Structural properties of nonionic cyclodextrin colloids in water

The amphiphilic character in water of a novel class of chemically modified cyclodextrins has been investigated by means of small-angle X-ray scattering and light scattering. The introduction ofhydrophilic oligo(ethylene glycol) onto the secondary side of heptakis[6-alkylthio-6-deoxy-2-oligo(ethylene glycol)]-beta-cyclodextrins produces an enhanced water solubility of these molecules. Shape and dimensions of the generated micellar aggregates, analyzed in terms of a suitable core-shell model, remain stable in the wide concentration range explored. The highly associative behavior of these macromolecules is evidenced by the very low value of the critical micelle concentration (cmc), which is about 2 orders of magnitude smaller than the cmc usually obtained for traditional surfactant. Despite the complex geometry of this novel macromolecule, shape and dimensions of generated micellar aggregates can be properly described according to the thermodynamic approaches generally used for amphiphilic molecules and block copolymers. Results show how the modulation of hydrophobic and hydrophilic components sensitively influence the structural features of the generated aggregates thus offering the possibility to control molecular organization in a manner similar to that for traditional colloids. For all the classes of the investigated systems, the small micelles have been found in equilibrium with polydisperse large aggregates of entangled micelles. These novel nonionic colloidal systems combine inclusion and transport properties of host macrocycles, such as cyclodextrin, together with the increased stability of colloidal aggregates, and may be of interest for their potential application as innovative drug delivery systems.     

The interaction of H2, CO, CO2, H2O and NH3 on ZnO surfaces: an Oniom Study

We have used the Oniom method with three layers in order to study the interaction of CO, H₂, H₂O, NH₃ and CO₂ molecules with the ZnO surfaces using a (ZnO)₃₄₈ cluster model. The layers are divided into the high layer at the CCSD level, the medium layer at the RHF level and the low level layer using the UFF force field method. The orbital and binding energies of the adsorbed molecules, Mulliken and ChelpG charges as well as geometrical parameters were analyzed and compared with the available experimental and theoretical data.     

Er as marker for order–disorder determination in the PbTiO3 system

Er³⁺ ions were added to the PbTiO₃ network using the polymeric precursor method to characterize the order–disorder transformation found in this material by means of experimental and theoretical approach. The disordered and ordered material structures were studied by photoluminescence measurements, X-ray diffraction (XRD) and UV–visible spectroscopy. The Er³⁺ ions served as a marker to identify the structural short-range order beginning in the PbTiO₃ matrix. From photoluminescence results it was concluded that disordered PbTiO₃ powders have a certain short range order in the network that are undetected by XRD measurements. The electronic structures were calculated by the ab initio periodic method in DFT level with the non-local B3LYP hybrid approximation for the Ti atom site interpretation using density of states (DOS) results. This analysis enabled understanding that Ti atom sphere coordination can create possible states for radioactive return and trap of electron–holes pair.     

Polymer heterogenized iridium amino complexes. Catalyzed reduction of nitrobenzene under WGSR conditions

The activation studies for catalytic reduction of nitrobenzene to aniline by iridium(I) complexes, [Ir(COD)(amine)₂]PF₆ (COD=1,5-cyclooctadiene, amine =4-picoline, 3-picoline, 2-picoline, or pyridine) heterogenized on poly(4-vinylpyridine) in aqueous 2-ethoxyethanol are described. The aniline formation (mmol, based on CO₂ formed after 9 h) followed the order: 4-picoline (0.068)>2-picoline (0.052)>3-picoline (0.046)≥pyridine (0.042) for 1.0×10⁻⁴ mol Ir/0.5 g of polymer, 0.26 mL of nitrobenzene, 10 mL of 2-ethoxyethanol/water, 8/2, v/v, P(CO)=0.9 atm, at 100°C.     

Ceramic crucibles: a new alternative for melting of PbO-BiO1.5-GaO1.5 glasses

PbO-Bi₂O₃-Ga₂O₃ glasses present interesting properties such as good transmission in the mid-infrared region, high magnetic Verdet constant and non-linear properties. The processing of these heavy-metal-oxide (HMO) glasses is limited by the high corrosive nature of the melt, even in relation to noble metal crucibles. In this work, three kinds of ceramic crucibles (alumina, tin oxide and zirconia) were tested for melting HMO glasses. The main physical properties of the prepared glasses, such as the characteristic temperatures, optical transmission were studied in function of the crucible nature, time/temperature melting parameters. The incorporation of crucible material in the glasses was determined by ICP and atomic absorption. The maximum glass contamination from the crucible was 2.9, 1.6 and 3.6 mol% for Al₂O₃, SnO₂ and ZrO₂ crucibles, respectively, when melting was done at 900 °C/240 min, for zirconia crucibles and at 1000 °C/60 min, for the other two crucibles. The evolution of the physical properties was discussed as a function of contamination degree.     

Copolymerization of styrene with (Z)-1,3-pentadiene in the presence of a syndiotactic-specific catalyst

Copolymerization of styrene with (Z)-1,3-pentadiene affords copolymers mostly containing 1,2 pentadiene units. Both the styrene and the pentadiene units are in syndiotactic arrangement but the comonomer sequence distribution is far from bernoullian. Interestingly, the behavior of (Z)-1,3-pentadiene does not change much when polymerization temperature raises from −20 to +20°C, notwithstanding that (Z)-1,3-pentadiene affords a 1,2-syndiotactic homopolymer at −20°C but a prevailingly 1,4 cis homopolymer at +20°C. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2697–2702, 1997     

Anti-Inflammatory Activity of a CB2 Selective Cannabinoid Receptor Agonist: Signaling and Cytokines Release in Blood Mononuclear Cells

The endocannabinoid system (ECS) exerts immunosuppressive effects, which are mostly mediated by cannabinoid receptor 2 (CBR2), whose expression on leukocytes is higher than CBR1, mainly localized in the brain. Targeted CBR2 activation could limit inflammation, avoiding CBR1-related psychoactive effects. Herein, we evaluated in vitro the biological activity of a novel, selective and high-affinity CBR2 agonist, called JT11, studying its potential CBR2-mediated anti-inflammatory effect. Trypan Blue and MTT assays were used to test the cytotoxic and anti-proliferative effect of JT11 in Jurkat cells. Its pro-apoptotic activity was investigated analyzing both cell cycle and poly PARP cleavage. Finally, we evaluated its impact on LPS-induced ERK1/2 and NF-kB-p65 activation, TNF-α, IL-1β, IL-6 and IL-8 release in peripheral blood mononuclear cells (PBMCs) from healthy donors. Selective CB2R antagonist SR144528 and CBR2 knockdown were used to further verify the selectivity of JT11. We confirmed selective CBR2 activation by JT11. JT11 regulated cell viability and proliferation through a CBR2-dependent mechanism in Jurkat cells, exhibiting a mild pro-apoptotic activity. Finally, it reduced LPS-induced ERK1/2 and NF-kB-p65 phosphorylation and pro-inflammatory cytokines release in human PBMCs, proving to possess in vitro anti-inflammatory properties. JT11 as CBR2 ligands could enhance ECS immunoregulatory activity and our results support the view that therapeutic strategies targeting CBR2 signaling could be promising for the treatment of chronic inflammatory diseases.