• Title/Summary/Keyword: Kinetic-spectrophotometry

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Synthesis of Carbobenzoxy-alanyl-thiaarginine (thialysine) benzyl ester and kinetic Studies with Trypsin

  • 홍남주;장성훈;진동훈
    • Bulletin of the Korean Chemical Society
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    • v.19 no.6
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    • pp.689-695
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    • 1998
  • Carbobenzoxy-alanyl-thiaarginine benzyl ester and carbobenzoxy-alanyl-thialysine benzyl ester were synthesized in solution. Kinetic studies were carried out using three different analytical methods, semi-classical method, progress curve analysis and competitive spectrophotometry. In competitive spectrophotometry, carbobenzoxy-valyl-glycyl-arginyl-p-nitroaniline was used as a detector. Kinetic constants such as $K_m$ and $V_{max}$ measured by competitive spectrophotometry are almost the same as those values measured by semi-classical method. Colorimetric Ellman's assays showed the thio-peptido mimetics to be a suitable substrates for trypsin. Kinetic studies with trypsin gave $K_m$ of 2.33 mM and $k_{cat}$ of $1.50{\times}10^5\;min^{-1}$ for carboxy-alanyl-thiaarginine benzyl ester and $K_m$ of $3.41{\times}10^{-3}\; Mm\; and\; k_{cat}\; of\; 520{\times}102\; min^{-1}$ for carbobenzoxy-alanyl-thialysine benzyl ester, respectively. Kinetic constants $(K_m=2.04{\times}10^{-2}\; mM, K_{cat}=4.42{\times}10^3 \;min^{-1})$ for natural substrate, carbobenzoxy-alanyl-lysine benzyl ester, were also evaluated by competitive spectrophotometry in order to compare the mode of binding on trypsin.

Competitive Spectrophotometry for Microbial Dipeptide Transport Systems

  • Hwang, Se-Young;Ki, Mi-Ran;Cho, Suk-Young;Lim, Wang-Jin;Yoo, Ick-Dong
    • Journal of Microbiology and Biotechnology
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    • v.6 no.2
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    • pp.92-97
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    • 1996
  • Portage kinetic constants of peptide transport can be measured by competitive spectrophotometry. The kinetic constants of L-Glu-L-Glu transport in Escherichia coli were ascertained using L-Phe-L-3-thia-Phe (PSP) as a detector. Since the production of thiophenol upon intracellular hydrolysis of PSP was competitively inhibited by L-Glu-L-Glu, it was able to compute the kinetic constants of L-Glu-L-Glu using this method. The resulted data were in agreement with the values obtained by the method of Michaelis-Menten kinetics. The potential of this method was examined against dipeptide transport systems in various microorganisms. These results strongly suggest that the overall properties of individual systems for dipeptide transports can be easily characterized by competitive spectrophotometry.

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Effect of Cationic and Anionic Porphyrins on the Structure and Activity of Adenosine Deaminase

  • Ajloo, Davood;Hajipour, Samaneh;Saboury, Ali Akbar;Zakavi, Saeed
    • Bulletin of the Korean Chemical Society
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    • v.32 no.9
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    • pp.3411-3420
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    • 2011
  • Kinetic and structural studies have been carried out on the effects of meso-tetrakis(4-sulfonatophenyl)-porphyrin ($H_2TPPS_4$) as an anionic and meso-tetrakis(3-N-methyl-pyridyl)porphyrin ($H_2TMPYP$) as a cationic porphyrin with adenosine deaminase (ADA) in 25 mM citrate/phosphate buffer, pH = 4-8, at $37^{\circ}C$ using UVvis spectrophotometry, circular dichroism (CD), fluorescence spectrophotometry as well as molecular dynamics (MD) and molecular docking. Kinetic results showed that the two porphyrins are non-competitive inhibitors. Increasing pH, increases $K_I$ and cationic porphyrin has a higher $K_I$ and lower binding constant ($K_b$) at all pH ranges. Analyzing the secondary structure revealed that both ligands decrease the secondary structure and that the anionic porphyrin is more effective.

