• Journal of Soil and Groundwater Environment
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• v.11 no.6
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• pp.69-75
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• 2006

Improper disposal of petroleum and spills from underground storage tanks have created large areas with highly toxic contamination of the soil and groundwater. Methyl tert-butyl ether (MTBE) is widely used as a fuel additive because of its advantageous properties of increasing the octane value and reducing carbon monoxide and hydrocarbon exhausts. However, MTBE is categorized as a possible human carcinogen. This research investigated the Modified Photo-Fenton system which is based on the Modified Fenton reaction and UV light irradiation. The Modified Fenton reaction is effective for MTBE degradation near a neutral pH, using the ferric ion complex composed of a ferric ion and environmentally friendly organic chelating agents. This research was intended to treat high concentrations of MTBE; thus, 1,000 mg/L MTBE was chosen. The objectives of this research are to find the optimal reaction conditions and to elucidate the kinetic and mechanism of MTBE degradation by the Modified Photo-Fenton reaction. Based on the results of experiments, citrate was chosen among eight chelating agents as the candidate for the Modified Photo-Fenton reaction because it has a relatively higher final pH and MTBE removal efficiency than the others, and it has a relatively low toxicity and is rapidly biodegradable. MTBE degradation was found to follow pseudo-first-order kinetics. Under the optimum conditions, [$Fe^{3+}$] : [Citrate] = 1 mM: 4 mM, 3% $H_2O_2$, 17.4 kWh/L UV dose, and initial pH 6.0, the 1000 ppm MTBE was degraded by 86.75% within 6 hours and 99.99% within 16 hours. The final pH value was 6.02. The degradation mechanism of MTBE by the Modified Photo-Fenton Reaction included two diverse pathways and tert-butyl formate (TBF) was identified to be the major degradation intermediate. Attributed to the high solubility, stability, and reactivity of the ferric-citrate complexes in the near neutral condition, this Modified Photo-Fenton reaction is a promising treatment process for high concentrations of MTBE under or near a neutral pH.

• Journal of the Mineralogical Society of Korea
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• v.25 no.2
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• pp.85-94
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• 2012

The $AsO_4$ ion in acid mine drainage has been known to substitute for $SO_4$ in schwertmannite and prevent schwertmannite from being converted to goethite. There have been studies on the heavy metal sorption on schwertmannite, but no experimental results have been reported on the characteristics of heavy metal sorption on $AsO_4$-substituted schwertmannite. In this study, we conducted sorption experiments of Cu, Pb, and Zn on the $AsO_4$-substituted schwertmannite at pH 4 and 6 in the solution of 3, 10, 30, and 100 mg/L concentrations. For all heavy metals, the sorbed heavy metals significantly increase at pH 6 compared with at pH 4. At both pH 4 and 6, Pb shows the highest sorption capacity and those of Cu and Zn are similar. With increasing time, the sorbed heavy meal contents increase too. However, in the case of Zn, the most sorptions occur at the initial stage and no significant increase is observed with time. Among the concentration ranges in which we conducted the experiment, the increasing trend is clear in high concentrated solutions such as 100 mg/L. We applied several sorption kinetic model and it shows that the diffusion process may be the most important factor controlling the sorption kinetics of Cu, Pb, and Zn on $AsO_4$-substituted schwertmannite. Considering the previous results that pure schwertmannite has similar sorption capacity for all three heavy metals at pH 6 and has higher sorption capacity for Cu and Pb than Zn at pH 4, our experiments indicates that substitution of $AsO_4$ for $SO_4$ on schwertmannite changes surface and sorption characteristics of schwertmannite. It also shows that $AsO_4$ contributes not only to the stability of schwertmannite, but also to the mobility of heavy metals in acid mine drainage.

• Journal of the Mineralogical Society of Korea
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• v.26 no.4
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• pp.229-244
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• 2013

