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Collision-induced Dissociation (collision-induced + dissociation)
Selected AbstractsThe First Sandwich Complex with an Octa(thioether) Coordination Sphere: Bis(maleonitrile-tetrathia-12-crown-4)silver(I),EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2006Hans-Jürgen Holdt Abstract The new tetrathiacrown ethers maleonitrile-tetrathia-12-crown-4 (mn12S4) and maleonitrile-tetrathia-13-crown-4 (mn13S4) have been prepared and characterised by X-ray crystallographic analysis. These crown ethers form 2:1, 3:2 and 1:1 complexes with AgY (Y = BF4, PF6). The crystal structures of [Ag(mn12S4)2]BF4 (3a), [Ag(mn13S4)2]BF4 (4a) and [Ag2(mn13S4)3](PF6)2 (6b) have been determined. Compound 3a contains the centrosymmetric sandwich complex cation [Ag(mn12S4)2]+ where each mn12S4 ligand is coordinated to the Ag centre in an endo manner through all four S atoms. The 2:1 complex [Ag(mn12S4)2]+ is the first sandwich complex with a tetrathiacrown ether and the first complex with an octa(thioether) coordination sphere. The crystal structure of compound 4a also reveals a 2:1 complex. This complex, [Ag(mn13S4)2]+, exhibits a half-sandwich structure. One mn13S4 ligand coordinates to Ag+ by all four S donor atoms and the other 13S4 crown by only one S atom. Compound 6b contains a dinuclear Ag complex. The Ag complexes 3a,b,8a,b were also studied by electrospray ionisation mass spectrometry. Collision-induced dissociation (CID) was used to compare the relative stability of 2:1 complexes [AgL2]+ and 1:1 complexes [AgL]+ (L = mn12S4, mn13S4). The 13C NMR chemical shifts of 2:1 and 1:1 Ag complexes and their corresponding free ligands were also estimated and compared. The free energy of the barrier of ring inversion (,G,) for [Ag(mn12S4)2]+ was determined to be 64 kJ,mol,1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Collision-induced dissociation of sulfur-containing imidazolium ionic liquidsJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2008Alain Lesimple Abstract A number of 1,2-dimethylimidazole ionic liquids substituted on NII with alkyl chains of varying lengths terminated with sulfur-containing groups were investigated by electrospray high-resolution tandem Fourier-transform mass spectrometry. Fragmentation pathways are strongly dependent on the oxidation state of the sulfur and the alkyl chain length. The dissociations detected are rationalized by deuterium labeling, comparisons between homologous compounds and accurate mass data. Several homolytic processes are reported, leading to distonic ions and loss of hydrogen, methyl and other free radicals. Copyright © 2007 John Wiley & Sons, Ltd. [source] Collision-induced dissociation studies of protonated ether,(H2O)n (n = 1,3) clustersJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2006Daniel J. Goebbert Abstract We have studied the protonated ether,(H2O)n (n = 1,3) complexes containing tetrahydrofuran, dimethyl, diethyl, dibutyl, and butylmethyl ethers using a flowing afterglow triple-quadrupole mass spectrometer. Collision-induced dissociation, CID, of all clusters with n = 1, 2 shows sequential water loss. The n = 3 cluster of dimethyl ether shows sequential water loss, while all other ether clusters display selective product formation. The CID spectra are interpreted based on known energetics, and theoretical studies of the dimethyl and diethyl ether systems. Copyright © 2006 John Wiley & Sons, Ltd. [source] To b or not to b: The ongoing saga of peptide b ionsMASS SPECTROMETRY REVIEWS, Issue 4 2009Alex G. Harrison Abstract Modern soft ionization techniques readily produce protonated or multiply protonated peptides. Collision-induced dissociation (CID) of these protonated species is often used as a method to obtain sequence information. In many cases fragmentation occurs at amide bonds. When the charge resides on the C-terminal fragment so-called y ions are produced which are known to be protonated amino acids or truncated peptides. When the charge resides on the N-terminal fragment so-called b ions are produced. Often the sequence of y and b ions are essential for peptide sequencing. The b ions have many possible structures, a knowledge of which is useful in this sequencing. The structures of b ions are reviewed in the following with particular emphasis on the variation of structure with the number of amino acid residues in the b ion and the effect of peptide side chain on b ion structure. The recent discovery of full cyclization of larger b ions results in challenges in peptide sequencing. This aspect is discussed in detail. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 28:640,654, 2009 [source] Role of 2-oxo and 2-thioxo modifications on the proton affinity of histidine and fragmentation reactions of protonated histidine,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2010Adrian K. Y. Lam A combination of electrospray ionisation (ESI), multistage and high-resolution mass spectrometry experiments was used to compare the gas-phase chemistry of the amino acids histidine (1), 2-oxo-histidine (2), and 2-thioxo-histidine (3). Collision-induced dissociation (CID) of all three different proton-bound heterodimers of these amino acids led to the relative gas-phase proton affinity order of: histidine >2-thioxo-histidine >2-oxo-histidine. Density functional theory (DFT) calculations confirm this order, with the lower proton affinities of the oxidised histidine derivatives arising from their ability to adopt the more stable keto/thioketo tautomeric forms. All protonated amino acids predominately fragment via the combined loss of H2O and CO to yield a1 ions. Protonated 2 and 3 also undergo other small molecule losses including NH3 and the imine HN=CHCO2H. The observed differences in the fragmentation pathways are rationalised through DFT calculations, which reveal that while modification of histidine via the introduction of the oxygen