Secondary structure of DNA is recognized by slightly cross-linked cationic hydrogel

Interaction of salmon sperm DNA (300-500 bp) and ultrahigh molecular mass DNA (166 kbp) from bacteriophage T4dC with linear poly(N-diallyl-N-dimethylammonium chloride) (PDADMAC) and slightly cross-linked (#) PDADMAC (#PDADMAC) hydrogel in water has been studied by means of UV-spectroscopy, ultracentrifugation, atomic force, and fluorescence microscopy (FM). It is found that the linear polycation induced compaction of either native (double-stranded) or denatured (single-stranded) DNA by forming PDADMAC-DNA interpolyelectrolyte complexes (IPEC)s. At the same time, #PDADMAC hydrogel is able to distinguish between native and denatured DNA. Native DNA is adsorbed and captured in the hydrogel surface layer, while denatured DNA diffuses to the hydrogel interior until the whole hydrogel sample is transformed into the cross-linked IPEC. Both native and denatured DNA can be completely released from the hydrogel in appropriate conditions with no degradation by adding a low molecular salt. The data observed using conventional physicochemical methods with respect to DNA of a moderate molecular mass remarkably correlate with the pictures directly observed for ultrahigh molecular mass DNA in dynamics by using FM.     

Conducive integral domains as pullbacks

This article presents a characterization of conducive (integral) domains as the pullbacks in certain types of Cartesian squares in the category of commutative rings. Such squares behave well with respect to (semi)normalization, thus permitting us to recover the recent characterization by Dobbs-Fedder of seminormal conducive domains. The conducive domains satisfying various finiteness conditions (Noetherian, Archimedean, accp) are characterized by identifying suitable restrictions on the data in the corresponding Cartesian squares. Various necessary or sufficient conditions are given for Mori conducive domains. Consequently, one has examples of several (accp non-Mori; Mori non-Noetherian) conducive domains.Work performed under the auspices of GNSAGA of Consiglio Nazionale delle Ricerche and Dipartimento di Matematica, Università di Roma La SapienzaSupported in part by grants from University of Tennessee Faculty Development Program and the Università di Roma La Sapienza     

Palladium-assisted multicomponent synthesis of 2-aryl-4-aminoquinolines and 2-aryl-4-amino[1,8]naphthyridines

A palladium-mediated multicomponent domino reaction leading to 2-aryl-4-amino-quinolines and 2-aryl-4-amino[1,8]naphthyridines is reported. The scope of the reaction was examined using carbon monoxide, two 2-ethynyl-arylamines, four aryl iodides, and 10 primary amines as substrates. The selection of the appropriate catalytic system was achieved testing several palladium/phosphine systems and overrides previously reported drawbacks associated with the use of primary amines in related reactions. Moreover several features concerning the role of both palladium [(0) and (II)] and phosphines are reported.     

Reaction of enaminonitriles with isocyanates. Synthesis of new 2-oxo- and 6-oxopyrimidines

The reaction of enaminonitriles 1 with aryl or benzyl isocyanates afforded C- 3–5 or N-adducts 6–8 or a mixture of both depending on the substitution pattern of the considered enaminonitrile. The one-step synthesis of 6-oxopyrimidines 9–11 and 2-oxopyrimidines 12–14 by cyclization of compounds 3–5 and 6–8 respectively is also described.     

Characteristic features of polytypism in compounds with the La18W10O57‐type structure

Crystals with the La₁₈W₁₀O₅₇‐type structure (6H and 5H polytypes) were obtained by a self‐flux method from high‐temperature solutions. Some of the crystal samples were studied by single‐crystal X‐ray structure analysis. The diffraction patterns indicated that two phases co‐exist in each sample. The hexagonal lattices have a common period of a ≈ 9.0 Å and are non‐equal in length but have equally oriented superstructure periods 6c (phase I) and 5c (phase II), c ≈ 5.4 Å. The structures of phases I and II were solved in the symmetry groups P2c and P321, respectively, based on the X‐ray data for crystals I and II, with predominant content of the first and second phase. The motif of isolated WO₆ prisms with W atoms on the cell edges is common to both phases. WO₆ octahedra, both isolated and joined by faces, are distributed along the c axis within the unit cells. Phase I contains extra layers of isolated WO₆ octahedra compared to phase II. Tungsten sites in joined octahedra are disordered and partially occupied. Disordering is more expressed in phase II, which in return contains rather more W and O per atom of La. The refined chemical compositions are La₁₈W₁₀O₅₇ for I and La₁₅W_8.5O₄₈ for II.     

