Marian Zaborski

Electrooxidation of flavonoids at platinum electrode studied by cyclic voltammetry

Flavonoids are natural vegetable dyes synthesized from phenylalanine. They are responsible for colour of blooming plant portions. Moreover, they are very important for human health due to their activity as free radical acceptors. Cyclic and differential pulse voltammetry was used in the determination of kinetic parameters of flavonoids electrooxidation. Electrochemical measurements of the oxidation of organic compounds can be helpful in understanding how these compounds are metabolised by living organisms. Flavonoids electrochemical oxidation is an irreversible reaction at a platinum electrode. In the case of morin hydrate, rutin, dihydroxyflavone, trihydroxyflavone, hesperidin, quercetin, the first step of the electrooxidation includes an exchange of two electrons during the oxidation of hydroxyl groups in the ring B. Hydroxyl groups in the rings A and C are probably oxidised in subsequent steps. The heterogeneous rate constants (k(bh)) determined for the flavonoids electrooxidation are as follows: morin - 3.59×10(-4), rutin - 4.42×10(-4), dihydroxyflavone - 4.54×10(-4), trihydroxyflavone - 4.19×10(-4), hesperidin - 4.50×10(-4) and quercetin - 4.63×10(-4)cms(-1). Their anodic transition coefficient ranged from 0.63 to 0.48 (n=2). Xanthone and flavone were oxidised easiest and quickest among other substrates at the platinum electrode with the heterogeneous rate constants (k(bh)) of 7.08×10(-4) and 6.46×10(-4)cms(-1), respectively.

Characterization of complexes formed by polypropylene imine dendrimers and anti-HIV oligonucleotides

Current anti-HIV therapies are capable of controlling viral infection but do not represent a definitive cure. They rely on the administration of antiretroviral nucleoside analogues, either alone or in combination with vectors. Dendrimers are branched, synthetic polymers with layered architectures, promising non-viral vectors in gene therapy. The aim of the paper was to study the interactions between three anti-HIV antisense oligonucleotides (ODNs): SREV, ANTI TAR, GEM91 and different generation polypropylene imine dendrimers (PPI) by monitoring changes in the fluorescence polarization of fluorescein attached to the ends of the ODNs when increasing concentrations of dendrimers were added. Laser Doppler electrophoresis, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to characterize, respectively, zeta potential, particle size and morphology of dendriplexes formed in different molar ratios. Antisense oligonucleotides interacted with polypropylene imine dendrimers in different molar ratios depending on generation. Zeta potential of dendriplexes varied from (-25 to -21) mV to -5 mV (for PPIG3 and PPIG4 complexes) and to zero (for PPIG2 complexes). The structures presented a polydisperse size from about 50 nm to even 700-800 nm by TEM and about 250 nm by DLS. It means that besides single dendriplexes, aggregates were also present.

Carbosilane dendrimers NN8 and NN16 form a stable complex with siGAG1.

A new mechanism of gene expression inhibition has been discovered as RNA interference, in which the ability of double-stranded RNA to stimulate specific degradation of an mRNA target with a complementary sequence to one of the double-stranded RNA strands. Water-soluble carbosilane dendrimers containing ammonium or amine groups at their periphery are biocompatible molecules that may be good candidates as non-viral carriers of small interfering RNA. In studying the formation of complex between anti-HIV siRNA siGAG1 and carbosilane dendrimers NN8 and NN16 by circular dichroism, fluorescence, and zeta-potential, the size of nanoparticles formed has been estimated by dynamic light scattering. At a charge ratio of 1:3-4 (siGAG1:dendrimer), the dendriplexes formed were in the size range of 250-350 nm.

Surface properties of zinc oxide nanoparticles studied by inverse gas chromatography.

Inverse gas chromatography (IGC) was applied in infinite dilution to evaluate the surface properties of zinc oxide nanoparticles with respect to their specific surface area, particle size and morphology (spherical, whiskers, and snowflakes). The dispersive components (gamma(S)(D)) of the free energy of zinc oxides were determined by Grays method, whereas their tendency to undergo specific interactions was estimated based on the electron donor-acceptor approach presented by Papirer. The zinc oxide nanoparticles exhibited high surface energies that were dependent on their morphology. The highest value of gamma(S)(D) was determined for spherical zinc oxide particles with high specific surface area, which had the most structure defects. The specific interactions were characterized by the energy (DeltaG(A)(SP)) and enthalpy (DeltaH(A)(SP)) of adsorption as well as the donor and acceptor interaction parameters (K(A), K(D)).

