The -Cys-Cys- motif in Helicobacter pylori's Hpn and HspA proteins is an essential anchoring site for metal ions

The Hpn and HspA proteins from H. pylori are significant for nickel homeostasis and protect the cells from higher concentrations of external metal ions. Both proteins have a unique histidine- and cysteine-rich domain at the C terminus. The interactions of Ni(2+), Bi(3+), Zn(2+) and Cd(2+) ions with C-terminal Ac-CCSTSDSHHQ-NH(2) and Ac-EEGCCHGHHE-NH(2) fragments from Hpn and the Ac-GSCCHTGNHD-NH(2) sequence from HspA were studied by potentiometry, mass spectrometry, circular dichroism and UV-Vis spectroscopy. Ac-CC-NH(2) was used as a reference peptide. The studies have shown that nickel ions form planar complexes with a {2S(-),N(-)} binding mode. The thiol sulfurs of the -Cys-Cys- motif are also the anchoring sites for Bi(3+), Zn(2+) and Cd(2+) ions. The studied protein fragments have the highest affinity for Bi(3+) ions. The thermodynamic stability of Ni(2+) is much higher then that of Zn(2+).     

N,N'-Carbonyldiimidazole-mediated functionalization of superparamagnetic nanoparticles as vaccine carrier

Particulates with specific sizes and characteristics can induce potent immune responses by promoting antigen uptake of appropriate immuno-stimulatory cell types. Magnetite (Fe(3)O(4)) nanoparticles have shown many potential bioapplications due to their biocompatibility and special characteristics. Here, superparamagnetic Fe(3)O(4) nanoparticles (SPIONs) with high magnetization value (70emug(-1)) were stabilized with trisodium citrate and successfully conjugated with a model antigen (ovalbumin, OVA) via N,N'-carbonyldiimidazole (CDI) mediated reaction, to achieve a maximum conjugation capacity at approximately 13 microgmicrom(-2). It was shown that different mechanisms governed the interactions between the OVA molecules and magnetite nanoparticles at different pH conditions. We evaluated as-synthesized SPION against commercially available magnetite nanoparticles. The cytotoxicity of these nanoparticles was investigated using mammalian cells. The reported CDI-mediated reaction can be considered as a potential approach in conjugating biomolecules onto magnetite or other biodegradable nanoparticles for vaccine delivery.     

Thermal behavior of the Cu–22.55 at.%Al alloy with small Ag additions

In this study the effect of Ag additions on the thermal behavior of the Cu–22.55 at.%Al alloy was studied using electrical resistivity measurements, in situ X-ray diffractometry, differential scanning calorimetry, and optical microscopy. The results indicated that Ag additions do not change the phase transformations sequence in the studied alloys, but modify its critical temperatures due to a change on entropy of system. It was verified that at the cooling rate of 10 K/min the decomposition of β phase into (α + γ₁) is incomplete, but for lower cooling rates than 1.0 K/min this reaction is completed.     

Speciation analysis of chromium in drinking water samples by ion-pair reversed-phase HPLC–ICP-MS: validation of the analytical method and evaluation of the uncertainty budget

The approach presented in this article refers to the modification of a method for the detection and quantitative determination of chromium species in water by high-performance liquid chromatography inductively coupled plasma mass spectrometry. The main aim of this work was to establish a detailed validation of the analytical procedure and an estimation of the budget of measurement uncertainty which was helpful in recognizing the critical points of the presented method. As a result of the method validation experiment, the obtained limit of quantification, repeatability and intermediate precision were satisfied for the quantification Cr(III) and Cr(VI) in water matrices. The trueness of the method was verified via an estimation of the recovery of the spiked real samples. The recovery rate of both determined analytes was found to be between 93 and 115 %. Considering that the validation of the method and the evaluation of measurement uncertainty are crucial for quantitative analysis, the above-mentioned assessment of the uncertainty budget was performed in two different ways: a modelling approach and a single-laboratory validation approach. The measurement uncertainties of the results were found to be 4.4 and 7.8 % for Cr(III), 4.2 and 7.9 % for Cr(VI) using the classical concept and method validation data, respectively. This paper is the first publication to presenting all the steps needed to evaluate the measurement uncertainty for the speciation analysis of chromium species. In summary, the obtained results demonstrate that the method can be applied effectively for its intended use.     

Decomposition of meta- and para-phenylphenol during ozonation process

The decomposition of meta-phenylphenol (m-PP) and para-phenylphenol (p-PP) in a heterogeneous gas-liquid system using ozone was investigated. The influence of different reaction parameters such as ozone and PP isomers concentration as well as pH and temperature of the reaction mixture on the PP decay rate was determined. The second-order rate constants for the direct reaction of molecular ozone, determined in a homogeneous system, were (5.85 ± 0.35) × 10² M^?1 s^?1 and (8.90 ± 0.33) × 10² M^?1 s^?1 for m-PP and p-PP, respectively. The rate constants for the reaction of m-PP and p-PP with ozone increased with increasing pH. The reaction rate constants with ozone were found to be (1.75 ± 0.02) × 10⁹ M^?1 s^?1 and (1.86 ± 0.02) × 10⁹ M^?1 s^?1 for m-PP and p-PP anions, respectively.     

