The effect of surface coverage on conformation changes of bovine serum albumin molecules at the air-solution interface detected by sum frequency generation vibrational spectroscopy

The air-BSA solution interface has been investigated by various techniques for years. From these studies we know that BSA molecules segregate at the BSA solution-air interface, and the surface coverage increases with the increase of the bulk solution concentration. However, questions still remain as to whether the protein changes conformation, orientation, or a combination of the two upon adsorption. In this paper, by using sum frequency generation (SFG) vibrational spectroscopy we found that the conformation of interfacial BSA molecules changes dramatically at the solution-air interface, compared to that of the native BSA in solution. The hydrophobic methyl groups of BSA molecules at this interface tend to align along the surface normal. The degree of such conformational changes of surface BSA molecules depend on the surface coverage, indicating that the protein-protein interaction plays a very important role in determining the conformation of interfacial protein molecules. At very low surface concentration, the adsorbed BSA molecules unfold substantially. Our results can provide a molecular interpretation of results obtained from other studies such as protein layer thickness and surface tension measurements of protein solution.     

C反应蛋白免疫电极的研究

C反应蛋白(CRP)是临床医学中重要的检验项目之一。本文以醋酸纤维素-戊二醛-己二胺载体膜与自制的原电极研制成非标记CRP免疫电极。研究了载体膜的组成对电极灵敏度的影响,并采用均匀设计法对载体膜的活化条件、抗原抗体结合时间以及电极测试条件等进行了优化。该电极响应快、灵敏度高、重现性和稳定性良好。在最佳实验条件下,电极线性范围为1.8～60μg/ml,所得线性回归方程为E=0.2+0.091[CRP];相关系数0.9989。在用于血清样品的测定中,取得满意结果。     

On-column amperometric detection in capillary electrophoresis with an improved high-voltage electric field decoupler

The analysis of polyamide-6 oligomers and polymer is usually performed with expensive fluorinated alcohols like 2,2,2-trifluoroethanol (TFE) or 1,1,1,3,3,3-hexafluoroisopropanol (HFIP). Formic acid is well known as a mobile phase additive to adjust pH in reversed-phase high-performance liquid chromatography. However, formic acid is seldom used as a modifier to perform gradient elution chromatography on octadecyl-modified silica-based columns. Here we demonstrate the determination of cyclic and linear polyamide-6 oligomers using formic acid as a modifier on an octadecyl-modified silica-based column. This column was shown to be stable for more than 5000 column volumes, even when a mobile phase of 65-95% formic acid in water at a flow of 1 ml/min is applied. With formic acid under the conditions used (65-95% formic acid in water) the oligomers are retained on the column, while the polymer does not precipitate. In comparison, during adsorption and separation with a HFIP gradient, precipitation of the polymer occurs. The implications of the different separation mechanisms, i.e., adsorption vs. precipitation chromatography are discussed. Loadability is shown to be much better with the formic acid system. However, with formic acid as a modifier UV detection below 250 nm is not feasible. The less sensitive evaporative light scattering detector is used to detect the polyamide oligomers in the formic acid phase. In addition it is shown that capillary zone electrophoresis (CZE) with UV-absorbance detection using HFIP is an attractive combination as HFIP is UV-transparent and CZE allows low modifier consumption.     

New Approach to Synthesis of 6,7—Dimethoxyisatin

A new approach to synthesis of 6,7-dimethoxyisatin is reported.2-nitro-3,4-dimethoxy mandelonitrile in glacial acetic acid was treated with the solution of stannous chloride in hydrochloric acid to give 6,7-dimethoxyisatin in a high yield.     

