Smectic order parameters via liquid crystal NMR spectroscopy: Application to a partial bilayer smectic A phase

Solute molecules were dissolved in the liquid crystal 4-cyano-4??-n-octyloxybiphenyl (8OCB), known to form a partial bilayer smectic-A phase. Through measurement of solutes?? and solvent??s orientational order parameters via nuclear magnetic resonance spectroscopy, and their analysis via a statistical thermodynamic density functional theory, values of the solvent??s positional order parameters and solutes?? positional-orientational distribution functions were obtained. Near to the transition to the nematic phase, the main positional order parameter of the smectic liquid crystal turned out to be comprised in the interval 0.4?C0.6, though the quality of the fittings assuming the phase as nematic all across the temperature range investigated was only slightly worse. This may be ascribed to the looseness of the partial bilayer smectic structure. Solutes were found to preferentially lie in those regions where liquid crystal molecule terminal chains are located.      

Allyl palladium complexes bearing carbohydrate-based N-heterocyclic carbenes: Anticancer agents for selective and potent in vitro cytotoxicity

Novel allyl palladium compounds stabilized by carbohydrate-based N-heterocyclic carbenes (NHCs) were prepared and characterized by nuclear magnetic resonance, high-resolution mass spectrometry and elemental analysis. The antiproliferative activity of the compounds was tested on a panel of different tumor lines, especially ovarian cancer and MRC-5 human lung fibroblasts (nontumor cells). These experiments showed that both mixed NHC/PPh₃ and NHC/PTA (PTA = 1,3,5-triaza-7-phosphaadamantane) allyl complexes have IC₅₀ (half maximal inhibitory concentration) values comparable and sometimes even significantly lower than cisplatin. Moreover, the mixed NHC/PTA allyl complexes exhibit good activity toward the seven tumor lines tested with a substantial inactivity against normal cells, a necessary condition to avoid the general cytotoxicity of a metallo-drug. Furthermore, this subclass of compounds proved particularly active on the A549 lung cancer tumor line (up to 100-fold more cytotoxic than cisplatin) and exhibited satisfactory cytotoxicity against KURAMOCHI and OVCAR3 cell lines, which are currently considered the best in vitro models for serous ovarian cancer, the most lethal tumor for women worldwide.     

QSAR study and VolSurf characterization of anti-HIV quinolone library

Antiviral quinolones are promising compounds in the search for new therapeutically effective agents for the treatment of AIDS. To rationalize the SAR for this new interesting class of anti-HIV derivatives, we performed a 3D-QSAR study on a library of 101 6-fluoro and 6-desfluoroquinolones, taken either from the literature or synthesized by us. The chemometric procedure involved a fully semiempirical minimization of the molecular structures by the AMSOL program, which takes into account the solvatation effect, and their 3D characterization by the VolSurf/GRID program. The QSAR analysis, based on PCA and PLS methods, shows the key structural features responsible for the antiviral activity.     

A note on the sum of uniform random variables

An inductive procedure is used to obtain distributions and probability densities for the sum S_n of independent, non-equally uniform random variables. Some known results are then shown to follow immediately as special cases. Under the assumption of equally uniform random variables some new formulas are obtained for probabilities and means related to S_n. Finally, some new recursive formulas involving distributions are derived.     

Penicillin G acylase as chiral selector in CE using a pullulan-coated capillary

In the present study, penicillin G acylase (PGA), an enzyme belonging to the family of hydrolases, has been investigated as chiral selector in CE using the partial filling technique. Owing to the strong disposition of PGA to be adsorbed by the inner capillary wall, permanently coated capillaries were used to diminish both the protein-wall interactions and the EOF. In particular, the silica surface of the capillary was chemically coated by an antiadhesive and an hydrophilic layer of pullulan, a high-molecular-mass homopolysaccharide. The coating procedure consisted in the silanization with glycidoxypropyltrimethoxysilane and the subsequent coupling of the hydroxyl groups of pullulan onto the silanized capillary. Using this approach, a significant EOF suppression was obtained within a wide pH range (pH 3.0-9.0); this result was very important in order to find the suitable conditions for the application of partial filling technique. The optimization of partial filling was carried out by considering the effects of different experimental conditions (buffer pH, PGA concentration, and loading duration), on the migration time and enantioresolution of rac-ketoprofen. Under the selected conditions as: 100 mM sodium phosphate buffer (pH 5.5) containing 240 microM of PGA (partial filling of 120 s at a pressure of 50 mbar), a series of acidic compounds resulted to be enantioresolved in about 10 min. The long-term stability of the proposed coating was evaluated; more than 100 injections were performed without significant loss of reproducibility.     

Comparative analysis of the oil and supercritical CO(2) extract of Cymbopogon citratus Stapf

Dried and ground leaves of lemon grass (Cymbopogon citratus Stapf.) were used as a matrix for supercritical extraction of essential oil with CO(2). The objective of this study was to analyze the influence of pressure on the supercritical extraction. A series of experiments were carried out, for 360 min, at 50 degrees C and at different pressures: 90, 100, 110 and 120 bar. Extraction conditions were chosen to maximize citral content in the extract oil. The collected extracts were analysed by GC-MS and their composition was compared with that of the essential oil isolated by hydrodistillation and by steam distillation. At higher solvent density the extract aspect changes passing from a characteristic yellow essential oil to yellowish semi-solid mass because of the extraction of high molecular mass compounds. The optimum conditions for citral extraction were 90 bar and 50 degrees C, at these conditions citral represent more than 68% of the essential oil and the extraction yield was 0.65% while the yield obtained from hydrodistillation was 0.43% with a content of citral of 73%.     

Condensation of substituted 2-aminopyridine with β-ketocarboxylic esters: 4H-pyrido[1,2-a]pyrimidin-4-ones and pyridin-2-ones

We report the condensation of substituted 2-aminopyridines 5 with β-ketocarboxylic esters in polyphosphoric acid. In this reaction were obtained together with the target compounds, 4H-pyrido[1,2-a]pyrirnidin-4-ones 6 also the pyridin-2-ones 7 . All the compounds 7 were tested for their calcium-antagonistic activity but failed to evoke any vasorelaxant response.     

Micro computed tomography based finite element models for elastic and strength properties of 3D printed glass scaffolds

Acta Mechanica Sinica - In this study, the mechanical properties of glass scaffolds manufactured by robocasting are investigated through micro computed tomography ( $$\mu -CT$$ ) based finite...     

Photoactive Ru Complex Embedded in Mesostructured MCM-41 Nanoparticles

The synthesis and characterization of photoactive hybrid materials based on [Ru(bpy)₃]²⁺ physically adsorbed within the channels of mesoporous MCM-41 silica nanoparticles is presented. A set of photoactive mesostructured hybrids with different guest loading has been prepared and characterized by X-ray diffraction, High Resolution Transmission Electron Microscopy, volumetric analyses, Diffuse Reflectance UV-Vis and Photoluminescence spectroscopies and lifetime measurements. The hybrids synthesis and the washing procedures, performed to investigate the host-guest interaction and the stability of the complex within the mesopores, didn??t affect the integrity of the structure and morphology of MCM-41 nanoparticles. The dispersion of [Ru(bpy)₃]²⁺ within the channels varied depending on the loading value and this is reflected in the different and peculiar photoluminescence features of the resulting hybrid materials. Photoluminescence spectroscopy evidenced that the use of MCM-41 nanoparticles ensures a better dispersion of the complex within the mesopores, if compared with traditional MCM-41. Further studies are in progress to investigate the interesting and promising features exhibited by such photoactive systems for advanced applications of electrochemiluminescence in optoelectronics and diagnostics.