• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.915-920
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• 2008

In this paper the electrochemical behaviors of hydroquinone ($H_2Q$) were investigated on a carbon paste electrode using room temperature ionic liquid N-butylpyridinium hexafluorophosphate ($BPPF_6$) as binder (ILCPE) and further applied to $H_2Q$ determination. In pH 2.5 phosphate buffer solution (PBS), the electrochemical response of H2Q was greatly improved on the IL-CPE with a pair of well-defined quasi-reversible redox peaks appeared, which was attributed to the electrocatalytic activity of IL-CPE to the $H_2Q$. The redox peak potentials were located at 0.340 V (Epa) and 0.240 V (Epc) (vs. the saturated calomel electrode, SCE), respectively. The formal potential ($E^0$') was calculated as 0.290 V and the peak-to-peak separation (${\Delta}E_p$) was 0.100 V. The electrochemical parameters of $H_2Q$ on the IL-CPE were further calculated by cyclic voltammetry. Under the selected conditions the anodic peak current was linear with $H_2Q$ concentration over the range from $5.0\;{{\times}}\;10^{-6}$ to $5.0\;{\times}\;10^{-3}\;mol\;L^{-1}$ with the detection limit as $2.5\;{\times}\;10^{-6}\;mol\;L^{-1}$ (3$\sigma$ ) by cyclic voltammetry. The proposed method was successful applied to determination of $H_2Q$ content in a synthetic wastewater sample without the interferences of commonly coexisting substances.

• Analytical Science and Technology
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• v.9 no.3
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• pp.235-243
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• 1996

A carbon paste electrode were chemically modified using ${\alpha}$-cyclodextrin. Characteristics of chemically modified carbon paste electrodes were studied on the basis of the inclusion complex formation of ${\alpha}$-cyclodextrin and p-nitrophenol in solution. Cyclic voltammetry and differential pulse voltammetry were used to monitor the efficiency of the chemical modification. When the ${\alpha}$-cyclodextrin and carbon powder ratio of 2 : 1 in weight were used, the reduction peak current of p-nitrophenol was decreased almost completely, whereas those of o-nitrophenol and hydroquinone were not changed much. This result is due to the large difference in the inclusion complex formation constants of p-nitrophenol and the other probes with ${\alpha}$-cyclodextrin. Taking advantage of this difference, we can determine the concentration of o-nitrophenol even in the presence of p-nitrophenol.

• The Korean Journal of Physiology and Pharmacology
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• v.21 no.3
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• pp.345-352
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• 2017

Since previous studies have reported that hydroquinone (HQ) exerted immunosuppressive and anti-inflammatory activity, various HQ derivatives have been synthesized and their biological activities investigated. In this study, we explored the anti-inflammatory activity of JS-III-49, a novel HQ derivative, in macrophage-mediated inflammatory responses. JS-III-49 suppressed the production of the inflammatory mediators nitric oxide (NO) and prostaglandin $E_2$ ($PGE_2$) and down-regulated the mRNA expression of the inflammatory enzymes cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) as well as the expression of the pro-inflammatory cytokines interleukin-6 (IL-6) and IL-$1{\beta}$ without cytotoxicity in LPS-stimulated RAW264.7 cells. JS-III-49 inhibited nuclear translocation of the $NF-{\kappa}B$ transcription factors p65 and p50 by directly targeting Akt, an upstream kinase of the $NF-{\kappa}B$ pathway, in LPS-stimulated RAW264.7 cells. However, JS-III-49 did not directly inhibit the kinase activities of Src and Syk, which are upstream kinases of Akt, in LPS-stimulated RAW264.7 cells. Moreover, JS-III-49 suppressed the nuclear translocation of c-Fos, one of the components of AP-1, by specifically targeting p38, an upstream mitogen-activated protein kinase (MAPK) in the AP-1 pathway in LPS-stimulated RAW264.7 cells. These results suggest that JS-III-49 plays an anti-inflammatory role in LPS-stimulated macrophages by targeting Akt and p38 in the $NF-{\kappa}B$ and AP-1 pathways, respectively.

