• 한국진공학회:학술대회논문집
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• 한국진공학회 1996년도 제11회 학술발표회 논문개요집
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• pp.40-41
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• 1996

Nitridation technique has been receiving much attention for the formation of a thin nitrided buffer layer on which high quality nitride films can be formedl. Particularly, gallium nitride (GaN) has been considered as a promising material for blue-and ultraviolet-emitting devices. It can also be used for in situ formed and stable passivation layers for selective growth of $GaAs_2$. In this work, formation of a thin nitrided layer is investigated. Nitrogen electron cyclotron resonance(ECR)-plasma is employed for the formation of thin nitrided layer. The plasma source used in this work is a compact ECR plasma gun3 which is specifically designed to enhance control, and to provide in-situ monitoring of plasma parameters during plasma-assisted processing. Microwave power of 100-200 W was used to excite the plasma which was emitted from an orifice of 25 rnm in diameter. The substrate were positioned 15 em away from the orifice of plasma source. Prior to nitridation is performed, the surface of n-type (001)GaAs was exposed to hydrogen plasma for 20 min at $300{\;}^{\circ}C$ in order to eliminate a native oxide formed on GaAs surface. Change from ring to streak in RHEED pattern can be obtained through the irradiation of hydrogen plasma, indicating a clean surface. Nitridation was carried out for 5-40 min at $RT-600{\;}^{\circ}C$ in a ECR plasma-assisted molecular beam epitaxy system. Typical chamber pressure was $7.5{\times}lO^{-4}$ Torr during the nitridations at $N_2$ flow rate of 10 seem.(omitted)mitted)

• 한국양식학회지
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• 제18권3호
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• pp.173-179
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• 2005

Superoxide dismutase (SOD), an antioxidant enzyme catalyzing the first step for scavenging the reactive oxygen species is important as an early warning indicator to address various biological stresses. For this reason, the monitoring the expressed pattern of SOD gene in fish organs is one of important biomarkers to assess the aquatic pollution caused by many toxic chemicals. Based on the Northern blot hybridization, semi-quantitative and/or realtime RT-PCRs, the alteration of SOD gene transcripts in shark liver was examined during the experimental acute exposures to cadmium. The expression of SOD at mRNA level was up-regulated both by injection (0, 0.5, 1 or 2 mg $CdCl_2/kg$ body weight for 48 hours) and by immersion (0 or $5{\mu}M$ Cd for 0, 1, 4 and 7 days) treatments of cadmium. The transcriptional stimulation of shark SOD gene by cadmium exposure was dependent upon doses and durations: there was a trend toward more increase in higher dose and longer durations of exposure. The hepatic SOD mRNA levels showed also a general agreement with the tissue cadmium concentrations accumulated in immersion exposure. This result may provide useful strategy to develop a fine molecular biomarker at mRNA level for detecting aquatic pollution caused by toxic metals.

• 세라미스트
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• 제22권3호
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• pp.281-300
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• 2019

Surface enhanced Raman scattering (SERS) was first discovered in 1974 by an unexpected Raman signal increase from Pyridine adsorbed on rough Ag electrode surfaces by the M. Fleishmann group. M. Moskovits group suggested that this phenomenon could be caused by surface plasmon resonance (SPR), which is a collective oscillation of free electrons at the surface of metal nanostructures by an external light source. After about 40 years, the SERS study has attracted great attention as a biomolecule analysis technology, and more than 2500 new papers and 500 review papers related to SERS topic have been published each year in recently. The advantages of biomaterials analysis using SERS are as follows; ① Molecular level analysis is possible based on unique fingerprint information of biomolecule, ② There is no photo-bleaching effect of the Raman reporters, allowing long-term monitoring of biomaterials compared to fluorescence microscopy, ③ SERS peak bandwidth is approximately 10 to 100 times narrower than fluorescence emission from organic phosphor or quantum dot, resulting in higher analysis accuracy, ④ Single excitation wavelength allows analysis of various biomaterials, ⑤ By utilizing near-infrared (NIR) SERS-activated nanostructures and NIR excitation lasers, auto-fluorescence noise in the visible wavelength range can be avoided from in vivo experiment and light damage in living cells can be minimized compared to visible lasers, ⑥ The weak Raman signal of the water molecule makes it easy to analyze biomaterials in aqueous solutions. For this reason, SERS is attracting attention as a next-generation non-invasive medical diagnostic device as well as substance analysis. In this review, the principles of SERS and various biomaterial analysis principles using SERS analysis will be introduced through recent research papers.

