Bestimmung von Epoxyendgruppen in modifizierten chromatographischen Sorbentien und Gelen

Zusammenfassung Zur Bestimmung der auf Silicagel oder Ethylenglykolmethacrylat-Gel Spheron chemisch gebundenen Epoxygruppen wurden die Methoden der Addition von Chlorwasserstoff aus einer Lösung von Pyridiniumchlorid in Pyridin, einer Lösung von Chlorwasserstoff in Dioxan oder Methylcellosolve, sowie die Addition von Thiosulfat und die direkte Titration mit Perchlorsäure in nichtwäßrigem Milieu in Anwesenheit von Tetraethylammoniumbromid untersucht und angewendet. Die besten Resultate mit einer guten Reproduzierbarkeit liefert die direkte Titration der in einer Tetraethylammoniumbromidlösung in Eisessig suspendierten Probe mit einer Perchlorsäurelösung in Eisessig. Die relative Standardabweichung in einem Bereich von 0,6–0,8 mmol Epoxygruppe/g ist nicht höher als 1%.

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Determination of epoxy end-groups in modified chromatographic sorbents and gels

Summary The addition of hydrogen chloride from solutions of pyridinium chloride in pyridine, or from solutions of hydrogen chloride in dioxan or in methylcellosolve, as well as the addition of thiosulphate and the direct non-aqueous titration with perchloric acid in the presence of tetraethylammonium bromide were studied and applied for the determination of bound epoxy groups in epoxidized silicagels and the ethyleneglycol methacrylate gels Spheron. Best results with high reproducibility were obtained by direct titration with perchloric acid of a sample suspended in a solution of tetraethylammonium bromide in acetic acid. The relative standard deviation in the range of 0.6–0.8 mmol epoxy group/g does not exceed 1%.

     

Biological efficacy of antisense oligonucleotides complementary to overlapping regions of the mRNA target

Phosphorothioate oligonucleotides complementary to target mRNA are stable in biological milieu and are capable of decreasing levels of this mRNA and the protein encoded by this mRNA (antisense knockdown). The results of our study are compared with the data published in the literature on the efficacy of three antisense 18—21-mer oligonucleotides, which are targeted to the start codon or nearby sequences of _2A-adrenoceptor mRNA, on receptor expression, and functions regulated by these receptors. The highest biological efficacy was shown by the oligonucleotide, which is complementary to the mRNA region and contains the largest number of unpaired bases in the theoretically calculated conformation corresponding to the free energy minimum. Targeting of both ends of the antisense on unpaired bases of the target also leads to the enhancement of its biological efficacy.     

基于硫醇耦合蛋白绑定方法的表面等离子共振谱葡萄糖检测技术研究

使用表面等离子共振谱(surface plasmon resonance,SPR)检测葡萄糖浓度,引入D-半乳糖/D-葡萄糖结合蛋白(D-galactose/D-glucose binding protein,GGBP),该蛋白能够选择性吸附葡萄糖分子,实现特异性、高分辨率地检测葡萄糖分子的浓度。研究了在SPR传感器表面利用硫醇耦合绑定蛋白的方法,成功在SPR传感器表面绑定了GGBP蛋白并对不同浓度的葡萄糖进行了测量实验。实验结果显示,当葡萄糖浓度为0.1~10mg·dL-1时,采用硫醇耦合方法修饰蛋白的传感器具有良好的线性,同时也具有很好的重复性和稳定性,在SPR传感器表面绑定GGBP蛋白满足了组织液中低浓度葡萄糖检测的需求。     

Needle‐trap device for the sampling and determination of chlorinated volatile compounds

A needle‐trap device, with immobilized sorbent inside the syringe, coupled with GC–MS was applied for air sampling and determination of chlorinated volatile organic compounds such as dichloromethane, trichloromethane, and tetrachloromethane. The application of a needle trap packed with combination of three sorbents including Tenax TA, Carbopack X, and Carboxen 1000 resulted in detection limits of few pg for chlorinated volatile compounds and recoveries of 99.2–102.8%. The extraction and desorption parameters were optimized within the study. As a result, the precision determined as RSD was equal to 5.05 and 3.03 and 6.52% for dichloromethane, trichloromethane, and tetrachloromethane, respectively. The storage time for chlorinated compounds up to 48 h and reusability of the needle‐trap device were verified. The obtained results have proved the ability of needle traps to compete with other solventless sampling and sample preparation extraction techniques.     

