• Journal of the Korean Chemical Society
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• v.28 no.6
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• pp.418-424
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• 1984

Rate constants for the hydrolysis of cinnamonitrile in the concentration range of 1 ∼ 5M of perchloric acid at 25$^{\circ}$C have been determined by UV spectrophotometry and from the Bunnett equations, hydration parameters (${\omega}$ = 9.8, ${\omega}^*$ = 0.42 & ${\phi}$=1.6) were obtained. CNDO/2 MO calculations were performed to determine relative stability, net charges, and overlap population of various conformational isomers. The results show that the (E)-planar is more stable than the (Z)-planar and protonation is favored on the nitrogen atom. On the basis of above findings, the acid hydrolysis is initiated by the protonation of the nitrogen atom of cinnamonitrile and then water molecule acting as nucleophile and as a proton transfer agent in the rate determining step. In the transition state of the acid hydrolysis, nucleophilic addition of water molecule occurs by sigma approach to the positively charged $C_7({\alpha}$) atom of the conjugate acid. As the results, we may conclude that the hydrolysis of cinnamonitrile in the strong acidic media proceeds through the A-2 type mechanism.

• Journal of the Korean Chemical Society
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• v.44 no.2
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• pp.120-126
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• 2000

The rate constants for the hydrolysis of 2-phenyl-4H,5H-3-methyl-3-thiazolinium perchlorate(PTP) derivatives were detemined by the use of ultraviolet visible spectrophotometer in water. The rate equations which could be applied over a wide pH ranges were obtained. On the basis of rate equation, hydrolysis product analysis, general base catalysis, and substituent effect, a plausible mechanism of the hydrolysis is proposed: Below pH 4.0, the reaction is initiated by addition of water, while above pH 9.0, Michael type nucleophilic addition takes place. In the pH range of $4.5{\sim}8.0$, these two reactions appear to occur competitively.

• Korean Journal of Medicinal Crop Science
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• v.26 no.2
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• pp.127-133
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• 2018

Background: The demand of recycling renewable agricultural by-products is increasing. Radiation breeding is a method used to improve saccharification efficiency. Thus, we investigated the effect of gamma ray irradiation on the pretreatment and enzymatic hydrolysis of the stalks of Senna tora, an important medicinal plants. Methods and Results: S. tora seeds were irradiated with gamma ray at doses of 100, 200, 300, and 400 Gy. In the pretreated biomass, glucan and lignin content were higher in the M1 ($1^{st}$ generations of irradiation) S. tora stalks than in the M2 ($2^{nd}$ generations of irradiation) stalks, this can be explained by the higher degradation rate in M1. After oxalic acid pretreatment, the concentration of total phenolic compounds (TPCs) in the hydrolysate increased in the gamma ray treated seeds. The highest relative increase rate in crystallinity in the pretreated biomass was observed in M1-400 Gy and M2-100 Gy. The cellulose conversion rate was higher in M1 than in M2, except for 200 Gy. Conclusions: Gamma ray irradiation at an appropriate dose can be used to improve the efficiency of pretreatment and enzymatic hydrolysis, thereby increasing biomass availability.

• BMB Reports
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• v.36 no.2
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• pp.196-200
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• 2003

Previously, we reported the biochemical properties of RGA1 that is expressed in Escherichia coli (Seo et al., 1997). The activities of RGA1 that hydrolyzes and binds guanine nucleotide were dependent on the $MgCl_2$ concentration. The steady state rate constant ($k_{cat}$) for GTP hydrolysis of RGA1 at 2 mM $MgCl_2$ was $0.0075{\pm}0.0001\;min^{-1}$. Here, we examined the effects of pH and cations on the GTPase activity. The optimum pH at 2 mM $MgCl_2$ was approximately 6.0; whereas, the pH at 2 mM $NH_4Cl$ was approximately 4.0. The result from the cation dependence on the GTPase (guanosine 5'-triphosphatase) activity of RGA1 under the same condition showed that the GTP hydrolysis rate ($k_{cat}=0.0353\;min^{-1}$) under the condition of 2mM $NH_4Cl$ at pH 4.0 was the highest. It corresponded to about 3.24-fold of the $k_{cat}$ value of $0.0109\;min^{-1}$ in the presence of 2 mM $MgCl_2$ at pH 6.0.

• Journal of the Korean Chemical Society
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• v.38 no.4
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• pp.265-270
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• 1994

The aquation and base hydrolysis of [Co(en)$_2$NH$_3$Cl]$^{2+}$ were studied by UV spectroscopic method in various SDS aqueous solution. The base hydrolysis of [Co(en)$_2$NH$_3$Cl]$^{2+}$ with the addition of 0, 0.05, 0.1 mol dm$^{-3}$ sodium chloride was studied. For the aquation of the complex, the rate constant in the micellar phase(kH$^M$) was a little larger than that in the aqueous phase(kH$^W$). With the increase of SDS concentration, the second order rate constant(kOH) for the base hydrolysis unchanged below the CMC and sharply decreased down to a limiting value after the CMC was reached. The effect of added NaCl on the rate behavior of the complexes in the micellar solution were investigated by using an ion-exchanged model.

