Microcalorimetric studies on the non-competitive inhibition of bovine liver arginase

Two methods, e.g. initial rate method and thermokinetic reduced extent method were presented for studies on non-competitive inhibition. Arginase-catalyzed the hydrolysis of L-arginine toL-ornithine and urea and the inhibition of this reaction by sodium fluoride were studied in the absence and presence of exogenous of Mn²⁺at 37°C in 40 mM sodium barbiturate-hydrochloric acid buffer solution (pH 7.4). Both methods were successively used to determine the values of K₁. The advances and disadvantages of each method were compared in this paper. Exogenous Mn²⁺ could result in more sensitivity of arginase to F^-1. Since the inhibition of arginase by F^-1 depends on the pH values of the reaction system and behave as a non-competitive inhibition, it probably due to its small volume and high electronic density allow it access to the activity site of the enzyme and replaces of μ-OH₂ (or μ-OH) as the bridge ligand with Mn(II, II) cluster. However, further studies are necessary to determine the modes of interaction of F^-1 with bovine liver arginase. This revised version was published online in August 2006 with corrections to the Cover Date.     

Probing in vitro digestion at oil–water interfaces

Interfacial layers have been widely applied to study the formation and stability of emulsion-based systems. However, the application of isolated interfaces to address digestibility of emulsions is often limited because of the complexity of experimental methods and results. This review summarizes the latest developments in analytical methods and literature data on effects of digestion on interfacial layers. Particular emphasis is given to understand the changes on interfacial magnitudes during oral, gastric, and duodenal digestion, either applied separately or sequentially. Limitations of interfacial aspects and key factors that influence emulsion microstructure in bulk and lipid digestion are identified. Understanding the behavior of interfacial layers upon gastrointestinal digestion promotes an accurate tracking of the physiological fate of emulsions.     

Fluorescence immunological determination of immunoglobulin G in human serum by high-performance liquid gel-permeation chromatography

Summary A high-performance liquid gel-permeation chromatographic method is described for the determination of human serum immunoglobulin G (IgG) by separating the fluorescent immuno complex from the free fluorescence-labeled antibody. Fluorescence-labeled antibody used in this study was fluorescein isothiocyanate (FITC)-labeled Fab fragment goat anti-human IgG (anti-IgG Fab). Immuno complexes and antibody of different molecular sizes can be separated. FITC-labeled anti-IgG Fab was added to the serum and the mixture is passed through the column. An immuno complex separates as well-delineated peak in the column void volume, and was measured by the fluorescence of the column eluate (Ex=490nm, Em=520nm). The total analysis time for a serum sample was approximately 15min. The minimum detection limit was 25 mg/dl. The relative standard deviation was below 2% (peak area). The results of the HPL-GPC analysis correlate well with those obtained by laser nephelometric assay (r=0.992).     

牛血清蛋白对手性物质的毛细管电泳拆分

采用聚氧乙烯涂层毛细管柱，以牛血清蛋白(BSA)为手性添加剂，运用毛细管电泳电导检测对手性药物沙丁胺醇和多沙唑嗪以及DL-组氨酸、色氨酸、苏氨酸进行拆分。考察了涂层柱的稳定性和重现性。对影响手性分离的主要因素：缓冲溶液的浓度和酸度、BSA的浓度、有机溶剂的种类和浓度以及分离电压进行了系统的研究。结果表明：在选择的最佳实验条件下，各对映异构体在22min内得到基线分离。     

Silicone-modified starch/protein microparticles: protecting biopolymers with a hydrophobic coating

