Synthesis, characterization, and stability of Fe-MCM-41 for production of carbon nanotubes by acetylene pyrolysis

Fe-substituted MCM-41 molecular sieves with ca. 1, 2, and 3 wt % Fe were synthesized hydrothermally using different sources of colloidal silica (HiSil and Cab-O-Sil) and characterized by ICP, XRD, N2 physisorption, UV-vis, EPR, TPR, and X-ray absorption. Catalysts synthesized from Cab-O-Sil showed higher structural order and stability than those from HiSil. The local environment of Fe in the mesoporous material as studied by UV-vis reveals the dominance of framework Fe in all the as-synthesized Fe-MCM-41 samples. Dislodgement of some Fe species to extraframework location occurs upon calcination, and this effect is more severe for Fe-MCM-41 (2 wt %) and Fe-MCM-41 (3 wt %), as confirmed by EPR and X-ray absorption. These materials have been used as catalytic templates for the production of carbon nanotubes (CNTs) by acetylene pyrolysis at atmospheric pressure. A relationship between the Fe loading in MCM-41 and the carbon species produced during this reaction has been established. Using our optimized conditions for this system, Fe-MCM-41 with ca. 2 wt % Fe showed the best results with particularly high selectivity for single-wall carbon nanotube (SWNT) production. This catalyst was selective for carbon nanotubes with a low amount of amorphous carbon for a narrow range of temperatures from 1073 to 1123 K. To account for the different selectivity of these catalysts for CNTs production, the local environment and chemical state of Fe in the used catalyst was further probed by X-band EPR.     

Heat shock protein 27 interacts with vimentin and prevents insolubilization of vimentin subunits induced by cadmium

Vimentin is an intermediate filament that regulates cell attachment and subcellular organization. In this study, vimentin filaments were morphologically altered, and its soluble subunits were rapidly reduced via cadmium chloride treatment. Cadmium chloride stimulated three major mitogen-activated protein kinases (MAPKs): extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38, and led apoptotic pathway via caspase-9 and caspase-3 activations. In order to determine whether MAPKs were involved in this cadmium-induced soluble vimentin disappearance, we applied MAPK-specific inhibitors (PD98059, SP600125, SB203580). These inhibitors did not abolish the cadmium-induced soluble vimentin disappearance. Caspase and proteosome degradation pathway were also not involved in soluble vimentin disappearance. When we observed vimentin levels in soluble and insoluble fractions, soluble vimentin subunits shifted to an insoluble fraction. As we discovered that heat-shock protein 27 (HSP27) was colocalized and physically associated with vimentin in unstressed cells, the roles of HSP27 with regard to vimentin were assessed. HSP27-overexpressing cells prevented morphological alterations of the vimentin filaments, as well as reductions of soluble vimentin, in the cadmium-treated cells. Moreover, HSP27 antisense oligonucleotide augmented these cadmium-induced changes in vimentin. These findings indicate that HSP27 prevents disruption of the vimentin intermediate filament networks and soluble vimentin disappearance, by virtue of its physical interaction with vimentin in cadmium-treated SK-N-SH cells.     

Cyclometallated Pd(II) azido complexes containing 6-phenyl-2,2'-bipyridyl or 2-phenylpyridyl derivatives: synthesis and reactivity toward organic isocyanides and isothiocyanates

Cyclometallated palladium(II) azido complexes containing C,N,N- or C,N-donor ligands, [Pd(N(3))L](HL = 6-phenyl-2,2'-bipyridine or 2-phenylpyridyl derivatives), showed different reactivities toward organic isocyanides and isothiocyanates. In particular, aryl isocyanides (CN-Ar) underwent insertion into the orthometallated Pd-C bond on the phenyl moiety of the supporting ligand (L) in [Pd(N(3))L] or [Pd(N(3))(PR(3))L] to selectively give carbodiimido [[Pd(N=C=N-Ar)L]], imidoyl [[Pd(N(3))(-C=N-Ar)(PR(3))L]], or imidoyl carbodiimido complexes [[Pd(N=C=N-Ar)(-C=N-Ar)L] or [Pd(N=C=N-Ar)(-C=N-Ar)(PR(3))L]], depending on reaction conditions. Interestingly, reactions of [Pd(N(3))(PR(3))L] with organic isothiocyanates gave unusual dinuclear complexes [(micro-SCN(4)-R)PdL](2), exhibiting the concurrent S- and N-coordinating thio-tetrazole bridge.     

Asymmetric syntheses of fused bicyclic compounds by conjugate additions of allylic organolithium species to activated olefins and subsequent cyclizations

[reaction: see text]. Addition of the configurationally stable organolithium species produced by enantioselective deprotonation of N-Boc-N-(p-methoxyphenyl) allylamines to alpha,beta-unsaturated carbonyl compounds affords 1,4-addition products in good yields with high diastereomeric and enantiomeric ratios. Further transformations of these compounds provide [3.3.0]-, [4.3.0]-, [5.3.0]-, and [5.4.0]-carbocycles and heterocycles with high stereoselectivities.     

Sequential actions of cobalt nanoparticles and palladium(II) catalysts: three-step one-pot synthesis of fenestranes from an enyne and an alkyne diester

A three-step one-pot synthesis of fenestranes from a readily available enyne and an alkyne diester has been carried out with cobalt nanoparticles and palladium(II) as catalysts.     

