• Bulletin of the Korean Chemical Society
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• v.28 no.2
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• pp.271-275
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• 2007

γ -Glutamyl transpeptidase (EC 2.3.2.2) plays a key role in glutathione metabolism by catalyzing the transfer of the γ -glutamyl residue and hydrolysis of glutathione. The functional residues at the active site of the rat kidney γ -glutamyl transpeptidase were investigated by kinetic studies at various pH, the treatment of diethylpyrocarbonate (DEPC), and photooxidation in presence of methylene blue. An ionizable group affecting the enzymatic activity with an apparent pKa value of 7.1, which is in the range of pKa values for a histidine residue in protein, was obtained by examining the pH-dependence of kinetic parameters. The pH effect on the photoinduced inactivation rate of the enzyme corresponds to that expected for the photooxidation of the free histidine. The involvement of a histidine in the catalytic site of the enzyme was further supported by DEPC modification accompanied by an increase in absorbance at 240 nm, indicating the formation of Ncarbethoxyhistidine. The histidine located at the position of 382 in the precursor of the enzyme is primarily suspected based on the amino acid sequence alignment of the transpeptidases from various organisms.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.303-307
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• 2013

This study compares the efficacy of soaking and percolation pretreatments with alkaline solutions for lignocellulosic biomass. Various biomass such as rice straw and barley were pretreated by soaking processes in various alkaline solutions including sodium hydroxide, potassium hydroxide, aqueous ammonia and sodium carbonate. The enzymatic digestibility of rice straw and barley that had been pretreated by soaking in aqueous ammonia was over 80%. Eucalyptus residue, Larix leptolepis and Pinus rigida exhibited relatively low enzymatic digestibility. Nevertheless, the enzymatic digestibility of pretreated eucalyptus residue was increased by five times compared to that of the initial biomass. And, the enzymatic digestibility of the percolation pretreated eucalyptus residue was increased 12 times.

• Korean Journal of Veterinary Service
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• v.45 no.3
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• pp.229-236
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• 2022

This study describes an analytical method based on LC-MS/MS for the quantitation of 5 fluoroquinolones (Enrofloxacin, Ciprofloxacin, Marbofloxacin, Norfloxacin and Danofloxacin) in meat, and was applied to 230 meat samples for validation. Quantitation was performed based on a matrix-matched calibration to compensate for the matrix effect on the electrospray ionization. Good linear calibrations (R²≥0.998) were obtained for all fluoroquinolones at 6 concentrations of 1~50 ㎍/kg. Satisfied recoveries of all fluoroquinolones were demonstrated in spiked meat at three levels from 10 to 50 ㎍/kg. The recoveries ranged between 75.8~99.2% in beef, 80.1~99.6% in pork and 72.2~99.8% in chicken, respectively. The limits of quantitation (LOQs) for fluoroquinolones ranged from 0.7 to 3.2 ㎍/kg. We also monitored fluoroquinolones residue in the sample (beef 107, pork 71, chicken 52) using LC-MS/MS. Residues of fluoroquinolones which exceeded maximum residue limits (MRL) were not exceed in any of the 230 samples.

• Korean Journal of Environmental Agriculture
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• v.22 no.3
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• pp.227-232
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• 2003

This study was conducted to evaluate the terminal residue of a new fungicide, KNF 1002, in cucumber and pepper under greenhouse and field conditions. When a microemulsion formulation (20%) of KNF 1002 was applied once or twice during $1{\sim}7$ days before harvest, its terminal residue in cucumber ranged <$0.02{\sim}0.20\;mg/kg$ under greenhouse condition. In pepper, its figure recorded $0.31{\sim}0.79\;mg/kg$ and $0.11{\sim}0.28\;mg/kg$ under greenhouse and field conditions, respectively. Much higher level of terminal residues was observed in leaves than those in fruits in pepper, showing $7.38{\sim}25.20\;mg/kg$ and $0.11{\sim}1.99\;mg/kg$ under greenhouse and field conditions, respectively. Cultivation condition affected evidently the residue level in pepper harvests. Residual pattern of KNF 1002 seemed to be comparable to strobilurin fungicides currently used.

• Korean Journal of Environmental Agriculture
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• v.34 no.2
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• pp.128-133
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• 2015

BACKGROUND: Plant extracts have been used as environment friendly agricultural materials for organic farming in South Korea. However safety evaluation on the plant extracts was not properly tested. The aim of this study was to evaluate safety of the extracts from Melia azedarach, Nerium indicum and Coptis chinensis on cultivating rice. METHODS AND RESULTS: Pant extarcts 300-fold diluted were treated on rice, and residues of M. azedarach, N. indicum and C. chinensis were determined. The analytes from the rice samples were detected by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). The method was validated, and good linearities ($r^2=0.995-0.998$), specificity, and recoveries were obtained. Limits of detection were 0.01 mg/kg for all of the target compounds. Recoveries were 79.3-118.3% at 0.1 mg/kg and 75.2-111.5% at 0.5 mg/kg. The residue levels were below 0.030 mg/kg for azadirachtin, 0.320 mg/kg for oleandrin and 1.460 mg/kg for berberine. CONCLUSION(S): The extracts of M. azedarach, N. indicum and C. chinensis contained azadirachtin, oleandrin and berberine as an active ingredient, respectively. The residue of three active ingredients dramatically decreased after treatment in all fruits, stems and roots of rice.

