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Bacillus amyloliquefaciens α - amylase 의 구조적 안정성에 대한 분광학적 및 전기영동 연구
오화섭,김광희,서세원,최명언 ( Hwa Seop Oh,Kwang Hee Kim,Se Won Suh,Myung Un Choi ) 생화학분자생물학회 1991 BMB Reports Vol.24 No.2
The nature of calcium ion binding to α-amylase from Bacillus amyloliquefaciens was examined to investigate its effect on the structural stability of the enzyme. Calcium ion provided an excellent protection against the destruction of the enzyme activity by heat, protease, and denaturing agents. The structural change of α-amylase upon binding of Ca^(2+) has been studied by circular dichroism, fluorescence, and UV difference absorption spectroscopy. Upon binding calcium ions, the content of α-helical structure of α-amylase increased significantly and the binding constant of calcium to α-amylase was found to be about 4.8 mM at pH 7.5. The fluorescence emission spectrum showed that the calcium-free enzyme had different λ_(max) from the native enzyme. The λ_(max) of the Ca^(2+)-free enzyme shifted to longer wavelength by 15 nm and the intensity at λ_(max) decreased compared to the native enzyme. Furthermore, the protective nature of calcium ion binding was examined by electrophoretic techniques. The fragmentation pattern of α-amylase following an irreversible thermoinactivation at 90℃ was analyzed by SDS-PAGE. The native and calcium-free enzymes showed a marked difference in the electrophoretic patterns. In the case of native enzyme, the aggregate of the main band (54.7 kD) appeared gradually as high-molecular mass traces on the top region of the gel. However, in the case of Ca^(2+)-free enzyme, the main band disappeared rapidly and new distinct bands of smaller molecular masses (40.2 kD, 22.0 kD, 13.1 kD) appeared. The digestion patterns of α-amylase by trypsin were also different between the native and Ca^(2+)-free enzyme. From these results it can be concluded that the binding of Cat` ion contributes markedly to the structural stability of α-amylase.
n-표면 거칠기가 형성된 AlGaInP 수직형 적색 발광다이오드의 광추출효율 증가
서재원,오화섭,송현돈,박경욱,유성욱,박영호,박해성,곽준섭,Seo, Jae-Won,Oh, Hwa-Sub,Song, Hyun-Don,Park, Kyung-Wook,Ryu, Seong-Wook,Park, Yung-Ho,Park, Hae-Sung,Kwak, Joon-Seop 한국진공학회 2008 Applied Science and Convergence Technology Vol.17 No.4
AlGaInP 기반 수직형 적색 LED (Light Emitting Diode)의 광추출효율을 증가시키기 위하여 화학적 etching 기술을 이용하여 n-AlGaInP 표면에 삼각꼴 모양의 거칠기를 형성하였다. Etching은 $H_3PO_4$계의 용액을 이용하여 화학적 etching을 진행 하였다. AlGaInP etching은 광추출효율의 증가와 밀접한 관련을 갖고 있으며 AFM (Atomic Force Microscope)을 이용하여 AlGaInP 표면을 분석하여 약 44 nm의 RMS (root-mean-square) 거칠기가 형성됨을 알 수 있었다. 광추출효율은 기존 수직형 적색 LED보다 거칠기가 형성된 수직형 적색 LED에서 41%의 높은 발광 효율을 보임으로써 고효율 수직형 적색 LED의 가능성을 보였다. In order to increase extraction efficiency of AlGaInP-based vertical RED LEDs, chemical wet etching technique was produced by using a roughened surface with triangle-like morphology. A commonly used $H_3PO_4$-based solution was applied for chemical wet etching. The light extraction of AlGaInP LED was related to the n-side roughed surface morphology. The morphology of roughed surface is analyzed by the atomic force microscope (AFM). As a result, the roughed surface AlGaInP LED has a root-mean-square (RMS) roughness of 44 nm. The brightness shows 41% increase after roughening n-side surface, as compared to the ordinary flat surface LED.