Arsenic contamination may be brought about by a variety of natural and anthropogenic causes. Among diverse naturally-occurring chemical speciations of arsenic, trivalent (As(III), arsenite) and pentavalent (As(V), arsenate) forms have been reported to be the most predominant ones. It has been well known that the behavior of arsenic is chiefly affected by aluminum, iron, and manganese oxides. For this reason, this study was initiated to evaluate the applicability of manganese slag (Mn-slag) containing high level of Mn, Si, and Ca as an efficient sorbent of arsenic. The main properties of Mn-slag as a sorbent were investigated and the sorption of each arsenic species onto Mn-slag was characterized from the aspects of equilibrium as well as kinetics. The specific surface area and point of zero salt effect (PZSE) of Mn-slag were measured to be $4.04m^2/g$ and 7.73, respectively. The results of equilibrium experiments conducted at pH 4, 7 and 10 suggest that the sorbed amount of As(V) was relatively higher than that of As(III), indicating the higher affinity of As(V) onto Mn-slag. As a result of combined effect of pH-dependent chemical speciations of arsenic as well as charge characteristics of Mn-slag surface, the sorption maxima were observed at pH 4 for As(V) and pH 7 for As(III). The sorption of both arsenic species reached equilibrium within 3 h and fitting of the experimental results to various kinetic models shows that the pseudo-second-order and parabolic models are most appropriate to simulate the system of this study.

• Applied Biological Chemistry
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• v.47 no.4
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• pp.390-395
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• 2004

In order to characterize ion channels present in tomato roots, microsomes were incorporated into an artificial lipid bilayer arranged for electrophysiological analysis. Of the five different ion channels that could be found, a channel of 450 pS conductance was found most frequently. This channel displayed subconductance states of 450, 257 and 105 pS. All subconductance states showed linear current-voltage relationships. At positive holding potentials, high frequency of transient channel openings was observed; however, at negative potentials, the open times were long and open probability high. Po was 0.83 at -40 mV. When an additional 50 mM $K^+\;or\;Na^+$ was added to the cis side of bilayer, the reversal potentials shifted in the negative direction to near -10 mV. Thus, the 450 pS cation channel selects poorly between $K^+\;and\;Na^+$. In the presence of $100\;{\mu}M$ metal ions, the channel activity was severely inhibited by $La^{3+},\;Ba^{2+},\;and\;Zn^{2+}$, and Po was decreased to 0.2 or even less. However, $Al^{3+}\;and\;Cd^{2+}$ decreased the activity by only 20%. Interestingly, each metal ion showed different kinetics of channel inhibition. While $500\;{\mu}M\;La^{3+}$ inhibited the activities of all subconductance state, 1 mM $Zn^{2+}$ inhibited all except the 105 pS state. $Cd^{2+}$ changed the gating of the channel from a long-opening state to brief transient openings even at negative holding potentials. These data represent that the metal ions may have different binding sites on the channel protein and could be useful modulators and probes to investigate structural characteristics as well as the functional roles of the 450 pS channel on the root physiology.

• Korean Journal of Environmental Agriculture
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• v.36 no.1
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• pp.57-62
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• 2017

BACKGROUND: Pesticide residue analysis is essentially required for safety evaluation of agricultural products. Bistrifluron and chlorantraniliprole have been currently considered as potentials to deeply evaluate their residues in agricultural products because they are frequently found in strawberry. This work was performed to investigate the residual patterns of bistrifluron and chlorantraniliprole in strawberry after harvest. METHODS AND RESULTS: Strawberry was treated with bistrifluron and chlorantraniliprole 0, 1, 2, 3, 5, 7 and 10 days before harvest under greenhouse conditions. The strawberry samples were subjected to solvent and solid phase extractions followed by LC-MS/MS analysis. There covery percentages of bistrifluron and chlorantraniliprole for tified in the control samples ranged from approximately 82 to 103% with the method limit of 0.005 mg/kg. The concentrations of bistrifluron and chlorantraniliprole in strawberry samples decreased significantly in 10 days after treatment, giving the safety levels of 0.04 to 0.06 mg/kg at 10 days after application, as considered maximum residue limit. The half-lives of bistrifluron and chlorantraniliprole based on first order kinetics were determined to 6.3 days and 6.4 days, respectively. CONCLUSION: Bistrifluron and chlorantraniliprole are suggested to use in strawberry 10 days before harvest to reach residual safety levels.

