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Ionization Ion Trap Mass Spectrometry (ionization + ion_trap_mass_spectrometry)
Selected AbstractsOn-chip solid-phase extraction pre-concentration/focusing substrates coupled to atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry for high sensitivity biomolecule analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2009Arti Navare Atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) has proven a convenient and rapid method for ion production in the mass spectrometric (MS) analysis of biomolecules. AP-MALDI and electrospray ionization (ESI) sources are easily interchangeable in most mass spectrometers. However, AP-MALDI suffers from less-than-optimal sensitivity due to ion losses during transport from the atmosphere into the vacuum of the mass spectrometer. Here, we study the signal-to-noise ratio (S/N) gains observed when an on-chip dynamic pre-concentration/focusing approach is coupled to AP-MALDI for the MS analysis of neuropeptides and protein digests. It was found that, in comparison with conventional AP-MALDI targets, focusing targets showed (1) a sensitivity enhancement of approximately two orders of magnitude with S/N gains of 200,900 for hydrophobic substrates, and 150,400 for weak cation-exchange (WCX) substrates; (2) improved detection limits as low as 5,fmol/µL for standard peptides; (3) significantly reduced matrix background; and (4) higher inter-day reproducibility. The improved sensitivity allowed successful tandem mass spectrometric (MS/MS) sequencing of dilute solutions of a derivatized tryptic digest of a protein standard, and enabled the first reported AP-MALDI MS detection of neuropeptides from Aedes aegypti mosquito heads. Copyright © 2009 John Wiley & Sons, Ltd. [source] Applications of silver nanoparticles capped with different functional groups as the matrix and affinity probes in surface-assisted laser desorption/ionization time-of-flight and atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry for rapid analysis of sulfur drugs and biothiols in human urineRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2008Kamlesh Shrivas A strategy is presented for the analysis of sulfur drugs and biothiols using silver nanoparticles (AgNPs) capped with different functional groups as the matrix and affinity probes in surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS) and atmospheric pressure-matrix assisted laser desorption/ionization ion trap mass spectrometry (AP-MALDI-ITMS). Biothiols adsorbed on the surface of AgNPs through covalent bonding were subjected to ultraviolet (UV) radiation that enabled desorption and ionization due to the excellent photochemical property of NPs. The proposed method has been successfully applied for the determination of cysteine and homocysteine in human urine samples using an internal standard. The limit of detection (LOD) and limit of quantification (LOQ) for cysteine and homocysteine in urine sample are 7 and 22,nM, respectively, with a relative standard deviation (RSD) of <10%. The advantages of the present method compared with the methods reported in the literature for biothiol analysis are simplicity, rapidity and sensitivity without the need for time-consuming separation and tedious preconcentration processes. Additionally, we also found that the bare AgNPs can be directly used as the matrix in MALDI-TOF MS for the analysis of sulfur drugs without the addition of an extra proton source. Copyright © 2008 John Wiley & Sons, Ltd. [source] Atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry of sulfonic acid derivatized tryptic peptidesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2001T. Keough Atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) and ion trap mass spectrometry have been used to study the fragmentation behavior of native peptides and peptide derivatives prepared for de novo sequencing applications. Sulfonic acid derivatized peptides were observed to fragment more extensively and up to 28 times more efficiently than the corresponding native peptides. Tandem mass spectra of native peptides containing aspartic or glutamic acids are dominated by cleavage on the C-terminal side of the acidic residues. This significantly limits the amount of sequence information that can be derived from those compounds. The MS/MS spectra of native tryptic peptides containing oxidized Met residues show extensive loss of CH3SOH and little sequence-specific fragmentation. On the other hand, the tandem mass spectra of derivatized peptides containing Asp, Glu and oxidized Met show much more uniform fragmentation