Spectrophotometric and Kinetic Determination of Some Sulphur Containing Drugs in Bulk and Drug Formulations

  • Walash, M.I.;El-Brashy, A.M.;Metwally, M.S.;Abdelal, A.A.
    • Bulletin of the Korean Chemical Society
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    • v.25 no.4
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    • pp.517-524
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    • 2004
  • Two simple and sensitive spectrophotometric methods were developed for the determination of carbocisteine, penicillamine, ethionamide and thioctic acid in bulk and in their pharmaceutical preparations using alkaline potassium permanganate as an oxidizing agent. The first one involves determination of ethionamide and thioctic acid by spectrophotometric investigation of the oxidation reaction of the two drugs. The second method involves determination of carbocisteine and penicillamine by kinetic studies of the oxidation reaction of these two drugs at room temperature for a fixed time of 20 minutes. The absorbance of the colored manganate ions was measured at 610 nm in both methods. 1-10 ${\mu}$g/mL of ethionamide and thioctic acid could be etermined by the spectrophotometric method with detection limits of 0.11 and 0.089 ${\mu}$g/mL for the two drugs respectively. 2-10 ${\mu}$g/mL of carbocisteine and penicillamine could be determined by the kinetic method with detection limits of 0.14 and 0.21 ${\mu}$g/mL respectively. The two methods were successfully applied for the determination of these drugs in their dosage forms.

Photocatalytic Degradation of 3-Nitrophenol with ZnO Nanoparticles under UV Irradiation

  • Li, Jiulong;Ko, Weon Bae
    • Elastomers and Composites
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    • v.52 no.2
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    • pp.131-135
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    • 2017
  • Zinc nitrate hexahydrate [$Zn(NO_3){\cdot}6H_2O$] and sodium hydroxide [NaOH] were used as source reagents in the preparation of ZnO nanoparticles in an aqueous solution containing deionized water and ethanol in a ratio of 2:5 (v/v). ZnO nanoparticles were heated in an electric furnace at $700^{\circ}C$ for 2 h under an atmosphere of inert argon gas. The morphological and structural properties of the nanoparticles were characterized by scanning electron microscopy (SEM) and powder X-ray diffractometry (XRD). UV-vis spectrophotometry was used to analyze the photocatalytic degradation of 3-nitrophenol with ZnO nanoparticles as photocatalyst under ultraviolet irradiation at 254 nm. Evaluation of the kinetic of the photo-catalytic degradation of 3-nitrophenol indicated that the degradation of 3-nitrophenol with ZnO nanoparticles obeyed the pseudo-first order reaction rate model.

Kinetic and Molecular Orbital Stuides on the Reaction of 5-nitrofurfural Hydrazone Formation

  • Lee, Kyung-Hee;Jee, Jong-Gi
    • Bulletin of the Korean Chemical Society
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    • v.6 no.5
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    • pp.280-284
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    • 1985
  • Kinetic measurements of the 5-nitrofurfural-hydrazine reaction in various pH ranges of aquous solution were carried out by ultraviolet spectrophotometry at $25^{\circ},\;35^{\circ}\;and\;45^{\circ}C$. The observed rate of the reaction varies with the change in pH, which gives characteristic "bell-type" rate acidity profile. The maximum rate is shown in the vicinity of pH 4. This reaction procceds with rate-determining attack of hydrazine on the 5-nitrofurfural at low pH and undergoes a change in rate-determining step to dehydration of the addition intermediate as pH increases. The reaction has a "reactant-like transition state" which precedes intermediate in low pH and "product-like transition state" which follows it in neutral pH. The geometry of 5-nitrofurfural-hydrazine intermediate was estimated with PCILO method associated with CNDO/2 scheme.

The Investigation of a Novel Indicator System for Trace Determination and Speciation of Selenium in Natural Water Samples by Kinetic Spectrophotometric Detection

  • Gurkan, Ramazan;Ulusoy, Halil Ibrahim
    • Bulletin of the Korean Chemical Society
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    • v.31 no.7
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    • pp.1907-1914
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    • 2010
  • A novel catalytic kinetic method is proposed for the determination of Se(IV), Se(VI) and total inorganic selenium in water based on the catalytic effect of Se(IV) on the reduction of bromate by p-nitrophenylhydrazine at pH 3.0. The generated bromine, $Br_2$ or $Cl_2$ plus $Br_2$ in 0.1 M NaCl (or NaBr) environment efficiently decolorized Calmagite and the reaction was monitored spectrophotometrically at 523 nm as a function of time. In this indicator reaction, bromide acted as an activator for the catalysis of selenium (IV) and a reducing agent for selenium (VI) at pH 3.0, which allowed the determination of total selenium. The fixed time method was adopted for the determination and speciation of inorganic selenium. Under the optimum conditions, the calibration graph are linear in the range 1 - 35 ${\mu}gL^{-1}$ of Se(IV) for the fixed time method at $25^{\circ}C$. The detection limit based on statistical $3S_{blank}$/m-criterion was 0.215 ${\mu}gL^{-1}$ for the fixed time method (7 min). All of the variables that affect the sensitivity at 523 nm were investigated, and the optimum conditions were established. The interference effect of various cations and anions on the Se (IV) determination was also studied. The selectivity of the selenium determination was greatly improved with the use of the strongly cation exchange resin such as Amberlite IR120 plus. The proposed kinetic method was validated statistically and through recovery studies in natural water samples. The RSDs for ten replicate measurements of 5, 15 and 25 ${\mu}gL^{-1}$ of Se(IV) and Se(VI) was changed between 2.1 - 4.85%. Analyses of a certified standard reference material (NIST SRM 1643e) for selenium using the fixed-time method showed that the proposed kinetic method has good accuracy. Se(IV), Se(VI) and total inorganic selenium in environmental water samples have been successfully determined by this method after selective reduction of Se(VI) to Se(IV).

