bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of pyridinoline and its derivatives by scanning‐array four‐sector tandem mass spectrometry
Authors: Self Ron , Stead David A. , Robins Simon P. , Derrick Peter J. , Chen Su 
Published: May 2005

AbstractStructures of the trifunctional crosslink molecules, pyridinoline, deoxypyridinoline and glucosylgalactosyl‐pyridinoline, have been characterized by positive‐ion liquid secondary‐ion mass spectrometry (LSIMS) and collision‐induced dissociation with scanning‐array four‐sector tandem mass spectrometry. It has been found that: (i) the naturally occurring cations (Cat+) are readily desorbed by positive‐ion LSIMS utilizing glycerol + thioglycerol (1:1) as liquid matrix and dominate the spectra, facilitating accurate mass measurement; (ii) changing the matrix to 3‐nitrobenzyl alcohol leaves little evidence of the cation, and (iii) collision‐induced dissociation of the cations (Cat+) of pyridinoline, deoxypyridinoline and glucosylgalatosyl‐pyridinoline gives a wealth of fragmentation for structure elucidation. These fundamental studies of tandem mass spectra of the known trifunctional crosslink molecules provided valuable structure‐related information, which help in the identification of the tissue‐specific peptides containing these crosslinks. Artefact ions in these tandem mass spectra are remarkably abundant.
A novel hydrogen rearrangement of bifunctional o‐xylylene derivatives in chemical ionization mass spectrometry
Authors: Nakata Hisao , Osogoshi Keisuke , Noda Yasuyo , Abe Ayako , Suzuki Hiroshi 
Published: May 2005

AbstractA novel hydrogen rearrangement reaction was found in benzyl ions that have a (benzyl) group (Z=O or N) at their ortho position. From deuterium labeling experiments, mass analyzed ion kinetic energy spectra with collisional activation, and examination of structure‐peak intensity correlation, a mechanism is proposed which involves a direct transfer of hydrogen (hydride) to the structurally remote but spatially close cationic center. The possibility of an alternative, less likely mechanism including an ion/neutral complex and/or a proton‐bridged complex has also been discussed.
Total yield measurements in matrix‐assisted laser desorption using a quartz crystal microbalance
Authors: Quist Arjan P. , Huth‐Fehre T. , Sundqvist Bo U. R. , Vertes Akos 
Published: May 2005

AbstractA quartz crystal microbalance (QCM) is employed to determine the desorption yield of neutral particles in matrix‐assisted laser desorption ionization. For ferulic acid, the matrix substance used, the QCM mass resolution of 1 ng corresponds to a detection limit of ≈︁1012 particles. Sample exposure effects are studied at different fluences by measuring the total desorption yield after consecutive laser pulses fired on the same spot on the sample. The dependence of the total yield on the fluence is studied for different angles of incidence of the laser beam. Varying the distance between the QCM and the sample yields information about the angular spread of the desorbed neutral particles. Additional information about the fluence threshold for the production of charged particles is gained by direct electronic measurements of sample charging.
Electron impact mass spectrometry of some 5‐amino salicylic acid derivatives
Authors: Rizzi Emanuele , Ferrario Francesco , Sala Alberto , Catinella Silvia , Traldi Pietro 
Published: May 2005

AbstractThe electron impact‐induced fragmentation processes of eleven differently substituted 5‐amino salicylic acids were studied by means of mass‐analyzed ion kinetic energy (MIKE) spectroscopy, parent‐ion spectroscopy and accurate mass measurements. Most of the fragmentation processes are related to the cleavages of the 5‐amino substituents. Unusual behaviour is that related to the CO2 loss from the molecular ion, quite significant in the normal electron ionization spectra and completely undetectable in the MIKE spectra.
Cathodic bombardment and sputtering in the 0.5–4.0 torr pressure region of a glow‐discharge ion source
Authors: Mason Rod S. , Milton Dafydd M. P. , Pichilingi Melanie , Anderson Peter D. J. , Tereza Fernandez M. 
Published: May 2005