Protic ionic liquids as recyclable solvents for the acid catalysed synthesis of diphenylmethyl thioethers

The acid catalysed formation of diphenylmethyl (DPM) thioethers was successfully achieved using the protic ionic liquid (pIL) triethylamine:methanesulfonic acid (TeaMs) as the reaction solvent under microwave irradiation. A slight excess of methanesulfonic acid (10% v/v) was required to facilitate the reaction, which was applied to a variety of thiols. Aliphatic, aromatic and heterocyclic aromatic thiols were converted to their corresponding DPM thioethers in high yields (63–99%), in short reaction times (5–20 min) and using mild temperatures (80–100 °C). Finally, the pIL (TeaMS) was recycled five times without loss of yield.     

A Convenient Preparation of Bis(4‐methoxyphenyl)methanethiol and Its Application in the Synthesis of Biotin Thioacid

We have established a facile protocol for the preparation of bis(4‐methoxyphenyl)methanethiol ( 4 ). Thiol 4 was used to prepare biotin thioester 7 which was later subjected to acidolysis to afford biotin thioacid ( 1b ) in high yield. Compound 1b represents a new biotinylating reagent worth exploring and its spectral data was reported for the first time.     

Esr and endor studies of partially deuterated and chlorinated phenalenyls : New synthetic pathways

A variety of partially chlorinated and deuterated phenalenyl radicals has been produced by the reaction of the respective acenaphthylenes with chloroform as a carbenoid precursor and via thermal decomposition of some mercury carboxylates. By ESR and ENDOR-in-solution measurements the effectiveness of the different reaction paths to specifically substituted compounds has been investigated.     

Partial oxidation and oxidative polymerization of metallothionein

One mechanism for regulation of metal binding to metallothionein (MT) involves the non-enzymatic or enzymatic oxidation of its thiols to disulfides. Formation and speciation of oxidized MT have not been investigated in detail despite the biological significance of this redox biochemistry. While metal ion-bound thiols in MT are rather resistant towards oxidation, free thiols are readily oxidized. MT can be partially oxidized to a state in which some of its thiols remain reduced and bound to metal ions. Analysis of the oxidation products with SDS-PAGE and a thiol-specific labeling technique, employing eosin-5-iodoacetamide, demonstrates higher-order aggregates of MT with intermolecular disulfide linkages. The polymerization follows either non-enzymatic or enzymatic oxidation, indicating that it is a general property of oxidized MT. Supramolecular assemblies of MT add new perspectives to the complex redox and metal equilibria of this protein.     

Electrochemical and Electrocatalytic Properties of Imidazole Analogues of the Redox Cofactor Pyrroloquinoline Quinone

The electrochemical and electrocatalytic properties of two synthetic imidazole analogues of the redox cofactor pyrroloquinoline quinone (PQQ) were evaluated. Cyclic voltammetry measurements as a function of pH indicated that both 4,5‐dihydro‐4,5‐dioxo‐1H‐imidazolo[5,4‐f]quinoline‐7,9‐dicarboxylic acid ( 1 ) and 4,5‐dihydro‐4,5‐dioxo‐2‐methyl‐1H‐imidazolo[5,4‐f]quinoline‐7,9‐dicarboxylic acid ( 2 ) undergo a reversible reduction of the o‐quinone moiety below pH 8 with potentials slightly more positive than those observed for PQQ. Upon incorporation into a polypyrrole membrane on the tip of a glassy carbon electrode, 1 and 2 exhibited electrocatalytic properties sufficient for the indirect amperometric detection of cysteine. The response for cysteine was linear up to 1 mM over a wide pH range. Detection limits (S/N=3) were in the μM range and dependent on the solution pH. Interference from redox active species such as dopamine and uric acid were minimized by the pH‐dependent redox potentials of 1 and 2 and thus the ability to tune the detection potential.