聚乙二醇化重组人Cu,Zn-SOD改构体制备工艺的优化及其半衰期测定

目的优化聚乙二醇(polyethylene glycol,PEG)化重组人铜锌超氧化物歧化酶(hCu,Zn-SOD)改构体(rmhCu,Zn-SOD)的制备工艺,以期延长其在体内的半衰期。方法以相对分子质量5 000的甲氧基聚乙二醇乙酸-羟基琥珀酰亚胺酯(mPEG-SPA)作为修饰剂,对rmhCu,Zn-SOD蛋白进行化学修饰,并对mPEG-SPA与rmhCu,Zn-SOD的摩尔比、反应缓冲液、反应温度、反应方式及反应时间进行优化;利用硫酸铵沉淀、凝胶过滤色谱法对PEG化rmhCu,Zn-SOD进行分离纯化,并检测其在小鼠体内的半衰期。结果 PEG化rmhCu,Zn-SOD的最佳制备工艺为mPEG-SPA与rmhCu,Zn-SOD的摩尔比1.5∶1,缓冲液为pH 8.5的磷酸盐缓冲液,反应液混匀后4℃静置反应1 h;纯化的修饰产物的纯度约为90%,残余酶活力为(84.3±2.3)%,蛋白修饰率为(65.4±1.9)%;与未修饰的rmhCu,Zn-SOD相比,PEG化rmhCu,Zn-SOD的半衰期延长了约7倍。结论优化了PEG化rmhCu,Zn-SOD的制备工艺;PEG化修饰有效延长了该改构体蛋白在体内的半衰期。     

一种铜锌超氧化物歧化酶突变体的原核表达、纯化及酶活性测定

目的原核表达、纯化一种铜锌超氧化物歧化酶(Cu,Zn-SOD)突变体,并检测其酶活性。方法将经热力学优化的Cu,Zn-SOD突变体基因亚克隆至pET-28a载体中,构建重组表达质粒SOD1-pET-28a,转化入大肠埃希菌BL21(DE3)中,IPTG诱导表达;在500 mL摇瓶培养条件下,通过改变加入Cu、Zn离子的量优化诱导表达条件;表达的重组蛋白经初步纯化后,测定酶活性。结果重组表达质粒SOD-pET-28a经双酶切及测序证明构建正确;表达的重组蛋白相对分子质量约为15 000,主要以可溶性形式表达;工程菌株在500 mL摇瓶培养条件下培养至10 h左右,A₆₀₀至3. 5左右时加入终浓度为0. 1 mmol/L IPTG、0. 2 mmol/L ZnCl₂、0. 5 mmol/L CuSO4,可获得最佳表达量(29. 2%);初步纯化获得的重组蛋白纯度为97. 32%,比活为5. 08×103U/mg。结论成功利用大肠埃希菌表达系统表达了一种经热力学优化的Cu,Zn-SOD突变体,初步纯化的突变体具有较好的酶活性,为进一步摸索大规模生...     

原子吸收光谱法同时测定花生、葵花子中铜和锌

用原子吸收光谱法在同一体系中同时测定花生、葵花子中铜和锌，方法快速简便，铜的RSD为0．72％～0．81％、锌的RSD为0．58％～0．77％，回收率99．48％～100．09％。     

电位溶出法测定饲料中的铜和锌

研究了用微分电位溶出分析测定饲料中的铜、锌含量 ,具有快速、准确、简便等特点。本法测定铜的变异系数为 4 1 % ,加标回收率为 93 2— 1 0 6 8% ;测定锌的变异系数为1 4 % ,加标回收率为 97 1— 1 0 1 3%。     

工业废水中铬、镍、铜、锌、铅的测定

采用火焰原子吸收法测定了工业废水铬，镍，铜，锌，铅的含量，测定的灵敏度较高，相对标准偏差低于7．3％，回收率95％－105％，操作简单快速，结果满意。     

交流示波极普法测定甘草锌胶囊的锌含量

用交流示波极谱法测定了某草锌胶整剂中的含量,本方法与原了吸收分光光度法,EDTA络合滴定法相比较,测定结果相似,简单省时,无须灰化,且终点直观等。     

一种提取猪血铜锌超氧化物歧化酶的新方法

超氧化物歧化酶（SOD）在我国目前虽有生产，但由于技术原因，产量很低，在临床上很少应用。为此，本文从猪血中提取出Cu-Zn-SOD，采用凝胶层析的方法，一步即可生产出纯酶。     

用原子吸收法连续测定钢丝帘线镀层中的铜锌含量

采用原子吸收法对钢丝帘线镀层中的铜、锌含量进行连续测定。试验结果表明,原子吸收法测定铜、锌含量的最佳条件为,狭缝宽度0.5nm,乙炔流速0.9L·min-1,空气流速11L·min-1,燃头高5(刻度值),波长分别为324.7和213.9nm,灯电流分别为3和6mA。在此条件下常见的几种共存离子对测定几乎无干扰,且测定结果标准偏差小。     

