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Mass Spectrometry Measurements (mass + spectrometry_measurement)
Selected AbstractsMetabolic profiling as a tool for revealing Saccharomyces interactions during wine fermentationFEMS YEAST RESEARCH, Issue 1 2006Kate S. Howell Abstract The multi-yeast strain composition of wine fermentations has been well established. However, the effect of multiple strains of Saccharomyces spp. on wine flavour is unknown. Here, we demonstrate that multiple strains of Saccharomyces grown together in grape juice can affect the profile of aroma compounds that accumulate during fermentation. A metabolic footprint of each yeast in monoculture, mixed cultures or blended wines was derived by gas chromatography , mass spectrometry measurement of volatiles accumulated during fermentation. The resultant ion spectrograms were transformed and compared by principal-component analysis. The principal-component analysis showed that the profiles of compounds present in wines made by mixed-culture fermentation were different from those where yeasts were grown in monoculture fermentation, and these differences could not be produced by blending wines. Blending of monoculture wines to mimic the population composition of mixed-culture wines showed that yeast metabolic interactions could account for these differences. Additionally, the yeast strain contribution of volatiles to a mixed fermentation cannot be predicted by the population of that yeast. This study provides a novel way to measure the population status of wine fermentations by metabolic footprinting. [source] Investigation on Aggregate Formation of Ionic LiquidsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2005Sandra Dorbritz Abstract Understanding the behavior of ionic liquids on the molecular level is essential for explaining solubilizing or reaction processes, including catalytic reactions in ionic liquids or with ionic liquids as co-solvent. Using mass spectrometry techniques it is possible to characterize their aggregate formation behavior, which depends on the used solvent. With increasing polarity of the solvent and decreasing ionic liquid concentration, the size of the formed aggregates decreases. From conductivity measurement curves "critical aggregate concentrations" were calculated, which confirm the results of mass spectrometry measurements. Addition of ionic liquids increases the solubility of acetophenone in water. This effect can be explained by the aggregate formation ability of ionic liquids. The findings can be used to explain the outstanding solubility and solvation properties of ionic liquids. [source] Assessment of the repeatability and reproducibility of hydrogen/deuterium exchange mass spectrometry measurements,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2008William Burkitt A system to perform automated hydrogen/deuterium exchange mass spectrometry measurements was constructed using an XYZ robotic autosampler that was capable of performing solvent manipulations and a 4.7 T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The system included features such as the first demonstration of a ,dual column' high-performance liquid chromatography (HPLC) setup, and a novel digestion strategy. The performance of the system, in terms of the repeatability and reproducibility of the measurement of protein hydrogen/deuterium exchange, was assessed over a 2-month period. The sensitivity of the measurement of hydrogen exchange towards several parameters was assessed, which allowed their impact on the reproducibility to be discussed. The parameters assessed were the temperature of the HPLC columns and switching valves, the temperature of the quench solutions, the pH of the mobile phase, the pH of the quenched solution, the acid used in the mobile phase and the analytical column used. Copyright © 2008 John Wiley & Sons, Ltd. [source] Structural analysis of secondary ions by post-source decay in time-of-flight secondary ion mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2006David Touboul Tandem mass spectrometry measurements have been achieved using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and a post source decay (PSD)-like method. The performance of the method has been demonstrated on model molecules with well-known fragmentation pathways. Several lipids have been fragmented including the phosphocholine ion, phosphatidylcholines, cholesterol and vitamin E. Pure samples were analyzed, and the results compared with those obtained with the same compounds on a quadrupole-TOF hybrid mass spectrometer. Then, the structures of some lipids which are currently observed in the TOF-SIMS imaging of mammalian tissue sections were verified. Copyright © 2006 John Wiley & Sons, Ltd. [source] Phosphopeptide analysis by positive and negative ion matrix-assisted laser desorption/ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2001Katharina Janek This article describes a simple procedure for the detection of phosphorylated peptides by comparable positive and negative ion mode matrix-assisted laser desorption/ionization mass spectrometry measurements. Based on studies with phosphorylated peptides (EAIXAAPFAK, X,=,pS, pT, pY) and their corresponding non-phosphorylated analogs, it was found that phosphopeptides, which are characterized by a low ionization efficiency in the positive ion mode, exhibit drastically increased signal intensities in the negative ion mode compared to their non-phosphorylated analogs. The effect was successfully used to identify phosphorylated sequences of the commonly used phosphoprotein standards, protein kinase A and ,-casein, by peptide mass fingerprint analyses of the corresponding Lys C and trypsin digests using both (positive and negative) ion modes. The comparison of positive and negative ion spectra of a given protein digest (relative intensity[M,,,H],/relative intensity[M,+,H]+) can be used to identify any phosphopeptides present which may then be separated and analyzed further. Copyright © 2001 John Wiley & Sons, Ltd. [source] Monitoring the Formation of Coordination Complexes Using Electrospray Mass SpectrometryCHEMISTRY - AN ASIAN JOURNAL, Issue 5 2009Jennifer Abstract Linked-in: The rigid Schiff-base ligand cis,trans -1,3,5-tris(pyridine-2-carboxaldimino) cyclohexane (ttop) is synthesized, and its complexation to copper(II) salts at a range of stoichiometries is investigated crystallographically by using electrospray mass spectrometry. Further, in-situ mass spectrometry measurements allow the stepwise construction of the complexes to be observed. cis,trans -1,3,5-Triaminocyclohexane (trans -tach) has been shown to be an excellent ligand in the synthesis of discrete complexes, molecular clusters, and infinite architectures. Herein, we report the Schiff-base derivitization of trans -tach to form cis,trans -1,3,5- tris (pyridine-2-carboxaldimino) cyclohexane (ttop), and the complexation of this ligand with copper(II) salts. The complexation reaction leads to the crystallization of transition-metal complexes with nuclearities of 1, 2, and 4, and the formation of the complexes can be followed stepwise, in real time, using electrospray mass spectrometry. [source] | ||||||||||