Rolling circle amplification-templated DNA nanotubes show increased stability and cell penetration ability

DNA nanotubes hold promise as scaffolds for protein organization, as templates of nanowires and photonic systems, and as drug delivery vehicles. We present a new DNA-economic strategy for the construction of DNA nanotubes with a backbone produced by rolling circle amplification (RCA), which results in increased stability and templated length. These nanotubes are more resistant to nuclease degradation, capable of entering human cervical cancer (HeLa) cells with significantly increased uptake over double-stranded DNA, and are amenable to encapsulation and release behavior. As such, they represent a potentially unique platform for the development of cell probes, drug delivery, and imaging tools.     

Effect of Organoclay Mixture on the Rheological Properties of ABS-Clay Nanocomposites

Summary: In this work, poly(acrylonitrile-butadiene-styrene) (ABS) and different organically modified montmorillonite clay nanocomposites were prepared by melt intercalation in a co-rotating twin screw extruder. The influence of the screw torque during processing and of the mixture of the modified organoclays in the intercalation/exfoliation of the clay in the polymeric matrix was evaluated through low angle X-ray diffraction range and capillary and parallel plate-plate rheometry.     

Facile synthesis of Koser's reagent and derivatives from iodine or aryl iodides

The first one-pot synthesis of neutral and electron-rich [hydroxy(tosyloxy)iodo]arenes (HTIBs) from iodine and arenes is presented, thereby avoiding the need for expensive iodine(III) precursors. A large set of HTIBs, including a polyfluorinated analogue, can be obtained from the corresponding aryl iodide under the same conditions. The reaction proceeds under mild conditions, without excess reagents, and is fast and high-yielding. Together, the two presented routes give access to a wide range of HTIBs, which are useful reagents in a variety of synthetic transformations.     

Characterisation of five coins from the archaeological heritage of Portugal

This paper reports a study carried out on three Roman and two Portuguese coins found in the archaeological site of São Pedro, in Fronteira (Alentejo, Portugal). The three Roman coins have been identified as a Follis, an AE 2 and an AE 3 (bronze alloys), while the Portuguese coins have been identified as a Ceitil (copper) and the “6 vinténs” (Ag–Cu alloy). Scanning electron microscopy (SEM) coupled to energy dispersive spectroscopy (EDS) has allowed the semi-quantitative determination of the elemental composition of both the corrosion products and the alloy used in the manufacture of the coins. The crystalline corrosion products constituents of the patinas were identified by X-ray powder diffraction spectroscopy (XRD). The more deteriorated coin, the AE 3, was submitted to electrochemical studies in Na₂SO₄ aqueous solution and the corresponding data analysed. After 3 weeks, the E _OCP was still quite stable, ranging between ?0.050 and ?0.070 V vs. SCE; the corrosion resistance, R _p, was of the order of 5 to 3?×?10³ Ω. Chemical treatment of the sample by 1-h immersion in 0.1 M NaOH produced a more active surface, with R _p showing a decrease of a factor of about ten. On the other hand, it was concluded from voltammetric data that polarisations of E _a?≥?0.050 V vs. SCE led to copper oxidation, with no reduction of the other corrosion products.     

3D-RISM-KH molecular theory of solvation and density functional theory investigation of the role of water in the aggregation of model asphaltenes

