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Cyclotron Resonance Mass Spectrometry (cyclotron + resonance_mass_spectrometry)
Kinds of Cyclotron Resonance Mass Spectrometry Selected AbstractsGas-phase radical,radical recombination reactions of nitroxides with substituted phenyl radicalsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 4 2004J. L. Heidbrink Fourier-transform ion cyclotron resonance mass spectrometry has been used to examine gas-phase reactions of four different nitroxide free radicals with eight positively charged pyridyl and phenyl radicals (some containing a Cl, F, or CF3 substituent). All the radicals reacted rapidly (near collision rate) with nitroxides by radical,radical recombination. However, some of the radicals were also able to abstract a hydrogen atom from the nitroxide. The results establish that the efficiency (kreaction/kcollision) of hydrogen atom abstraction varies with the electrophilicity of the radical, and hence is attributable to polar effects (a lowering of the transition-state energy by an increase in its polar character). The efficiency of the recombination reaction is not sensitive to substituents, presumably due to a very low reaction barrier. Even so, after radical,radical recombination has occurred, the nitroxide adduct was found to fragment in different ways depending on the structure of the radical. For example, a cationic fragment was eliminated from the adducts of the more electrophilic radicals via oxygen anion abstraction by the radical (i.e., the nitroxide adduct cleaves heterolytically), whereas adducts of the less electrophilic radicals predominantly fragmented via homolytic cleavage (oxygen atom abstraction). Therefore, differences in the product branching ratios were found to be attributable to polar factors. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 216,229 2004 [source] Gas phase isomeric differentiation of oleanolic and ursolic acids associated with heptakis-(2,6-di- O -methyl)-,-cyclodextrin by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2010Zhan Yu Abstract Oleanolic acid (OA) and ursolic acid (UA) are isomeric triterpenoid compounds with similar pharmaceutical properties. Usually, modern chromatographic and electrophoretic methods are widely utilized to differentiate these two compounds. Compared with mass spectrometric (MS) methods, these modern separation methods are both time- and sample-consuming. Herein, we present a new method for structural differentiation of OA and UA by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with the association of heptakis-(2,6-di- O -methyl)-,-cyclodextrin (DM-,-CD). Exact MS and tandem MS (MS/MS) data showed that there is no perceptible difference between OA and UA, as well as their ,-cyclodextrin and ,-cyclodextrin complexes. However, there is a remarkable difference in MS/MS spectra of DM-,-CD complexes of OA and UA. The peak corresponding to the neutral loss of a formic acid and a water molecule could only be observed in the MS/MS spectrum of the complex of DM-,-CD : OA. Molecular modeling calculations were also employed to further investigate the structural differences of DM-,-CD : OA and DM-,-CD : UA complexes. Therefore, by employing DM-,-CD as a reference reagent, OA and UA could be differentiated with purely MS method. Copyright © 2010 John Wiley & Sons, Ltd. [source] Studies of the intermolecular DNA triplexes of C+·GC and T·AT triplets by electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2008Cuihong Wan Abstract Formation and stabilities of four 14-mer intermolecular DNA triplexes, consisting of third strands with repeating sequence CTCT, CCTT, CTT, or TTT, were studied by electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) in the gas phase. The gas-phase stabilities of the triplexes were compared with their CD spectra and melting behaviors in solution, and parallel correlation between two phases were obtained. In the presence of 20 mM NH4+ (pH 5.5), the formation of the TTT triplex was not detected in both solution and the gas phase. Other triplexes showed the same order, CTCT > CCTT > CTT, of ion abundances in mass spectra and Tm values in solution. The more stable triplexes are those that contained higher percentage of C+·GC triplets and an alternating CT sequence. However, the CCTT with the same C+·GC triplets as the CTCT showed a higher stability than the latter during the gas-phase dissociation. Furthermore, a biphasic triplex-to-duplex-to-single transition was detected in the gas phase, while a monophasic triplex-to-single dissociation was observed in solution. The present results reveal that hydrogen bonds