• 한국광물학회지
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• 제14권2호
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• pp.119-127
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• 2001

주구성 양이온이 Si와 Al인 딕카이트와 엽납석에 대하여 적외선분광분석(FTIR)을 실시하였다. 원적외선(Far-IR)영역과 중간적외선(Mid-IR)영역을 이용하였으며, 특히 $200 cm^{-1}$ / 이하의 Far-IR영역에서 처음으로 딕카이트의 흡수선들을 제시하였다. 딕카이트의 경우 일부 시료에서 소량의 카올리나이트나 나크라이트 층이 소량으로 협재되어 있다. 카올리나이트의 결정도를 나타내는 Hinckley지수는 딕카이트의 결정도와는 관련성이 적게 나타났다. 엽납석의 경우, 수산기와 관련된 신축진동흡수띠($3673~3676 cm^{-1}$ )는 약간 이상적인 구조에서 벗어나 있는데, 아마도 미량의 철에 의한 영향이나, 삼사형과 단사형이 섞여 있기 때문인 것으로 보인다.

• 한국재료학회지
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• 제8권3호
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• pp.219-223
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• 1998

실리카 유리에 3가 이온 희토류 원소인 $Eu^{3+}$, $Sm^{3+}$, $Tb^{3+}$를 첨가한 경우의 분광특성 변화를 연구하였다. 유리시료의 분광특성은 회토류를 첨가한 경우의 파장영역에 따른 흡수 및 발광파장의 변화를 관찰하였으며, 희토류 함량을 1-10wt%까지 첨가하여 함량변화에 따른 형광세기 변화를 조사하였다. 형광특성 측정 결과 희토류 원소의 함량이 10wt%까지 형광세기는 함량에 비례하여 계속 증가하였으며, 시료의 형광특성을 상온에서 관측한 결과 400-500nm사이에서 가장 많은 빛을 흡수하여 가시광선 영역인 600nm부근에서 방출되는 형광세기가 가장 크게 나타났다. 이때 방출되는 희토류 원소들은 $Eu^{3+}$의 경우 $^{5}D_{o}$ -> ^{7}F$. $Sm^{3+}$ 은 $4F_{5/2}$ -> $^{6}H$, $Tb^{3+}$은 $^{5}D_{4}$ -> ^{7}F$의 전이임일 알 수 있었다.

• Advances in nano research
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• 제3권2호
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• pp.97-109
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• 2015

Citrate ion is a commonly used reductant in metal colloid synthesis, undergoes strong surface interaction with silver nanocrystallites. The slow crystal growth observed as a result of the interaction between the silver surface and the citrate ion makes this reduction process unique compared to other chemical and radiolytic synthetic methods. The antimicrobial effects of silver (Ag) ion or salts are well known, but the effects of citrate coated Ag nanoparticles (CAgNPs) are scant. Herein, we have isolated biofilm causative bacteria and fungi from drinking water PVC pipe lines. Stable CAgNPs were prepared and the formation of CAgNPs was confirmed by UV-visible spectroscopic analysis and recorded the localized surface plasmon resonance of CAgNPs at 430 nm. Fourier transform infrared spectroscopic analysis revealed C=O and O-H bending vibrations due to organic capping of silver responsible for the reduction and stabilization of the CAgNPs. X-ray diffraction micrograph indicated the face centered cubic structure of the formed CAgNPs, and morphological studies including size (average size 50 nm) were carried out using transmission electron microscopy. The hydrodynamic diameter (60.7 nm) and zeta potential (-27.6 mV) were measured using the dynamic light scattering technique. The antimicrobial activity of CAgNPs was evaluated (in vitro) against the isolated fungi, Gram-negative and Gram-positive bacteria using disc diffusion method and results revealed that CAgNPs with 170ppm concentration are having significant antimicrobial effects against an array of microbes tested.

