• Journal of the Korean Chemical Society
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• v.36 no.4
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• pp.565-578
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• 1992

It has been suggested that Hg$^{2+}$-promoted reaction of a series of cis-[Co(en)$_2$(L)Cl]$^{2+}$ (en = 1,2-diaminoethane) with L = NH$_3$, NH$_2$CH$_3$, glyOC$_2$H$_5$, glyOCH$_3$, dl-alaOC$_2$H$_5$, NH$_2$CH$_2$CONH$_2$, and NH$_2$CH$_2$CN proceeds by dissociative interchange(I$_d$) mechanism from kinetic data, circular dichroism spectra, analyses of products, and the values of m(Grunwald-Winstein plot) using Y (solvent ionizing power) in aqueous solution and in mixed aqueous-organic solvent. It has been found that chloride replacement by water (aquation) for the series with L = NH$_3$ and NH$_2$CH$_3$ and chelation of ligand L to Co(Ⅲ) for the series with L = glyOC$_2$H$_5$, glyOCH$_3$, dl-alaOC$_2$H$_5$, NH$_2$CH$_2$CONH$_2$, and NH$_2$CH$_2$CN occurs, respectively. The rate constants on Hg$^{2+}$-induced reaction of the series except cis-[Co(en)$_2$(NH$_2$CH$_2$CN)Cl]$^{2+}$ were increased with increasing the contents of ethanol in mixed water-ethanol solvents. In mixed water-30${\%}$ organic solvents, the rate constants of the series except cis-[Co(en)$_2$(NH$_2$CH$_2$CN)Cl]$^{2+}$ have also been measured in the order 30${\%}$ 2-propanol-water > 30${\%}$ ethanol-water > water. However, the rate constants of cis-[Co(en)$_2$(NH$_2$CH$_2$CN)Cl]$^{2+}$ were reversed. The rate constants of the series with L= NH$_3$ and NH$_2$CH$_3$ were related to ligand field parameter (${\Delta}$), but those of the series with L = glyOC$_2$H$_5$, glyOCH$_3$, dl-alaOC$_2$H$_5$, NH$_2$CH$_2$CONH$_2$, NH$_2$CH$_2$CN were not. The reaction between the series and Hg2+ in aqueous media containing NO$_3^-$ has been investigated. The results for the reaction do not alter the mechanism, but the rate only was altered.

• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.346-353
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• 2011

Base hydrolysis of 7-hydroxy-2H-chromen-2-one (HC) and 7-hydroxy-2H-chromen-2-one-4-acetic acid (HCA) in aqueous-methanol and aqueous-acetone mixtures were studied kinetically at temperature range from 283 to 313 K. The activation parameters of the reactions were evaluated and discussed. Moreover, the change in the activation energy barrier of the investigated compounds from water to water-methanol and water-acetone mixtures was estimated from the kinetic data. It is observed that the change in activation barriers is more or less the same for the hydrolysis of HC and HCA. Base hydrolysis of HC and HCA follows a rate law with $k_{obs}=k_2[OH^-]$. The decrease in the rate constants of HC and HCA as the proportion of methanol or acetone increases is due to the destabilization of $OH^-$ ion. The high negative values of entropy of activation support the proposal mechanism, i.e. the investigated reaction takes place via the formation of an intermediate complex. Moreover, these values refer to the rigidity and stability of the intermediate complex. Thus, the ring opening of the intermediate complex would be the rate controlling step.

• Journal of the Korean Society of Food Science and Nutrition
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• v.11 no.3
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• pp.21-27
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• 1982

A kinetical approach for the non-enzymatic browning reaction of the dried file-fish was studied. The reaction rates revealed a tend to increase with increasing water activity and showed the maximum at $0.75\;a_w$ The activation energies obtained from the Arrhenius plot ranged 12.5 to 16.5 Kcal/mole. From these energies of activation, the $Q_{10}$ values at $45^{\circ}C$ showed 1.9 to 2.3 and both activation energy and $Q_{10}$ values were reduced with increase in $a_w$ Shelf-lives, the time to reach an 0.15 O.D./g solid at which severe brown color change could be de ectable, decreased rapidly as the temperature and water activity increase. A storage study under a square-wave fluctuating temperature condition (at 35 and $55^{\circ}C$ periodically with 7 days interval), the rate constants at all water activities used in the experiments were higher than those at $45^{\circ}C$, the mean temperature of the cycle which affects other kinetic parameters including activation energies, $Q_{10}$ values and finally the shelf-lives. The data obtained from the fluctuating temperaure storage study will be used in prediction of shelf-life. The shelf lives assessed at $25^{\circ}C$ from the accelerated shelf-life tests ranged from 179 daysat $0.75\;a_w$ to 302 days at $0.44\;a_w$.

