• BMB Reports
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• v.33 no.1
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• pp.43-48
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• 2000

4-Aminobutyrate aminotransferase is a key enzyme of the 4-aminobutyric acid shunt. It converts the neurotransmitter 4-aminobutyric acid to succinic semialdehyde. In order to study the structural and functional aspects of catalytically active Cys residues of pig brain 4-aminobutyrate aminotransferase, we purified the active form in E. coli by coproduction of thioredoxin. The structural arrangement for functional requirements of a dimeric protein using a bifunctional sultbydryl reagent was then characterized, and the spatial proximity between the essential SH groups and a cofactor (pyridoxal-5'-phosphate) binding site was determined. The bifunctional sultbydryl reagent DMDS reacted with the enzyme at the ratio of one molecule per enzyme dimer. This resulted in an approximately 50% loss of enzymatic activity. The spatial proximity of the distance between the essential SH groups and the cofactor-binding site was determined by the energy transfer measurement technique. The result (approximate 20 ${\AA}$) suggested that cross-linking of two sulfhydryl groups with DMDS is not near a PLP binding site.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.11a
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• pp.292-293
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• 2002

대기 중에서 HOx(OH, H $O_2$) 라디칼은 가장 중요한 산화제로서 광화학 반응의 핵심적 역할을 한다. 이러한 OH 라디칼의 정확한 농도를 측정하기 위한 여러 가지 시도가 있었으나, 그 존재량이 적고 수명이 짧기 때문에 측정에 많은 어려움이 있다. 간접적인 측정에 근거한 모델링과 계산적인 이론 값에 의하면 대류권에서의 전 지구적 평균 OH 라디칼의 농도는 대략 $10^{6}$molecules $cm^{-3}$이고, H $O_2$ 라디칼의 농도는 $10^{8}$molecules $cm^{-3}$정도로 추정된다. (중략)

• Journal of Biosystems Engineering
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• v.24 no.6
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• pp.539-546
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• 1999

Some stress for a plant could be detected to a certain degree by plant physiological measuring technique of the state of the art. The capability of early detection of my measuring system depends on kind of plant and kind and level of stress. The objectives of this study were to evaluate the capability of several fast and intact type plant stress detection systems to detect nitrogen deficiency of cucumber in the field. A series of experiment was carried out with four kinds of intact type measuring devices - a chlorophyll content meter, a chlorophyll fluorescence measurement system, an infrared thermometer and an optical spectrometer. The experiments resulted that the chlorophyll content meter could detect the stress of N deficiency at a confidence level higher than 95% on 3rd day for the earliest case and the detection of high precision was possible from 7th day after the stress was applied. The chlorophyll fluorescence measurement system detected the stress at a confidence level higher than 95% on 3rd day for the earliest case but the detection was not as much precise as the chlorophyll content meter. Leaf temperature measurement noted very poor results to detect the stress. Using the spectrometer, sensitive wavelength regions to detect the stress were searched and found out as 562∼564 nm, 700∼724 nm and 1,886∼1,894 nm. With the spectrometer using any of wavelength within the sensitive wavelength region, detection of the stress at a confidence level higher than 95% was possible from 3rd or 4th day after the stress was applied.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.153-160
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• 2003

The purpose of study was to evaluate the effects of the $CO_2$ laser irradiation on demineralization inhibition and rehardening of human primary tooth enamel by laser fluoresecence measurement. Enamel specimens were made from the human primary teeth. The center spots of the specimens about 2 mm diameter were irradiated by $CO_2$ laser at the conditions of focused continuous or defocused pulsed, 3 or 6 W, for 4 seconds, before or after the demineralization by Coca-Cola for 24 hours at $37^{\circ}C$. The Diagnodent was used to measure the degree of demineralization and rehardening. There was no significant difference between focused continuous and defocused pulsed irradiation. 6W irradiation inhibited the demineralization but 3W did not. 6W irradiation rehardened the demineralized enamel but 3W did partially. The color of enamel was changed to brown to black after 6W irradiation but 3W caused no color change. $CO_2$ laser irradiation showed the effects on demineralization inhibition and rehardening of human priamary tooth enamel, and the laser fluoresecence measurement technique seemed to be a valid evaluation method.

