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Ion Cyclotron Resonance (ion + cyclotron_resonance)
Kinds of Ion Cyclotron Resonance Terms modified by Ion Cyclotron Resonance Selected AbstractsMalondialdehyde modification of myelin oligodendrocyte glycoprotein leads to increased immunogenicity and encephalitogenicityEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 7 2007Maja Wållberg Abstract Self proteins may become autoantigenic through structural modification. We studied malondialdehydation of recombinant rat (rr) myelin oligodendrocyte glycoprotein (MOG), an autoantigen in multiple sclerosis. Malondialdehyde (MDA) modification changed protein weight and charge, the location of these adducts being mapped by Fourier transform ion cyclotron resonance. Molecular modelling revealed significant differences in the MDA-rrMOG three-dimensional structure. DBA/1 mice immunised with MDA-rrMOG developed greater proliferative responses and more severe experimental autoimmune encephalomyelitis than mice immunised with unmodified rrMOG. MDA-rrMOG was taken up more effectively by antigen-presenting cells (APC), at least partially through scavenger receptors. Exposure to MDA-rrMOG led to increased expression of IL-23, IL-12 and IL-12R, indicating a role not only for increased antigen uptake but also for activation of APC. We thus provide biochemical, structural, immunological and clinical data that suggest that the post-translationally modified form of this myelin autoantigen is a more relevant form of the molecule. [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] Proteomics by FTICR mass spectrometry: Top down and bottom upMASS SPECTROMETRY REVIEWS, Issue 2 2005Bogdan Bogdanov Abstract This review provides a broad overview of recent Fourier transform ion cyclotron resonance (FTICR) applications and technological developments relevant to the field of proteomics. Both the "bottom up" (peptide level) and "top down" (intact protein level) approaches are discussed and illustrated with examples. "Bottom up" topics include peptide fragmentation, the accurate mass and time (AMT) tag approach and dynamic range extension technology, aspects of quantitative proteomics measurements, post-translational modifications, and developments in FTICR operation software focused on peptide and protein identification. Topics related to the "top down" approach include various aspects of high mass measurements, protein tandem mass spectrometry, methods for the study of protein conformations, and protein complexes as well as advanced technologies that may become of practical utility in the coming years. Finally, early examples of the integration of both FTICR approaches to biomedical proteomics applications are presented, along with an outlook for future directions. © 2004 Wiley Periodicals, Inc., Mass Spec Rev 24:168,200, 2005 [source] Comprehensive characterization of marine dissolved organic matter by Fourier transform ion cyclotron resonance mass spectrometry with electrospray and atmospheric pressure photoionizationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2010Juliana D'Andrilli We compare the ultrahigh resolution 9.4,T Fourier transform ion cyclotron resonance (FT-ICR) mass spectra of marine dissolved organic matter (DOM) isolated from two sites in the Weddell Sea (Antarctica) obtained by complementary electrospray ionization (ESI) and atmospheric pressure photoionization (APPI). Ions produced by APPI extend to higher carbon unsaturation than those produced by ESI, indicated by higher double-bond equivalents (rings plus double bonds) minus oxygen (DBE-O) values, whereas ESI-generated ions are more oxygenated. Moreover, many sulfur-containing compounds were efficiently ionized by ESI but not detected by APPI. Because the mass spectra obtained by ESI and APPI are significantly different, both are necessary to obtain a more complete description of the molecular composition of marine DOM. Copyright © 2010 John Wiley & Sons, Ltd. [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] Negative ion dissociation of peptides containing hydroxyl side chainsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 2 2008Dan Pu The dissociation of deprotonated peptides containing hydroxyl side chains was studied by electrospray ionization coupled with Fourier transform ion cyclotron resonance (ESI-FTICR) via sustained off-resonance irradiation collision induced dissociation (SORI-CID). Dissociation under post-source decay (PSD) conditions was performed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF). This work included hexapeptides with one residue