Heterogeneous enantioselective epoxidation catalyzed by Mn(salen) complexes grafted onto mesoporous materials by phenoxy group

Three chiral Mn(salen) complexes were immobilized into different mesoporous material via phenoxy group by a simplified method and they show high activity and enantioselectivity for asymmetric epoxidation of various substituted unfunctional olefins. The heterogeneous Mn(salen) catalysts show comparable ee values for asymmetric epoxidation of styrene and 6-cyano-2,2-dimethylchromene and much higher ee values for epoxidation of a-methylstyrene (heterogeneous 79.7% ee versus homogeneous 26.4% ee) and cis-beta-methylstyrene (heterogeneous 94.9% ee versus homogeneous 25.3% ee for cis-epoxide) than the homogeneous catalysts. These heterogeneous catalysts also remarkably alter the cis/trans ratio of epoxides for asymmetric epoxidation of cis-beta-methylstyrene (heterogeneous 21 versus homogeneous 0.38). The axial tether group does not make a big effect on ee values and the increase in ee value and change in cis/trans ratio are mainly attributed to the axial immobilization mode and the support effect of heterogeneous catalysts. The catalysts keep constant ee values for the recycle tests of eight times for asymmetric epoxidation of a-methylstyrene. And several possibilities were proposed to elucidate the difference in ee values of heterogeneous catalysts from homogeneous catalysts. (c) 2005 Elsevier B.V. All rights reserved.

Post-grafting preparation of large-pore mesoporous materials with localized high content titanium doping

A new post-grafting process, consisting of two steps of substrate preparation and sol - gel post-grafting, has been developed to prepare titanium-doped mesoporous SBA-15 material with a double-layered structure and locally concentrated titanium content at the inner pore surface. With this novel technique, the single phased and originally ordered mesostructures can be well conserved; in the conventional direct synthesis they can be partially damaged when the frameworks are doped with high content heteroatoms. Titanium species exist in an isolated, tetrahedral structure and are localized at the pore surface; this is beneficial to both reactant access and product release. Characterization with XRD, N-2 adsorption/desorption isotherms, HREM/ EDS, ICP, UV - Vis, and the newly developed UV - Raman spectroscopy confirm these results. Preliminary catalytic tests with the selective epoxidation of cyclohexene show good catalytic activity. Among them, sample TiSBA-15-10 with a Si : Ti molar ratio of 10 shows a TON value of 75 and a highest product ( epoxide) yield of 55%.

Synthesis and catalytic reactivity of MCM-22/ZSM-35 composites for olefin aromatization

A series of MCM-22/ZSM-35 composites has been hydrothermally synthesized and characterized by XRD, SEM, particle size distribution analysis, N-2 adsorption and NH3-TPD techniques. Pulse and continuous flow reactions were carried out to evaluate the catalytic performances of these composites in aromatization of olefins, respectively. It was found that MCM-22/ZSM-35 composites could be rapidly crystallized at 174 degrees C with an optimal gel composition of SiO2/Al2O3=25, Na2O/SiO2=0.11, HMI/SiO2=0.35, and H2O/SiO2=45 (molar ratio), of which the weight ratio of ZSM-35 zeolite in the composite relied on the crystallization time. The coexistence of MCM-22 and ZSM-35 in the composite (MCM-22/ZSM-35=45/55 wt/wt) was observed to exert a notable synergistic effect on the aromatization ability for butene conversion and FCC gasoline updating, possibly due to the intergrowth of some MCM-22 and ZSM-35 layers.

Large-pore mesoporous SBA-15 silica particles with submicrometer size as stationary phases for high-speed CEC separation

A new mesoporous sphere-like SBA-15 silica was synthesized and evaluated in terms of its suitability as stationary phases for CEC. The unique and attractive properties of the silica particle are its submicrometer particle size of 400 nm and highly ordered cylindrical mesopores with uniform pore size of 12 nm running along the same direction. The bare silica particles with submicrometer size have been successfully employed for the normal-phase electrochromatographic separation of polar compounds with high efficiency (e.g., 210 000 for thiourea), which is matched well with its submicrometer particle size. The Van Deemeter plot showed the hindrance to mass transfer because of the existence of pore structure. The lowest plate height of 2.0 mu m was obtained at the linear velocity of 1.1 mm/s. On the other hand, because of the relatively high linear velocity (e.g., 4.0 mm/s) can be generated, high-speed separation of neutral compounds, anilines, and basic pharmaceuticals in CEC with C-18-modified SBA-15 silica as stationary phases was achieved within 36, 60, and 34 s, respectively.

Trigo Embrapa 41: nova cultivar para Minas Gerais, Goiás e Distrito Federal.

1997

Judicial Perspectives on the Operation of s.41 and the Relevance and Admissibility of Prior Sexual History Evidence: Four Scenarios

Judicial Perspectives on the Operation of s.41 and the Relevance and Admissibility of Prior Sexual History Evidence: Four scenarios. N.Kibble. Crim.L.R. 2005 190. RAE2008

Practice links [Issue 41, February 2011]

Practice Links is a free e-publication for practitioners working in Irish social services, voluntary and nongovernmental sectors. Practice Links was created to enable practitioners to keep up-to-date with new publications, electronic resources and conference opportunities. Issue 41 features a review of the research thesis which examines the effects of parental imprisonment upon children's behaviour.

Antibody deficiency due to a missense mutation in CD19 demonstrates the importance of the conserved tryptophan 41 in immunoglobulin superfamily domain formation.

Immunoglobulin superfamily (IgSF) domains are conserved structures present in many proteins in eukaryotes and prokaryotes. These domains are well-capable of facilitating sequence variation, which is most clearly illustrated by the variable regions in immunoglobulins (Igs) and T cell receptors (TRs). We studied an antibody-deficient patient suffering from recurrent respiratory infections and with impaired antibody responses to vaccinations. Patient's B cells showed impaired Ca(2+) influx upon stimulation with anti-IgM and lacked detectable CD19 membrane expression. CD19 sequence analysis revealed a homozygous missense mutation resulting in a tryptophan to cystein (W52C) amino acid change. The affected tryptophan is CONSERVED-TRP 41 located on the C-strand of the first extracellular IgSF domain of CD19 and was found to be highly conserved, not only in mammalian CD19 proteins, but in nearly all characterized IgSF domains. Furthermore, the tryptophan is present in all variable domains in Ig and TR and was not mutated in 117 Ig class-switched transcripts of B cells from controls, despite an overall 10% amino acid change frequency. In vitro complementation studies and CD19 western blotting of patient's B cells demonstrated that the mutated protein remained immaturely glycosylated. This first missense mutation resulting in a CD19 deficiency demonstrates the crucial role of a highly conserved tryptophan in proper folding or stability of IgSF domains.

Inclusion of poorly soluble drugs in highly ordered mesoporous silica nanoparticles

Silica nanoparticles (MSNs) with a highly ordered mesoporous structures (103A) with cubic Im3 m have been synthesized using triblock copolymers with high poly(alkylene oxide) (EO) segments in acid media. The produced nanoparticles displayed large specific surface area (approximately 765 cm(2)/g) with an average particles size of 120 nm. The loading efficiency was assessed by incorporating three major antiepileptic active substances via passive loading and it was found to varying from 17 to 25%. The state of the adsorbed active agents was further analyzed using differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD). Dissolution studies revealed rapid release profiles within the first 3 h. The viability of 3T3 endothelial cells was not affected in the presence of MSNs indicating negligible cytotoxicity. 2009 Elsevier B.V. All rights reserved.