• Journal of the Korean Chemical Society
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• v.22 no.1
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• pp.30-36
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• 1978

The kinetics of hydrolysis of ${\alpha}$-nitrobenzaldehydephenylhydrazone derivatives (p-$NO_2$, m-$NO_2$, p-Cl, p-$CH_3$) have been investigated by UV spectrometry in 25% dioxane-water at $25^{\circ}C$ and a rate equation which can be applied over wide pH range was obtained. From the rate equation and the effect of solvent, substituent and pKa on the rate equation, the following reaction mechanisms were proposed. Below pH 3.0 the hydrolysis of ${\alpha}$-nitrobenzaldehydephenylhydrazone proceeds by $S_N1$ mechanism, while above pH 4.0 the hydrolysis proceeds through 1,3-dipole ion mechanism. In the range of pH from 3.0 to 4.0 these two reactions occur competitively.

• Journal of Microbiology and Biotechnology
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• v.6 no.3
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• pp.179-183
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• 1996

Synergism among endo-xylanase, $\beta$-xylosidase, and $\alpha$-L-arabinofuranosidase from Bacillus stearothermophilus upon xylan hydrolysis was investigated by using birchwood, oat spelt, and arabinoxylan as substrates. Endo-xylanase and $\beta$-xylosidase showed the cooperative action on all three substrates tested, revealing the fact that $\beta$-xylosidase assists endo-xylanase action in xylan hydrolysis by relieving the endproduct inhibition upon endo-xylanase conferred by xylooligomers. $\alpha$-L-Arabinofuranosidase also exhibited synergic effects with endo-xylanase and $\beta$-xylosidase on oat spelt and arabinoxylan, which contained significant amounts of arabinose side chains, whereas no synergism was detected on birchwood xylan which had only trace amounts of the side chain. Thus, the hydrolysis of xylan containing arabinose side chains required $\alpha$-L-arabinofuranosidase as well as endo-xylanase and $\beta$-xylosidase for the better hydrolysis of the substrates, and these enzymes work cooperatively in order to maximize the extent and rate of xylan hydrolysis.

• The Korean Journal of Food And Nutrition
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• v.11 no.4
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• pp.394-401
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• 1998

In present work, the development of processing for various fermented sea foods using low-usefulness marine resources were investigated. The optimum temperatures of autolysis were 35$^{\circ}C$ for hair tail, 45$^{\circ}C$ for gizzard shad, 30$^{\circ}C$ for kangdale, 30$^{\circ}C$ for pen shell and 30$^{\circ}C$ for oyster and when alcalse(Novo Co.) were added, optimum temperatures were 60$^{\circ}C$, 50$^{\circ}C$, 50$^{\circ}C$, 50$^{\circ}C$ and 50$^{\circ}C$, respectively, and protease N, P. (Pacific chem. enzyme mixture 2,000) were 55$^{\circ}C$, 60$^{\circ}C$, 50$^{\circ}C$, 50$^{\circ}C$ and 50$^{\circ}C$, respectively. Especially although exozymes and endozymes reacted at same time, hydrolysis rate of raw materials got to maximum at optimum temperatures of exozymes. The facts showed that exozymes dominated the hydrolysis reached max8imum at pH 9.0, and optimum hydrolysis time of all raw materials were 6 hours. And the optimum concentrations of exozymes were about 3.0% for hair tail, 4.5% for gizzard shad, 3.5% for kangdale, 3.0% for pen shell and 3.0% for oyster, respectively.

• Macromolecular Research
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• v.10 no.2
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• pp.122-126
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• 2002

A molecularly imprinted polymer (MIP) having both amidine and imidazole functional groups in the active site has been prepared using p-nitrophenyl phosphate as a transition state analogue (TSA). The imprinted polymer MIP with amidine and imidazole found to have the highest hydrolysis activity compared with other MIPs with either amidine or imidazole groups only. It is postulated a cooperative effect between amidine and imidazole in the hydrolysis of p-nitrophenyl methyl carbonate (NPMC) as a substrate when both groups were arranged in proximity by molecular imprinting. The rate enhancement of the hydrolysis by MIP was 60 folds over the uncatalyzed solution reaction and two folds compared with the control non-imprinted polymer CPI having both functional groups. The enzyme-mimetic catalytic hydrolysis of p-nitrophenyl acetate by MIP was evaluated in buffer at pH 7.0 with $K_{m}$ of 1.06 mM and $k_{cat}$ of 0.137 $h^{-1}$ . . .

• Bulletin of the Korean Chemical Society
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• v.26 no.7
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• pp.1037-1043
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• 2005

Kinetic study on the cleavage of N-methylphthalamic acid (NMPA) in mixed acidic aqueous-acetonitrile solvent reveals the formation of both phthalic anhydride (PAn) (through O-cyclization) and N-methylphthalimide (NMPT) (through N-cyclization). The formation of NMPT varies from $\sim$20% to $\sim$3% with the increase in the content of acetonitrile from 2 to 70% v/v. Pseudo first-order rate constants for the formation of PAn are more than 4-fold larger than those for the formation of NMPT at 2% v/v $CH_3CN$ in mixed aqueous solvents. Pseudo first-order rate constants for alkaline hydrolysis of NMPT reveal a nonlinear decrease with increase in the content of $CH_3CN$ in mixed aqueous solvents.