• Title, Summary, Keyword: Hill reaction

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Kinetics of Oxidation of Nitrotoluenes by Acidic Hexacyanoferrate (Ⅲ)

  • Bhattacharjee, A. K.;Mahanti, M. K.
    • Bulletin of the Korean Chemical Society
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    • v.4 no.3
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    • pp.120-123
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    • 1983
  • The reaction of hexacyanoferrate (Ⅲ) with nitrotoluenes in aqueous acetic acid containing perchloric acid(1.0 M) at $50^{\circ}C$ gave the corresponding aldehyde as the major product. The order with respect to each of the reactants ― substrate, oxidant and acid ― was found to be unity. The Hammett plot yielded a ${\sigma}^+$ value of -1.30, and the kinetic isotope effect gave a $k_H/k_D$ value of 6.2. The pathway for the conversion of the nitrotoluenes to the products has been mechanistically visualized as proceeding through the benzylic radical intermediate, formed in the rate determining step of the reaction.

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The Effect of Newly Synthesized Compounds on the Photosynthetic Electron Transport of Cyanobacteria (Anacystis nidulans $R_2$) (신규(新規) 합성화합물들이 cyanobacteria의 광합성전자전달계에 미치는 영향)

  • Hwang, I.T.;Kim, J.S.;Cho, K.Y.;Yoneyama, K.;Yoshida, S.
    • Korean Journal of Weed Science
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    • v.13 no.2
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    • pp.89-95
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    • 1993
  • The Inhibiting activity of newly synthesized phenol (E-series) and triazine (T-series) derivatives was evaluated by using thylakoid membranes extracted from cyanobacteria (Anacystis nidulans $R_2$). There were no significant differences between phenol derivatives and dinoseb to the thylakoid membrane extracted from wild type in the Hill reaction. However, a phenol derivative, E-24 which has no -Cl at phenyl ring, did not show any activity. The longer the length of R substituents was in phenol derivatives, the lower inhibiting activity was in the Hill reaction. Triazine derivatives, T-27, T-28, T-40, T-41, T-47 and T-48 were also compared with diuron and atrazine. Among triazine compounds, T-27 and T-28 showed 10 and 30 times activity as high as atrazine to wild type, respectively. Other triazine derivatives, T-40, T-41, T-47 and T-48 showed low inhibiting activity to wild and mutant type. A structural difference of T-27 and T-28 from T-40, T-41, T-47 and T-48 was the presented of -C-NH-. Both T-27 and T-28 were very closely associated with serine, an amino acid located at the 264th position of D1 protein because of the resistant ratio(R/S) to mutant G-264 were higher than that of atrazine.

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Effects of Different Extraction Extraction Media and Reaction Mixtures on Photosystem II Activity of Spinach Chloroplasts (시금치 엽록체의 광계의 활성에 미치는 추출용매와 반응용액의 영향)

  • 권병규
    • Journal of Plant Biology
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    • v.19 no.4
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    • pp.95-99
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    • 1976
  • This work deals with different extraction media and reaction mixtures on photosystem II activity of Spinach chloroplasts. The photoreduction rate of ferricyanide and DPIP by intact chloroplasts which extracted with four kinds of extraction media; S-Tris-N pH 7.2, 8.0, S-Tricine-N pH 7.2, 8.0, was measured in five kinds of reaction mixtures; S-Tris-N pH 7.2, 8.0, S-Tricine-N pH 7.2, 8.0, 0.05 M-Tris pH 7.2. The extraction medium which shows the highest photoreduction rate was S-Tris-N at pH 7.2 and S-Tricine-N at pH 8.0. As to the reaciton mixture, S-Tricine-N pH 8.0 showed the highest rate. On the complex effects of extraction media and reaction mixtures, the highest photordeuction rate of Hill oxidant by intact chloroplasts was obtained by S-Tris-N pH 7.2 extraction medium and S-Tricine-N pH 8.0 reaction mixture. The second highest activity was obtained by S-Tricine-N pH 8.0 extraction medium and reaction mixture.