Poly(dimethylsiloxane) microchip for precolumn reaction and micellar electrokinetic chromatography of biogenic amines

We have demonstrated that precolumn derivatization and capillary electrophoresis separation on a poly(dimethylsiloxane) (PDMS) microchip can be realized as efficient as those on glass microchips. In an optimized condition of micellar electrokinetic chromatography (MEKC), using 25 mM sodium borate buffer (pH 10.0) with 25 mM sodium dodecyl sulfate (SDS) and 5% v/v methanol, the electroosmotic flow in an oxidized PDMS microchip is stabilized within 3% for days. By employing a fluorometric derivatization with o-phthaldialdehyde (OPA) in an optimally designed reaction chamber, four most important biogenic amines occurring in foods, histamine, tyramine, putrescine, and tryptamine, are quantitatively determined in less than 1 min at the levels applicable to real samples. The migration behaviors of anionic OPA-derivatized biogenic amines under the MEKC conditions are analyzed, and it has been found that under our separation conditions, the electrophoretic mobility of the SDS micelles is significantly greater than those of the anions in the aqueous phase. The channel manifold in a PDMS substrate is fabricated using replica molding against a thick photoresist, SU-8, pattern generated by photolithography. The plate with the microchannel pattern is strongly, irreversibly bonded to another PDMS plate by using a new bonding technique, which employs surface oxidation by corona discharge generated from a cheap, handy source, Tesla coil.     

Improved expression by cytomegalovirus promoter/enhancer and behavior of vascular endothelial growth factor gene after myocardial injection of naked DNA

Direct injection of the vascular endothelial growth factor (VEGF) gene plasmid DNA into the myocardium was shown to induce development of new blood vessels to increase the circulation in the heart of patients with coronary artery diseases. However, such angiogenic gene therapy (via naked DNA) was limited by low level of gene expression. Furthermore, the temporal and spatial characteristics of VEGF gene transfer in the heart are not known. In this study, we demonstrated that a plasmid vector, containing the human cytomegalovirus immediate early (HCMV IE) promoter and enhancer, induces greater expression of gene in the rat heart monitored by gene fused to the chloramphenicol acetyl transferase (CAT) reporter, than four different viral and cellular promoters. Interestingly, expression of VEGF121 protein showed an earlier peak, a shorter duration, and a wider distribution than that of CAT only. Therefore, a plasmid vector with an HCMV IE promoter/enhancer provides clear advantages over other previously developed plasmids. Furthermore, expression profile of VEGF121 gene may provide useful information in the design of angiogenic gene therapy in the heart.     

Synthesis and Structures of Titanosiloxane Cage Compounds

Reaction of (triphenylmethyl)silanetriol (1) with cyclopentadienyltitanium trichloride (CpTiCl₃) in the presence of triethylamine as a HCl scavenger gave both compounds of a partial open-cage type {[Ph₃CSiO(OH)]₃(Ph₃CSiO_3/2)(CpTiO_3/2)₄} (2) and cube type (Ph₃CSiO_3/2CpTiO_3/2)₄ (3). The 1:1 reaction of 1 and CpTiCl₃ in toluene solvent at reflux temperature for 3 d afforded compounds 2 (22%) and 3 (36%). When 1 is reacted with a 1.5 fold excess of CpTiCl₃ under the same conditions, compound 3 was obtained in high yield (81%) along with 2 in trace quantities. Compounds 2 and 3 were fully characterized by the analyses of ¹H, ¹³C, ²⁹Si NMR, IR, and FAB MS data. The solid-state structure of 3 was determined by a single crystal X-ray diffraction study. Compound 3 had shown to have catalytic activity for the oxidation of alkenes such as 1-octene, cyclooctene, and norbornene with t-butyl hydrogen peroxide. The effect of solvent was observed in this epoxidation reaction. The order of reactivity were decreased as follows: CHCl₃ > hexane THF.     

Sphingosine mediates FTY720-induced apoptosis in LLC-PK1 cells

FTY720, a synthetic sphingoid base analog, was examined as a new sphingosine kinase inhibitor, which converts endogenous sphingosine into its phosphate form. With 20 microM of FTY720, sphingosine accumulated in the LLC-PK(1) cells in a time- and dose-dependent manner. The FTY720 treated cells showed a high concentration of fragmented DNA, a high caspase-3 like activity and TUNEL staining cells. It was also found that the sphingosine and sphinganine level increased in a time- and dose-dependent manner within 12 h after the FTY720 treatment. The sphingosine kinase activity was reduced by FTY720 as much as other sphingosine kinase inhibitors, N, N-dimethylsphingosine (DMS), dl-threo-dihydrosphingosine (DHS). The fragmented DNA content as a result of the 20 microM of FTY720 treatment and by 5 microM of the exogenously added BSA-sphingosine complex indicated typical apoptosis. Under similar conditions, the accumulated sphingosine concentration in all the cells was almost identical even though the sphingosine distribution inside the cells was somewhat different. These results indicate that the FTY720 induced apoptosis is associated with the inhibition of the sphingosine kinase activity and is strongly associated with the successive accumulation of sphingosine.     

Preparation of block copolymer vesicles in solution

Block copolymer vesicles can be prepared in solution from a variety of different amphiphilic systems. Polystyrene‐block‐poly(acrylic acid), polystyrene‐block‐poly(ethylene oxide), and many other block copolymer systems can produce vesicles of a wide range of sizes; those in the range of 100–1000 nm have been explored extensively. Different factors, such as the absolute and relative block lengths, the presence of additives (ions, homopolymers, and surfactants), the water content in the solvent mixture, the nature and composition of the solvent, the temperature, and the polydispersity of the hydrophilic block, provide control over the types of vesicles produced. Their high stability, resistance to many external stimuli, and ability to package both hydrophilic and hydrophobic compounds make them excellent candidates for use in the medical, pharmaceutical, and environmental fields. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 923–938, 2004