• BMB Reports
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• v.33 no.3
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• pp.228-233
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• 2000

The steady-state investigation of the mechanism of Dhydroxyisovalerate dehydrogenase was performed in order to understand this type of kinetic patterns. The initial velocity was measured with various amounts of both substrates, NADPH and 2-ketoisovalerate. Double reciprocal plots gave patterns that conversed on or near the abscissa. Binding studies indicated that NADPH bound first to the enzyme. The product $NADP^+$ was found to be a competitive inhibitor with respect to NADPH at a constant concentration of 2-ketoisovalerate. However, it showed noncompetitive inhibition against 2-ketoisovalerate at a fixed amount of NADPH. Another product, D-hydroxyisovalerate, was a non-competitive inhibitor versus NADPH and 2-ketoisovalerate at constant levels of 2-ketoisovalerate and NADPH, respectively. These results were comparable with an ordered bi-bi mechanism, in which NADPH bound first to the enzyme, followed by the binding of 2- ketoisovalerate. $NADP^+$ is the last product to be released. The ordered reaction manner of D-hydroxyisovalerate dehydrogenase from 2-ketoisovalerate to D-hydroxyisovalerate allows the accurate regulation of valine metabolism and it may lead to the regulation of total biosynthesis of enniatins in the Fusarium species.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.3
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• pp.179-184
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• 1982

The behavior of continuous flow culture of Lartobacillus bulgricus was investigated by application of Monod's kinetic model. The parameters obtained from Monod's chemostat theory successfully predicted the behavior of the chemostat. Then, it was found that Monod's kinetics were applicable to the growth rate dependence on glucose concentration. Under steady-state condition, the maximum growth rate, saturation constant, and wash out were found to be 0.62/hr, 7.69 g/1, 0.51/hr of continuous culture. And the optimum condition for the highest cell production was 0.41/hr in dilution rate, and at that point the cell production rate was 0.178g/1 hr.

• Bulletin of the Korean Chemical Society
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• v.23 no.10
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• pp.1459-1462
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• 2002

The kinetics of the addition of X-substituted benzylamines (BA) to Y-substituted Benzylideneacetylacetones (BAA) have been investigated in acetonitrile at $25.0^{\circ}C$. The reaction is studied under pseudo-first-order conditions by keeping a large excess of BA over BAA. The addition of BA to BAA occurs in a single step in which the addition of BA to $C_\alpha$ of BAA and proton transfer from BA to $C_\beta$ of BAA take place concurrently with a four-membered cyclic transition state structure. The magnitude of the Hammett ($p_X$) and Bronsted ($\beta_x$) coefficients are rather small suggesting an early tansition state (TS). The sign and magnitude of the cross-interaction constant, $p_{XY}$ (= -0.49), is comparatible to those found in the normal bond formation processes in the $S_N2$ and addition reactions. The normal kinetic isotope effect ($K_H/K_D$ > 1.0) and relatively low $\Delta$H^{${\neq}$}$ and large negative $\Delta$S^{${\neq}$}$ values are also consistent with the mechanism proposed.

• Bulletin of the Korean Chemical Society
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• v.6 no.4
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• pp.196-202
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• 1985

A Very Low Pressure Reactor (VLPR) is constructed for the kinetic study of atom-molecule bimolecular elementary reactions. The basic principles and the versatility of the method are described. By using the VLPR technique the forward (k1) and the reverse (k-1) rate constants for Br atom reaction with trimethylsilane are studied; Br + $(CH_3)_3$SiH k1 ${\leftrightarrow}$ k-1 HBr + $(CH_3)_3$Si. From the kinetic data and the entropy estimation the bond dissociation energy for Si-H bond in trimethylsilane is calculated to be 90.1 kcal/mole $({\pm}1.1$ kcal/mole). The Arrhenius parameters for k1 are found to be log A = 10.6 l/mole·sec, $E_a$ = 4.4 kcal/mole respectively. For the comparison purpose analogous reaction for carbon compound ; Br + $(CH_3)_3$CH ${\rightarrow}$ HBr + $(CH_3)_3$C was also studied. The corresponding rate constant and equilibrium constant at $25^{\circ}C$ are found to be 2.67 ${\times}$ $10^6l$/mole${\cdot}$sec and 160 respectively.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1539-1542
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• 2011