1,2,4-Triazolo[4,3-c]pyrimidines from 4-acylhydrazinopyrimidines

The reaction of N¹-acetylacetamidrazones 1 with N-[bis(methylthio)methylene]cyanamide (2) at room temperature in the presence of potassium carbonate in dimethyl sulfoxide affords good yields of ethyl 4-acylhydrazino-2-amino-6-methylthio-5-pyrimidine carboxylate 3 . By briefly refluxing compounds 3 in dimethyl sulfoxide, 1,2,4-triazolo[4,3-c]pyrimidine derivatives 4 were obtained. When equimolecular amounts of N¹-acylacetamidrazones and compounds 2 were refluxed in dimethyl sulfoxide/toluene, compounds 4 were obtained directly.     

Synthesis of triflouromethylated pyridinecarbonitriles

Enaminonitriles 1 react in mild conditions with β-trifluoroacetylvinyl ethers 2 to give the pyridine derivatives 4 . The reaction involves the formation of the intermediate 3 , that can be isolated when enol ether 2a is used.     

Microstructural Evolution of Titanium Carbonitride Based Materials During Oxidation

 Ti(C, N) based materials represent a new class of hard and wear resistant structural materials. Nowadays, the main field of applications is focused on metal cutting and finishing operations. For these kinds of applications usually the mentioned materials work in oxidizing environments at high temperatures. The thermophysical stability under these conditions represents therefore a key factor that influences the material’s performance, and consequently the tool life of the component in service. The present study aimed to investigate the oxidation behaviour of two different Ti(C, N)-WC based materials, the first containing 0.9 wt% of Co and the second 6.2 wt% of Ni and 2.9 wt% of Co. Cycled oxidation tests (20 hours each) were conducted with a muffle furnace in laboratory static air at 1000 °C up to 100 hours. During the initial transitory stage the competition between the mass gain due to the formation of solid TiO₂ (rutile) and the mass loss due to released volatile W oxides controlled the mass change; thereafter the oxidation process obeyed a linear law. Great microstructural modifications occurred on the (sub)surfaces of the oxidized samples: multiphase TiO₂ based scales grew upon the external surfaces of the oxidized specimens. Kinetics and oxidation mechanisms were proposed and discussed.     

Confined space design by nanoparticle self-assembly

Nanoparticle (NP) self-assembly has led to the fabrication of an array of functional nanoscale systems, having diverse architectures and functionalities. In this perspective, we discuss the design and application of NP suprastructures (SPs) characterized by nanoconfined compartments in their self-assembled framework, providing an overview about SP synthetic strategies reported to date and the role of their confined nanocavities in applications in several high-end fields. We also set to give our contribution towards the formation of more advanced nanocompartmentalized SPs able to work in dynamic manners, discussing the opportunities of further advances in NP self-assembly and SP research.

This perspective gives an outlook on the design of interparticle confined nanocavities in self-assembled NP systems and their functional relevance.     

Analysis of yttrium aluminium borate crystals by solution-based methods: inductively coupled plasma atomic emission spectrometry and flame atomic absorption spectrometry

Comparative analysis of yttrium aluminium borate (YAB) /YAl₃(BO₃)₄/ optical single crystals was performed by flame atomic absorption spectrometry (FAAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) methods for Cr, Dy, Er, Yb, Y, Al, B and Mo. The dopant element, Ce, could be determined only by the ICP-AES method at the required concentration level. The powdered crystal samples were fused with lithium metaborate (LiBO₂) at 950 °C in a platinum crucible and then dissolved in 6 mol l⁻¹ HCl. Although this fusion-dissolution procedure proved to be simple and effective, the quantitative determination of B—as the matrix element in samples—was handicapped by the B content of the fusing reagent. For the FAAS method, with the use of nitrous oxide–acetylene flame, cesium chloride ionization buffer and lanthanum chloride releasing agent [0.1+0.2% (m/v), respectively] were applied. These agents enhanced the atomic absorption signals of Cr, Dy, Er, Mo, Yb and Y, whereas no change of sensitivity was resulted in for Al and B. A fairly good agreement was found between the results of the two alternative spectrochemical methods. The predicted stoichiometry of the crystals was also well approximated indicating the reliability of the crystal growth technology applied.