and electrostatic interactions dominate in the gas phase, while base stacking and hydrophobic interactions dominate in solution to stabilize the triplexes. Moreover, weak acidic conditions (pH 5,6) promote the formation of the parallel triplexes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Peptide and protein characterization by high-rate electron capture dissociation Fourier transform ion cyclotron resonance mass spectrometry.JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2004The original article to which this Erratum refers was published in Journal of Mass Spectrometry 39 (7) 2004; 719,729. Copyright © 2004 John Wiley & Sons, Ltd. [source] Sheathless electrospray ionization directly from a capillary monolith for fast liquid chromatography coupled to Fourier transform ion cyclotron resonance mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2004Felix C. Leinweber [source] Protein identification by peptide mass fingerprinting and peptide sequence tagging with alternating scans of nano-liquid chromatography/infrared multiphoton dissociation Fourier transform ion cyclotron resonance mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2003Toshiyuki Kosaka Abstract We have developed a method for protein identification with peptide mass fingerprinting and sequence tagging using nano liquid chromatography (LC)/Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). To achieve greater sensitivity, a nanoelectrospray (nano-ES) needle packed with reversed-phase medium was used and connected to the nano-ES ion source of the FTICR mass spectrometer. To obtain peptide sequence tag information, infrared multiphoton dissociation (IRMPD) was carried out in nano-LC/FTICR-MS analysis. The analysis involves alternating nano-ES/FTICR-MS and nano-ES/IRMPD-FTICR-MS scans during a single LC run, which provides sets of parent and fragment ion masses of the proteolytic digest. The utility of this alternating-scan nano-LC/IRMPD-FTICR-MS approach was evaluated by using bovine serum albumin as a standard protein. We applied this approach to the protein identification of rat liver diacetyl-reducing enzyme. It was demonstrated that this enzyme was correctly identified as 3-,-hydroxysteroid dehydrogenase by the alternating-scan nano-LC/IRMPD-FTICR-MS approach with accurate peptide mass fingerprinting and peptide sequence tagging. Copyright © 2003 John Wiley & Sons, Ltd. [source] Evaluation of the metal binding properties of a histidine-rich fusogenic peptide by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2003Andrea Sinz Abstract Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) was used to investigate metal ion interactions of the 18 amino acid peptide fragment B18 (LGLLLRHLRHHSNLLANI), derived from the membrane-associated protein bindin. The peptide sequence B18 represents the minimal membrane-binding motif of bindin and resembles a putative fusion peptide. The histidine-rich peptide has been shown to self-associate into distinct supramolecular structures, depending on the presence of Zn2+ and Cu2+. We examined the binding of B18 to the metal ions Cu2+, Zn2+, Mg2+, Ca2+, Mn2+ and La3+. For Cu2+, we compared the metal binding affinities of the wild-type B18 peptide with those of its mutants in which one, two or three histidine residues have been replaced by serines. Upon titration of B18 with Cu2+ ions, we found sequential binding of two Cu2+ ions with dissociation constants of ,34 and ,725 µM. Mutants of B18, in which one histidine residue is replaced by serine, still exhibit sequential binding of two copper ions with affinities for the first Cu2+ ion comparable to that of wild-type B18 peptide, but with a greatly reduced affinity for the second Cu2+ ion in mutants H112S and H113S. For mutants in which two histidines are replaced by serines, the affinity for the first Cu2+ ion is reduced ,3,10 times in comparison with B18. The mutant in which all three histidine residues are replaced by serines exhibits an ,14-fold lower binding for the first Cu2+ ion compared with B18. For the other metal ions under investigation (Zn2+, Mg2+, Ca2+, Mn2+ and La3+), a modest affinity to B18 was detected binding to the peptide in a 1 : 1 stoichiometry. Our results show a high affinity of the wild-type fusogenic peptide B18 for Cu2+ ions whereas the Zn2+ affinity was found to be comparable to that of other di- and trivalent metal ions. Copyright © 2003 John Wiley & Sons, Ltd. [source] Characterization by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry of the major photoproducts of temoporfin (m -THPC) and bacteriochlorin (m -THPBC)JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2001Marc