• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.283-283
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• 2010

The liquid metal ion sources(LMIS) in FIB system have many advantages of high current density, high brightness and low ion energy spread. Most FIB systems use LMIS because the ion beam spot size of LMIS is smaller than other ion sources. LMIS is basically emitted by an extractor but the new electrode called the suppressor is able to control the emission current. We investigated characteristics LMIS with a suppressor, the function of the suppressor in LMIS, the change of the electric field by the suppressor and the advantages of using the suppressor. The characteristics of the threshold voltage and current-voltage (I-V) were observed under the varying extracting voltage with floated suppressor voltage, and under the varying suppressor voltages with fixed extractor voltage. We also simulated LMIS with the suppressor through CST(Computer Simulation Technology). The emission current increases as the suppressor voltage decreases because the suppressor voltage which restrains the electric field goes down, The threshold voltage increases as the suppressor voltage increases. We can explain characteristics and functions of LMIS with a suppressor using the electric field.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.88-88
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• 2010

The liquid metal ion sources(LMIS) in FIB system have many advantages of high current density, high brightness, and low ion energy spread. Most FIB systems use LMIS because the beam spot size of LMIS is smaller than of gas field ionization sources(GFIS). LMIS basically consists of a emitter(needle, anode), a reservoir(gallium) and a extractor(cathode). But several LMIS have new electrode called the suppressor. We investigated characteristics of LMIS with a suppressor. The characteristics of the threshold voltage and current-voltage (I-V) were observed under the varying extracting voltage with floated suppressor voltage, and under the varying suppressor voltages with fixed extractor voltage. We also simulated LMIS with the suppressor through CST(Computer Simulation Technology). We can explain characteristics of LMIS with a suppressor using the electric field.

• Korean Journal of Head & Neck Oncology
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• v.20 no.2
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• pp.147-155
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• 2004

Objectives: Head and neck squamous cell carcinoma (HNSCC) is the most common head and neck malignant tumor. The molecular genetic changes involving both oncogenes and tumor suppressor genes are known to be involved in head and neck squamous cell carcinogenesis, but the roles of the known tumor suppressor genes in carcinogenesis are not fully elucidated. The objectives of this study are to demonstrate the genetic alterations including the loss of heterozygosity (LOH) , amplification, and microsatellite instability of known tumor suppressor genes in HNSCC and to evaluate the relationship between genetic alterations of tumor suppressor genes and clinicopathologic features. Materials and Methods: Genetic alterations of 10 micro satellite markers of the 6 known tumor suppressor genes (APC, EXT1, DPC4, p16, FHIT, and PTEN) were analysed by DNA-PCR in paraffin-embedded histologically confirmed HNSCC specimens. Results: The genetic alterations of tumor suppressor genes were found frequently. Among the genetic alterations, LOH was most frequently found one. LOH was found frequently in APC (45.4%), EXT1 (36.4%), DPC4 (54.5%), and p16 (50%), but not found in FHIT. Also, the author found that abnormalities of APC gene was related to cervical lymph node metastasis and recurrence and that abnormalities of EXT1 gene were coexisted with those of APC gene or DPC4 gene. But these coexistences had no correlation with clinical features. Conclusion: These results suggested that APC, EXT1, p16, and DPC4 genes might play important roles and multiple tumor suppressor genes may participate dependently or independently in the carcinogenesis of HNSCC. These results also suggested that APC gene might relate to prognosis.

• Analytical Science and Technology
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• v.12 no.2
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• pp.89-93
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• 1999

In this study, conductivity cell and suppressor for micro-column ion chromatography were developed to analyze ions in small columns of samples. With a capillary column, the flow rate of the mobile phase is so small (usually $5{\sim}20{\mu}L/min$) that the usual conductivity cell can not be used. Therefore, we developed a new type of conductivity cell and suppressor which have small inner volumes. The conductivity cell was made with two Pt hypodermic needles (i.d. 0.010 mm) which are slightly separated (about $2{\mu}m$), and the suppressor was made of Nafion tubings. When several anions(fluoride, nitrite, nitrate, chlorate) were analyzed using developed conductivity cell and suppressor, a good chromatogram was obtained.

• BMB Reports
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• v.48 no.8
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• pp.454-460
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• 2015

Naturally occurring reoviruses are live replication-proficient viruses that specifically infect human cancer cells while sparing their normal counterpart. Since the discovery of reoviruses in 1950s, they have shown various degrees of safety and efficacy in pre-clinical or clinical applications for human anti-cancer therapeutics. I have recently discovered that cellular tumor suppressor genes are also important in determining reoviral tropism. Carcinogenesis is a multi-step process involving the accumulation of both oncogene and tumor suppressor gene abnormalities. Reoviruses can exploit abnormal cellular tumor suppressor signaling for their oncolytic specificity and efficacy. Many tumor suppressor genes such as p53, ataxia telangiectasia mutated (ATM), and retinoblastoma associated (RB) are known to play important roles in genomic fidelity/maintenance. Thus, a tumor suppressor gene abnormality could affect host genomic integrity and likely disrupt intact antiviral networks due to the accumulation of genetic defects which in turn could result in oncolytic reovirus susceptibility. This review outlines the discovery of oncolytic reovirus strains, recent progresses in elucidating the molecular connection between oncogene/tumor suppressor gene abnormalities and reoviral oncotropism, and their clinical implications. Future directions in the utility of reovirus virotherapy is also proposed in this review. [BMB Reports 2015; 48(8): 454-460]

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.1039-1043
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• 1996

In the firing operation, muzzle jumping phenomenon was investigated, and a method of reducing muzzle jump was suggested. The muzzle jumping force was determined from the torque acting on the rifle due to a recoil force. For the purpose of reducing a muzzle jump, the gas flowing through the M16A1 flash suppressor was considered. A flash suppressor, improved in reducing a muzzle imp, was modeled and tested. The experiment shows that muzzle jump has quantitative relation to shape of a flash suppressor, and can be reduced by the improved modeling of a flash suppressor.