• Journal of the Korean Chemical Society
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• v.51 no.6
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• pp.585-590
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• 2007

• Journal of the Korean Electrochemical Society
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• v.6 no.2
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• pp.130-133
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• 2003

3,4-dihydroxybenzoic acid(3,4-DHBA) was electropolymerized on glassy carbon electrode to give the GC/p-3,4-DHBA type electrode which was modified with dopamine by the help of 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride(EDC) acting as a coupling agent. The carboxylic sites on the polymeric surface of p-3,4-DHBA and mine group at the dopamine gave a QCA(Au)/p-3,4-DHBA-dopamine type of modified electrodes. The o-quinone moieties at the electrode surface exhibited high selectivity to titanium ions in solution. The redox process of the electrode is hydroquinone : quinone +$2H^+2e^-$, which had two strong and two weak pairs of peaks at CV. The modified electrode can deposit Ti(IV) ions as much as $4.13\times10^{-5}gcm^{-2}$. The calibration curve of the electrodes, log of the surface coverage-normalized redox response vs log[Ti], exhibited an excellent correlation$(r{\geq}0.997)$ for titanium concentrations ranging from $5.25\times10^{-4}\;to\;5.25\tiems10^{-8}M.$.

• Radiation Oncology Journal
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• v.31 no.2
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• pp.57-65
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• 2013

Beta-lapachone (${\beta}$-Lap; 3,4-dihydro-2, 2-dimethyl-2H-naphthol[1, 2-b]pyran-5,6-dione) is a novel anti-cancer drug under phase I/II clinical trials. ${\beta}$-Lap has been demonstrated to cause apoptotic and necrotic death in a variety of human cancer cells in vitro and in vivo. The mechanisms underlying the ${\beta}$-Lap toxicity against cancer cells has been controversial. The most recent view is that ${\beta}$-Lap, which is a quinone compound, undergoes two-electron reduction to hydroquinone form utilizing NAD(P)H or NADH as electron source. This two-electron reduction of ${\beta}$-Lap is mediated by NAD(P)H:quinone oxidoreductase (NQO1), which is known to mediate the reduction of many quinone compounds. The hydroquinone forms of ${\beta}$-Lap then spontaneously oxidizes back to the original oxidized ${\beta}$-Lap, creating futile cycling between the oxidized and reduced forms of ${\beta}$-Lap. It is proposed that the futile recycling between oxidized and reduced forms of ${\beta}$-Lap leads to two distinct cell death pathways. First one is that the two-electron reduced ${\beta}$-Lap is converted first to one-electron reduced ${\beta}$-Lap, i.e., semiquinone ${\beta}$-Lap $(SQ)^{{\cdot}-}$ causing production of reactive oxygen species (ROS), which then causes apoptotic cell death. The second mechanism is that severe depletion of NAD(P)H and NADH as a result of futile cycling between the quinone and hydroquinone forms of ${\beta}$-Lap causes severe disturbance in cellular metabolism leading to apoptosis and necrosis. The relative importance of the aforementioned two mechanisms, i.e., generation of ROS or depletion of NAD(P)H/NADH, may vary depending on cell type and environment. Importantly, the NQO1 level in cancer cells has been found to be higher than that in normal cells indicating that ${\beta}$-Lap may be preferentially toxic to cancer cells relative to non-cancer cells. The cellular level of NQO1 has been found to be significantly increased by divergent physical and chemical stresses including ionizing radiation. Recent reports clearly demonstrated that ${\beta}$-Lap and ionizing radiation kill cancer cells in a synergistic manner. Indications are that irradiation of cancer cells causes long-lasting elevation of NQO1, thereby sensitizing the cells to ${\beta}$-Lap. In addition, ${\beta}$-Lap has been shown to inhibit the repair of sublethal radiation damage. Treating experimental tumors growing in the legs of mice with irradiation and intraperitoneal injection of ${\beta}$-Lap suppressed the growth of the tumors in a manner more than additive. Collectively, ${\beta}$-Lap is a potentially useful anti-cancer drug, particularly in combination with radiotherapy.

