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151.
Anti‐Inflammatory Activity of a Novel Acetylene Isolated from the Roots of Angelica tenuissima Nakai
Hyun Gyu Choi Hyukjae Choi Jeong‐Hyung Lee Byung Sun Min Jeong Ah Kim 《Helvetica chimica acta》2016,99(6):447-451
Three polyacetylenes, one novel and two known, were isolated from the root of Angelica tenuissima. Using 1H‐ and 13C‐NMR, COSY, HMBC, and HMQC, their structures were found to be (3R,8S)‐heptadeca‐1‐en‐4,6‐diyne‐3,8‐diol ( 1 ), falcarindiol ( 2 ), and oplopandiol ( 3 ). Absolute configurations of compound 1 were established using Mosher's esterification. In addition, the polyacetylenes ( 1 – 3 ) were evaluated for their anti‐inflammatory activity. Compounds 1 and 3 showed potent inhibitory activity against lipopolysaccharide‐induced nitric oxide (NO) production in RAW267.7 macrophage cells with IC50 values of 4.31 and 5.06 μm, respectively. Compound 1 strongly inhibited inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)‐2 in a concentration‐dependent manner. 相似文献
152.
Kwang-Wook Kim Eil-Hee Lee In-Kyu Choi Jae-Hyung Yoo Hyun-Soo Park 《Journal of Radioanalytical and Nuclear Chemistry》2000,245(2):301-308
The electrochemical redox behavior of nitric acid was studied using a glassy carbon fiber column electrode system, and its reaction mechanism was suggested and confirmed in several ways. Electrochemical reactions in less than 2.0M nitric acid was not observed. However, in more than 2.0M nitric acid, the reduction of nitric acid to nitrous acid occurred and the reduction rate was slow so that the nitric acid solution had to be in contact with an electrode for a period of time long enough for an apparent reduction current of nitric acid to nitrous acid to be observed. The nitrous acid generated in more than 2.0M nitric acid was rapidly and easily reduced to nitric oxide by an autocatalytic reaction. Sulfamic acid was confirmed to be effective to destroy the nitrous acid. At least 0.05M sulfamic acid was necessary to scavenge the nitrous acid generated in 3.5M nitric acid. 相似文献
153.
The human organic anion transporter 4 (hOAT4) has been identified as the fourth isoform of OAT family. hOAT4 contributes to move several negatively charged organic compounds between cells and their extracellular milieu. The functional characteristics and regulatory mechanisms of hOAT4 remain to be elucidated. It is well known that caveolin plays a role in modulating proteins having some biological functions. To address this issue, we investigated the co-localization and interaction between hOAT4 and caveolin-1. hOAT4 and caveolin-1 (mRNA and protein expression) were observed in cultured human placental trophoblasts isolated from placenta. The confocal microscopy of immuno-cytochemistry using primary cultured human trophoblasts showed hOAT4 and caveolin-1 were co-localized at the plasma membrane of the cell. This finding was confirmed by Western blot analysis using isolated caveolae-enriched membrane fractions and immune-precipitates from the trophoblasts. When synthesized cRNA of hOAT4 along with scrambled- or antisense-oligodeoxynucleotide (ODN) of Xenopus caveolin-1 were co-injected to Xenopus oocytes, the [3H]estrone sulfate uptake was significantly decreased by the co-injection of antisense ODN but not by scrambled ODN. These findings suggest that hOAT4 and caveolin-1 share a cellular expression in the plasma membrane and caveolin-1 up-regulates the organic anionic compound uptake by hOAT4 under the normal physiological condition. 相似文献
154.
155.
156.
Huang XJ Im HS Yarimaga O Kim JH Lee DH Kim HS Choi YK 《The journal of physical chemistry. B》2006,110(43):21850-21856
Carboxylated single-walled carbon nanotubes (SWCNT) chemically assembled on gold substrate was employed as netlike electrode to investigate the charge-transfer process and electrode process kinetics using uric acid as an example. The electrochemical behavior of uric acid in carboxylated SWCNT system was investigated using cyclic voltammetry, chronoamperometry, and single potential time-based techniques. The properties of raw SWCNT electrode were also studied for comparison purpose. Uric acid has better electrochemical behavior whereas ascorbic acid has no effective reaction on the carboxylated SWCNT electrode. Cyclic voltammograms indicate that the assembled carboxylated SWCNT increases more active sites on electrode surface and slows down the electron transfer between the gold electrode and uric acid in solution. The charge-transfer coefficient (alpha) for uric acid and the rate constant (k) for the catalytic reaction were calculated as 0.52 and 0.43 s(-1), respectively. The diffusion coefficient of 0.5 mM uric acid was 7.5 x 10(-6) cm2 x s(-1). The results indicate that electrode process in the carboxylated SWCNT electrode system is governed by the surface adsorption-controlled electrochemical process. 相似文献
157.
