized by the presence of CNT, and the surface and structural characterization of the samples was carried out. The XRD results showed that the Fe/CNT-$TiO_2$ composites contained a mix of anatase and rutile forms of $TiO_2$ particles when the precursor is $TiOSO_4{\cdot}xH_2O$ (TOS). An excellent photocatalytic activity of Fe/CNT-$TiO_2$ was obtained for the degradation of methylene blue (MB) under visible light irradiation. It was considered that Fe cation could be doped into the matrix of $TiO_2$, which could hinder the recombination rate of the excited electrons/holes. The photocatalytic activity of the composites was also found to depend on the presence of CNT. The synergistic effects among the Fe, CNT and $TiO_2$ components were responsible for improving the visible light photocatalytic activity.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.337-337
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• 2012

Dye sensitized solar cell (DSSC) having high efficiency with low cost was first reported by Gr$\ddot{a}$tzel et al. Many DSSC research groups attempt to enhance energy conversion efficiency by modifying the dye, electrolyte, Pt-coated electrode, and $TiO_2$ films. However, there are still some problems against realization of high-sensitivity DSSC such as the recombination of injected electrons in conduction band and the limited adsorption of dye on $TiO_2$ surface. The surface of $TiO_2$ is very important for improving hydrophilic property and dye adsorption on its surface. In this paper, we report a very efficient method to improve the efficiency and stability of DSSC with nano-structured $TiO_2$. Atmospheric plasma system was utilized for nitrogen plasma treatment on nano-structured $TiO_2$ film. We confirmed that the efficiency of DSSC was significantly dependent on plasma power. Relative in the $TiO_2$ surface change and characteristics after plasma was investigated by various analysis methods. The structure of $TiO_2$ films was examined by X-ray diffraction (XRD). The morphology of $TiO_2$ films was observed using a field emission scanning electron microscope (FE-SEM). The surface elemental composition was determined using X-ray photoelectron spectroscopy (XPS). Each of plasma power differently affected conversion efficiency of DSSC with plasma-treated $TiO_2$ compared to untreated DSSC under AM 1.5 G spectral illumination of $100mWcm^{-2}$.