Microwave Assisted Digestion Method for the Determination of Cadmium,Copper, Lead,and Zinc in Biological Materials

Anodic stripping voltammetry is useful instrumental method for trace element determination in biological materials. It is however extremely demanding to the quality of the sample preparation process. The high‐pressure microwave assisted digestion seems to meet its requirements. The differential pulse anodic stripping voltammetry technique was used for determination of cadmium, copper, lead and zinc in certified reference materials both of plant and of animal origin to prove the analytical properties of such sample preparation method. The found concentrations have been in satisfactory agreement with the certified values. The elaborated digestion procedure is greatly universal and has required accuracy and precision.     

Theoretical study of the oxidative polymerization of aniline with peroxydisulfate: Tetramer formation

Semi‐empirical quantum chemical study of the oxidative polymerization of aniline with ammonium peroxydisulfate, in aqueous solutions without added acid, has been based on the MNDO‐PM3 computations of thermodynamic, redox, and acid–base properties of reactive species and the intermediates, combined with the MM2 molecular mechanics force‐field method and conductor‐like screening model of solvation. The main reaction routes of aniline tetramerization are proposed. The regioselectivity of the formation of aniline tetramers by redox and electrophilic aromatic substitution reactions is analyzed. It was proved that the linear N? C4 coupled tetra‐aniline is formed as a dominant product by three different pathways: comproportionation redox reaction between N‐phenyl‐1,4‐benzoquinonediimine and 4‐aminodiphenylamine, the one‐electron oxidation of aniline with its half‐oxidized N? C4 coupled trimer, and the electrophilic aromatic substitution reaction of aniline with fully oxidized N? C4 coupled trianiline nitrenium cation. The electrophilic aromatic substitution reaction of the N? C4 coupled aniline trimer with aniline nitrenium cation, as well as the oxidation of aniline with half‐oxidized branched trimer, lead to the branched aniline tetramers. The competing character of different tetramerization routes is highlighted. The oxidative intramolecular cyclization of branched oligoanilines and polyaniline, leading to the generation of substituted phenazine units, has been predicted to accompany the classical routes of the polymerization of aniline. Various molecular (branched vs. linear) oligomeric structures produced at different level of acidity during the course of polymerization and their impact on the formation of supramolecular structures of conducting polyaniline (nanorods and nanotubes vs. granular morphology), are discussed. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Preparative separation of immunoglobulins from bovine colostrum by continuous divergent-flow electrophoresis

Immunoglobulins in bovine colostrum were separated and fractionated from other proteins using the method and instrumentation developed in our laboratory. The proposed separation was based on bidirectional isotachophoresis/moving boundary electrophoresis with electrofocusing of the analytes in a pH gradient from 3.9 to 10.1. The preparative instrumentation included the trapezoidal non-woven fabric that served as separation space with divergent continuous flow. The defatted and casein precipitate-free colostrum supernatant was loaded directly into the instrument without any additional colostrum pre-preparation. Immunoglobulin G was fractionated from other immune proteins such as bovine serum albumin, β-lactoglobulin, and α-lactalbumin, and was continuously collected in separated fractions over 3 h. The fractions were further processed, and isolated immunoglobulin G in the liquid fractions was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by re-focusing in gel isoelectric focusing. Separated immunoglobulin G was detected in seven fractions by sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a gradually decreased concentration in the fractions. Re-focusing of the proteins in the fractions by gel isoelectric focusing revealed multiple separated zones of immunoglobulin G with the isoelectric point values covering the range from 5.4 to 7.2. Each fraction contained distinct zones with gradually increased isoelectric point values and decreased concentrations from fraction to fraction.     

Simultaneous analysis of polar and non-polar components of cell membrane phospholipids by GC-MS

A rapid and selective GC-MS method was optimised for the simultaneous analysis of fatty acids, phosphoethanolamine, phosphoglycerol and phosphoserine, which comprise the polar headgroups of phospholipids. Enzymatic hydrolysis was used for sample preparation to selectively release fatty acids and prevent cleavage of the phosphoester bonds of the polar headgroups. A two-step consecutive derivatisation of the fatty acids and polar headgroups was applied to enable the simultaneous analysis of the selected analytes. The method was tested on samples of cell membrane phospholipids of Bacillus subtilis, a microbe with a broad spectrum of fatty acids. This approach can accelerate and simplify biotechnological research and quality control. The experimental conditions were optimised using a chemometric approach denoted as experimental design.     

