• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.2
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• pp.64-75
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• 2003

Aptamers are functional nucleic acids that can specially bind to proteins, peptides, amino acids. nucleotides, drugs, vitamins and other organic and inorganic compounds. The aptamers are identified from random DNA or RNA libraries by a SELEX (systematic evolution of ligands by exponential amplification) process. As aptamers have the advantage, and potential ability to be released from the limitations of antibodies, they are attractive to a wide range of therapeutic and diagnostic applications. Aptamers, with a high-affinity and specificity, could fulfil molecular the recognition needs of various fields in biotechnology. In this work, we reviewed some aptamer Selection techniques, properties, medical applications of their molecules and their biotechnological applications, such as ELONA (enzyme linked oligonucleotide assay), flow cytometry, biosensors, electrophoresis, chromatography and microarrays.

• BMB Reports
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• v.33 no.6
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• pp.476-482
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• 2000

In this paper, we report a new cationic lipid composed of L-lysinamide and cholesterol as a potent gene delivery vector. $3{\beta}$[L-Lysinamide-carbamoyl] cholesterol could self-assemble with plasmid DNA forming discrete lipoplexes. From atomic force microscopic images of the complexes, the size distribution was observed to range from 100 to 150 nm in diameter. The transfection efficiency of this amphiphile on different cell lines was evaluated as a micellar solution in the absence of the fusogenic helper lipid, dioleoyl phosphatidyletbanolamine (DOPE). Transfection experiments were performed as a function of charge ratio (lipid/DNA) and transfection time. Cytotoxicity and in vitro transfection efficiency of the amphiphile was demonstrated and compared with those of commercially available Lipofectin and polyethylenimine (PEI).

• Polymer(Korea)
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• v.39 no.3
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• pp.388-393
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• 2015

Low molecular weight species were extracted from PC and SAN by a solvent extraction method in order to investigate the effect of low molecular weight species on interfacial tension and affinity between PC and SAN. From the analysis of molecular weight distribution by the GPC, it was confirmed that the low molecular weight species were effectively eliminated by the solvent extraction. Interfacial tension measurements and morphological observation were carried out with the PC and SAN of which the low molecular weight species were extracted. Interfacial tension was increased and the infinity was decreased for the extracted PC and SAN pair. This result implied that the low molecular weight species play a role as a compatibilizer between two polymers. Among two polymers, low molecular weight SAN contributes more in the compatibilization. Thus, it is favorable to use SAN containing a larger amount of low molecular weight species in fabrication of PC/ABS blend.

• Journal of Microbiology and Biotechnology
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• v.16 no.11
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• pp.1832-1836
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• 2006

Mesorhizobium sp. LUK, which utilizes 3-amino-3-phenylpropionic acid as the sole source of nitrogen with high enantioselectivity (E(S)>100), was isolated using enrichment culture. The enzyme involved in the utilization of (S)-3-amino-3-phenylpropionic acid was confirmed to be a transaminase and was purified by 235-folds with a specific activity of 0.72 U/mg. The molecular weight of the purified protein was ca. 47 kDa and the active enzyme was determined as a dimer on gel filtration chromatography. The N-terminal sequence was obtained from the purified protein. Spontaneous decarboxylation of produced ${\beta}-keto$ acids was observed during the chiral resolution of 3-amino-3-phenylpropionic acid.

• Journal of Microbiology and Biotechnology
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• v.17 no.7
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• pp.1098-1105
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• 2007

Quantum mechanical and molecular dynamics simulation analysis has been performed on the model system for CALB (Candida antarctica lipase B) with esters to study the reaction mechanism and conformational preference of catalytic hydrolysis and the esterification reaction. Using quantum mechanical analysis, the ping-pong bi-bi mechanism was applied and energies and 3-dimensional binding configurations of the whole reaction pathways were calculated. Further molecular dynamics simulation analysis was performed on the basis of the transition state obtained from quantum mechanical study to observe the effect of structures of the substrates. Calculation results using substrates of different chain length and chiral configurations were compared for conformational preference. The calculated results showed very small influence on chain length, whereas chiral conformation showed big differences. Calculated results from molecular modeling studies have been compared qualitatively with the experimental data using racemic mixtures of (${\pm}$)-cis-4-acetamido-cyclopent-2-ene-1-ethyl acetate as substrates.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.343-348
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• 2018

