bluuebunny/crossref_metadata_2025_split huggingface dataset:
Singlet/Triplet excitation (X1∑+→a3IIr) of CO by N+ and O+˙
Authors: Lee A. R. , Enos C. S. , Brenton A. G. 
Published: May 2005

AbstractVibrational excitation of CO by N+ and O+˙ is investigated by means of high‐resolution translational energy spectroscopy. The spectra display unusual features which are discussed in relation to the Wigner spinconservation rule. Reaction channels involving CO (X1Σ+→a3Πr) are prominently featured.
The gas phase benzilic acid rearrangement
Authors: Hayes Roger N. , Eichinger Peter C. H. , Bowie John H. 
Published: May 2005

AbstractReaction of benzil with HO− in the chemical ionization source of a triple‐analyser mass spectrometer forms a [benzl + HO−] ion. This ion, upon collisional activation, gives a mass spectrum identical to that obtained from deprotonated benzilic acid under the same experimental conditions.
Analysis of multi‐domain cellulolytic enzymes by UV‐laser induced desorption mass spectrometry
Authors: Perera I. K. , Uzcategui E. , Håkansson P. , Brinkmalm G. , Pettersson G. , Johansson G. , Sundqvist B. U. R. 
Published: May 2005

AbstractThis paper reports the application of matrix‐assisted UV‐laser induced desorption (LID) mass spectrometry for the analysis of some extracellular multi‐domain cellulolytic enzymes, in the molecular weight range 5000–90 000 u, produced by the fungi Phanerochaete chrysosporium and Trichoderma reesei. A high sensitivity (1–10pmol of protein), has been attained in obtaining the mass spectra of these highly glycosylated enzymes and some of their peptides, with carbohydrate content in the 10–40% range. The desorption of samples containing the enzymes mixed with a protein having an accurately known molecular weight—an internal calibrant—is also demonstrated. Spectra from complete enzymes and their functional domains are presented to explore the possibilities of employing LID for obtaining structural information.
Fast‐Atom bombardment mass spectrometry and collisional spectroscopy in the structural characterization of underivatized 1,4‐benzodiazepines
Authors: Ghezzo E. , Traldi P. , Minghetti G. , Cinellu M. A. , Bandini A. L. , Banditelli G. , Zecca L. 
Published: May 2005

AbstractFast‐atom bombardment (FAB) mass spectrometry linked with collision spectroscopy has been employed for the structural characterization of eight underivatized 1,4‐benzodiazepines. Both positive‐ and negative‐ion FAB led, in all cases examined, to the production of abundant molecular species. Collision experiments performed on such ions gave rise to the identification of diagnostic fragment ions, that could be related to the original structure.
Artifacts in four‐sector tandem mass spectrometry
Authors: Falick A. M. , Medzihradszky Katalin F. , Walls F. C. 
Published: May 2005

AbstractSeveral types of artifacts were shown to be present in 4‐sector tandem collision‐induced dissociation (CID) mass spectra. In CID spectra of protonated peptides produced by liquid secondary‐ion mass spectrometry (LSIMS), peaks corresponding to successive losses of matrix molecules from the precursor ion were observed. In addition, peaks corresponding to MH+ ions of smaller peptides that were also present in the sample/matrix mixture in greater abundance than the selected precursor ion were observed. Both of these types of artifact peaks were shown to originate from the ‘peak‐at‐every‐mass’ chemical noise at the same nominal mass as that selected by the first 2 sectors (MS1). These noise ions are transmitted through to the collision cell and produce fragments that are analysed and detected in the next 2 sectors (MS2). A second, unrelated, kind of artifact was found to be due to decompositions in the second field‐free region of MS2 in an EBEB geometry machine. These artifacts, which are detectable over only a very limited mass range when using a conventional single‐point detector, can be present over a much greater mass range when an array detector is used and when the collision cell is floated above ground potential. A clear understanding of the origins of all peaks in a CID spectrum is important in order to have a firm foundation for interpretation, manual or computer‐aided, of the spectra of unknown compounds.
Radical identification by liquid chromatography/thermospray mass spectrometry
Authors: Iwahashi Hideo , Parker Carol E. , Mason Ronald P. , Tomer Kenneth B. 
Published: May 2005