AbstractCathodic ion sputtering energies have been studied in a glow‐discharge ion source, operated in the ranges 0.5–2.0 Torr pressure and 100–1000 V discharge voltage using ion kinetic energy spectroscopy. Average energies in the range 10–20 eV were measured. These energies are very low compared with the theoretical prediction of the charge‐transfer model. In view of this, the high sputtering yields measured are surprising. It is inferred that the sputtering is caused, not by the discharge gas ions as is still widely believed, but by fast discharge‐gas atoms. A means of estimating the average energy of the neutral flux is found by comparing presently measured thresholds with Literature values directly obtained. The average energy seems to be about three times greater than that of the ions. The neutral flux is crudely estimated by comparison of the apparent nett sputter yields measured here with tabulated primary values and taking into account back‐diffusion. It is found to be > 100 times larger than the ion flux. The flux created by charge transfer alone is therefore not enough to explain the high sputtering yields measured. Higher energy ions detected and composed mainly of ionized cathodic atoms appear to be formed in a region intermediate between the negative glow and the cathode, which again is different from the generally held view.
Characterization of glucuronic acid conjugates of a novel angiotensin receptor antagonist
Authors: Bowers Gary D. , Eddershaw Peter J. , Hughes Soraya Y. , Manchee Gary R. , Oxford Janet , Games D. E. 
Published: May 2005

AbstractNanogram quantities of glucuronic acid conjugates of GR117289 in rat and dog bile have been analysed by semi‐microbore high‐performance liquid chromatography (HPLC)/ionspray mass spectrometry with on‐line UV diode array detection. The determination of drug metabolites in bile has often proved problematical due to the large number of endogenous components in this biological matrix, in particular the bile acids. Semi‐microbore HPLC is useful for concentrating small quantities of material and, in combination with an on‐line diode array detector, for distinguishing between drug related and endogenous components. A novel angiotensin II receptor antagonist, GR117289, had proved difficult to analyse by thermospray mass spectrometry because of its thermal lability. The use of the less thermally dependent technique of ionspray mass spectrometry allowed the characterization of nanogram quantities of glucuronic acid metabolites of GR117289 in bile.
Halocarbenes as diagnostic tools for mass spectral localization of double bonds
Authors: Schuerch Stefan , Howald Markus , Gfeller Hans , Schlunegger Urs Peter 
Published: May 2005

AbstractDifferent halocyclopropanes prepared by cycloaddition of halocarbenes to olefins by phase‐transfer reactions have been analyzed by gas chromatography/mass spectrometry (GC/MS). Starting from CCl2‐adducts, the investigations have been extended to bromine‐ and fluorine‐containing cyclopropanes. As reaction partners, a group of olefins, containing different alkyl substituents, have been selected. Thereby, special attention has been paid to smooth reaction conditions, high reaction yield and simple handling. The suitability for mass spectral analysis is discussed. Fragmentation pathways and diagnostic potential are evaluated. Best results have been obtained by addition of bromofluorocarbene to double bonds. The resulting bromofluorocyclopropanes are considered to be the most promising derivatives for mass spectral localization of double bonds.
Formation of deprotonated molecules [M—H]− of α‐tocopherol under fast‐atom bombardment conditions
Authors: Takayama Mitsuo 
Published: May 2005

AbstractThe formation of deprotonated molecules, [M—H]−, of α‐tocopherol under fast‐atom bombardment (FAB) conditions has been discussed on the basis of a proton subtraction reaction between analyte and matrix molecules. The use of proton‐accepting matrices such as diethanolamine (DEA) and pentamethyleneglycol (PMG) gave higher intensities of the [M—H]− ion and more definitive spectral data than when other matrices, a 1:2 (v/v) mixture of thioglycerol (TG) and dithiothreitol (DTT), or m‐nitrobenzylalcohol (m‐NBA), were used. The order of proton acceptability evaluated for the matrices used was DEA>PMG>DTT>m‐NBA. It was concluded that the proton acceptability, which is measured by gas‐phase basicity or proton affinity, is a most important factor for the formation of both [M + H]+ and [M—H]− ions under FAB conditions. Further, the formation of molecular ions, M+·, under FAB conditions and the formation of [M—H]− ions by electron impact have been discussed by using α‐tocopherol.
Simple and sensitive quantitation method for mevalonic acid in plasma using gas chromatography/mass spectrometry
Authors: Ishihama Yasushi , Mano Nariyasu , Oda Yoshiya , Hiyoshi Hironobu , Ikuta Hironori , Yoshida Yutaka 
Published: May 2005