The aminolysis of O-methyl S-aryl thiocarbonates with benzylamines are studied in acetonitrile at -45.0$^{\circ}C$. The ${\beta}_X$(${\beta}_{nuc}$) values are in the range 0.62-0.80 with a negative cross-interaction constant, ${\rho}_{XZ}$ = -0.42, which are interpreted to indicate a concerted mechanism. The kinetic isotope effects involving deuterated benzylamine nucleophiles ($XC_6H_4CH_2ND_2$) are large, $k_H/k_D$ = 1.29-1.75, suggesting that the N-H(D) bond is partially broken in the transition state by forming a hydrogen-bonded four-center cyclic structure. The concerted mechanism is enforced by the strong push provided by the MeO group which enhances the nucleofugalities of both benzylamine and arenethiolate from the putative zwitterionic tetrahedral intermediate.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.173-184
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• 2002

In order to evaluate the devolatilization models of pulverized coal, various devolatilization models are examined for the numerical analysis of Drop Tube Furnace.The results of analysis are compared with the experimental results. A numerical study was conducted to explore the sensitivities of the predictions to variation of the model parameters. It helps to elucidate the source of the discrepancies. Three different wall temperature conditions of the DTF, 1100, 1300 and $1500^{\circ}C$ were considered in this analysis. Two fuels are U.S.A. Alaska coal and Australia Drayton coal. The results of analysis with constant rate model, single kinetic rate model and two competing rate modes well presented fast volatile matter release in the early devolatilization. However, in the latter devolatilization they did not coincide with experimental results which presented tardy volatile matter release on account of pyrolysis of high molecular substance. On the other hand, the results of analysis with DAEM(Distribute Activation Energy Model) coincided with experiment al results in overall devolatilization.

• Bulletin of the Korean Chemical Society
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• v.29 no.9
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• pp.1769-1773
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• 2008

fThe kinetics and mechanism of the reactions of Y-O-aryl phenylphosphonochloridothioates with X-pyridines are investigated in acetonitrile at 35.0 ${^{\circ}C}$. The negative value of the cross-interaction constant, $\rho$XY = −0.46, indicates that the reaction proceeds by concerted $S_N2$ mechanism. The observed $k_H/k_D$ values involving d-5 pyridine ($C_5D_5N$) nucleophiles are greater than unity (1.05-1.11). The net primary deuterium kinetic isotope effects, $(k_H/k_D)_{net}$ = 1.28-1.35, excluding the increased $pK_a$ effect of d-5 pyridine are obtained. The transition state with a hydrogen bond between the leaving group Cl and the hydrogen (deuterium) atom in the C-H(D) is suggested for the studied reaction system.

• Journal of Korean Society of Water Science and Technology
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• v.26 no.6
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• pp.143-152
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• 2018

The process parameters of ethyl violet from aqueous solution by activated carbon adsorption were carried out as a function of pH, temperature, contact time, initial concentration and temperature. The adsorption equilibrium data can be described well by the Langmuir and Freundlich isotherm models. Base on Langmuir constant ($R_L=0.0343{\sim}0.0523$) and Freundlich constant (1/n=0.1633~0.1974), This process could be employed as effective treatment for adsorption of ethyl violet. The kinetic experimental results showed that the adsorption process can be well described with the pseudo second order model. Based on the positive enthalpy (6.505 kJ/mol), the adsorption of ethyl violet onto granular activated carbon is endothermic. The negative Gibbs free energy (-1.169~-1.681 kJ/mol) obtained indicates that the adsorption process is spontaneous and physisorption.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.753-757
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• 2014

The nucleophilic substitution reactions of Y-aryl N,N-dimethyl phosphoroamidochloridates with substituted anilines and deuterated anilines are kinetically investigated in acetonitrile at $65.0^{\circ}C$. A stepwise mechanism with a rate-limiting leaving group departure from the intermediate is proposed based on the positive ${\rho}_{XY}$ value. The deuterium kinetic isotope effects involving deuterated anilines show secondary inverse with all the nucleophiles, rationalized by a dominant backside nucleophilic attack.

• Bulletin of the Korean Chemical Society
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• v.19 no.12
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• pp.1334-1336
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• 1998

Kinetic studies are carried out on the reactions of 2-chloro-2-propen-1-yl arenesulfonates with anilines and N,N-dimethylanilines in acetonitrilile at 45.0 ℃. The 2-chloro substituent is found to deactive the allyl moiety with considerable decrease in the rates. The sign and magnitude of the cross-interaction constant (ρxz 0.3) and the inverse secondary kinetic isotope effect (kH/kD 0.92) support an SN2 mechanism with a relatively tight transition state. The possibility of an SN2' mechanism can be safely precluded based on the ρxz values observed.