Angotti Abstract The photobleaching of 5,10,15,20-tetrakis(m -hydroxyphenyl)chlorin (temoporfin, m -THPC) and 5,10,15,20-tetrakis(m -hydroxyphenyl)bacteriochlorin (bacteriochlorin, m -THPBC) was studied in ethanol,water (1 : 99, v/v) and in physiological medium (phosphate-buffered saline, PBS) with or without fetal calf serum (FCS). m -THPC solution was irradiated with the laser radiation of 650 nm, whereas m -THPBC solution underwent two consecutive irradiations at 532 and 650 nm. The photoproducts were characterized by UV,visible absorption spectrophotometry and by matrix-assisted laser desorption/ionization (MALDI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). Independent of the solvent used, the phototransformation of either photosensitizer yielded the formation of 5,10,15,20-tetrakis (m -hydroxyphenyl)porphyrin (m -THPP) through a major dehydrogenation process. Copyright © 2001 John Wiley & Sons, Ltd. [source] Solvation of acylium fragment ions in electrospray ionization quadrupole ion trap and Fourier transform ion cyclotron resonance mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2001Ziqiang Guan Abstract In electrospray ionization (ESI) quadrupole ion trap and Fourier transform ion cyclotron resonance mass spectrometry, certain fragment ions (e.g. acylium ions) generated either during the ion transportation process (in the source interface region) or in the ion trap are found to undergo ion,molecule reactions with ESI solvent molecules (water, acetonitrile and aliphatic alcohols) to form adduct species. These unexpected solvated fragment ions severely complicate the interpretation of mass spectrometic data. High-resolution accurate mass measurements are important in establishing the elemental compositions of these adduct species and preventing erroneous data interpretation. Copyright © 2001 John Wiley & Sons, Ltd. [source] Activation of large lons in FT-ICR mass spectrometryMASS SPECTROMETRY REVIEWS, Issue 2 2005Julia Laskin Abstract The advent of soft ionization techniques, notably electrospray and laser desorption ionization methods, has enabled the extension of mass spectrometric methods to large molecules and molecular complexes. This both greatly extends the applications of mass spectrometry and makes the activation and dissociation of complex ions an integral part of these applications. This review emphasizes the most promising methods for activation and dissociation of complex ions and presents this discussion in the context of general knowledge of reaction kinetics and dynamics largely established for small ions. We then introduce the characteristic differences associated with the higher number of internal degrees of freedom and high density of states associated with molecular complexity. This is reflected primarily in the kinetics of unimolecular dissociation of complex ions, particularly their slow decay and the higher energy content required to induce decomposition,the kinetic shift (KS). The longer trapping time of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) significantly reduces the KS, which presents several advantages over other methods for the investigation of dissociation of complex molecules. After discussing general principles of reaction dynamics related to collisional activation of ions, we describe conventional ways to achieve single- and multiple-collision activation in FT-ICR MS. Sustained off-resonance irradiation (SORI),the simplest and most robust means of introducing the multiple collision activation process,is discussed in greatest detail. Details of implementation of this technique, required control of experimental parameters, limitations, and examples of very successful application of SORI-CID are described. The advantages of high mass resolving power and the ability to carry out several stages of mass selection and activation intrinsic to FT-ICR MS are demonstrated in several examples. Photodissociation of ions from small molecules can be effected using IR or UV/vis lasers and generally requires tuning lasers to specific wavelengths and/or utilizing high flux, multiphoton excitation to match energy levels in the ion. Photodissociation of complex ions is much easier to accomplish from the basic physics perspective. The quasi-continuum of vibrational states at room temperature makes it very easy to pump relatively large amounts of energy into complex ions and infrared multiphoton dissociation (IRMPD) is a powerful technique for characterizing large ions, particularly biologically relevant molecules. Since both SORI-CID and IRMPD are slow activation methods they have many common characteristics. They