• Journal of the Korean Chemical Society
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• v.34 no.4
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• pp.345-351
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• 1990

Optical isomers of DABS-amino acids have been separated in a reversed phae high performance liquid chromatography by adding Cu (Ⅱ)-L-Proline chelate to the mobile phase. The retention behaviors for the DABS-amino acids are discussed in terms of pH of the mobile phase and the concentrations of acetonitrile, Cu (Ⅱ) complex, and buffer. The selectivity of the optical isomers of DABS-amino acids increases with the pH of the mobile, and the concentration of the chelate, but decreases with concentration of the oganic modifier. The concentration of buffer does not affect the optical separation selectivity. A separation mechanism is illustrated by cis and trans formation based on the steric effect of the ligand exchange reaction between DABS-amino acids and the copper chelate.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.3
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• pp.173-179
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• 2010

In a HLW repository, the buffer is exposed to an elevated temperature due to a radioactive decay and geochemical conditions for a long time and such a hydrothermal condition may cause a significant loss of its barrier function. This study carried out hydrothermal tests with a domestic smectite clay to investigate the changes in the expandibility, layer charge, and cation exchange capacity of the smectite. When the temperature and potassium concentration in solution was increased for the hydrothermal treatments, the expandibility decreased, the layer charge negatively increased, and the CEC also decreased.

• Restorative Dentistry and Endodontics
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• v.33 no.6
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• pp.507-517
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• 2008

There are considerable in vitro and in vivo evidences for remineralization and demineralization occurring simultaneously in incipient enamel caries. In order to "heal" the incipient dental caries, many experiments have been carried out to determine the optimal conditions for remineralization. It was shown that remineralization is affected by different pH, lactic acid concentrations, chemical composition of the enamel, fluoride concentrations, etc. Eighty specimens from sound permanent teeth without demineralization or cracks, 0.15 mm in thickness, were immersed in lactic acid buffered demineralization solutions for 3 days. Dental caries with a surface zone and subsurface lesion were artificially produced. Groups of 10 specimens were immersed for 10 or 12 days in lactic acid buffered remineralization solutions consisting of pH 4.3 or pH 6.0, and 100, 50, 25, or 10 mM lactic acid. After demineralization and remineralization, images were taken by polarizing microscopy (${\times}100$) and micro-computed tomography. The results were obtained by observing images of the specimens and the density of the caries lesions was determined. 1.As the lactic acid concentration of the remineralization solutions with pH 4.3 was higher, the surface zone of the carious enamel increased and an isotropic zone of the subsurface lesion was found. However, the total decalcification depth increased at the same time. 2.In the remineralization solutions with pH 6.0, only the surface zone increased slightly but there was no significant change in the total decalcification depth and subsurface zone. In the lactic acid buffer solutions with the lower pH and higher lactic acid concentration, there were dynamic changes at the deep area of the dental carious lesion.

• Journal of Plant Biology
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• v.36 no.4
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• pp.407-413
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• 1993

해녀콩(Canavalia lineata L. DC) 잎에서 유도한 캘러스를 pH 8인 완충용액에 한 시간 동안 처리하면 pH 6에서 보다 arginase의 활성이 약 두 배로 증가했다. 캘러스에서 얻은 arginase의 조효소액을 Sephacryl S-200 컬럼에서 분획하면 분자량이 각각 380 kD과 179 kD으로 나타났는데 분자량이 큰 arginase의 분획은 pH 8 처리구에서 각각 상대적으로 많이 나타났다. 그리고 pH 6에 0.5 mM Mn2+를 첨가하였을 때도 380 kD arginase의 분획이 크게 나타났으며, pH 6 처리에서 얻은 179 kD arginase 분획에 pH 8 처리를 하면 380 kD 분획으로 쉽게 전이될 수 있었다. pH 6 처리 후 추출한 arginase는 Mn2+의 첨가로 활성이 크게 증가하여 pH 8 처리 후 추출한 arginase와 비슷한 활성을 보이나, pH 8 처리 후 추출한 arginase는 Mn2+의 첨가로 더 이상의 활성증가를 보이지 않았다. Mn2+이 없는 조건에서 두 arginase의 Km값과 Vmax를 조사한 결과, 380 kD arginase는 22 mM과 1.61 $\mu$mole urea.min-1.mg-1 protein, 그리고 179 kD arginase는 30 mM과 0.79 $\mu$mole urea.min-1.mg-1 protein으로 측정되었다.