• The Korean Journal of Physiology
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• v.28 no.2
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• pp.203-214
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• 1994

Using the methods of stopped-flow and epifluorescence microscopy with entrapped fluorophore, membrane permeability of $NH_3$ and weak acids in liposomes, renal brush border (BBMV) and basolateral membrane vesicles (BLMV), and primary culture cells from renal proximal tubule was measured. Permeability coefficient (cm/sec) of $NH_3$ was $(2.9{\times}10^{-2}$ in phosphatidylcholine liposome $25^{\circ}C)$, $5.9{\times}10^{-2}$ in renal proximal tubule cell $(37^{\circ}C)$, $4.0{\times}10^{-2}\;and\;2.4{\times}10^{-2}$ in BBMV and BLMV $(25^{\circ}C)$, respectively. Formic acid has the highest permeability coefficient among the weak acids tested, which was $4.9{\times}10^{-3}$ in liposome, $5.0{\times}10^{-3}$ in renal proximal tubule cell, $9.1{\times}10^{-3}$ in BBMV and $3.8{\times}10^{-3}$ in BLMV. There was a linear relationship between external concentration of nonionized formic acid and initial rate of flux of formic acid in liposome, and the slope coincided with the value of permeability coefficient of formic acid measured in pH 7.0. These results show that techniques of stopped-flow and epifluorescence microscopy with entrapped fluorophore provide the precise method of measurement of very rapid transport of nonelectrolytes through membranes with the advantages of instantaneous mixing effect, good resolution time and easy manipulation.

• Journal of Radiation Protection and Research
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• v.41 no.4
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• pp.359-367
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• 2016

Background: As new legislation has come into force implementing radiation safety management for the use of naturally occurring radioactive materials (NORM), it is necessary to establish a rapid and accurate measurement technique. Measurement of $^{238}U$ and $^{232}Th$ using conventional methods encounter the most significant difficulties for pretreatment (e.g., purification, speciation, and dilution/enrichment) or require time-consuming processes. Therefore, in this study, the applicability of ED-XRF as a non-destructive and rapid screening method was validated for raw materials and by-product samples. Materials and Methods: A series of experiments was conducted to test the applicability for rapid screening of XRF measurement to determine activity of $^{238}U$ and $^{232}Th$ based on certified reference materials (e.g., soil, rock, phosphorus rock, bauxite, zircon, and coal ash) and NORM samples commercially used in Korea. Statistical methods were used to compare the analytical results of ED-XRF to those of certified values of certified reference materials (CRM) and inductively coupled plasma mass spectrometry (ICP-MS). Results and Discussion: Results of the XRF measurement for $^{238}U$ and $^{232}Th$ showed under 20% relative error and standard deviation. The results of the U-test were statistically significant except for the case of U in coal fly ash samples. In addition, analytical results of $^{238}U$ and $^{232}Th$ in the raw material and by-product samples using XRF and the analytical results of those using ICP-MS ($R^2{\geq}0.95$) were consistent with each other. Thus, the analytical results rapidly derived using ED-XRF were fairly reliable. Conclusion: Based on the validation results, it can be concluded that the ED-XRF analysis may be applied to rapid screening of radioactivities ($^{238}U$ and $^{232}Th$) in NORM samples.

• Biomedical Science Letters
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• v.3 no.1
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• pp.29-35
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• 1997

Cardiovascular disease has been the leading cause of death among patients with chronic renal failure. Many reports have been described that homocysteine is one of the independent risk factor to the occulsive vascular disease. In this study, HPLC/FLD (high performance liquid chromatography-fluorescence detector) technique was used to measure homocysteine level in patients with chronic renal failure and normal control group. The detection limit and recovery of total plasma homocysteine using HPLC/FLD were 98.6$\pm$5.8% and 0.2 nmol/ml, respectively. The linearity of this method was established in concentration range of 2~50 nmol/ml (correlation coefficient=0.9997). The concentrations of total plasma homocysteine were 6.81$\pm$1.54 nmol/ml and 27.28$\pm$14.94 nmol/ml in normal control (n=20) and patient group (n=90), respectively (p<0.05). In this study, the HPLC/FLD method showed high sensitivity and reproducibility for a routine clinical laboratory testing. Moreover determination of homocysteine level in plasma might be useful for a biochemical marker for predicting the cardiovascular diseases and for monitoring of therapeutic effect of lowering homocysteine in patients with chronic renal failure.