of serine, threonine, or tyrosine and five inert alanine residues. During SORI-CID and PSD, dissociation of [M,H], yielded c- and y-ions. Side-chain losses of formaldehyde (HCHO) from serine-containing peptides, acetaldehyde (CH3CHO) from threonine-containing peptides, and 4-methylene-2,5-cycohexadienone (C7H6O) from tyrosine-containing peptides were generally observed in the negative ion PSD and SORI-CID spectra. Side-chain loss occurs much less from tyrosine-containing peptides than from serine- and threonine-containing peptides. This is probably due to the bulky side chain of tyrosine, resulting in steric hindrance and poor geometry for dissociation reactions. Additionally, a selective cleavage leading to the elimination of the C-terminal residue from [M,H], was observed from the peptides with serine and threonine at the C-terminus. This cleavage does not occur in the dissociation of peptides with an amide group at the C-terminus or peptides with neutral or basic residues at the C-terminus. It also does not occur with tyrosine at the C-terminus. Both the C-terminal carboxylic acid group and the hydroxyl side chain of the C-terminal residue must play important roles in the mechanism of C-terminal residue loss. A mechanism involving both the C-terminal carboxylic acid group and a hydroxyl side chain of serine and threonine is proposed. Copyright © 2007 John Wiley & Sons, Ltd. [source] A new hybrid electrospray Fourier transform mass spectrometer: design and performance characteristicsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 2 2006Peter B. O'Connor A new hybrid electrospray quadrupole Fourier transform mass spectrometry (FTMS) instrument design is shown and characterized. This instrument involves coupling an electrospray source and mass-resolving quadrupole, ion accumulation, and collision cell linear ion trap system developed by MDS Sciex with a home-built ion guide and ion cyclotron resonance (ICR) cell. The iterative progression of this design is shown. The final design involves a set of hexapole ion guides to transfer the ions from the accumulation/collision trap through the magnetic field gradient and into the cell. These hexapole ion guides are separated by a thin gate valve and two conduction limits to maintain the required <10,9,mbar vacuum for FTICR. Low-attomole detection limits for a pure peptide are shown, 220,000 resolving power in broadband mode and 820,000 resolving power in narrow-band mode are demonstrated, and mass accuracy in the <2,ppm range is routinely available provided the signal is abundant, cleanly resolved, and internally calibrated. This instrument design provides high experimental flexibility, allowing Q2 CAD, SORI-CAD, IRMPD, and ECD experiments with selected ion accumulation as well as experiments such as nozzle skimmer dissociation. Initial top-down mass spectrometry experiments on a protein is shown using ECD. Copyright © 2005 John Wiley & Sons, Ltd. [source] Continuous-flow sample introduction for field desorption/ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2004Tanner M. Schaub We introduce continuous-flow field desorption (FD) for improved spectral quality, higher sample throughput, and simpler interface to sample handlers and chromatographic equipment. A recently developed commercial FD probe with integral fused-silica capillary allows sample dosing in situ, without probe removal and reinsertion. A stable FD-generated ion current can be sustained for longer than an hour by continuous deposition of analyte solution on the FD emitter heated and at high voltage. Continuous-flow FD allows ensemble averaging of up to 100 Fourier transform ion cyclotron resonance (FT-ICR) mass spectra, in contrast to the traditional emitter dosing technique. Continuous-flow FD is amenable to interface with liquid chromatography (LC) and/or automated sample injectors. Copyright © 2004 John Wiley & Sons, Ltd. [source] Primary structural determination of N-terminally blocked peptides from the bark of Eucommia ulmoides Oliv by mass spectrometric analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2003Ren-Huai Huang Sequencing of N-terminally blocked proteins/peptides is a challenge since these molecules inhibit processing by Edman degradation. By using high accuracy Fourier transform ion cyclotron resonance (FTICR) tandem mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), the primary structures of two novel N-terminally blocked antifungal peptides (EAFP1 and EAFP2), purified from the bark of Eucommia ulmoides Oliv, have been determined. The results show that the high mass accuracy provided by FTICR