Characteristics of compounds in hops using cyclic voltammetry, UV-VIS, FTIR and GC-MS analysis

The article presents the antioxidant properties of the extracts of hop EI and EII, by the electrochemical methods on a platinum electrode and comparative analysis of the composition of the extracts of hops using UV-VIS, FTIR and GC-MS methods. The hops extract EI, was obtained from the waste of the hops cone. The hops extract EII, was obtained from the hops cone itself. Hops contain a wide range of polyphenolic compounds with antioxidant properties divided in various chemical classes. Flavonoids and other polyphenolic compounds contained in hops show antioxidant capacity because of the presence of hydroxyl groups in various configurations and numbers within their molecules. The electrochemical properties and antioxidant capacity of hop samples were determined to select the most effective antioxidant. Based on the cyclic and pulse voltammograms, it was observed that hop extract EI contains polyphenols that are oxidised at a less positive potential than extract EII, i.e., it shows better antioxidant capacity. From the analysis of the UV-VIS and FTIR spectra and the GC-MS analysis, it was observed that extract EI contains less phenyl compounds than EII. In addition to flavonoids, EII contains hop acids and chlorophyll. The solutions of hop extracts show very good antioxidant capacities; therefore, they can effectively inhibit or slow negative oxidation reactions and scavenge free radicals and reactive oxygen species (ROS).

Synthesis and dissolving power of 1-Alkyl-3-methylpyridinium-based ionic liquids

Abstract1-Alkyl-3-methylpyridinium-based ionic liquids with substituents from C2 to C10 and anions Cl− and Br− were synthesized, and their dissolving power toward the cellulose was investigated. The results of quantum-chemical calculations of molecules of ionic liquids are presented.

Highly Organized Self-Assembled Dendriplexes Based on Poly(propylene imine) Glycodendrimer and Anti-HIV Oligodeoxynucleotides

Dendrimers are artificial polymeric macromolecules which are widely considered to be a promising tool for future gene therapy applications. They have been used as efficient delivery vehicles for antisense oligonucleotides targeting the interior of cells. We demonstrate that dendriplexes formed from anti-HIV oligodeoxynucleotides ANTI-TAR, GEM91, and SREV in complex with generation 4 maltose (PPI-Mal G4) and maltotriose (PPI-Mal-III G4) modified poly(propylene imine) dendrimers are able to self-assemble into highly organized 1D and 3D nanostructures. The resulting nanostructures were characterized by fluorescence methods, laser Doppler electrophoresis, dynamic light scattering (DLS), atomic force microscopy (AFM) and molecular modeling. The results show that ANTI-TAR and GEM 91 dendriplexes self-assemble into fibrils with length scales up to several hundreds of nm. SREV, on the contrary, forms quadrilateral- like 3D nanostructures. A good correlation between the various experimental methods and molecular modeling indicates the formation of those nanostructures in solution. Space symmetry of the oligonucleotides and the resulting dendriplex monomeric units are probably the most important factors which influence the way of self-assembling.

Biodegradable protein-containing elastomeric vulcanizates

Abstract The effects of leather powders, chrome tanned leather powders and keratin were studied on properties of the synthetic isoprene rubber IR and the microbiological decomposition of the result...

Surface properties of calcium and magnesium oxide nanopowders grafted with unsaturated carboxylic acids studied with inverse gas chromatography.

Inverse gas chromatography (IGC) was applied at infinite dilution to evaluate the surface properties of calcium and magnesium oxide nanoparticles and the effect of surface grafted unsaturated carboxylic acid on the nanopowder donor-acceptor characteristics. The dispersive components (γ(s)(D)) of the free energy of the nanopowders were determined by Grays method, whereas their tendency to undergo specific interactions was estimated based on the electron donor-acceptor approach presented by Papirer. The calcium and magnesium oxide nanoparticles exhibited high surface energies (79 mJ/m² and 74 mJ/m², respectively). Modification of nanopowders with unsaturated carboxylic acids decreased their specific adsorption energy. The lowest value of γ(s)(D) was determined for nanopowders grafted with undecylenic acid, approximately 55 mJ/m². The specific interactions were characterised by the molar free energy (ΔG(A)(SP)) and molar enthalpy (ΔH(A)(SP)) of adsorption as well as the donor and acceptor interaction parameters (K(A), K(D)).

Hydroxyapatite: An Environmentally Friendly Filler for Elastomers

Natural hydroxyapatite HAP, extracted from the animal bones was used as filler for carboxylated acrylonitrile-butadiene rubber XNBR. Physicochemical properties of the HAP were investigated. It demonstrated the tendency to create the structure in paraffin oil. When added to rubber, HAP formed a molecular filler network, which was observed from the dynamical mechanical analysis. Hydroxyapatite appeared to be active filler, since mechanical properties of the vulcanizates were improved upon filling. However, the dispersive component of the hydroxyapatite surface energy was slightly higher in comparison to the value which corresponds to the rubber.