Miscibility of gramicidin A-ethyl nonadecanoate in langmuir monolayers in the presence of salts dissolved in the subphase

The behavior of binary mixed Langmuir monolayers from gramicidin A (GA) and ethyl nonadecanoate (EN), spread on aqueous subphases containing NaCl and CaCl2, was investigated on the basis of the analysis of surface pressure-average area per molecule (pi-A) isotherms complemented with Brewster angle microscopy (BAM) images. Compression modulus versus surface pressure (C(S-1)-pi) curves indicate the existence of interactions in the GA-EN mixed monolayers at low surface pressures (below 5 mN m(-1)). However, for mixtures in which the ester is the predominant component, both GA and EN are miscible within regions from fully expanded to collapse. To examine the interactions between both components in the studied system, values of the mean molecular area per molecule (A12) were plotted as a function of molar fraction of gramicidin A (X(GA)). A12-X(GA) plots exhibit negative deviations from ideality at high surface pressures, wherein beta-helices of GA are vertically oriented in respect to the interface. However, at surface pressures below the plateau transition, which is due to reorientation of GA, the binary system obeys the additive rule. Brewster angle microscopy (BAM) was applied for a direct visualization of the monolayers morphologies. The obtained images prove that for molar ratios of GA > or = 0.3 and at surface pressures above 5 mN m(-1), both components are immiscible at the interface. The observed negative deviations from the additively rule were attributed to the formation of a three-dimensional phase in the mixed film, which provokes its contraction at the interface.     

Strychninium N‐phthaloyl‐β‐alaninate N‐phthaloyl‐β‐alanine and brucinium N‐phthaloyl‐β‐alaninate 5.67‐hydrate

Comparison of the structures of strychninium N‐phthaloyl‐β‐alaninate N‐phthaloyl‐β‐alanine, C₂₁H₂₃N₂O₂⁺·C₁₁H₈NO₄⁻·C₁₁H₉NO₄, and brucinium N‐phthaloyl‐β‐alaninate 5.67‐hydrate, C₂₃H₂₇N₂O₄⁺·C₁₁H₈NO₄⁻·5.67H₂O, reveals that, unlike strychninium cations, brucinium cations display a tendency to produce stacking inter­actions with cocrystallizing guests.     

1,4‐Michael Addition – The Analytical Way for Quantitative Sensing of Neurotransmitter at Bare Gold Electrode in Physiological Solution in the Presence of Interfering Biogenic Compounds

Electrooxidation of norepinephrine in the presence a nucleophile was investigated on a bare gold electrode. Electrochemically produced norepinephrinequinone undergoes an attack by morpholine as nucleophile via 1,4‐Michael addition. The reaction products were identified by electrospray ionization mass spectrometry. The procedure used was suitable for quantitative norepinephrine determination in the concentration range from 1×10^?9 M to 8×10^?4 M with a detection limit of 8.7×10^?10 M in a samples containing an excess of ascorbic and uric acids. The proposed method is simple, green which means that it does not require the use of toxic compounds and solvents and thus is promising for detection of norepinephrine in physiological environment.     

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.     

Thermal properties of fats extracted from powdered baby formulas

The aim of this research was to analyse composition, fatty acids distribution and oxidative stability of fats extracted from four samples of baby formulas. The fats were oxidized in a differential scanning calorimeter (DSC) under polythermal (dynamic) conditions and at normal pressure. The DSC experiments were carried out in an oxygen flow atmosphere using different, linearly programmed, heating rates in the range of 4?C12.5?°C/min. The extrapolated onset temperatures were determined using DSC exotherms and used for the assessment of the thermal oxidative stabilities of the samples. Activation energies (E _a), pre-exponential factors (Z) and reaction rate constants (k) for oil oxidation under DSC conditions were calculated using the Ozawa?CFlynn?CWall method and the Arrhenius equation. The melting characteristics of the studied fats were obtained. The fats extracted from the agglomerated samples with higher onset temperatures were more stable than the fats extracted from the initial samples of baby formulas.     

Biparametric multicommutated flow analysis system for determination of human serum phosphoesterase activity

A multicommutated flow analysis (MCFA) system constructed of microsolenoid valves and pumps offering simultaneous determination of activity of acid phosphatase (ACP) and alkaline phosphatase (ALP) in human serum samples has been developed. The MCFA system is based on optoelectronic flow-through detector made of two light emitting diodes and operating according to paired emitter detector diode (PEDD) principle. This photometric PEDD device has been dedicated for detection of p-nitrophenol (NP) generated in the course of enzymatic hydrolysis of p-nitrophenyl phosphate and optimized for the determination of NP in human serum samples. The developed PEDD-based MCFA system allows independent optimization of conditions for reaction and detection steps of photometric ACP and ALP bioassays. Moreover, it allows elimination of photometric interferences from serum matrix components according to two-points kinetic mode of measurement. The single measurement cycle takes 12 min, consists of four measurements (two for each phosphoesterase) and enables determination of serum ACP and ALP activities at physiological and pathological levels. The real analytical utility of the developed MCFA system has been confirmed by analysis of control sera as well as real human serum samples from healthy persons and oncological patients.     

Betaine and Carnitine Derivatives as Herbicidal Ionic Liquids

This study focused on the synthesis and subsequent characterization of herbicidal ionic liquids based on betaine and carnitine, two derivatives of amino acids, which were used as cations. Four commonly used herbicides (2,4‐D, MCPA, MCPP and Dicamba) were used as anions in simple (single anion) and oligomeric (two anions) salts. The obtained salts were subjected to analyzes regarding physicochemical properties (density, viscosity, refractive index, thermal decomposition profiles and solubility) as well as evaluation of their herbicidal activity under greenhouse and field conditions, toxicity towards rats and biodegradability. The obtained results suggest that the synthesized herbicidal ionic liquids displayed low toxicity (classified as category 4 compounds) and showed similar or improved efficacy against weed compared to reference herbicides. The highest increase was observed during field trials for salts containing 2,4‐D as the anion, which also exhibited the highest biodegradability (>75 %).