A Kinetic Study of the Substitution of $\beta$-Disketone in Bis($\beta$-diketonato)Oxovanadium (IV) ((베타-디케토네이토) 옥소바나듐 (IV) 착물에서의 베타-디케톤 치환반응에 관한 속도론적 연구)

  • Hwang, Gyu Tak;Kim, Jeong Seong;Sin, Han Cheol;Kim, In Hwan;Kim, Gi Tae
    • Journal of the Korean Chemical Society
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    • v.34 no.4
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    • pp.319-324
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    • 1990
  • Kinetic of substitution of dibenzoylmethanate (dbm) for one acetylacetonate (acac) in VO (acac)$_2$ have been studied in various solvents by spectrophotometry. Under the condition [VO (acac)$_2$] 》[Hdbm], the rate law for the substitution reaction is expressed as, rate = k$_2$K[VO(acac)$_2$] [Hdbm] / (1 + K[VO(acac)$_2$]) where K = [VO (acac)$_2$dbmH] / [VO(acac)$_2$][Hdbm] and the rate constant k$_2$ corresponds to that of proton transfer from coordinated Hdbm to leaving acac- in VO(acac)$_2$dbmH.

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Kinetics and Mechanism for aquation of [Co(en)2(CO3)]+ in [H+] aqueous solution (산 수용액내에서 [Co(en)2(CO3)]+의 아쿠아 반응속도와 반응메커니즘)

  • Lee, Chul-Je;Kim, Dong-Yeub
    • Journal of the Korean Society of Industry Convergence
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    • v.8 no.3
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    • pp.155-160
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    • 2005
  • Kinetic studies were carried out for aquation of carbonatobis(ethylenediamine)cobalt(III) complexes in [H+] aqueous solution by UV/VIS-spectrophotometry. The rate law that in deduced from rate data is $rate=k_H{^+}[H^+]^{1.4}$ {$[Co(en)_2(CO_3)]^+$}1.0 where $k_H{^+}$ is the rate constant considering acidic catalyst, $H^+$ ion whose value is $0.241l{\cdot}mol^{-1}{\cdot}sec^{-1}$. The values of activation parameters Ea, ${\Delta}H^{\ast}$ and ${\Delta}S^{\ast}$ were $15.33Kcal{\cdot}mol^{-1}$, $14.52Kcal{\cdot}mol^{-1}$ and -57.49 e.u. respectively. On the basis of kinetic data and the observed activation parameters, we have proposed the mechanism that proceeds with two step protonations. The rate equation derived from the proposed mechanism has been in agreement with the observed rate equation. It has been seen that our modified mechanism for Harris's proton freequilibrium one prefer to the his concerted mechanism, and more the last product substitute $H_2O$ for $OH^-$ the Harris's mechanism in the acidity range 2 < pH < 5.

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A Product Inhibition Study on Adenosine Deaminase by Spectroscopy and Calorimetry

  • Saboury, Ali Akbar;Divsalar, Adeleh;Jafari, Ghasem Ataie;Moosavi-Movahedi, Ali Akbar;Housaindokht, Mohammad Reza;Hakimelahi, Hosain
    • BMB Reports
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    • v.35 no.3
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    • pp.302-305
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    • 2002
  • Kinetic and thermodynamic studies have been made on the effect of the inosine product on the activity of adenosine deaminase in a 50 mM sodium phosphate buffer, pH 7.5, at $27^{\circ}C$ using UV spectrophotometry and isothermal titration calorimetry (ITC). A competitive inhibition was observed for inosine as a product of the enzymatic reaction. A graphical-fitting method was used for determination of the binding constant and enthalpy of inhibitor binding by using isothermal titration microcalorimetry data. The dissociation-binding constant is equal to $140\;{\mu}M$ by the microcalorimetry method, which agrees well with the value of $143\;{\mu}M$ for the inhibition constant that was obtained from the spectroscopy method.