We applied a multiscale modeling approach that involves the statistical-mechanical three-dimensional reference interaction site model with the Kovalenko-Hirata closure approximation (3D-RISM-KH molecular theory of solvation) as well as density functional theory (DFT) of electronic structure to study the role of water in aggregation of the asphaltene model compound 4,4'-bis(2-pyren-1-yl-ethyl)-2,2'-bipyridine (PBP) [X. Tan, H. Fenniri and M. R. Gray, Energy Fuels, 2008, 22, 715]. The solvation free energy and potential of mean force predicted by 3D-RISM-KH reveal favorable pathways for disaggregation of PBP dimers in pure versus water-saturated chloroform solvent. The water density distribution functions elucidate hydrogen bonding preferences and water bridge formation between PBP monomers. The ΔG(298) values of -5 to -7 kcal mol(-1) for transfer of water molecules in chloroform to a state interacting with PBP molecules are in agreement with experimental results. Geometry optimization and thermochemistry analysis of PBP dimers with and without water bridges using WB97Xd/6-31G(d,p) predict that both PBP dimerization and dimer stabilization by water bridges are spontaneous (ΔG(298) < 0). The (1)H NMR chemical shifts of PBP monomers and dimers predicted using the gauge-independent atomic orbital method and polarizable continuum model for solvation in chloroform are in an excellent agreement with the experimental results for dilute and concentrated PBP solutions in chloroform, respectively [X. Tan, H. Fenniri and M. R. Gray, Energy Fuels, 2009, 23, 3687]. The DFT calculations of PBP dimers with explicit water show that bridges containing 1-3 water molecules lead to stabilization of PBP dimers. Additional water molecules form hydrogen bonds with these bridges and de-shield the PBP protons, negating the effect of water on the (1)H(C3) NMR chemical shift of PBP, in agreement with experiment. The ΔG(298) results show that hydrogen bonding to water and water-promoted polynuclear assembly bridging is as important as π-π interactions for asphaltene aggregation.     

On Birkhoff Theorems for Lagrangian invariant tori with closed orbits

We show that a C¹ torus that is homologous to the zero section, invariant by the geodesic flow of a symmetric Finsler metric in T², and possesses closed orbits is a graph of the canonical projection. This result, together with the result obtained by Bialy in 1989 for continuous invariant tori without closed orbits of symmetric Finsler metrics in T², shows that the second Birkhoff Theorem holds for C¹ Lagrangian invariant tori of symmetric Finsler metrics in the two torus. We also study the first Birkhoff Theorem for continuous invariant tori of Finsler metrics in T² and give some sufficient conditions for a continuous minimizing torus with closed orbits to be a graph of the canonical projection. Partially supported by CNPq, FAPERJ, TWAS     

Purification,Partial Characterization,and CNBr-Sepharose Immobilization of a Vasorelaxant Glucose/Mannose Lectin from Canavalia virosa Seeds

A novel mannose/glucose-binding lectin from Canavalia virosa (designated as ConV) has been purified from seeds of C. virosa by affinity chromatography on a mannose-Sepharose 4B column. ConV strongly agglutinates rabbit erythrocytes and was inhibited by monosaccharides (D-mannose, D-glucose, and α-methyl-D-mannoside) and glycoproteins (ovalbumin and fetuin). SDS-PAGE revealed three bands corresponding to three subunits (α, β, and γ) confirmed by ESI mass spectrometry with exact mass of 25,480?±?2 Da, 12,864?±?1 Da, and 12,633?±?1 Da, respectively. The purified lectin was more stable in pH ranging from 7.0 to 9.0, supported up to 80?ºC without any loss in activity and unaffected by EDTA. ConV showed no toxicity against Artemia sp. nauplii and relaxed endothelized rat aorta, with the participation of the lectin domain. In our tests, the lectin immobilized on CNBr-Sepharose was capable of binding 0.8 mg of ovalbumin per chromatography, allowing the use of ConV as a tool for capture and purification of glycoproteins.     

Green chromatographic fingerprinting: An environmentally friendly approach for the development of separation methods for fingerprinting complex matrices

A chromatographic fingerprint is a comprehensive method that reveals the distinctive pattern of peaks across the chromatogram for a given sample. It is considered an effective strategy to assess the identity and quality of herbal materials, as well as for the control of the quality of their derived products. HPLC is the most employed technique for these purposes and it is used routinely for quality control in industry. Hence, its impact on the environment should not be neglected. This work provides a rational and generic procedure to qualitatively fingerprint complex matrices. Resource‐ and time‐saving experimental designs were selected; an alternative safer organic solvent was tested and a time‐saving and innovative response entitled the green chromatographic fingerprinting response was developed and employed. This procedure was applied in the development of chromatographic fingerprints for extracts of Bauhinia forficata and Casearia sylvestris. Moreover, the response proposed here can be combined with a complementary metric available in the literature to compare methods using different solvents. According to this, the chromatographic fingerprints developed here using ethanol as the organic solvent provided a performance better than that of reference methods in which more harmful acetonitrile or methanol were employed.