are also distinctly different because SORI-CID is intrinsically selective (only ions that have a cyclotron frequency close to the frequency of the excitation field are excited), whereas IRMPD is not (all ions that reside on the optical path of the laser are excited). There are advantages and disadvantages to each technique and in many applications they complement each other. In contrast with these slow activation methods, the less widely appreciated activation method of surface induced dissociation (SID) appears to offer unique advantages because excitation in SID occurs on a sub-picosecond time scale, instantaneously relative to the observation time of any mass spectrometer. Internal energy deposition is quite efficient and readily adjusted by altering the kinetic energy of the impacting ion. The shattering transition,instantaneous decomposition of the ion on the surface,observed at high collision energies enables access to dissociation channels that are not accessible using SORI-CID or IRMPD. Finally, we discuss some approaches for tailoring the surface to achieve particular aims in SID. © 2004 Wiley Periodicals, Inc., Mass Spec Rev 24:135,167, 2005 [source] The role of electron capture dissociation in biomolecular analysisMASS SPECTROMETRY REVIEWS, Issue 2 2005Helen J. Cooper Abstract The introduction of electron capture dissociation (ECD) to electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) constitutes a significant advance in the structural analysis of biomolecules. The fundamental features and benefits of ECD are discussed in this review. ECD is currently unique to FT-ICR MS and the fundamentals of that technique are outlined. The advantages and complementarity of ECD in relation to other tandem mass spectrometry (MS/MS) techniques, such as infrared multiphoton dissociation (IRMPD) and sustained off-resonance collision-induced dissociation (SORI-CID), are discussed. The instrumental considerations associated with implementation of ECD, including activated ion techniques and coupling to on-line separation techniques, are covered, as are the allied processes electronic excitation dissociation (EED), electron detachment dissociation (EDD), and hot electron capture (HECD). A major theme of this review is the role of ECD in proteomics, particularly for characterization of post-translational modifications (phosphorylation, glycosylation, carboxyglutamic acid, sulfation, acylation, and methionine oxidation) and the top-down approach to protein identification. The application of ECD to the analysis of polymers, peptide nucleic acids, and oligonucleotides is also discussed. © 2004 Wiley Periodicals, Inc., Mass Spec Rev 24:201,222, 2005 [source] Protein identification in cerebrospinal fluid using packed capillary liquid chromatography Fourier transform ion cyclotron resonance mass spectrometryPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 2 2003Margareta Ramström Abstract The identification and characterization of proteins in complex biological samples such as body fluids, require powerful and reliable tools. Mass spectrometry is today one of the most important methods in such research. This paper reports on the results from the first experiment where a tryptic digest of cerebrospinal fluid was analyzed applying reversed phase liquid chromatography coupled on-line to a 9.4 T Fourier transform ion cyclotron resonance mass spectrometer. In total, 70,204 peaks were detected, which originated from 16,296 isotopic clusters corresponding to 6551 unique peptide masses. From these masses, 39 proteins were identified in the sample. The amount of sample required for one experiment corresponds to 32 ,L of cerebrospinal fluid. [source] Characterization of oil sands naphthenic acids treated with ultraviolet and microwave radiation by negative ion electrospray Fourier transform ion cyclotron resonance mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 21 2010John V. Headley Naphthenic acids (NAs) are concentrated in oil sand process water (OSPW) as a result of caustic oil sands extraction processes. There is considerable interest in methods for treatment of NAs in OSPW. Earlier work has shown that the combination of ultraviolet (UV) and microwave treatments in the laboratory was effective in reducing the concentration of classical NAs. Here we apply Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to further characterize NAs treated with (a) UV (254,nm) in the presence of TiO2 catalyst; and/or (b) microwave irradiation (2.45,GHz). FT-ICR MS was used to characterize the NA fraction before and after treatment. Acidic oxygen-containing classes were most abundant in all