bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct chemical ionization mass spectrometry of short‐chain polysaccharides
Authors: Metzger J. O. , Bruns‐Weller E. 
Published: May 2005

AbstractUnderivatized short‐chain polysaccharides such as two inulins from different plants containing up to 35‐40 monosaccharide units with molecular weights of up to 6500 Da and dextran T 1.5 containing up to 16‐20 monosaccharide units with molecular weights of up to 3200 Da have been investigated by direct chemical lionization. Under soft ionization conditions such as ammonia chemical ionization and reduced ion‐source temperature, it was possible to obtain spectra of the native polysaccharides showing dominant ion series corresponding to ammonia adduct ions of oligosaccharides, and also ion series corresponding to ammonia adduct ions of anhydro‐oligosaccharides.
Secondary‐ion and electron production from surfaces bombarded by large polyatomic ions
Authors: Martens J. , Ens W. , Standing K. G. , Verentchikov A. 
Published: May 2005

AbstractHeavy molecular ions with energies in the range 10–20 keV and masses from 276 u to 132 000 u, produced by matrix‐assisted laser desorption, were used as primary projectiles to produce secondary‐ion spectra from a variety of surfaces ina tandem time‐of‐fight mass spectrometer. In the negative mode the ratio of electron emission to secondary‐ion emission was found to decrease rapidly with increasing projectile mass. Ion emission was found to dominate for primary ions larger than ∼ 10 000 u. Positive or negative molecular ions and cations were observed from several organic targets of masses up to 1140 u (gramicidin S) for incident projectiles up to mass 132 000 u, i. e., for projectile speeds down to ∼7000 m/s. Other ions characteristic of the target were also observed for these projectiles. Thus, large polyatomic ions can cause secondary‐ion desorption even at very low velocity. The background ions of both polarities are similar to those found in keV particle bombardment by monatomic projectiles. The same ions are observed for all the projectiles; most can be identified with hydrocarbon background. The relative intensities of the background positive ions are largely independent of projectile, and for both polarities the ratio of the ions characterizing the target to those forming the background is approximately constant for all the projectiles. These results strongly suggest that the background ions come from the usual layer of organic impurities attached to the target surface. No direct evidence for surface‐induced dissociation was observed in this mass and energy range.
Protein structural effects in gas phase ion/molecule reactions with diethylamine
Authors: Loo Rachel R. Ogorzalek , Loo Joseph A. , Udseth Harold R. , Fulton John L. , Smith Richard D. 
Published: May 2005

AbstractThe relationship between gas‐phase protein structure and ion/molecule reactivity is explored in comparisons between native and disulfide‐reduced aprotinin, lysozyme, and albumin. Reactions are performed in the reactions with equal concentrations of diethylamine, multiply protonated molecules generated by electrospray ionization (ESI) of ‘native’ proteins shifted to lower charge states than did multiply protonated molecules from ESI of the disulfide‐reduced counterparts, suggesting that the disulfide‐reduced protein ions are less reactive than native protein ions of the same charge state. Differences in reactivity may arise from protonation of different amino acid residues and/or differences in the proximites of charge sites in two molecules. These results suggest that the reactivity of multiply charged proteins can be significantly affected by their gas‐phase structure.
Modification of a commercial thermospray interface controller to improve ion‐current stability
Authors: East Philip B. , Eckers Christine , Haskins Neville J. , Hare John F. , James Phillip J. 
Published: May 2005

AbstractThe stability of the ion beam in a thermospray interface is largely dependent on the control of the vaporizer temperature. The original time‐proportional vaporizer control circuit provides inadequate temperature stabilization. Modification of the circuit by repositioning the thermocouple amplifier and replacing the time proportional part of the circuit with a phase‐angle controller greatly improves the temperature stability and hence th ion‐current stability. The improvement in performance was demonstrated using terbutaline as a test substance.
Observation of MH+, MO+, MOH+, MH−, MO− and MOH− Ions (M=C60 and C70) in fast‐atom bombardment mass spectra of fullerenes
Authors: Miller Jack M. , Chem Lin‐Zhi 
Published: May 2005

AbstractC60 and C70 in 3‐nitrobenzyl alcohol and 2‐nitrophenyloctylether have been investigated using both positive‐ and negative‐ion fast‐atom bombardment spectrometry. In addition to the ions, MH+, MO+ and MOH+, and corresponding MH−, MO− and MOH− ions (MC60, C70) other ions were observed in the positive‐ and negative‐ion mass spectra. Collision‐induced dissociations of the MO+ and MOH+ ions produced the fullerene ions, indicating that the oxygen and hydroxyl were connected to the convex external surface of the fullerenes.
Matrix‐assisted laser desorption with ultra‐short laser pulses
Authors: Demirev P. , Westman A. , Reimann C. T. , Håkansson P. , Barofsky D. , Sundqvist B. U. R. , Cheng Y. D. , Seibt W. , Siegbahn K. 
Published: May 2005

