Effects of the physicochemical properties of titanium dioxide nanoparticles, commonly used as sun protection agents, on microvascular endothelial cells

Until now, the potential effects of titanium dioxide (TiO₂) nanoparticles on endothelial cells are not well understood, despite their already wide usage. Therefore, the present work characterizes six TiO₂ nanoparticle samples in the size range of 19 × 17 to 87 × 13 nm, which are commonly present in sun protection agents with respect to their physicochemical properties (size, shape, ζ-potential, agglomeration, sedimentation, surface coating, and surface area), their interactions with serum proteins and biological impact on human microvascular endothelial cells (relative cellular dehydrogenase activity, adenosine triphosphate content, and monocyte chemoattractant protein-1 release). We observed no association of nanoparticle morphology with the agglomeration and sedimentation behavior and no variations of the ζ-potential (?14 to ?19 mV) in dependence on the surface coating. In general, the impact on endothelial cells was low and only detectable at concentrations of 100 μg/ml. Particles containing a rutile core and having rod-like shape had a stronger effect on cell metabolism than those with anatase core and elliptical shape (relative cellular dehydrogenase activity after 72 h: 60 vs. 90 %). Besides the morphology, the nanoparticle shell constitution was found to influence the metabolic activity of the cells. Upon cellular uptake, the nanoparticles were localized perinuclearly. Considering that in the in vivo situation endothelial cells would come in contact with considerably lower nanoparticle amounts than the lowest-observable adverse effects level (100 μg/ml), TiO₂ nanoparticles can be considered as rather harmless to humans under the investigated conditions.     

Raman scattering investigation of selenomethionine replacement in protein SOUL crystals

The vibrational properties of both wild‐type and selenomethionine (SeMet)‐substituted protein SOUL crystals have been investigated here by Raman spectroscopy. Several Raman peaks observed in the spectra of methionine and SeMet were identified as specific markers. The unambiguous assignment of these peaks has been inferred by comparing the experimental Raman spectra of the pure amino acids, recorded in solid state and in aqueous solution, and the Raman intensities computed using quantum chemical calculations. Moreover, a quantitative evaluation of the relative amount of SeMet replacement in the crystals of protein SOUL labelled with SeMet has been estimated through the ratio between the Raman intensities of marker peaks. These results offer evidence of the potential of Raman microscopy as a reliable and non‐invasive tool for novel in‐depth structural investigations in biocrystallography. Copyright © 2009 John Wiley & Sons, Ltd.     

Fragment-based QSAR: perspectives in drug design

Drug design is a process driven by innovation and technological breakthroughs involving a combination of advanced experimental and computational methods. A broad variety of medicinal chemistry approaches can be used for the identification of hits, generation of leads, as well as to accelerate the optimization of leads into drug candidates. Quantitative structure–activity relationship (QSAR) methods are among the most important strategies that can be applied for the successful design of small molecule modulators having clinical utility. Hologram QSAR (HQSAR) is a modern 2D fragment-based QSAR method that employs specialized molecular fingerprints. HQSAR can be applied to large data sets of compounds, as well as traditional-size sets, being a versatile tool in drug design. The HQSAR approach has evolved from a classical use in the generation of standard QSAR models for data correlation and prediction into advanced drug design tools for virtual screening and pharmacokinetic property prediction. This paper provides a brief perspective on the evolution and current status of HQSAR, highlighting present challenges and new opportunities in drug design.     

Production of Cellulolytic Enzymes by <Emphasis Type="Italic">Aspergillus phoenicis</Emphasis> in Grape Waste using Response Surface Methodology

The production of cellulolytic enzymes by the fungus Aspergillus phoenicis was investigated. Grape waste from the winemaking industry was chosen as the growth substrate among several agro-industrial byproducts. A 2 × 2 central composite design was performed, utilizing the amount of grape waste and peptone as independent variables. The fungus was cultivated in submerged fermentation at 30 °C and 120 rpm for 120 h, and the activities of total cellulases, endoglucanases, and β-glucosidases were measured. Total cellulases were positively influenced by the linear increase of peptone concentration and decrease at axial concentrations of grape waste and peptone. Maximum activity of endoglucanase was observed by a linear increase of both grape waste and peptone concentrations. Concentrations of grape waste between 5 and 15 g/L had a positive effect on the production of β-glucosidase; peptone had no significant effects. The optimum production of the three cellulolytic activities was observed at values near the central point. A. phoenicis has the potential for the production of cellulases utilizing grape waste as the growth substrate.     

MSPD Procedure for Determination of Carbofuran, Pyrimethanil and Tetraconazole Residues in Banana by GC–MS

An extraction method based on matrix solid-phase dispersion was developed to determine carbofuran, pyrimethanil and tetraconazole in banana using gas chromatography–mass spectrometry. The best results were obtained using 2.0 g of banana, 1.0 g of silica as dispersant sorbent and n-hexane:ethyl acetate (1:4, v/v) as eluting solvent. The method was validated using banana samples fortified with pesticides at different concentration levels (0.05–2.0 mg kg^?1). Average recoveries (four replicates) ranged from 68 to 111%, with relative standard deviations between 6.6 and 20.5%. Detection and quantification limits for banana ranged from 0.02 to 0.05 and 0.05 to 0.10 mg kg^?1, respectively.     

Modified Carbon Paste Electrode for Kinetic Investigation and Simultaneous Determination of Ascorbic and Uric Acids

The present work explores, for the first time, the electrocatalytic oxidation of ascorbic acid (AscH₂) and its determination in the presence of uric acid (UA) on the in situ activated 4‐nitrophthalonitrile modified carbon paste electrode. The kinetic constant κ for the catalytic reaction for the electrocatalytic oxidation of ascorbic acid, evaluated by cyclic voltammetry, chronoamperometry and RDE voltammetry provided values around 10⁶ L mol^?1 s^?1. The sensor provided a linear response range for AscH₂ and UA from 5.0 up to 120.0 μmol L^?1 with detection limits of 1.6 μmol L^?1and 1.3 μmol L^?1, respectively. The sensor was applied for the simultaneous determination of AscH₂ and UA in urine samples and the average recoveries for these samples were 99.8 (±3.1)% and 99.9 (±2.1)%, respectively .