Each of the two polycarbonates (PC) of different molecular weights was blended with acrylonitrile-butadiene-styrene (ABS) under high-shear rate processing to afford PC/ABS. Sizes of ABS dispersed phases and mechanical properties of PC/ABS blends were investigated and high-shear rate processing of PC/ABS was carried out by changing screw speed and processing time. Prepared specimens were examined by scanning electron microscope (SEM) to observe morphology changes. Sizes of ABS dispersed phases in PC/ABS blends were observed to decrease gradually as screw speeds increased. Tensile strengths and elongations of specimens were investigated by universal testing method (UTM) to study the influence of molecular weight of PC exerting on PC/ABS blends. As a result, PC1/ABS blends (PC1: higher molecular weight PC) exhibited more strengthened properties than PC2/ABS (PC2: lower molecular weight PC). The tensile strength of PC1/ABS showed an increasing tendency when the screw speed increased, and the elongation did not show a significant decrease, but increased slightly with increasing shear time at a constant screw speed of 1000 rpm.

• Molecules and Cells
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• v.19 no.3
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• pp.334-341
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• 2005

Plants are sessile and rely on a wide variety of growth hormones to adjust growth and development in response to internal and external stimuli. We have identified a gene, designated NAN, encoding a basic helix-loop-helix (bHLH) transcription factor that regulates cell elongation and seed germination in plants. NAN has an HLH motif in its C-terminal region but does not have any other discernible homologies to bHLH proteins. A bipartite nuclear localization signal is located close to the HLH motif. An Arabidopsis mutant, nan-1D, in which NAN is activated by the insertion of the 35S enhancer, exhibits growth retardation with short hypocotyls and curled leaves. It is also characterized by reduced seed germination and apical hook formation, symptomatic of GA deficiency or disrupted GA signaling. The phenotypic effects of nan-1D were increased by treatment with paclobutrazol (PAC), an inhibitor of gibberellic acid (GA) biosynthesis. NAN is constitutively expressed throughout the life cycle. Our observations indicate that NAN has a housekeeping role in plant growth and development, particularly in seed germination and cell elongation, and that it may modulate GA signaling.

• BMB Reports
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• v.38 no.3
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• pp.290-293
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• 2005

In order to investigate the epitope of basic fibroblast growth factor (bFGF) and its immunogenicity, the epitopes of bFGF were screened from the phage display library with monoclonal antibody GF22, which can neutralize the bio-activity of bFGF. By three rounds of screening, the positive phage clones with bFGF epitopes were selected, which can effectively block the bFGF to bind with GF22. Sequence analysis showed that the epitopes shared a highly conservative sequence (Leu-Pro-Pro/Leu-Gly-His-Phe/Ile-Lys). The sequence of PPGHFK was located at 22-27 of the bFGF. The specific immuno-response of mouse could be highly induced by phage clones with the epitopes. And the anti-bFGF activity induced by LPGHFK was 3 times higher than the original sequence, which showed that the mimetic peptide LPLGHIK might be used as a tumor vaccine in the prevention and treatment of tumor.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.640-641
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• 2003

• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.9-13
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• 2016

Electrospun poly(ether sulfone) (PES) membrane impregnated with Nafion (PES-N) have been developed for high-temperature polymer-electrolyte membrane fuel cell (HT-PEMFC). The PES-N obtains highly thermal stability up to $430^{\circ}C$, which is higher than that of the commercial Nafion 212. The PES-N membrane shows a good proton conductivity of about $10^{-2}S\;cm^{-1}$ in a temperature range from $75^{\circ}C$ to $120^{\circ}C$. The membrane-electrode assembly (MEA) with the PES-N membrane exhibits a current density of $1.697A\;cm^{-2}$ at $75^{\circ}C$, and $0.813A\;cm^{-2}$ at $110^{\circ}C$ when the applied voltage is 0.6 V, whereas the MEA with the Nafion 212 membrane shows the current density of $0.647Acm^{-2}$ at $110^{\circ}C$. The results suggest that the PES-N can be a good candidate for a polymer electrolyte membrane of the HT-PEMFC.