• Microbiology and Biotechnology Letters
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• v.25 no.3
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• pp.240-247
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• 1997

Bacillary is the most common form of H. pylori observed during human infection. However, it is known that the morphology change of H. pylori from bacillary to coccoid can be occurred with a response to the environmental stresses such as the nutrient depletion, accumulation of toxic metabolites, pH alteration, and exposure to antimicrobial agents. The coccoid form of H. pylori, which is viable but non-culturable in vitro, seems to be the major cause of antibiotic resistancy and high reinfectability of H. pylori. In this regard, we studied the environmental factors that can induce the morphological change in vitro of H. pylori, and the change of fatty acid composition of plasma membrane. The morphological change from bacillary to coccoid could be observed with the depletion of nutrients, pH variation and reactive oxygen species added in the culture media. This morphologic conversion was paralleled by a dramatic decrease in unsaturated fatty acids and an increase in saturated fattv acids of plasma membrane. The change in composition of membrane fatty acid seems to be a kind of protection mechanism of H. pylori against these environmental stresses.

• Journal of Microbiology and Biotechnology
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• v.22 no.12
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• pp.1597-1604
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• 2012

Genus Bacillus is a spore-forming bacterium that has unique properties in cell differentiation, allowing the forming of spores in stress conditions and activated in the vegetative cell, with suitable environments occurring during the life cycle acting as a trigger. Their habitat is mainly in soil; thus, many species of Bacillus are associated with plants as well as rhizosphere bacteria and endophytic bacteria. Signal transduction is the principal mechanism of interactions, both within the cell community and with the external environment, which provides the subsequent functions or properties for the cell. The antimicrobial compounds of Bacillus sp. are potentially useful products, which have been used in agriculture for the inhibition of phytopathogens, for the stimulation of plant growth, and in the food industry as probiotics. There are two systems for the synthesis of these substances: nonribosomal synthesis of cyclic lipopeptides (NRPS) and polyketides (PKS). For each group, the structures, properties, and genes of the main products are described. The different compounds described and the way in which they co-exist exhibit the relationship of Bacillus substances to plants, humans, and animals.

• Journal of Life Science
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• v.7 no.2
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• pp.149-159
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• 1997

Chitin, a linked polysaccharide composed of 2-acetamido-2-deoxy-$\beta$-D-glucopytanose residues, is distributed widely in nature. It has been utilized on various application field due to the development of chitin derivatives such as chitosan, partial deacetylated chitin, carboxylmethyl chitin, sulfated chitin, and so on. Chitin and chitosan have been recently interested in antitumor and antimicrobial activities, because of a powerful tumor inhibitory effect against experimental mouse tumors. Especially, the oligosaccharides obtained by partial degradation of them exhibited a remarkable antitumor effect against sarcoma 180, MM 48 and Meth Asolid tumors and antimetastatic effect against Lewis lung carcinoma in mice. This review describes on antitumor effects of chitin, chitosan and their oligosaccharides by their mechanism of action involving enhancement of immunological system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.4
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• pp.285-290
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• 2005

Mechanical properties of rubber mat are influenced by many factors such as compounding ingredients and states of cure, process of rubber, and fillers. Our study aim is to investigate influence of N-isopropyl-N'-chloro-P-phenylene diamine antioxidant on the thermal aging and ozone cracking. In this work, the degradation of antiblastic rubber mat was studied and suggested mechanism to involve two-types of degradation, thermal-aging and ozone-cracking both of which can be contained antioxidant or non-antioxidant.

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.134.1-134.1
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• 2003

Tempting to further understanding the biophysical mechanism of action of chlorhexidine, we examined effects of the antimicrobial agent(chlorhexidine digluconate) on rate of rotational mobility of liposomes of total lipids extracted from anaerobic bacterial outer membranes (Porphyromonas gingivalis outer membranes). (omitted)

• Asian-Australasian Journal of Animal Sciences
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• v.33 no.3
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• pp.373-381
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• 2020

There is a need for newer feed additives due to legal prohibition on inclusion of growth promoting antibiotics in livestock diets in several countries due to antimicrobial resistance. In this context, rare earth elements (REE) have gained attention among animal nutritionists as potential growth promoters. Currently, several studies have reported better weight gain, milk production, egg laying capacity and feed conversion efficiency among different breeds of farm animals following supplementation with REE, with however largely inconsistent results. Furthermore, REE supplementation has also shown to improve ruminal fibrolytic and proteolytic activities as well as flavor of meat with negligible residues in edible tissue, however the mechanism behind this action is still unclear. According to existing research, due to their poor absorption and similarity with calcium REE might exert their action locally on gut microbial populations within the gastrointestinal tract (GIT). Moreover, REE have also shown anti-inflammatory, anti-oxidative as well as immune stimulating effects. The present review aims to broaden the knowledge about use of REE as feed additives for livestock and sum up efficacy of REE supplementation on performance and health of animals by comparing the findings. Till date, researches with REE have shown properties that make them a promising, new and safe alternative feed additive but further exploration is recommended to optimize effects and clarify discrepancy of various results before practical proposals can be drafted.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3695-3702
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• 2013

