氧化苏木精复合电极测定牛奶中残留青霉素

氧化苏木精复合电极测定牛奶中残留青霉素;电流型电化学生物传感器;氧化苏木精;青霉素     

Duplex Surface Enhanced Raman Scattering-Based Lateral Flow Immunosensor for the Low-Level Detection of Antibiotic Residues in Milk

A duplex surface enhanced Raman scattering (SERS)-based lateral flow immunosensor was established for the simultaneous detection of two common antibiotic residues including tetracycline and penicillin in milk. The newly synthesized Au@Ag nanoparticles were labeled with different Raman molecules including 5,5-dithiobis-2-nitrobenzoic acid (DTNB) or 4-mercaptobenzoic acid (MBA), followed by the conjugation of anti-tetracycline monoclonal antibody or anti-penicillin receptor, forming two kinds of SERS nanoprobes. The two nanoprobes can recognize tetracycline-BSA and ampicillin-BSA, respectively, which facilitates the simultaneous detection of the two types of antibiotics on a single test line. After optimization, detection limits of tetracycline and penicillin as low as 0.015 ng/mL and 0.010 ng/mL, respectively, were achieved. These values were far below those of most of other documented bio-analytical approaches. Moreover, the spiking test demonstrates an excellent assay accuracy with recoveries of 88.8% to 111.3%, and satisfactory assay precision with relative standard deviation below 16%. Consequently, the results demonstrate that the SERS-based lateral flow immunosensor developed in this study has the advantages of excellent assay sensitivity and remarkable multiplexing capability, thus it will have great application potential in food safety monitoring.     

磁性聚合物微球固定化青霉素G酰化酶制备光学纯(S)-2-氯苯甘氨酸

通过反相悬浮聚合法制备了超顺磁性环氧聚合物微球用于固定化青霉素G酰化酶,利用磁性固定化酶催化N-苯乙酰-(R,S)-2-氯苯甘氨酸进行不对称水解反应,制备出(S)-2-氯苯甘氨酸单一对映体。磁性固定化酶催化水解反应的适宜条件为:底物浓度100 mg·m L-1,反应温度和时间30℃和12 h,反应溶液p H 8.0。在此条件下,N-苯乙酰-(R,S)-2-氯苯甘氨酸的转化率为48.8%,产物(S)-2-氯苯甘氨酸的对映体过量值eep达99.4%。磁场下回收磁性固定化青霉素G酰化酶,重复使用6次,底物的转化率和产物的对映体过量值分别为47.8%和91.4%。     

Simultaneous Determination of Procaine Penicillin G and Benzathine Penicillin G by Second Derivative Spectrophotometry

Abstract

A new method for determining the binary mixtures of procaine penicillin G and benzathine penicillin G using “zero-crossing” second derivative spectrophotometry is described. Calibration graphs were linear up to 8.80 10^?5 M for procaine penicillin G and 4.40 10^?5 M for benzathine penicillin G. The method was realized in ethanol/water medium (30 % v/v). A complete and exhaustive statistical analysis of the experimental data was realized to demonstrate the validity of method. The method was applied for determining procaine penicillin G and benzathine penicillin G synthetic mixtures with good results. The procedure does not require any separation step.     

Di-functional magnetic nanoflowers: A highly efficient support for immobilizing penicillin G acylase

The novel di-functional magnetic nanoflowers (DMNF) which had both epoxy groups and hydrophilic catechol as well as phthaloquinone groups capable of covalently coupling of penicillin G acylase (PGA) were characterized by scanning electron microscopy, transmission electron microscope (TEM), vibrating sample magnetometer, N₂ adsorption, and so on. The studies showed that DMNF possessed “hierarchical petal” structure of nanosheets had specific saturation magnetization of 39.7 emu/g and average pore diameter of 25.4 nm as well as specific surface area of 17.28 m²/g. For hydrolysis of penicillin G potassium catalyzed by the PGA immobilized on DMNF with enzyme loading of 106 mg/g-support, its apparent activity reached 2,667 U/g, which benefited from the “hierarchical petal” and large pore structure of the magnetic DMNF leading to high enzyme loading and fast diffusion of substrate molecules to the immobilized PGA to reaction. The apparent activity of the immobilized PGA could keep 2,408 U/g (above 90% of its initial activity) after repeating use for 10 cycles. The magnetic immobilized PGA exhibited excellent operational stability due to covalently coupling of the enzyme molecules between the support by covalent interaction of the amino groups of PGA and the reactive groups of epoxy, catechol, and phthaloquinone groups on DMNF. Furthermore, the PGA displayed good acid and alkaline resistance as well as thermal stability by immobilization using DMNF.     

