• Animal cells and systems
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• v.1 no.4
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• pp.647-651
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• 1997

We have used a transient expression assay employing Drosophila S2 cells to study the transcriptional repression activity of a 27 amino acid residue-long repression domain FS1 which was generated by a frame-shift in a pair-rule gene, even-skipped of Drosophila melanogaster. In an attempt to define a minimal requirement for the repression activity, we constructed a series of truncation mutant forms of the FS1, fused to a heterologous GAL4 DNA-binding domain, and measured their activities. All of the mutant forms, including the GAL4-FS1 (5-23) which retains the smallest number (19) of amino acid residues of FS1, were found to repress an initiator, a minimal TATA-lacking promoter, in a GAL4-binding-site-dependent manner. These findings suggest that a 19 amino acid residue-long region, rich in proline and leucine residues, is a transcriptional repression domain and may interact with the general transcription machinery.

• Korean Journal of Veterinary Research
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• v.46 no.3
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• pp.291-294
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• 2006

$Parallux^{TM}$, a solid-phase fluorescence immunoassay(SPFIA) developed for antibiotics residue detection in milk, was applied for analysis of fish muscle. The recommended therapeutic dose of ampicillin(100 mg/kg body weight, withdrawal period 7 days) was orally administered to a group of 25 olive flounders(Paralichthys olivaceus) for consecutive five days. Muscle was sampled after drug treatment 1st, 2nd, 3rd, 4th and 5th day. The concentration of ampicillin in muscle, determined by SPFIA, was compared with that of internal standard(10 ppb as ampicillin). The absorbance ratio of sample to internal standard(Bs/Bo) was employed as an index to determine the muscle residue in olive flounder. To investigate the recovery rate, the standard solutions were added to muscle samples to give final concentrations in muscle of 10 and 50 ng/ml. The recovery rates of all spiked samples were > 89% of the spiked value. Ampicillin was detected in muscle of fishes treated until the 3rd day of withdrawal period. The present study showed that the SPFIA can be easily adopted in predicting tissue residues for ampicillin in farmed fishes.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2877-2883
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• 2010

The folding kinetics of $WT^*$ ubiquitin variant with valine to alanine mutation at sequence position 26 (HubWA) was studied by stopped-flow fluorescence spectroscopy. While unfolding kinetics showed a single exponential phase, refolding reaction showed three exponential phases. The semi-logarithmic plot of urea concentration vs. rate constant for the first phase showed v-shape pattern while the second phase showed v-shape with roll-over effect at low urea concentration. The rate constant and the amplitude of the third phase were constant throughout the urea concentrations, suggesting that this phase represents parallel process due to the configurational isomerization. Interestingly, the first and second phases appeared to be coupled since the amplitude of the second phase increased at the expense of the amplitude of the first phase in increasing urea concentrations. This observation together with the roll-over effect in the second folding phase indicates the presence of intermediate state during the folding reaction of HubWA. Quantitative analysis of Hub-WA folding kinetics indicated that this intermediate state is on the folding pathway. Folding kinetics measurement of a mutant HubWA with hydrophobic core residue mutation, Val to Ala at residue position 17, suggested that the intermediate state has significant amount of native interactions, supporting the interpretation that the intermediate is on the folding pathway. It is considered that HubWA is a useful model protein to study the contribution of residues to protein folding process using folding kinetics measurements in conjunction with protein engineering.

• YAKHAK HOEJI
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• v.41 no.6
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• pp.756-764
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• 1997

Ile-224 in I269S mutant horse liver alcohol dehydrogenase isoenzyme S (HLADH-S) was mutated to serine by site-directed mutagenesis in order to study the role of the residue in c oenzyme binding to the enzyme. The specific activity of the I269S and I224S mutant enzyme to ethanol was increased 6-fold and all Michaelis constants($K_a,\;K_b,\;K_p,\;and\;K_q$,/TEX>) were larger than those for the wild-type and I269S enzyme. The substitution decreased the afffinity to coenzymes and increased the specific activity of the enzyme. The mutant enzyme showed the highest catalytic efficiency for octanol among the primary alcohols. But it didn`t have activities on retinoids and 5${\beta}$-cholanic acid-3-one. From these results, it was confirmed that the hydrophobic interaction of Ile-224 residue with coenzyme was related to coenzyme affinity in ADH reaction. The substitution also affected the substrate affinities to the enzyme.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.4169-4172
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• 2012

To elucidate the roles of cysteine residues in rice Phi-class GST F3, in this study, all three cysteine residues were replaced with alanine by site-directed mutagenesis in order to obtain mutants C22A, C73A and C77A. Three mutant enzymes were expressed in Escherichia coli and purified to electrophoretic homogeneity by affinity chromatography on immobilized GSH. The substitutions of Cys73 and Cys77 residues in OsGSTF3 with alanine did not affect the glutathione conjugation activities, showing non-essentiality of these residues. On the other hand, the substitution of Cys22 residue with alanine resulted in approximately a 60% loss of specific activity toward ethacrynic acid. Moreover, the ${K_m}^{CDNB}$ value of the mutant C22A was approximately 2.2 fold larger than that of the wild type. From these results, the evolutionally conserved cysteine 22 residue seems to participate rather in the structural stability of the active site in OsGSTF3 by stabilizing the electrophilic substrates-binding site's conformation than in the substrate binding directly.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.113-119
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• 2014