• Applied Biological Chemistry
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• v.37 no.5
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• pp.343-348
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• 1994

Ti plasmid of A. tumefaciens was labeled with $^3H-thymidine$, purified and encapsulated into phosphatidylserine (PS) and PS-cholesterol (Chol; 1 : 1 molar ratio) liposomes by lyophilization-rehydration method. PS was supplemented with 1 mole percent octadecyl rhodamine B for fluorometric measurement of PS. Liposomes entrapping $^3H-Ti plasmid$ were fused with Nicotiana sanderae protoplasts by treating with 5 mM $CaCl_2$ and 10% PEG. The fusion was evidenced by fluorescence microscopic technique. The amounts of Ti plasmid and PS associated with protoplasts were assayed by the radioactivity of $^3H-Ti plasmid$ and by the fluorescence of rhodamine B. About 7.9% of the PS liposome and 7.2% of PS-Chol liposome were fused with protoplasts. During the fusion process, about 30% of the liposomal contents of PS-Chol liposome was leaked, in contrast to about 60% leakage of its contents in PS liposome. Accounting the number of liposomes fused with protoplasts together with the encapsulation efficiency and the leakage of liposomal contents, it was calculated that ca. 1,700 Ti plasmid was transfered into one protoplast by the present method. This result may indicates that the present method transfers enough Ti plasmid into plant protoplast to elicit genetic transformation of plants.

• Environmental Engineering Research
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• v.17 no.4
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• pp.205-210
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• 2012

Hydroperoxyl radical/superoxide anion radical ($HO_2{\cdot}/O_2^-{\cdot}$, $pK_a$=4.8) as an intermediate is of considerable importance in oxidation processes. Hence, the method of detecting $HO_2{\cdot}/O_2^-{\cdot}$ with high sensitivity is necessary to be developed. To achieve this objective, this study newly employed terephthalate (TA) as a probe for the measurement of $HO_2{\cdot}/O_2^-{\cdot}$ in the kinetic method presented in our previous study. This method was based on the hydroxylation of TA to produce mainly hydroxyterephthalic acid or hydroxyterephthalate (OHTA), which was analyzed by fluorescence detection (${\lambda}_{ex}$=315nm, ${\lambda}_{ex}$=425nm). The life-time of $HO_2{\cdot}/O_2^-{\cdot}$ and its concentration formed from the photolysis technique of $H_2O_2$ were reported in this study. At range of pH 2-10, the life-time of $HO_2{\cdot}/O_2^-{\cdot}$ was 51-422 sec. In particular, an increase in the life-time with pH was observed. The sensitivities of the kinetic method by using TA were always higher with 1.7-2.5 times at pH 8.0 than those by using benzoic acid. From these results, this study can contribute to understanding the basic functions of $HO_2{\cdot}/O_2^-{\cdot}$ in oxidation processes.

• Journal of Bio-Environment Control
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• v.28 no.4
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• pp.461-470
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• 2019

This study was carried out to quantify the drought stress in grafted watermelon seedlings non-destructively by using chlorophyll fluorescence (CF) imaging technique rather than the visual judgment. Six-day old watermelon seedlings were grown under uniform irrigation for 3 days, and then given drought stress. Afterward, the sensor for the measurement of water content in plug tray cell unit was used to classify the drought-stress level into nine groups from D1 (53.0%, sufficient moisture state) to D9 (15.7%, extremely dry stress), and the 16 CF parameters were measured. In addition, re-irrigation was performed on the drought stressed seedlings(D5 - D9) to determine the growth and photosynthesis recovery level, which was not confirmed by visual judgment. The kinetic curve patterns of CF in three different drought stressed seedling groups were found to be different for the early detection of drought stress. All the 16 CF parameters decreased continuously with exposure to drought stress and drastically decreased from D5 (32.1%) where the visual judgment was possible. The fluorescence decline ratio (Rfd_Lss) started to decrease from the initial drought stress level (D5 - D6), and the Maximum PSII quantum yield (Fv/Fm) was significantly decreased in the later extreme drought stress range (D7 - D9) by re-irrigation recovery test. Thus, Rfd_Lss and Fv/Fm parameters were finally selected as potent indicators of growth and photosynthesis recovery in the initial and later stages of drought stress. Also, to the differences in the numerical values of the individual chlorophyll fluorescence parameters, the drought stress level was intuitively confirmed through the image. These results indicate that Rfd and Fv/Fm can be considered as potential CF parameters for the detection of low and extremely high drought stress, respectively. Furthermore, Fv/Fm can be considered as the best CF parameters for recovery at re-irrigation.