• 방사성폐기물학회지
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• 제16권4호
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• pp.397-410
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• 2018

아메리슘(Am)은 사용후핵연료의 장기 방사성 독성에 크게 영향을 주기 때문에 고준위 방사성 폐기물 처분의 장기 안전성 평가에 필수적으로 고려되어야 할 원소이다. 분광학적 방법을 이용한 일부 악티나이드 원소의 화학반응 연구가 활발히 진행되고 있는 반면, 아메리슘에 대한 연구는 아직까지 미비한 상황이다. 이 연구에서는 고순도의 시료를 필요로 하는 화학반응 연구를 위하여 $^{241}Am$ 시료를 정제한 후, 액체섬광계수기와 감마선 및 알파선 스펙트럼을 이용하여 정량과 정성분석을 하였다. 액체 광도파 모세관 셀을 이용한 고감도의 UV-Vis 흡수 분광학과 시간분해 레이저 형광 분광학을 이용하여 Am(III) 가수분해물과 옥살레이트(oxalate, Ox) 착물반응을 조사하였다. 산성조건에서 $Am^{3+}$은 503 nm에서 최대 흡수봉우리를 보이며, 몰흡광계수는 $424{\pm}8cm^{-1}{\cdot}M^{-1}$임을 확인하였다. 중성 이상의 pH 조건에서 형성되는 $Am(OH)_3(s)$ 콜로이드 입자에서는 506-507 nm 파장에서 최대 흡수봉우리가 관측되었다. ${Am(Ox)_3}^{3-}$ 착물은 $Am^{3+}$에 비교하여 흡수 및 발광스펙트럼이 각각 4와 5 nm정도 장파장으로 이동하였고 몰흡광계수와 발광세기도 크게 증가하였다. ${Am(Ox)_3}^{3-}$의 발광수명은 23에서 56ns으로 증가하였고 이는 Am(III)의 내부권에 결합하고 있던 약 여섯 개의 물분자가 옥살레이트의 카르복실기로 치환되었음을 의미한다. 이 결과로부터 ${Am(Ox)_3}^{3-}$은 각 옥살레이트 리간드가 두 자리 결합(bidentate)을 하고 있다는 것을 제안하였다.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.275-280
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• 2010

Actinobacillus actinomycetemcomitans is a gram-negative, nonmotile coccobacillus bacterium that is associated with several human diseases, including endocarditis, meningitis, osteomyelitis, subcutaneous abscesses and periodontal diseases. A full-length Omp1-like protein gene from A. actinomycetemcomitans was cloned into a pQE30 vector and overexpressed in Escherichia coli BL21(DE3) cells. The protein revealed sequence homologies to Seventeen kilodalton proteins (Skp) from Pasteurella multocida and E. coli that have been characterized as periplasmic chaperones. This soluble Omp1-like protein was successfully purified to homogeneity for further folding and functional studies. The purity, identity, and conformation of the protein were determined using sodium dodecyl sulfate polyacrylamide gel electrophoresis, matrix-assisted laser desorption ionization mass spectrometry, circular dichroism, fluorescence spectroscopic, and differential scanning calorimetric studies. We showed that the protein formed an oligomer larger than a tetramer. We found, further, that it is comprised of mostly $\alpha$-helices and boasts high thermal stability.

• BMB Reports
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• 제30권2호
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• pp.125-131
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• 1997

This work reports studies of the catalytic and structural properties of pyridoxal kinase (ATP: pyridoxal 5' -phosphotransferase, EC. 2.7.1.35), Pyridoxal kinase catalyzes the phosphorylation of vitamin $B_6$ (pyridoxal, pyridoxamine, pyridoxine) using ATP-Zn as a phosphoryl donor. The enzyme purified from brain tissues is made up of two identical subunits of 40 kDa each. Native enzyme was inhibited by a substrate analogue, pyridoxal-oxime. Limited chymotrypsin digestion of pyridoxal kinase yields two fragments of 24 and 16 kDa with concomitant loss of catalytic activity. These fragments were isolated by DEAE ion exchange chromatography and used for binding studies with fluorescent ATP and pyridoxal analogues. The spectroscopic properties of both fluorescent pyridoxal analogue and Anthraniloyl ATP (Ant-ATP) bound to the 24 kDa fragment are indistinguishable from those of both pyridoxal analogue and Ant-ATP bound to the native pyridoxal kinase, respectively. The small 16 kDa fragment, generated by proteolytic cleavage of the kinase, does not bind any of the substrate analogues. Binding characteristics of Ant-ATP were extensively studied by measuring the changes in fluorescence spectra at various conditions. From the results presented herein, it is postulated that the structural domain associated with catalytic activity comprises approximately one-half of the molecular mass of pyridoxal kinase (24 kDa). whereas the remaining portion (16 kDa) of the enzyme contains a regulatory binding domain.

