Evaluation of the antioxidant activity by flow injection analysis method with electrochemically generated ABTS radical cation

A Trolox equivalent antioxidant capacity (TEAC) decolourisation assay was adapted to a flow injection analysis (FIA) system and a simple and rapid method for antioxidant activity evaluation was developed. To avoid the time consuming step of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS) radical cation preparation by chemical oxidation of ABTS, as in the original TAEC assay, and hence, to shorten the analysis time, the ABTS radical cation was generated on-line by electrochemical oxidation of ABTS in the flow-through electrolysis cell forming a part of the FIA system. The proposed method was optimised with respect to a flow rate, injection volume and ABTS radical cation/carrier ratio. Under the optimised conditions linear calibration graphs for Trolox were obtained over the range 10-100 microM, with a limit of detection 1.6 microM. Good reproducibility (relative standard deviation 1.95%) and sample throughput (32 samples per hour) were achieved. The developed method was applied to the evaluation of the antioxidant activity of pure compounds and samples of some common beverages. In both cases a good correlation between the results obtained by the proposed method and TEAC values evaluated by the classic TAEC decolourisation assay was obtained (r(2)= 0.996 for pure compounds and r(2)= 0.957 for beverage samples).     

Gas phase isomerization of \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 10}} {\rm H}_{{\rm 14}} } \right]_{}^{_.^ + } $\end{document} ions generated from adamantanoid compounds

\documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 10}} {\rm H}_{{\rm 14}} } \right]_{}^{_.^ + } $\end{document} ions have been generated from a number of adamantanoid compounds, both by ionization and ionization followed-by fragmentation. Metastable ion abundance ratios of competitive reactions indicate the decomposition of these ions from common structures in all cases.     

Lie algebra type noncommutative phase spaces are Hopf algebroids

For a noncommutative configuration space whose coordinate algebra is the universal enveloping algebra of a finite-dimensional Lie algebra, it is known how to introduce an extension playing the role of the corresponding noncommutative phase space, namely by adding the commuting deformed derivatives in a consistent and nontrivial way; therefore, obtaining certain deformed Heisenberg algebra. This algebra has been studied in physical contexts, mainly in the case of the kappa-Minkowski space-time. Here, we equip the entire phase space algebra with a coproduct, so that it becomes an instance of a completed variant of a Hopf algebroid over a noncommutative base, where the base is the enveloping algebra.     

κ-Poincaré–Hopf algebra and Hopf algebroid structure of phase space from twist

We unify κ-Poincaré algebra and κ-Minkowski spacetime by embedding them into quantum phase space. The quantum phase space has Hopf algebroid structure to which we apply the twist in order to get κ-deformed Hopf algebroid structure and κ-deformed Heisenberg algebra. We explicitly construct κ-Poincaré–Hopf algebra and κ-Minkowski spacetime from twist. It is outlined how this construction can be extended to κ-deformed super-algebra including exterior derivative and forms. Our results are relevant for constructing physical theories on noncommutative spacetime by twisting Hopf algebroid phase space structure.     

A novel method for flow injection analysis of total antioxidant capacity using enzymatically produced ABTS and biamperometric detector containing interdigitated electrode

Application of interdigitated array microelectrodes as electrochemical sensors for determination of antioxidant capacity is reported. Electrochemical measurements with interdigitated electrodes (IDE) were studied in both stationary solutions and the flow system. The method is based on biamperometric measurements using ABTS⁺|ABTS redox couple in phosphate buffer solution, pH 7.40. During analysis, the ABTS radical cation was enzymatically produced by peroxidase in a tubular flow-through reactor. The performance of bioreactor was tested at different concentrations of immobilized enzyme, ABTS and hydrogen peroxide. The influence of flow rate on proper operation of the bioreactor was also studied. The results of antioxidant activity were determined using Trolox as a standard. The applied IDE detector accomplished good sensitivity of 0.3 nA/μM of Trolox and offered linear range between 20 to 500 μM of Trolox.The comparison of results (R² = 0.9915) for antioxidant activity between spectroscopic and FIA biamperometric measurements by interdigitated electrodes confirmed the applicability of the proposed method for determination of antioxidant capacity.     

Binding structure of elastase inhibitor scyptolin A

Natural bioactive compounds are of general interest to pharmaceutical research because they may be used as leads in drug development campaigns. Among them, scyptolin A and B from Scytonema hofmanni PCC 7110 are known to inhibit porcine pancreatic elastase, which in turn resembles the attractive drug target neutrophil elastase. The crystal structure of scyptolin A as bound to pancreatic elastase was solved at 2.8 A resolution. The inhibitor occupies the most prominent subsites S1 through S4 of the elastase and prevents a hydrolytic attack by covering the active center with its rigid ring structure. The observed binding structure may help to design potent elastase inhibitors.     

Über die Enantiomerentrennung durch Verteilung zwischen flüssigen Phasen. 3. Mitteilung. Selektivität der lipophilen Weinsäureester für chirale Ammonium-Salze verschiedener Konstitution und Konfiguration

Separation of Enantiomers by Partition between Liquid Phases. 3. Communication. Selectivity of Lipophilic Tartaric Acid Esters for Chiral Ammonium Salts of Different Constitution and Configuration Several methods are described which allow determination on a small scale of the enantiomer distribution constant Q, and the affinity coefficient P, which characterize the enantioselectivity and the affinity of a lipophilic phase for ammonium salts of different constitution and configuration. The influence of concentration of the tartaric acid ester, temperature, concentration and type of the lipophilic anion on Q and P was investigated to find out favourable experimental conditions for resolutions of racemates by iterative process, e.g. partition chromatography. The relationship between Q and the configuration of aminoalcohols 1–12 was explored and the observed regularities are pointed out. In addition it was found that lipophilic tartaric acid esters are enantioselective to salts of threo-1,2-diphenyl-1,2-ethanediamine 13 , and to phenylglycine and its derivatives 14–16.     

High throughput plasma N-glycome profiling using multiplexed labelling and UPLC with fluorescence detection

A rapid glycomic profiling method is described wherein N-glycans from plasma samples individually labelled with aniline, 2-aminobenzamide and 2-aminoacridone are mixed, co-injected and separated in the same HILIC-fluorescence run. Transfer of the multiplexed method to UPLC-fluorescence permits an increase in sample throughput from 24 to 864 plasma samples per day.