Probing angular correlations in sequential double ionization

We study electron correlation in sequential double ionization of noble gas atoms and HCl in intense, femtosecond laser pulses. We measure the photoelectron angular distributions of Ne+ relative to the first electron in a pump-probe experiment with 8 fs, 800 nm, circularly polarized laser pulses at a peak intensity of a few 10(15) W/cm2. Using a linear-linear pump-probe setup, we further study He, Ar, and HCl. We find a clear angular correlation between the two ionization steps in the sequential double ionization intensity regime.     

Intramolecular cyclization of <Emphasis Type="Italic">N</Emphasis>-propargyl anilines: a new synthetic entry into highly substituted indoles

Indole derivatives are an important class of heterocycle found in a large number of natural products and synthetic pharmaceuticals. Given the low cost and easy availability of N-propargyl anilines, synthesis of indole cores from these versatile structural motifs has attracted a lot of attention in the past decade. In this review, we summarize the most representative and interesting reports on this rapidly advancing area, with special emphasis on mechanistic aspects of the reactions.     

A cellular uptake and cytotoxicity properties study of gallic acid-loaded mesoporous silica nanoparticles on Caco-2 cells

In this study, the effects of intracellular delivery of various concentrations of gallic acid (GA) as a semistable antioxidant, gallic acid-loaded mesoporous silica nanoparticles (MSNs-GA), and cellular uptake of nanoparticles into Caco-2 cells were investigated. MSNs were synthesized and loaded with GA, then characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, N₂ adsorption isotherms, X-ray diffraction, and thermal gravimetric analysis. The cytotoxicity of MSNs and MSNs-GA at low and high concentrations were studied by means of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) test and flow cytometry. MSNs did not show significant toxicity in various concentrations (0–500 μg/ml) on Caco-2 cells. For MSNs-GA, cell viability was reduced as a function of incubation time and different concentrations of nanoparticles. The in vitro GA release from MSNs-GA exhibited the same antitumor properties as free GA on Caco-2 cells. Flow cytometry results confirmed those obtained using MTT assay. TEM and fluorescent microscopy confirmed the internalization of MSNs by Caco-2 cells through nonspecific cellular uptake. MSNs can easily internalize into Caco-2 cells without deleterious effects on cell viability. The cell viability of Caco-2 cells was affected during MSNs-GA uptake. MSNs could be designed as suitable nanocarriers for antioxidants delivery.     

Efficient regio- and stereoselective ring opening of epoxides with alcohols, acetic acid and water catalyzed by ammonium decatungstocerate(IV)

Epoxides can be cleaved in a regio- and stereoselective manner under neutral conditions with alcohols and acetic acid in the presence of catalytic amounts of decatungstocerate(IV) ion, ([CeW₁₀O₃₆]⁸⁻), affording the corresponding β-alkoxy and β-acetoxy alcohols in high yields. In water, ring opening of epoxides occurs with this catalyst to produce the corresponding diols in good yields.     

Kinetics of adsorption and proteolytic cleavage of a multilayer ovalbumin film by subtilisin Carlsberg

Adsorption and proteolytic activity of the enzyme subtilisin Carlsberg have been studied on an immobilized, multilayer ovalbumin film. The cross-linked multilayer substrate permits protease adsorption to be examined unencumbered by the surface inhomogeneity typically observed in monolayer studies of protease surface kinetics. Decline of the protein film was measured over time using ellipsometry. Resulting kinetic data as a function of aqueous enzyme concentration and temperature were well fit by a Langmuir-Michaelis-Menten model for surface proteolysis. We observed that both the protein degradation kinetics and the in situ adsorption data were well described by the proposed model. The temperature dependence of the kinetic rate parameter yielded an activation energy of 12 kcal/mol. Further, the apparent Langmuir adsorption equilibrium constant of the enzyme at the protein/aqueous interface was 0.11 L/mg at 22 degrees C, 0.034 L/mg at 36 degrees C, and 0.011 L/mg at 50 degrees C. Although enzyme adsorption at a given aqueous enzyme concentration decreased at higher temperature, the enzyme cleaved the substrate more rapidly, leading to a net increase in the ovalbumin film degradation rate. We observed that the maximum enzyme coverage on the immobilized protein surface was approximately 40% of a close-packed monolayer at ambient temperature (22 degrees C).     

Microwave Thermolysis: A Rapid and Selective Method for the Cleavage of THP Ethers Using CrO 3 Supported onto Zeolite in Solventless System

Oxidative deprotection of tetrahydropyranyl ethers (THP ethers) using chromium trioxide supported onto zeolite under microwave irradiation in solvent free condition is described.