Expression and Characterization of an Active Chimeric Protein of Human Extracellular Superoxide Dismutase and hCuZnSOD in Pichiapastoris

Mammalian cells express two isoforms of Cu-and Zn-containing superoxide dismutases(SODs),CuZnSOD and extracellular SOD(EC-SOD),involved in the defense system against reactive oxygen species(ROS).The two SODs have structurally homologous centre domain with distinct N-and C-terminuses,resulting in the different characteristics of the structure and function of the two molecules.We generated a hybrid SOD molecule(namely hySOD) via replacing the N-and C-terminuses of hCuZnSOD with the counterparts of hEC-SOD.The...     

有限长密绕圆柱形螺线管自感系数的精确表达式

对于有限长密绕圆柱形螺线管,首先用贝塞尔函数展开法推导出自感系数的积分形式的表达式,然后用直接积分的方法得出两个级数形式的自感系数表达式,最后对这两个表达式作了简要的分析与比较.     

收缩喷嘴中的湍流Ⅰ——边界层解

应用边界层积分法,研究锥形喷嘴入口区域中湍动涡流的发展.球面坐标系中的控制方程,通过边界层的假定得到简化,并对边界层进行了积分.应用4阶Adams预测校正法求解该微分方程组.入口区域的切向和轴向速度,分别应用自由涡流和均匀速度分布来表示.由于缺乏收缩喷嘴中涡流的实验数据,需要用数值模拟对该发展模式进行逆向验证.数值模拟的结果证明,该解析模型在预测边界层参数中的能力,例如边界层的生长、剪切率和边界层厚度,以及不同锥度角时的涡流强度衰减率等.为所提出的方法引进一个简明而有效的程序,用以研究几何形状收缩设备内的边界层参数.     

Single‐run capillary electrophoresis method for the fast simultaneous determination of amoxicillin,clavulanate, and potassium

We report a new fast method for the simultaneous determination of amoxicillin, clavulanate, and potassium by capillary electrophoresis with capacitively coupled contactless conductivity detection. Samples containing potassium as the cation, and both amoxicillin and clavulanate as anions were determined simultaneously in a single run (in less than 45 s) using 10 mmol/L of both 2‐amino‐2‐hydroxymethyl‐propane‐1,3‐diol and 3‐{[2‐hydroxy‐1,1‐bis(hydroxymethyl)ethyl]amino}‐1‐propanesulfonic acid (pH 8.4) as the background electrolyte. Limits of detection were 25.0, 5.0, and 4.0 μmol/L for amoxicillin, clavulanate, and potassium, respectively. The proposed method is inexpensive, simple, fast (75 injections h⁻¹), environment friendly (minimal waste generation), and accurate (recovery values between 98 and 103%). The results obtained with the proposed method were statistically similar (95% confidence level) to those obtained by using high‐performance liquid chromatography (amoxicillin and clavulanate) and flame photometry (potassium).     

AibA/AibB Induces an Intramolecular Decarboxylation in Isovalerate Biosynthesis by Myxococcus xanthus

Isovaleryl coenzyme A (IV‐CoA) is an important precursor for iso ‐fatty acids and lipids. It acts in the development of myxobacteria, which can produce this compound from acetyl‐CoA through alternative IV‐CoA biosynthesis (aib). A central reaction of aib is catalyzed by AibA/AibB, which acts as a cofactor‐free decarboxylase despite belonging to the family of CoA‐transferases. We developed an efficient expression system for AibA/AibB that allowed the determination of high‐resolution crystal structures in complex with different ligands. Through mutational studies, we show that an active‐site cysteine previously proposed to be involved in decarboxylation is not required for activity. Instead, AibA/AibB seems to induce an intramolecular decarboxylation by binding its substrate in a hydrophobic cavity and forcing it into a bent conformation. Our study opens opportunities for synthetic biology studies, since AibA/AibB may be suitable for the production of isobutene, a precursor of biofuels and chemicals.     

Simple and robust digital holography for high-resolution imaging

Based on the point spread function of holographic system,the lateral resolution of digital holographic imaging system without any pre-magnification is studied.The expression of resolution limitation of holographic imaging system is thus presented.We investigate the possibilities to improve the lateral resolution.The simple experimental setup with an off-axis arrangement is built.By using a U.S.Air Force(USAF)test target as microscopic object,the recorded holograms are reconstructed digitally based on the principle of Fresnel diffraction.The lateral resolution of 2.76 μm without any pre-magnification is demonstrated experimentally,which matches the theoretical prediction well.     

Ab initio multi-reference configuration interaction of the low-lying states of the AsP molecule

Nine low-lying electronic states of the AsP molecule, including Σ , Ⅱ, and △ symmetries with singlet, triplet, and quintet spin multiplicities, are studied using multi-reference configuration interaction method.The potential energy curves and the spectroscopic constants of these nine states are determined, and compared with the experimental observed data as well as other theoretical works available at present.Three quintet states are reported for the first time.Furthermore, the analytical potential energy functions of these states are fitted using Murrell-Sorbie function and least square fitting method.     

温控表达载体的构建及HIV-1p24的表达与纯化

通过改造原核表达载体ｐ Ｂ Ｖ２２０ 和ｐ Ｅ Ｔ２８,构建出了一种新的通用型温控原核表达载体ｐ Ｖ Ｖ５,该载体携带 Ｐｒ Ｐｌ串联温控启动子以及 Ｈｉｓ Ｔａｇ 的纯化标签,利于目的蛋白的表达与纯化将 Ｈ Ｉ Ｖ１ ｇａｇ 基因的１１４８１８５７ 编码序列分别插入到ｐ Ｖ Ｖ５ｂ、ｐ Ｅ Ｔ２８ｂ 的相应位点,构建了重组表达质粒 ｐ Ｅ Ｇ１ｂ、ｐ Ｂ Ｇ７ｂ,二者在不同受体菌中,表达重组蛋白的量分别占全菌体蛋白总量的 ４２％ 和２８％ 表达产物为融合蛋白并主要以包涵体的形式存在 该蛋白 Ｎ 端与含６ 个组氨酸在内的３０ 个氨基酸残基的多肽相连,利用 Ｉ Ｍ Ａ Ｃ金属螯和层析柱,对包涵体中的重组ｐ２４ 蛋白进行纯化, 其纯度超过 ８０％ ;对上清中的可溶性ｐ２４ 蛋白进行纯化,产物最终纯度超过６７％ 纯化后的重组蛋白可与 Ｈ Ｉ Ｖ１ 型标准阳性血清发生较强的免疫学反应     

HAMILTONIAN SYSTEM AND SIMPLETIC GEOMETRY IN MECHANICS OF COMPOSITE MATERIALS (Ⅱ)——PLANE STRESS PROBLEM

Fundamental theory presented in Part (I)^[8] is used to analyze anisotropic plane stress problems. First we construct the generalized variational principle to enter Hamiltonian system and get Hamiltonian differential operator matrix; then we solve eigen problem; finally, we present the process of obtaining analytical solutions and semi-analytical solutions for anisotropic plane stress problems on rectangular area.