• Korean Journal of Food Science and Technology
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• v.24 no.3
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• pp.256-260
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• 1992

This study was conducted to calculate and predict the shelf-life of meat sausage through physicochemical and biological analysis. Judging from physico-chemical components, it can be found out the most effective indicator in meat sausage. And also, the materials used for packaging is cellulose #23 in inner-packaging and CN/HDPE laminating film in outer-packaging. The changes of the most effective indicator were discussed through the method of kinetic analysis. Judging from physico-chemical components, VBN was the most available component in quality judgement of meat sausage and their upper limiting contents were 20 mg%. It is possible to calculate and predict the shelf-life of meat sausage through the regression equation and $Q_{10}$ value. As a result, the shelf-life prediction was $58{\sim}63$ days at $10^{\circ}C$, $47{\sim}51$ days at $20^{\circ}C$ and 26 days at $40^{\circ}C$, respectively, but the difference between two methods showed about $4{\sim}5$ days. $Q_{10}$ value on the changes contents was 1.35 at acceralated temperature $40^{\circ}C$. The reaction rate of VBN contents could be interpreted as a first order reaction that divided into 2 periods with different reaction rate constants. The corresponding Arrhenius activation energies were 2.959 Kcal/mole and 3.632 Kcal/mole, respectively.

• Biomolecules & Therapeutics
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• v.3 no.1
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• pp.21-27
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• 1995

The only compounds with antagonistic activity via AT$_1$receptor, one of two subtypes of angiotensin II (AII) receptor, have been demonstrated to block the vasoconstriction effects of AII and thereby provide therapeutic potential. This initiated the search for compounds with high specific affinity to AT$_1$receptor and their effective screening methods. The radioligand binding assay for the AII receptor is regarded as the primary method for the evaluation of AT$_1$receptor antagonists for their activity. In this paper, we characterized the liver AT$_1$receptor and describe the efficient method of the radioligand binding assay using rat liver as a source of AT$_1$receptor. Equilibrium binding studies with rat adrenal cortex, adrenal medulla, liver and bovine adrenal showed that the specific bindings of [$^3$H] AII were saturable in all tissues and the Scatchard plots of those data were linear, suggesting a single population of binding sites. Hill slopes were very near to the unity in all tissues. Kinetic studies of [$^3$H) AII binding in rat liver homogenates yielded two association rate constants, 4.10$\times$10$^{7}$ M$^{-1}$ min$^{-1}$ and 4.02$\times$10$^{9}$ M$^{-1}$ min$^{-1}$ , with a single dissociation rate constant, 7.07$\times$10$^{-3}$ min-$^{-1}$ , possibly due to the partial dissociation phenomenon. The rank order of inhibition potencies of [$^3$H] AII binding in rat liver was AII>Sarile>Losartan>PD 123177. Rat liver homogenates revealed to have very high density of homogeneous population of the AT$_1$receptor subtype, as the specifically bound [$^3$H] AII was not inhibited by PD 123177, the nonpeptide antagonist of AT$_2$. The results of this study demonstrated that the liver homogenates from rats could be the best receptor preparation for the AT$_1$receptor binding assay and provide an efficient system for the screening of newly synthesized candidate compounds of AT$_1$receptor antagonist.

• Journal of Soil and Groundwater Environment
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• v.14 no.1
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• pp.44-50
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• 2009

The occurrence of endocrine disrupting compounds (EDCs), chemicals that interfere with human hormone system, are increasing in the freshwater, waste water and subsurface as well. In this study, we determined the reactivity of three EDCs in the presence of birnessite. In aqueous phase, bisphenol A, 2,4-dichlorophenol and 17${\beta}$-estradiol, which possesses phenoxy-OH, were very rapidly transformed by birnessite: up to 99% of initial concentrations (50 mg/L for bisphenol A, 100mg/L for 2,4-dichlorophenol, and 1.5mg/L for 17${\beta}$-estradiol) were destroyed within 60 minutes. Especially, bisphenol A was the most reactive chemical, disappearing by 99% in a few minutes. The reaction occurred on the surface of birnessite, showing a linear increase of first-order kinetic constants with the increase of the surface area of birnessite. In soil slurry phase, the reactivity of birnessiteto EDCs was faster than in aqueous phase probably due to the cross coupling reaction of phenoxy radicals with soil organic matter. Considering the rapid transformation of the EDCs in the both phases, this oxidative cross coupling reaction mediated by birnessite would be an effective solution for the remediation of EDCs in environmental media, especially in soil.

• Journal of Soil and Groundwater Environment
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• v.12 no.2
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• pp.1-8
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• 2007

A series of batch and column experiments were conducted for the development of biobarrier technology which can be applied to containment and reduction of contaminants in soil and ground waters. The growth kinetic constants of Pseudomonas fluorescens on glucose or molasses were determined using batch experiments. The maximum specific growth rate (Vmax) of P. fluorescens at $23^{\circ}C$ on glucose or molasses were $0.246\;hr^{-1}$ and $0.073\;hr^{-1}$, respectively. However, molasses was selected as carbon source due largely to the absence of lag phase of P. fluorescens growth on molasses and economic reason. In constant head column experiments, the hydraulic conductivity of the column soil reduced by $6.8{\times}10^{-3}$ times from $4.1{\times}10^{-2}cm/sec$ to $2.8{\times}10^{-4}cm/sec$ after the inoculation of P. fluorescens and administration of carbon source and nutrients. The biomass concentration was observed highest in the column inlet. Measurements of carbon source and electron accepter (dissolved oxygen) concentration showed that the growth of P. fluorescence, which is the main reason for hydraulic conductivity reduction, was limited not by the concentration of carbon source but by the concentration of electron acceptor.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.11
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• pp.989-996
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• 2009

