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将来源于嗜热古菌Sulfolobus tokodaii的脱卤酶(L-HADST)基因克隆到载体p ET28b,转化大肠杆菌BL21(DE3)进行表达,在蛋白的N末端带有6个组氨酸融合标签,纯化后经聚丙烯酰胺凝胶电泳显示融合蛋白的分子量约为25000.融合蛋白催化2-氯丙酸(2-CPA)的最适反应温度为70℃,最适p H值为9.5.以外消旋2-CPA为底物生产D-乳酸,利用HPLC检测反应液中2-CPA及乳酸的变化,发现L-HADST只催化L-2-CPA脱氯反应.对酶催化反应条件进行了优化,结果表明,在p H值为9.5,温度为60℃的条件下,当反应体系中缓冲液浓度为3 mol/L,底物浓度为0.5 mol/L,酶浓度为3×104U/L时有较高的底物转化率及乳酸生成量.依据条件优化结果可知,影响反应速度的因素有底物浓度、缓冲液浓度以及酶浓度,其中底物浓度变化对转换率的影响最明显. 相似文献
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系统地研究了利用分子束外延方法在GaAs(001) 衬底上外延生长的MnAlx薄膜的结构和垂直易磁化特性随组分及生长温度的依赖关系. 磁性测试表明, 可在较大组分范围内 (0.4≤x≤1.2) 获得大矫顽力的垂直易磁化MnAlx薄膜, 然而同步辐射X射线衍射和磁性测试发现当x≤0.6时MnAl薄膜出现较多的软磁相, 当x >0.9时, MnAl薄膜晶体质量和化学有序度逐渐降低, 组分为MnAl0.9时制备的薄膜有最好的[001]取向. 随着生长温度的增加, MnAl0.9薄膜的有序度、垂直磁各向异性常数、矫顽力和剩磁比均增加, 350℃时制备的MnAl0.9薄膜化学有序度高达0.9, 其磁化强度、剩磁比、矫顽力和垂直磁各向异性常数分别为265emu/cm3、93.3%、8.3kOe (1 Oe=79.5775A/m)和7.74Merg/cm3 (1 erg=10-7J). 不含贵金属及稀土元素、良好的垂直易磁化性质、 与半导体材料结构良好的兼容性以及磁性能随不同生长条件的可调控 性使得MnAl薄膜有潜力应用于多种自旋电子学器件.
关键词:
分子束外延
大矫顽力材料
磁各向异性 相似文献
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利用椭圆偏振光谱仪和原子力显微镜,研究了相同温度下不同退火气氛及压强处理对溶液旋涂法制备a-IGZO光学特性和薄膜微观结构的影响。实验结果表明,当退火气氛为O2时,压强由0.1 MPa增加到1.5 MPa,薄膜的光学带隙由3.23 eV增大到3.31 eV,表面粗糙层由6.77 nm降低到4.77 nm。与N2气氛相比,1.5 MPa O2气氛下薄膜的光学带隙有所提高,表面粗糙度也有所降低。因此,在1.5 MPa O2气氛下,可以有效降低薄膜内部有机物的残留及缺陷,形成更加致密的非晶a-IGZO薄膜。 相似文献
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Structure and Magnetic Properties of (In,Mn)As Based Core-Shell Nanowires Grown on Si(111) by Molecular-Beam Epitaxy 下载免费PDF全文
We report the structure and magnetic properties of (In,Mn)As based core-shell nanowires grown on Si (111) by molecular-beam epitaxy. Compared to the core InAs nanowire with a flat side facet and consistent diameter, the core-shell nanowire shows a rough sidewall and an inverse tapered geometry. X-ray diffraction, transmission electron microscopy and energy-dispersive x-ray spectroscopy show that (In,Mn)As is formed on the side facets of In As nanowires with a mixture ofwurtzite and zinc-blende structures. Two ferromagnetic transition temperatures of (In,Mn)As from magnetic measurement data are observed: one is less than 25 K, which could be attributed to the magnetic phase with diluted Mn atoms in the InAs matrix, and the other is at ~300 K, which may originate from the undetectable secondary phases such as MnAs nanoclusters. The synthesis of (In,Mn)As based core-shell nanowires provides valuable information to exploit a new type of spintronic nano-materials. 相似文献
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Quantum oscillations in a hexagonal boron nitride-supported single crystalline InSb nanosheet 下载免费PDF全文
A gated Hall-bar device is made from an epitaxially grown, free-standing InSb nanosheet on a hexagonal boron nitride (hBN) dielectric/graphite gate structure and the electron transport properties in the InSb nanosheet are studied by gate-transfer characteristic and magnetotransport measurements at low temperatures. The measurements show that the carriers in the InSb nanosheet are of electrons and the carrier density in the nanosheet can be highly efficiently tuned by the graphite gate. The mobility of the electrons in the InSb nanosheet is extracted from low-field magneotransport measurements and a value of the mobility exceeding $\sim 1.8\times10^4$ cm$^{2}\cdot$V$^{-1}\cdot$s$^{-1}$ is found. High-field magentotransport measurements show well-defined Shubnikov-de Haas (SdH) oscillations in the longitudinal resistance of the InSb nanosheet. Temperature-dependent measurements of the SdH oscillations are carried out and key transport parameters, including the electron effective mass $m^{\ast }\sim 0.028 m_{0}$ and the quantum lifetime $\tau \sim 0.046 $ ps, in the InSb nanosheet are extracted. It is for the first time that such experimental measurements have been reported for a free-standing InSb nanosheet and the results obtained indicate that InSb nanosheet/hBN/graphite gate structures can be used to develop advanced quantum devices for novel physics studies and for quantum technology applications. 相似文献
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An ultra-thin Co2MnSi(0.5 nm)/Mn Ga(1.5 nm) bilayer capped with Pt(5 nm) has been successfully grown by molecular-beam epitaxy.It is a potential candidate of synthetic antiferromagnets due to antiferromagnetic coupling between Co2MnSi and MnGa,which is a promising skyrmion-racetrack-memory medium without skyrmion Hall effect after capping with a Pt layer.Unusual humps in transverse Hall resistance loops are clearly observed in the temperature range from 260 to 400 K.This an... 相似文献
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