AbstractThe combination of gas chromatography and mass spectrometry using a polar capillary column and isobutane chemical ionization made it possible to determine mevalonic acid (MVA) as the lactone at subnanogram levels using 1 mL of plasma. The pretreatment procedure consisted of only three steps, namely lactonization, washing with chloroform and liquid/liquid extraction. This simple, rapid and sensitive method, having good precision and accuracy, is useful for evaluating the change of plasma MVA, which is well correlated with whole‐body cholesterol biosynthesis.
Mass shifts due to ion/ion interactions in a quadrupole ion‐trap mass spectrometer
Authors: Cleven Curtis D. , Cox Kathleen A. , Graham Cooks R. , Bier M. E. 
Published: May 2005

AbstractMass spectra recorded using a Paul ion trap, operated in the mass‐selective instability scan mode, give peak positions which are shown to depend on ion abundance. The isolated molecular ions of benzene, anisole, cresol, and n‐butylbenzene are ejected during the mass selective instability scan at times which display a linear dependence on ion abundance for low populations of trapped ions. Remarkably, the degree to which the peaks are shifted is also compound dependent. Mass shifts are also influenced by the presence of other ions in the trap and this effect is amplified as the mass difference between the analyte and matrix ions decreases. Mass shifts are also affected by the helium pressure which controls the ion density. Extrapolation to zero ion abundance and to zero helium pressure is suggested as a method of eliminating these effects and hence of improving the mass measurement accuracy attainable using the ion trap.
Mass‐selective analysis of ions in time‐of‐flight mass spectrometry using an ion‐trap storage device
Authors: Fountain Scott. T. , Lee Heewon , Lubman David M. , Chen Chung‐Hsuan 
Published: May 2005

AbstractA quadrupole ion trap was used as a front‐end device for selecting specific ions formed via matrix‐assisted laser desorption for analysis in time‐of‐flight mass spectrometry. Using low‐voltage auxiliary RF signals, the ion trap can be used to resonantly eject all but a selected mass‐to‐charge range prior to time‐of‐flight mass analysis. A series of simple analog resonance ejection circuits were developed to provide this selective ion trapping. These circuits use both single‐ and modulated‐frequency waveforms applied directly to the repeller endcap of the quadrupole ion‐trap source in a monopolar fashion. Commercially available waveform generators, as well as a multichannel voltage‐controlled oseillator circuit, were used for resonant ion ejection and ion isolation prior to pulsed extraction into the time‐of‐flight mass spectrometer. The analytical utility of these circuits was tested on a series of biologically active peptides from m/z 700 to 1650 using matrix‐assisted laser desorption/ionization (MALDI) directly into the ion trap. These simple analog circuits were found to provide a number of useful qualitative improvements in the ion‐trap/reflectron time‐of‐flight device including the broadband removal of matrix background ions formed via MAI DI and the isolation of molecular ions from complex peptide mixtures. The utility of this methodology for tandem mass spectrometry, including collision‐induced dissociation and photodissociation, is discussed.
Maximum entropy deconvolution of heterogeneity in protein modification: Protein adducts of 4‐hydroxy‐2‐nonenal
Authors: Bruenner Bernd A. , Daniel Jones A. , Bruce German J. 
Published: May 2005

AbstractTo explore the chemistry of the reactions of the cytotoxic aldehyde trans‐4‐hydroxy‐2‐nonenal (HNE) with proteins, we incubated this aldehyde in vitro with β‐lactoglobulin B, a model protein of molecular weight 18 277 Da. Direct characterization of reaction products using electrospray ionization mass spectrometry yielded spectra whose complexity suggested extensive product heterogeneity. Spectra were transformed to a true mass scale using both a conventional transform algorithm and a maximum entropy algorithm. Both transformations demonstrated the formation of aldehyde‐protein adducts containing from three to nine aldehyde molecules per molecule of protein. Maximum entropy deconvolution resolved Schiff base adducts and/or dehydration products, differing from the Michael addition adducts by 18 Da. The dominant reaction pathway, however, was Michael addition of the aldehyde to nucleophilic functional groups on the protein. The large number of Michael adducts relative to the one available cysteine requires that other amino acids, such as histidine and lysine, also be modified. The data suggest that methods for analysis of HNE that involve displacement of Schiff base groups from proteins will only recover a small fraction of HNE.
An automated liquid chromatography/mass spectrometry system coupled on‐line with microdialysis for the in vivo analysis of contrast agents
Authors: Michelsen Peter , Pettersson Göran , Games D. E. 
Published: May 2005