A nickel(II) complex $[Ni(H_2biim)_2(H_2O)_2](ClO_4)_2{\cdot}H_2O$ (1) of biimidazole ligand has been synthesized and characterized (Where $H_2biim$ = 2,2'-biimidazole). The single crystal X-ray diffraction of the complex shows a dimeric structure with six coordinated psudo-octahedral geometry. The cyclic voltammograms of complex exhibited one quasireversible reduction wave ($E_{pc}=-0.61V$) and an irreversible oxidation wave ($E_{pa}=1.28V$) in DMF solution. The interaction of the complex with Calf-Thymus DNA (CT-DNA) has been investigated by absorption and fluorescence spectroscopy. The complex is an avid DNA binder with a binding constant value of $1.03{\times}10^5M^{-1}$. The results suggest that the nickel(II) complex bind to CT-DNA via intercalative mode and can quench the fluorescence intensity of EB bind to CT-DNA with $K_{app}$ value of $3.2{\times}10^5M^{-1}$. The complex also shown efficient oxidative cleavage of supercoiled pBR322 DNA in the presence of hydrogen peroxide as oxidizing agent. The DNA cleavage by complex in presence of quenchers; viz. DMSO, KI, $NaN_3$ and EDTA reveals that hydroxyl radical or singlet oxygen mechanism is involved. The complex showed invitro antimicrobial activity against four bacteria and two fungi. The antimicrobial activity was nearer to that of standard drugs and greater than that of the free ligand.

• Biomedical Science Letters
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• v.24 no.1
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• pp.30-34
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• 2018

Silver (Ag) has been widely used in commercial products and medical fields since ancient times because of its antibacterial effect. It is harmless and non-toxic to the human body. For this reason, recent research has actively evaluated antimicrobial activity using silver (Ag). In this study, we investigated the inhibitory effect of a silver-based compound, silver phosphate ($Ag_3PO_4$) on the growth of Staphylococcus aureus and the activation of human immunity. First, the inhibitory effect of $Ag_3PO_4$ on the growth of Staphylococcus aureus was confirmed by a growth curve and a colonyounting method. As a result, the growth inhibitory effect increased as the concentration of $Ag_3PO_4$ increased. Specifically, treatment with $5{\mu}g/mL$ of $Ag_3PO_4$ resulted in no bacteria growth, and the colony-counting method showed a remarkable inhibition. In addition, the expression of cytokine IL-8 by $Ag_3PO_4$ was examined to investigate the cellular immune system activation by $Ag_3PO_4$. After pretreatment of Staphylococcus aureus for 1 hour with $50{\mu}g/mL$ $Ag_3PO_4$, an increased IL-8 mRNA expression resulted. In cells treated with $Ag_3PO_4$, we found that the expression of IL-8 was enhanced in a time-dependent fashion compared to non-treated cells. These results indicate that $Ag_3PO_4$ induces antimicrobial activity against Staphylococcus aureus and activates human immunity. These results are expected to contribute to the future study of the mechanism of silver (Ag) and silver-based compounds in relation to antibacterial activity.

• Journal of Korean Medicine Rehabilitation
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• v.30 no.1
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• pp.31-45
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• 2020

Objectives In this study, we investigated the antimicrobial activity of a 70% ethanol extract of Maneung-hwan (MEH), which is prescribed by practitioners of oriental medicine for use against methicillin-resistant Staphylococcus aureus (MRSA). Methods The antibacterial activity of MEH against MRSA strains was evaluated using the disc diffusion method, broth microdilution method (minimal inhibitory concentration, MIC), checkerboard dilution test, and time-kill test. The mechanism of action of MEH was investigated by bacteriolysis using detergents or ATPase inhibitors Additionally, mRNA and protein expression were investigated by quantitative reverse transcription-polymerase chain reaction and western blot assay, respectively. Results The MIC of MEH was 25~1,600 ㎍/mL against all the tested bacterial strains. We showed that MEH extract exerts strong antibacterial activity. In the checkerboard dilution test, the fractional inhibitory concentration index of MEH in combination with antibiotics indicated synergism or partial synergism against S. aureus. The time-kill study indicated that the growth of the tested bacteria was considerably inhibited after a 24-h treatment with MEH and selected antibiotics. To measure the cell membrane permeability, MEH (3.9 ㎍/mL) was combined with Triton X-100 (TX) at various concentrations N,N-dicyclohexylcarbodimide (DCCD) was also tested as an ATPase inhibitor. TX and DCCD cooperation against S. aureus exhibited synergistic action. Accordingly, the antimicrobial activity of MEH in the context of cell membrane rupture and ATPase inhibition was assessed. Additionally, the expression of genes and proteins associated with resistance was reduced after exposing MRSA to MEH. Conclusions These results suggest that MEH possesses antibacterial activity and acts as a potential natural antibiotic against MRSA.

• Journal of fish pathology
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• v.9 no.1
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• pp.65-77
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• 1996

Tachyplesin I is an antimicrobial peptide isolated from horseshoe crab. To investigate the mechanism of action of tachyplesin I for phospholipid bilayers, tachyplesin I and five analogs have been synthesized by the solution method. The synthesized five analogs are [$Phe^2$]-tachyplesin I, [$Phe^{8,13}$]-tachyplesin I, [$Cys(Acm)^{3,7,12,16}$]-tachyplesin I with no disulfide bonds, 7(Acm) and 10 (Acm) which denote the fragments [$Cys(Acm)^{3,7,12,16}$]-tachyplesin I. Circular dichroism spectra showed that tachyplesin I took an antiparallel $\beta$-structure in buffer solution and a less ordered structure in acidic liposomes. The carboxyfluorescein leakage experiment indicated that tachyplesin I interacted strongly with neutral and acidic phospholipid bilayers. In fluorescence experiment, the hydrophobic part of the peptide was shown to be embedded in lipid bilayers. All the peptides except for 7(Acm) and 10(Acm) were almost equally active in lipopolysaccharide binding. Therefore, the present study suggested that phospholipid bilayers induced a conformational change of tachyplesin I from the stable $\beta$-structure to a less ordered one.