Coordination polymers. IX

Poly-(butanediol-1,4-adipate) and poly-(diethyleneglycol-succinate) polyesters and their ionized derivatives, containing Mg²⁺ and Zn²⁺ ions with different stoichiometric ratios to the chain-end COOH groups of the polyesters have been investigated by derivatograph.The thermal decompositions of the metal-containing polyesters differ significantly from those of the unionized polyesters. These differences are connected with the chemical repeating unit of the polyesters and the chemical nature of the metal ions, and proportional to the amount of the latter.An explanation is given of the catalytic effect of metal ions on the process of decomposition of the polyesters.

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Zusammenfassung Poly-(butandiol-1,4-adipat) und Poly-(diethylenglycolsuccinat) polyester und ihre «ionisierten» Derivate — mit Mg²⁺ — und Zn²⁺-Ionengehalt in verschiedenen stöchiometrischen Verhältnissen zu den endständigen COOH-Gruppen der Polyester — wurden im Derivatographen untersucht.Die thermische Zersetzung der metallhaltigen Polyester unterscheidet sich wesentlich von nicht-ionisierten Polyestern. Diese Unterschiede sind mit den sich wiederholenden chemischen Einheiten der Polyester und der chemischen Beschaffenheit der Metallionen verbunden, und proportional dem Anteil derselben.Es wird eine Erklärung des katalytischen Effekts der Metallionen auf den Zersetzungsvorgang der Polyester gegeben.

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-1,4 «» , Mg²⁺ Zn²⁺ . , «» . . .

     

Effect of vibrational excitation of HBr on the H+HBr abstraction and exchange reactions

The effect of vibrational excitation of HBr on the H+HBrH₂+Br and H+HBrH+HBr reactions has been investigated on the extended LEPS surface (ELEPS) constructed on the basis of quantum chemically calculated points of PES. Together with this surface the LEPS surface of Sudhakaran and Raff [1] was used for comparison at two relative translational energies. A quasiclassical trajectory method was used to study the abstraction and exchange reaction dynamics. The reactive cross section was calculated as a function of the relative collision energy and the vibrational state of HBr. The following conclusions can be drawn from the results of the study: (i) vibrational excitation v=0 v=2 more than doubles the reaction cross section, (ii) the increase in the collision energy is most effectively channelled into the product translational energy.Dedicated to Professor J. Koutecký on the occasion of his 65th birthday     

Radiolysis of aqueous-ethanolic solution of tryptophan

The effect of ethanol on radiation stability of tryptophan during -irradiation of its aqueous solutions was investigated. In comparison with radiation losses of tryptophan irradiated in pure water, the losses in aqueous-ethanolic solutions are considerably higher and they increase with increasing ethanol concentration. Basic radiation products of tryptophan formed on irradiation of its aqueous-ethanolic solutions in consequence of the reaction of tryptophan with acetaldehyde as the main product of radiolysis of ethanol were followed by paper electrophoresis.     

Application of Et3NHCl-AlCl3 Ionic Liquid as an Initiator in Cationic Copolymerization of 1, 3-Pentadiene with Styrene

Room temperature ionic liquids (RTILs) as advanced, technological solvents can be designed to fit a particular application. They used as green “media and/or catalysts” for chemical synthesis have been extensively reviewed recently. RTILs1 not only show …     

Tritium volume activity in natural waters of the NPP Temelín region

With the use of the tritium monitoring network the samples of river water, air humidity and precipitation are collected and analysed for HTO in the vicinity of Temelín nuclear power plant.     

Differential pulse polarographic determination of salicylaldehyde as its Girard-P derivative

A method for the determination of salicylaldehyde (2 × 10^–6–10^–4 M) by differential-pulse polarography, based on the in situ formation of its Girard-P derivative in aqueous solution at pH 2.5, is proposed. The relative standard deviation was 1.5% (ten determinations of 4 × 10^–5 M level). The applicability of this method was checked in synthetic samples containing salicyl alcohol,o-aminophenol, 2-methylphenol, salicylic acid and 4-aminobenzoic acid.     

Novel method for the preparation of anionic surfactant-selective electrodes

A simple one-step synthesis is described for the functionalization of poly(vinyl chloride) used for the preparation of anionic surfactant-selective membrane electrodes. The method is based on the nucleophilic substitution of a fraction of the chlorine atoms bound to the poly(vinyl chloride) backbone by trimethylamine. The prepared slightly charged polymer gave rise to high-quality surfactant-selective electrode membranes, which had a Nernstian response, short response time, and appropriate stability.     

Stability study of simvastatin under hydrolytic conditions assessed by liquid chromatography

In this work, a liquid chromatography stability-indicating method was developed and applied to study the hydrolytic behavior of simvastatin in different pH values and temperatures. The selected chromatographic conditions were a C18 column; acetonitrile-28 mM phosphate buffer solution, pH 4 (65 + 35) as the mobile phase; 251 degrees C column temperature; and flow rate 1 mL/min. The developed method exhibited an adequate repeatability and reproducibility (coefficient of variation 0.54 and 0.74%, respectively) and a recovery higher than 98%. Furthermore, the detection and quantification limits were 9.1 x 10(-7) and 2.8 x 10(-6) M, respectively. The degradation of simvastatin fitted to pseudo-first order kinetics. The degradation was pH dependent, being much higher at alkaline pH than at acid pH. Activation energy, kinetic rate constants (k) at different temperatures, the half life (t1/2) and the time for 10% degradation to occur (t90) values are also reported.     

Human topoisomerase I poisoning: docking protoberberines into a structure-based binding site model

Summary Using the X-ray crystal structure of the human topoisomerase I (top1) – DNA cleavable complex and the Sybyl software package, we have developed a general model for the ternary cleavable complex formed with four protoberberine alkaloids differing in the substitution on the terminal phenyl rings and covering a broad range of the top1-poisoning activities. This model has the drug intercalated with its planar chromophore between the −1 and +1 base pairs flanking the cleavage site, with the nonplanar portion pointing into the minor groove. The ternary complexes were geometry-optimized and relative interaction energies, computed by using the Tripos force field, were found to rank in correct order the biological potency of the compounds; in addition, the model is also consistent with the top1-poisoning inactivity of berberine, a major prototype of the protoberberine alkaloids. The model might serve as a rational basis for elaboration of the most active compound as a lead structure, in order to develop more potent top1 poisons as next generation anti-cancer drugs.     

表面修饰二氧化锡纳米微晶的制备与表征

制备了硅烷偶联剂KH-570表面修饰的SnO2纳米微晶，通过FT-IR、XPS、TEM和TG-DTA对其结构和表面特性进行表征和研究. FT-IR和XPS分析结果确证了KH-570与SnO2表面是以化学键合或物理吸附方式相结合,粒子表面存在酯基等有机官能团的红外吸收特征；观测到KH-570中Si原子的Si2s和Si2p谱线. TEM分析表明，表面修饰反应增强了SnO2纳米微晶的疏水性和分散性.由XPS和TG的实测数据探讨了纳米粒子具有较低包覆量的可能原因.