AbstractRadical adducts of 5,5‐dimethyl‐1‐pyrroline N‐oxide (DMPO) with hydroxyl, methanol‐derived, and ethanol‐derived radicals were detected by a combination of liquid chromatography with either electron paramagnetic resonance or thermospray mass spectrometry (LC/EPR or LC/TSP‐MS) in the Fenton system (with methanol or ethanol). One radical adduct was observed in the reaction of DMPO with the hydroxyl radical or the methanol‐derived radical, while two adducts were detected in the reaction of DMPO with ethanol‐derived radicals. The LC/TSP‐MS spectra showed quasi‐molecular ions [M+H]+ at m/z 146 and m/z 160 for the methanol‐derived and ethanol‐derived radical adducts, respectively, and an apparent molecular ion M+ at m/z 130 for the hydroxyl radical adduct. Use of methyl‐D3 alcohol (CD3OH) and ethyl‐D5 alcohol (CD3CD2OH) indicated that carbon‐centered radicals are formed. Experiments with partially deuterated ethanol (CD3CH2OH and CH3CD2OH) indicated that the two adducts observed in the reaction of DMPO with ethanol‐derived radicals correspond to the two diastereomeric adducts of DMPO with the α‐hydroxyethyl free radical.
An experimental determination of the energy of the first triplet doubly‐ionized state of ammonia
Authors: Griffiths W. J. , Harris F. M. 
Published: May 2005

AbstractThe double‐ionization energy of NH3 to the first triplet state of the dication has been measured by double‐charge‐transfer spectroscopy using OH+ as the projectile ion. The value determined, 37.9±0.5 eV, is in excellent agreement with that calculated by Tarantelli et al. [Chem. Phys. Lett. 117, 577 (1985)] using the configuration interaction method.
Ion optical considerations in tandem mass spectrometry
Authors: Boerboom A. J. H. 
Published: May 2005

AbstractA review of tandem sector‐field mass spectrometers is given with features of various combinations of electric and magnetic sector fields and quadrupole lenses and, eventually, a Wien filter. In particular, a tandem mass spectrometer is described, constructed at Amsterdam, with post‐acceleration, variable dispersion and array detection. The simultaneously‐detected mass range varies from 1:1.06 through 1:12, the resolution in the second stage amounts to 1000 (single‐focusing), the dynamic range is 5000:1, and the sensitivity is such that less than 1 fmol of sample can be detected and identified.
A new gas chromatography/tandem mass spectrometry method for analysis of monoaromatic steroids in petroleum
Authors: Nali M. , Corana F. , Riva A. , Albrecht P. , Wehrung P. 
Published: May 2005

AbstractA new gas chromatography/tandem mass spectrometry (GC/MS/MS) analytical approach for monoaromatic steroids is described in comparison with a more conventional GC/MS analysis. Some examples are reported both on standards and on real samples.
Collision‐activated dissociation studies of alkylamines formed from copper‐induced dealkylation of N‐alkylporphyrins
Authors: Naylor Stephen , Gibbs Anthony H. , Lamb John H. , De Matteis Francesco 
Published: May 2005

AbstractA low‐energy (5–450 eV) collision‐activated dissociation (CAD) study of a series of aliphatic amines revealed that at collision energies above 200 eV, charge‐site‐initiated fragmentation occurs. The resulting fragment ions can be utilized in the characterization of alkyl substituents of di‐ and trisubstituted aliphatic amines. In the presence of Cu2+ and a suitable nucleophile, such as n‐dodecylamine, N‐alkyl protoporphyrins dealkylate to afford copper protoporphyrin and an alkyl‐dodecylamine adduct. A CAD study of a number of alkyl‐dodecylamine adducts derived from the copper‐induced dealkylation of synthetic N‐alkyl protoporphyrins, using charge‐site‐initiated fragment ions, showed that the alkyl group was trapped by the nucleophilic amine present. Subsequently this method was used to identify the alkyl group of a biologically derived N‐alkyl protoporphyrin.
The use of tandem mass spectrometry as a problem‐solving tool in the industrial environment
Authors: Rollins K. , Scrivens J. H. , Jennings R. C. K. , Morden W. E. , Welby J. K. , Bateman R. H. 
Published: May 2005

AbstractThis paper deals with a number of the benefits associated with a variety of tandem mass spectrometer geometries and the way in which these configurations have been applied to the solution of real problems. It discusses the use made of a variety of tandem mass spectrometry approaches to the study of analytical problems of industrial relevance. ICIs utilization of tandem mass spectrometry has grown substantially from an initial involvement in the early 1980s to a point where a number of instruments have been installed and used predominantly for trace analysis, structural studies and in the characterization of complex mixtures. We have selected a small number of examples of the use of the various tandem mass spectrometry approaches emphasizing the unique features of the technique.
Use of triethylammonium formate to enhance sensitivity in negative‐ion liquid chromatography/thermospray‐mass spectrometry
Authors: Steffenrud S. , Dewey Elisabeth , Maylin G. 
Published: May 2005

