• Food Science and Biotechnology
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• 제17권6호
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• pp.1332-1336
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• 2008

The water extract of Saururus chinensis was investigated for oxygen radical absorbance capacity (ORAC), reducing capacity, metal chelating activity, and intracellular antioxidant activity using HepG2 cell. When 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) was used for the generation of peroxyl radicals in vitro, S. chinensis extract (SC-E) showed the strong and concentration-dependent scavenging activity through donating protons which could be explained by its reducing property. When hydroxyl radicals were generated in vitro through the addition of $Cu^{2+}$ and $H_2O_2$, SC-E demonstrated the antioxidant activity depending on its concentration. In HepG2 cell model, most of intracellular oxidative stress generated by AAPH was efficiently removed by SC-E. However, when $Cu^{2+}$ without $H_2O_2$ was used as an oxidant in the intracellular assay, SC-E partially reduced the oxidative stress caused by $Cu^{2+}$ in cellular antioxidant activity assay system. These results indicate that SC-E could be utilized for the development of functional foods as antioxidant resource in the near future.

• Bulletin of the Korean Chemical Society
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• 제15권11호
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• pp.967-971
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• 1994

The stability constants, log K of the 1 : 1 complexation for IA ions, $Ag^+$, and $Tl^+$ with a series of podands having different aromatic end-groups (I-IV) have been determined conductometrically in methanol at 25.0 $^{\circ}$C. Exceptionally the equivalent conductivity, ${\lambda}_{eq}\;of\;Li^+\;and\;Na^+$ were increased by the addition of I, because the complexed ions are less mobile than solvated ions. The order of log K values for I was $Ag^+{\gg}Tl^+>K^+>Na^+>Rb^+>Cs6+>Li^+$. The log K sequence of the podands for the certain cations was I>II>III${\geq}$IV. And every podands except IV showed the maximum selectivity for $Ag^+$ among the cations. These results were discussed in terms of the aromatic end-group effects, such as hetero-donor atoms or conformational changes by ${\pi}-{\pi}$ stacking interactions. The detailed conformations of ${\pi}-{\pi}$ stacking were also discussed by the observations of upfield shifts of some aromatic protons upon complexation from $^1H$ NMR spectra.

• Bulletin of the Korean Chemical Society
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• 제17권11호
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• pp.1045-1052
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• 1996

The effects of G-T mismatches on thermal stability, the base-pair lifetime and the global structure of a d(GCGTGCGC)2 duplex were studied by using 1H NMR, UV and CD spectroscopy. The existence of G-T mismatches was found to cause a noticeable change in the chemical environment of imino protons associated with significant decrease in the base-pair lifetime at the mismatched site as well as in thermal stability of the duplex itself. The melting transition of d(GCGTGCGC)2 was not cooperative at all at 100 mM or lower concentration of NaCl, but became cooperative at 500 mM or higher NaCl concentration. The melting temperature (Tm) of this duplex was 32℃ at 500 mM concentration of NaCl, which is much lower than that of d(GCGCGCGC)2 at the same NaCl concentration. This suggests that the decrease in stability may be ascribed to the decrease in the base-pair lifetime and the deviation from the normal structure due to the G-T mismatches. Adding berenil to d(GCGTGCGC)2 caused no observable change in the global structure but the large decrease in the base-pair lifetime and the stability of the duplex.

• Bulletin of the Korean Chemical Society
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• 제14권5호
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• pp.599-602
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• 1993

Micellization process of dodecyltrimethylammonium bromide (DTAB) was studied by using the aromatic probe (benzene) which dissolved in aqueous DTAB solutions. Proton NMR chemical shift measurements of DTAB and DTAB-benzene system showed that benzene molecules solubilized near the micelle-water interface and that the solubilization sites within the micelles are different as the DTAB concentration is passing through 32.0 mM (hereafter we refer this concentration as the second CMC). The change of solubilization sites is also confirmed by abrupt changes of the chemical shifts and relaxation rates of benzene protons in DATB-benzene system at this concentration. It was revealed from the electrical conductivity and viscosity measurements that the solubilization of benzene caused the DTAB micelles to swell out and that the micelles prepared after the second CMC had a greater swelling effect than those prepared before the second CMC. The transition point which reflects the saturation of benzene molecules on the solubilization sites of micelles was observed at one benzene/micellized DTAB mole ratio from the electrical conductivity measurements. Along the different concentration of DTAB solution, this transition point is appeared clearly after the second CMC. From these results it is suggested that the shapes and/or sizes of DTAB micelles of the spherical micelle region prepared after the second CMC are different from those prepared before the second CMC.