samples whereas other heteroatomic classes were least abundant or not present in some samples. For example, the SO2 -containing species were absent in UV- or combined UV- and microwave-treated samples. The O2 class was dominant in all samples, indicative of NAs. However, samples treated with UV and microwave radiation have a lower relative abundance of other heteroatomic classes. We observed O2, S1O2, O3, S1O3, O4, O5, and O6 classes, whereas the species with relatively high On content, namely, the O3, O5, and O6 classes, were present only in UV- and microwave-treated samples. The relatively high On content is consistent with oxidation of the parent acids in treated samples. There may thus be potential implications for environmental forensics. For example, the monitoring of the ratio of SO2:O2 or tracking the relative abundances of O2, O3, O4, O5, and O6 classes may provide insights for distinguishing naturally derived oil sands components from those that are process-related in aquatic environments. Copyright © 2010 John Wiley & Sons, Ltd. [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] 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] Analysis of S -adenosylmethionine and related sulfur metabolites in bacterial isolates of Pseudomonas aeruginosa (BAA-47) by liquid chromatography/electrospray ionization coupled to a hybrid linear quadrupole ion trap and Fourier transform ion cyclotron resonance mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 21 2009Tommaso R. I. Cataldi A comprehensive and highly selective method for detecting in bacterial supernatants a modified sulfur nucleoside, S -adenosyl-L-methionine (SAM), and its metabolites, i.e., S -adenosylhomocysteine (SAH), adenosine (Ado), 5,-deoxy-5,-methylthioadenosine (MTA), adenine (Ade), S -adenosyl-methioninamine (dcSAM), homocysteine (Hcy) and methionine (Met), was developed. The method is based on reversed-phase liquid chromatography with positive electrospray ionization (ESI+) coupled to a hybrid linear quadrupole ion trap (LTQ) and 7-T Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). A gradient elution was employed with a binary solvent of 0.05,M ammonium formate at pH 4 and acetonitrile. The assay involves a simultaneous cleanup of cell-free bacterial broths by solid-phase extraction and trace enrichment of metabolites with a 50-fold concentration factor by using immobilized phenylboronic and anion-exchange cartridges. While the quantitative determination of SAM was performed using stable-isotope-labeled SAM-d3 as an internal standard, in the case of Met and Ade, Met- 13C and Ade- 15N2 were employed as isotope-labeled internal standards, respectively. This method enabled the identification of SAM and its metabolites in cell-free culture of Pseudomonasaeruginosa grown in Davis minimal broth (formulation without sulphur organic compounds), with routine sub-ppm mass accuracies (,0.27,±,0.68,ppm). The resulting contents of SCSS -SAM, SS -dcSAM, MTA, Ado and Met in the free-cell supernatant of P. aeruginosa was 56.4,±,2.1,nM, 32.2,±,2.2,nM, 0.91,±,0.10,nM, 19.6,±,1.2,nM and 1.93,±,0.02,µM (mean,±,SD, n,=,4 extractions), respectively. We report also the baseline separation (Rs ,1.5) of both diastereoisomeric forms of SAM (SCSS and SCRS) and dcSAM (SS and RS), which can be very useful to establish the relationship between the biologically active versus the inactive species, SCSS/SCRS and SS/RS of SAM and dcSAM, respectively. An additional confirmation of SAM-related metabolites was accomplished by a systematic study of their MS/MS spectra. Copyright © 2009 John Wiley & Sons, Ltd. [source] Molecular mass ranges of coal tar pitch fractions by mass spectrometry and size-exclusion chromatographyRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2009F. Karaca A coal tar pitch was fractionated by solvent solubility into heptane-solubles, heptane-insoluble/toluene-solubles (asphaltenes), and toluene-insolubles (preasphaltenes). The aim of the work was to compare the mass ranges of the different fractions by several different techniques. Thermogravimetric analysis, size-exclusion chromatography (SEC) and UV-fluorescence spectroscopy showed distinct differences between the three fractions in terms of volatility, molecular size ranges and the aromatic chromophore sizes present. The mass spectrometric methods used were gas chromatography/mass spectrometry (GC/MS), pyrolysis/GC/MS, electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) and laser desorption time-of-flight mass spectrometry (LD-TOFMS). The first three techniques gave good mass spectra only for the heptane-soluble fraction. Only LDMS