• BMB Reports
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• 제33권3호
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• pp.242-248
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• 2000

Phage display of proteins is a powerful tool for protein engineering since a vast library of sequences can be rapidly screened for a specific property. In this study, we develop da new phage display vector that was derived from a pET-25b(+) vector. The pET-25b(+) was modified in order that the expressed protein would have a T7-tag at the amino terminus and GpS (a major coat protein of M13 phage) at the carboxyl terminus. Another vector without the gp8 gene was also constructed. The newly developed phagemid vectors have several advantageous features. First, it is easy to examine whether or not the target proteins are functional and faithfully transported into the periplasmic space. This feature is due to the fact that recombinant proteins are produced abundantly in the pET system. Second, the T7-tag makes it possible to detect any target proteins that are displayed on the surface of filamentous bacteriophage. To verify the utility of the vector, the clones containing the glutathione S-transferase (GST) gene as a target were examined. The result showed that the GST produced from the recombinant vector was successfully transported into the periplasmic space and had the anticipated enzyme activity. Western blot analysis using a T7-tag antibody also showed the presence of the target protein displayed on the surface of the phage. The phages prepared from the recombinant clones were able to bind to glutathione-Sepharose and then eluted with glutathione. These results showed that the new vectors developed in this study are useful for the phage display of proteins.

• 한국수산과학회지
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• 제39권6호
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• pp.454-459
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• 2006

A simultaneous high-performance liquid chromatography assay method for amoxicillin and ampicillin in fish products was developed, evaluated, and validated by monitoring these antibiotics in fish samples obtained from aquaculture and distribution. The recovery rate of this method was higher than those of conventional methods and was 95.3-106.6% for amoxicillin and 81.4-92.4% for ampicillin. Our pretreatment procedure sufficiently removed or reduced materials affecting HPLC analysis, such as low-molecular-weight substances. The performance limit of this method was evaluated as 0.01 ppm of amoxicillin and ampicillin in fish muscle. Finally, 171 fish samples, including olive flounder (Paralichthys olivaceus), common sea bass (Lateolabrax japonicus), and black rock fish (Sebastes schlegeli) collected from fish farms in the coastal area between April and September 2005 were analyzed to evaluate the overall efficiency of the method and to monitor the actual of amoxicillin and ampicillin usage in fish farms. The results indicated that the developed method was suitable for analyzing amoxicillin and ampicillin in fish muscle, and determined that those antibiotics were being used for fish farming but were not detected in fish samples during the shipping and distribution stages.

• Asian-Australasian Journal of Animal Sciences
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• 제16권12호
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• pp.1822-1829
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• 2003

Porcine colostrum and milk were separated into the acid-soluble and casein fractions by acidification followed by centrifuge. The acid-soluble fraction of porcine colostrum was further separated by liquid chromatography and anisotropic membrane filtration. Trypsin and chymotrypsin inhibitory capacity in porcine colostrum, milk and their components was determined by incubating bovine trypsin or chymotrypsin in a medium containing their corresponding substrates with or without addition of various amounts of porcine colostrum, porcine milk or their components. The inhibition of insulin-like growth factor I (IGF-I) and epidermal growth factor (EGF) degradation in pig small intestinal contents by porcine colostrum was measured by incubating iodinated IGF-I or EGF with the intestinal contents with or without addition of porcine colostrum. Degradation of labeled IGF-I or EGF was determined by monitoring the generation of radioactivity soluble in 30% trichloroacetic acid (TCA). The results showed that porcine colostrum had high levels of trypsin and chymotrypsin inhibitory activity and increased the stability of IGF-I and EGF in pig intestinal contents. The inhibitory activity declined rapidly during lactation. It was also found that trypsin and chymotrypsin inhibitory activity and the inhibition on IGF-I and EGF degradation in the acid-soluble fraction were higher than that in the casein fraction. Heat-resistance study indicated that trypsin inhibitors in porcine colostrum survived heat treatments of $100^{\circ}C$ water bath for up to 10 min, but exposure to boiling water bath for 30 min significantly decreased the inhibitory activity. Compared with the trypsin inhibitors, the chymotrypsin inhibitors were more heatsensitive. Separation of the acid-soluble fraction of porcine colostrum by liquid chromatography and anisotropic membrane filtration revealed that the trypsin and chymotrypsin inhibitory capacity was mainly due to a group of small proteins with molecular weight of 10,000-50,000. In conclusion, the present study confirmed the existence of high levels of protease inhibitors in porcine colostrum, and the inhibition of porcine colostrum on degradation of milk-borne growth factors in the pig small intestinal tract was demonstrated for the first time.