AbstractAn automated high‐performance liquid chromatography (HPLC)/mass spectrometry instrument coupled on‐line with a microdialysis probe is described for the analysis of contrast agents in biological fluids. This system is used for pharmacokinetic and structure elucidation studies of contrast agents used in X‐ray and magnetic resonance imaging investigations. Additionally an LC/MS system for the direct analysis of urine, that obviates the need for conventional sample clean‐up, is described.
Revealing the mammalian lignan precursor secoisolariciresinol diglucoside in flax seed by ionspray mass spectrometry
Authors: Bambagiotti‐Alberti Massimo , Coran Silvia A. , Ghiara Caterina , Giannellini Valerio , Raffaelli Andrea , Traldi P. 
Published: May 2005

AbstractIonspray mass spectrometry allowed the rapid detection and unambiguous identification of secoisolariciresinol diglucoside, an important mammalian lignan precursor occurring in flax seed. It was observed that this compound is embedded in a complex form, probably a complex glucoside of still undisclosed structure, among the polar solvent extractables of flax seed from which it could not be released as such without the intervention of alkaline methanolysis. Comparison of ionspray mass spectra of untreated and methanolysed flax‐seed extracts confirmed methanolysis as the crucial step in setting up any further analytical or preparative procedure concerned with secoisolariciresinol diglucoside.
An automated, open‐access service to synthetic chemists: Thermospray mass spectrometry
Authors: Brown David V. , Dalton Melanie , Pullen Frank S. , Perkins George L. , Richards Don , Cottee Frank H. 
Published: May 2005

AbstractNuclear magnetic resonance (NMR) and mass spectrometry (MS) are the major spectroscopic tools used by synthetic organic chemists to monitor the steps of their syntheses. Rapid confirmation of the structure at each synthetic step is vital for efficient progress to the desired product. In many laboratories automated open‐access NMR is routine. This often leaves mass spectrometry as a rate‐limiting step in structure confirmation. The key information the chemist needs from a mass spectrum is the relative molecular mass (RMM). We have therefore developed an automated, open‐access thermospray mass spectrometry service, in which a chemist logs a sample into a queue on the mass spectrometer, and a short time later takes the mass spectrum away. The whole process occurs without any intervention by a mass spectrometrist. This has made mass spectra available as rapidly as NMR spectra, so that chemists can obtain the data they need to confirm synthetic structures within less than two hours.
Comparison of peptide analysis results for horse, bovine and dog cytochrome c using capillary electrophoresis/mass spectrometry with untreated capillary column and basic buffer condition
Authors: Takada Yasuaki , Nakayama Kanae , Yoshida Motoko , Sakairi Minoru 
Published: May 2005

AbstractPeptide analysis of cytochrome c using capillary electrophoresis/mass spectrometry was demonstrated to be a rapid, sensitive and useful technique for providing information concerning the location of variation. We analyzed tryptic digests of horse, bovine and dog cytochrome c, and compared the peptide analysis results for information concerning amino acid sequences in proteins. The differences in amino acid sequence were confirmed by taking into consideration that all the other fragments are identical in each map. The use of an untreated capillary column with basic buffer condition (water+acetonitrile+(20 g/L) ammonium carbonate (70/20/10), pH 9.2) had a reproducibility of migration times to within about 2%.
Resolution and spectral‐line shapes in the reflecting time‐of‐flight mass spectrometer with orthogonally injected ions
Authors: Laiko V. V. , Dodonov A. F. , Cotter R. J. 
Published: May 2005

AbstractPrincipal factors limiting the resolution of time‐of‐flight (TOF) mass spectrometers based on ‘orthogonal’ ion beam acceleration have been studied theoretically. It has been found that the construction of the orthogonal acceleration TOF mass analyzer enables, in some cases, the simultaneous compensation of both ion spatial and initial velocity distributions by appropriate selection of ion‐mirror potentials. This analytical result has been proved by numerical simulation of spectral line shapes. The influence of elementary cell dimensions of grids on the mass resolution has been investigated by the numerical integration of a large number of ion trajectories. The grids consisting of a set of parallel and equally spaced wires have been treated. Analytical approximations of the electrical field potential of the grids have been used. It has been found that optimization of TOF mass analyzers should include the treatment of ion scattering by grids.
Investigation of protein‐protein noncovalent interactions in soybean agglutinin by electrospray ionization time‐of‐flight mass spectrometry
Authors: Tang Xue‐Jun , Fred Brewer C. , Saha Sanat , Chernushevich Igor , Ens Werner , Standing Kenneth G. , Chait Brian T. 
Published: May 2005