• Journal of Food Hygiene and Safety
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• v.13 no.2
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• pp.143-148
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• 1998

The purpose of this study was to determine the kinetics of paralytic shellfish poison (PSP) destruction at various temperature. The toxic digestive gland homogenate of blue mussel (Mytilus edulis), PSP crude toxin, gonyautoxin group and saxitoxin group were heated at temperature ranging from 90 to $120^{\circ}C$, and then the toxicities were measured in samples heated for various time intervals. The rate constant (k) of the toxic digestive gland homogenate, PSP crude toxin, gonyautoxin group and saxitoxin group were $3.28{\times}10^{-2},\;1.20{\times}10^{-2},\;5.88{\times}10^{-2}\;and\;2.58{\times}10^{-2}\;at\;120^{\circ}C$, respectively. The decimal reduction time (D-value) of the toxic digestive gland homogenate, PSP crude toxin, gonyautoxin group and saxitoxin group were 70, 192, 39 and 89 at $120^{\circ}C$, respectively. These results indicate that PSP crude toxin is most heat-stable of 4 types of PSP toxins and PSP toxin are more heat-stable than food poisoning bacteria and spores. The retorting condition to reduce PSP toxicity below quarantine limit ($80\;\mu\textrm{g}/100\;g$ in Korea and America, 4 MU/g in Japan) could be calculated by rate constant. For example, the digestive gland homogenate having a initial toxicity of $200\;\mu\textrm{g}/100\;g$ could have toxicity below quarantine limit when heated at $90^{\circ}C$ for 129 min., $100^{\circ}C$ for 82 min., $110^{\circ}C$ for 48 min. and $120^{\circ}C$ for 28 min. These results suggest that commercial retorting condition ($115^{\circ}C$ for 70 min) in Korea is enough to reduce toxicity below quarantine limit from initial toxicity of $200\;\mu\textrm{g}/100\;g$. From these results, the quarantine limit of PSP-infested shellfish for canning can be level up to raw score of $200\;\mu\textrm{g}/100\;g$.

• Korean Journal of Environmental Agriculture
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• v.34 no.4
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• pp.268-273
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• 2015

BACKGROUND: Petroleum-contaminated soil from leaking above- and underground storage tanks and spillage during transport of petroleum products is widespread environmental problem in recent years. Application of compost may be the most promising, cost-effective, and eco-friendly technology for soil bioremediation because of its advantages over physical and chemical technology. The objective of this study was to evaluate effect of compost application on degradation of total petroleum hydrocarbon (TPH) in petroleum hydrocarbon-contaminated soil.METHOD AND RESULTS: An arable soil was artificially contaminated by diesel, and compost was applied at the different rate of 0, 10, 30, and 50 Mg/ha. Concentration of TPH in the soil decreased as application rate of compost increased. Degradation efficiency was highest at compost 30 Mg/ha; however, it slightly decreased with compost 50 Mg/ha. Kinetic modeling was performed to estimate the rates of chemical reaction. The correlation coefficient (R2) values for the linear plots using the second-order model were higher than those using the first-oder model. Compost 30 and 50 Mg/ha had the fastest TPH degradation rate in the second-order model. Change of microbial population in soil with compost application was similar to that of TPH. Microbial population in the soil increased as application rate of compost increased. Increasing microbial population in the contaminated soil corresponded to decreased in TPH concentration.CONCLUSION: Conclusively, compost application for soil bioremediation could be an effective response to petroleum hydrocarbon-contaminated soil. The increase in microbial population with compost suggested that compost application at an optimum rate might enhance degradation of TPH in soil.

• Journal of Life Science
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• v.21 no.7
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• pp.1032-1038
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• 2011

Recently identified Ciona intestinalis voltage sensor-containing phosphatase (Ci-VSP) consists of an ion channel-like transmembrane domain (VSD) and a phosphatase-like domain. Ci-VSP senses the change of membrane potential by its VSD and works as a phosphoinositide phosphatase by its phosphatase domain. In this study, we present the construction of His-tagged phosphatase-like domain of Ci-VSP, its recombinant expression and purification, and its enzymatic activity behavior in order to examine the biochemical behavior of phosphatase domain of Ci-VSP without interference. We found that Ci-VSP(248-576)-His can be eluted with an elution buffer containing 25 mM NaCl and 100 mM imidazole during His-tag purification. In addition, we found the proper measurement condition for kinetics study of Ci-VSP(248-576)-His against p-nitrophenyl phosphate (pNPP). We measured the kinetic constant of Ci-VSP(248-576)-His at $37^{\circ}C$, pH 5.0 or 5.5, under 30 min of reaction time, and less than $2.0\;{\mu}g$ of protein amount. With these conditions, we acquired that Ci-VSP(248-576)-His has $K_m$ of $354{\pm}0.143\;{\mu}M$, $V_{max}$ of $0.0607{\pm}0.0137\;{\mu}mol$/min/mg and $k_{cat}$ of $0.359{\pm}0.009751\;min^{-1}$ for pNPP dephosphorylation. Therefore, we produced a pure form of Ci-VSP(248-576)-His, and this showed a higher activity against pNPP. This purified protein will provide the road to a structural investigation on an interesting protein, Ci-VSP.