• Bulletin of the Korean Chemical Society
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• 제20권6호
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• pp.648-652
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• 1999

Studies have been carried out on the unusual molecular nonrigidity of CoⅢ(PymS)3 and Cp* RhⅢ(PymS)2(PymS:2-mercaptopyrimidine). The crystal structure of CoⅢ(PymS)3 approximates to an octahedral mer isomer with 4-membered N-Schelating fashion. For Cp*RhⅢ(PymS)2, one PymS ligand bonds to the rhodium ion in an S-monodentate mode (Rh-S(2) = 2.366(1)Å) while the other ligand chelates to the metal ion in an N,S-bidentae mode (Rh-S(1)=2.414(1);Rh-N(1)=2.103(3)Å). Even though the conformations and configurations of both complexes are still retained in solution, an unusual nonrigidity for the protons of the PymS region is obsered in the solution. The broad proton signals of CoⅢ(PymS)3 exhibit a temperature-dependence in the range of -40∼40℃ with a free energy of activation ΔG=64.49kJ/mol(40℃). For Cp*RhⅢ(PymS)₂,such a fluxionality has been markedly observed in solution. This fluxional behavior can be explained in terms of "ligand tautomerism" in metal complexes containing potential tautomeric forms.

• Archives of Pharmacal Research
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• 제27권1호
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• pp.31-34
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• 2004

The electrochemical behavior of doxorubicin hydrochloride was investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV). From CV and SWV studies of doxorubicin hydrochloride in the acetate buffers of various pH values, it was found that protons were involved in the reduction of the antibiotic at the $H^+/e^$- ratio at one ( $\DeltaEp/pH =-53 ∼ -61 mV at 23^{\circ}C$), proposing the electrochemical reduction of the quinone moiety in its anthraquinone aglycone. Its electrochemical behavior was pseudo-reversible in the acetate buffer of pH 3.5 by exhibiting the well-defined single cathodic and anodic waves and the ratio of $lp^a/lp^c$ at approximately one over the scan rates of 10∼100 mV/s. Fast and sensitive SWV showing a single peak of doxorubicin has been applied for its quantitative analysis using an acetate buffer of pH 3.5. A linearity was obtained when the peak currents (lp) were plotted against concentrations of doxorubicin in the range of $5.0\times10^{-7} M∼1.0\times10^{-5}$M with a detection limit of $1.0\times10^{-7}$ M.

• Archives of Pharmacal Research
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• 제12권1호
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• pp.17-21
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• 1989

We have reported earlier on the reactivity of 7-dithiocarboxy-3-phenyl-5,6-dihydro imidazo[2,1-b]thiazolium-betaine with several para-substituted phenacyl bromides. In this work reactions of 7-dithiocarboxy-3-phenyl(or methyl)-5,6-dihydro imidazo[2,1-b]thiazolium-betaine with a series of aliphatic alkylating agents of ${\alpha}$ -halo ketone,${\gamma}$-halo koto ester and ${\alpha}$ -halo ester were examined for the similar purpose. In case of ${\alpha}$-halo ketone or ${\gamma}$-halo koto ester such as ${\alpha}$ -chloro acetone or ethyl 4-chloro acetoacetate new biheterocyclic compound was obtained via ring transformation reaction. However, reaction of the betaine with methyl(or ethyl) bromoacetate used as a ${\alpha}$-halo ester, gave, in-stead, S-alkylated quarternary ammonium salt.

• 한국자기공명학회논문지
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• 제23권3호
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• pp.61-66
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• 2019

RNAs exhibit distinct structural and dynamic features required for proper function. The hydrogen-bonded imino protons of RNAs are a probe of the conformational transition and dynamic feature. MicroRNAs originate from primary transcripts containing hairpin structures. The levels of mature miR156 influence the flowering time of plants. To understand the molecular mechanism of biological function of $miR156:miR156^*$ duplex, we performed hydrogen exchange study on the model RNAs mimicking two phenotypes of $miR156:miR156^*$, $miR156:miR156^*$ (m-miR156a) and $miR156:miR156^*$ (m-miR156g) duplexes. This study found that the internal bulge of m-miR156a destabilized the neighboring base-pairs, whereas the bulge structure of m-miR156g did not affect the thermal stabilities of the neighboring base-pairs.

• Nuclear Engineering and Technology
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• 제51권1호
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• pp.275-283
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• 2019

Rare isotope beam facilities require shielding data in early stage of their design. There is much less shielding data on neutrons from the reactions between heavy ion beams and matter than the data on neutrons produced by protons. The purpose of the present work is to produce and thus increase the amount of shielding data on neutrons generated by high-energy heavy ion beams based on the RAON in-flight fragment facility. Calculations were performed with the computational Monte Carlo codes PHITS and MCNPX. The secondary neutron source terms were evaluated at 550 MeV/u for Ca, Kr, and Sn and at 400 MeV/u for U ions on a graphite target. Source terms and attenuation lengths were obtained by fitting the ambient dose equivalent inside an ordinary concrete shield.

• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1298-1305
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• 2018

The use of System-on-Chip (SoC) solutions in the design of on-board data handling systems is an important step towards further miniaturization in space. However, the Total Ionizing Dose (TID) and Single Event Effects (SEE) characterization of these complex devices present new challenges that are either not fully addressed by current testing guidelines or may result in expensive, cumbersome test configurations. In this paper we report the test setups, procedures and results for TID testing of a SoC microcontroller both using standard $^{60}Co$ and low-energy protons beams. This paper specifically points out the differences in the test methodology and in the challenges between TID testing with proton beam and with the conventional gamma ray irradiation. New test setup and procedures are proposed which are capable of emulating typical mission conditions (clock, bias, software, reprogramming, etc.) while keeping the test setup as simple as possible at the same time.