Improvement of electrospun polymer fiber meshes pore size by femtosecond laser irradiation

Polymer meshes have recently attracted great attention due to their great variety of applications in fields such as tissue engineering and drug delivery. Poly(?-caprolactone) nanofibers were prepared by electrospinning giving rise to porous meshes. However, for some applications in tissue engineering where, for instance, cell migration into the inner regions of the mesh is aimed, the pore size obtained by conventional techniques is too narrow. To improve the pore size, laser irradiation with femtosecond pulses (i.e., negligible heat diffusion into the polymer material and confined excitation energy) is performed. A detailed study of the influence of the pulse energy, pulse length, and number of pulses on the topography of electrospun fiber meshes has been carried out, and the irradiated areas have been studied by scanning electron microscopy, contact angle measurements and spectroscopic techniques. The results show that using the optimal laser parameters, micropores are formed and the nature of the fibers is preserved.     

Structural insights for the design of new PPARgamma partial agonists with high binding affinity and low transactivation activity

Peroxisome Proliferator-Activated Receptor γ (PPARγ) full agonists are molecules with powerful insulin-sensitizing action that are used as antidiabetic drugs. Unfortunately, these compounds also present various side effects. Recent results suggest that effective PPARγ agonists should show a low transactivation activity but a high binding affinity to inhibit phosphorylation at Ser273. We use several structure activity relationship studies of synthetic PPARγ agonists to explore the different binding features of full and partial PPARγ agonists with the aim of differentiating the features needed for binding and those needed for the transactivation activity of PPARγ. Our results suggest that effective partial agonists should have a hydrophobic moiety and an acceptor site with an appropriate conformation to interact with arm II and establish a hydrogen bond with Ser342 or an equivalent residue at arm III. Despite the fact that interactions with arm I increase the binding affinity, this region should be avoided in order to not increase the transactivation activity of potential PPARγ partial agonists.     

Preparation of polyurethane elastomers (PUEs) in a high‐throughput workflow

High‐throughput experimentation (HTE) represents a promising and versatile approach for polyurethane (PU) research as a tool to rapidly screen and characterize a large number of samples in an automated way. To realize a unique HTE workflow for the research and development of PU elastomers (PUEs), the use of parallel automated formulation and coating platforms at Flamac were explored. To evaluate the applicability of HTE for PUEs, four different PU systems were investigated with different reactivities and viscosities. All prepared PUEs were evaluated by conventional physical testing methods measuring the E‐modulus, tensile‐elongation and the hardness properties revealing similar trends as conventionally prepared PUEs indicating the viability of the HTE approach. In addition, the properties of the PUEs were also investigated using downscaled microtensile bars as well as depth‐sensing indentation, again, revealing similar trends. With this proof of principle study, we demonstrated for the first time that HTE can also be extended to polymeric materials based on high reactive and viscous raw materials in combination with complex technologies. The reported results provide a basis for the use of HTE approaches for preparing, screening and characterizing large numbers of PUEs for R&D purposes. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

MnO x /ZrO2 gel-derived materials for hydrogen peroxide decomposition

Manganese-yttrium-zirconium mixed oxide nanocomposites with three different Mn loadings (5, 15 and 30 wt%) were prepared by sol–gel synthesis. Amorphous xerogels were obtained for each composition. Their structural evolution with the temperature and textural properties were examined by thermogravimetry/differential thermal analysis, X-ray diffraction, diffuse reflectance UV–vis spectroscopy and N₂ adsorption isotherms. Mesoporous materials with high surface area values (70–100 m² g⁻¹) were obtained by annealing in air at 550 °C. They are amorphous or contain nanocrystals of the tetragonal ZrO₂ phase (T-ZrO₂) depending on the Mn amount and exhibit Mn species with oxidation state higher than 2 as confirmed by temperature programmed reduction experiments. T-ZrO₂ is the only crystallizing phase at 700 °C while the monoclinic polymorph and Mn₃O₄ start to appear only after a prolonged annealing at 1,000 °C. The samples annealed at 550 °C were studied as catalysts for H₂O₂ decomposition in liquid phase. Their catalytic activity was higher than that of previously studied Mn/Zr oxide systems prepared by impregnation. Catalytic data were described by a rate equation of Langmuir type. The decrease of catalytic activity with time was related to dissolution of a limited fraction (up to 15%) of Mn into the H₂O₂/H₂O solution.     