Determination of traces of bismuth by quenching of solid-substrate room-temperature phosphorescence from morin-labeled silicon dioxide nano-particles

Silicon dioxide nano-particles, diameter 50 nm, containing morin (morin–SiO₂) have been synthesized by the sol–gel method. They emit strong and stable room-temperature phosphorescence (SS-RTP) on filter paper as substrate, and bismuth can quench the intensity of the SS-RTP. On this basis a new morin–SiO₂ solid-substrate room-temperature phosphorescence-quenching method has been established for determination of traces of bismuth. Reduction of phosphorescence intensity (I_p) is directly proportional to the concentration of bismuth in the working range 0.16–14.4 ag spot^–1 (sample volume 0.40 L spot^–1, corresponding to the concentration range 0.40–36.0 fg mL^–1). The regression equation of the working curve is I_p=14.86+5.279×[Bi³⁺] (ag spot^–1) (n=6, r=0.9982). The detection limit of this method is 0.026 ag spot^–1 (corresponding to a concentration of 6.5×10^–17 g mL^–1).This sensitive, reproducible and accurate method has been used for successful analysis of real samples.     

Development of a liquid chromatography/tandem mass spectrometry assay for the quantification of PM00104, a novel antineoplastic agent, in mouse, rat, dog, and human plasma

A rapid and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay was developed and validated to quantify a novel antineoplastic agent, PM00104, in mouse, rat, dog, and human plasma. The method was validated to demonstrate the specificity, limit of quantification (LOQ), accuracy, and precision of measurements. The calibration range for PM00104 was established using PM00104 standards from 0.01-5.0 ng/mL in blank plasma. The selected reaction monitoring (SRM), based on the m/z 692.2 --> 218.2 transition, was specific for PM00104, and that based on the m/z 697.2 --> 218.2 transition was specific for PM00104 ((13)C(2),(2)H(3)) (the internal standard, IS); no endogenous materials interfered with the analysis of PM00104 and IS from blank plasma. The assay was linear over the concentration range 0.01-5.0 ng/mL. The correlation coefficients for the calibration curves ranged from 0.9981-0.9999. The mean intra-day and inter-day accuracies for all calibration standards (n = 8) ranged from 97-105% (< or =5% bias) in human plasma, and the mean inter-day precision for all calibration standards was less than 8.5%. The mean intra- and inter-day assay accuracy for all quality control (QC) replicates in human plasma (n = 9), determined at each QC level throughout the validated runs, ranged from 96-112% (< or =12% bias) and from 102-105% (< or =5% bias), respectively. The mean intra- and inter-day assay precision was less than 15.0 and 11.8% for all QC levels, respectively. For the QC samples prepared in animal species plasma, the %CV values of the assays ranged from 1.8-8.8% in mouse plasma, from 3.7-13.8% in rat plasma, and from 3.0-7.2% in dog plasma. The assay accuracies ranged from 92-102% (< or =8% bias) for all QC levels prepared in mouse plasma; ranged from 93-106% (< or =7% bias) in rat plasma; and ranged from 95-114% (< or =14% bias) in dog plasma. The assay has been used to support preclinical pharmacokinetic and toxicokinetic studies and is currently used to measure PM00104 plasma concentrations to support clinical trials.     

Z‐bpy,a New C2‐Symmetric Bipyridine Ligand and Its Application in Enantioselective Copper(I)‐Catalyzed Cyclopropanation of Olefins

A rigid C₂‐symmetric chiral bipyridine ligand Z‐bpy with a triptycene‐like backbone was designed and synthesized from simple chemicals in a scalable route. Using this new ligand, copper(I) catalyzed cyclopropanation of styrenes with commercial ethyl diazoacetate produced various corresponding cyclopropanes in high yields, diastereoselectivity and enantioselectivity up to 97% ee.     

环己烷催化氧化制取顺酐和醋酸的催化剂研究

为研究气态环己烷催化氧化制取顺酐及醋酸的新反应，采取不同的方法制备了系列固体VPO催化剂.借助XRD、FT-IR对催化剂进行了主体晶相确定，用氧化还原滴定方法测定了不同晶相催化剂中钒的平均氧化数.结合催化反应的活性评价，发现催化剂主体晶相、结晶度、活化气氛和催化剂的V4＋/V5＋比均对目标反应的催化活性产生影响，5种催化剂中以(VO)2P2O7晶相催化剂的活性为最高.