gave signals from the toluene-insolubles, indicating that the molecules were too involatile for GC and too complex to pyrolyze into small molecules during pyrolysis/GC/MS. ESI-FTICRMS gave no signal for toluene-insolubles probably because the fraction was insoluble in the methanol or acetonitrile, water and formic acid mixture used as solvent to the ESI source. LDMS was able to generate ions from each of the fractions. Fractionation of complex samples is necessary to separate smaller molecules to allow the use of higher laser fluences for the larger molecules and suppress the formation of ionized molecular clusters. The upper mass limit of the pitch was determined as between 5000 and 10,000,u. The pitch asphaltenes showed a peak of maximum intensity in the LDMS spectra at around m/z 400, in broad agreement with the estimate from SEC. The mass ranges of the toluene-insoluble fraction found by LDMS and SEC (400,10,000,u with maximum intensity around 2000,u by LDMS and 100,9320,u with maximum intensity around 740,u by SEC) are higher than those for the asphaltene fraction (200,4000,u with maximum intensity around 400,u by LDMS and 100,2680,u with maximum intensity around 286,u by SEC) and greater than values considered appropriate for petroleum asphaltenes (300,1200,u with maximum intensity near 700,u). Copyright © 2009 John Wiley & Sons, Ltd. [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] Sulfonamide bond cleavage in benzenesulfonamides and rearrangement of the resulting p -aminophenylsulfonyl cations: application to a 2-pyrimidinyloxybenzylaminobenzenesulfonamide herbicideRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2005Hao-Yang Wang The gas-phase fragmentation/rearrangement reactions of compound 1, [2-(4,6-dimethoxypyrimidin-2-yloxy)-benzyl]-[4-(piperidine-1-sulfonyl)phenyl]amine, have been examined by Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The analyses reveal that under sustained off-resonance irradiation collision-induced dissociation (SORI-CID) conditions in the FTICR cell, protonated 1 undergoes two competitive pathways initiated by different protonation positions. The first pathway is initiated by protonation on the amino group and yields only one fragment ion due to loss of the entire benzenesulfonamide moiety. In the second pathway, protonation of the sulfonamide group leads to cleavage of a sulfonamide bond with loss of the neutral piperidine, followed by loss of SO via a sulfonyl cation rearrangement. An intramolecular SNAr mechanism is proposed to rationalize the rearrangement of the p -aminophenylsulfonyl cation and the resulting SO loss. To test the generality of this process, SORI-CID spectra of protonated sulfamethoxazole and of the p -aminophenylsulfonyl cation (SBN) were obtained. For the SBN ion, SORI-CID experiments as well as density functional theory (B3LYP) calculations show that rearrangement, assigned as a SNAr reaction of the sulfonyl cation group, can account for the observed SO loss process. Candidate transition state structures were optimized at the B3LYP/6-31+G (d, p) level of theory using the Gaussian98 molecular modeling package. The computational results show that the barrier for SO loss from SBN is much lower than that for SO2 loss, which satisfactorily rationalizes the SORI-CID experimental results for SBN. Moreover, it is proposed that a fragment ion at m/z 196 in the MS/MS spectrum of protonated 1 is formed via the ion resulting from SO loss via a second intramolecular SNAr mechanism. Copyright © 2005 John Wiley & Sons, Ltd. [source] Tool command language automation of the modular ion cyclotron data acquisition system (MIDAS) for data-dependent tandem Fourier transform ion cyclotron resonance mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2003Michael A. Freitas This manuscript describes the addition of data-dependent automation to the modular ion cyclotron resonance data acquisition system (MIDAS). The automation is made possible by developments and incorporation of a tool command language (Tcl) interpreter for automated acquisition. To accomplish the automation, real-time generation of excitation waveforms and scriptable data post-processing has been implemented into the MIDAS source code. In addition a new excitation event has also been added to allow for run-time generation of a single notch stored waveform inverse Fourier transform (SWIFT) excitation event. Examples of these new features and discussion of their enhancement to the existing data station are presented. Copyright © 2003 John Wiley & Sons, Ltd. [source] A combined ion source for fast switching between electrospray and matrix-assisted