Sample preparation on polymeric solid phase extraction sorbents for liquid chromatographic-tandem mass spectrometric analysis of human whole blood--a study on a number of beta-agonists and beta-antagonists

Alternative strategies for sample preparation of human blood samples were evaluated including protein precipitation (PP) and solid phase extraction (SPE) on Waters Oasis polymeric columns. Gradient chromatography within 15 min was performed on a Hypersil Polar-RP column combined with a Sciex API 2000 triple quadrupol instrument equipped with an electro-spray interface. Beta-agonists and beta-antagonists available on the Swedish market were included in the study. A combination of zinc sulphate and ethanol was found effective for PP. A clear supernatant was achieved that either could be injected directly on the LC-MS-MS system for analysis or transferred to a SPE column for further extraction and analyte concentration. Retention on the hydrophilic-lipophilic balanced sorbent HLB as well as the mixed mode cationic MCX and anionic MAX sorbents were investigated. On HBL the relative lipophilicity of the target analytes was investigated. At a high pH when the amino alcohols are deprotonised the more non-polar analytes (e.g., carvediol, betaxolol, bisoprolol and propranolol) were well retained on the sorbent and for the majority methanol content higher than 50% in water (v/v) was needed for elution. Some analytes though, with additional weak acidic functionalities (fenoterol, salbutamol, sotalol, and terbutaline) were poorly retained. On MAX the retention of these weak acids was improved when loaded under basic conditions but under neutral conditions analyte recoveries was comparable with HLB. On MCX all the analytes were well retained allowing a wash step of 100% methanol at neutral and low pH. By applying the supernatant from PP in combination with an additional portion of aqueous formic acid (2%) the analytes could be loaded and retained. High extraction recoveries were found for most analytes but for a few, significant losses were seen during PP (e.g., formoterol) and/or evaporation (e.g., fenoterol, formoterol, labetalol and terbutaline). The effectiveness of the sample preparation was evaluated by ESI ion-suppression studies by post column infusion of the target analyte. An ethanol zinc sulphate aq mixture was found to be more effective than acetonitrile, methanol or ethanol for PP of human whole blood samples. Beside suppression by salts in the front peak, only limited suppression from other artefacts such as more lipophilic compounds was found late in the chromatograms. Some tendency though to concentrate more lipophilic artefacts on the Oasis sorbents was seen. These findings show that the Oasis MCX sorbent is well suited for sample preparation of beta-agonists and beta-antagonists from human whole blood if the objective is to cover a great number of the analytes in the same assay.     

The radical mechanism of cobalt(II) porphyrin-catalyzed olefin aziridination and the importance of cooperative H-bonding

The mechanism of cobalt(II) porphyrin-mediated aziridination of styrene with PhSO(2)N(3) was studied by means of DFT calculations. The computations clearly indicate the involvement of a cobalt 'nitrene radical' intermediate in the Co(II)(por)-catalyzed alkene aziridination. The addition of styrene to this species proceeds in a stepwise fashion via radical addition of the 'nitrene radical'C to the C=C double bond of styrene to form a γ-alkyl radical intermediate D. The thus formed tri-radical species D easily collapses in an almost barrierless ring closure reaction (TS3) to form the aziridine, thereby regenerating the cobalt(II) porphyrin catalyst. The radical addition of the 'nitrene radical'C to the olefin (TS2) proceeds with a comparable barrier as its formation (TS1), thus providing a good explanation for the first order kinetics in both substrates and the catalyst observed experimentally. Formation of C is clearly accelerated by stabilization of C and TS1 via hydrogen bonding between the S=O and N-H units. The computed radical-type mechanism agrees well with all available mechanistic and kinetic information. The computed free energy profile readily explains the superior performance of the Co(II)(porAmide) system with H-bond donor functionalities over the non-functionalized Co(TPP).     

Study of the nitric oxide system in the rat cerebellum during aging

Background  

The cerebellum is the neural structure with the highest levels of nitric oxide, a neurotransmitter that has been proposed to play a key role in the brain aging, although knowledge concerning its contribution to cerebellar senescence is still unclear, due mainly to absence of integrative studies that jointly evaluate the main factors involved in its cell production and function. Consequently, in the present study, we investigate the expression, location, and activity of nitric oxide synthase isoenzymes; the protein nitration; and the production of nitric oxide in the cerebellum of adult and old rats.     

The garner heavy duty quartz fiber microbalance

Summary A Garner balance is described which by means of a vertical suspension fiber is said to be capable of weighing a 5-g load with a sensitivity better than that attainable with the ordinary knife-edge balance. Its weighing chambers were especially designed to accommodate light absorption tubes for the determination of carbon and hydrogen. A practical system for eliminating vibration and furnishing a suitable mounting for sensitive quartz fiber balances in the industrial laboratory is also reported. Under a 5-g load, the Garner balance was found to give strict proportionality within±0.001 mg between torsion and weight. It reproduces within ±0.26g when weighing a 0.4-g platinum boat with the torsion fiber under continuous strain.

