• Journal of Microbiology and Biotechnology
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• v.19 no.3
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• pp.299-306
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• 2009

Dissolved oxygen (DO) has a significant effect on the molecular weight of hyaluronic acid (HA) during the fermentation of Streptococcus zooepidemicus. Therefore, to further investigate the effect of DO on the yield and molecular weight of HA, this study compared the metabolic flux distribution of S. zooepidemicus under aerobic conditions at various DO levels. The metabolic flux analysis demonstrated that the HA synthesis pathway, considered a dependent network, was little affected by the DO level. In contrast, the fluxes of lactate and acetate were greatly influenced, and more ATP was generated concomitant with acetate at a high DO level. Furthermore, the has gene expression and HA synthase activity were both repressed under anaerobic conditions, yet not obviously affected under aerobic conditions at various DO levels. Therefore, it was concluded that the HA molecular weight would seem to depend on the concomitant effect of the generation of ATP and reactive oxygen species. It is expected that this work will contribute to a better understanding of the effect of the DO level on the mechanism of the elongation of HA chains.

• Proceedings of the Korea Crystallographic Association Conference
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• 2000.11a
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• pp.8-8
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• 2000

• BMB Reports
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• v.42 no.1
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• pp.41-46
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• 2009

Post-transcriptional regulation of mRNA stability by Hu proteins is an important mechanism for tumorigenesis. We focused on the molecular interactions between the HuC protein and AU-rich elements (AREs) to find chemical inhibitors of RNA-protein interactions using RNA electrophoretic mobility shift assay with non-radioactive probes. Screening of 52 natural compounds identified 14 candidate compounds that displayed potent inhibitory activity. Six (quercetin, myricetin, (-)-epigallocatechin gallate, ellagic acid, (-)-epicatechin gallate, and rhamnetin) were categorized as phytochemicals, and their $IC_{50}$ values were low ($0.2-1.8\;{\mu}M$).

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.8
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• pp.932-938
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• 2007

The interaction between adherent molecules and gas molecules was modeled in molecular scale and simulated by the molecular dynamics method in order to understand the evaporation and removal processes of adherent molecules on metallic surface using high temperature gas flow. Methanol molecules were chosen as adherent molecules to investigate effects of adhesion quantify and gas molecular collisions because the industrial oil has too complex structures of fatty acid. The effects of adherent quantify, gas temperature and surface temperature for the evaporation rate of adherent molecules and the molecular removal mechanism were investigated and discussed in the present study. Evaporation and removal rates of adherent molecules from metallic surface calculated by the molecular dynamics method showed the similar dependence on surface temperature shown in the experimental results.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.24-24
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• 2002

HtrA (high temperature requirement A), a periplasmic heat shock protein, is known to have molecular chaperone function at low temperatures and proteolytic activity at elevated temperatures. To investigate the mechanism of functional switch to pretense, we have determined the crystal structure of the N-terminal protease domain (PD) of HtrA from Thermotoga maritima. HtrA PD shares the same fold with chymotrypsin-like serine professes. However, crystal structure suggests that HtrA PD is not an active pretense at current state since its active site is not formed properly and blocked by an additional helical lid. On the surface of the lid, HtrA PD has hydrophobic patches that could be potential substrate binding sites for molecular chaperone activity. Present structure suggests that the activation of the proteolytic function of HtrA PD at elevated temperatures might occur by the conformational change.

