离子液体中聚乙二醇维生素E琥珀酸酯的合成

以离子液体为催化剂,由维生素E经两步酯化反应合成了聚乙二醇1000(PEG1000)维生素E琥珀酸酯。以离子液体1-(N',N'-二甲胺乙基)-3-甲基咪唑四氟硼酸盐为催化剂、1,2-二氯乙烷为助溶剂、维生素E与琥珀酸酐摩尔比为1:1.2,在80 ℃条件下反应4 h,维生素E琥珀酸酯(TAS)的产率为90%。以1-丙磺酸基-3-甲基咪唑硫酸氢盐/甲苯为反应体系,TAS与PEG1000摩尔比为1:2,在100 ℃下反应5 h,PEG1000维生素E琥珀酸酯(TPGS)收率为91%。     

Thiol redox status evaluation in red blood cells by capillary electrophoresis-laser induced fluorescence detection

Thiols and in particular glutathione (GSH) play a central role in human metabolism, including the detoxification of xenobiotics, cell homeostasis, radioprotection, and antioxidant defence. Here, a new method is provided for the measurement of reduced and total forms of thiols in red blood cells. In order to minimize oxidation of reduced thiols, a water erythrocyte lysis (15 min at 4 degrees C) was performed followed by a protein precipitation step with acetonitrile. The supernatant was rapidly derivatized with 5-iodoacetoamidefluorescein that trapped thiol groups, thus minimizing auto-oxidation. Derivatized samples were separated in a 57 cm x 75 microm ID capillary by using 5 mmol/L sodium phosphate, 4 mmol/L boric acid as electrolyte solution with 75 mmol/L N-methyl-D-glucamine at pH 11.0. Under these conditions, cysteinylglycine (CysGly), cysteine (Cys), glutathione, and gamma-glutamylcysteine (GluCys) were baseline-resolved in approximately 4 min. Precision tests showed a good repeatability of our method both for migration times (coefficient of variation CV < 0.8%) and areas (CV < 3.3%). Furthermore, a good reproducibility of intrassay and interassay tests was obtained (CV < 5% and CV < 8%, respectively). The method was employed to investigate the effect of acidic precipitation on intracellular thiol concentration. Our data suggest that sample acidification causes a modification of the measured redox thiol status due to the development of a pro-oxidant environment; moreover, the thiol redox status of red blood cells was evaluated in 22 healthy volunteers.     

Kinetic catalytic determination of trace Cu(II) in water samples with the thioglycolic/thiolactic acid–chromate reaction

The use of two novel similar indicator reactions as applied to the kinetic determination of Cu(II) in water is investigated. The methods rely on the catalytic effect of the analyte on the oxidation of thioglycolic (TGA) and thiolactic (TLA) acids by chromate in acidic media. The extent of the reactions was followed spectrophotometrically at 345 nm. Pseudo-first-order rate coefficients, k_obsd, were determined as a function of catalyst concentration. Interference of Fe(III) and Pb(II) was suppressed by complexation with pyrophosphate. For the reaction of TGA, a linear regression for k_obsd versus [Cu(II)] was obtained for the entire concentration range considered. Although the plot corresponding to TLA oxidation exhibits a sharp change of slope at approximately 1.8×10^–5 M Cu(II), it can still be described effectively by two linear regressions with different slopes. The reaction of TGA is more sensitive than that of TLA at low Cu(II) concentration. The opposite is true for higher catalyst contents. The detection limits were 65 gL^–1 for TGA and of 80 gL^–1 for TLA oxidation, respectively. The relative standard deviations, of 0.4% for TGA and 1.1% for TLA oxidation, respectively, were obtained for five replicate runs at 1000 g L^–1. Samples of river and wastewater from the mining region of Baia-Mare, Northern Romania were analyzed using the more sensitive reaction of thioglycolic acid. Results were compared to those obtained by the officially standardized methods. Good agreement was obtained, even for an untreated sample. Measurements did not require prior separation of interfering species.     

Chromatographic characterization of a hexapeptide containing three thiol groups,intrinsic to the metallothionein structure

Summary The hexapeptide Lys-Cys-Thr-Cys-Cys-Ala [56–61] MT I is a molecule intrinsic to the metallothionein structure. Its chromatographic behaviour on a reversed-phase column, using electrochemical detection has been studied in order to get a better understanding of its chemical stability under various conditions. The chromatogram of the peptide consists of two peaks. The optimization procedure for their separation is presented and a hydrodynamic voltammogram has been generated. The relative proportion of the two peaks can vary with experimental conditions and is clearly dependent of the peptide concentration. Following the various experiments to which the peptide was submitted, namely elution after air oxidation, under inert atmosphere, in basic pH, after addition of an oxidizing agent (H₂O₂) and after addition of a reducing agent (2-mercaptoethanol), a reaction scheme was suggested: transformations of the reduced hexapeptide (three free thiol groups) into—as a first step—its intramolecular oxidized form (one SS bond, one free SH) and then into—as a second step—the fully oxidized dimeric form (no more free SH). Electrochemical detection allows a quantitative follow-up of the thiol oxidation and hence, of the disappearance of the reduced peptide.     

