• Bulletin of the Korean Chemical Society
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• 제24권4호
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• pp.437-440
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• 2003

In a mediator-aided microbial fuel cell, the choice of a proper mediator is one of the most important factors for the development of a better fuel cell system as it transfers electrons from bacteria to the electrode. The electrochemical behaviors within the lipid layer of two representative mediators, thionin and safranine O both of which exhibit reversible electron transfer reactions, were compared with the fuel cell efficiency. Thionin was found to be much more effective than safranine O though it has lower negative formal potential. Cyclic voltammetric and fluorescence spectroscopic analyses indicated that both mediators easily penetrated the lipid layer to pick up the electrons produced inside bacteria. While thionin could pass through the lipid layer, the gradual accumulation of safranine O was observed within the layer. This restricted dynamic behavior of safranine O led to the poor fuel cell operation despite its good negative formal potential.

• Bulletin of the Korean Chemical Society
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• 제32권5호
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• pp.1645-1649
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• 2011

[ ${\beta}$ ]Ketoacyl acyl carrier protein synthase I (KAS I) is involved in the elongation of unsaturated fatty acids in bacterial fatty acid synthesis and a therapeutic target of designing novel antibiotics. In this study, we performed receptor-oriented pharmacophore-based in silico screening of E. coli KAS I (ecKAS I) with the aim of identifying novel inhibitors. We determined one pharmacophore map and selected 8 compounds as candidates ecKAS I inhibitors. We discovered one antimicrobial compound, YKAe1008, N-(3-pyridinyl) hexanamide, displaying minimal inhibitory concentration (MIC) values in the range of 128-256 ${\mu}g/mL$ against MRSA and VREF. YKAe1008 was subsequently assessed for binding to ecKAS I using saturation-transfer difference NMR spectroscopy. Further optimization of this compound will be carried out to improve its antimicrobial activity and membrane permeability against bacterial cell membrane.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1897-1901
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• 2010

Multi-wall carbon nanotube (MWNT)-modified glassy carbon electrodes (GCE) were prepared for simultaneous determination of rutin and quercetin. Microbial carbohydrates, $\alpha$-cyclosophorohexadecaose ($\alpha$-C16) and succinoglycan monomer M3 (M3) were doped into MWNTs to prepare a $\alpha$-C16-doped MWNT-modified GCE (($\alpha$-C16 + MWNTs)/GCE) and a M3-doped MWNT-modified GCE ((M3 + MWNTs)/GCE), respectively. The sensitivities of the ($\alpha$-C16 + MWNTs)/GCE to rutin and quercetin were 34.7 ${\mu}A\cdot{\mu}M^{-1}{\cdot}cm^{-2}$ and 18.3 ${\mu}A\cdot{\mu}M^{-1}{\cdot}cm^{-2}$, respectively, in a linear range of $2\sim8{\mu}M$ at pH 7.2. The sensitivities of the (M3 + MWNTs)/GCE was 2.44 ${\mu}A\cdot{\mu}M^{-1}{\cdot}cm^{-2}$ for rutin and 7.19 ${\mu}A\cdot{\mu}M^{-1}{\cdot}cm^{-2}$ for quercetin without interference.

• Bulletin of the Korean Chemical Society
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• 제34권9호
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• pp.2629-2634
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• 2013

Fisetin is a naturally occurring flavonoid with some anti-cancer and anti-inflammation capabilities. In this study, we perform docking studies between human c-Jun N-terminal kinase 1 (JNK 1) and fisetin and proposed a binding model of fisetin and JNK 1, in which the hydroxyl groups of the B ring and oxygen at the 4-position of the C ring play key roles in binding interactions with JNK. Fluorescence quenching and saturation-transfer difference (STD) NMR experiments showed that fisetin exhibits good binding affinity to JNK, $1.32{\times}10^8M^{-1}$. The anti-inflammatory activity of fisetin was also investigated. Fisetin significantly suppressed tumor necrosis factor, the NO production, and macrophage inflammatory cytokine release in LPS-stimulated RAW264.7 mouse macrophages. We found that the anti-inflammatory cascade of fisetin was mediated through the JNK, and cyclooxygenase (COX)-2 pathways. Our findings suggest the potential of fisetin as an anti-inflammatory agent.

• Journal of Microbiology and Biotechnology
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• 제19권12호
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• pp.1612-1616
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• 2009

Isoflavonoids are a class of phytoestrogens. Isoflavonone synthase (IFS) is responsible for the conversion of naringenin to genistein. IFS is a cytochrome P450 (CYP), and requires cytochrome P450 reductase (CPR) for its activity. Additionally, the majority of cytochrome P450s harbor a membrane binding domain, making them difficult to express in Escherichia coli. In order to resolve these issues, we constructed an inframe fusion of the IFS from red clover (RCIFS) and CPR from rice (RCPR) after removing the membrane binding domain from RCIFS and RCPR. The resultant fusion gene, RCIFS-RCPR, was expressed in E. coli. The conversion of naringenin into genistein was confirmed using this E. coli transformant. Following the optimization of the medium and cell density for biotransformation, $60\;{\mu}M$ of genistein could be generated from $80\;{\mu}M$ of naringenin. This fusion protein approach may be applicable to the expression of other P450s in E. coli.

