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TOF Mass Spectrometry (tof + mass_spectrometry)
Selected AbstractsPhotoionization studies on various quinones by an infrared laser desorption/tunable VUV photoionization TOF mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2008Yang Pan Abstract Photoionization and dissociative photoionization characters of six quinones, including 1,2-naphthoquinone (1,2-NQ), 1,4-naphthoquinone (1,4-NQ), 9,10-phenanthroquinone (PQ), 9,10-anthraquinone (AQ), benz[a]- anthracene-7,12-dione (BAD) and 1,2-acenaphthylenedione (AND) have been studied with an infrared laser desorption/tunable synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (IR LD/VUV PIMS) technique. Mass spectra of these compounds are obtained at different VUV photon energies. Consecutive losses of two carbon monoxide (CO) groups are found to be the main fragmentation pathways for all the quinones. Detailed dissociation processes are discussed with the help of ab initio B3LYP calculations. Ionization energies (IEs) of these quinones and appearance energies (AEs) of major fragments are obtained by measuring the photoionization efficiency (PIE) spectra. The experimental results are in good agreement with the theoretical data. Copyright © 2008 John Wiley & Sons, Ltd. [source] Accessible proteomics space and its implications for peak capacity for zero-, one- and two-dimensional separations coupled with FT-ICR and TOF mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2006Jennifer L. Frahm The number and wide dynamic range of components found in biological matrixes present several challenges for global proteomics. In this perspective, we will examine the potential of zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) separations coupled with Fourier-transform ion cyclotron resonance (FT-ICR) and time-of-flight (TOF) mass spectrometry (MS) for the analysis of complex mixtures. We describe and further develop previous reports on the space occupied by peptides, to calculate the theoretical peak capacity available to each separations-mass spectrometry method examined. Briefly, the peak capacity attainable by each of the mass analyzers was determined from the mass resolving power (RP) and the m/z space occupied by peptides considered from the mass distribution of tryptic peptides from National Center for Biotechnology Information's (NCBI's) nonredundant database. Our results indicate that reverse-phase-nanoHPLC (RP-nHPLC) separation coupled with FT-ICR MS offers an order of magnitude improvement in peak capacity over RP-nHPLC separation coupled with TOF MS. The addition of an orthogonal separation method, strong cation exchange (SCX), for 2D LC-MS demonstrates an additional 10-fold improvement in peak capacity over 1D LC-MS methods. Peak capacity calculations for 0D LC, two different 1D RP-HPLC methods, and 2D LC (with various numbers of SCX fractions) for both RP-HPLC methods coupled to FT-ICR and TOF MS are examined in detail. Peak capacity production rates, which take into account the total analysis time, are also considered for each of the methods. Furthermore, the significance of the space occupied by peptides is discussed. Copyright © 2006 John Wiley & Sons, Ltd. [source] Automated software-guided identification of new buspirone metabolites using capillary LC coupled to ion trap and TOF mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2006Anabel S. Fandiño Abstract The identification and structure elucidation of drug metabolites is one of the main objectives in in vitro ADME studies. Typical modern methodologies involve incubation of the drug with subcellular fractions to simulate metabolism followed by LC-MS/MS or LC-MSn analysis and chemometric approaches for the extraction of the metabolites. The objective of this work was the software-guided identification and structure elucidation of major and minor buspirone metabolites using capillary LC as a separation technique and ion trap MSn as well as electrospray ionization orthogonal acceleration time-of-flight (ESI oaTOF) mass spectrometry as detection techniques. Buspirone mainly underwent hydroxylation, dihydroxylation and N -oxidation in S9 fractions in the presence of phase I co-factors and the corresponding glucuronides were detected in the presence of phase II co-factors. The use of automated ion trap MS/MS data-dependent acquisition combined with a chemometric tool allowed the detection of five small chromatographic peaks of unexpected metabolites that co-eluted with the larger chromatographic peaks of expected metabolites. Using automatic assignment of ion trap MS/MS fragments as well as accurate mass measurements from an ESI oaTOF mass spectrometer, possible structures were postulated for these metabolites that were previously not reported in the literature. Copyright © 2006 John Wiley & Sons, Ltd. [source] Fabrication of Aromatic-Aliphatic Aminoketone Polymers with Terminal Fluorine GroupsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 14 2010Susann Anders Abstract A procedure for synthesis aromatic-aliphatic PAK, completely functionalized with p- fluorophenyl terminal groups, is presented. This synthesis uses the nucleophilic aromatic substitution of DFB with various secondary aliphatic diamines [CH3NH(CH2)mNHCH3] (m,=,3, 6, and 8) and cesium fluoride as the base catalyst in the melt. The linearity and the complete functionalization of the PAK compounds with p- fluorophenyl terminal groups are demonstrated with the aid of MALDI TOF mass spectrometry. PAK compounds are semi-crystalline as shown by WAXS and DSC measurements. The degree of crystallinity ranges between 2 and 25%. Nucleophilic aromatic substitution reactions in the fluorine end groups are demonstrated by reaction of PAK (m,=,6) with the strong S- nucleophile mercaptoacetic