• Journal of Life Science
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• v.20 no.6
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• pp.845-852
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• 2010

Our previous study showed that lungs infected by Pseudomonas, a gram-negative bacteria, produce prostaglandin $D_2$ ($PGD_2$) and prostaglandin $E_2$ ($PGE_2$), the two major prostanoids generated by cyclooxygenase-2 (COX-2), and that the ratio of $PGD_2$ and $PGE_2$ can affect the outcome of the bacterial lung infection. In this study, we sought to uncover the mechanism that determines the ratio of $PGD_2$ and $PGE_2$ produced in lung inflammation. When treated with lipopolysaccharide (LPS), primary alveolar macrophages, extracted from mouse lung, more $PGE_2$ was produced than $PGD_2$, whereas MH-S, a murine alveolar macrophage cell line, produced more $PGD_2$ than $PGE_2$ in a similar experiment. Western blot analyses showed that the kinetics of COX-2 expression in both cell types is similar and epigenetic silencing of COX-2 expression did not affect expressions of lipocalin-PGD synthase (L-PGDS) and PGE synthase (mPGES-1), major enzymes synthesizing $PGD_2$ and $PGE_2$ in inflammation, respectively, indicating no effect of COX-2 on expressions of the two enzymes. Expressions of L-PGDS and mPGES-1 were also similar in both cell types, suggesting no effect of the two key enzymes in determining the ratio of $PGD_2$ and $PGE_2$ in these cells. A single intraperitoneal injection of LPS to C57BL/6 mice induced COX-2 expression and, similar to alveolar macrophages, produced more $PGE_2$ than $PGD_2$ in the lung. These results suggest that the differential expressions of $PGD_2$ and $PGE_2$ in the lung reflect those in alveolar macrophages and may not be directly determined by the enzymes responsible for $PGD_2$ and $PGE_2$ synthesis.

• Journal of Veterinary Clinics
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• v.21 no.4
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• pp.329-335
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• 2004

Dog spermatozoa were recovered from the caudae epididymides of 23 domestic dogs which were 11 pure breed and 12 mix-breed dogs ranging in age from 0.6 to 3 years. The experimental designs were as follows: 1) the effect of chilling to 0. 10 or 37$^{\circ}C$. 2) the kinetics of chilling injury at 0 or 4$^{\circ}C$, and 3) the effect of sugars at $0^{\circ}C$. Viable spermatozoa were recovered by percoll gradient separation and adjusted to 5${\times}$10$^{7}$ spermatozoa/ml. In experiment 1, spermatozoa were diluted with 0.33 M glucose supplemented with 3% BSA (G-BSA) at 1:2 dilution. Spermatozoa were loaded into straws and exposed at 0, 10 or 37$^{\circ}C$ for 30 min. In experiment 2, spermatozoa were prepared as the experiment 1 and exposed for 0.5, 5, 15, or 30 min at 0 or 4$^{\circ}C$. In experiment 3, spermatozoa were diluted with different sugars (0.33 M galactose, glucose, fructose, mannitol, lactose, sucrose, raffinose) and cooled to $0^{\circ}C$ for 30 min. Sperm membrane integrity, motility and acrosome integrity were assayed after rewarming at 37$^{\circ}C$ for 5 min. Sperm motility and membrane integrity abruptly decreased with decreasing temperature but acrosome integrity gradually decreased (P<0.05). Sperm motility was more sensitive to cold shock than membrane integrity and acrosome integrity. Spermatozoa cooled to $0^{\circ}C$ were more damaged than those at 4$^{\circ}C$. Sperm motility was not different among exposed times at both. 0 and 4$^{\circ}C$. However, membrane integrity of spermatozoa exposed for 30 min at both 0 and 4$^{\circ}C$ was significantly lower (P<0.05). Spermatozoa diluted in 0.33 M fructose or galactose showed lower motility and higher morphological abnormality with coiled tail at $0^{\circ}C$. These sperm characteristics were strongly related. These results indicate that dog epididymal spermatozoa are relatively sensitive to rapid cooling and higher morphological abnormality at $0^{\circ}C$ was shown in spermatozoa diluted in fructose and galactose.