• Interdisciplinary Bio Central
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• v.4 no.3
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• pp.10.1-10.12
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• 2012

Introduction: We investigated frameshift suppressor tRNAs previously reported to use five-base anticodon-codon interactions in order to provide a collection of frameshift suppressor tRNAs to the synthetic biology community and to develop modular frameshift suppressor logic devices for use in synthetic biology applications. Results and Discussion: We adapted eleven previously described frameshift suppressor tRNAs to the BioBrick cloning format, and built three genetic logic circuits to detect frameshift suppression. The three circuits employed three different mechanisms: direct frameshift suppression of reporter gene mutations, frameshift suppression leading to positive feedback via quorum sensing, and enzymatic amplification of frameshift suppression signals. In the course of testing frameshift suppressor logic, we uncovered unexpected behavior in the frameshift suppressor tRNAs. The results led us to posit a four-base binding hypothesis for the frameshift suppressor tRNA interactions with mRNA as an alternative to the published five-base binding model. Conclusion and Prospects: The published five-base anticodon/codon rule explained only 17 of the 58 frameshift suppression experiments we conducted. Our deduced four-base binding rule successfully explained 56 out of our 58 frameshift suppression results. In the process of applying biological knowledge about frameshift suppressor tRNAs to the engineering application of frameshift suppressor logic, we discovered new biological knowledge. This knowledge leads to a redesign of the original engineering application and encourages new ones. Our study reinforces the concept that synthetic biology is often a winding path from science to engineering and back again; scientific investigations spark engineering applications, the implementation of which suggests new scientific investigations.

• Korean Journal of Microbiology
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• v.30 no.1
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• pp.37-41
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• 1992

The KEM1 gene is known to affect microtubule and spindle pole body function during the cell division cycle in Saccharomjyces cerevisiae. To identify new genes with functions similar or related to those of KEM1, we isolated a high copy suppressor gene (ROK1) that suppresses the kem1 mutation when cloned on a high copy number plasmid but not on a low copy number plasmid. Two clones which suppress both the benomyl hypersensitivity and the $Kar^{-}$ enhancing phenotype of kem1 null mutation were isolated and were shown to have a 9.0 kb identical insert by restriction endonuclease analysis. The restriction map constructed indicates that this suppressor gene, ROK1 is not KEM1. Subcloning experiments suggest that the functional region of ROK1 is at least 3.0kb in size.

• Korean Journal of Microbiology
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• v.45 no.2
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• pp.215-221
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• 2009

Site-specific incorporation of unnatural amino acids into proteins in vivo can be achieved by co-expression of an orthogonal pair of suppressor tRNA and engineered aminoacyl-tRNA synthetase (ARS) that specifically ligates an unnatural amino acid to the suppressor tRNA. As a step to establish this technique, here we generated an Escherichia coli reporter strain DH10B(Tn:lacZam) by integrating amber mutated lacZ gene into the chromosome of E. coli DH10B strain. In vivo expression of E. coli amber suppressor $tRNA^{Gln}$ produced blue colonies in culture plates containing X-Gal as well as dramatically increased $\beta$-galactosidase activity. In addition, expression of an orthogonal pair of Saccharomyces cerevisiae suppressor $tRNA^{Tyr}$ and tyrosyl-tRNA synthetase also produced blue colonies as well as moderate increase of $\beta$-galactosidase activity. These data demonstrate that our reporter strain will provide an efficient method to assess amber suppression in both qualitative and quantitative manners.

• Korean Journal of Microbiology
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• v.50 no.1
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• pp.1-7
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• 2014

Site-specific incorporation of unnatural amino acids (SSIUA) into protein can be achieved in vivo by coexpression of an orthogonal pair of suppressor tRNA and engineered aminoacyl-tRNA synthetase (ARS) that specifically ligates an unnatural amino acid to the suppressor tRNA. As a step to develop the SSIUA technique in Escherichia coli, here we established a new 2-step screening system that can be used for selecting an ARS variant(s) that ligates an unnatural amino acid to a suppressor tRNA. A positive selection system consists of chloramphenicol acetyl transferase gene containing an amber mutation at the $27^{th}$ residue, and efficiently concentrated amber suppressible ARS with a maximum enrichment factor of $9.0{\times}10^5$. On the other hand, a negative selection system was constructed by adding multiple amber codons in front of a lethal gene encoding the control of cell death B toxin (ccdB) which acts as an inhibitory protein of bacterial topoisomerase II. Amber suppression of ccdB by an orthogonal pair of Saccharomyces cerevisiae tyrosyl-tRNA synthetase (TyrRS) and an amber suppressor tRNA significantly inhibits bacterial growth. This selection system was also able to efficiently remove amber suppressible ARS which could ligate natural amino acids to the suppressor tRNA. Thus, sequential combination of these two selection systems might be able to function as a powerful tool for selecting an ARS variant that specifically ligates an unnatural amino acid to the suppressor tRNA from an ARS mutant pool.