acid. [source] Identification of human whole saliva protein components using proteomicsPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 4 2004Rui Vitorino Abstract The determination of salivary biomarkers as a means of monitoring general health and for the early diagnosis of disease is of increasing interest in clinical research. Based on the linkage between salivary proteins and systemic diseases, the aim of this work was the identification of saliva proteins using proteomics. Salivary proteins were separated using two-dimensional (2-D) gel electrophoresis over a pH range between 3,10, digested, and then analyzed by matrix assisted laser desorption/ionization-time of flight (MALDI-TOF)-TOF mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Proteins were identified using automated MS and MS/MS data acquisition. The resulting data were searched against a protein database using an internal Mascot search routine. Ninety spots give identifications with high statistical reliability. Of the identified proteins, 11 were separated and identified in saliva for the first time using proteomics tools. Moreover, three proteins that have not been previously identified in saliva, PLUNC, cystatin A, and cystatin B were identified. [source] Structure of the putative thioesterase protein TTHA1846 from Thermus thermophilus HB8 complexed with coenzyme A and a zinc ionACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2009Toshiaki Hosaka TTHA1846 is a conserved hypothetical protein from Thermus thermophilus HB8 with a molecular mass of 15.1,kDa that belongs to the thioesterase superfamily (Pfam 03061). Here, the 1.9,Å resolution crystal structure of TTHA1846 from T. thermophilus is reported. The crystal structure is a dimer of dimers. Each subunit adopts the so-called hot-dog fold composed of five antiparallel ,-strands flanked on one side by a rather long ,-helix and shares structural similarity to a number of thioesterases. Unexpectedly, TTHA1846 binds one metal ion and one ligand per subunit. The ligand density was modelled as coenzyme A (CoA). Its structure was confirmed by MALDI,TOF mass spectrometry and electron-density mapping. X-ray absorption fine-structure (XAFS) measurement of the crystal unambiguously characterized the metal ion as zinc. The zinc ion is tetrahedrally coordinated by the side chains of Asp18, His22 and Glu50 and the CoA thiol group. This is the first structural report of the interaction of CoA with a zinc ion. From structural and database analyses, it was speculated that the zinc ion may play an inhibitory role in the enzymatic activity. [source] Rapid and specific high-performance liquid chromatography for the in vitro quantification of d -Lys6,GnRH in a microemulsion-type formulation in the presence of peptide oxidation productsBIOMEDICAL CHROMATOGRAPHY, Issue 2 2010Alexandra P. Kafka Abstract A high-performance liquid chromatography (HPLC) method for assay of d -Lys6,GnRH contained in a microemulsion-type formulation is described. The peptide is extracted from the microemulsion matrix and quantified using a two-step gradient method. Separation from microemulsion compounds and potential peptide oxidation products was achieved on a Jupiter C18 column at 40°C, using a gradient of 10,35% CH3CN for peptide elution. The correlation of peak intensity measured at 220 nm and peptide concentration was linear over the range 2.5,60 µg/mL with a correlation coefficient of 0.9997 and a y -intercept not significantly different from zero (p > 0.05). Intraday and interday variability of the assay was less than 5% for multiple injections of samples containing 7.5, 30 and 60 µg/mL. The lower limit of quantitation was calculated to be 0.38 µg/mL, and the lower limit of detection was 0.13 µg/mL. The assay was applied to samples that were stressed under physiological conditions (37°C, pH 7.4) over 4 days. Three degradation peaks were well resolved from the parent peptide, demonstrating the selectivity of the assay. Off-line MALDI TOF mass spectrometry was applied to identify these degradation species as oxidation products of the peptide. Copyright © 2009 John Wiley & Sons, Ltd. [source] Degree of blockiness of amide groups as indicator for difference in physical behavior of amidated pectinsBIOPOLYMERS, Issue 1 2006Stéphanie E. Guillotin Abstract Thickening and gelling properties of commercial amidated pectins depend on the degree of amidation and methyl-esterification, but also the distribution of these groups is of great importance. Methods have been developed during the last few years to determine the distribution of methyl esters over the pectic backbone. We applied the strategies developed for the analysis of high methyl-esterified pectins for studying the distribution of amide groups in amidated pectins. Low methyl-esterified amidated (LMA) pectins were digested before and after removal of methyl esters by an endo -polygalacturonase to determine the degree of blockiness of the substituents. The nature of the substituents (amide groups compared to methyl esters) did not modify the behavior of the enzyme. Oligomers released were separated by using high-performance anion exchange chromatography and pulsed amperometric detection (HPAEC,PAD) at pH 5. Fractions collected after on-line desalting were identified by using MALDI,TOF mass spectrometry. Oligomers were found to elute from the column as a function of their total charge. For the same overall charge and size, oligomers with methyl esters eluted before oligomers with amide groups. Both amide groups and methyl esters of the LMA pectins studied were found to be semirandomly distributed over the pectic backbone, but this may vary according to the amidation process used. © 2006 Wiley Periodicals, Inc. Biopolymers 82: 29,37, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] | ||||||||||