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Rapid Hydrolysis of Ginseng Saponin by Microwave Oven Reaction (전자렌지 반응을 이용한 인삼 사포닌의 신속한 가수분해법)

  • Park, Man-Ki;Park, Jeong-Hill;Kang, Jong-Seong;Lee, Mi-Young;Park, Young-In;Yu, Su-Jeong;Han, Byung-Hoon
    • Journal of Ginseng Research
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    • v.17 no.1
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    • pp.35-38
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    • 1993
  • A new and rapid method for the hydrolysis of ginsenosides to panaxadiol or panaxatriol was developed. It is based on the microwave oven reaction, which is high temperature and high-pressure reaction. The optimal hydrolysis time using 5% $H_2SO_4$ solution was found at 10 min PTFE reaction vessel in microwave oven, which is more than 30 times faster than the conventional hydrolysis method.

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Biorational Screening System Using Cyanobacteria(Anacystis nidulans $R_2$) for Searching the Photosynthetic Electron Transport Inhibitors (Cyanobacteria를 이용한 광합성 전자전달저해제의 생합리적 스크리닝)

  • Hwang, I.T.;Hong, K.S.;Cho, K.Y.;Yoshida, S.
    • Korean Journal of Weed Science
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    • v.13 no.2
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    • pp.81-88
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    • 1993
  • For searching the photosynthetic electron transport(PET) inhibitors, bio-rational screening system using thylakoid membranes extracted from wild and mutant cyanobacteria(Anacystis nidulans $R_2$) was developed. Generally, thylakoid membrane was more sensitive to the tested herbicides than the chloroplast from spinach in the Hill reaction. Higher resistant characteristics appeared in mutant D-5, Di-22 to diuron and mutant G-264 to atrazine as compared to wild type. To test the reaction of thylakoid membrane to herbicides, diuron and atrazine were applied simultaneously. Diuron and atrazine competed each other for binding with substituted amino acids, while diuron and dinoseb were non-competitive, and inhibiting activity was increased. Conclusively, bio-rational screening system using cyanobacteria was proved to be fast and efficient screening method for the development of PET inhibitors.

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Stability analysis of the rotating and stationary grooved journal bearings (정지홈과 회전홈을 갖는 저널베어링의 안정성 평가)

  • Lee, M.H.;Lee, J.H.;Jang, G.H.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.141-146
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    • 2013
  • This research investigates the stability analysis for the rotating and the stationary grooved journal bearing. The dynamic coefficients of the journal bearing are calculated by using FEM and the perturbation method. When journal bearing is in whirling motion, the dynamic coefficients have time-varying components as a sine wave due to the reaction force of oil film toward the center of journal even in the steady state. The solutions for the equations of motion can be assumed as the Fourier series expansion. The equations of motion can be rewritten as the linear algebraic equations with respect to the Fourier coefficients. Then, stability of the grooved journal bearing can be calculated by Hill's infinite determinant. The periodic function of dynamic coefficients is derived using Fourier Fast Transform(FFT).The stability of journal bearing is determined as rotating speed increases and the stability of rotating grooved journal bearing is compared and discussed with the stability of stationary grooved journal bearing.

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Chemical and Free Radical-scavenging Activity Changes of Ginsenoside Re by Maillard Reaction and Its Possible Use as a Renoprotective Agent

  • Yamabe, Noriko;Song, Kyung-Il;Lee, Woo-Jung;Han, Im-Ho;Lee, Ji-Hwan;Ham, Jung-Yeob;Kim, Su-Nam;Park, Jeong-Hill;Kang, Ki-Sung
    • Journal of Ginseng Research
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    • v.36 no.3
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    • pp.256-262
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    • 2012
  • Reactive oxygen species play critical role in kidney damage. Free radical-scavenging activities of Panax ginseng are known to be increased by heat-processing. The structural change of ginsenoside and the generation of Maillard reaction products (MRPs) are closely related to the increased free radical-scavenging activities. In the present study, we have demonstrated the Maillard reaction model experiment using ginsenoside Re and glycine mixture to identify the renoprotective effect of MRPs from ginseng or ginsenosides. Ginsenoside Re was transformed into less-polar ginsenosides, namely Rg2, Rg6 and F4 by heat-processing. The free radical-scavenging activity of ginsenoside Re-glycine mixture was increased in a temperature-dependant manner by heatprocessing. The improved free radical-scavenging activity by heat-processing was mediated by the generation of antioxidant MRPs which led to the protection of LLC-PK1 renal epithelial cells from oxidative stress. Although the free radical scavenging activities of less-polar ginsenosides were weak, they could protect LLC-PK1 cells from oxidative stress. Therefore, MRPs and less-polar ginsenosides contributed to the combined renoprotective effects against oxidative renal damage.