Amperometric Biosensors Based on Recombinant Bacterial Laccase CotA for Hydroquinone Determination

In this study, stable CotA laccase from Bacillus subtilis 168 was adsorbed on electrode modified with a thiol graphene‐gold nanoparticle (thGP‐AuNPs) nanocomposite film. The novel bacterial laccase biosensor was employed for quantitative detection of hydroquinone (HQ) and the electrochemical properties of this laccase biosensor were investigated. The results indicate that the immobilized CotA shows great oxidation activity towards HQ in the presence of oxygen and the biosensor shows linear electrocatalytic activity in the concentration range from 1.6 to 409.6 μM, with a detection limit of 0.3 μM. Further, the CotA modified electrode, when compared to fungal laccase‐modified biosensors, shows better alkaline stability (retaining approximately 80 % and 70 % of response current at pH 8 and 9, respectively) and reusability (retaining ～87 % of response current after 100 days). The development of this new kind of laccase on a biosensor will offer a novel tool for substance detection applications in hostile environments, especially for industrial pollutants.     

One‐pot synthesis of (3‐sulfopropyl methacrylate potassium)‐silica hybrid monolith via thiol‐ene click chemistry for CEC

A novel (3‐sulfopropyl methacrylate potassium)‐silica hybrid monolithic column for CEC has been prepared by a simple one‐pot approach based on efficient thiol‐ene click chemistry. In this process, the polycondensation of hydrolyzed alkoxysilanes and in situ click reaction of vinyl groups on 3‐sulfopropyl methacrylate potassium and thiol groups on the precondensed siloxanes simultaneously occurred in a pretreated capillary. Homogeneous monolithic matrix with large through‐pores tightly bonded to the inner wall of the capillary was shown by optical microscope and SEM. The minimum plate height of this hybrid monolithic column was determined as 3.9 μm for thiourea. Anilines, alkylbenzenes, and phenols were well separated on this hybrid monolithic column by CEC, which indicated typical reversed‐phase and cation‐exchange chromatographic retention mechanisms of the column.     

Enhancement of the Surface Activity for Some Monomeric and Polymeric Thiol Surfactants Using Silver Nanoparticles

In the present work, the self-assembling of some synthesized thiol surfactants namely (6-(3-amino phenoxy) hexane-1-thiol, 8-(3-amino phenoxy) octane-1-thiol, 10-(3-amino phenoxy) decane-1-thiol, 12-(3-amino phenoxy) dodecane-1-thiol, and their polymers on silver nanoparticles was investigated. The self-assembling of these surfactants on silver nanoparticles was characterized using different techniques such as ultraviolet (UV) spectroscopy, powder x-ray diffraction (XRD), electrone diffraction (ED), and transmission electron microscopy (TEM). The effect of the self-assembling of these surfactants on the stabilization of the silver nanoparticles (AgNPs) was studied using TEM images. The growth of the silver nanoparticles was investigated with respect to the increase of alkyl chain in the synthesized thiol surfactants. The effect of silver nanoparticles on the surface, interfacial tension, and the emulsion stability of these surfactants with paraffin oil was studied. The results show that the silver nanoparticles have the ability to effect on the behavior of these surfactants in solution and improve their surface activity.     

A conceptual framework for predicting the toxicity of reactive chemicals: modeling soft electrophilicity

Although the literature is replete with QSAR models developed for many toxic effects caused by reversible chemical interactions, the development of QSARs for the toxic effects of reactive chemicals lacks a consistent approach. While limitations exit, an appropriate starting-point for modeling reactive toxicity is the applicability of the general rules of organic chemical reactions and the association of these reactions to cellular targets of importance in toxicology. The identification of plausible “molecular initiating events” based on covalent reactions with nucleophiles in proteins and DNA provides the unifying concept for a framework for reactive toxicity. This paper outlines the proposed framework for reactive toxicity. Empirical measures of the chemical reactivity of xenobiotics with a model nucleophile (thiol) are used to simulate the relative rates at which a reactive chemical is likely to bind irreversibly to cellular targets. These measures of intrinsic reactivity serve as correlates to a variety of toxic effects; what's more they appear to be more appropriate endpoints for QSAR modeling than the toxicity endpoints themselves.     

巯基化、钠化和酸化膨润土对Cu2+，Pb2+和Zn2+的吸附性能研究

基于改性膨润土可能存在的优异吸附能力,利用傅里叶变换红外光谱仪和场发射扫描电镜研究分析了巯基化、钠化及酸化三种改性膨润土对Cu2+,Pb2+和Zn2+的等温吸附与竞争吸附实验结果。研究结果表明,在单一重金属离子的等温吸附环境下,巯基化膨润土对Cu2+,Pb2+和Zn2+的吸附能力明显优于其他两种材料,且对Pb2+具有一定的吸附选择性,吸附率达到近100%;在竞争吸附环境下,三种改性膨润土对Cu2+,Pb2+和Zn2+的吸附率都有所下降,但巯基化膨润土仍旧能够保持较好的吸附能力,较其他膨润土的吸附率大约高出10%～40%;三种重金属离子的吸附量均表现为Cu2+＞Pb2+＞Zn2+,这与三种重金属离子的竞争能力、化学亲和力等大小有关;膨润土的巯基改性,步骤简单且吸附重金属的效果好,对膨润土改性及其应用具有重要意义。