Due to the development of the petroleum refining technology and continuously increased demand from markets, a quantity of gasoline and diesel oil produced from a restricted quantity of crude oil has been increasing, and residual fuel to be used at marine diesel engines has been gradually becoming low quality. As a result, it was recently reported that trouble oils which cause abnormal combustion such as knocking with extreme noise and misfire from internal combustion engines were increasing throughout the world. In this study, an author investigated ignitability and combustion quality by using combustion analyzer with constant volume(FCA, Fuel Combustion Analyzer) and middle speed diesel engine about MDO(Marine Diesel Oil), HFO(Heavy Fuel Oil), LCO(Light Cycle Oil) and Blend-HFO which was blended LCO of 1000 liters with HFO of 600 liters. Moreover, for betterment of ignitability and combustion quality of injected fuels, multi-injection experiment was carried out in the diesel engine using Blend-HFO. According to the results of FCA analysis, ignitability and combustion quality was bad in the order of MDO

• Toxicological Research
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• v.25 no.1
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• pp.41-45
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• 2009

This study was conducted to monitor the level of bifenthrin residues in pear sprayed with 2% bifenthrin wettable powder (WP) at the recommended rate at four different schedules prior to harvest. The target analyte was extracted with acetone, partitioned into dichloromethane, and then purified by florisil chromatographic column. The residue determination was performed on a DB-5 capillary column using GC with electron capture detector (ECD). Linearity of this method was quite good ($r^2$ = 0.9951) in the concentration ranged from 0.2 mg/kg to 10 mg/kg. Recovery test was carried out at two concentration levels, 0.2 mg/kg and 1.0 mg/kg, in three replicates, and their rates were from 82.9% to 107.2%. No quantitative bifenthrin was detected in pear of all kinds of treatments including the treatment sprayed 4 times until 7 days before harvest. This sensitive and selective method can be used to monitor the trace residual amounts of bifenthrin in pear in a quite low concentration level.

• Korean Journal of Veterinary Service
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• v.44 no.3
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• pp.125-131
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• 2021

Benzimidazole is an widely used anthelmintics in livestock clinics. The aim of present study was to investigate benzimidazole residues in the meat in Sejong City. A total of 338 samples of meat(beef 287, pork 37, chicken 14) were selected from the laboratory meat(Korean beef genetic test, hygiene test) supplied to school in Sejong City. Representative benzimidazole class drug such as thiabendazole, 2-amino albendazole sulfone, fenbendazole, oxfendazole, and oxfendazole sulfone were monitored in samples by using lc-ms/ms and the analysis was preformed based on the Korea Food Code guideline. Limit of quantitation (LOQ) was ranged from 0.56 to 3.02 ppb for target drugs and the accuracy was within the acceptance criteria. Among the sample analyzed only one case, the pork meat was found to have drug levels that exceed LOQ. However, the overall residue concentration was 2.17 ppb, which was lower than the maximum residue levels (100 ppb).

• Korean Journal of Materials Research
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• v.28 no.11
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• pp.627-632
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• 2018

Two dimensional(2D) crystals, composed of a single layer or a few atomic layers extracted from layered materials are attracting researchers' interest due to promising applications in the nanoelectromechanical systems. Worldwide researchers are preparing devices with suspended 2D materials to study their physical and electrical properties. However, during the fabrication process of 2D flakes on a target substrate, contamination occurs, which makes the measurement data less reliable. We propose a dry transfer method using poly-methyl methacrylate(PMMA) for the 2D flakes to transfer onto the targeted substrate. The PMMA is then removed from the device by an N-Methyl-2-pyrrolidone solution and a critical point dryer, which makes the suspended 2D flakes residue free. Our method provides a clean, reliable and controllable way of fabricating micrometer-sized suspended 2D nanosheets.

• Journal of Preventive Veterinary Medicine
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• v.42 no.4
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• pp.171-176
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• 2018

A study of the tissue depletion of florfenicol (FFC) administered orally to pigs at a dose of 0.05 kg/ton feed for 7 days was performed. Sixteen healthy cross swine were administered with FFC. Four treated animals were arbitrarily selected to be sacrificed 1, 3 and 5 days after the end of treatment. FFC residue concentrations in muscle, liver, kidney, and fat were determined using high-performance liquid chromatography (HPLC) with ultraviolet photometric detector at 230 nm. The correlation coefficient ($R^2$) of the calibration curve for florfenicol amine (FFCa) was > 0.997 and the limits of detection and quantification were 0.012 and $0.040{\mu}g/mL$, respectively. Recovery rates in swine edible tissues ranged from 79.1 to 93.5%. In the FFC-treated group, FFC residues at 3 days post-treatment were below the maximum residue limits (MRLs) in muscle, kidney and fat, and those at 5 days post-administration were below the MRLs in all edible tissues. These results suggest that the withdrawal period of FFC after the drug treatment might be 5 days, which is a sufficient amount of time for reduction of the FFC residues below the MRLs in all edible tissues.