atom in 2 or the sulfur atom in 3 does not affect the barriers against the loss of H2O+CO, barriers against the losses of NH3 and HN=CHCO2H are lowered relative to protonated histidine. Copyright © 2010 John Wiley & Sons, Ltd. [source] Collision-induced dissociation of protonated tetrapeptides containing , -alanine, , -aminobutyric acid, , -aminocaproic acid or 4-aminomethylbenzoic acid residues,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2006Erach R. Talaty The influence of the presence and position of a single , -alanine, , -aminobutyric acid, , -aminocaproic acid or 4-aminomethylbenzoic acid residue on the tendency to form b - and y -type product ions was determined using a group of protonated tetrapeptides with general sequence XAAG, AXAG and AAXG (where X refers to the position of amino acid substitution). The hypothesis tested was that the ,alternative' amino acids would influence product ion signal intensities by inhibiting or suppressing either the nucleophilic attack or key proton transfer steps by forcing the adoption of large cyclic intermediates or blocking cyclization altogether. We found that specific b ions are diminished or eliminated completely when ,A, ,Abu, Cap or 4AMBz residues are positioned such that they should interfere with the intramolecular nucleophilic attack step. In addition, differences in the relative proton affinities of the alternative amino acids influence the competition between complementary bn and yn ions. For both the AXAG and the XAAG series of peptides, collision-induced dissociation (CID) generated prominent b ions despite potential inhibition or suppression of intramolecular proton migration by the ,A, ,Abu, Cap or 4AMBz residues. The prominent appearance of b ions from the AXAG and XAAG peptide is noteworthy, and suggests either that proton migration occurs through larger, ,whole' peptide cyclic intermediates or that fragmentation proceeds through a population of [M+H]+ isomers that are initially protonated at amide O atoms. Copyright © 2006 John Wiley & Sons, Ltd. [source] Cluster ions of diquat and paraquat in electrospray ionization mass spectra and their collision-induced dissociation spectraRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2003Boris L. Milman Cluster ions such as [Cat+X+nM]+ (n,=,0,4); [Cat-H+nM]+ (n,=,1,3); and [2(Cat-H)+X+nM]+ (n,=,0,2), where Cat, X, and M are the dication, anion, and neutral salt (CatX2), respectively, are observed in electrospray ionization (ESI) mass spectrometry of relatively concentrated solutions of diquat and paraquat. Collision-induced dissociation (CID) reactions of the clusters were observed by tandem mass spectrometry (MS/MS), including deprotonation to form [Cat-H]+, one-electron reduction of the dication to form Cat+., demethylation of the paraquat cation to form [Cat-CH3]+, and loss of neutral salt to produce smaller clusters. The difference in acidity and reduction power between diquat and paraquat, evaluated by thermodynamical estimates, can rationalize the different fractional yields of even-electron ([Cat-H]+ and its clusters) and odd-electron (mostly Cat+.) ions in ESI mass spectra of these pesticides. The [Cat+n,·,Solv]2+ doubly charged cluster ions, where n,,,2 and Solv is the solvent molecule (methanol and/or water), are only observed as very weak peaks in precursor ion CID spectra of the Cat2+ salt cation at low collision energy. The presence of an anion and a solvent molecule in a cluster is assumed to be related to existence of tight and loose ion pairs, respectively, in multiply charged droplets/ions formed by ESI. The results emphasize again the role of solution chemistry concepts such as acidity/basicity, redox power, and ion-pair formation, for ESI. Copyright © 2003 John Wiley & Sons, Ltd. [source] Collision-induced dissociation of glycero phospholipids using electrospray ion-trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2001Åsmund Larsen Characterisation of phospholipids was achieved using collision-induced dissociation (CID) with an ion-trap mass spectrometer. The product ions were compared with those obtained with a triple quadrupole mass spectrometer. In the negative ion mode the product ions were mainly sn -1 and sn -2 lyso-phospholipids with neutral loss of ketene in combination with neutral loss of the polar head group. Less abundant product ions were sn -1 and sn -2 carboxylate anions. CID using a triple quadrupole mass spectrometer, however, gave primarily the sn -1 and sn -2 carboxylate anions together with lyso-phosphatidic acid with neutral loss of water. For the ion trap a charge-remote-type mechanism is proposed for formation of the lyso-phospholipid product ions by loss of ,-hydrogen on the fatty acid moiety, electron rearrangement and neutral loss of ketene. A second mechanism involves nucleophilic attack of the phosphate oxygen on the sn -1 and sn -2 glycerol backbone to form carboxylate anions with neutral loss of cyclo lyso-phospholipids. CID (MS3 and MS4) of the lyso-phospholipids using the ion-trap gave the same carboxylate anions as those obtained with a triple quadrupole instrument where multiple collisions in the collision cell are expected to occur. The data demonstrate that phospholipid species determination can be performed by using LC/MSn with an ion-trap mass spectrometer with detection of the lyso-phospholipid anions. The ion-trap showed no loss in sensitivity in full scan MSn compared to multiple reaction monitoring data acquisition. In combination with on-line liquid chromatography this feature makes the ion-trap useful in the scanning modes for rapid screening of low concentrations of phospholipid species in biological samples as recently described (Uran S, Larsen,Å, Jacobsen PB, Skotland T. J. Chromatogr. B 2001; 758: 265). Copyright © 2001 John Wiley & Sons, Ltd. [source] Fragmentation of Alkoxo(catecholato)vanadium(V) Complexes[(C6H4O2)V(OR1)(OR2)]+ in the Gas PhaseEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2005Malgorzata Kaczorowska Abstract Electrospray ionization (ESI) mass spectrometry is used to investigate the gas-phase dissociation behavior of vanadium(V) complexes [(C6H4O2)V(OR1)(OR2)]+ containing two identical or different alkoxy groups (R1, R2 = CH3, C2H5, n -C3H7, i -C3H7 and t -C4H9) and a catecholato ligand (C6H4O2). The fragmentation reactions of the complexes are studied by collision-induced dissociation (CID) and labeling experiments. For [(C6H4O2)V(OR1)(OR2)]+ cations with alkoxo groups larger than methyl, a trend for preferential evaporation of hydrocarbon fragments is observed, followed by expulsion of neutral alcohols. Further, the CID spectra of all complexes show a signal which can be assigned to the complex [(C6H4O2)VO]+. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Use of LC,MS,MS for the rapid, specific and sensitive quality control measurement of carrier in a PET radioligand: [18F]FECNTJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 13 2005H. Umesha Shetty Abstract In the production of radioligands for imaging low concentrations of target proteins (e.g. receptors or transporters) in human subjects with positron emission tomography, control of specific radioactivity is necessary for efficacy and safety. Such quality control requires a fast method to be available for measuring carrier (non-radioactive ligand) in each batch of radioligand, preceding its release for administration. Measurement is usually achieved with HPLC equipped with an ultraviolet (UV) absorbance detector. However, this method is not easily applicable to radioligands that have low UV extinction coefficients and are produced at high specific radioactivity, such as [18F] (2,-carbomethoxy-3,-(4-chlorophenyl)-8-(2-fluoroethyl)nortropane; [18F]FECNT). Here we describe a fast, specific and sensitive LC,MS,MS method for measuring carrier in [18F]FECNT preparations. Small samples of formulated [18F]FECNT plus an added internal standard (2,-carbomethoxy-3,-(4-chlorophenyl)-8-(n -propyl)nortropane; INTSTD) are rapidly eluted from a short reverse phase HPLC column into an MS probe. Following electrospray ionization, the molecular ions ([MH]+) of FECNT (m/z=326) and INTSTD (m/z=322) are isolated and energized for collision-induced dissociation. The product ions from FECNT (m/z=294) and INTSTD (m/z=290) are monitored selectively. The calibration curve for MS response is linear for FECNT concentrations in the range 2,20 pg/µl and suitable for reproducibly (RSD 5%) and rapidly (<3 min) measuring low concentrations of carrier in [18F]FECNT preparations. Copyright © 2005 John Wiley & Sons, Ltd. [source] Simultaneous HPLC-DAD-MS (ESI+) determination of structural and geometrical isomers of carotenoids in mature grapes,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2010Pasquale Crupi Abstract Carotenoids are uniquely functional polyene pigments ubiquitous in nature; aside from being responsible for the color of a wide variety of vegetables, interest is being focused on food carotenoids due to their likely health benefits. From analytical point of view, it is important to unequivocally identify individual carotenoid compounds in many food stuffs. Therefore, isolation of standards from natural sources must be encouraged for accurate identifications. Like many fruits, mature grape berries contain numerous carotenoid compounds, mostly found in the skin at levels two to three times higher than in the pulp. Carotenoid compounds in a typical wine grape variety (Negroamaro) grown in Apulian region were investigated by reversed-phase C30 (RP-30) HPLC-DAD-MS (ESI+) analysis. As a consequence of an unusual ionization process of carotenoids, their mass spectra registered in the positive ion mode comprised both protonated molecules and molecular ion radicals with little fragmentation. Additionally, selective collision-induced dissociation (CID) experiments, together with fine structures of the UV,vis spectra, were used to differentiate structural and geometrical isomers. This technique allowed the simultaneous determination of regio- and cis -isomers of lutein (zeaxanthin, 9Z and 9,Z -lutein) and a cis -isomer of ,-carotene (9Z - ,-carotene), 5,6-epoxy xanthophylls (violaxanthin, (9,Z)-neoxanthin, lutein-5,6-epoxide) and 5,8-epoxy xanthophylls diasteroisomers (neochrome, auroxanthin, luteoxanthin, flavoxanthin, chrysanthemaxanthin). Copyright © 2010 John Wiley & Sons, Ltd. [source] Peak width-mass correlation in CID MS/MS of isomeric oligosaccharides using traveling-wave ion mobility mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2009Tohru Yamagaki Abstract Isomeric oligosaccharides ,-cyclodextrin (,-CD), glucosyl-,CD (Glc1 -,CD) and maltosyl-,CD (Glc2 -,CD) were analyzed by traveling-wave ion mobility (twIM) mass spectrometry (MS). Their formation of multicharged multimers differed from each other. The ion mobility-mass spectrometry was useful in the self-assembling and complex formation analyses of CD isomers. The drift times of the isomers and their product ions with the same mass were almost the same in collision-induced dissociation (CID) MS/MS. In contrast, the ion mobility peak widths were sensitive to structural differences of the isomeric product ions. The twIM peak width (ms - µs) of the product ions [M , Glcn + H]+ (n = 0 , 6) of ,-CD correlated linearly with their masses (Da); the large and/or long chain product ions had wider peak widths, which were much wider than those from the general diffusion effect. This was a novel and useful ,trend line' to discriminate between the three isomers. Plots of [M , Glc2 , 6 + H]+ of Glc1 -,CD and [M , Glc3 , 6 + H]+ of Glc2 -,CD product ions' plots were on the same trend line as ,-CD. The plots of [M , Glc1 + H]+ of Glc1 -,CD and [M , Glc1, 2 + H]+ of Glc2 -,CD strayed from the ,-CD line; their peak widths were narrower than those of ,-CD. These results