mass spectrometry is effective to determine the N-terminally blocking group, and can simplify the task of spectral interpretation and improve the precision of sequence determination. The combination of MALDI-TOFMS with carboxyl peptidase Y digestion was used to determine the C-terminal 36- and 27-residue sequences of EAFP1 and EAFP2, respectively, to provide the sequence linkage information for tryptic fragments. Compared with traditional peptide chemistry the advantage of mass spectrometric techniques is their simplicity, speed and sensitivity. Copyright © 2003 John Wiley & Sons, Ltd. [source] Characterisation of combinatorial libraries of mucin-2 antigen peptides by high-resolution mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2002Emöke Windberg An epitope motif, TX1TX2T, of mucin-2 glycoprotein was identified by means of a mucin-2-specific monoclonal antibody, mAb 994, raised against a synthetic mucin-derived 15-mer peptide conjugate. For determination of the epitope sequence recognised with highest affinity by mAb 994, a combinatorial approach was applied using the portioning-mixing technique excluding Cys. Antibody binding of libraries was most profound when Gln was at the X1 position. Analytical characterisation of the TQTX2T library was conducted by amino acid analysis and matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) and electrospray ionisation Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometric methods. Control libraries were prepared by mixing 19 individual peptides corresponding to the TQTX2T sequence. Thus, mixtures of 6, 10 and 19 pentapeptides were analysed and compared with the combinatorial mixture. MALDI-TOFMS was able to detect only partially the components in the 6- and 10-member mixtures, but failed to characterise a more complex 19-member mixture. In contrast, ESI-FTICRMS resolved all mixtures of higher complexity and provided direct identification at monoisotopic resolution, such as for a peptide library containing ,isobaric' lysine and glutamine (,m,=,0.0364,Da). The results of this study suggest that ESI-FTICRMS is a powerful tool for characterisation of combinatorial peptide libraries of higher complexity. Copyright © 2002 John Wiley & Sons, Ltd. [source] Characterization of a [(O3/2SiMe)x(OSi(OH)Me)y(OSiMe2)z] silsesquioxane copolymer resin by mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2001Ron E. Tecklenburg Electrospray ionization Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry were applied to a complex silsesquioxane-siloxane copolymer resin. The wide-polydispersity starting material was fractionated into 21 separate fractions in order to facilitate the analysis by mass spectrometry. ESI-FTICR exact mass measurements were able to identify the specific oligomers present in the lowest mass fractions and showed that very few unreacted silanol groups remained, that is, topologically closed structures predominated. MALDI-TOFMS was able to show that gel-permeation chromatography substantially underestimated the molecular masses of the higher mass fractions. Mass autocorrelation was able to show that the silsesquioxane monomer appeared only in even numbers in any given oligomer. This is a natural consequence of the highly condensed nature of the resin. Copyright © 2001 John Wiley & Sons, Ltd. [source] Flexible open-cell design for internal-source matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2001Vladimir Frankevich A new Fourier transform ion cyclotron resonance (FTICR) cell design is described that improves the performance of internal-source matrix-assisted laser desorption/ionization (MALDI) applications. The design employs a capacitively coupled open FTICR cell and a ring electrode placed between the ion source and the ICR cell. The flexibility of our open-cell design allows the use of several different trapping schemes for ion detection. Elimination of the drift time dependence in a MALDI experiment, ion accumulation, RF ion selection, and improved trapping of MALDI ions desorbed at an angle to the surface normal are some of the advantages of this design. Copyright © 2001 John Wiley & Sons, Ltd. [source] Dynamics of the ion cyclotron resonance effect on amino acids adsorbed at the interfacesBIOELECTROMAGNETICS, Issue 1 2006N. Comisso Abstract In this study we show a reproduction of the Zhadin experiment, which consists of the transient increase of the electrolytic current flow across an aqueous solution of L -arginine and L -glutamic acid induced by a proper low frequency alternating magnetic field superimposed to a static magnetic field of higher strength. We