Determination of the limits of applicability of the chemical equilibrium model to the detonation products of gas mixtures

The applicability of the model of a chemically equilibrium mixture to describing the evolution of the composition of the detonation products during their expansion in three typical problems involving oxygen- and air-based combustible mixtures is examined. For the detonation products of oxygen-based mixtures, the model of a chemical equilibrium mixture provides a good agreement with the kinetic calculations for all practically important initial conditions for these problems. For air-based mixtures, initial conditions at which such an agreement is observed are determined.     

Effect of dose and dose rate of gamma radiation on catalytic activity of catalase

Catalytic activity of gamma irradiated catalase from bovine liver was studied for hydrogen peroxide decomposition at constant temperature and pressure. The measurement was performed at temperatures 27, 32, 37, 42 and 47 °C. Solutions containing 1 and 0.01 g dm⁻³ of catalase in phosphate buffer were used for the study. Repeatability of both sample preparation and kinetics measurement was experimentally verified. Rate constants of the reaction were determined for all temperatures and the activation energy was evaluated from Arrhenius plot. Gamma irradiation was performed using ⁶⁰Co radionuclide source Gammacell 220 at two different dose rates 5.5 and 70 Gy h⁻¹, with doses ranging from 10 to 1000 Gy. The observed reaction of irradiated and non-irradiated catalase with hydrogen peroxide is of the first order. Irradiation significantly decreases catalytic activity of catalase, but the activation energy does not depend markedly on the dose. The effect of irradiation is more significant at higher dose rate.     

Iminodiacetic acid-modified magnetic poly(2-hydroxyethyl methacrylate)-based microspheres for phosphopeptide enrichment

Magnetic non-porous hydrophilic poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate) microspheres prepared by the dispersion polymerization and modified with iminodiacetic acid (IDA) were employed for the IMAC separation of phosphopeptides. Fe³⁺ and Ga³⁺ ions immobilized on IDA-modified magnetic microspheres were used for the enrichment of phosphopeptides from the proteolytic digests of two model proteins differing in their physico-chemical properties and phosphate group content: porcine pepsin A and bovine α-casein. The optimum conditions for phosphopeptide adsorption and desorption in both cases were investigated and compared. The phosphopeptides separated from the proteolytic digests were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The ability of the prepared Fe³⁺- and Ga³⁺-IDA-modified magnetic microspheres to capture phosphopeptides from complex mixtures was shown on an example of bovine milk proteolytic digest.     

Azidoacetone as a complexing agent of transition metals Ni2+/Co2+ promoted dissociation of the C-C bond in azidoacetone

The relevance of metal interactions with azides has led us to the study of the complexation of some transition metals, nickel and cobalt, by azidoacetone by means of electrospray ionization mass spectrometry (ESI-MS). Complexes were obtained from solutions of NiCl(2) and CoCl(2) , in methanol/water. Nickel was electrosprayed with other counter ion, bromide (Br), as well as other solvent (ethanol/water). For nickel and cobalt, the complexes detected were single positively charged, with various stoichiometries, some resulted from the fragmentation of the ligand, the loss of N(2) being quite common. The most abundant species were [Ni(II)Az(2)X](+) where X = Cl, Br and Az = azidoacetone. Some of the complexes showed solvation with the solvent components. Metal reduction was observed in complexes where a radical was lost, resulting from the homolytic cleavage of a metal coordination bond. Collision-induced dissociation (CID) experiments followed by tandem mass spectrometry (MS-MS) analysis were not absolutely conclusive about the coordination site. However, terminal ions of the fragmentation routes were explained by a gas-phase mechanism proposed where a C-C bond was activated and the metal inserted subsequently. Density functional theory calculations provided structures for some complexes. In [Ni(II)Az(2)X](+) species, one azidoacetone ligand is monodentate and the dominant binding location is the alkylated nitrogen and not the carbonyl group. The other azidoacetone ligand is bidentate showing coordination through alkylated nitrogen and the carbonyl group. These are also the preferential binding sites for the most stable isomer of [Ni(II)AzX](+) species.     

On the way to understand antioxidants: chromanol and dimethoxyphenols gas-phase acidities

Some antioxidant mechanisms displayed by several phenolic compounds relate with OH bond dissociation energy. One way for its determination, in the gas-phase, relies on acidity measurements. Gas-phase acidities were determined experimentally, applying the kinetic method, for chromanol and four dimethoxyphenols, and theoretically through quantum chemical DFT calculations for chromanol, six dimethoxyphenols and 3,4,5-trimethoxyphenol. The experimental acidity order, 2,3-dimethoxyphenol > 3,5-dimethoxyphenol > 2,6-dimethoxyphenol > 3,4-dimethoxyphenol ≈ phenol > chromanol shows good agreement with the theoretical acidity order, 2,5-dimethoxyphenol > 2,3-dimethoxyphenol > 3,4,5-trimethoxyphenol > 3,5-dimethoxyphenol ≈ 2,4-dimethoxyphenol > 2,6-dimethoxyphenol > 3,4-dimethoxyphenol > phenol > chromanol. These acidity trends were rationalized in terms of the substituent effects on the thermodynamic stabilities both of the parent phenols and the corresponding phenoxide ions. DFT calculations also evidenced the occurrence of intramolecular C-H···O hydrogen bonds whenever there are vicinal substituents (either OH, O(-) or OCH(3)) which induce further stabilization of the geometries.     