AbstractNoncovalent interactions in soybean agglutinin (SBA) were studied on an electrospray ionization (ESI) time‐of‐flight mass spectrometer constructed recently at the University of Manitoba. The high m/z range and high sensitivity of the instrument together with mild ESI interface conditions turned out to be ideal for detecting this noncovalently bonded tetrameric protein (MW ∼ 116 000 Da) in low charge states (z=23 to 27). By altering the acetonitrile content of the SBA solutions it was shown that the observed SBA tetramers are due to structurally specific noncovalent associations in solution. Octamers and dodecamers (MW ∼ 350 000 Da) were also detected. Information on the quaternary structure of the tetramers was obtained by analyzing the fragment‐ion spectrum resulting from the collision‐induced dissociation of the tetramer ions.
Determination of molecular structures of photolysis products of substituted aromatic azides in diethylamine solvent by gas chromatography/mass spectrometry
Authors: Senthil Vellala , Soundararajan N. 
Published: May 2005

AbstractWe have photolyzed methyl‐3‐azido‐4‐fluoro benzoate, methyl‐3‐azido‐6‐fluoro benzoate, and methyl‐3‐azido‐4,6‐difluoro benzoate, in neat diethylamine and the resultant products were analyzed by capillary column gas chromatography/mass spectrometry. Two types of products were formed. The first type of product includes substituted anilines and adducts of an aryl nitrene with one molecule of diethylamine. The second type of product includes adducts derived by addition of two molecules of diethylamine to ketenimines with elimination of hydrogen fluoride and also products derived from these with subsequent elimination of hydrogen cyanide molecule. These hydrogen cyanide eliminated products appear to have been formed by secondary photolysis of the initially formed adducts.
High performance liquid chromatography/ionspray mass spectrometry of N‐ethylmaleimide and acrylic acid ester derivatives for bioanalysis of thiol compounds
Authors: Jemal Mohammed , Hawthorne Dara 
Published: May 2005

AbstractHigh performance liquid chromatoraphy/ionspray mass spectra of N‐ethylmaleimide (NEM) and acrylate derivatives of the sulfhydryl compound BMS186716 exhibited a variety of fragmentation patterns, in positive‐ or negative‐ion mode, providing a wide choice of conditions for developing a bioanalytical method based on selected‐ion monitoring. Because the NEM derivative gave two chromatographic peaks (due to two diastereomers) whereas the acrylate derivative gave a single peak, the acrylate derivatization was chosen for further investigations. While BMS186716 in blood or plasma was extremely unstable, the compound could be stabilized by adding methyl acrylate (MA) to the biological matrix, owing to instantaneous reaction to form the stable BMS186716‐MA derivative. This stabilization scheme is being investigated for developing a sensitive bioanalytical liquid chromatographic/mass spectrometric method for BMS186716.
Fragmentation reactions of the trimethylsilyl adducts of C6 ketones
Authors: Bosma Nancy L. , Harrison Alex G. , Munson B. 
Published: May 2005

AbstractThe unimolecular (metastable ion) and collision‐induced fragmentation reactions of the trimethylsilyl cation adducts of six C6 ketones have been studied by tandem mass spectrometry. A major unimolecular fragmentation channel involves regeneration of the trimethylsilyl cation; other fragmentation channels involve elimination of (CH3)3SiOH, C5H10, C4H8 and C3H6 from the adduct ions. Some mechanistic detail has been obtained from a study of the adducts with deuterium‐containing ketones, and the reactions observed are compared with the fragmentation reactions of the protonated ketones. Collision‐induced dissociation (CID) of the adduct ion results in predominant formation of (CH3)3Si+. However, in the high energy (6 keV) CID new minor reaction channels, involving elimination of alkanes, CH4 to C4H10, become accessible. It is concluded that tandem mass spectrometry of the trimethylsilyl adducts provides only limited ability to distinguish between isomeric ketones.