indicated that product ions from the chemical species of Glc1 -, CD and Glc2 -,CD retained their CD structure. Analyses of the IM peak widths enable us to elucidate the structures of the product ions. Copyright © 2009 John Wiley & Sons, Ltd. [source] Phosphopeptide fragmentation and analysis by mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2009Paul J. Boersema Abstract Reversible phosphorylation is a key event in many biological processes and is therefore a much studied phenomenon. The mass spectrometric (MS) analysis of phosphorylation is challenged by the substoichiometric levels of phosphorylation and the lability of the phosphate group in collision-induced dissociation (CID). Here, we review the fragmentation behaviour of phosphorylated peptides in MS and discuss several MS approaches that have been developed to improve and facilitate the analysis of phosphorylated peptides. CID of phosphopeptides typically results in spectra dominated by a neutral loss of the phosphate group. Several proposed mechanisms for this neutral loss and several factors affecting the extent at which this occurs are discussed. Approaches are described to interpret such neutral loss-dominated spectra to identify the phosphopeptide and localize the phosphorylation site. Methods using additional activation, such as MS3 and multistage activation (MSA), have been designed to generate more sequence-informative fragments from the ion produced by the neutral loss. The characteristics and benefits of these methods are reviewed together with approaches using phosphopeptide derivatization or specific MS scan modes. Additionally, electron-driven dissociation methods by electron capture dissociation (ECD) or electron transfer dissociation (ETD) and their application in phosphopeptide analysis are evaluated. Finally, these techniques are put into perspective for their use in large-scale phosphoproteomics studies. Copyright © 2009 John Wiley & Sons, Ltd. [source] An investigation of the homolytic saccharide cleavage of deprotonated flavonol 3- O -glycosides in a quadrupole ion trap mass spectrometerJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2008Barry D. Davis Abstract The trend in the extent of homolytic saccharide cleavage is reported for a series of deprotonated flavonol 3- O -glycosides upon collision-induced dissociation (CID) in a quadrupole ion trap mass spectrometer. The second-generation product ions from the primary [Y0], and [Y0, H],, product ions were also identified. It was determined that the structure of both the aglycon and the saccharide portions of the flavonoid glycoside are pivotal in inducing radical cleavage. In contrast to earlier work on this subject reported for a smaller group of flavonols, the correlation between the degree of B-ring hydroxylation and the extent of radical saccharide cleavage showed several notable exceptions in the present work. Homolytic cleavage was also investigated in the context of using tandem mass spectrometry to identify the aglycon portions of flavonoid glycosides. Copyright © 2008 John Wiley & Sons, Ltd. [source] Evaluation of glycosylation and malonylation patterns in flavonoid glycosides during LC/MS/MS metabolite profilingJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2008P. Kachlicki Abstract Flavonoid conjugates constitute several classes of plant phenolic secondary metabolites including many isomeric compounds differing in the hydroxylation pattern and substitution of their rings with different groups such as alkyls, acyls or sugars. These compounds occur in plant tissues mainly as glycosides and in many cases it is necessary to have reliable and detailed information concerning the structure of these natural products. Our results were obtained using leaf extracts of Arabidopsis thaliana and Lupinus angustifolius in which different glycosides of flavones, flavonols and isoflavones are present. Analysis of collision-induced dissociation (CID)/MS/MS spectra of protonated [M + H]+, sodiated [M + Na]+ or deprotonated [M , H], molecules recorded during HPLC runs may bring needed information in this respect. However, registration of mass spectra of [M + Na]+ ions with a good efficiency is possible only after post-column addition of a sodium acetate solution to the LC column eluate. The retention of sodium cation on the saccharidic parts of the molecule is observed after the CID fragmentation. In many cases, the location of this cation on the glycan attached to C-3 hydroxyl group of flavonol led to assignment of its structure. Additionally, the determination of the structure of the aglycone and of the sequence of the glycan part was made possible through the CID data obtained from the [M + H]+ and [M , H], ions. CID spectra show a different order of sugar elimination from hydroxyl groups at C-3 and C-7 in flavonol glycosides isolated from A. thaliana leaves and give sufficient information to discriminate flavonoid O-diglycosides from flavonoid di-O-glycosides. Copyright © 2007 John Wiley & Sons, Ltd. [source] Structure elucidation of aplidine metabolites formed in vitro by human liver microsomes using triple quadrupole mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2005Esther F. A. Brandon Abstract The cyclic depsipeptide aplidine is a new anti-cancer drug of marine origin. Four metabolites of this compound were found after incubation with pooled human microsomes using gradient high-performance liquid chromatography with ultraviolet detection. After chromatographic isolation, the metabolites have been identified using nano-electrospray triple quadrupole mass spectrometry. A highly specific sodium-ion interaction with the cyclic structure opens the depsipeptide ring, and cleavage of the amino acid residues gives sequence information when activated by collision-induced dissociation in the second quadrupole. The aplidine molecule could undergo the following metabolic reactions: hydroxylation at the