AbstractThe major objective of this investigation was to find a thermospray buffer that would decrease ion/molecule reactions in the gas phase. This would cause solution chemistry and ion evaporation to be major parameters controlling ion production. Using triethylammonium formate, protonation by ion/molecule reaction in the gas phase was decreased as indicated by the effect of solution pH on ion production. The detection limits in the full‐scan mode for some amphoteric compounds and acids were one magnitude lower than those obtained with ammonium acetate or ammonium formate buffers. A few examples of sensitive full‐scan detection demonstrate the usefulness of this novel buffer for negative‐ion thermospray liquid chromatography/mass spectrometry.
Characterization of cyclodextrins using ion‐evaporation atmospheric‐pressure ionization tandem mass spectrometry
Authors: Huang Eric C. , Henion Jack D. 
Published: May 2005

AbstractA tandem mass spectrometer equipped with the pneumatically‐assisted electrospray (ion spray) liquid chromatography/mass spectrometry interface and an atmospheric‐pressure ionization source was used for characterization of underivatized cyclic oligosaccharides. Protonated singly charged molecular ions were generated via ion‐evaporation mechanism(s). The formation of doubly charged molecular ions from the model compounds appears to be related to the channel diameter of these cyclic oligosaccharides. Tandem mass spectrometry (MS/MS) was used to study collision‐induced dissociation of the protonated molecule and showed exclusive cleavage of the glycosidic bond. The molecular weights of these oligosaccharides as well as the number of sugar units were confirmed by MS/MS. The potential application of MS/MS for target compound analysis was demonstrated by the parent‐ion scan method with a synthetic mixture.
Magic numbers in kinetic energy releases for unimolecular decompositions of proton‐bound acetone and acetone/water clusters
Authors: Lifshitz C. , Iraqi M. , Peres T. 
Published: May 2005

AbstractMagic numbers were observed for kinetic energy releases (KERs) upon desolvation of proton‐bound neat acetone clusters and mixed acetone/water clusters. The results for the neat clusters are successfully reproduced by the evaporative ensemble model of Klots. We conclude that the phenomenon is general, namely that the KER for a series of clusters goes through a maximum for the cluster of size n having special stability.
On the formation of doubly charged fragment and cluster ions of oxygen‐ and sulfur‐containing substances in field ionization and field desorption mass spectrometry
Authors: Kosevich M. V. , Shelkovsky V. S. 
Published: May 2005

AbstractThe appearance of doubly charged molecular, fragment and cluster ions in the field desorption and field ionization mass spectra of thiotepa are discussed. A comparison with the field‐desorption mass spectra of some other oxygen‐ and sulfur‐containing compounds is made and the conclusion reached, that the formation of doubly charged fragment [MO]2+, [MS]2+, and cluster [(MO)M]2+, [(MS)M]2+ ions is a characteristic behaviour of several types of substances containing O and S groups under the conditions of high electric field.
Gas chromatography/mass spectrometry in the elucidation of the structure of piperidine alkaloids
Authors: Maksimović Mirjana , Šober Miroslav , Nikolin Branko 
Published: May 2005

AbstractPiperidine heterocycles are present in the structure of many alkaloids, for example coniine in the structures of lobelia, cocaine alkaloids and sedum alkaloids, Sedum alkaloids are 2,6‐disubstituted derivatives of piperidine or N‐methylpiperidine. Extracts obtained from Sedum acre L. were investigated for the presence of alkaloids by gas chromatography/mass spectrometry. Identification has been carried out on the basis of retention time, molecular ion mass and characteristic fragmentation. Investigated extracts contained unknown alkaloids which belong to the piperidine group of sedum alkaloids. Mass spectral fragmentation patterns and a proposed structure for the unknown alkaloids are discussed.
Electrospray interface for liquid chromatography/mass spectrometry
Authors: Hiraoka Kenzo , Kudaka Ichiro 
Published: May 2005