• Journal of Dairy Science and Biotechnology
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• 제31권2호
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• pp.171-177
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• 2013

The dairy industry has consistently grown via the expansion of dairy-based food categories. Dairy product consumption is stable since the nutrient composition in dairy products is ideal for human health. However, dairy products are highly susceptible to food-borne pathogens. Controlling the safety of dairy products is thus important when considering the nutrient-rich matrix of this food category. Currently, immunoassays or molecular biology techniques have been used to evaluate the safety of dairy products in Korea. These methods are based on the detection of proteins and thus have low reproducibility and sensitivity. Recent techniques to detect food-borne pathogens have focused on genetic analyses. Rapid detection methods for food-borne pathogens in milk and dairy products using polymerase chain reaction (PCR) techniques, such as conventional PCR, real-time PCR, repetitive sequence-based (rep)-PCR, PCR-denaturing gradient gel electrophoresis (DGGE), and digital PCR, are reviewed in this article. The aim of this review was to contribute knowledge of the relationship between microflora and the quality of dairy products. This study will also assist in the immediate monitoring of food-borne pathogens in milk and dairy products when an outbreak related to this food category occurs.

• Mass Spectrometry Letters
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• 제4권4호
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• pp.75-78
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• 2013

A gas chromatography/mass spectrometric (GC/MS) method was developed as a candidate reference method for the accurate determination of essential fatty acids (linoleic acid, ${\alpha}$- and ${\gamma}$-linolenic acids) in food supplemental oil products. Samples were spiked with three internal standards (stearic acid-$d_{35}$, $^{13}C_{18}$-linoleic acid, and $^{13}C_{18}$-${\alpha}$-linolenic acid). Samples were then subject to saponification, derivatization for methylation, and extraction by organic solvent. For GC/MS measurement, an Agilent HP-88 column, designed for the separation of fatty acid methyl esters, was selected after comparing with other columns as it provided better separation for target analytes. Target analytes and internal standards were detected by selected ion monitoring of molecular ions of their methyl ester forms. The GC/MS method was applied for the measurement of three botanical oils in NIST SRM 3274 (borage oil, evening primrose oil, and flax oil), and measurement results agreed with the certified values. Measurement results for target analytes which have corresponding isotope-labeled analogues as internal standard were calculated based on isotope dilution mass spectrometry (IDMS) approach, and compared with results calculated by using the other two internal standards. Results from the IDMS approach and the typical internal standard approach were in good agreement within their measurement uncertainties. It proves that the developed GC/MS method can provide similar metrological quality with IDMS methods for the measurement of fatty acids in natural oil samples if a proper fatty acid is used as an internal standard.

• Journal of Gastric Cancer
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• 제2권4호
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• pp.213-220
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• 2002

Purpose: The cDNA microarray provides a powerful alternative with an unprecedented view in monitoring geneexpression levels and leads to discoveries of regulatory pathways involved in complicated biological processes. Our aim is to explore the different gene-expression patterns in gastric adenocarcinomas. Materials and Methods: By using a cDNA microarray representing 4,600 cDNA clusters, we studied the expression profiling in 10 paired gastric adenocarcinoma samples and in adjacent noncancerous gastric tissues from the same patients. Alterations in the gene-expression levels were confirmed by Vsing Northern blots and reverse-transcription PCR (RT-PCR) in all of 4 randomly selected genes. Results: Genes those were expressed differently in cancer ous and noncancerous tissues were identified. 44 (of which 26 were known) and 92 (of which 43 were known) genes or cDNA were up- and down-regulated, respectively, in more than $80\%$ of the gastric adenocarcinoma samples. In cancer ous tissues, genes related to gene/protein expression, cellcycle regulation, and metabolism were mostly up-regulated whereas genes related to the oncogene/tumor suppressor gene, cell structure/motility, and immunology were mostly down-regulated. The semi-quantitative RT-PCR results for the four genes we tested were consistent with the array findings. Conclusions: These results provide not only a new molecular basis for understanding the biological properties of gastric adenocarcinomas but also a useful resource for future development of therapeutic targets and diagnostic markers for gastric adenocarcinomas.

• Asian Pacific Journal of Cancer Prevention
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• 제16권12호
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• pp.4833-4837
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• 2015

Biomarkers for preclinical diagnosis of cancer are valuable tools for detection of malignant tumors at early stages in groups at risk and screening healthy people, as well as monitoring disease recurrence after treatment of cancer. However the complexity of the body's response to the pathological processes makes it virtually impossible to evaluate this response to the development of the disease using a single biomarker that is present in the serum at low concentrations. An alternative approach to standard biomarker analysis is called immunosignature. Instead of going after biomarkers themselves this approach rely on the analysis of the humoral immune response to molecular changes associated with the development of pathological processes. It is known that antibodies are produced in response to proteins expressed during cancer development. Accordingly, the changes in antibody repertoire associated with tumor growth can serve as biomarkers of cancer. Immunosignature is a highly sensitive method for antibody repertoire analysis utilizing high density peptide microarrays. In the present review we discuss modern methods for antibody detection, as well as describe the principles and applications of immunosignature in research and clinical practice.