The Impact of Zeta Potential and Physicochemical Properties of TiO2‐Based Nanocomposites on Their Biological Activity

The aim of this research was to observe the relationship between zeta potential, morphology, surface area, porosity, chemical composition, and ecotoxicity of nanocomposite powders such as Au/TiO₂, Ag₂O/TiO₂, PdO/TiO₂, Ag/TiO₂/SiO₂, Ag/N(C)TiO₂, and SiO₂/TiO₂ from which Ag₂O/TiO₂, Ag/N(C)/TiO_2, and Ag/TiO₂/SiO₂ were exhibiting good antimicrobial properties. It was observed, that nanomaterials characterized by similar morphology and zeta potential revealed the similar toxic behavior. The samples of higher agglomeration and higher zeta potential, especially Ag/TiO₂/SiO₂ xerogel and TiO₂/SiO₂ aerogel were generally less ecotoxic to water organisms and plants. They were also not genotoxic in concentrations up to 500 and 250 mg/L, respectively.     

Serendipitous Identification of a Covalent Activator of Liver Pyruvate Kinase

Enzymes are effective biological catalysts that accelerate almost all metabolic reactions in living organisms. Synthetic modulators of enzymes are useful tools for the study of enzymatic reactions and can provide starting points for the design of new drugs. Here, we report on the discovery of a class of biologically active compounds that covalently modifies lysine residues in human liver pyruvate kinase (PKL), leading to allosteric activation of the enzyme (EC₅₀=0.29 μM). Surprisingly, the allosteric activation control point resides on the lysine residue K282 present in the catalytic site of PKL. These findings were confirmed by structural data, MS/MS experiments, and molecular modelling studies. Altogether, our study provides a molecular basis for the activation mechanism and establishes a framework for further development of human liver pyruvate kinase covalent activators.     

Production of H<Subscript>2</Subscript>S and properties of sulfite reductase from selected strains of wine-producing yeasts

Correlation between H₂S productivity (p) and sulfite reductase activity (A) was estimated for seven wine-producing yeasts. It was described by a linear function p=f(A), the slope of which depended on the yeast strain. The most intensive H₂S synthesis by all the examined yeasts was observed within the early logarithmic growth phase, either in nitrogen abundance and SO₂ presence, or in nitrogen deficient and SO₂-free medium. Sulfite reductase from all the strains was optimally active at pH close to 7.4. The enzyme from cryophilic yeasts displayed maximum activity at approximately 16 °C, and from mesophiles at 22–26 °C. The preparations showed different affinities toward sulfite (K_m of 16.7–67.5 M). Values of activation energy in sulfite reduction depended on the yeast, and ranged from 14.07 to 67.04 kJ mol^–1.     

Moments-Based Fast Wedgelet Transform

In the paper the moments-based fast wedgelet transform has been presented. In order to perform the classical wedgelet transform one searches the whole wedgelets’ dictionary to find the best matching. Whereas in the proposed method the parameters of wedgelet are computed directly from an image basing on moments computation. Such parameters describe wedgelet reflecting the edge present in the image. However, such wedgelet is not necessarily the best one in the meaning of Mean Square Error. So, to overcome that drawback, the method which improves the matching result has also been proposed. It works in the way that the better matching one needs to obtain the longer time it takes. The proposed transform works in linear time with respect to the number of pixels of the full quadtree decomposition of an image. More precisely, for an image of size N×N pixels the time complexity of the proposed wedgelet transform is O(N ²log ₂ N).     

Influence of technological parameters on the epoxidation of 1‐butene‐3‐ol over titanium silicalite TS‐2 catalyst

BACKGROUND: The influence of technological parameters on the epoxidation of 1‐butene‐3‐ol (1B3O) over titanium silicalite TS‐2 catalyst has been investigated. Epoxidations were carried out using 30%(w/w) hydrogen peroxide at atmospheric pressure. The major product from the epoxidation of B3O was 1,2‐epoxybutane‐3‐ol, with many potential applications. RESULTS: The influence of temperature (20–60 °C), 1B3O/H₂O₂ molar ratio (1:1–5:1), methanol concentration (5–90%(w/w)), TS‐2 catalyst concentration (0.1–6.0%(w/w)) and reaction time (0.5–5.0 h) have been studied. CONCLUSION: The epoxidation process is most effective if conducted at a temperature of 20 °C, 1B3O/H₂O₂ molar ratio 1:1, methanol concentration (used as the solvent) 80%(w/w), catalyst concentration 5%(w/w) and reaction time 5 h. Copyright © 2009 Society of Chemical Industry     

Viscosity effects in the photopolymerization of two‐monomer systems

Photopolymerization kinetics and viscosity behavior of five different two‐monomer systems forming hydrogen bonds and composed of mixtures of a high viscosity monomer (HVM) and a low viscosity monomer (LVM) at various molar ratios were investigated at six polymerization temperatures. The monomers used were mono‐ or dimethacrylates. Detailed viscosity measurements of the monomer mixtures showed significant negative deviations from the theoretical values (characterized by excess logarithm viscosities) indicating that interactions between the molecules of the same type (in individual monomers) are stronger than those between two molecules of different types (HVM and LVM). The photopolymerization kinetics were analyzed from the point of view of the appearance, viscosity and temperature behavior of the most reactive composition (MRC), the one showing the highest value of the maximum polymerization rate within a range of the HVM: LVM ratios. It was found that MRC appearance is determined mainly by the initial viscosity of the two‐monomer system, whereas the functionality of the monomers (and network formation) is much less important (MRC is observed even in linear systems). The initial viscosity of all the monomer mixtures showing MRC lay in the range of 0.06–2 Pa s, which is narrow compared to the range of viscosities of the monomers (approximately 10^?3–10³ Pa s). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal stability of poly(2-ethylhexyl acrylates) used as plasticizers for medical application

This article discusses thermal analysis of different molecular weight poly(2-ethylhexyl acrylates) synthesized by radical polymerization of 2-ethylhexyl acrylate. The main aim of this work was to investigate the thermal properties and degradation process of synthesized acrylic homopolymers and forming of thermal degradation products during their pyrolysis. As investigated method pyrolysis combined with gas chromatography was used. Poly(2-ethylhexyl acrylates) are used as plasticizers for pressure-sensitive adhesives applied in medical area.