Effect of Cytosine Analogues on Cytosine Deaminase from Aspergillus fumigatus IFO 5840 (Aspergillus fumigatus IFO 5840의 Cytosine Deaminase에 미치는 Cytosine Analogue의 영향)

  • 김재근
    • The Korean Journal of Food And Nutrition
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    • v.10 no.1
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    • pp.53-59
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    • 1997
  • In this study investigated the effect of cytosine deaminase activity from Aspergillus fumigatus IFO 5840 by cytosine analogues. The results were as follows. The enzyme was strongly inibited by 2-thiouracil, 2-thiocytosine, 6-azacytosine and 2-mercaptopyrimidine. The half inhibitory concentration(HIC) of 2-thiocytosine and 6-azacytosine on cytosine deaminase was 0.80mM and 1.15mM, respectively. The enzyme was inhibited at a certain level by addition of 2-thiocytosine immediately, but was maintained to some extend under the inhibited state by 6-azacytosine in proportion to reaction time. Regardless of kinds of substrate such as cytosine and 5-fluorocytosine, 2-thiocytosine and 6-azacytosine showed action as inhibitors, 2-thiocytosine inhibited cytosine deaminase activity about twice as strong as 6-azacytosine. The enzyme, when cytosine was used as a substrate, was revealed the pattern of competitive inhibition by 2-thiocytosine and 6-azacytosine, The ki value for these compounds was 4.5$\times$10-4M and 1.756$\times$10-3M, respectively. At this point, the Hill coefficient for cytosine, 2-thiocytosine and 6-azacytosine was 1.80, 1.81 and 2.45, respectively.

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Unusual Allosteric Property of L-alanine Dehydrogenase from Bacillus subtilis

  • Kim, Soo-Ja;Lee, Woo-Yiel;Kim, Kwang-Hyun
    • BMB Reports
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    • v.31 no.1
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    • pp.25-30
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    • 1998
  • Kinetic studies of L-Alanine dehydrogenase from Bacillus subtilis-catalyzed reactions in the presence of $Zn^{2+}$ were carried out. The substrate (L-alanine) saturation curve is hyperbolic in the absence of the metal ion but it becomes sigmoidal when $Zn^{2+}$ is added to the reaction mixture indicating the positive cooperative binding of the substrate in the presence of zinc ion. The cooperativity of substrate binding depends on the xinc ion concentration: the Hill coefficients ($n_H$) varied from 1.0 to 1.95 when the zinc ion concentration varied from 0 to $60\;{\mu}m$. The inhibition of AlaDH by $Zn^{2+}$ is reversible and noncompetitive with respect to $NAD^+$ ($K_i\;=\;5.28{\times}10^{-5}\;M$). $Zn^{2+}$ itself binds to AlaDH with positive cooperativity and the cooperativity is independent of substrate concentration. The Hill coefficients of substrate biding in the presence of $Zn^{2+}$ are not affected by the enzyme concentration indicating that $Zn^{2+}$ binding does not change the polymerization-depolymerization equilibria of the enzyme. Among other metal ions, $Zn^{2+}$ appears to be a specific reversible inhibitor inducing conformational change through the intersubunit interaction. These results indicate that $Zn^{2+}$ is an allosteric competitive inhibitor and substrate being a non-cooperative per se, excludes the $Zn^{2+}$ from its binding site and thus exhibits positive cooperativity. The allosteric mechanism of AlaDh from Bacillus subtilis is consistent with both MWC and Koshland's allosteric model.

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