Self-assembly of chiral trans-cyclobutane-containing β-dipeptides into ordered aggregates

Two chiral synthetic β-dipeptides have been constructed, one with two trans-cyclobutane residues and the other with one trans and one cis fragment, 1 and 2, respectively, and investigated to get insight into the non-covalent interactions responsible for their self-assembly to form ordered aggregates, as well into parameters such as their morphology and size. Experimental evidence of the formation of these assemblies was provided by spectroscopy, microscopy and X-ray diffraction experiments that suggest the formation of nanoscale helical aggregates. This process involves a conformational change in the molecules of each dipeptide with respect to the preferred conformation of the isolated molecules in solution. A high-resolution NMR spectroscopy study allowed the determination of the dynamics of the gelation process in [D(8)]toluene and the sol-gel transition temperature, which was around 270 K in this solvent at a concentration of 15 mM. NMR spectroscopy experiments also provided some information about conformational changes involved in the sol-gel transition and also suggested a different gel packing for each dipeptide. These observations have been nicely explained by computational studies. The self-assembly of the molecules has been modelled and suggested a head-to-head molecular arrangement for 1 and a head-to-tail arrangement for 2 to give helical structures corresponding to hydrogen-bonded single chains. These chains interact with one another in an antiparallel way to afford bundles, the significant geometry parameters of which fit well to the main peaks observed in wide-angle X-ray diffraction spectra of the aggregates in the solid state.     

Layered structure of room-temperature ionic liquids in microemulsions by multinuclear NMR spectroscopic studies

Microemulsions form in mixtures of polar, nonpolar, and amphiphilic molecules. Typical microemulsions employ water as the polar phase. However, microemulsions can form with a polar phase other than water, which hold promise to diversify the range of properties, and hence utility, of microemulsions. Here microemulsions formed by using a room‐temperature ionic liquid (RTIL) as the polar phase were created and characterized by using multinuclear NMR spectroscopy. ¹H, ¹¹B, and ¹⁹F NMR spectroscopy was applied to explore differences between microemulsions formed by using 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim][BF₄]) as the polar phase with a cationic surfactant, benzylhexadecyldimethylammonium chloride (BHDC), and a nonionic surfactant, Triton X‐100 (TX‐100). NMR spectroscopy showed distinct differences in the behavior of the RTIL as the charge of the surfactant head group varies in the different microemulsion environments. Minor changes in the chemical shifts were observed for [bmim]⁺ and [BF₄]^? in the presence of TX‐100 suggesting that the surfactant and the ionic liquid are separated in the microemulsion. The large changes in spectroscopic parameters observed are consistent with microstructure formation with layering of [bmim]⁺ and [BF₄]^? and migration of Cl^? within the BHDC microemulsions. Comparisons with NMR results for related ionic compounds in organic and aqueous environments as well as literature studies assisted the development of a simple organizational model for these microstructures.     

Drug repositioning for anti-tuberculosis drugs: an in silico polypharmacology approach

Molecular Diversity - Development of potential antitubercular molecules is a challenging task due to the rapidly emerging drug-resistant strains of Mycobacterium tuberculosis (M.tb)....     

Arithmetic properties of ℓ-regular partitions

For a given prime p, by studying p  -dissection identities for Ramanujan?s theta functions ψ(q)$\psi (q)$ and f(−q)$f(-q)$, we derive infinite families of congruences modulo 2 for some ?  -regular partition functions, where ?=2,4,5,8,13,16$?=2,4,5,8,13,16$.     

Aptamer‐Assisted Assembly of Gold Nanoframe Dimers

The assembly of nanoframe dimers assisted by aptamer‐functionalized smaller spherical gold nanoparticles as prospective surface‐enhanced Raman scattering (SERS) biotraps for riboflavin, an important molecule for biological electron transfer reactions, is reported. In this approach, the aptamer‐coated gold nanoparticles designed for selective binding of riboflavin also serve as the electrostatic driver for nanoframe dimerization in dilute solutions. The gold nanoframe dimers provide unique conditions for plasmonic coupling in a hot spot with sufficient space for the binding of bulky biomolecules. The use of an aptamer allows for highly selective binding of the targeted analyte as compared with conventional organic ligands with excellent low detection limit of one micromole of riboflavin.