along the peptide backbone. The AP-MALDI tandem mass spectra of some derivatized peptides were shown to be qualitatively very similar to the corresponding vacuum MALDI postsource decay mass spectra, which were obtained on a reflector time-of-flight instrument. However, the ion trap mass spectrometer offers several advantages for peptide sequencing relative to current reflector time-of-flight instruments including improved product ion mass measurement accuracy, improved precursor ion selection and MSn. These latter capabilities were demonstrated with solution digests of model proteins and with in-gel digests of 2D-gel separated proteins. Copyright © 2001 John Wiley & Sons, Ltd. [source] Determination of triclosan metabolites by using in-source fragmentation from high-performance liquid chromatography/negative atmospheric pressure chemical ionization ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2010Jian-lin Wu Triclosan is a widely used broad-spectrum antibacterial agent that acts by specifically inhibiting enoyl,acyl carrier protein reductase. An in vitro metabolic study of triclosan was performed by using Sprague-Dawley (SD) rat liver S9 and microsome, while the invivo metabolism was investigated on SD rats. Twelve metabolites were identified by using in-source fragmentation from high-performance liquid chromatography/negative atmospheric pressure chemical ionization ion trap mass spectrometry (HPLC/APCI-ITMS) analysis. Compared to electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS) that gave little fragmentation for triclosan and its metabolites, the in-source fragmentation under APCI provided intensive fragmentations for the structural identifications. The invitro metabolic rate of triclosan was quantitatively determined by using HPLC/ESI-ITMS with the monitoring of the selected triclosan molecular ion. The metabolism results indicated that glucuronidation and sulfonation were the major pathways of phase II metabolism and the hydroxylated products were the major phase I metabolites. Moreover, glucose, mercapturic acid and cysteine conjugates of triclosan were also observed in the urine samples of rats orally administrated with triclosan. Copyright © 2010 John Wiley & Sons, Ltd. [source] Identification of organic hydroperoxides and hydroperoxy acids in secondary organic aerosol formed during the ozonolysis of different monoterpenes and sesquiterpenes by on-line analysis using atmospheric pressure chemical ionization ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2009Marc-Christopher Reinnig On-line ion trap mass spectrometry (ITMS) enables the real-time characterization of reaction products of secondary organic aerosol (SOA). The analysis was conducted by directly introducing the aerosol particles into the ion source. Positive-ion chemical ionization at atmospheric pressure (APCI(+)) ITMS was used for the characterization of constituents of biogenic SOA produced in reaction-chamber experiments. APCI in the positive-ion mode usually enables the detection of [M+H]+ ions of the individual SOA components. In this paper the identification of organic peroxides from biogenic volatile organic compounds (VOCs) by on-line APCI-ITMS is presented. Organic peroxides containing a hydroperoxy group, generated by gas-phase ozonolysis of monoterpenes (, -pinene and , -pinene) and sesquiterpenes (, -cedrene and , -copaene), could be detected via on-line APCI(+)-MS/MS experiments. A characteristic neutral loss of 34,Da (hydrogen peroxide, H2O2) in the on-line MS/MS spectra is a clear indication for the existence of an organic peroxide, containing a hydroperoxy functional group. Copyright © 2009 John Wiley & Sons, Ltd. [source] Electrospray ionization ion trap mass spectrometry for structural characterization of oligosaccharides derivatized with 2-aminobenzamideRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2005Willy Morelle The use of electrospray ionization (ESI) quadrupole ion trap mass spectrometry and reversed-phase high-performance liquid chromatography (HPLC) for the characterization of 2-aminobenzamide (2AB)-labeled oligosaccharides and N-linked protein oligosaccharide mixtures is described. The major signals were obtained under these conditions from the [M+Na]+ ions for all 2AB-derivatized oligosaccharides. Under collision-induced dissociation, sodiated molecular species generated in the ESI mode yield simple and predictable mass spectra. Tandem mass spectrometry (MS/MS) experiments with orders higher than two offer a number of ways to enhance MS/MS spectra and to derive information not present in MS and MS2 