AbstractAn excimer pumped dye laser generating ultra‐short (560 fs full width at half maximum, FWHM) pulses in the ultraviolet (UV, 248 nm) and visible (496 nm) spectral ranges is used to desorb protein ions from different matrices. The effects of laser‐light energy and power density on secondary‐ion yields from insulin are reported. These data are compared to data obtained by employing a nitrogen laser (337 nm, 3 ns FWHM). The existence of a threshold energy density for the matrix‐asisted laser desorbtion (MALD) of insulin ions by the ultra‐short pulses is established. This threshold energy is of the same order of magnitude for the two laser systems employed and does not depend on the laser pulse length (the energy deposition time). Thus we demonstrate that the amount of laser energy deposited into the sample, rather than the laser power, is the important parameter in the MALD process.
C60 and C70 fullerene isomers generated in flames. Detection and verification by liquid chromatography/mass spectrometry analyses
Authors: Anacleto Joseph F. , Perreault Hélène , Boyd Robert K. , Pleasance Stephen , Quilliam Michael A. , Sim P. Greig , Howard Jack B. , Makarvovsky Yakov , Lafleur Arthur L. 
Published: May 2005

AbstractFullerenes C60 and C70, generated by combustion, have been shown previously to be produced in controlled laminar flames accompanied by other compounds having fullerene‐like characteristics. Analysis of these additional compounds by hith‐performance liquid chromatography, coupled on‐line with mass spectrometry has identified them as isomers of the C60 and C70 fullerenes. The newly observed isomers have characteristic UV spectra and are thermally unstable, undergoing conversion to the more stable fullerenes with a half‐life of about 1 h in boiling toluene (111°C). Isomers of C60 and C70 fullerenes previously have been studied theoretically, but not observed experimentally. The flame‐generated material also contains C60O and C70O compounds, as well as C76 and higher carbon clusters.
Matrix‐assisted laser desorption/ionization of high‐mass molecules by Fourier‐transform mass spectrometry
Authors: Castro John A. , Köster Claus , Wilkins Charles , Cotter R. J. 
Published: May 2005

AbstractFollowing the first demonstrations of high‐mass analysis using time‐of‐flight matriz‐assisted laser desorption/ionization (MALDI) techniques by Hillenkamp,1,2 Tanaka3 and their co‐workers, there have been significant efforts in a number of laboratories to adapt the new methodology to Fourier‐transform mass Spectrometry (FTMS). The motivation fsor this research is obvious. Namely, it would be desirable to couple the unparalleled high mass resolution of FTMS4 with the extended mass range proveded by MALDI, paricularly for analysis of polymers and biomolecules. Unfortuanately, Prior to the presnt work, attempts to mate FTMS and MALDI have met with limited success. The highest mass matrix‐assisted laser‐desorption‐FTMS result previously obtained appears to be the unpublished low resolution spectrum of bovine insulin recently reported by russell co‐workers.5 We,6 Campana and co‐workes,7 and Hettich and Buchanan8,9 have had some sucess with MALDI‐FTMS of biomolecules with masses lower than 3000 Da.9 Fruthermore, with single exception of Campana's report of obtaining mass resolutiojn of 5000 for the moleculer ion of melittin,7 such spectra have not displayed high resolution. Here, we report successful development of MALDI‐FTMS, demonstrated with spectra obtained from a variety of high‐mass polymer and biomolecule samples, using 355nm radiation from an excimer‐pumped dye laser for desorption/ionization and sinapinic acid as matrix, Some of these spectra are of much higher mass resolution than is possible with current time‐of flight mass spectrometers.
Negative‐mode electrospray‐mass spectrometry using nonaqueous solvents
Authors: Hiraoka Kenzo , Kudaka Ichiro 
Published: May 2005

AbstractNonaqueous solvents suitable for negative‐mode electrospray‐mass spectrometry were investigated. Mixtures of methanol with benzene and with carbon tetrachloride were found to be the best solvents. Negative ions of 10−9 M concentrations of surface‐active agents in these solutions could be detected.
The implementation and application of precursor‐ion scanning using a four‐sector instrument
Authors: Scrivens J. H. , Rollins K. , Jennings R. C. K. , Bordoli R. S. , Bateman R. H. 
Published: May 2005