isopropyl group (metabolites apli-h 1 and apli-h 2); C-dealkylation at the N(Me)-leucine group (metabolite apli-da); hydroxylation at the isopropyl group and C-dealkylation at the N(Me)-leucine group (metabolite apli-da/h), and C-demethylation at the threonine group (metabolite apli-dm). The identification of these metabolites formed in vitro may greatly aid the elucidation of the metabolic pathways of aplidine in humans. Copyright © 2005 John Wiley & Sons, Ltd. [source] High-resolution H/D exchange studies on the HET-s218,295 prion proteinJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2005Alexis Nazabal Abstract In a search for improved resolution of hydrogen/deuterium (H/D) exchange experiments analyzed by mass spectrometry (HXMS), we evaluated two methodologies for a detailed structural study of solvent accessibility in the case of the HET-s218,295 prion protein. For the first approach, after incubation in the deuterated solvent, aggregated HET-s218,295 was digested with pepsin and the generated peptides were analyzed by nanospray mass spectrometry in an ion trap, with and without collision-induced dissociation (CID). We compared deuterium incorporation in peptides as determined on peptide pseudomolecular ions and on b and y fragments produced by longer peptides under CID conditions. For both b and y fragment ions, an extensive H/D scrambling phenomenon was observed, in contrast with previous studies comparing CID-MS experiments and 1H NMR data. Thus, the spatial resolution of HXMS experiments could not be improved by means of MS/MS data generated by an ion trap mass spectrometer. In a second approach, the incorporation of deuterium was analyzed by MS for 76 peptides of the HET-s218,289 peptide mass fingerprint, and the use of shared boundaries among peptic peptides allowed us to determine deuteration levels of small regions ranging from one to four amino acids. This methodology led to evidence of highly protected regions along the HET-s218,295 sequence. Copyright © 2005 John Wiley & Sons, Ltd. [source] Quantitative peptidomics of mouse pituitary: comparison of different stable isotopic tagsJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2005Fa-Yun Che Abstract Determining the relative levels of neuropeptides in two samples is important for many biological studies. An efficient, sensitive and accurate technique for relative quantitative analysis involves tagging the peptides in the two samples with isotopically distinct labels, pooling the samples and analyzing them using liquid chromatography/mass spectrometry (LC/MS). In this study, we compared two different sets of isotopic tags for analysis of endogenous mouse pituitary peptides: succinic anhydride with either four hydrogens or deuteriums and [3-(2,5-dioxopyrrolidin-1-yloxycarbonyl)propyl]trimethylammonium chloride with either nine hydrogens or deuteriums. These two labels react with amines and impart either a negative charge (succinyl) or a positive charge (4-trimethylammoniumbutyryl (TMAB)). Every endogenous mouse pituitary peptide labeled with the light TMAB reagent eluted from the C18 reversed-phase column at essentially the same time as the corresponding peptide labeled with the heavy reagent. Most of the peptides labeled with succinyl groups also showed co-elution of the heavy- and light-labeled forms on LC/MS. The mass difference between the heavy and light TMAB reagents (9 Da per label) was larger than that of the heavy and light succinyl labels (4 Da per label), and for some peptides the larger mass difference provided more accurate determination of the relative abundance of each form. Altogether, using both labels, 82 peptides were detected in Cpefat/fat mouse pituitary extracts. Of these, only 16 were detected with both labels, 41 were detected only with the TMAB label and 25 were detected only with the succinyl label. A number of these peptides were de novo sequenced using low-energy collisional tandem mass spectrometry. Whereas the succinyl group was stable to the collision-induced dissociation of the peptide, the TMAB-labeled peptides lost 59 Da per H9 TMAB group. Several peptides identified in this analysis represent previously undescribed post-translational processing products of known pituitary prohormones. In conclusion, both succinyl and TMAB isotopic labels are useful for quantitative peptidomics, and together these two labels provide more complete coverage of the endogenous peptides. Copyright © 2005 John Wiley & Sons, Ltd. [source] Using collision-induced dissociation with corrections for the ion number of degrees of freedom for quick comparisons of relative bonding strengthJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2004Natalia Vinokur Abstract The number of degrees of freedom-dependent stability of ions and ion,neutral non-covalent complexes under collision-induced dissociation (CID) conditions was studied in a quadrupole ion trap mass spectrometer. It was found that the stability of ions as probed by energy-variable CID has a linear dependence on the total number of degrees of freedom for the ions (or ion,neutral complexes) with the same (or nearly the same) bonding energy. The slope of such a stability vs number of degrees of freedom dependence correlates with the binding energy. Proton-bound amine dimers display the lowest slope as they have weak bonds. Breaking covalent bonds will result in much greater slopes. In addition to the binding energy, the vibrational frequencies of the ion also affect the stability vs number of degrees of freedom behavior. Studying such a dependence of the CID stability in a system paves the way for direct relative binding energy comparisons. The application of this approach is demonstrated by testing the relative heme affinities of anti-malaria drugs and related compounds. Copyright © 2004 John Wiley & Sons, Ltd. [source] Rearrangement process occurring in the fragmentation of adefovir derivativesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2004Xiaoyan Chen Abstract The fragmentation of the antiviral drug adefovir dipivoxil and its two active metabolites, adefovir and monopivoxil adefovir, was investigated using both ion trap and triple-quadrupole mass spectrometers. Fragment ions due to loss of 30 Da were observed and attributed to an unanticipated rearrangement process by loss of formaldehyde. The proposed mechanism is supported with the aid of three newly synthesized adefovir derivatives and with accurate mass measurement. Other fragmentations by loss of a pivaloyl group, loss of water, C,P bond cleavage and C,O bond cleavage were also observed for adefovir derivatives. It was concluded that the compounds containing a >POO,CHR,OCO, group generally displayed a rearrangement reaction by loss of RCHO in collision-induced dissociation, and the process generally required an activation energy lower than for a direct bond cleavage. Copyright © 2004 John Wiley & Sons, Ltd. [source] Neutral loss of amino acid residues from protonated peptides in collision-induced dissociation generates N- or C-terminal sequence ladders,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2003Mogjiborahman Salek Abstract The widespread occurrence of the neutral loss of one to six amino acid residues as neutral fragments from doubly protonated tryptic peptides is documented for 23 peptides with individual sequences. Neutral loss of amino acids from the N-terminus of doubly charged tryptic peptides results in doubly charged y-ions, forming a ladder-like series with the ions [M + 2H]2+ = ymax2+, ymax , 12+, ymax , 22+, etc. An internal residue such as histidine, proline, lysine or arginine appears to favor this type of fragmentation, although it was sometimes also observed for peptides without this structure. For doubly protonated non-tryptic peptides with one of these residues at or near the N-terminus, we observed neutral loss from the C-terminus, resulting in a doubly charged b-type ion ladder. The analyses were performed by Q-TOF tandem mass spectrometry, facilitating the recognition of neutral loss ladders by their 2+ charge state and the conversion of the observed mass differences into reliable sequence information. It is shown that the neutral loss of amino acid residues requires low collision offset values, a simple mechanistic explanation based on established fragmentation rules is proposed and the utility of this neutral loss fragmentation pathway as an additional source for dependable peptide sequence information is documented. Copyright © 2003 John Wiley & Sons, Ltd. [source] A novel tandem quadrupole mass spectrometer allowing gaseous collisional activation and surface induced dissociationJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2001Shabaz Mohammed Abstract A novel tandem quadrupole mass spectrometer is described that enables gaseous collision-induced dissociation (CID) and surface-induced dissociation (SID) experiments. The instrument consists of a commercially available triple quadrupole mass spectrometer connected to an SID region and an additional, orthogonal quadrupole mass analyser. The performance of the instrument was evaluated using leucine-enkephalin, allowing a comparison between CID and SID, and with previous reports of other SID instruments. The reproducibility of SID data was assessed by replicate determinations of the collision energy required for 50% dissociation of leucine-enkephalin; excellent precision was observed (standard deviation of 0.6 eV) though, unexpectedly, the reproducibility of the equivalent figure for CID was superior. Several peptides were analysed using SID in conjunction with liquid secondary-ion mass spectrometry or electrospray; a comparison of the fragmentation of singly protonated peptide ions and the further dissociation of y-type fragments was consistent with the equivalence of the latter fragments to protonated peptides. Few product ions attributable to high-energy cleavages of amino acid side-chains were observed. The SID properties were investigated of a series of peptides differing only in the derivatization of a cysteine residue; similar decomposition efficiencies were observed for all except the cysteic acid analogue, which demonstrated significantly more facile fragmentation. Copyright © 2001 John Wiley & Sons, Ltd. [source] Determination of the electron affinities of ,- and ,-naphthyl radicals using the kinetic method with full entropy analysis.JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2001H bond dissociation energies of naphthalene, The C Abstract The C , H bond dissociation energies for naphthalene were determined using a negative ion thermochemical cycle involving the gas-phase acidity (,Hacid) and electron affinity (EA) for both the ,- and ,-positions. The gas-phase acidity of the naphthalene ,- and ,-positions and the EAs of the ,- and ,-naphthyl radicals were measured in the gas phase in a flowing afterglow,triple quadrupole apparatus. A variation of the Cooks kinetic method was used to measure the EAs of the naphthyl radicals by collision-induced dissociation of the corresponding ,- and ,-naphthylsulfinate adducts formed by reactions in the flow tube portion of the instrument. Calibration references included both , and , radicals, and full entropy analysis was performed over a series of calibration curves measured at collision energies ranging from 3.5 to 8 eV (center-of-mass). The measured EAs are 33.0 ± 1.4 and 31.4 ± 1.0 kcal mol,1 (1 kcal = 4.184 kJ) for the ,- and ,-naphthyl radicals, respectively. The gas-phase acidities for naphthalene were measured by the DePuy silane cleavage method, which utilizes the relative abundances of aryldimethylsiloxides and trimethylsiloxide that result from competitive cleavages from a proposed pentacoordinate hydroxysiliconate intermediate. The measured acidities are 394.0 ± 5.0 and 397.6 ± 4.8 kcal mol,1 for the ,- and ,- positions, respectively. The C , H bond dissociation energies calculated from the thermochemical cycle are 113.4 ± 5.2 and 115.4 ± 4.9 kcal mol,1 for the ,- and ,-positions, respectively. These energies are, to within experimental error, indistinguishable and are approximately the same as the first bond dissociation energy for benzene. Copyright © 2001 John Wiley & Sons, Ltd. [source] Isolation of inulin-type oligosaccharides from Chinese traditional medicine: Morinda officinalis How and their characterization using ESI-MS/MSJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1 2010Zhenmin Yang Abstract Inulin-type oligosaccharides with different DP were prepared by size-exclusion chromatography and purity of each oligosaccharide was determined by HPLC equipped with cyclodextrin-bond column. The purities of obtained inulin-type oligosaccharides with different DP were more than 98% by one-step process. The DP and molecular weight were obtained through ESI-MS in negative mode. The characterization of the inulin-type oligosaccharides with different DP was studied by MS/MS spectra obtained by collision-induced dissociation of molecular ions ([M,H],). When the DP was lower, the fragment ions were formed through cross-ring cleavages of two bonds within the sugar ring and glycosidic cleavages. However, with the increase of DP, the ions resulting from glycosidic cleavages between two sugar residues were predominant. [source] Balancing robust quantification and identification for iTRAQ: Application of UHR-ToF MSPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 11 2010Saw Yen Ow Abstract iTRAQ reagents allow the simultaneous multiplex identification and quantification of a large number of proteins. Success depends on effective peptide fragmentation in order to generate both peptide sequence ions (higher mass region, 150,2200,m/z) and reporter ions (low mass region, 113,121,m/z) for protein identification and relative quantification, respectively. After collision-induced dissociation, the key requirements to achieve a good balance between the high and low m/z ions are effective ion transmission and detection across the MS/MS mass range, since the ion transmission of the higher m/z range competes with that of the low m/z range. This study describes an analytical strategy for the implementation of iTRAQ on maXis UHR-Qq-ToF instruments, and discusses the impact of adjusting the MS/MS ion transmission parameters on the quality of the overall data sets. A technical discussion highlights a number of maXis-specific parameters, their impact of quantification and identification, and their cross-interactions. [source] O -Glycosylated 24,kDa human growth hormone has a mucin-like biantennary disialylated tetrasaccharide attached at Thr-60PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 13 2009Juan J. Bustamante Abstract MS was used to characterize the 24,kDa human growth hormone (hGH) glycoprotein isoform and determine the locus of O -linked oligosaccharide attachment, the oligosaccharide branching topology, and the monosaccharide sequence. MALDI-TOF/MS and ESI-MS/MS analyses of glycosylated 24,kDa hGH tryptic peptides showed that this hGH isoform is a product of the hGH normal gene. Analysis of the glycoprotein hydrolysate by high-performance anion-exchange chromatography with pulsed amperometric detection and HPLC with fluorescent detection for N -acetyl neuraminic acid (NeuAc) yielded the oligosaccharide composition (NeuAc2, N -acetyl galactosamine1, Gal1). After ,-elimination to release the oligosaccharide from glycosylated 24,kDa hGH, collision-induced dissociation of tryptic glycopeptide T6 indicated that there had been an O -linked oligosaccharide attached to Thr-60. The sequence and branching structure of the oligosaccharide were determined by ESI-MS/MS analysis of tryptic glycopeptide T6. The mucin-like O -oligosaccharide sequence linked to Thr-60 begins with N -acetyl galactosamine and branches in a bifurcated topology with one appendage consisting of galactose followed by NeuAc and the other consisting of a single NeuAc. The oligosaccharide moiety lies in the high-affinity binding site 1 structural epitope of hGH that interfaces with both the growth hormone and the prolactin receptors and is predicted to sterically affect receptor interactions and alter the biological actions of hGH. [source] Characterization of a peptide family from the skin secretion of the Middle East Tree Frog Hyla savignyi by composition-based de novo sequencingRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2010Markus Langsdorf A new tryptophyllin-like peptide family was found in the skin secretion of the tree frog Hyla savignyi. Peptides were characterized by database-independent sequencing strategies and specific ion fragmentation features were investigated. Skin secretions from specimens of Hyla savignyi were collected by mild electrical stimulation. Peptides were separated by reversed-phase nano-high-performance liquid chromatography (nanoHPLC) and mass spectra were acquired online by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Peptides were characterized by manual de novo sequencing and by composition-based sequencing (CBS), appearing mostly as C-terminal free acids and as their acid amide analogs. Amide peptides yielded lower intensities of y-type ions after collision-induced dissociation (CID) than their acid analogs. A mechanism of internal b-ion formation (positive ion mode) and of CO2 elimination (negative ion mode) is proposed. We also exemplified phenomena such as the proline effect and formation of non-direct sequence ions after sequence rearrangements. The occurrence of rearrangement products, of internal ions and of the proline effect made the CID spectra highly complex. CBS analysis nevertheless resulted in successful and highly reliable sequence analysis. Copyright © 2010 John Wiley & Sons, Ltd. [source] On the structural diversity of