Silicone-coated starch/protein (human serum albumin, HSA) microparticles were prepared by precipitation of a starch/HSA/DMSO/water (water-in-oil) emulsion into acetone containing a silicone: the silicone polymer was either unfunctionalized (SiMe₃ terminated, PDMS) or functionalized at its termini with Si(OEt)₃ groups (TES-PDMS). The microparticles of approximate diameter 2–7 μm were highly hydrophobic with advancing contact angles 115°. Over several minutes, however, the contact angle decreased to ca. 40–70°. Soxhlet extraction with water led to degradation of the microparticles, irrespective of the nature of their silicone coating, as evidenced by release of the protein from them. Intraperitoneal (IP) or gastric administration of the two different particles to mice, however, showed a clear difference between the two silicones. The microparticles coated with either PDMS or TES-PDMS led to very different immune responses. Oral administration of the microparticles prepared with functionalized silicone elicited a significant production of antibodies, whereas the particles prepared with the unfunctionalized silicone (PDMS) were only weakly active. By contrast, the IP results demonstrated that particles coated with PDMS elicited an immune response that was established much more rapidly than with the particles modified with TES-PDMS. It is proposed that the TES-PDMS forms a physically adhering film or covalent bond to the protein molecules, which serves to protect the microparticle from biological degradation in the gut and/or facilitates the microparticle/protein interaction with the immune system.     

Studies on the Interaction of Beryllon Ш with Proteins by Voltammetric Technique and its Application

A new quantitative determination method of proteins using beryllon Ш by voltammetric technique was developed in this paper. In pH 3.5 Britton-Robinson (B-R) buffer solution, beryllon Ш can bind with human serum albumin (HSA) to form an electro-inactive supermolecular complex. Beryllon Ш has a well-defined voltammetric reduction peak at -0.38 V (vs. SCE) and the addition of protein in this solution can cause the decrease of the reductive peak current. Based on the decrease of the reduction peak current, a new electrochemical method for the determination of HSA was established with linear range of 1.0~40.0 mg/L and the detection limit of 1.0 mg/L. This method is further applied to the determination of real sample of healthy human serum.     

2型糖尿病患者血清钙镁与甲状腺激素含量变化及临床意义

为了监测 2型糖尿病人血清钙、镁和甲状腺激素含量 ,分析其临床意义及相关性 ,应用放射免疫分析法测定了 1 1 5例 2型糖尿病及 1 5 0例健康人血清甲状腺激素含量。同时用美国杜邦RXL自动生化仪测定了其血清钙、镁含量。结果表明 ,在 2型糖尿病伴有明显并发症者血镁、FT3水平明显降低 (P <0 0 5 ) ,钙镁两种元素与甲状腺激素水平无明显相关性。 2型糖尿病患者适当补镁对预防其并发症是有益的 ,测定FT3 等可作为判断 2型糖尿病严重程度和估计预后的参考指标。     

化学发光分析法测定动物蛋白粉等样品中的锰

基于Mn(Ⅱ) 邻菲罗啉对鲁米诺 KIO4化学发光体系的催化作用建立了测定Mn(Ⅱ)的分析方法。Mn(Ⅱ)质量浓度在2.0×10-6～5.0×10-5mg/mL范围与发光强度呈线性响应,回归方程为ICL=0.6+1.39×106ρ(mg/mL),检出限为2.0×10-6mg/mL。Cr3+、Fe2+、Co2+、Au3+等离子有干扰,使用EDTA、F-、8 羟基喹啉等为掩蔽剂可消除或降低干扰。将该法应用于生物化工产品丙酸钙、动物蛋白粉等中痕量锰的测定,加标回收率98%～102%,10次测定RSD为4 6%。将测定的结果与原子吸收法比较,相对偏差≤±3%。     

Monitoring of sources of clinical exposure to nickel

Due to the widespread uses of Ni and Ni alloys, patients undergoing medical treatments can experience inadvertent exposure to the metal, present as a contaminant in fluids for intravenous administration or released from surgical implants and other medical devices. Because of the risk of acute allergic reactions in Ni-sensitive subjects, sources of metal exposure within medical care and its concentrations in biological fluids of potentially exposed patients should be periodically monitored, using reliable analytical procedures, which include strict measures of contamination control. The results of a recent survey on the concentrations of Ni and other potentially toxic metals in human albumin solutions are reported.     

阴阳离子型表面活性剂双水相萃取色氨酸衍生物和牛血清白蛋白

溴化十二烷基三乙胺（Ｃ１２ＮＥ）和十二烷基硫酸钠（ＳＤＳ）在一定条件下混合可以形成具有清晰界面的两个水相，称为阴阳离子型表面活性剂双水相。作者研究了利用该双水相萃取３种色氨酸衍生物和牛血清白蛋白的可能性．文中采用工作曲线校正扣除表面活性剂背景的影响，萃取结果准确可信。