spectra. Information on composition, sequence, branching and, to some extent, interglycosidic linkages can be deduced from fragments resulting from the cleavage of glycosidic bonds and from weak cross-ring cleavage products. Reversed-phase HPLC and derivatization by reductive amination using 2-aminobenzamide were finally applied to characterize a glycan pool enzymatically released from glycoproteins. Copyright © 2005 John Wiley & Sons, Ltd. [source] A computational and experimental study of cation affinity (Na+) of nucleobases and modified nucleobases by electrospray ionization ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2004S. Rochut Gas-phase Na+ affinities of modified or unmodified nucleobases were determined theoretically at the density functional theory level, with the B3P86 functional and the 6,31,+,G* basis set, and experimentally using electrospray ionization ion trap mass spectrometry (ESI-ITMS) and the kinetic method. For the calculations, the sodium cation affinities (SCA) were obtained from energies of the most stable complexes of the free nucleobases. Experimentally and theoretically relative scales of cation affinities were determined using eight modified and unmodified nucleobases and a very good agreement was obtained. Copyright © 2004 John Wiley & Sons, Ltd. [source] Analysis of protein ions in the range 3000,12000,Th under partial (no discharge) atmospheric pressure chemical ionization conditions using ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2002Simone Cristoni A new approach, based on the use of atmospheric pressure chemical ionization ion trap mass spectrometry (APCI-ITMS), but without a corona discharge, was investigated for application to creating and monitoring protein ions. It must be emphasized that APCI is not usually used in protein analysis. In order to verify the applicability of the proposed method to the analysis of proteins, two standard proteins (horse cytochrome c and horse myoglobin) were analyzed. A mixture of the two proteins was also analyzed showing that this novel approach, based on the use of APCI, can be used in the analysis of protein mixtures. Copyright © 2002 John Wiley & Sons, Ltd. [source] Determination of the disulfide bond pattern of the endogenous and recombinant angiogenesis inhibitor endostatin by mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2001Harald John Endostatin, a C-terminal fragment of collagen XVIII, is a promising protein drug which is in development for cancer therapy due to its anti-angiogenic activity. Although several endogenous molecular forms of human endostatin differing in their N-terminal length and their post-translational modifications (18.5,22,kDa) have been discovered, only one recombinant form of 20,kDa is used in clinical trials. This protein, recombinantly expressed in Pichia pastoris, contains four cysteines forming two disulfide bonds (Cys1-Cys4 and Cys2-Cys3). In contrast, there are conflicting data about the disulfide pattern of endogenous material. This report presents the disulfide analyses of both the endogenous circulating endostatins isolated from human hemofiltrate and the recombinant protein. The determination of the disulfide pattern was performed by Edman degradation, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and electrospray ionization ion trap mass spectrometry (ESI-ITMS) performed in the off-line nanospray mode. All native and recombinant endostatins exhibited a Cys1-Cys4 (Cys162 -Cys302) and Cys2-Cys3 (Cys264 -Cys294) linkage. For a clear discussion of fragmented disulfide-bridged peptide chains obtained from MSn experiments, a modified general nomenclature is proposed. Copyright © 2001 John Wiley & Sons, Ltd. [source] LC-MS characterization of efficacy substances in serum of experimental animals treated with Sophora flavescens extractsBIOMEDICAL CHROMATOGRAPHY, Issue 6 2007Guan Ye Abstract Anti-DHBV (duck hepatitis B virus) activity was found in the aqueous extracts of Sophora flavescens Ait. in vivo. Liquid chromatography/electrospray ionization ion trap mass spectrometry was applied to characterize the components in duck serum after oral administration of S. flavescens extract. Oxymatrine (1), sophoranol (2), sophoridine (3) and matrine (4) were identified in the serum. Further research on the four compounds was evaluated for their antiviral activity against HBV (hepatitis B virus) in cell culture. The results suggested that oxymatrine, sophoranol and matrine were the efficacy substances for anti-HBV activity in aqueous extracts of S. flavescens Ait. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||