Two-photon uncaging of neurochemicals using inorganic metal complexes

Neuroactive compounds can be photoreleased by means of two-photon excitation using a new kind of transition metal-based caged compound.     

Synthesis,biological evaluation and DNA binding properties of novel mono and bisnaphthalimides

A novel series of mono and bisnaphthalimides was synthesized and their antiproliferative activities were evaluated against three tumor cell lines. Bisnaphthalimides 3 and 4, bearing a pyrazine ring fused to the naphthalimide system, showed activities in the order of 10(-8) microM, similar to elinafide. DNA binding properties and the ability to induce DNA damage were studied for some of the most active compounds.     

The structures of 2-(4,5-dihydro-5-aryl-3-isoxazolyl)-1-arylethanone oximes. An unusual behaviour in its 1H-NMR and mass spectra

The reaction of dibenzalacetones substituted on the aromatic ring with hydroxylamine hydrochloride and potassium hydroxide in refluxing ethanol affords several compounds. Herein, we report the structures and spectral properties of several oximes of 2-(4,5-dihydro-5-aryl-3-isoxazolyl)-1-arylethanones 6 . Unusual behaviour on its ¹H-nmr and mass spectra was observed. Single crystal X-ray diffraction was performed on compound 6d to support our structural considerations abouth the title compounds.     

Pair correlation function of short-ranged square-well fluids

We have performed extensive Monte Carlo simulations in the canonical (NVT) ensemble of the pair correlation function for square-well fluids with well widths lambda-1 ranging from 0.1 to 1.0, in units of the diameter sigma of the particles. For each one of these widths, several densities rho and temperatures T in the ranges 0.1< or =rhosigma(3)< or =0.8 and T(c)(lambda) less or approximately T less or approximately 3T(c)(lambda), where T(c)(lambda) is the critical temperature, have been considered. The simulation data are used to examine the performance of two analytical theories in predicting the structure of these fluids: the perturbation theory proposed by Tang and Lu [Y. Tang and B. C.-Y. Lu, J. Chem. Phys. 100, 3079 (1994); 100, 6665 (1994)] and the nonperturbative model proposed by two of us [S. B. Yuste and A. Santos, J. Chem. Phys. 101 2355 (1994)]. It is observed that both theories complement each other, as the latter theory works well for short ranges and/or moderate densities, while the former theory works for long ranges and high densities.     

Fast,accurate and robust adaptive finite difference methods for fractional diffusion equations

The computation time required by standard finite difference methods with fixed timesteps for solving fractional diffusion equations is usually very large because the number of operations required to find the solution scales as the square of the number of timesteps. Besides, the solutions of these problems usually involve markedly different time scales, which leads to quite inhomogeneous numerical errors. A natural way to address these difficulties is by resorting to adaptive numerical methods where the size of the timesteps is chosen according to the behaviour of the solution. A key feature of these methods is then the efficiency of the adaptive algorithm employed to dynamically set the size of every timestep. Here we discuss two adaptive methods based on the step-doubling technique. These methods are, in many cases, immensely faster than the corresponding standard method with fixed timesteps and they allow a tolerance level to be set for the numerical errors that turns out to be a good indicator of the actual errors.     

Combination of high pressure with nisin or lysozyme to further process mechanically recovered poultry meat

Abstract

The combined effect of high pressure processing (HPP) and nisin or lysozyme on aerobic mesophile and psychrotrophe populations of mechanically recovered poultry meat (MRPM) was evaluated. Nisin (0, 12.5, 100 and 200ppm) or lysozyme (0 and 150ppm) were added to MRPM, and vacuum-packaged samples were treated at 350 and 450 MPa for 5 and 15min at 20°C. In mesophiles, reductions above 4 log CFU/g were found in some samples. Psychrotrophes proved more sensitive; in MRPM containing 200 ppm of nisin treated at 450 MPa for 15min, no growth was detected (a lethality of more than 8 log units). There was no synergistic effect between HPP and lysozyme. In contrast, combination of HPP and nisin is a promising nonthermal preservation treatment.     

A finite difference method with non-uniform timesteps for fractional diffusion and diffusion-wave equations

An implicit finite difference method with non-uniform timesteps for solving fractional diffusion and diffusion-wave equations in the Caputo form is presented. The non-uniformity of the timesteps allows one to adapt their size to the behaviour of the solution, which leads to large reductions in the computational time required to obtain the numerical solution without loss of accuracy. The stability of the method has been proved recently for the case of diffusion equations; for diffusion-wave equations its stability, although not proven, has been checked through extensive numerical calculations.     

Enantioselective synthesis of α-hydroxy-β-amino acids from α-amino acids mediated by sulfoxides

The synthesis of the optically pure (2S,3S)- and (2R,3S)-3-amino-2-hydroxybutanoic acids from commercially available (S)-alanine derivatives is reported. The key step of the synthetic sequence is the conversion of γ-amino sulfoxides into γ-amino alcohols by treatment with TFAA and sym-collidine. The efficiency of this non-oxidative Pummerer reaction (NOPR) is dependent on the stereochemistry of the starting sulfoxide.     

Terracinolides A and B, Two Bishomoditerpene Lactones with a Novel Carbon Framework from Euphorbia terracina

A methanolic extract of Euphorbia terracina L. has been shown to contain two peracylated polyhydroxy terpenoid lactones with a novel C(22) carbon framework. These metabolites, which have been named terracinolides A (1) and B (2), are based on the same parent compound, but differ in the nature of one of the acyl residues. This novel skeletal system is formally derived from the jatrophane framework by addition of a two-carbon fragment on C-17 (jatrophane numbering).