Enzymatic Reaction Coupled with Flow-Injection Analysis with Charged Aerosol,Coulometric, or Amperometric Detection for Estimation of Contamination of the Environment by Pesticides

Because excessive using of pesticides poses a threat to the environment and to human health, development of low-cost and sensitive methods for analysis of pesticides in the environment is needed. Several bacteria can release halide ions from the molecules of halogenated hydrocarbons. This can be used in a device for analysis of halogenated hydrocarbons in the environment by quantification of the halide anions. Here we directed our attention to selecting an instrument for detection of chloride anions. We tested three different detectors, amperometric, and coulometric, both coupled with flow-injection analysis and charged aerosol, coupled with high performance liquid chromatography. Detection limits (3 × S/N) for measurement of chloride anions by use of these detectors was 30 μM (charged aerosol), 100 nM (coulometric), and 1 nM (amperometric). Because of its lowest detection limit for chloride anions and the many technical possibilities of miniaturization, the amperometric detector was used to test of effect of different cations on the chloride signal under the optimized experimental conditions (working electrode potential −365 mV; “Current R” 5 μA; mobile phase 0.2 M phosphate buffer, pH 6; flow rate 0.5 mL min⁻¹). NaCl, SrCl₂, NH₄Cl, and CsCl were tested as sources of chloride anions. We then used the detector to detect chloride anions catalytically cleaved from 1-chlorohexane by the enzyme haloalkane dehalogenase LinB from the bacterium Sphingobium japonicum UT26. The activity of the enzyme increased with increasing reaction temperature until the maximum was observed at 39°C. The results obtained were in good agreement with data obtained by colorimetric detection.

     

The preparation of conducting polyaniline�Csilver and poly(p-phenylenediamine)�Csilver nanocomposites in liquid and frozen reaction mixtures

The oxidation of aniline with silver nitrate in 1?mol?L^?1 acetic acid at 20?°C yielded a composite of two conducting components, polyaniline and silver; the acceleration with 1?mol% of p-phenylenediamine is needed for efficient synthesis. The yield and molecular weight increased when aniline was copolymerized with 10?mol% p-phenylenediamine. Such product displayed metallic conductivity below 180?K and semiconductor type above this temperature. As the result, the conductivity was the same at 100 and 300?K. The oxidation of p-phenylenediamine alone with silver nitrate also produced a conducting composite having the conductivity of 1,750?S cm^?1 despite the assumed nonconductivity of poly(p-phenylenediamine). The present study demonstrates that all oxidations proceeded also in frozen reaction mixtures at ?24?°C, i.e., in the solid state. In most cases, molecular weights of polymer component increased, the conductivity of composites with silver improved, to 2,990?S?cm^?1 for poly(p-phenylenediamine)?Csilver, and remained high after deprotonation with 1?mol?L^?1 ammonium hydroxide.     

The conversion of polyaniline nanotubes to nitrogen-containing carbon nanotubes and their comparison with multi-walled carbon nanotubes

Polyaniline (PANI) nanotubes were prepared by the oxidation of aniline in solutions of acetic or succinic acid, and subsequently carbonized in a nitrogen atmosphere during thermogravimetric analysis running up to 830 °C. The nanotubular morphology of PANI was preserved after carbonization. The molecular structure of the original PANI and of the carbonized products has been analyzed by FTIR and Raman spectroscopies. Carbonized PANI nanotubes contained about 8 wt.% of nitrogen. The molecular structure, thermal stability, and morphology of carbonized PANI nanotubes were compared with the properties of commercial multi-walled carbon nanotubes.     

The stability of polyaniline in strongly alkaline or acidic aqueous media

Polyaniline (PANI) base has been suspended in 9 M potassium hydroxide at 20 °C or 90 °C for various time intervals extending to 4 months. The fraction of acetone-soluble material increased from 1.2 wt.% to 4.5 wt.% after exposure to an alkaline medium for 60 days at 20 °C. Gel-permeation chromatography indicates that the aggregation of PANI is reduced, while the chain degradation itself is negligible. FTIR spectroscopy confirms this trend and the absence of hydrolytic changes in the PANI structure. Polyaniline retains the ability to be reprotonated with a 1 M sulfuric acid to a conducting form. No marked changes in the molecular structure have been found, even after suspension of PANI in 9 M KOH at 90 °C for 60 days.Similar immersion of PANI salt in 5 M sulfuric acid at 20 °C was responsible for changes in the protonation, and the mass increased by 11 wt.%. This was explained by the exchange of the original sulfate or chloride counter-ions for hydrogen sulfate anions or by the protonation of secondary amine sites in PANI in addition to imine ones. The changes in the molecular structure are discussed on the basis of FTIR spectra. The conductivity decreased from 1.2 S cm⁻¹ to ∼10⁻³ S cm⁻¹ but no time-dependence of conductivity was observed. There was no fraction of PANI soluble in acetone. PANI in the protonated state is thus stable also in the strongly acidic medium.The study is supplemented by the assessment of the thermal stability of PANI base, which is of importance for the processing of PANI. Loss of moisture has been observed after exposure to 250 °C for 10 h in both nitrogen atmosphere and in air. Good stability was found at 350 °C only in the nitrogen atmosphere, while a marked mass loss in weight was registered in air.     