laser desorption/ionization in Fourier transform ion cyclotron resonance mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2002Gökhan Baykut A new ion source has been developed for Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) that enables quick changes between matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) modes. When operating as an ESI source, the sample solution is sprayed through an angled nebulizer. The generated ions pass through a glass capillary followed by a skimmer and three sequential hexapole ion guides. Ions can be accumulated in the third hexapole (storage hexapole) before they are injected into the ICR trap. The second hexapole is mounted on a movable platform which also carries the MALDI sample plate. During the switch from ESI to MALDI, this platform moves the second hexapole out of the hexapole series and locates a MALDI sample plate with 384 sample positions into the area directly in front of the storage hexapole. The storage hexapole is in a medium pressure chamber (MPC) which has windows both for the incoming laser beam and for the observation optics, as well as a gas tube for pulsing collision gas into the chamber. During the MALDI operation the focused laser beam enters the MPC, passes between the hexapole rods and irradiates a MALDI sample on the target plate. The sample molecules are desorbed/ionized into the storage hexapole and simultaneously cooled by collisions with the pulsed gas. Ions desorbed from multiple laser shots can be accumulated in this hexapole before they are transferred to the ICR trap. With the combined ion source a computer-controlled switch between MALDI and ESI modes is possible in less than a minute, depending on the position of the MALDI target on the 384-spot plate. Immediate acquisition of mass spectra is possible after mode switching without the need for tuning or re-calibration. Copyright © 2002 John Wiley & Sons, Ltd. [source] Liquid chromatography and electron-capture dissociation in Fourier transform ion cyclotron resonance mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 10 2002Magnus Palmblad Liquid separation methods in combination with electrospray mass spectrometry as well as the recently introduced fragmentation method electron capture dissociation (ECD) have become powerful tools in proteomics research. This paper presents the results of the first successful attempts to combine liquid chromatography (LC) and Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) with ECD in the analysis of a mixture of standard peptides and of a bovine serum albumin tryptic digest. A novel electron injection system provided conditions for ECD sufficient to yield extensive sequence information for the most abundant peptides in the mixtures on the time-scale of the chromatographic separation. The results suggest that LC/ECD-FTICRMS can be employed in the characterization of peptides in enzymatic digests of proteins or protein mixtures and identify and localize posttranslational modifications. Copyright © 2002 John Wiley & Sons, Ltd. [source] Optimal pressure conditions for unbiased external ion accumulation in a two-dimensional radio-frequency quadrupole for Fourier transform ion cyclotron resonance mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 21 2001Mikhail E. Belov When combined with on-line separations (e.g., capillary liquid chromatography (LC)), Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) provides a powerful tool for biological applications, and particularly proteomic studies. The sensitivity, dynamic range, and duty cycle provided by FTICR-MS have been shown to be increased by ion trapping and accumulation in a two-dimensional (2D) radio-frequency (rf)-only multipole positioned externally to an FTICR cell. However, it is important that ions be detected across the desired m/z range without a significant bias. In this work we found that pressure inside the accumulation rf-quadrupole plays an important role in obtaining ,unbiased' ion accumulation. Pressure optimization was performed in both pulsed and continuous modes. It was found that unbiased accumulation in a 2D rf-only quadrupole could be achieved in the pressure range of 5,×,10,4 to 5,×,10,3 Torr. External ion accumulation performed at the optimal pressure resulted in an increase in both the spectrum acquisition rates and dynamic range. 