In this study, the effects of biofilter media type (three different activated carbons and anthracite), empty bed contact time (EBCT) and temperature on the removal of four aldehyde species (formaldehyde, acetaldehyde, glyoxal and methylglyoxal) in BAC filters were investigated. Experiments were conducted at three water temperature (5, 15 and $25^{\circ}C$) and four EBCTs (5, 10, 15, and 20 min). The experimental results indicated that the coal based BAC retained more bacterial biomass on the surface of the activated carbon than the other BACs, and increasing EBCT or increasing water temperature also increased the four aldehyde species removal in BAC filters. To achieve above 80% of removal efficiency for four aldehyde species in a BAC filter, above 15 min EBCT at $5^{\circ}C$ and 10 min EBCT at above $15^{\circ}C$ were required. The kinetic analysis indicated a first-order reaction rate for the biodegradation of four aldehyde species at various water temperatures. Data obtained from the BAC filters at various temperatures were also used to evaluate pseudo first-order rate constants for four aldehyde species. The half-lives evaluated for formaldehyde, acetaldehyde, glyoxal and methylglyoxal in the coal-based BAC ranging from 0.89 to 3.19 min, from 0.75 to 3.35 min, from 2.16 to 4.72 min and from 1.49 to 3.86 min, respectively, could be used to assist water utilities in designing and operating BAC filters.

• Journal of Microbiology and Biotechnology
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• v.21 no.10
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• pp.1012-1020
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• 2011

A gene coding for an endoglucanase (EglA), of the glycosyl hydrolase family 12 and derived from Aspergillus niger VTCC-F021, was cloned and sequenced. The cDNA sequence, 717 bp, and its putative endoglucanase, a 238 aa protein with a predicted molecular mass of 26 kDa and a pI of 4.35, exhibited 98.3-98.7% and 98.3-98.6% identities, respectively, with cDNA sequences and their corresponding endoglucanases from Aspergillus niger strains from the GenBank. The cDNA was overexpressed in Pichia pastoris GS115 under the control of an AOX1 promoter with a level of 1.59 U/ml culture supernatant, after 72 h of growth in a YP medium induced with 1% (v/v) of methanol. The molecular mass of the purified EglA, determined by SDS-PAGE, was 33 kDa, with a specific activity of 100.16 and 19.91 U/mg toward 1% (w/v) of ${\beta}$-glucan and CMC, respectively. Optimal enzymatic activity was noted at a temperature of $55^{\circ}C$ and a pH of 5. The recombinant EglA (rEglA) was stable over a temperature range of $30-37^{\circ}C$ and at pH range of 3.5-4.5. Metal ions, detergents, and solvents tested indicated a slightly inhibitory effect on rEglA activity. Kinetic constants ($K_m$, $V_{max}$, $k_{cat}$, and $k_{cat}/K_m$) determined for rEglA with ${\beta}$-glucan as a substrate were 4.04 mg/ml, 102.04 U/mg, 2,040.82 $min^{-1}$, and 505.05, whereas they were 10.17 mg/ml, 28.99 U/mg, 571.71 $min^{-1}$, and 57.01 with CMC as a substrate, respectively. The results thus indicate that the rEglA obtained in this study is highly specific toward ${\beta}$-glucan. The biochemical properties of rEglA make it highly valuable for downstream biotechnological applications, including potential use as a feed enzyme.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.642-650
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• 2005

This research investigates the effects of adding oxidants such as $Fe^0$, $Fe^{2+}$, and ${S_2O_8}^{2-}$ in the sonolysis of 1,4-D. Results indicate that the degradation could be divided into two steps (initiation and acceleration) kinetically. The initial portion agreed with zero-order expression, while the second portion could be fitted with pseudo first-order expression. In the presence of ${HCO_3}^-$, as a radical scavenger, the degradations of 1,4-D and TOC were suppressed, indicating that OH radical is an important factor in the sonolysis. The overall degradation efficiency of 79.0% in the sonolysis was achieved within 200 minutes. While $Fe^0$, $Fe^{2+}$, and ${S_2O_8}^{2-}$ were individually combined with sonication, the degradation efficiency of 1,4-D increased 18.6%, 19.1%, and 16.5% after 200 min, respectively. The addition of oxidants not only changed the kinetic model from zero to pseudo first order at initiation step, but also increased the rate constants in the acceleration step. The addition of oxidants in the sonolysis of 1,4-D also improved the mineralization of 1,4-D, however, the effect of adding oxidants on the rate increase was similar regardless of the oxidants.