容量法测定微量元素预混合饲料中锌、铜含量

探讨了用容量法测定微量元素预混合饲料中锌、铜含量的分析条件;样品用盐酸和硝酸处理后,用EDTA滴定法测定锌、铜合量,再用硫脲掩蔽铜,用EDTA滴定法测定锌含量,总量减去锌含量即可得到铜含量。     

Determination of degradation rate of acrylonitrile polymers

Low‐temperature degradations of acrylonitrile homopolymers and acrylonitrile/acrylamide copolymers in air were investigated by IR and thermogravimetry. The degradation rates of acrylonitrile polymers were determined by measurement of normalized absorbance of ? C?N band and effects of the degradation temperature, time, and comonomer on the rate of degradations were discussed. It was found that the polymers start to degrade as the temperature increased to 150°C. In the temperature range of 180–210°C, values of the rate of polymer degradation were maximal and the rate of degradation of acrylonitrile/acrylamide copolymers was higher compared with that of acrylonitrile homopolymers. At 150°C, acrylonitrile homopolymers had an induction period of about 0.5 h. The rate of degradation of acrylonitrile/acrylamide copolymers showed an obvious trend of increase along with acrylamide concentration, and changes of the rate became less prominent as the weight ratio of acrylamide/acrylonitrile went beyond 5/95. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1511–1514, 2006     

保健酒的配制及其羟基自由基清除率的测定

以罗丹明B(RB)为显色剂,在酸性条件下芬顿(Fenton)体系产生的羟基自由基(·OH)能够迅速氧化RB使其溶液在554 nm处吸光度下降,可测定·OH的产生量;保健酒具有消除·OH的功能,使溶液吸光度下降的程度削弱,保健酒加入体系前后吸光度的差值(ΔA)与保健酒对·OH的清除率成正比,以此建立了·OH清除率的评价方...     

液相电导法测定氯化氢脱析速率

介绍了采用液相电导法测定氯化氢脱析速率,从而测试聚氯乙烯树脂稳定性的方法,该方法能提供PVC树脂脱HCl的诱导期、降解速率及降解全过程的信息,与刚果红和老化白度法相比,能确切地反映树脂的热稳定性。     

Determination of isopropyl peroxydicarbonate decomposition rate constant using EPR

The decomposition rate constant, k_d, of isopropyl peroxydicarbonate in toluene at 23.3°C was determined using electron paramagnetic resonance techniques (EPR). Diphenylpicrylhydrazyl (DPPH) was used to monitor the formation of radicals. Because DPPH has a strong absorption spectrum on the EPR, the accuracy of measuring small changes in the indicator concentration should be greater than measuring small concentrations of primary radicals. A value for k_d of 4.5 × 10^?7 sec^?1 was obtained. This is in good agreement with previously published values.     

The effect of surface modification on the cathodic disbondment rate of epoxy and alkyd coatings

Surface modification of carbon steel substrates using appropriate functionalised silanes was carried out to investigate their effect on the dry and wet adhesion strength, and the cathodic disbondment rate, of coating binders based on epoxy and alkyd chemistries. Results show that pre-treatment of the steel substrate with 3-glycidoxypropyltrimethoxy silane (3-GPS) enhanced the dry and wet adhesion of an epoxy-based coating. Similarly, pre-treatment with 3-aminopropyltriethoxy silane (3-APS) enhanced the dry and wet adhesion of alkyd-based systems. However, although pre-treatment with 3-GPS reduced the cathodic disbondment rate for epoxy by a factor of 3, no effect on the disbondment rate for alkyd-based binders on substrates pre-treated with 3-APS was found. This strongly suggests that cathodic disbondment of epoxy proceeds by disruption of interfacial bonds (i.e. at the binder/substrate interface) but that disbondment of alkyds proceeds by direct degradation of the binder and that the interface plays little part in the process.     

Determination of recombination and attachment rate constants from ballistic experiments

We present measurements of the electron concentration in wakes behind aluminum spherical models flying in air with velocity 3.4–5.7 km/sec at a pressure of 10–80 torr. We have calculated the heating and entrainment of aluminum from the surface of the models as they move within the flight range. We show that condensation of Al vapor may occur at distances of more than 100 diameters of the body and pressure ≳80 torr. We pose and solve the inverse problem of determining (from experimental data) the effective attachment coefficient for attachment to air molecules and the attachment rate constants for AlO+e→AlO⁻, AlO₂+e→AlO₂ ⁻. Scientific-Research Institute of Mechanics, Moscow State University, Moscow 119899. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 5, pp. 70–82, September–October, 1995.     

Determination of the rate constants for a CECE reduction mechanism

We have made a generalized treatment of first-order kinetic processes in dc polarography, obtaining approximate analytic expressions, applicable to any conditions. This treatment is applied to the electrochemical reduction of O-nitrophenol, which undergoes a CECE mechanism in which both chemical stages influence the process simultaneously. All the rate constants involved in the process have been calculated.