AbstractThe positive and negative ions produced by electrospray atomization from solutions of various molecules were detected using a high‐pressure quadrupole mass spectrometer. The electrospray interface for liquid chromatography/mass spectrometry was investigated in various respects, i.e., the effect of needle voltage on the total current, solvent dependence, the effect of surrounding gas, gas temperature, and the sensitivity of detection of mass‐analysed ions. In the positive‐ion mode, the detection limits of ionic samples in solution are found to be lower than the order of parts per billion. The addition of CCl4 in solution inhibits a breakdown to discharge at the needle tip and makes it possible to electrospray at much higher needle voltages. It was found that neutral samples in solutions with concentrations of ≥ 10−4 M could easily be detected by producing a small corona discharge on the tip of the liquid cone (atmospheric pressure ionization).
Sequence‐specific fragmentation from oligopeptides using plasma‐desorption mass spectrometry
Authors: Buko Alexander M. , Sarin Virender K. 
Published: May 2005

Abstract252Cf plasma‐desorption mass spectrometry (PDMS) has been demonstrated to provide sequence‐specific fragmentation for several oligopeptides. The nature of the fragment ions observed is generally similar to that observed using liquid secondary‐ion mass spectrometry (LSIMS) and can be observed using less sample than LSIMS requires, but PDMS spectra are acquired at a lower resolution. In addition, the molecular weight of some of the oligopeptides studied exceeds that which is generally accepted as within the sequence range of LSIMS. The specific series of sequence ions that predominate in the PDMS spectra appear to be related to the amino acid compositions and sequences of the oligopeptides.
Identification of prenylated flavonoids using fast‐atom bombardment mass spectrometry
Authors: Takanyama Mitsuo , Fukai Toshio , Ichikawa Koichi , Nomura Taro 
Published: May 2005

Abstract6‐ and 8‐prenylated flavanones were distinguishable from each other by means of their fast‐atom bombardment (FAB) spectral patterns, while the corresponding electron ionization spectral patterns were very similar to each other. It was suggested that 6‐ and 8‐prenylated flavonoids can, in general, be distinguished by means of FAB.
252Cf‐plasma desorption and cesium‐ion liquid secondary‐ion mass spectrometric analysis of recombinant proteins
Authors: Tsarbopoulos A. , Pramanik B. N. , Reichert P. , Siegel M. M. , Nagabhushan T. L. , Trota P. P. , Jardine I. 
Published: May 2005

AbstractThe keV Cs+ liquid secondary‐ion mass spectrometry (LSIMS) and 252Cf‐plasma desorption (PD) mass spectra of recombinant proteins in the 10–25 kDa mass range are compared. Both techniques showed comparable mass accuracy and sensitivity, and in the case of LSIMS, remarkably short analysis time. Analysis by the PD/nitrocellulose method demonstrated slightly higher sensitivity and relativity lower dependence on the salt and buffer content of the protein sample.
Solvent‐induced conformational changes of polypeptides probed by electrospray‐ionization mass spectrometry
Authors: Loo Joseph A. , Loo Rachel R. Ogorzalek , Udseth Harold R. , Edmonds Charles G. , Smith Richard D. 
Published: May 2005

AbstractElectrospray‐ionization (ESI) mss spectrometry is used to monitor higher order structural changes of polypeptide induced by alteration of the pH or organic solvent composition in the protein solution environment. A bimodal charge‐state disribution is observed in the ESI mass spectrometry of ubiquitin (relative molecualr mass 8565) in solution containing small amounts (<20%) of organic solvents. The distribution of peaks at high m/z (low‐charge state) is found to represent the protein in its native, globular state; the higher‐charge‐state distribution is characteristic for a more extended conformation. Addition of methanol denaturant in excess of 40% v/v is needed to eliminate the low‐charge‐state distribution completely. Lesser amounts of acetonitrile, acetone, or isopropanol (∼20%) are reqiored to denature the ubiquitin protein. Other proteins showing conformational efects in their ESI mass spectra are also illustrated. While the ESI spectra are related to solution phase structure, ESI‐tandem mass spectrometry of multiply charged molecular ions of different conformation is suggested as a probe of gas‐phase protein three‐dimensional structure.
Various techniques for the mass spectrometric analysis of valatile traces in environmental matrices using a direct‐coupled, paked column
Authors: Hille Jürgen 
Published: May 2005