• Journal of Pharmaceutical Investigation
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• 제22권2호
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• pp.139-148
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• 1992

A prodrug of cefazolin pivaloyloxymethyl ester (CFZ-PV) was synthesized to improve oral absorption and bioavailability of parent drug by esterification of sodium cefazolin (CFZ) with chloromethyl pivalate. The successful synthesis of CFZ-PV was confirmed by spectroscopic analysis. Partition coefficient studies showed that CFZ-PV is more lipophilic than CFZ. The pharmacokinetic characteristics of CFZ-PV and CFZ preparations were compared following oral administrations of these compounds to rabbits. The analysis of CFZ in plasma was conducted by HPLC method. The ester compound (prod rug) was not detected in plasma following oral administration of CFZ-PV, and although CFZ-PV had not microbiological activity in vitro, the plasma taken after CFZ-PV administration had microbiological activity. From above observations, it was noted that CFZ-PV is rapidly hydrolyzed to CFZ in the body. And it was found that the oral absorption of CFZ-PV was increased, yielding 2-fold higher bioavailability than CFZ. From the results of this experiment, it was concluded that CFZ-PV could be a novel prodrug of CFZ which can improve the oral bioavailability of CFZ.

• Journal of Pharmaceutical Investigation
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• 제23권2호
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• pp.61-69
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• 1993

Prodrug of cefazolin (CFZ) was prepared with the objective of improving its oral bioavailability. Cefazolin phthalidyl ester (CFZ-PT) was synthesized and evaluated as potential prodrug form. The successful synthesis of CFZ-PT was identified by spectroscopic analysis. Partition coefficient studies showed that CFZ-PT is more lipophilic than CFZ and the ester was hydrolyzed enzymatically into the parent drug in blood, liver and intestinal homogenates. The pharmacokinetic characteristics of CFZ-PT and CFZ were compared following oral administrations to rabbits. Serum CFZ concentration was determined by HPLC method and the ester compound (prodrug) was not detected in serum following oral administration of CFZ-PT. CFZ-PT did not have antimicrobial activity in vitro against Bacillus subtilis ATCC 6633, whereas CFZ-PT in serum after oral administration to rabbits had antimicrobial activity. From above observations, it was noted that CFZ-PT is rapidly hydrolyzed to CFZ in the body and the bioavailability of CFZ-PT was increased by 3.5-fold than that of CFZ. From these results of this study, it was concluded that CFZ-PT may be a novel prodrug of CFZ which can improve the oral absorption of CFZ.

• BMB Reports
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• 제35권4호
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• pp.364-370
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• 2002

The effect of sodium n-dodecyl sulphate (SDS) on hemoglobin autoxidation was studied in the presence of a 100mM phosphate buffer (pH 7.0) by different methods. These included spectorphotometry, fluorescence technique, cyclic voltametry, differential scanning calorimetry, and densitometry. Spectroscopic studies showed that SDS concentrations up to 1 mM increased deoxy-, decreases oxy-, and had no significant effect on the met- conformation of hemoglobin. Therefore, a SDS concentration up to 1 mM increased the deoxy form of hemoglobin as the folded, compact state and decreases the oxy conformation. The turbidity measurements and differential scanning calorimetry techniques indicated a more stable conformation for hemoglobin in the presence of SDS up to 1mM. Electrochemical studies also confirmed a more difficult oxidation under these conditions. The induction of the deoxy form in the presence of SDS was confirmed by densitometry techniques. The compact structure of deoxyhemoglobin blocks the formation of met-conformation in low SDS concentrations.

• 한국세라믹학회지
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• 제26권6호
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• pp.811-819
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• 1989

There have been many studies on the biological phenomena of Bioglasses, which nay be used as implant materials in human body. However, not many works on the Bioglass compositions have been reported. In the present study, the effect of Al2O3 substitution for SiO2 in Bioglass of Na2O-CaO-P2O5-SiO2 system on its structure and properties was examined. Infrared and Raman spectroscopic studies for the glass structural analysis, differential thermal analysis and X-ray diffraction analysis for crystallization of the glass were perfomed. Several physical properties, such as thermal expansion coefficient, softening point, microhardness and reaction phenomena, were also measured. The major crystalline phase, after heat treatment of the glasses, was Na2Ca2(SiO2)3 and the crystal was transformed into other phase with increased substitution of Al2O3. The added Al2O3 reduced non-bridging oxygen in glass structure and thermal expansion coefficient, but increased glass density, sofening point and microhardness. When the glasses are reacted in Tris-buffer solution, the substituted Al2O3 inhibited the formation of hydroxyapatite on the Bioglas surface, and no hydroxyapatite was formed for the sample which contained more than 6wt.% of Al2O3 even if they were reacted for 600 hours.