Mineral oxides and layered minerals in combination with itaconic acid as coagents for peroxide crosslinking of hydrogenated acrylonitrile-butadiene elastomer

The aim of this work was to study the activity of nanosized calcium and magnesium oxides and layered minerals (boehmite, hydrotalcite) as coagents in the crosslinking of hydrogenated acrylonitrile-butadiene elastomer (HNBR) with dicumyl peroxide. The surfaces of the mineral oxides and layered minerals were modified with unsaturated acid (itaconic acid) to ensure their activity during the crosslinking process. The efficiency of modification process was estimated, based on thermogravimetric analysis and zeta potential measurements of obtained coagents. In this article, we discuss the effect of coagents on the crosslinking density and mechanical properties of vulcanisates. Application of nanosized mineral oxides and layered minerals together with itaconic acid decreased the optimal vulcanisation time of rubber compounds and improved the crosslinks density as well as the tensile strength of the vulcanisates due to formation of additional ionic crosslinks in the elastomer network. It is important from technological reasons.     

Mobile-phase pH influence on the retention of some benzoic acid derivatives in reversed-phase chromatography

Five end-capped octadecyl RP stationary phases, among which one was a polar embedded stationary phase, were tested for the analysis of benzoic acid derivatives using two mobile phases with or without addition of formic acid (water pH was measured by a common approach; pH of water with addition of formic acid was 3.0 and without formic acid 5.8). The influence of mobile-phase pH on the retention of benzoic acid derivatives was under study. Consequently, Purospher-STAR and Alltima columns provided symmetrical peaks for benzoic acid derivatives at pH 3.0 and also at pH 5.8. Reprosil and Symmetry stationary phases showed poor peak shapes at higher pH of the mobile phase. Differences between the tested columns may be caused by surface heterogeneity. Another reason may be the presence of some atoms creating additional adsorption sites on the surface of Reprosil and Symmetry stationary phases. This can lead to enhanced silanol activity resulting in peak tailing. The addition of formic acid into the mobile phase improved peak shapes. The polar embedded C18 stationary-phase Synergi-Fusion-RP appeared as not a suitable column for the analysis of benzoic acid derivatives. Synergi-Fusion-RP provided asymmetrical peaks even if formic acid was added into the mobile phase.     

Thermodynamic and kinetic studies on the binding of nitric oxide to a new enzyme mimic of cytochrome p450

A new model for the P450 enzyme carrying a SO(3)(-) ligand coordinated to iron(III) (complex 2) reversibly binds NO to yield the nitrosyl adduct. The rate constant for NO binding to 2 in toluene is of the same order of magnitude as that found for the nitrosylation of the native, substrate-bound form of P450(cam) (E.S-P450(cam)). Large and negative activation entropy and activation volume values for the binding of NO to complex 2 support a mechanism that is dominated by bond formation with concomitant iron spin change from S = (5)/(2) to S = 0, as proposed for the reaction between NO and E.S-P450(cam). In contrast, the dissociation of NO from 2(NO) was found to be several orders of magnitude faster than the corresponding reaction for the E.S-P450(cam)/NO system. In a coordinating solvent such as methanol, the alcohol coordinates to iron(III) of 2 at the distal position, generating a six-coordinate, high-spin species 5. The reaction of NO with 5 in methanol was found to be much slower in comparison to the nitrosylation reaction of 2 in toluene. This behavior can be explained in terms of a mechanism in which methanol must be displaced during Fe-NO bond formation. The thermodynamic and kinetic data for NO binding to the new model complexes of P450 (2 and 5) are discussed in reference to earlier results obtained for closely related nitrosylation reactions of cytochrome P450(cam) (in the presence and in the absence of the substrate) and a thiolate-ligated iron(III) model complex.     

Synthesis,Pharmacological Evaluation,and Computational Studies of Cyclic Opioid Peptidomimetics Containing β3-Lysine

Our formerly described pentapeptide opioid analog Tyr-c[D-Lys-Phe-Phe-Asp]NH₂ (designated RP-170), showing high affinity for the mu (MOR) and kappa (KOR) opioid receptors, was much more stable than endomorphine-2 (EM-2) in the rat brain homogenate and displayed remarkable antinociceptive activity after central (intracerebroventricular) and peripheral (intravenous ) administration. In this report, we describe the further modification of this analog, which includes the incorporation of a β³-amino acid, (R)- and (S)-β³-Lys, instead of D-Lys in position 2. The influence of such replacement on the biological properties of the obtained analogs, Tyr-c[(R)-β³-Lys-Phe-Phe-Asp]NH₂ (RP-171) and Tyr-c[(S)-β³-Lys-Phe-Phe-Asp]NH₂, (RP-172), was investigated in vitro. Receptor radiolabeled displacement and functional calcium mobilization assays were performed to measure binding affinity and receptor activation of the new analogs. The obtained data revealed that only one of the diastereoisomeric peptides, RP-171, was able to selectively bind and activate MOR. Molecular modeling (docking and molecular dynamics (MD) simulations) suggests that both compounds should be accommodated in the MOR binding site. However, in the case of the inactive isomer RP-172, fewer hydrogen bonds, as well as instability of the canonical ionic interaction to Asp¹⁴⁷, could explain its very low MOR affinity.     