AbstractPrecursor‐ion scanning, in which all ions that fragment to form a selected product ion are detected, has been implemented on a four‐sector instrument. The various experimental parameters associated with the experiment i.c., prcursor mass range, product and precursor ion resolution, collision energy and mass‐measurement accuracy have been established via a series of experiments, Brief examples of the use of the technique in the characterization of synthetic polymers, quaternary salts and peptieds are described together with the analysis of a mixture of phthalate esters.
Optimization of sample deposition for plasma‐desorption mass spectrometry of peptidoglycan monomers
Authors: Allmair Günter , Caparros Marta Rodriguez , Pittenauer Ernst 
Published: May 2005

AbstractThree selected peptidogycan monomers isolated from muramidase‐digested Escherichia coli‐sacculus were characterized by positive‐ and negative‐ion 252Cf plasma‐desorption mass spectrometry (PDMS). Dut to the high affinity of sugar moieties towards alkali cations multiple alkali attachment in PDMS can be a problem. Electrospray, nitrocellulose, nitrocellulose sandwich anthracene‐9‐carboxylic acid 3‐(3‐Pyridyl)acrylic acid deposition techniques were evaluated for the degree of (de)proltonation and cationization of the molecular species by sodium and/or potassium. Electrosprayed and nitrocellulose‐deposited samples mainly exhibited intense cationized molecular ion species whereas anthracene‐9‐caboxylic acid‐deposition sample show a similar pattern but with much lower intensity. An extension of the nitrocellulose deposition technique, the so‐called nitrocellulose sandwich sample preparation reduced the aallkali attachment problem for these hydrophilic compounds. Application of the small molecule matrix 3‐(3‐pyridyl)acrylic acid yielded mass spectra with abundant [M+H]+ and [MH]− ions in the positive‐ and in the negative‐ion modes, respectively.
Matrix‐assisted laser desorption using a fast‐atom bombardment ion source and a magnetic mass spectrometer
Authors: Annan Roland S. , Köchling Heinrich J. , Hill James A. , Biemann Klaus 
Published: May 2005

AbstractA conventional fast‐atom bombardment (FAB) ion source was used to achieve matrix‐assisted laser desorption (MALD) in a high‐mass, double‐focusing, magnetic mass spectrometer. The pulsed ion signals generated by irradiation of a mixture of sample and matrix (2,5‐dihydroxybenzoic acid) with either a XeF excimer Laser (353 nm) or a nitrogen laser (337 nm) were recorded with a focal‐plane detector. A resolution (full‐width at half maximum) of 4500 was achieved at m/z 1347.7 (the peptide substance P), 2500 for CsI cluster ions at m/z 10005.7, and 1250 for the isotope cluster of the small protein cytochrome c (horse) [M+H]+=m/z 12360 (average). Sensitivity is demonstrated with 11 fmol of substance P. A survey scan is taken to prodluce a better signal‐to‐noise ratio. In addition to higher sensitivity and lower matrix interference, lthe advantage of MALD over FAB is the former's lower susceptibility to the presence of salts, and competition between hydrophobic and bydrophilic components of a mixture. This feature is demonstrated by the complete MALD spectrum of a crude partial tryptic digest of spedrm‐whale apomyoglobin, containing 24 peptides, representing the entire sequence of this protein.
Control of ion kinetic energy in ion cyclotron resonance spectrometry: Very‐low‐energy collision‐induced dissociation
Authors: Boering Krisltie A. , Rolfe Joseph , Brauman John I. 
Published: May 2005

AbstractA novel means of effecting collision‐induced dissociation of molecular ions for use in conjuction with Fourier‐transform ion cyclotron resonance (FT‐ICR) mass spectrometry is reported. Using an electronic circuit external to the ICR hardware and software, ions are continuously acceperated and decelerated over a period of hundreds of milliseconds by rledpreatedly shifting the phase of the radio frequency excitation driving signal by 180°. At low kinetic energies, a succession of collisions which transfer small amounts of energy favors the lowest energy fragmentation pathway and allows ions with large activation energies to fragmentation of n‐butylbenzene cation and by extremely large secondary isotope effects in the dissociation of t‐butoxide‐d6 anion.
Gas‐phase silane oligomerization by the isovalent rare earth ions Sc+, Y+ and Lu+
Authors: Azzaro M. , Breton S. , Decouzon M. , Geribaldi S. 
Published: May 2005