Shiga toxin glycosphingolipid receptors in lymphoid and myeloid cells determined by nanoelectrospray ionization tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2010Petra Hoffmann Shiga toxin (Stx, synonymous to verotoxin, VT) binds with high and low affinity to the globo-series neutral glycosphingolipids (GSLs), globotriaosylceramide (Gb3Cer or Gal,4Gal,4Glc,1Cer, also known as CD77) and globotetraosylceramide (Gb4Cer or GalNAc,3Gal,4Gal,4Glc,1Cer), respectively, which represent the targets of Stxs on many different cell types. B-cell-derived Raji cells and THP-1 cells of monocytic origin are widely used for the investigation of Stx-mediated cellular response, because Stx is known to cause cell death in both cell lines. Despite their functional importance, the Stx receptors of Raji and THP-1 cells have so far not been investigated. This prompted us to explore the structures of their GSL receptors in detail by means of nanoelectrospray ionization quadrupole time-of-flight mass spectrometry (nanoESI-QTOF-MS) with collision-induced dissociation (CID) in conjunction with Stx1 as well as anti-Gb3Cer and anti-Gb4Cer antibodies. Using the combination of a thin-layer chromatography (TLC) overlay assay and MS1 and MS2 analysis we identified Gb3Cer (d18:1, C24:1/C24:0) as the prevalent Stx1-receptor accompanied by less abundant Gb3Cer (d18:1, C16:0) in the neutral GSL fraction of Raji cells. The same Gb3Cer species but with almost equal proportions of the C24:1/C24:0 and C16:0 variants were found in THP-1 cells. In addition, unusual hydroxylated Gb3Cer (d18:1, C24:1/C24:0) and Gb3Cer (d18:1, C26:1) could be identified in trace quantities in both cell lines. As the most obvious difference between Raji and THP-1 cells we observed the expression of Gb4Cer in THP-1 cells, whereas Raji cells failed to express this elongation product of Gb3Cer. Both short- and long-chain fatty acid carrying Gb4Cer (d18:1, C16:0) and Gb4Cer (d18:1, C24:1/C24:0), respectively, were the prevalent Gb4Cer variants. This first report on the differential expression of Gb3Cer and Gb4Cer and their structural diversity in lymphoid and myeloid cell lines supports the hypothesis that such heterogeneities might play a functional role in the molecular assembly of GSLs in membrane organization and cellular signaling of Stx-susceptible cells. Copyright © 2010 John Wiley & Sons, Ltd. [source] Methylation of acidic moieties in poly(methyl methacrylate-co-methacrylic acid) copolymers for end-group characterization by tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2010Rémi Giordanengo The complete structural characterization of a copolymer composed of methacrylic acid (MAA) and methyl methacrylate (MMA) units was achieved using tandem mass spectrometry. In a first step, collision-induced dissociation (CID) of sodiated MAA-MMA co-oligomers allowed us to determine the co-monomeric composition, the random nature of the copolymer and the sum of the end-group masses. However, dissociation reactions of MAA-based molecules mainly involve the acidic pendant groups, precluding individual characterization of the end groups. Therefore, methylation of all the acrylic acid moieties was performed to transform the MAA-MMA copolymer into a PMMA homopolymer, for which CID mainly proceeds via backbone cleavages. Using trimethylsilyldiazomethane as a derivatization agent, this methylation reaction was shown to be complete without affecting the end groups. Using fragmentation rules established for PMMA polymers together with accurate mass measurements of the product ions and knowledge of reagents used for the studied copolymer synthesis, a structure could be proposed for both end groups and it was found to be consistent with signals obtained in nuclear magnetic resonance spectra. Copyright © 2010 John Wiley & Sons, Ltd. [source] Gas-phase formation of protonated benzene during collision-induced dissociation of certain protonated mono-substituted aromatic molecules produced in electrospray ionizationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2010Min Li Protonated benzene, C6H, has been studied extensively to understand the structure and energy of a protonated organic molecule in the gas phase. The formation of C6H is either through direct protonation of benzene, i.e., chemical ionization, or through fragmentation of certain radical cations produced from electron ionization or photon ionization. We report a novel observation of C6H as a product ion formed in the collision-induced dissociation (CID) of protonated benzamide and related molecules produced via electrospray ionization (ESI). The formation of C6H from these even-electron precursor ions during the CID process, which has not been previously reported, is proposed to occur from the protonated molecules via a proton migration in a five-membered ring intermediate followed by the cleavage of the mono-substituent CC bond and concurrent formation of an ion-molecule complex. This unique mechanism has been scrutinized by examining some deuterated molecules and a series of structurally related model compounds. This finding provides a convenient mean to generate C6H, a reactive intermediate of considerable interest, for further physical or chemical investigation. Further studies indicate that the occurrence of C6H in liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) appears to be a rather common phenomenon for many compounds that contain ,benzoyl-type' moieties. Hence, the observation of the C6H ion in LC/ESI-MS/MS can be used as an informative fragmentation pathway which should facilitate the identification of a great number of compounds containing the ,benzoyl-type' and similar structural features. These compounds are frequently present in food and pharmaceutical products as leachable impurities that require strict control and rapid elucidation of their identities. Copyright © 2010 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||