SIMULTANEOUS POLV(V1NVL ACETATE)/SILICA NETWORKS. INFLUENCE OF CROSSLINKING AGENTS

The modification of the rate or formation of interpenetrant simultaneous inorsjanic-organic (SIPIN) networks of poly(vinyl acetate) (PVAc)-SiO; was studied. The P(VAc) network was formod by radical polymerization with benzoyl peroxide in the presence of a crosslinked monomer, diethylen glycol bis maleate. SiO: network was obtained by sol-gel reaction of tetraethoxysilane (TEOS) catalyzed by radical polymeriznble acids: maleic acid (MA) and acrylic acid (AA) The reaction medium was the ethylic alcohol-water mixture. The formation rate of SIPIN depends on the ratio of initial organic over aqueous phases in case of caialysis by MA. The yelling limes for MA are higher than those for AA. This behavior inversely proponional to the acid strength is assigned to the selective interaction of the acids wiih the hydrocarbonated or aqueous zone of initial systems. Crotonic acid (CrA) is partitioned in the hydrocarbonate zone where TEOS also lies The glass transition temperature of organic network, P(VAc) increases with the increase of crosslinking agent concentration. It is higher in the network prepared in presence of MA owing to the higher number of hydrogen bonds induced by COOH.     

Nanopore generation in hybrid polycyanurate/poly(ε-caprolactone) thermostable networks

Novel nanoporous thermosetting films were obtained from thermostable polycyanurate (PCN)-based hybrid networks synthesized by polycyclotrimerization of cyanate ester of bisphenol E in the presence of a modifier reactive toward cyanate groups, i.e. dihydroxy-telechelic poly(ε-caprolactone) (PCL). The nanoporous structure was generated in PCN/PCL hybrid networks after extraction of unreacted free PCL sub-chains which were not chemically incorporated into the PCN cross-linked framework. Structure–property relationships for precursory and porous PCN/PCL hybrid networks were investigated using a large array of physico-chemical techniques. The porosity associated with the networks after extraction was more particularly evaluated by SEM and DSC-based thermoporometry: pore sizes around 10–90 nm were determined along with pore volumes as high as about 0.3 cm³ g⁻¹. Density and dielectric measurements strongly suggested the occurrence of closed pore structures. Due to their high thermal stability as investigated by TGA, nanoporous PCN/PCL hybrid cross-linked films could be considered as promising materials for potential applications as thermostable membranes.     

Yb valence states in YbC2: a HERFD-XANES spectroscopic investigation

The valence state of Yb in YbC(2) was analyzed using high-energy-resolution fluorescence detection (HERFD) X-ray absorption near-edge structure (XANES) spectroscopy and time-of-flight neutron powder diffraction to clarify a controversy in the literature. The unit cell volume of YbC(2) suggests a mixed Yb valence, which was formerly determined to be 2.8 by magnetization measurements and paramagnetic neutron scattering techniques. However, the nature of the intermediate valence was not clearly established. Both homogeneous and heterogeneous mixed valences were assumed in different publications. The temperature-dependent behavior of the valence state was only predicted, albeit not explicitly studied. In this work, the valence state of Yb in YbC(2) is, therefore, investigated thoroughly by HERFD-XANES spectroscopy at low and high temperatures. Our measurements result in an average Yb valence of 2.81 that is temperature-independent from 15 to 1123 K. These findings are confirmed by neutron powder diffraction experiments, which reveal a constant C-C distance of 128.7(9) pm in a temperature range from 5 to 100 K. A significant temperature dependence of the Yb valence state in YbC(2) can, therefore, be excluded by our experimental results.     

Microwave-assisted seeded growth of lanthanide-based nanoparticles for imaging and therapy

Size control: Particles designed for imaging and therapy need to be size tunable to ensure their optimal performance. A highly reproducible procedure for the preparation of uniform, spherical, lanthanide-based nanoparticles (NPs) was developed. The size of the particles can be predefined to an accuracy of up to a few nanometers by microwave-generated temperature control and the choice of aging time (see figure).     

Structural portrait of filamin interaction mechanisms

We review the most recent findings on human filamin structure, with particular emphasis on the relationships between structure, function, and interaction. Filamin is a cytoskeletal actin-binding protein and it is therefore crucial in providing cells with the necessary mechanical and dynamical properties. Filamentous actin cross-linking by filamin is regulated by a number of other proteins and the molecular mechanisms of this complex interaction network can be understood by highlighting the structural features of isolated filamin moieties and of their complexes with several partners. Here we describe first the structure-function relationships of the isolated filamin, its flexibility, and its dimerization mechanism. Secondly, we illustrate the structural mechanism with which filamin can recognize its partners, both the actin filaments and the regulatory proteins.     

Synthesis of new sugar-based surfactants and evaluation of their hemolytic activities

The synthesis of four sugar-based surfactants derived from glucose and (R)-12-hydroxystearic acid is described. The surfactants have a hydroxy group in the hydrophobic part, which is either free or acylated using acetyl chloride, hexanoyl chloride, or myristoyl chloride. Three of the synthesized surfactants are water-soluble and are evaluated with respect to their CMCs and hemolytic activities. The fourth surfactant has limited water solubility and is not further included in the study. The investigated surfactants are all hemolytic close to their respective CMC indicating that their use in parenteral formulations may be limited. Nevertheless, surfactants having the proposed structure appear as promising alternatives to existing solubilizing agents for pharmaceutical applications.     

Cu-catalyzed N-arylation of oxazolidinones: an efficient synthesis of the kappa-opioid receptor Agonist CJ-15161

An efficient method for intermolecular N-arylation of oxazolidinones using catalytic copper in the presence of a bidentate ligand is reported. The conditions allow the use of copper and can be used to prepare enantiopure N-aryl beta-amino alcohols. A short, scalable synthesis of CJ-15,161 is also reported. The required amines were obtained from the precursor alpha-amino acids or, more conveniently, from the corresponding 1,2-amino alcohols.     

Iron(III)-Doped, Silica Nanoshells: A Biodegradable Form of Silica

Silica nanoparticles are being investigated for a number of medical applications; however, their use in vivo has been questioned because of the potential for bioaccumulation. To obviate this problem, silica nanoshells were tested for enhanced biodegradability by doping iron(III) into the nanoshells. Exposure of the doped silica to small molecule chelators and mammalian serum was explored to test whether the removal of iron(III) from the silica nanoshell structure would facilitate its degradation. Iron chelators, such as EDTA, desferrioxamine, and deferiprone, were found to cause the nanoshells to degrade on the removal of iron(III) within several days at 80 °C. When the iron(III)-doped, silica nanoshells were submerged in fetal bovine and human serums at physiological temperature, they also degrade via removal of the iron by serum proteins, such as transferrin, over a period of several weeks.