Choi JC Kohno K Masuda D Yasuda H Sakakura T 《Chemical communications (Cambridge, England)》2008,(6):777-779
Iron triflate, in situ-formed from FeCl3 and triflic acid, or FeCl3 and silver triflate efficiently catalyse the intermolecular addition of carboxylic acids to various alkenes to yield carboxylic esters; the reaction is applicable to the synthesis of unstable esters, such as acrylates. 相似文献
158.
Yoon SH Moon JH Choi KM Kim MS 《Rapid communications in mass spectrometry : RCM》2006,20(14):2201-2208
A deflection system consisting of four deflectors was designed and used to reduce the interference from post-source decay (PSD) product ions in photodissociation (PD) tandem time-of-flight (TOF) mass spectrometry. For simple protonated peptides generated by matrix-assisted laser desorption/ionization, the presence of PSD product ions at the laser irradiation spot was found to noticeably alter the minor peaks in the PD spectra even though the major ones were hardly affected. Other benefits from the use of the deflection system such as the improvement in the resolving power in PSD tandem mass spectra are discussed. 相似文献
159.
TiO(2) sensitized by derivatized ruthenium bipyridyl complexes has been intensively investigated as a tool to utilize visible light. This article describes an alternative approach to attaching ruthenium complex sensitizers at the TiO(2)/H(2)O interface, which is a much simpler and more efficient way to produce hydrogen. The surface of TiO(2) particles are simply coated with perfluorosulfonate polymer (cation-exchange resin: Nafion), and then Ru(bpy)(3)(2+) (as a cationic form), whose bipyridyl ligands are not functionalized with carboxylic acid groups, are bound within the Nafion layer through electrostatic attraction. The visible-light-induced production of H(2) on Nf/TiO(2) using simple Ru(bpy)(3)(2+) as a sensitizer is far more efficient than that on Ru(dcbpy)(3)-TiO(2), upon which many sensitized photoelectrochemical conversion systems are based. Effects of various experimental parameters such as pH, concentration of Ru(bpy)(3)(2+), Nafion loading, and the kind of TiO(2) were investigated. Under optimized conditions, the H(2) production rate was about 80 mumol/h, which corresponds to an apparent photonic efficiency of 2.6%. The roles of the Nafion layer on TiO(2) in the sensitized H(2) production are proposed to be twofold: to provide binding sites for cationic sensitizers and to enhance the local activity of protons in the surface region. 相似文献
160.
S.-Y. Jeon M.-B. Choi J.-H. Hwang E. D. Wachsman Sun-Ju Song 《Journal of Solid State Electrochemistry》2012,16(2):785-793
The oxygen excess nonstoichiometry of La2NiO4 + δ
is measured as a function of temperature and oxygen partial pressure (pO2) by coulometric titration method. A positive deviation from the ideal dilution solution behavior is exhibited, and the partial
molar thermodynamic quantities of La2NiO4 + δ
are calculated from the Gibbs–Helmholtz equation for regular solution by introducing the activity coefficient of the charge
carriers. The activity coefficient of holes is successfully calculated by using the Joyce–Dixon approximation of the Fermi–Dirac
integral. The effective mass of holes (
m\texth* m_{\text{h}}^{{*}} ) is 1.27–1.29 times the rest mass (m
h), which indicate the action of band-like conduction and allow the effect of the small degree of polaron hopping to be ignored.
The activity coefficient of holes calculated against the oxygen nonstoichiometry clearly illustrates the early positive deviation
of the activity coefficient of holes from unit, leading to
g\texth · \gamma_{{{\text{h}}^{ \bullet }}} ≈ 14 at δ ≈ 0.08, which is quite close to the literature value of
g\texth · \gamma_{{{\text{h}}^{ \bullet }}} ≈ 10 at δ ≈ 0.08. All the evaluated thermodynamic quantities are in good agreement with the experimental literature values. 相似文献