AbstractThe gas‐phase reactions between silane and three isovalent metal ions Sc+, y+ and Lu+ are investigated using a Fourier‐transform ion cyclotron resonance mass spectrometer. In contrast to its carbon analogue methane, silane exhibits very different behaviour towards these three metal ions. Lu+ is unreactive sdtowards silane even with a translational activation of the metal ion. The reaction is slow and endothermic with Sc+. It leads first to the formation of ScH+, and ScSIH, and then to the formation fo ScSiH. Slow sequential reactions are observed with the ion ScSiH to give ScSinH, ScSinH, ScSinH and ScSi up to a value of n=3. By contrast to Sc+, only the emtal silylene ion YSiH is observed in the tirst step of the rapid and exothermic reaction of Y+ with silane. YSiH then undergoes a rapid sequintial reaction to give YSinH and YSinH, ions up to a value of n=7.
Extraction and mass spectroscopic characterization of giant fullerences up to C500
Authors: Shinohara Hisanori , Sato Hiroyasu , Saito Yahachi , Izuoka Akira , Sugawara Tadashi , Ito Hiroyuki , Sakurai Tohru , Matsuo Takekiyo 
Published: May 2005

AbstractA series of very large all‐carbon molecules has been successfully extracted with quinoline from fullerene‐rich carbon soots produced by the vaporization of graphite in a helium atmosphere using the contact are method. The present extracts (black powder) were found not to be soluble either in benzene or toluene, which are normally used as extraction solvents for C60 and C70. The secondary ion mass spectrum (SIMS) of the extracts reveals that they contain a series of even‐numbered gigantic carbon molecules C70+2n (n⩾1) up to at least C500. The SIMS spectra exhibit a remarkably wide distribution of carbon molecules which has a broad maximum at around C130‐C150. The possibility of the isolation of such large carbon molecules, which are possibly fullerenes, is also presented.
The determination of low d5‐phenylalanine enrichment (0.002–0.09 atom percent excess), after conversion to phenylethylamine, in relation to protein turnover studies by gass chromatography/electron ionization mass spectrometry
Authors: Calder A. G. , Anderson S. E. , Grant I. , McNurlan M. A. , Garlick P. J. 
Published: May 2005

AbstractA gas chromatography/mass spectrometry (GC/MS) method for measuring very low levels of enrichment of d5‐phenylalanine (0.002–0.09 atom percent excess) is described. This method makes it possible to determine the enrichment of amino acid incorporated into tissue protein during studies of protein synthesis in man. Phenylalamine is enzymatically converted to phenylethylamine and the d5‐enrichment is measured in the heptafluorobutyryl derivative by selective‐ion recording under electron ionization conditions. The coefficients of variation for muscle‐protein hydrolysate samples enriched with d5‐phenylalanine at the 0.005 and 0.05 atom percent excess levels were 6.0 and 1.2%, respectively. This precision at low enrichment and the small amount of contrast to the conventional approach which uses GC/MS for plasma amino acids (typically 2–20 atom percent excess) but gas isotope‐ratio mass spectrometry for protein‐bound amino acids, the enrichment of both plasmafree and protein‐bound d5‐phenylalanine can be measured with a single instrument.
The proton bound association of large multifunctional group molecules: Tartaric acid esters
Authors: Honovich J. P. , Karachevtsev G. V. , Nikolaev E. N. 
Published: May 2005

AbstractThe kinetics fo production of proton‐bound dimers of dimethyl‐ and diisopropyl‐tartrate were analyzed were analyzed by the method of initial slopes. From the pressure dependence of the apparent bimolecular rate constatn, the back‐dissociation rate and radiative stabilization of the intermediate excited collision complex was calculated. The back‐dissociation (10.3 and 2.8 × 10 3s−1) and radiative (8.2 and 7.1 s−1) rates are compared to literature values for functionally similar acetone. In contrast to acetone these dimers exhibit a back‐dissociation reaction to regenerate the monomer species. These results can be taken to imply a lower binding energy in these dimers due to steric effects. Competing reactions to form ions of m/z 145 and 235 were also observed for the dimethyl and diisopropyl ester, respectively.
Identification of phospholipid molecular species containing two fatty acyl chains differing by 2 Da by negative‐ion fast‐atom bombardment with mass‐analyzed ion kinetic energy analysis
Authors: Chen Su , Curcuruto Ornella , Catinella Silvia , Traldi Pietro 
Published: May 2005