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] Crystallization of a pentapeptide-repeat protein by reductive cyclic pentylation of free amines with glutaraldehydeACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2009Matthew W. Vetting The pentapeptide-repeat protein EfsQnr from Enterococcus faecalis protects DNA gyrase from inhibition by fluoroquinolones. EfsQnr was cloned and purified to homogeneity, but failed to produce diffraction-quality crystals in initial crystallization screens. Treatment of EfsQnr with glutaraldehyde and the strong reducing agent borane,dimethylamine resulted in a derivatized protein which produced crystals that diffracted to 1.6,Å resolution; their structure was subsequently determined by single-wavelength anomalous dispersion. Analysis of the derivatized protein using Fourier transform ion cyclotron resonance mass spectrometry indicated a mass increase of 68,Da per free amino group. Electron-density maps about a limited number of structurally ordered lysines indicated that the modification was a cyclic pentylation of free amines, producing piperidine groups. [source] Disaccharide Mimetics of the Aminoglycoside Antibiotic NeamineCHEMBIOCHEM, Issue 9 2004Andre Venot Dr. Abstract A highly convergent approach has been employed for the facile synthesis of a library of 24 disaccharides that are ,(1,3), ,(1,3), ,(1,4), or ,(1,4) linked and contain 2,4 amino groups. Fourier-transformation ion cyclotron resonance mass spectrometry (FT-ICR MS) has been used to determine dissociation constant (Kd) values for the binding of the disaccharides to a prototypical fragment of 16S ribosomal RNA. Several derivatives bound with affinities similar to that of neamine. Structure,activity relationships have revealed the substitution pattern that is important for high-affinity binding. The compounds described here are unique lead compounds for the design of novel aminoglycoside antibiotics. [source] The Structure of a Novel Neutral Lipid,A from the Lipopolysaccharide of Bradyrhizobium elkanii Containing Three Mannose Units in the BackboneCHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2010Iwona Komaniecka Dr. Abstract The chemical structure of the lipid,A of the lipopolysaccharide (LPS) from Bradyrhizobium elkanii USDA 76 (a member of the group of slow-growing rhizobia) has been established. It differed considerably from lipids,A of other Gram-negative bacteria, in that it completely lacks negatively charged groups (phosphate or uronic acid residues); the glucosamine (GlcpN) disaccharide backbone is replaced by one consisting of 2,3-dideoxy-2,3-diamino- D -glucopyranose (GlcpN3N) and it contains two long-chain fatty acids, which is unusual among rhizobia. The GlcpN3N disaccharide was further substituted by three D -mannopyranose (D -Manp) residues, together forming a pentasaccharide. To establish the structural details of this molecule, 1D and 2D,NMR spectroscopy, chemical composition analyses and high-resolution mass spectrometry methods (electrospray ionisation Fourier-transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and tandem mass spectrometry (MS/MS)) were applied. By using 1D and 2D,NMR spectroscopy experiments, it was confirmed that one D -Manp was linked to C-1 of the reducing GlcpN3N and an ,-(1,6)-linked D -Manp disaccharide was located at C-4, of the non-reducing GlcpN3N (,-linkage). Fatty acid analysis identified 12:0(3-OH) and 14:0(3-OH), which were amide-linked to GlcpN3N. Other lipid,A constituents were long (,-1)-hydroxylated fatty acids with 26,33 carbon atoms, as well as their oxo forms (28:0(27-oxo) and 30:0(29-oxo)). The 28:0(27-OH) was the most abundant acyl residue. As confirmed by high-resolution mass spectrometry techniques, these long-chain fatty acids created two acyloxyacyl residues with the 3-hydroxy fatty acids. Thus, lipid,A from B. elkanii comprised six acyl residues. It was also shown that one of the acyloxyacyl residues could be further acylated by 3-hydroxybutyric acid (linked to the (,-1)-hydroxy group). [source] Investigation of Protein,Ligand Interactions by Mass SpectrometryCHEMMEDCHEM, Issue 4 2007Andrea Sinz Prof. Abstract The rate of drug discovery is greatly dependent on the development and improvement of rapid and reliable analytical methods that allow screening for protein,ligand interactions. The solution-based methods for investigating protein,ligand interactions by mass spectrometry (MS), which are discussed in this paper, are hydrogen/deuterium exchange of protein backbone amide hydrogens, and photoaffinity labeling. Moreover, MS analysis of intact noncovalent protein,ligand complexes is described. Fourier transform ion cyclotron resonance mass spectrometry (FTICR,MS) with its ultra-high resolution and excellent mass accuracy is also considered herein as it is gaining increasing popularity for a mass spectrometric investigation of protein,ligand interactions. [source] | ||||||||||