• Korean Journal of Plant Tissue Culture
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• v.27 no.4
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• pp.259-268
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• 2000

Senescence is a sequence of biochemical and physiological events that lead to death of a cell, organ, or whole organism. Senescence is now clearly regarded as a genetically determined and evolutionarilly acquired developmental process comprising the final stage of development. However, in spite of the biological and practical importance, genetic mechanism of senescence has been very limited. Through forward and reverse genetic approaches, we are trying to reveal the molecular and genetic mechanism of senescence in plants, employing leaf organs of Arabidopsis as a model system. Using forward genetic approach, we have initially isolated several delayed senescence mutants either from T-DNA insertional lines or chemical-mutagenized lines. In the case of ore 4 and ore 9 mutants, the mutated genes were identified. The recent progress on characterization of mutants and identification of the mutated genes will be reported. We are also screening mutations from other various sources of mutant pools, such as activation tagging lines and promoter trap lines. Two dominant senescence-delayed mutants were isolated from the activation tagging pool. Cloning of the genes responsible for this phenotype is in progress. For reverse genetic approach, the genes that induced during leaf senescence were first isolated by differential screening method. We are currently using PCR-based suppression subtractive hybridization, designed to enrich a cDNA library for rare differentially expressed transcripts. Using this method, we have identified over 35 new sequences that are upregulated at leaf senescence stage. We are investigating the function of these novel genes by systemically generating antisense lines.

• Journal of Energy Engineering
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• v.18 no.2
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• pp.125-131
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• 2009

Physical characteristics of metals such as hardness, wear-resistance and corrosion-resistance can be artificially controlled by ion implantation. The interaction between ion and solid surface was modeled in molecular scale and simulated by the molecular dynamics method in order to understand the ion implantation mechanism. From the microscopic point of view, the molecular behaviors were observed for improving characteristics of ion implantation. For these purposes, the implantation mechanism and the influences of incident energy, surface temperature and molecular weight were discussed in this study. As the results, the penetration probability was even decreased if incident energy was exceeded any values in the case of high temperature of solid surface. Moreover, it was confirmed that ion implantation into solid surface with amorphous state could be more effective for some conditions.

• Journal of Ginseng Research
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• v.43 no.4
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• pp.666-675
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• 2019

Background: Korean Red Ginseng (KRG) has been widely used as an herbal medicine to normalize and strengthen body functions. Although many researchers have focused on the biological effects of KRG, more studies on the action mechanism of red ginseng are still needed. Previously, we investigated the proteomic changes of the rat spleen while searching for molecular signatures and the action mechanism of KRG. The proteomic analysis revealed that differentially expressed proteins (DEPs) were involved in the increased immune response and phagocytosis. The aim of this study was to evaluate the biological activities of KRG, especially the immune-enhancing response of KRG. Methods: Rats were divided into 4 groups: 0 (control group), 500, 1000, and 2000 mg/kg administration of KRG powder for 6 weeks, respectively. Isobaric tags for relative and absolute quantitation was performed with Q-Exactive LC-MS/MS to compare associated proteins between the groups. The putative DEPs were identified by a current UniProt rat protein database search and by the Gene Ontology annotations. Results: The DEPs appear to increase the innate and acquired immunity as well as immune cell movement. These results suggest that KRG can stimulate immune responses. This analysis refined our targets of interest to include the potential functions of KRG. Furthermore, we validated the potential molecular targets of the functions, representatively LCN2, CRAMP, and HLA-DQB1, by Western blotting. Conclusion: These results may provide molecular signature candidates to elucidate the mechanisms of the immune response by KRG. Here, we demonstrate a strategy of tissue proteomics for the discovery of the molecular function of KRG.

• Journal of Life Science
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• v.9 no.1
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• pp.22-25
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• 1999

In order to study the mechanism for the adaptation to salt stress, we mutagenized budding yeast Saccharomyces cerevisiae with Ethylmethane sulfonate, and isolated salt-tolerant mutants. Among the salt-tolerant mutants, two strains exhibit additional temperature sensitive phenotype. Here, we report that these two salt-tolerant mutants are specific to {TEX}$Na^{+}${/TEX} rather than general osmotic stress. These mutant strains may contain mutations in the genes involved in {TEX}$Na^{+}${/TEX} home-ostasis.

• Bulletin of the Korean Chemical Society
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• v.24 no.10
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• pp.1509-1511
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• 2003