have identified the mechanisms that were at the origin of the so-far poor reproducibility of the above effect: the state of polarization of the electrode turned out to be a key parameter. The electrochemical investigation of the system shows that the observed phenomenon involves the transitory activation of the anode due to ion cyclotron frequency effect, followed again by anode passivation due to the adsorption of amino acid and its oxidation products. The likely occurrence of similar ion cyclotron resonance (ICR) phenomena at biological membranes, the implications on ion circulation in living matter, and the consequent biological impact of environmental magnetic fields are eventually discussed. Bioelectromagnetics 27:16,25, 2006. © 2005 Wiley-Liss, Inc. [source] Complexes between Lithium Cation and Diphenylalkanes in the Gas Phase: The Pincer EffectCHEMISTRY - A EUROPEAN JOURNAL, Issue 29 2006Jean-François Gal Prof. Abstract The gas-phase lithium cation basicities (LCB values, Gibbs free energies of binding) of ,,,-diphenylalkanes Ph-(CH2)n -Ph (n=2, 3, or 7) and 1,1-diphenylethane Ph-CH(Me)-Ph were investigated by means of Fourier-transform ion cyclotron resonance (FTICR) mass spectrometry. Their structures, and those of the corresponding Li+ complexes were optimized at the B3LYP/6-31G(d) level and their relative stabilities calculated at the B3LYP/6-311+G(3df,2p)//B3LYP/6-31G(d) level. Whereas the most stable conformers of the free diphenylalkanes were found to adopt a completely stretched aliphatic chain connecting the two benzene rings, the most stable Li+ complexes correspond to conformers in which the alkali metal cation interacts simultaneously with both benzene rings through the folding of the aliphatic chain ("pincer effect"). This chelation brings about a significant enhancement of the Li+ binding enthalpies (LBE values), which were calculated to be approximately 75 kJ,mol,1 higher than those evaluated for conventional (singly coordinated) , complexes in which the metal cation interacts with only one of the benzene rings. The increase of the corresponding lithium cation basicities, however, (Gibbs free energies of Li+ binding, LCB values) was calculated to be smaller by approximately 15 kJ,mol,1 as the pincer effect is entropically disfavored. The good agreement between the calculated LCB values, assuming a statistical distribution of the different conformers present in the gas phase, and the experimental LCB values measured by means of FTICR mass spectrometry are considered indirect evidence of the existence of the pincer effect. [source] Alkali Metal Complexes of the Dipeptides PheAla and AlaPhe: IRMPD Spectroscopy,CHEMPHYSCHEM, Issue 4 2008Nick C. Polfer, Prof. Abstract Complexes of PheAla and AlaPhe with alkali metal ions Na+ and K+ are generated by electrospray ionization, isolated in the Fourier-transform ion cyclotron resonance (FT,ICR) ion trapping mass spectrometer, and investigated by infrared multiple-photon dissociation (IRMPD) using light from the FELIX free electron laser over the mid-infrared range from 500 to 1900 cm,1. Insight into structural features of the complexes is gained by comparing the obtained spectra with predicted spectra and relative free energies obtained from DFT calculations for candidate conformers. Combining spectroscopic and energetic results establishes that the metal ion is always chelated by the amide carbonyl oxygen, whilst the C-terminal hydroxyl does not complex the metal ion and is in the endo conformation. It is also likely that the aromatic ring of Phe always chelates the metal ion in a cation-, binding configuration. Along with the amide CO and ring chelation sites, a third Lewis-basic group almost certainly chelates the metal ion, giving a threefold chelation geometry. This third site may be either the C-terminal carbonyl oxygen, or the N-terminal amino nitrogen. From the spectroscopic and computational evidence, a slight preference is given to the carbonyl group, in an ROaOt chelation pattern, but coordination by the amino group is almost equally likely (particularly for K+PheAla) in an ROaNt chelation pattern, and either of these conformations, or a mixture of them, would be consistent with the present evidence. (R represents the , ring site, Oa the amide oxygen, Ot the terminal carbonyl oxygen, and Nt the terminal nitrogen.) The spectroscopic findings are in better agreement with the MPW1PW91 DFT functional calculations of the thermochemistry compared with the B3LYP functional, which seems to underestimate the importance of the cation,, interaction. [source] | ||||||||||