• Analytical Science and Technology
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• v.18 no.1
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• pp.35-42
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• 2005

This study reports the effect of $Mg^{2+}$ ions on the behavior of the anionic surfactant in electrophoresis. Intractions of $Mg^{2+}$ ions with carboxylates and sulfonates resulted large changes in their apparent mobilities. A comprehensive analysis of the electroosmotic and electrophoretic mobilities reveals that major cause for the variation of the apparent mobilities of anions arises from the electroosmotic mobilities.

• Korean Journal of Food Science and Technology
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• v.23 no.6
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• pp.695-701
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• 1991

Spent layer breast meat and leg meat samples washed with 0.05 M sodium bicarbonate solution and 0.04 M phosphate buffer(pH 8.3) showed decreases in heat denaturation temperature indicating the destabilization of myofibrillar proteins. The destabilization was attributed to the solubilization of 95 Kdalton and 55 kdalton proteins from the myofibrils observed in gel-electrophoretograms. Transmission electron microscopy further indicated the breakage of Z-lines.

• Applied Chemistry for Engineering
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• v.5 no.1
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• pp.114-120
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• 1994

Esterolysis reactions of PNPDPP (p-nitrophenyldiphenylphosphate) by DCI ( dichloroisocyanuric acid sodium salt) in borate buffer pH8.0 micellar phase were studied. The rate of hydrolysis reaction was rapidly increased by adding cationic surfactants, CTAC (cetyltrimethylammonium chloride) or CTAB (cetyltrimethylammonium bromide), to the DCI solution. Especially in CTAB micellar system, the N-Cl bond of DCI was transformed to the N-Br bond during the reaction.

• The Korean Journal of Zoology
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• v.37 no.2
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• pp.144-155
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• 1994

마이크로파 에너지로서 현미경 관찰을 위한 생체물질을 고정할 때, 고정효과는 화학 고정액을 사용할 때와 비교하여 보다 우수한 또는 적어도 동일한 고정효과를 볼 수 있다는 것은 알려진 사실이다. 그러나 기존의 마이크로파 오븐을 사용하여 생체물질을 고정하면 고정 정도에 일정성이 없는데, 이는 마이크로파가 균일하게 조사되지 않고 고정에 적절하도록 마이크로팍의 강도를 조절하기 어려우며, 이로 인하여 정확한 고정온도의 측정이 불가능하기 때문으로 생각된다. 이 연구에서는 마이크로파가 조사되는 동안 시료의 온도를 측정할 수 없는 기존의 마이크연.파 오븐의 단점을 보완하기 위하여 비접촉식 적외선 온도 감응기를 장착한 마이크로파 오븐을 개발하였으며 고정효과를 관찰하기 위하여는 포유류의 기준 조직으로 알려진 생쥐의 신장을 고정하였다 고정효과는 전체적인 구조와 세부 구조의 보존이 모두 우수하였고 최적의 고정온도는 28$\pm$1$^{\circ}C$(완충용액 20 ml, 10초) 이었다. 이와같이 고정된 재료는 고정효과 뿐만 아니라 염색성이 좋아서 조직화학 반응이 우수하고, 냉동절편법과 연계했을 때 전체 절편제작 과정이 2~4시간 내에 완료될 수 있었다 이때 절편의 질(질)은 화학 고정액이나 냉동절편 법에 의하여 제작된 것 보다 우수하였다.

• Journal of the Korean Chemical Society
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• v.35 no.3
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• pp.219-225
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• 1991

Capillary zone electrophoresis (CZE) which is highly efficient separation technique has been domestically established having optimum detection sensitivity. By applying 20∼35 kV of electric potential to the narrow (50 ${\mu}m$ i.d.) capillary tubing filled with running buffer, this technique can quickly (< 20 min) separate the small quantities of sample with high separation efficiency (number of theoretical plates : 200,000∼500,000). Factors affecting the separation efficiency and resolution in CZE were examined by analyzing adenine and catecholamine derivatives.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.889-893
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• 1992

A very sensitive adsorptive stripping voltammetric method is studied on the gallium-morin complex at a hanging mercury drop electrode (HMDE) in 0.1 M acetate buffer solution. The effects of various analytical conditions are discussed on the reduction peak current of the adsorbed complex on the suface of HMDE. Interferences by other trace metals and surfactant are also discussed. Detection limit is 1.7 nM of gallium with 60 seconds deposition time, and the relative standard deviation (n = 7) at 4 ${\mu}$g/l gallium is 2.8%.