Analysis of N-acylhomoserine lactones after alkaline hydrolysis and anion-exchange solid-phase extraction by capillary zone electrophoresis-mass spectrometry

A quantitative, specific, and sensitive method for the determination of N-acylhomoserine lactones (HSLs - a group of bacterial semiochemicals) in the form of their hydrolysis products (N-acylhomoserines, HSs) is presented. Real samples were analyzed by capillary zone electrophoresis-mass spectrometry (CZE-MS) after alkaline lactonolysis and extraction by mixed-mode anion-exchange solid-phase extraction. The presented cleanup significantly speeds up the HSL extraction procedure, strongly reduces sample consumption, and is more selective compared to the commonly used liquid/liquid extraction. Completeness of the hydrolysis reaction was examined by nuclear magnetic resonance spectroscopy. This CZE-MS method complements recently published capillary separation techniques (nano liquid chromatography-MS, partial-filling micellar electrokinetic chromatography-MS, gas chromatography-MS) and provides a possibility to differentiate quantitatively between the homoserines (as naturally occurring degradation products) besides the intact homoserine lactones. The method was found to be quantitative down to a concentration of 0.05 microg/mL (limit of quantification), while the limit of detection was determined with 0.01 microg/mL - sufficient for the analysis of culture supernatants.     

Kinetic Modeling of Plasma Methane Conversion Using Gliding Arc

Plasma methane (CH4) conversion in gliding arc discharge was examined. The result data of experiments regarding the performance of gliding arc discharge were presented in this paper. A simulation which is consisted some chemical kinetic mechanisms has been provided to analyze and describe the plasma process. The effect of total gas flow rate and input frequency refers to power consumption have been studied to evaluate the performance of gliding arc plasma system and the reaction mechanism of decomposition.Experiment results indicated that the maximum conversion of CH4 reached 50% at the total gas flow rate of 1 L/min. The plasma reaction was occurred at the atmospheric pressure and the main products were C (solid), hydrogen, and acetylene (C2H2). The plasma reaction of methane conversion was exothermic reaction which increased the product stream temperature around 30～50℃.     

Water‐Soluble Triarylborane Chromophores for One‐ and Two‐Photon Excited Fluorescence Imaging of Mitochondria in Cells

Three water‐soluble tetracationic quadrupolar chromophores comprising two three‐coordinate boron π‐acceptor groups bridged by thiophene‐containing moieties were synthesised for biological imaging applications. Compound 3 containing the bulkier 5‐(3,5‐Me₂C₆H₂)‐2,2′‐(C₄H₂S)₂‐5′‐(3,5‐Me₂C₆H₂) bridge is stable over a long period of time, exhibits a high fluorescence quantum yield and strong one‐ and two‐photon absorption (TPA), and has a TPA cross section of 268 GM at 800 nm in water. Confocal laser scanning fluorescence microscopy studies in live cells indicated localisation of the chromophore at the mitochondria; moreover, cytotoxicity measurements proved biocompatibility. Thus, chromophore 3 has excellent potential for one‐ and two‐photon‐excited fluorescence imaging of mitochondrial function in cells.     

Propagation of a femtosecond pulse in a microresonator visualized in time

A noninvasive pulse-tracking technique has been exploited to observe the time-resolved motion of an ultrashort light pulse within an integrated optical microresonator. We follow a pulse as it completes several round trips in the resonator, directly mapping the resonator modes in space and time. Our time-dependent and phase-sensitive measurement provides direct access to the angular group and phase velocity of the modes in the resonator. From the measurement the coupling constants between the access waveguides and the resonator are retrieved while at the same time the loss mechanisms throughout the structure are directly visualized.     

Analysis of N-acyl-L-homoserine lactones produced by Burkholderia cepacia with partial filling micellar electrokinetic chromatography--electrospray ionization-ion trap mass spectrometry

A method for the analysis of N-acyl-L-homoserine lactones (AHLs) with micellar electrokinetic chromatography coupled to electrospray ionization-ion trap mass spectrometry, combining the flexibility of capillary electrophoresis with the unmatched structural information provided by mass spectrometry is presented. Different surfactants were evaluated, with sodium dodecyl sulfate (SDS) yielding the best results considering sensitivity and flexibility. We examined the interaction of AHLs with the SDS micelles at different analysis conditions and applied the optimized method to the analysis of a real bacterial sample. Two AHLs from Burkholderia cepacia colonizing the rhizosphere of traditional Indian rice cultivars could be unambiguously determined in an ethyl acetate extract with high resolution flexibility.     

Cationic Titanocene(III) Complexes for Catalysis in Single‐Electron Steps

By exploiting solvent and anion effects, [Cp₂Ti]⁺ complexes for atom‐economical catalysis in single‐electron steps were developed and applied for the first time. These complexes constitute remarkably stable and active catalysts for radical arylations. The reaction kinetics and catalyst composition were studied by cyclic voltammetry and in situ IR spectroscopy.     

Molecular distribution of some commercial nonylphenol ethoxylates using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Nonylphenol ethoxylates (NPEs) belong to a group of nonionic surfactants that are collectively referred to as alkylphenol ethoxylates (APEs). APEs find widespread use in heavy-duty commercial and household cleaning formulations, shampoos, and industrial processing, i.e. textile manufacture. Their environmental impact depends on the molecular distribution and the extent of their biodegradation in municipal sewage systems, waterways and rivers. We have established two sample preparation methods that have enabled the determination of the molecular distributions of six commercial nonylphenol ethoxylates using matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS). In both methods, alpha-cyano-4-hydroxycinnamic acid, dissolved in acetonitrile/tetrahydrofuran, was used as the matrix. In one set of experiments, the NPEs were dissolved in an acetonitrile/tetrahydrofuran solvent system prior to mixing with the matrix solution, and the resulting MALDI-TOF mass spectra produced mostly sodiated molecules [M + Na](+). The NPEs, all having the formula 4-(C(9)H(19))-C(6)H(4)-(OCH(2)CH(2))(n)-OH, are Surfonic (R)N-95, N-100, N-102, N-120, N-150 and N-300. Surfonic N-95 and N-100 gave n values of 5-20; Surfonic N-102, N-120, N-150, and N-300 gave n values of 5-21, 5-22, 8-25 and 15-40, respectively. In order to develop a sample preparation method that could be used with less polar NPEs, we dissolved the NPEs (except N-300) in pentane prior to mixing with the matrix solution, and found that the MALDI spectral quality was unaffected by the solvent systems. Copyright 1999 John Wiley & Sons, Ltd.     

Modified,Amorphous Titania—A Hybrid Semiconductor for Detoxification and Current Generation by Visible Light

Amorphous, microporous TiO ₂ hybrid semiconductors modified with transition metals induce generation of a photocurrent and photocatalytic degradation of the water contaminant 4-chlorophenol through photoinduced charge separation (the postulated mechanism is shown in the picture, Ar=4-ClC₆H₄). In contrast to the previously known crystalline titania photocatalysts, which are active only when excited with UV light, the amorphous semiconductors modified with platinum, rhodium, and gold chloride enable both processes also with visible light.