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Zusammenfassung Eine Garner Mikrowaage mit Quarzbalken wird beschrieben, deren Empfindlichkeit die der üblichen, auf Schneiden ruhenden Feinwaagen übertrifft und die doch eine Last von 5 g tragen kann, da der Balken von einem vertikalen Quarzfaden getragen wird. Die Gehänge und Gehängekammern wurden zur Aufnahme von leichten Absorptionsapparaten speziell entworfen. Eine für das Industrielaboratorium geeignete, praktische Aufstellung der Waage, die störende Vibrationen ausschließt, wird beschrieben. Unter Maximalbelastung von 5 g wurde Proportionalität innerhalb±0,001 mg zwischen Gewicht und kompensierender Torsionskraft festgestellt. Das Gewicht eines Platinschiffchens (0,4 g) konnte mit einem mittleren Fehler von ±0,26g reproduziert werden, wenn der horizontale Torsionsfaden aus Quarz ständig unter Torsionsspannung gehalten wurde.

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Résumé On décrit une balance de Garner qui, au moyen d'un fil de suspension vertical, est capable de peser une charge de 5 g avec une sensibilité meilleure que celle que l'on obtient avec une balance à couteau ordinaire. Ses compartiments ont été spécialement agencés pour loger les tubes d'absorption légers pour le dosage du carbone et de l'hydrogène. On donne aussi un système pratique pour éliminer les vibrations et pour fournir un montage convenable pour les balances à fil de quartz sensibles dans les laboratoires industriels. Sous une charge de 5 g, on a trouvé que la balance de Garner donne une proportionnalité rigoureuse à moins de±0,001 mg entre la torsion et le poids. Elle donne une valeur reproductible à moins de±0,26g pour une nacelle de platine de 0,4 g pour le fil de torsion soumis à un effort constant.

     

Highly diastereoselective addition of lithio vinyl sulfoxides to N-sulfinimines: an entry to enantiopure 3-sulfinyl-2,5-cis-dihydropyrroles

The addition of enantiopure alpha-metalated vinyl and dienyl sulfoxides to enantiomerically pure N-sulfinimines takes place with high diastereoselectivity primarily directed by the N-sulfinimine sulfur. The resulting allylic amines have been further transformed into highly functionalized 3-sulfinyl and 3-sulfonyl 2,5- cis-dihydropyrroles by reaction with electrophiles.     

Peptide sequence determination by matrix-assisted laser desorption ionization employing a tandem double focusing magnetic—Orthogonal acceleration time-of-flight mass spectrometer

This report describes the fragmentation processes for peptides induced by collisional activation of the ¹²C isobar of matrix-assisted laser desorption ionization (MALDI)-generated pseudomolecular ions employing an EBE orthogonal acceleration time-of-flight mass spectrometer and using xenon as the collision gas at a laboratory collision energy of 800 eV. These MALDI-collision-induced dissociation (CID) spectra are shown to provide sequence information of comparable quality to those obtained by using high energy CID conditions with liquid secondary ionization mass spectrometry on a four-sector tandem instrument. Peptide sequencing via MALDI-CID is demonstrated on three tryptic peptides obtained from a bacterial protein (P450 isozyme) of unknown sequence. Sensitivity is shown to be at the 1 pmol level for standard peptides.     

Transient excited-state absorption and gain spectroscopy of a two-photon absorbing probe with efficient superfluorescent properties

The synthesis, linear photophysical properties, two-photon absorption (2PA), excited-state transient absorption, and gain spectroscopy of a new fluorene derivative tert-butyl 4,4'-(4,4' (1E,1'E)-2,2'-(9,9-bis(2- (2-ethoxyethoxy)ethyl)-9H-fluorene-2,7-diyl)bis(ethene-2,1-diyl)bis(4,1 phenylene)]dipiperazine-1-carboxylate (1) are reported. The steady-state linear absorption and fluorescence spectra, along with excitation anisotropy, fluorescence lifetimes, and photochemical stability of 1 were investigated in a number of organic solvents at room temperature. The 2PA spectra of 1 with a maximum cross-section of ~ 300 GM were obtained with a 1 kHz femtosecond laser system using open-aperture Z-scan and two-photon-induced fluorescence methods. The transient excited-state absorption (ESA) and gain kinetics of 1 were investigated by a femtosecond pump-probe methodology. Fast relaxation processes (~1-2 ps) in the gain and ESA spectra of 1 were revealed in ACN solution, attributable to symmetry-breaking effects in the first excited state. Efficient superfluorescence properties of 1 were observed in a nonpolar solvent under femtosecond excitation. One- and two-photon fluorescence microscopy imaging of HCT 116 cells incubated with probe 1 was accomplished, suggesting the potential of this new probe in two-photon fluorescence microscopy bioimaging.     

Fette und ?le

Ohne Zusammenfassung     

Microencapsulation of Bioactive Ingredients for Their Delivery into Fermented Milk Products: A Review

The popularity and consumption of fermented milk products are growing. On the other hand, consumers are interested in health-promoting and functional foods. Fermented milk products are an excellent matrix for the incorporation of bioactive ingredients, making them functional foods. To overcome the instability or low solubility of many bioactive ingredients under various environmental conditions, the encapsulation approach was developed. This review analyzes the fortification of three fermented milk products, i.e., yogurt, cheese, and kefir with bioactive ingredients. The encapsulation methods and techniques alongside the encapsulant materials for carotenoids, phenolic compounds, omega-3, probiotics, and other micronutrients are discussed. The effect of encapsulation on the properties of bioactive ingredients themselves and on textural and sensory properties of fermented milk products is also presented.