• Korean Journal of Environmental Agriculture
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• v.37 no.2
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• pp.97-103
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• 2018

BACKGROUND: Dissipation of acetamiprid and thiamethoxam in greenhouse grown chard samples was evaluated at 5 intervals including the pre-harvest interval after application. This study was conducted to determine the residue levels, the biological half-lives and dissipation rate of acetamiprid and thiamethoxam in chard under controlled conditions. METHODS AND RESULTS: Acetamiprid and thiamethoxam were applied in accordance with good agricultural practices for chard. Chard samples were collected at 0, 1, 2, 3, 5, 7, 10 and 14 days after application. Quantitaion was performed by HPLC-DAD system with C18 column. Limit of quantification (LOQ) of acetamiprid and thiamethoxam were both 0.02 mg/kg for chard. The recovery of acetamiprid and thiamethoxam were 77.8~107.5% and 94.3~108.6% at two concentration levels. The half-lives of pesticide dissipation in chard for two fields were 11.9 and 8.2 days for acetamiprid and 3.6 and 3.3 days for thiamethoxam respectively. The dissipation rate of acetamiprid and thiamethoxam were estimated according to the statistics method with a 95% confidence. CONCLUSION: Dissipation of acetamiprid and thiamethoxam in chard were determined under greenhouse. The concentration of acetamiprid and thiamethoxam in chards at 0 days after application were below specified by Korean MRL. Dissipation rate constant will be useful to set the pre-harvest residue limit for public health and consumer protection.

• Carbon letters
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• v.26
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• pp.66-73
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• 2018

We assessed the effects of combining bio-char with straw residue mulching on the loss of soil soluble nutrients and citrus yield in sloping land. The two-year study showed that straw residue mulching (ST) and bio-char application combined with straw residue (ST+BC) can significantly reduce soil soluble nutrient loss when compared with the control treatment (CK). The comparative volume of the soil surface runoff after each of the treatments was as follows: CK > ST > ST + BC. Compared with the CK, the runoff volume of the ST was reduced by 13.6 % and 8.5 % in 2014 and 2015, respectively. Compared with the CK, combining bio-char with the ST application reduced the loss of soluble nitrogen and improved the soil total nitrogen content reaching a significant level in 2015. It dramatically increased the soil organic matter content over the two year period (36.3% in 2014, 50.6% in 2015) as well as the carbon/nitrogen ratio (C/N) (16.6% in 2014 and 39.3% in 2015). Straw mulching combined with bio-char showed a trend for increasing the citrus yield.

• Resources Recycling
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• v.13 no.3
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• pp.50-57
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• 2004

Waste aluminum dross is a major waste in the aluminum scrap smelters and its components are mostly alumina and remained metallic aluminum. In the process to extract the remained aluminum from the waste dross by leaching with sodium hydroxide solution, residue is generated and its main component is alumina. This residue could be recycled into ceramic materials such as alumina castable refractories by going through a series of treatments such as washing, drying and roasting. In this study, a pilot plant was constructed and tested to demonstrate the developed technology. One thousand tons of waste aluminum dross could be processed, and about seven hundred tons of ceramic materials produced in the demonstration line. From the test run of the pilot plant, although it was confirmed that the developed technology could be applied to commercialization, several technical improvements were found to be necessary for reducing impurities such as Na, Fe and for reforming drying equipment.

• Journal of Mushroom
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• v.12 no.4
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• pp.367-370
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• 2014

In this study, we attempted to find substitute materials, distillers residue of cassava, alfalfa pellet, and distillers residue of corn, for cotton seed meal in bottle cultivation of Pleurotus ostreatus. In all treatments, the total carbon content was comparable with the exception of T4, and the total nitrogen content of T3 was similar to the control group, and C/N ratio of T4 was higher than other treatments. The diameter of plieus was the largest in T2, and the diameter of stipe was the largest in T2 and T4. And the length of stipe was largest in T1 and T2, and the most number of available stipes was in T1 and T3. The yield and bio-efficiency of fruit-body by residue of corn with soluble treatment(T3), were similar to the control of P. ostreatus. Therefore, it was suggested that residue of corn was substituted for cotton seed meal for cultivation of P. ostreatus.

• Economic and Environmental Geology
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• v.53 no.2
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• pp.183-196
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• 2020

This study aimed to recover native gold from the concentrate using microwave-nitric acid leaching and magnetic/hydro separation experiments. The insoluble-residue was filtered from leaching solution through microwave-nitric acid leaching experiment. As a result of the atomic absorption spectrometer(AAS) analysis of the filtered leaching solution, it was discovered that Au content was not eluted at all and it was observed from the back scattered electron(BSE) image that native gold was liberated in the insoluble-residue. When magnetic/hydro separation experiments were applied for the insoluble-residue, magnetic and non magnetic minerals were separtated from insoluble-residue. Magnetite was recovered from the magnetic minerals and as a result of applying the hydro separation experiment again for the non-magnetic mineral, native gold was recovered. The native gold was identified through the X-ray diffraction(XRD) analysis and BSE image.