Isotopic fingerprints of the Lake Żabińskie (NE Poland) hydrological system on contemporary carbonates precipitated in the lake

An isotopic monitoring was undertaken in 2012–2014 at Lake ?abińskie (Mazurian Lakeland, NE Poland). The aim was to identify the factors and processes controlling an isotopic composition of the lake water and to explore the mechanism responsible for recording the climatic signal in stable isotope composition of deposited carbonates. δ¹⁸O and δ²H in the precipitation, lake water column, inflows and outflow, δ¹⁸O and δ¹³C in the carbonate fraction of sediments trapped in the water column were recorded with monthly resolution. A relationship between δ¹⁸O and δ²H in local precipitation was used to estimate the local meteoric water line. The dataset obtained for the water enabled to identify the modification of the water’s isotopic composition due to evaporation, connected with seasonal lake water stratification and mixing patterns. Statistically significant correlation coefficients suggest that the δ¹⁸O of the carbonate fraction in the sediment traps depends on the δ¹⁸O of rainfall water and on air temperature. The fractionation coefficient α shows that in summer months the carbonate precipitation process is closest to equilibrium. As expected for an exorheic lake, no significant correlation was observed between δ¹⁸O and δ¹³C in precipitated carbonate.     

Fast analysis of 19 anabolic steroids in bovine tissues by high performance liquid chromatography with tandem mass spectrometry

For the detection of 19 steroid hormones in bovine muscle, a fast and sensitive liquid chromatography with electrospray ionization tandem mass spectrometry method was developed using both positive and negative ionization mode. Chromatographic separation on Poroshell 120‐EC C18 column was achieved in less than 10 min using isocratic elution of mobile phase of acetonitrile/methanol/water. The compounds were extracted from muscle tissue using ethyl acetate and quick, easy, cheap, effective, rugged, and safe technique. The purification of the obtained extract was performed by dispersive solid‐phase extraction with sorbents C18, primary secondary amine and magnesium sulphate. The method was validated in accordance with the Commission Decision 2002/657/EC. For all steroids tested good recoveries were obtained (from 51.2 to 121.4%) in the concentration range from decision limits until 5 µg/kg. The values of decision limits and the detection capabilities for individual compounds were in the range 0.10–0.48 and 0.17–0.95 µg/kg, respectively. The method was characterized by satisfactory linearity for most compounds (correlation coefficients  > 0.99) and the reproducibility was lower than 35%. The elaborated procedure has met the criteria for confirmatory methods and is currently used in the official control of hormones.     

Effect of the Addition of Dried Dandelion Roots (Taraxacum officinale F. H. Wigg.) on Wheat Dough and Bread Properties

Dried and crushed dandelion roots (Taraxacum officinale F. H. Wigg.) (TO) were used as a formulation additive (at the amount of 0, 1, 3, 4, 5, and 6 g 100 g⁻¹ flour) to wheat bread. The farinographic properties of the dough and the physical and chemical properties of the bread were evaluated. It was found that the addition of dried flour caused a significant decrease in water absorption by the flour (1% and higher TO level), an increase in the development time (from 2% to 5% TO addition) and dough stability (3% and 4% TO level), and an increase in dough softening (4% and higher TO level). As the substitution of TO for wheat flour increased, there was a gradual decrease in loaf volume, an increase in specific weight and crumb hardness, and a darkening of the crumb color. The total polyphenol content increased linearly with the percentage increase of dried root additions TO from 0.290 to 0.394 mg GAE g⁻¹ d.m_., which translated into an increase in the antioxidant activity of the bread. It was found that dried crushed roots of Taraxacum officinale can be a recipe additive for wheat bread; however, due to their specific smell and bitter aftertaste, the level of this additive should not exceed 3 g 100 g⁻¹ flour.     

ChemInform Abstract: Influence of Nickel Substitution on the Cation Distribution and Magnetic Properties of ZnCr2Se4.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Synthesis and antifungal activity of novel 5‐substituted 4‐(1,3,4‐thiadiazol‐2‐yl)benzene‐1,3‐diols

5‐Substituted (amine, alkyl, aryl, heterocyclic) 4‐(1,3,4‐thiadiazol‐2‐yl)benzene‐1,3‐ diols were synthesized, and their antifungal properties were examined. The compounds were obtained by the one‐pot reaction of sulfinylbis((2,4‐dihydroxyphenyl)methanethione) with hydrazides or thiosemicarbazides. Their structures were identified from elemental, IR, ¹H NMR, and MS spectra analyses. The activities of the derivatives against five phytopathogenic fungi in vitro were measured. Moderate fungicidal effect of the compounds under consideration was found. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:533–540, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20645     

Polarity identification of GaN bulk single crystals (0001) surface by Auger electron spectroscopy

An attempt to identify the polarity of (0001) polar surface of GaN bulk single crystals grown by high nitrogen pressure solution method has been made using Auger electron spectroscopy (AES). AES concentration depth profiles of the top layer in (0001) direction starting from both (0001) faces of the sample have been measured. Distinct difference in the Ga concentration at the sample surface of both faces has been observed. The dependence of Ga eoncentration on depth is also different for both faces of the sample.