AbstractIsomeric glycerophosphatidylcholine molecular species containing fatty acyl chains differing by 2 Da (1‐stearoyl‐2‐oleoyl‐ and 1‐oleoyl‐2‐stearoyl‐sn‐glycero‐3‐phosphocholine) can be identified by the determination of trhe fatty acid chain esterified to the sn‐1 position in the glycerol backbone based on the electric sector voltage differences of [M‐86‐R2COOH]− anions derived from phosphatidic acid parent ions (M minus choline group) produced by negative‐ion fast‐atom bombardment combined with mass‐analyzed ion kinetic evergy analyses. Three volt differences can be observed in the spectra. The study further demonstrates that this approach is also effective in distinguishing such molecular species as isomers of glycerophosphatidic acid, glycerophosphatidyl‐ethanolamine and glycerophosphatidylserine and in characterizing the molecular species, differing by 2 Da, of the bovine brian glycerophosphatidylserine (1‐stearoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphoserine) and the rabbit kidney glycerophos‐phatidylethanolamine (1‐oleoyl‐2‐linoleoyl‐sn‐glycero‐3‐phosphoethanolamine).
High‐performance anion‐exchange chromatography/thermospray mass spectrometry in the analysis of oligosaccharides
Authors: Niessen W. M. A. , van der Hoeven R. A. M. , van der Greef J. , Schols H. A. , Lucas‐Lokhorst G. , Voragen A. G. J. , Bruggink C. 
Published: May 2005

AbstractThe on‐line coupling of high‐performance anion‐exchange chromatography mass spectrometry is described. The system is applied to the analysis of neutral and acidic oligosaccharides obtained by (enzymic) degradation of plant‐cell‐wall polysaccharides. The features, potential and limitations of the method are discussed and exemplified with the analysis of some glucuronoxylan and xyloglycan digests. The system allows rapid molecular‐mass determination of components in oligomer mixtures with 1–10 μg injected amounts.
An approach to the quantiative study of reduction processes occurring in fast‐atom bombardment/liquid‐assisted secondary‐ion mass spectrometry
Authors: Bertrand Michel J. , Visentini J. , Paul G. J. C. , Zidarov D. 
Published: May 2005

AbstractAn Approach which allows the determination of the specific effects of experimental parameters on the extent of reduction observed in fast‐atom bombardment/liquid‐assisted secondary‐ion mass spectrometry (FAB/LSIMS) has been developed. The methodology is based on the isolation of the different components‐background, reduction extent, and isotopic abundances—which contribute to peak intensities in the molecular‐ion cluster. The individual contributions of reduction and background are calculated by an algorithm SRBC (simulated reduction and background calculations) which utilizes a Monte‐Carlo method to optimize the values obtained for these variables. This approach has been used to examine the effects of analyte concentration, primary‐beam energy and beam density on the extent of reduction in FAB/SIMS experiments. The results obtained indicate that the beam energy has no significant effect on the apparent reduction, as measured by the experimental (A+2)/A isotope peak ratio, while analyte concentration and beam density effects are obseerved. However, background and reduction data generated by SRBC demonstrate that in some cases there is little effect of these parameters on the true reduction of the analyte and that the increase in apparent reduction with the variation in these parameters results mainly from an artefact created by an increase in the background signal at lower concentrations and higher beam densities.
The chemistry of transition‐metal ion interactions with cyclohexylamine in the gas phase
Authors: Chen Lin‐Zhi , Miller Jack M. 
Published: May 2005

AbstractThe formation of transition‐metal ion (M+Fe+, CO+, Ni+ and Mn+) complexes with cyclohexylamine (1) in a modified fast‐atom bombardment (FAB) source, and the reactions of various ion/molecule complexes, have been studied by FAB MASS spectrometry combined with metastable ion and collisional activation techniques. Multiples dehydrogenations to produce [(aniline)·M]+ and consecutive [2H2+NH3] elimination to afford [(benzene)·M]+ from 1 prevail for all the metal ions studied. Furthermore, [(1)·][Ni]+ and [(1)2·Co]+ ions underwent an unusual NH3 loss. Relative reactivities of the metal ions and complicated ligand effects are presented.
Efficient trapping and collision‐induced dissociation of high‐mass cluster ions using mixed target gases in the quadrupole ion trap
Authors: Morand Kenneth L. , Cox Kathleen A. , Cooks R. Graham 
Published: May 2005

AbstractHeavy target gases (neon, argon, krypton or xenon), when added in small amounts to the helium buffer gas in the quadruple ion trap, improve both the trapping efficiency of cesium iodide cluster ions of high mass‐to‐charge ratio and the internal energy deposition during collision‐induced dussociation experiments.