• Journal of Applied Biological Chemistry
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• 제48권3호
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• pp.127-132
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• 2005

MYB genes, comprising group of related genes found in animal, plant, and fungal genomes, encode common DNA-binding domains composed of one to four repeat motifs. MYB genes containing two repeats (R2R3) constitute largest MYB gene family in plants. R2R3 MYB genes play important roles in regulation of secondary metabolism, control of cell shape, disease resistance, and hormone response. Eight-four R2R3 MYB genes were retrieved from rice genome for functional characterization of MYB genes. Analysis of MYB domains revealed each MYB domain contains three ${\alpha}$-helices with regularly spaced tryptophan residues. R2R3 MYB genes were divided into four subfamilies based on phylogenic analysis result. Real-time PCR analysis of 34 MYB genes revealed 12 MYB genes were highly expressed in seeds than in leaves, whereas 4 genes were highly expressed in leaves.

• Journal of Applied Biological Chemistry
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• 제48권1호
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• pp.7-10
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• 2005

Trichoderma sp. SY most effectively produces an extracellular ${\gamma}$-L-arabinofuranosidase (AF) using arabinose as a carbon source. AF grown on cellulose as a carbon source was purified 28-fold with 4.4% yield by DEAE exchange and HQ/20 cation exchange chromatographies The purified enzyme was found to be homogeneous on SDS-PAGE with molecular weight of 89 kDa. It exhibited a high level of activity with p-nitrophenyl ${\alpha}$-L-arabinofuranoside, showing $K_m$ and $V_{max}$ values of $0.15\;{\mu}M$ and $239.85U{\cdot}mg^{-1}$, respectively and did not require any metal ion for activity. It also released p-nitrophenol from p-nitrophenol conjugated ${\beta}$-D-xylopyranoside, and ${\beta}$-D-galactopyranoside not from ${\beta}$-D-glucopyranoside.

• Bulletin of the Korean Chemical Society
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• 제35권11호
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• pp.3169-3174
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• 2014

Numerous studies have examined the role of flavonoids in modulating inflammatory responses in vitro. In this study, we found a novel flavonoid, 3,6,3'-trihydroxyflavone (1), with anti-inflammatory effects. Anti-inflammatory activity and mechanism of action were examined in mouse macrophages stimulated with lipopolysaccharide (LPS). Our results showed that the anti-inflammatory effects of 1 are mediated via p38 mitogen-activated protein kinase (p38 MAPK), Jun-N terminal kinase (JNK), and the extracellular-signal-regulated kinase (ERK) pathway in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Binding studies revealed that 1 had a high binding affinity to JNK1 ($1.568{\times}10^8M^{-1}$) and that the 3- and 6-hydroxyl groups of the C-ring and A-ring of 1 participated in hydrogen bonding interactions with the side chains of Asn114 and Lys55, respectively. The oxygen at the 3' position of the B-ring formed a hydrogen bond with side chain of Met111. Therefore, 1 could be a potential inhibitor of JNKs, with potent anti-inflammatory activity.

• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3219-3222
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• 2011

Three types of ${\beta}$-ketoacyl acyl carrier protein synthase (KAS) are important for overcoming the bacterial resistance problem. Recently, we reported the discovery of a antimicrobial flavonoid, YKAF01 (3,6-dihydroxyflavone), which exhibits antibacterial activity against Gram-positive bacteria through inhibition of ${\beta}$-ketoacyl acyl carrier protein synthase III (KAS III). In this report, we suggested that YKAF01 can be an inhibitor ${\beta}$-ketoacyl acyl carrier protein synthase I (KAS I) with dual inhibitory activity for KAS I as well as KAS III. KAS I is related to the elongation of unsaturated fatty acids in bacterial fatty acid synthesis and can be a good therapeutic target of designing novel antibiotics. We performed docking study of Escherichia coli KAS I (ecKAS I) and YKAF01, and determined their binding model. YKAF01 binds to KAS I with high binding affinity ($2.12{\times}10^6$) and exhibited an antimicrobial activity against the multidrug-resistant E. coli with minimal inhibitory concentration (MIC) value of 512 ${\mu}g$/mL. Further optimization of this compound will be carried out to improve its antimicrobial activity and membrane permeability against bacterial cell membrane.

• 한국축산식품학회지
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• 제31권6호
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• pp.899-906
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• 2011

The objectives of this study were to apply the Baranyi model to predict the growth of natural microflora in liver sausage with added kimchi powder. Kimchi powder was added to the meat products at 0, 1, 2, and 3% levels. To determine and quantify the natural microflora in the meat products, total plate counts and counts of anaerobic bacteria and lactic acid bacteria were examined throughout the 28 d of storage. The obtained data were applied to the Baranyi growth model. The indices used for comparing predicted and observed data were $B_f$, $A_f$, root mean square error (RMSE), and $R^2$. Twelve predictive models were characterized by a high $R^2$ and small RMSE. The Baranyi model was useful in predicting natural microflora levels in these meat products with added kimchi powder during storage.