Oxidation of Sanguinarine and Its Dihydro‐Derivative at a Pyrolytic Graphite Electrode Using Ex Situ Voltammetry. Study of the Interactions of the Alkaloids with DNA

This study describes the oxidation of sanguinarine (SG) and its metabolite dihydrosanguinarine (DHSG) on the surface of a basal‐plane pyrolytic graphite electrode (PGE). Since both alkaloids strongly adsorb onto the surface of pyrolytic graphite, measurements were performed using ex situ voltammetric methods, adsorptive transfer (AdT) cyclic voltammetry (CV) and square‐wave voltammetry (SWV). Oxidation peaks of SG (peak A) and DHSG (peak A*) were observed around the potential of +0.7 V (vs. Ag/AgCl/3 M KCl), depending on the experimental conditions. The voltammetric peaks A and A* are probably related to the oxidation of N‐methylphenanthridine nitrogenous heterocycle of SG and oxidation of DHSG back to SG, respectively. The electrochemical results and optimized AdT SWV were subsequently applied to the study of the interactions of SG and DHSG with DNA in vitro. Analysis of the alkaloid/DNA interactions was based on observing heights of oxidation peaks A and A* after incubation of SG and/or DHSG with supercoiled (sc) DNA [pBSK_(?)]. Electrochemical study of the interactions was supported and complemented with measurements using gel electrophoresis (Topoisomerase I scDNA relaxation assay) and steady‐state and time‐resolved fluorescence spectroscopy. The results suggest that SG intercalates into the double‐stranded structure of scDNA (the SG/base pair ratio is max. 1/4) while increased binding affinity was observed for quaternary cation (SG⁺). DHSG which, unlike SG⁺, does not possess a strictly planar molecular structure, did not show intercalative DNA binding in any of the three methods applied.     

Measurement of the yields of positively charged particles at an angle of 35° in proton interactions with nuclear targets at an energy of 50 GeV

Momentum spectra of cumulative particles in the region of high transverse momenta (P _T ) in pA → h ⁺ + X reactions were obtained for the first time. The experiment in which this was done was performed at the SPIN setup (Institute for High Energy Physics, Protvino) in a beam of 50-GeV protons interacting with C, Al, Cu, and W nuclei. Positively charged particles were detected at a laboratory angle of 35° and in the transverse-momentum range between 0.6 and 3.7 GeV/c. A strong dependence of the particle-production cross section on the atomic number was observed. A comparison with the results of calculations based on the HIJING and UrQMD models was performed in the subcumulative region.     

Approaches to mathematical design of ballistic experiment: Part II

Mathematical expedients used in designing ground tests of aerodynamic object models with the aim of finding experimental conditions optimal in terms of the body and accuracy of extracted information are described. In the first part of this paper, the method used in designing the ballistic experiment is demonstrated with processing of single-experiment data. In the second part, the validity of the design approach is illustrated by simultaneously processing trajectory data obtained in several experiments.     

Conductivity,impurity profile,and cytotoxicity of solvent‐extracted polyaniline

Understanding the correlation between the preparation, purification, impurity leaching, and cytotoxicity of polyaniline is crucial for the application of this conducting polymer in biomedicine. Polyaniline hydrochloride was purified in a Soxhlet extractor by using six different solvents: methanol, 1,2‐dichloroethane, acetone, ethyl acetate, hexane, or 0.2 M aqueous hydrochloric acid. The chromatographic analyses of impurities leached out of the polymer into the solvents confirmed differences in impurity profiles, which depended on the polarity of the extraction solvent. Compared with the original polymer, the conductivity of purified polyanilines increased in dependence on the amount and type of extracted impurities. The cytotoxicity of purified samples determined on the mouse embryonic fibroblast cell line NIH/3T3 using MTT assay improved as well. Methanol and 0.2 M hydrochloric acid were the most efficient solvents capable of extracting low‐molecular‐weight impurities, and thus reducing polyaniline cytotoxicity. The absence of cytotoxicity was observed at an extract concentration of 10%. Extraction with suitable solvents can, therefore, be a possible way of obtaining cyto‐compatible polyaniline with sufficient conductivity. Copyright © 2015 John Wiley & Sons, Ltd.     