The use of DSC and FT-IR spectroscopy for evaluation of oxidative stability of interesterified fats

The aim of this paper was to assess the oxidative stability of structured lipids synthesized by enzymatic interesterification of a blend of lard and rapeseed oil with concentrates of n ? 3 fatty acids. Differential scanning calorimetry was used to evaluate the oxidation induction time of interesterified fats as a parameter assessing resistance of tested fats to their thermal-oxidative decomposition. Moreover, the IR spectra registered in the classic spectral range (4000–400 cm^?1) were used to differentiate the samples of interesterified fats. The results show that the interesterification process decreased the induction time. Increased content polar fraction in the interesterified fatty product can reduce its resistance to oxidation. FT-IR data of selected spectral ranges correlate with the value of induction time at a statistically significant level. This is a proof that chemical changes occurring during different treatments of the starting mixture can be monitored by FT-IR spectroscopy. Moreover, obtained correlations can be used for the evaluation of an induction value of an unknown oil sample.     

Antimicrobial properties of biosynthesized silver nanoparticles studied by flow cytometry and related techniques

This work reports the effect of silver bionanoparticles (Bio(AgNPs) synthesized by Actinobacteria CGG 11n on selected Gram (+) and Gram (–) bacteria. Flow cytometry, classical antibiogram method and fluorescent microscopy approach was used for evaluation of antimicrobial activity of Bio(AgNPs) and their combination with antibiotics. Furthermore, the performed research specified the capacity of flow cytometry method as an alternative to the standard ones and as a complementary method to electromigration techniques. The study showed antibacterial activity of both BioAgNPs and the combination of antibiotics/BioAgNPs against all the tested bacteria strains in comparison with a diffusion, dilution and bioautographic methods. The synergistic effect of antibiotics/BioAgNPs combination (e.g. kanamycin, ampicillin, neomycin and streptomycin) was found to be more notable against Pseudomonas aeruginosa representing a prototype of multi‐drug resistant “superbugs” for which effective therapeutic options are very limited.     

Influence of the chelate ligand structure on the amide methanolysis reactivity of mononuclear zinc complexes

Zinc complexes of three new amide-appended ligands have been prepared and isolated. These complexes, [(dpppa)Zn](ClO4)2 (4(ClO4)2; dpppa = N-((N,N-diethylamino)ethyl)-N-((6-pivaloylamido-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine), [(bdppa)Zn](ClO4)2 (6(ClO4)2; bdppa = N,N-bis((N,N-diethylamino)ethyl)-N-((6-pivaloylamido-2-pyridyl)methyl)amine), and [(epppa)Zn](ClO4)2 (8(ClO4)2; epppa = N-((2-ethylthio)ethyl)-N-((6-pivaloylamido-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine), have been characterized by X-ray crystallography (4(ClO4)2 and 8(ClO4)2), 1H and 13C NMR, IR, and elemental analysis. Treatment of 4(ClO4)2 or 8(ClO4)2 with 1 equiv of Me4NOH.5H2O in methanol-acetonitrile (5:3) results in amide methanolysis, as determined by the recovery of primary amine-appended forms of the chelate ligand following removal of the zinc ion. These reactions proceed via the initial formation of a deprotonated amide intermediate ([(dpppa-)Zn]ClO4 (5) and [(epppa-)Zn]ClO4 (9)) which in each case has been isolated and characterized (1H and 13C NMR, IR, elemental analysis). Treatment of 6(ClO4)2 with Me4NOH.5H2O in methanol-acetonitrile results in the formation of a deprotonated amide complex, [(bdppa-)Zn]ClO4 (7), which was isolated and characterized. This complex does not undergo amide methanolysis after prolonged heating in a methanol-acetonitrile mixture. Kinetic studies and construction of Eyring plots for the amide methanolysis reactions of 4(ClO4)2 and 8(ClO4)2 yielded thermodynamic parameters that provide a rationale for the relative rates of the amide methanolysis reactions. Overall, we propose that the mechanistic pathway for these amide methanolysis reactions involves reaction of the deprotonated amide complex with methanol to produce a zinc methoxide species, the reactivity of which depends, at least in part, on the steric hindrance imparted by the supporting chelate ligand. Amide methanolysis involving a zinc complex supported by a N2S2 donor chelate ligand (3(ClO4)2) is more complicated, as in addition to the formation of a deprotonated amide intermediate free chelate ligand is present in the reaction mixture.