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Soft Ionization (soft + ionization)
Selected AbstractsMultiple Soft Ionization of Gas-Phase Proteins and Swift Backbone Dissociation in Collisions with ,99,eV Electrons,ANGEWANDTE CHEMIE, Issue 8 2010Roman Unerwartet: Elektronen mit einer Energie über 20,eV können Polypeptide mehrmals ionisieren (siehe Bild), ohne dabei die Primär- oder sogar Elemente der Tertiärstruktur zu zerstören. Durch gleichzeitige elektronische Anregung lassen sich Rückgratbindungen rasch spalten, wobei schwache Molekül-Molekül-Bindungen intakt bleiben. Dieses ,sanfte Fragmentieren" sollte eine genaue Charakterisierung der Struktur von Proteinkomplexen ermöglichen. [source] A silica-based monolithic column in capillary HPLC and CEC coupled with ESI-MS or electrospray-atmospheric-pressure laser ionization-MSELECTROPHORESIS, Issue 21 2005Stefan Droste Abstract We describe the successful coupling of CEC and capillary HPLC with the recently developed atmospheric-pressure laser ionization (APLI) method. APLI is suitable for selectively and sensitively ionizing nonpolar aromatic compounds at ambient pressure for subsequent mass-selective detection. The polycyclic aromatic hydrocarbons used as analytes are first separated either by CEC on a silica-based monolithic column or by capillary HPLC. The eluent, along with a sheath flow, is volatilized by microelectrospray and then selectively ionized by excimer laser (KrF*) radiation via two-photon excitation. A QTOF-MS is used as mass-selective detector. This interface combination makes soft ionization of thermally labile nonpolar aromatic analytes possible. [source] Detection and characterization of variant and modified structures of proteins in blood and tissues by mass spectrometryMASS SPECTROMETRY REVIEWS, Issue 5 2006Akira Shimizu Abstract Some variant proteins cause diseases, and some diseases result in increases of proteins with abnormally modified structures. The detection, characterization, and estimation of the relative amounts of protein variants and abnormally modified proteins are important for clinical diagnosis and for elucidation of the mechanisms of the pathogenesis of diseases. Analysis of the covalent structures of proteins using matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF-MS) and liquid chromatography-electrospray ionization MS (LC-ESI-MS), which had been developed by the early 1990s, have largely replaced analyses by conventional protein chemistry. Here, we review the detection and characterization of hemoglobin variants, HbA1c measurement, detection of carbohydrate-deficient transferrin, and identification of variants of transthyretin (TTR) and Cu/Zn-superoxide dismutase (SOD-1) using soft ionization MS. We also propose the diagnostic application of the signals of modified forms of TTR, that is, S-sulfonated TTR and S-homocysteinyl TTR. The relative peak height ratio of the abnormal/normal components gives valuable information about the instability of variants and enables the detection of unstable Hb subunits or thalassemia heterozygotes. We found unique modified structures of TTR that suggested changes in amyloid fibrils. © 2006 Wiley Periodicals, Inc. [source] Observation of vanadyl porphyrins and sulfur-containing vanadyl porphyrins in a petroleum asphaltene by atmospheric pressure photonionization Fourier transform ion cyclotron resonance mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2008Kuangnan Qian Vanadyl (VO) porphyrins and sulfur-containing vanadyl (VOS) porphyrins of a wide carbon number range (C26 to C52) and Z-number range (,28 to ,54) were detected and identified in a petroleum asphaltene by atmospheric pressure photonionization (APPI) and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). APPI provides soft ionization of asphaltene molecules (including VO and VOS porphyrins), generating primarily molecular ions (M+.). The ultra-high mass resolving power (m/,mFWHM ,500,K) of FTICR-MS enabled resolution and positive identification of elemental formulae for the entire family of VO and VOS porphyrins in a complicated asphaltene matrix. Deocophylerythro-etioporphyrin (DPEP) is found to be the most prevalent structure, followed by etioporphyrins (etio)- and rhodo (benzo)-DPEP. The characteristic Z-distribution of VO porphyrins suggests benzene and naphthene increment in the growth of porphyrin ring structures. Bimodal carbon number distributions of VO porphyrins suggest possible different origins of low and high molecular weight species. To our knowledge, the observation of VOS porphyrins in a petroleum product has not previously been reported. The work is also the first direct identification of the entire vanadyl porphyrin family by ultra-high resolution mass spectrometry without chromatographic separation or demetallation. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||