Ditopic Aza-Scorpiand Ligands Interact Selectively with ds-RNA and Modulate the Interaction upon Formation of Zn2+ Complexes

Nucleic acids are essential biomolecules in living systems and represent one of the main targets of chemists, biophysics, biologists, and nanotechnologists. New small molecules are continuously developed to target the duplex (ds) structure of DNA and, most recently, RNA to be used as therapeutics and/or biological tools. Stimuli-triggered systems can promote and hamper the interaction to biomolecules through external stimuli such as light and metal coordination. In this work, we report on the interaction with ds-DNA and ds-RNA of two aza-macrocycles able to coordinate Zn²⁺ metal ions and form binuclear complexes. The interaction of the aza-macrocycles and the Zn²⁺ metal complexes with duplex DNA and RNA was studied using UV thermal and fluorescence indicator displacement assays in combination with theoretical studies. Both ligands show a high affinity for ds-DNA/RNA and selectivity for ds-RNA. The ability to interact with these duplexes is blocked upon Zn²⁺ coordination, which was confirmed by the low variation in the melting temperature and poor displacement of the fluorescent dye from the ds-DNA/RNA. Cell viability assays show a decrease in the cytotoxicity of the metal complexes in comparison with the free ligands, which can be associated with the observed binding to the nucleic acids.     

Tracing of peroxy radicals in hexane cool flames

Stabilized hexane-air cool flames in a separately heated two-section reactor have been studied at T=480–770 K and P=30–63 kPa. ESR spectra of peroxy radicals were analyzed by the radical freezing technique and sonde sampling. Under these conditions high radical concentrations (>10¹⁴ cm^–3) are observed. With increasing pressure and temperature, the fraction of HO₂ radicals in the overall amount of radicals grows.

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480–770 , 30–63 . . , (>10¹⁴cm^–3). , HO₂ .

     

Synthesis and thermal decomposition of acid alkali metal hexafluoroaluminates

Acid alkali hexafluoroaluminates of K and Rb were prepared by precipitation of alkali fluoride containing H₃AlF₆ solutions with ethanol. Compounds were characterized by X-ray diffraction, IR spectroscopy,¹H-NMR and chemical analysis. The constitution is M^I(H₃O)₂AlF₆. Lattice parameters were determined.Dehydration and thermal decomposition were investigated by thermal analysis (TG, DTG, DTA) on a derivatograph-Q and by high temperature X-ray diffraction. Thermal decomposition is accompanied by liberation of H₂O and HF and a condensation of [AlF₆]^3– octahedra forming layer structures. Stable intermediate products are M^IAlF₄·0.5H₂O and M^IAlF₄. At higher temperatures hydrolysis occurs.

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Zusammenfassung Es wurden saure Kalium- und Rubidiumhexafluoroaluminate durch Fällung aus Alkalifluorid enthaltenden H₃AlF₆-Lösungen mit Ethanol dargestellt. Die erhaltenen Verbindungen wurden chemisch, röntgenographisch, IR- sowie¹H-NMR-spektroskopisch charakterisiert. Die Konstitution der Verbindungen ist M^I(H₃O)₂AlF₆. Die Gitterkonstanten wurden aus Röntgendiffraktionsdaten bestimmt. Entwässerung und thermische Zersetzung wurden mittels Heizguiniertechnik und Thermoanalyse (TG, DTG, DTA) an einem Derivatograph-Q untersucht. Bei der thermischen Zersetzung erfolgt eine HF- und H₂O-Abgabe sowie eine Kondensation von AlF ₆ ^3– -Oktaedern unter Ausbildung von Schichtstrukturen. Als stabile Zwischenprodukte wurden M^IAlF₄·0.5H₂O und M^IAlF₄ nachgewiesen. Bei höheren Temperaturen werden Hydrolysereaktionen beobachtet.

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, H₃AlF₆, . M¹(H₃O)₂AlF₆ , - - . . (, , ) Q- , . [AlF₆]^3– . M¹AlF₄·0.5H₂O M¹AlF₄. .

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Presented at the Microsymposium on Halogen Chemistry held in Budapest, 1987.     

Sonochemical synthesis and electrochemical characterization of α-nickel hydroxide: precursor effects

Sonochemical degradation of urea was employed to synthesize alpha-nickel hydroxide from different nickel salts. Utilization of ultrasound yielded products with properties significantly different than the products obtained by thermal degradation of urea. The effect of intercalating chloride, nitrate, acetate, and sulfate anions on morphology and electrochemical performance was studied. The sulfate-intercalated sample had the smallest interlayer spacing when obtained by the sonochemical method, contradicting all the previous thermal synthesis results. The specific capacitance trend also differed from the literature values, and the value for the sulfate-intercalated sample was larger than that of acetate- and nitrate-intercalated samples. Ultrasonic synthesis increased the specific capacitance of the sulfate-intercalated sample significantly. This sample was also the most reversible and had the highest charge efficiency.     

Large N‐Heteroacenes: New Tricks for Very Old Dogs?

Azaacenes have been known for a very long time, either as N,N′‐dihydro compounds or in their oxidized form as 4 n+2π systems, but only recently have processable and charcterizable derivatives been sought. In the last three years synthetic routes to large N‐heteroacenes have been developed. In particular, the Pd‐catalyzed coupling of aromatic diamines with activated aromatic dihalogenides has enabled simple access to numerous new azaacenes. Since 2010, azapentacene and stabile oligoazahexacene have been synthesized, as well as a symmetrical tetraazapentacene, which acts as an excellent electron‐transport material for thin‐film transistors.     

New transformations of vinyl acetate under the influence of the complex Rh(PPh3)3Cl

The strictly regioselective hydrocarboxylation of vinyl acetate to ethylidene diacetate by acetic acid formed in situ from vinyl acetate was realized for the first time with Rh(PPh₃)₃Cl as catalyst. The transformation of vinyl acetate into benzene, acetophenone, and acetylene was also realized.Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, 420083 Ufa. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1406–1408, June, 1992.     

Influence of defoliating agents on the level of some secondary metabolites in cotton-plant leaves

The change in the composition of the secondary metabolites (SMs) of cotton-plant leaves under the influence of two modifications of defoliating agents in the period of leaf fall has been studied. It has been shown that, in contrast to the dynamics of the SMs in genetic deciduous lines, up to the period of leaf-fall the amount of free sterols in the petioles decreases, while in the leaf blades it remains unchanged. In experiments with cotyledons, the opposite effect was observed. In all cases, the amount of polyprenols decreased substantially.Institute of Chemistry of Plant Substances, Uzbekistan Republic Academy of Sciences, Tashkent. Institute of Experimental Plant Biology, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 67–71, January–February, 1992.