Reaction of Amines with 8‐MethylthioBODIPY: Dramatic Optical and Laser Response to Amine Substitution

A thorough study of the photophysical and laser properties of 8‐aminoboron dipyrromethene dyes was undertaken to determine the role of amine substitution and spatial disposition on the properties of the dyes. It was found that the fluorescent and laser response varied significantly. Although primary amines give rise to highly fluorescent products at the blue edge of the visible region, secondary amines yield nonfluorescent analogues in polar media. The crystal structures of two analogues are reported and described. Steric hindrance and the higher electron‐releasing ability of the amine favor the formation of a quenching intramolecular charge‐transfer state. Accordingly, boron dipyrromethene derivatives with primary amines exhibited laser emission with efficiencies of up to 44 %. Besides, the more efficient derivative was also the most photostable, leading to a significant improvement in the lasing performance with regard to previously reported 8‐aminoboron dipyrromethene derivatives. An increase in the solvent polarity, and mainly the presence of tertiary cyclic amines, led to a dramatic decrease or even the loss of the laser action.     

Fluorescent Flippers: Small-Molecule Probes to Image Membrane Tension in Living Systems

Flipper probes have been introduced as small molecule fluorophores to image physical forces, that is, membrane tension in living systems. Their emergence over one decade is described, from evolution in design and synthesis to spectroscopic properties. Responsiveness to physical compression in equilibrium at the ground state is identified as the ideal origin of mechanosensitivity to image membrane tension in living cells. A rich collection of flippers is described to deliver and release in any subcellular membrane of interest in a leaflet-specific manner. Chalcogen-bonding cascade switching and dynamic covalent flippers are developed for super-resolution imaging and dual-sensing of membrane compression and hydration. Availability and broad use in the community validate flipper probes as a fine example of the power of translational supramolecular chemistry, moving from fundamental principles to success on the market.     

Nitrogen effects in multi-matrix calibrations by radiofrequency glow discharge – optical emission spectrometry

A study about the effect of nitrogen in the calibration curves of a series of analytical emission lines has been carried out in this work. Fifteen reference materials with different matrices (Fe, Al, Zn, Cu and Ni) were used (three of these reference materials contain nitrogen in their composition) and plots of intensity versus the product “sputtering rate times element concentration” were constructed for emission lines of the analytes considered in this work (Al, Fe, Cu, Cr, C, Mo, Zn, Si, Ti and Ni). Two different fits were performed in each plot, first considering only the points corresponding to samples without nitrogen in their composition and secondly including all the points. The results show almost negligible differences in the emission yields calculated. On the other hand, a mixture of Ar containing 0.5% N₂ was employed to check if the nitrogen effect was present at higher concentrations than those expected in analysis when samples with high nitrogen concentrations are used. Differences between the slopes of the calibration curves with the Ar/N₂ and pure Ar discharges were obtained (up to 30%). A study of the molecular bands recorded in the spectra when nitrogen is present in the discharge and determination of the resulting interferences on the analytes have been performed. Figure Glow discharge powered with radiofrequency energy     

A new linker for solid-phase synthesis of heparan sulfate precursors by sequential assembly of monosaccharide building blocks

A novel ester type linker which upon cleavage releases the glycans as carbamate protected aminoglycosides was successfully employed in the sequential assembly of L-idose and azido glucose monosaccharide building blocks to heparan sulfate precursors.     

Fracture strength testing of a self-passivating tungsten alloy at the micrometre scale

The brittle fracture strength of a self-passivating W-Cr10-Ti2 alloy (in wt.%) was measured through un-notched cantilever bending at the microscopic scale. The material behaved purely elastic and fractured catastrophically in an unstable fashion. An average nominal strength of 5.9 GPa was measured. The scatter in strength was shown to be significantly higher than the sum of all random errors indicating an inherent variability of the material’s strength. The measurements from 28 tests followed a Weibull distribution with a modulus of m = 12. Results from a size effect study at the microscopic scale were successfully predicted through Weibull scaling. Extrapolation into the macroscopic range overestimated the measured three-point bend strength, which is likely due to the presence of large-scale heterogeneities. The test technique sampled a material thickness of only several micrometres and is hence suitable for future ion irradiation studies.     

Synthesis,Culture Medium Stability,and In Vitro and In Vivo Zebrafish Embryo Toxicity of Metal–Organic Framework Nanoparticles

Metal–organic frameworks (MOFs) are among the most attractive porous materials available today. They have garnered much attention for their potential utility in many different areas such as gas storage, separation, catalysis, and biomedicine. However, very little is known about the possible health or environmental risks of these materials. Here, the results of toxicity studies on sixteen representative uncoated MOF nanoparticles (nanoMOFs), which were assessed for cytotoxicity to HepG2 and MCF7 cells in vitro, and for toxicity to zebrafish embryos in vivo, are reported. Interestingly, there is a strong correlation between their in vitro toxicity and their in vivo toxicity. NanoMOFs were ranked according to their respective in vivo toxicity (in terms of the amount and severity of phenotypic changes observed in the treated zebrafish embryos), which varied widely. Altogether these results show different levels of toxicity of these materials; however, leaching of solubilized metal ions plays a main role.     

A novel solventless coating method to graft low‐molecular weight polyethyleneimine on silica fine powders

The overall objective of the present study was to modulate the surface characteristics of aerogel‐like submicron and nanometric particles by coating them with polyethyleneimine (PEI) to suit specific biological applications. A new process for the covalent grafting of low‐molecular weight PEI chains has been described, based on the use of compressed CO₂ as the initiator of the ring opening polymerization of the ethyleneimine monomer, which was performed in the presence of silica particles. Coating was done at low pressure and temperature and in the absence of any organic solvent. Obtained materials were compared with a product prepared following the standard soaking procedure for PEI coating. Materials were characterized regarding composition, structure, surface charge, particle size, morphology, and drug release. The developed process led to the covalent grafting of low‐molecular weight PEI on the silica surface, which conferred an increased thermal stability for the coating and low cytotoxicity to the particles. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2760–2768     

Role of the Symmetry of Multipoint Hydrogen Bonding on Chelate Cooperativity in Supramolecular Macrocyclization Processes

Herein, we analyze the intrinsic chelate effect that multipoint H‐bonding patterns exert on the overall energy of dinucleoside cyclic systems. Our results indicate that the chelate effect is regulated by the symmetry of the H‐bonding pattern, and that the effective molarity is reduced by about three orders of magnitude when going from the unsymmetric ADD–DAA or DDA–AAD patterns to the symmetric DAD–ADA pattern.