• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.111-116
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• 2014

The kinetics and mechanism of oxidation of sulfanilic acid by N-chloro-p-toluene sulfonamide (chloramine-T) have been studied in acid medium. The species of chloramine-T were analysed on the basis of experimental observations and predominantly reactive species was taken into account for proposition of most plausible reaction mechanism. The derived rate law (1) conforms to such a mechanism. $$-\frac{d[CAT]}{dt}=\frac{kK_1[RNHCl][SA]}{K_1+[H^+]}$$ (1) All kinetic parameters were evaluated. Activation parameters such as energy and entropy of activation were calculated to be $(61.67{\pm}0.47)kJmol^{-1}$ and $(-62.71{\pm}2.48)kJmol^{-1}$ respectively employing Eyring equation.

• Journal of Microbiology
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• v.33 no.4
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• pp.289-294
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• 1995

The action mechanism of hemolysin rendering virulency of Vibrio anguilarum has not clarified as yet, even though there were several possible factors explained. We have studied hemolytic kinetics performed by hemolysin from V. anguillarum strain V7 as well as binding of hemolysin to RBC membrane. Maximal rate of hemolysis and duration of lag phase were directly and inversly correlated to the concentration of hemolysin used. Hemolysin molecules are known to bind consumptively with proper diameter, while other protectants with smaller diameter could not. In conclusion, hemolysin should bind irreversibly to RBC membrane exert hemolysis distorting osmotic pressure. The binding could be hindered by spatial structure of the RBC surfacem which might be caused by sialic acid.

• Bulletin of the Korean Chemical Society
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• v.16 no.9
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• pp.839-844
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• 1995

The kinetics and mechanism of the reactions of phenyl benzoates with benzylamines and pyrrolidine are investigated in acetonitrile. The variations of ρX (ρXY>0) and ρZ (ρYZ<0) with respect to the substituent in the substrate (σY) indicate that the reactions proceed through a tetrahedral intermediate, T±, with its breakdown in the rate determining step. The large magnitudes of ρZ, ρXY and ρYZ as well as the effects of secondary kinetic isotope effects involving deuterated nucleophiles are also in line with the proposed mechanism.

• Journal of the Korean Chemical Society
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• v.56 no.1
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• pp.28-33
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• 2012

The kinetics of ruthenium(III) chloride catalyzed oxidation of butanone and uncatalyzed oxidation of cyclohexanone by cerium(IV) in sulphuric acid medium have been studied. The kinetic rate law(I) in case of butanone conforms to the proposed mechanism. $$-\frac{1}{2}\frac{d[Ce^{IV}]}{dt}=\frac{kK[Ru^{III}][butanone]}{1+K[butanone]}$$ (1). However, oxidation of cyclohexanone in absence of catalyst accounts for the rate eqn. (2). $$-\frac{1}{2}\frac{[Ce^{IV}]}{dt}=\frac{(k_1+k_1K^'[H^+])[Ce^{IV}][Cyclohexanone]}{1+K_3[HSO_4^-]}$$ (2) Kinetics and activation parameters have been evaluated conventionally. Kinetically preferred mode of reaction is via ketonic and not the enolic forms.

• Journal of the Korean Chemical Society
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• v.56 no.2
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• pp.212-216
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• 2012

The kinetics of oxidation of nicotinic acid by peroxomonosulfate (PMS) has been studied in acetate buffers. Stoichiometry of the reaction corresponds to the reaction of one mole of the oxidant with a mole of nicotinic acid. N${\rightarrow}$O product has been confirmed both by UV visible and IR spectroscopy. The reaction is second order viz. first order with respect to each reactant. Activation parameters have also been evaluated. A plausible reaction mechanism is mentioned and the derived kinetic rate law accounts for experimental observations.

• BMB Reports
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• v.29 no.3
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• pp.210-214
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• 1996

The pH dependence of the kinetic parameters of mutant O-acetylserine sulfhydrylase (OASS) from Salmonella typhimurium LT-2 has been determined in order to obtain information on the chemical mechanism. The initial velocity pattern obtained by varying the concentrations of OAS at several fixed concentrations of TNB, shows an intersection on the left of the ordinate at pH 7.0, indicating that the kinetic mechanism is a sequential mechanism in which substrate inhibition by OAS is observed while the wild type enzyme showed a ping pong mechanism. The values of $V/E_t$, $V/K_{OAS}E_{t}$ and $V/K_{TNB}E_{t}$ decreased by about 68%, 14% and 16% as compared with the wild type enzyme. The $V/K_{OAS}E_{t}$ is a pK of 6.5 on the acid side of the pH profile, and the $V/K_{TNB}$ is pH independent. As compared with the wild type enzyme, the pKs in the V/K profiles are shifted, reflecting that binding of the cofactor in free E:OAS is less asymmetric.

• Bulletin of the Korean Chemical Society
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• v.22 no.10
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• pp.1123-1126
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• 2001

• Bulletin of the Korean Chemical Society
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• v.22 no.4
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• pp.383-387
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• 2001

The kinetics and mechanism of the reactions of thiophenyl dimethylacetates (TDA) and trimethylacetates (TTA) with benzylamines in acetonitrile are studied. The reactions are first order in both the amine and the substrate. Relatively large values of ${\beta}X(\betanuc$ = 1.1-1.5; TDA and 1.1-1.5; TTA) and ${\beta}Z({\beta}lg$ = -1.8~-2.0; DTA and -1.3~-1.6; TTA) for benzylamines, significantly large kH/kD values (=1.2-1.5; DTA and 1.2-1.5; TTA) involving deuterated benzylamines, and large ${\rho}XZ$ (=0.82; TDA and 1.05; TTA) values are interpreted to indicate stepwise acyl transfer mechanism, but with the hydrogen bonded four center type transition state for benzylamine. The relatively greater magnitudes of ${\rho}XZ$ and the secondary kinetic isotope effects involving deuterated nucleophiles are in line with the proposed mechanism.

• Journal of the Korean Chemical Society
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• v.63 no.6
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• pp.427-434
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• 2019

The role of hydrophobic residues on protein folding reaction was studied by folding kinetics measurements in conjunction with protein engineering. The HubWA, which was derived from human ubiquitin by mutating the residues at 45 (Phe to Trp) and 26 (Val to Ala), was used as a mutational background. Fourteen hydrophobic residues were mutated to alanine. Among fourteen variants generated, only four variant proteins (V5A, I13A, V17A, and I36A) were suitable for folding study. The folding kinetics of these variants was measured by stopped-flow fluorescence spectroscopy. The folding kinetics of HubWA and V17A was observed to follow a three-state on-pathway mechanism. On the other hand, folding kinetics of V5A, I13A, and I36A was observed to follow a two-state mechanism. Based on these observations, transition of protein folding reaction from collision-diffusion mechanism to nucleation-condensation mechanism was discussed.

• The Korean Journal of Zoology
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• v.32 no.2
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• pp.134-141
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• 1989

The present investigation aims at elucidating a possible mechanism of heat inactivation of SCK ceils by comparing the kinetics of cell lethality and protein degradation in the presence of heat protector or heat sensitizer. The effect of heat sensitizer and protector was exhibited in both cell survival and protein degradation kinetics, the magnitude of the effect being much profound for the protector compared to the sensitizer. A conclusion to he drawn from the present experiment is that there is no direct correlation between cell lethality and protein degradation. Rather, protein degradation, which might occur in the membrane, causes cell inactivation indirectly, possibly by altering the cellular environment. Accordingly, further studies are needed to get insight into the mechanism of cell inactivation by hyperthermia.