The UHPLC-DAD fingerprinting method for analysis of extracellular metabolites of fungi of the genus <Emphasis Type="Italic">Geosmithia</Emphasis> (Acomycota: Hypocreales)

A new simple ultra-high-performance liquid chromatography method with diode array detection (UHPLC-DAD) was developed for chemical fingerprinting analysis of extracellular metabolites in fermentation broth of Geosmithia spp. The SPE method employing Oasis MCX strong cation-exchange mixed-mode polymeric sorbent was chosen for extraction of the metabolites. The analyses were performed on an Acquity UPLC BEH C18 column (100 × 2.1 mm i.d.; particle size, 1.7 μm; Waters) using a gradient elution program with an aqueous solution of trifluoroacetic acid and acetonitrile as the mobile phase. The applicability of the method was proved by analysis of 38 strains produced by different species and isolated from different sources (hosts). The results revealed the correlation of obtained UHPLC-DAD fingerprints with taxonomical identity.     

Affinity liquid chromatography and capillary electrophoresis of seminal plasma proteins

Interactions of boar, bull, and human seminal plasma proteins with heparin and phosphorylcholine were studied by affinity LC using heparin immobilized to a Toyopearl support. A step gradient elution from 0.15 to 1.50 M NaCl was employed to elute the seminal plasma proteins. Relative amounts of the heparin-binding fraction of seminal plasma proteins (H+) in seminal plasma of three species were determined. Further on, the fraction of seminal plasma proteins interacting with phosphorylcholine-binding proteins (P+) was evaluated. P+ proteins were not found in human seminal plasma and their highest amount was present in bull seminal plasma. A CE method was developed for separation of seminal plasma proteins. Various capillaries and separation conditions were tested; the best resolution was obtained in a bare-silica capillary, with a micellar system consisting of a 0.02 M borate buffer and 0.05 M SDS pH 10.0. The optimized conditions were applied to the identification of the components in boar plasma.     

Optical and X-ray emission spectroscopy of high-power laser-induced dielectric breakdown in molecular gases and their mixtures

Large-scale plasma was created in molecular gases (CO, CO2, N2, H2O) and their mixtures by high-power laser-induced dielectric breakdown (LIDB). Compositions of the mixtures used are those suggested for the early earth's atmosphere of neutral and/or mildly reducing character. Time-integrated optical spectra emitted from the laser spark have been measured and analyzed. The spectra of the plasma generated in the CO-containing mixtures are dominated by emission of both C2 and CN radicals. A vibrational temperature of approximately 10(4) K was determined according to an intensity distribution in a vibronic structure of the CN (B2Sigma(+)u-X2Sigma(+)g) violet band. For comparison, the NH3-CH4-H2-H2O mixture has been irradiated as a model of the strongly reducing version of the early earth's atmosphere. In this mixture, excited CN seems to be significantly less abundant than C2. The LIDB experiments were in the molecular gases carried out not only in the static cell but also using a large, double stream pulse jet (gas puff target) placed in the vacuum interaction chamber. The obtained soft X-ray emission spectra indicate the presence of highly charged atomic ions in the hot core of high-power laser sparks.     

Parkia pendula Seed Lectin: Potential Use to Treat Cutaneous Wounds in Healthy and Immunocompromised Mice

Parkia pendula seed lectin was used to treat cutaneous wounds of normal and immunocompromised mice, inducing cicatrization. Methotrexate (0.8 mg/kg/week) was used as immunosuppressive drug. Wounds were produced in the dorsal region (1 cm²) of female albino Swiss mice (Mus musculus), health and immunocompromised. Wounds were daily topically treated with 100 μL of the following solutions: (1) control (NaCl 0.15 M), (2) control Im (0.15 M NaCl), (3) P. pendula seed lectin (100 μg/mL), and (4) P. pendula seed lectin Im (100 μg/mL). Clinical evaluation was performed during 12 days. Biopsies for histopathology analysis and microbiological examinations were carried out in the second, seventh, and 12th days. The presence of edema and hyperemia was observed in all groups during inflammatory period. The first crust was detected from the second day, only in the groups treated with P. pendula seed lectin. Microbiological analysis of wounds from day 0 to day 2 did not show bacterium at P. pendula seed lectin group; however, Staphylococcus sp. was detected every day in the other groups. The lectin markedly induced a total wound closing at P. pendula seed lectin and P. pendula seed lectin Im groups on 11th day of evolution. The present study suggests that P. pendula seed lectin is a biomaterial potential to show pharmacological effect in the repair process of cutaneous wounds.     

Simultaneous Determination of 11 Elements in Fly Ash by Inductively Coupled Plasma Orthogonal Acceleration Time-of-Flight Mass Spectrometry After Closed-Vessel Microwave-Assisted Extraction with Ammonium Fluoride

A method for simultaneous multi-element analysis of fly ash samples by inductively coupled plasma orthogonal acceleration time-of-flight mass spectrometry (oaTOF-ICP-MS) after closed-vessel microwave extraction with ammonium fluoride was introduced here. Corrosive and/or toxic acids like HF, HCl or HClO₄, as well as HNO₃, which are commonly used during sample preparation of the fly ash samples, are avoided in this method. The spectral effects due to the formation of different Cl, Na, K, Ca, Mg-containing polyatomic species interfering with the determination of a number of elements like As, Se or Ni during the oaTOF-ICP-MS analysis are negligible. Under the optimum experimental extraction conditions evaluated using a fractional factorial design (10 mg of the sample extracted with 5 mL of 140 g/L NH₄F for 10 min at 200°C), analysis of the resulting supernatant with Rh as an internal standard enabled precise and accurate simultaneous determination of 11 elements (Li, Be, Ni, As, Se, Rb, Sb, Cs, W, Tl and U) at trace and ultratrace levels. The accuracy was assessed by analysing two certified reference materials, namely Fine Fly Ash CTA-FFA-1 and Constituent Elements in Coal Fly Ash Standard Reference Material® 1633b. The precision of the reported method was better than 10%.