Evaluation of Certain Pharmaceuticals with Dibromohydantion. V. Determination of Penicillins

Abstract

A new bromometric assay procedure for penicillins was developed, using an organic brominating agent. 1,3-Dibromo, 5,5-dimethylhydantion (DBH). The experimental conditions, the molar ratio as well as the identification of the reaction products were thoroughly studied. The end point could be detected visually or potentiometrically. Spectrophotometric titration could also be performed. The suggested procedure could be successfully applied to pharmaceutical preparations containing penicillins. The percentage recoveries for different penicillins were satisfactory.     

牛奶中2种青霉素残留的高效液相色谱柱前衍生法检测

利用金属铜离子和青霉素G、氨苄西林可在一定条件下形成稳定络合物,建立了一种高效液相色谱快速测定牛奶中2种青霉素残留的方法.样品经酸化乙腈沉淀蛋白,离心处理.色谱柱为Agilent TC C18(150 mm×4.6 mm I.d., 5 μm),甲醇-水为流动相,流速1.5 mL/min,检测波长320 nm,样品在5 min内完成分离检测.青霉素G和氨苄西林的质量浓度分别在0.05 ～1.0 mg/L、0.08 ～2.1 mg/L范围内呈良好的线性关系,相关系数分别为0.995 6、0.998 4.方法的检出限分别为1.5×10-5、2.4×10-5g/L,相对标准偏差分别为2.4%、1.8%(n=5).方法显示出较好的选择性和较高灵敏度,适于牛奶中青霉素G和氨苄西林残留的检测.     

青霉素 V钾的二次微分简易示波伏安法测定

利用青霉素 V钾在 pH=7的 KH2PO4-Na2HPO4缓冲溶液中产生切口的示波特性 , 提出了一种药片中青霉素 V钾的测定方法 - - 二次微分简易示波伏安法 ; 校正曲线的线性范围为 2.0× 10-5～ 2.0× 10-4 mol/L, 检出限为 8× 10-6 mol/L; 对 7.0× 10-5 mol/L青霉素 V钾 8次测定结果的相对标准偏差为 1.6% ; 实验结果表明该法具有分析速度快、仪器装置简单以及药片中的淀粉等物质不干扰测定的优点 .     

MicroGISAXS of Langmuir–Blodgett protein films: effect of temperature on long‐range order

The grazing‐incidence small‐angle X‐ray scattering technique has been used here with a microfocus beamline (µGISAXS) to study the effect of temperature on the protein reorganization taking place in a Langmuir–Schaefer multilayered enzyme film. The study appears quite reproducible in the two enzymes being utilized, penicillin G acylase and urease. In‐plane and out‐of‐plane cuts are used to account for the changes in the film thickness and distance between structures taking place by the process of heating up to 423 K and cooling to room‐temperature. The out‐of‐plane cut suggests that the structures are getting closer and are becoming more organized owing to the heating affect. Merging of layers is likely to occur during the heating and cooling process, leading to a loss of correlation between the interfaces of the layers and to the establishment of long‐range order. The dramatic increase in long‐range order in the Langmuir–Blodgett multilayered enzyme films after heating and cooling, made here apparent by grazing‐incidence small‐angle X‐ray scattering using a microbeam, could in the future open the way to avoiding the bottleneck of protein crystallization for protein structure determination.     

Determination of Penicillins in Milk by a Dual-Optrode Biosensor

Penicillins are the most frequently found antibiotic residues in milk, as they are commonly used for the treatment of bacterial infections in cows. In the present study, we introduce a method for the rapid detection of penicillin residues in raw milk based on the determination of glucose concentration in milk with a dual flow-through biosensor. The molar concentration of glucose in milk is typically over 500 times lower than the concentration of lactose and is highly dependent on the rate of lactose hydrolysis, which is catalyzed by β-galactosidase. Glucose concentrations in milk change with variation in the β-galactosidase activity. β-Galactosidase is an enzyme produced in the microbiota in milk and its activity is inhibited by benzylpenicillin. Spiking milk with benzylpenicillin lowers glucose concentrations in comparison to high-quality milk after short storage intervals. The presence of penicillin in the milk of treated animals resulted in decreased glucose concentrations in comparison with high-quality milk that contained no antibiotics. The glucose concentration in milk samples was followed by the system enabling the elimination of the effects of bacterial respiration in the output with reliable results in less than 1?min.