AbstractVolatile trace impurities from enviornmental matrices were enriched on a packed column directly coupled to the vacuum system of a mass spectrometer. Traces in gaseous samples (air) were enriched without sample preparation. Traces from liquid samples (water) were separated on‐line by isothermal vacuum distillation, and from solid samples (soil) by vacuum desorption before adsorptive enrichment. Pressure reduction for sample introduction into the high vacuum of the mass spectrometer is realized by decreasing the pressure during enrichment and by cryo‐pumping, in which the packed column is immersed in liquid nitrogen (77 K). Besides the simple thermal desorption of enriched traces into the mass spectrometer, the column can be heated locally for carefully directed desorption of substance zones. Two alternative principles: ‘Frontal Desorption’ and ‘Purging’ are possible. Detection limits of ng/g were achieved for traces of chlorinated and aromatic hydrocarbons in air and water.
Location of unsaturated positions in phosphatidyl cholines by consecutive‐reaction monitoring
Authors: Bryant Duncan K. , Orlando Ron , Boyd R. K. 
Published: May 2005

AbstractConsecutive‐reaction monitoring (MS3) of negative ions has been shown to be useful in locating double bonds in the fatty acid ester groups of individual phosphatidyl cholines present in complex mixtures. This information is derived from charge‐remote fragmentations of carboxylate anions produced by collisional activation of the [MCH3]− precursor ions from phosphatidyl cholines. The added selectivety of this technique increases the sensitivity, relative to that of tandem mass spectrometry (MS2), such that only 3 pmol are needed to perform this analysis.
Analysis of polycyclic aromatic compounds by supercritical fluid charomatography/mass spectrometry using atmospheric‐pressure chemical ionization
Authors: Anacleto J. F. , Ramaley L. , Boyd R. K. , Pleasance S. , Quilliam M. A. , Sim P. G. , Benoit F. M. 
Published: May 2005

AbstractThe development of microbore packet‐column supercritical fluid chromatography/atmospheric pressure chemical ionization mass spectrometry (SFC/APCI‐MS) for the analysis of polycyclic aromatic compounds (PAC) is described. The SFC system was coupled to the mass spectrometer using an improved interface designed to accommodate commercially available fused silica restrictors. The atmospheric pressure chemical ionization characteristics of PAC are discussed and the use of chemical ionization reagents to modify the type of spectra obtained is described. With selected‐ion monitoring techniques the interface provided detection limits in the low picogram range for individual PAC standards. Using a photoionization detector for the off‐line optimization of chromatographic conditions, SFC/APCI‐MS was applied to the analysis of complex mixtures of PAC in coal tar and tar sand oil extracts. Tandem mass spectrometry was used to provide structural information.
Positively and negatively charged water cluster ions generated via liquid chromatography/thermospray mass spectrometry
Authors: Tinke A. P. , Heeremans C. E. M. , van der Hoeven R. A. M. , Niessen W. M. A. , van der Greef J. , Nibbering N. M. M. 
Published: May 2005

AbstractThe formation of singly protonated water clusters in the positive‐ion mode and singly deprotonated water clusters as well as singly negatively charged water clusters in the negative‐ion mode with a thermospray system running on pure water and in the discharge‐on mode is described. The influence of the potential at the repeller electrode opposite to the sampling cone recalls previous mechanistic discussions on the repeller influence. Application of these water cluster ions to tuning and calibration in the thermospray mode is proposed.
Conformational changes in proteins probed by hydrogen‐exchange electrospray‐ionization mass spectrometry
Authors: Katta Viswanatham , Chait Brian T. , Carr Steven 
Published: May 2005

AbstractHydrogen‐exchange electrospray‐ionization mass spectrometry is demonstrated to be an effective new method for probing conformational changes of proteins in solutions. The method is based on the mass spectrometric measurement of the extent of hydrogen/deuterium exchange that occurs in different protein conformers over defined periods of time. Results are presented in which hydrogen‐exchange electrospray‐ionization mass spectrometry is used to probe conformational changes in bovine ubiquitin induced by the addition of methanol to aqueous acidic solutions of the protein.
The resonantly enhanced of two‐photon ionization and electron ionization of trypyophan molecules in beams formed by laser evaporation of aqyeous cryogenic matrix
Authors: Elokhin V. A. , Krutchinsky A. N. , Ryabov S. F. , Cooks R. G. 
Published: May 2005

AbstractThe mass spectra resulting from election ionization and resonantly enhanced two‐ionization of amino acid trytophan molecules evaporated by the first harmonic frequency of a Nd‐YAG laser from an aqueous crygenic matrix were obtianed. The resonantly enhanced two‐photon spectra in the region of 0‐0 origin bands of tryptophan conformers was also measured.