• Korean Journal of Crystallography
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• v.2 no.2
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• pp.13-21
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• 1991

X-ray methods have been used to determine the chain conformation and packing of the thermotropic liquid crystalline copolyester prepared from 50% tarephthaloyl chloride(TPA) and 50% (1-phenylethyl) hydroquinone(PEHQ). The x-ray patterns of annealed melt-spun fibers contain a series of annealed melt-Pointing to a well ordered crystalline structure, despite the random sense(2 or 3-) of the 1-phenylethyl substiuttion on the TPA-hydroquinone backbone. The crystalline fiber is monoclinic with space group P2l and the unit cell has dimensions 11=12.77 A, b=10.17 A (upique axis), c=12.58 h (fiber axis). and β=90.1° and contains TPA-PEHO units of to or chains. The random substitution of 1-phenylethyl groups was modelled by placing these groups at both the 2and 3 positions and giving each a weight of one-hal(. T he structure has been refined by linked a rom least square methods(LALS) against 16 observed and 21 unobserved reflections. and had a final R value of 0.20. Packing of the side chains is effected by staggering adjacent chains along the b axis by approximately c/2, so that the side chains are interleaved. The phenyl-COO and COO-phenyl torsion angles are -6.1 and 65.6, respectively, such that the main chain phenyls are mutually inclined at 59.5 (the ester groups are assumed to be planar). These torsion angles compare very well with those for the model compounds, notably phenylbenzoate, and can be used in future analyses of the structures of more complex random sequence copolyesters.

• Polymer(Korea)
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• v.25 no.6
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• pp.782-788
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• 2001

The $[Ru(v-bpy)_3]^{2+}$ and vinylbenzoic acid (vba) were electrochemically copolymerized to afford electrodes modified with dopamine to study their properties such as electropolymerization rate, redox process, and electron transfer. The optimum mole ratio of the monomers was 5:2, which gave $1.84{ imes}10^{-2}s^{-1}$ of rate constant for first order reaction, while the ratio of the substances on the copolymeric film produced was 5:1.68. The formal potential produced from the hydroquinone=quinone+$2H^+2e^-$reaction at the electrode of GC/p- $[Ru(v-bpy)_3]^{2+}$/vba-dopamine was 0.17 V in phosphate buffer (pH=7.10). The electrocatalytic rate was $2.58{ imes}10^5cms^{-1}$;2.41 times faster than that of non-modified one. The mass change measured by EQCM was $3.28{ imes}10^3$$gmol^{-1}$ which is larger than that of non-modified one.

• Korean Journal of Food Science and Technology
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• v.22 no.6
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• pp.618-624
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• 1990

The antimutagenic effects of apple enzymatic browning reaction products(AEBRP) which resulted from the reaction of catechol, hydroquinone, homocatechol, hydroxyhydroquinone and pyrogallol with polyphenol oxidase extracted from apple(Jona gold) were investigated. Test strain used in SOS spot test and SOS chromotest was E. coli PQ 37/plasmid pKM 101. In SOS spot test, all of five AEBRPs showed strong antimutagenic effects on mytomycin C(MMC), 4-nitroquinoline-1-oxide(4NQO), N-me-thyl-N'-nitro-N-nitrosoguanidlne(MNNG) as increasing concentrations of AEBRP solution. In SOS chromotest, most of AEBRPs also showed strong antimutagenic effects on MMC, MNNG, 4NQO and 3-amino-1,4-dimethyl-5H-pyrido(4,3-b)indole (Trp-P-1), as increasing concentration of AEBRP solution.

• Bulletin of the Korean Chemical Society
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• v.10 no.6
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• pp.509-514
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• 1989

Reactions of thianthrene cation radical perchlorate (1) with N-(p-methoxyphenyl)benzenesulphonamide (14) in acetonitrile at room temperature afforded various products : thianthrene (3), N-(p-hydroxyphenyl)benzenesulphonamide (16), benzenesulphonamide (18), hydroquinone (20); 5-(5-benzenesulphonamido-2-methoxyphenyl)-thia nthrenium perchlorate(21), 2-benzenesulphonamido-2'-hydroxy-5,5'-dimethoxy biphenyl(24), 2-benzenesulphonamido-2',5'-dihydroxy-5-methoxy -biphenyl(25), and a traceable amount of p-quinone(23). The formations of part of (3) and (21) can be explained by either disproportionation or half-regeneration mechanism but those of the remainders by diverse reactions of sulphonamidyl radical (27) derived from (14) (through single electron transfer, followed by deprotonation processes). Similar results were observed from the reaction with N-(p-methoxyphenyl)methanesulphonamide (15).