Influence of selected biowaste materials pre-treatment on their anaerobic digestion

The topic of this study is the pre-treatment of substrates for anaerobic digestion. Two different substrates of algae Scenedesmus subspicatus (SAG 86.81), Chlorella kessleri (LARG/1) and foliage of Prunus serrulata were subjected to anaerobic digestion. A mixture of commercially available cellulolytic enzymes (Analytical science s.r.o., Modra, Slovakia) was used for anaerobic treatment of algae while the foliage of Prunus serrulata was pre-treated by lignolytic fungi. The highest production of methane per mass of volatile solids was reached with untreated Chlorella kessleri at (0.59 ± 0.04) L g⁻¹. The addition of cellulolytic enzymes did not increase the production of methane from the algal substrate; however, a faster substrate degradation and thus also higher speed of methane production at the beginning of cultivation was achieved. After foliage pre-treatment by fungal isolate Pleurotus pulmonarius, isolated from natural habitats, the methane production increased five times. In this way we were able to speed up the processes of biological degradation of ligno-cellulose materials and thereby to increase the production of methane. Our results show the possibility of using algae as a suitable substrate for biogas production. On the other hand, also aerobic pre-treatment of foliage (Pleurotus pulmonarius) presents a successful way for speeding up the degradation of ligno-cellulose waste leading to increased methane yields.     

The effects on soil/water/plant/animal systems by platinum group elements

Emissions of toxic substances such as oxides of carbon, nitrogen, sulphur, and, in addition, aromatic hydrocarbons, aldehydes and heavy metals are the most serious problem of road traffic affecting landscape. Platinum group elements (PGE), which are the main component of the catalyst, are one of the main sources of heavy metals in the environment. Here, we review the way by which emissions and forms of the emitted PGE end up in the environment especially to the soil-water-plant-animal system. The major points discussed are the following: 1) the main sources of PGE emission are automobile exhaust catalysts; 2) hospitals, where platinum is widely used to treat malignant neoplasm, and urban waste water belonging to other important sources of PGE in the environment; 3) soil is one of the most important components of the environment that may be contaminated with platinum metals; 4) phytotoxicity of PGE depends on the following conditions: the concentration of metals in the soil, time of exposure, the chemical form of metal, the chemical composition of exposed soil and plant species; 5) animals are also endangered by the increasing concentration of PGE in the environment. Moreover, we pay our attention to thiol-based mechanisms of how an organism protects itself against platinum group elements.      

Coating of zinc ferrite particles with a conducting polymer, polyaniline

Particles of zinc ferrite, ZnOFe2O3, were coated with polyaniline (PANI) phosphate during the in situ polymerization of aniline in an aqueous solution of phosphoric acid. The PANI-ferrite composites were characterized by FTIR spectroscopy. X-ray photoelectron spectroscopy was used to determine the degree of coating with a conducting polymer. Even a low content of PANI, 1.4 wt%, resulted in the 45% coating of the particles' surface. On the other hand, even at high PANI content, the coating of ferrite surface did not exceeded 90%. This is explained by the clustering of hydrophobic aniline oligomers at the hydrophilic ferrite surface and the consequent irregular PANI coating. The conductivity increased from 2 x 10(-9) to 6.5 S cm(-1) with increasing fraction of PANI phosphate in the composite. The percolation threshold was located at 3-4 vol% of the conducting component. In the absence of any acid, a conducting product, 1.4 x 10(-2) Scm(-1), was also obtained. As the concentration of phosphoric acid increased to 3 M, the conductivity of the composites reached 1.8 S cm(-1) at 10-14 wt% of PANI. The ferrite alone can act as an oxidant for aniline; a product having a conductivity 0.11 S cm(-1) was obtained after a one-month immersion of ferrite in an acidic solution of aniline.     

On partially null and pseudo null curves in the semi-euclidean space R^{4}_{2}

In this paper, we obtain the Frenet equations of a pseudo null and a partially null curves, lying fully in the semi–Euclidean space , and classify all such curves with constant curvatures.     

DIFFERENTIAL EXPRESSION OF PYRIMIDINE DIMER-BINDING PROTEINS IN NORMAL AND UV LIGHT-TREATED VERTEBRATE CELLS

Abstract— The expression of UV damage-specific DNA-binding proteins was examined in various phylogenetically distant species with differing DNA repair phenotypes. Two distinct constitutive DNA-binding activities, one specific for cyclobutane pyrimidine dimers and the other for non-cyclobutane dimer photoproducts, were detected. The expression of these binding activity was found to be variable throughout the animal kingdom: cold-blooded vertebrastes show a constitutive cyclobutance dimer-binding activity excusively, and primates reveal only non-cyclobutane expression (rather than the constitutive presence)of these UV damage-specific DNA-binding activities after UV traeatment correlate with the cell's capacity for DNA repair. In addition, cyclobutane pyrimidine dimer-binding activities could be detected only in cells with eestablished photoreactivating activity     

REDUCED REPAIR OF NON-DIMER PHOTOPRODUCTS IN A GENE TRANSFECTED INTO XERODERMA PIGMENTOSUM CELLS

Abstract— 4ells from patients with the sun sensitive cancer-prone disease, xeroderma pigmentosum (XP) have defective repair of UV damaged DNA with reduced excision of the major photoproduct, the cyclobutane type pyrimidine dimer. Other (non-dimer) photoproducts, have recently been implicated in UV mutagenesis. Utilizing an expression vector host cell reactivation assay, we studied UV damaged transfecting DNA that was treated by in vitro photoreactivation to reverse pyrimidine dimers while not altering other photoproducts. We found that the reduced expression of a UV damaged transfecting plasmid in XP complementation group A cells is only partially reversed by photoreactivation. E. coli photolyase treatment of pSV2catSVgpt exposed to 100 or 200 J m⁻² of 254 nm radiation removed 99% of the T4 endonuclease V sensitive sites. Transfection of XP12BE(SV40) cells with photoreactivated pSV2catSVgpt showed residual inhibition corresponding to 25 to 37% of the lethal hits to the cat gene. This residual inhibition corresponds to the fraction of non-dimer photoproducts induced by UV. This result implies that XP12BE(SV40) cells do not repair most of the non-dimer photoproducts in DNA.