SOD mimetic activity of salicylatocopper complexes

Investigation of salicylatocopper complexes in the presence of a nitrogen donor ligand is a growing research area due to the interesting mimetic activities of such complexes. Here, three X-salicylatocopper (where X = 3-methyl, or 4-methoxy) complexes with three different N-donor ligands, [Cu(μ-menia)(3-Mesal)₂(menia)(H₂O)]₂ (I), Cu(3-Mesal)₂(denia)₂(H₂O)₂ (II), Cu(4-MeOsal)₂(2-pyme)₂ (III), are presented (where 3-Mesal = 3-methysalicylate, 4-MeOsal = 4-methoxysalicylate, menia = N-methylnicotinamide, 2-pyme = 2-pyridylmethanol). The complexes were characterized by elemental analysis, IR and UV-VIS spectrophotometry. Cyclic voltammetry and the superoxide dismutase activity of the prepared complexes in solution were measured and the complexes were characterized by means of the inhibition concentration IC₅₀. In addition, the superoxide dismutase (SOD) activity of these complexes was compared with those of the parent ligand copper acetate, native SOD enzyme, and the related copper complexes containing non-steroidal anti-inflammatory drugs. The resulting SOD activity was correlated to the composition, structure and redox stability of the prepared complexes. The best value of the inhibition concentration was found for complex I (IC₅₀ = 2.24 µM), which classifies this complex into a group of good superoxide scavengers.     

Voltammetric determination of aminobiphenyls at a boron-doped nanocrystalline diamond film electrode

Voltammetric behavior of 2-aminobiphenyl, 3-aminobiphenyl, and 4-aminobiphenyl at a boron-doped nanocrystalline diamond film electrode was investigated using cyclic voltammetry and differential pulse voltammetry. Optimum conditions have been found for the determination of those genotoxic substances by differential pulse voltammetry at the above given electrode in the concentration range of 2 × 10⁻⁷ to 1 × 10⁻⁵ mol/L.     

Multi-component hybrid inorganic–organic–inorganic particles with various metal oxide outer shells

Non-agglomerated hybrid particles of 200 nm diameter with an outer metal oxide shell were prepared by reacting the COOH groups of poly((S)-N-dicarbazolyl-lysine)-covered silica particles with metal alkoxides, such as titanium, zirconium and aluminum alkoxides, followed by sol–gel processing. With tetraethoxysilane (Si(OEt)₄), the silica particle core was growing rather than forming an external metal oxide shell, as observed for the other tested metal alkoxides.     

Ultraviolet B light stimulates interleukin-20 expression by human epithelial keratinocytes

The proinflammatory cytokine interleukin-20 (IL-20) may exert the majority of its activity in the skin. We examined the effect of various treatments including several forms of phototherapy on IL-20 expression using cultured normal human epithelial keratinocytes (NHEK). Broadband UVB light, recombinant (r) IL-1 and rIL-8 increased, while hydrocortisone reduced, NHEK supernatant IL-20 levels. Elevation of NHEK IL-20 mRNA and maximal supernatant IL-20 levels occurred with a UVB light dose (40 mJ cm(-2)) that reduced cell viability by approximately 50%. While this UVB light dose also elevated supernatant IL-1 alpha and IL-8 levels, antibody neutralization studies indicated that neither of these cytokines was directly responsible for this increase in IL-20 expression. However, the elevation in IL-20 levels was fully inhibited by the p38 mitogen-activated protein kinase (MAPK) inhibitor SB-203580, suggesting involvement of this stress signaling pathway in this UVB light response. Photodynamic therapy (PDT) with the photosensitizer lemuteporfin, UVA light, cisplatin, lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha) or recombinant interferon-gamma (rIFN-gamma) either had little effect or decreased NHEK supernatant IL-20 levels. Reduced IL-20 levels paralleled the cytotoxic actions of PDT, UVA light or cisplatin and the antiproliferative effect of rIFN-gamma. Neither rIL-20 supplementation nor anti-IL-20 antibody treatments affected cell viability indicating that soluble IL-20 did not affect the short-term survival of UVB light-irradiated NHEK. Stimulation of IL-20 expression in keratinocytes by UVB light suggests that this cytokine might participate in skin responses to this ever-present environmental factor and potentially has a role in UV light-associated dermatoses.     

Solvent activity changes and phase separation during crosslinking of coating films

Changes in solvent activity and thermodynamic stability of a system undergoing crosslinking in the presence of a solvent are modeled by combination of branching theory with thermodynamics of polymer solutions and swelling of a crosslinked polymer. The system is considered as a quasiternary one in which the solvent, polydisperse soluble polymer (sol) and crosslinked network, respectively, represent the components. Crosslinking brings about growth of polymer structures but also changes in polymer-solvent interactions. The results are compared with onset of phase separation and changes in evaporation rates from films formed from a hydroxy-functional star oligomer and triisocyanate.