Evaluation of ammonium fluoride for quantitative microwave-assisted extraction of silicon and boron from different solid samples

A novel, simple, efficient and environmentally friendly closed-microwave-assisted extraction (MAE) method of silicon and boron from a variety of industrial and environmental samples using ammonium fluoride as an extractant was developed. This method avoids handling the corrosive and toxic HF and prevents the potential risk of analyte loss due to the creation of volatile SiF₄ and BF₃ in the presence of HF. Atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry were employed for the subsequent analysis of the resulting supernatant for determination of Si and B, respectively. Certified reference material BCR^®-032 Natural Moroccan Phosphate Rock (phosphate fertiliser) was taken to optimise the extraction parameters such as the sample amount, extraction temperature and time and the volume of the extractant. The optimum extraction parameters evaluated using a fractional factorial design were as follows: 50 mg of the sample extracted with 5 mL of 100 g L^?1 NH₄ F for 15 min at 180°C. The optimised MAE procedure was successfully applied to nine different matrix reference materials intended primarily for validation of methods for determination of components in fertilisers, sludge, plants and fly ash. The obtained results were in a good agreement with the certified or comparative values with an overall precision better than 10% in all cases. The proposed method is recommended for fast and reliable preparation of samples with silicon content <8.2% (w/w). However, further decreasing the sample mass to 10 mg enabled the quantitative extraction of silicon from fly ashes at levels of 23% (w/w).     

Physicochemical aspects of <Emphasis Type="Italic">Trichosporon cutaneum</Emphasis> CCY 30-5-10 adhesion and biofilm formation potential on cellophane

This paper focuses on the adhesion and biofilm formation potential of cellulolytic yeast Trichosporon cutaneum CCY 30-5-10 on solid cellophane from a novel perspective. First, physicochemical characterisation of the cells and carrier (cellophane) was performed to evaluate the effect of different culture media (complex vs mineral) on yeast cell adhesion. (Un)favourable adhesion conditions were predicted using the thermodynamic approach. Next, the ability of the cells to colonise the carrier under the above conditions was quantified and the biofilm structure was characterised using image analysis. The approaches described were found suitable to predict and experimentally verify favourable (cell-solid) adhesion, i.e. the hydrophobic and low electron-donor nature of cellophane together with hydrophobic cells (obtained when cultivated in a complex culture medium) were found to have a major impact in defining successful yeast adhesion with subsequent biofilm formation.     

The Phototoxic Potential of the Flavonoids,Taxifolin and Quercetin

Quercetin, one of the most abundant polyphenols in the plant kingdom has been shown to be photodegraded on exposure to UV light. Despite the fact, it is a component of several dermatological preparations. Its phototoxic potential has not been evaluated to date. The aim of this study was to assess whether photo‐induced degradation of quercetin is linked to phototoxic effects on living cells. Its dihydro derivative, taxifolin, was included in the study. For evaluation, the 3T3 Neutral Red Uptake Phototoxicity Test according to OECD TG 432 was used. To better approximate human skin, HaCaT keratinocytes, normal human epidermal keratinocytes and dermal fibroblasts were used, apart from the Balb/c 3T3 cell line. Quercetin showed a dose‐dependent photodegradation in aqueous and organic environments and a phototoxic effect on all used cells. Quercetin pretreatment and following UVA exposure resulted in increased reactive oxygen species production and intracellular glutathione level depletion in human dermal fibroblasts. Taxifolin was found completely nonphototoxic and photostable. As only in vitro methodology was used, further studies using 3D skin models and/or human volunteers are needed to confirm whether exposure to sunlight, tanning sunbeds and/or phototherapy in people using cosmetics containing quercetin is a health risk.     

SDDP for multistage stochastic programs: preprocessing via scenario reduction

Even with recent enhancements, computation times for large-scale multistage problems with risk-averse objective functions can be very long. Therefore, preprocessing via scenario reduction could be considered as a way to significantly improve the overall performance. Stage-wise backward reduction of single scenarios applied to a fixed branching structure of the tree is a promising tool for efficient algorithms like stochastic dual dynamic programming. We provide computational results which show an acceptable precision of the results for the reduced problem and a substantial decrease of the total computation time.     

Solid-state synthesis of undoped and Sr-doped K<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>NbO<Subscript>3</Subscript>

The solid-state synthesis of undoped K_0.5Na_0.5NbO₃ (KNN) and KNN doped with 1, 2 and 6 mol% Sr, from potassium, sodium and strontium carbonates with niobium pentoxide, was studied using thermal analysis and in situ high-temperature X-ray diffraction (HT-XRD). The thermogravimetry and the differential thermal analyses with evolved-gas analyses showed that the carbonates, which were previously reacted with the moisture in the air to form hydrogen carbonates, partly decomposed when heated to 200 °C. In the temperature interval where the reaction was observed, i.e., between 200 and 750 °C, all the samples exhibited the main mass loss in two steps. The first step starts at around 400 °C and finishes at 540 °C, and the second step has an onset at 540 °C and finishes with the end of the reaction between 630 and 675 °C, depending on the particle size distribution of the Nb₂O₅ precursor. According to the HT-XRD analysis, the perovskite phase is formed at 450 °C for all the samples, regardless of the Sr content. The formation of a polyniobate phase with a tetragonal tungsten bronze structure was detected by HT-XRD in the KNN with the largest amount of Sr dopant, i.e., 6 mol% of Sr, at 600 °C.