bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of the oxidation products of paralytic shellfish poisoning toxins by liquid chromatography/mass spectrometry
Authors: Quilliam Michael A. , Janeček Mojmir , Lawrence James F. 
Published: May 2005

AbstractPeriodate oxidation of the toxins responsible for paralytic shellfish poisoning (PSP) yields fluorescent products that are useful for trace analysis by reversed‐phase liquid chromatography. Some toxins are oxidized to the same product, while others are transformed to a mixture of products; in ail cases, the products are too unstable to be isolated preparatively. A mobile phase containing heptafluorobutyric acid as an ion‐pair agent was developed to improve compatibility with liquid chromatography/mass spectrometry (LC/MS) analysis. Several LC/MS techniques were investigated: chemical ionization with the moving belt interface, atmospheric‐pressure chemical ionization, thermospray, continuous‐flow fast‐atom bombardment, and ion‐spray. Only LC/ion‐spray MS was able to provide spectra of the oxidized products. The products were characterized as purines resulting from: (a) breakage of the C4–C12 bond and aromatization of the remaining rings (loss of 4 hydrogens); (b) partial elimination of a carbamoyl or N‐sulfocarbamoyl side‐chain (this is promoted by the presence of an N‐1‐hydroxy group); and (c) partial hydrolysis of an N‐suifocarbamoyl side‐chain to a carbamoyl group.
Analysis of the squalestatins by on‐line packed capillary liquid chromatography/dynamic liquid secondary‐ion/mass spectrometry
Authors: Lane S. J. , Brinded K. A. , Taylor N. L. 
Published: May 2005

AbstractA mixture of four squalestatins was separated and characterized by gradient‐packed capillary liquid chroma‐tography combined with dynamic liquid secondary‐ion mass spectrometry (LSIMS). Thioglycerol/glycerol matrix was added post‐column. Negative‐ion LSIMS was found to afford spectra typified by strong molecular ions with structurally informative fragments. The new method showed improvements in sensitivity and specificity for this class of compound when compared to existing thermospray methods.
Enhanced efficiency of surface‐induced dissociation of slow molecular ions at grazing incidence
Authors: Schmidt Lothar , Fritsch Hans‐Walter , Jungcfas Hartmut 
Published: May 2005

AbstractIons of m/z > 104 colliding with a solid surface at kinetic energies of 10–30 keV induce sputtering of secondary ions rather than emission of secondary electrons. Impact energies of 1 keV or lower lead to surface‐induced dissociation (SID) resulting in the release of specific fragment ions and this could also be employed for the detection of large ions in mass spectrometry. The present study using plasma‐desorption time‐of‐flight mass spectrometry gives evidence that the secondary ion yield of tlte SID‐process is maximal at grazing incidence. For impact energies ranging from 0,66 to 1.4 keV the SID efficiency is nearly constant and can be higher for large than for small organic ions colliding with a flat surface at grazing incidence angles.
The mass spectrometry service centre at Swansea: A small jewel in the crown of the science and engineering research council
Authors: Ballantine J. A. 
Published: May 2005

AbstractThe National Centre, set up by the Science and Engineering Reasearch Council in 1985, currently services the specialist mass spectrometry requirements of over 140 chemistry research teams, covering most of the British universities and carrying out about 9500 analyses each year, using mainly soft‐ionization techniques. Its work has featured in 1276 publilcatons during the past three years and the Centre has become invaluable to the progress of many research teams in Britain.
Contributions of fast‐atom bombardment mass spectrometry to studies of cyclic nucleotide biochemistry
Authors: Newton Russell P. 
Published: May 2005

AbstractCyclic nucleotides are biochemical second messengers which mediate the actions of many hormones and neurotransmitters. Fast‐atom bombardment (FAB) mass spectrometry and mass‐analysed ion kinetic energy (MIKE) spectra have provided a means of unambiguous identification of these compounds, and in addition to identifying endogenous putative cyclic nueleotides and their synthetic analogues FAB/MIKE analysis has now been applied to good effect to both qualitative and quantitative studies of cyclic nuclcotide‐related enzymes. Here the application of this mass spectrometric technique to cyclic nucleotides is described and its impact upon this field reviewed.
A radial‐field mass spectrometer with ‘T‐2’ deflection voltage
Authors: Akram A. G. , Miles H. T. 
Published: May 2005

AbstractMass analysis of ions emanating from a laser‐produced plasma requires some means of overcoming their wide energy spread, such as, for example, through the use of an ion reflector in time‐of‐flight spectrometers. An alternative approach to this problem is to allow the ions to move freely from the plasma into a spectrometer in which a radial deflection field varies in time in such a way that the deflection trajectory of an ion is independent of its energy. This paper describes the theory of such a spectrometer and investigates the focusing properties of the system. It is found that the required time‐varying field does not destroy the focusing features known for a radial field system except that under these new conditions first‐order focusing occurs at a turning angle of 144°, which contrasts with a focusing angle of 127° for a radial‐field spectrometer operating with a constant deflection field. The ion trajectories for the time‐varying field have been sutdied using numerical methods and results from these are presented. An approximate theory is also included which is in excellent agreement with the numerical computations and which yields simple results for use in spectrometer design.
State compositional analysis of diatomic cation beams using charge‐inversion spectrometry
Authors: Reid C. J. 
Published: May 2005

AbstractThe utility of charge‐inversion Spectrometry in the state analysis of diatomic cation beams is demonstrated by a brief summary and by reference to novel work on beams of NO+, SH+, CS+ and CI. A previously unknown state, of 3.5 eV relative energy and presumably of 4Σ+ symmetry was observed to be populated in a beam of CS+ ions formed from CS2. Evidence for the longevity ( > 10−5s) of the Ã2II state of CS+ and the b̃3II state of NO+ is also presented.
Double‐charge‐transfer spectroscopy using a modified Finnigan 8230 spectrometer
Authors: Andrews S. R. , Harris F. M. 
Published: May 2005

AbstractA Finnigan 8230 mass spectrometer has been converted to a translational‐energy‐loss spectrometer suitable for double‐charge‐transfer (DCT) spectroscopy. Its performance was investigated by obtaining DCT spectra when 3keV OH+ projectile ions interacted with xenon atoms and ethene molecules. Well‐separated peaks were obtained which correspond to the populating of dicationic electronic states differing in energy by about 1 eV.
Simultaneous detection of ions and neutrals produced by matrix‐assisted laser desorption
Authors: Mowry Curtis D. , Johnston Murray V. 
Published: May 2005

AbstractIonic and neutral products of matrix‐assisted laser desorption were simultaneously detected in a time‐of‐flight mass spectrometer. The neutrals were photoionized with coherent vacuum ultraviolet radiation. Mass spectra were obtained for primary and secondary alkyl amines in various absorbing matrices. Based upon relative signal intensities of directly formed analyte ions and photoionized analyte neutrals, the ratio of neutrals‐to‐ions ejected was found to be of the order of 10000 or greater with desorption irradiances near the threshold for ion formation. The ratio decreased with increasing irradiance of the desorption laser beam. This dependence is consistent with a collisional mechanism tor analyte‐ion formation during the desorption event that is initiated by photoionization of the matrix. Matrices which gave large signal intensities of directly formed analyte ions also gave large signal intensities of photoionized analyte neutrals. Conversely, matrices which gave small signal intensities of directly formed arelyte ions also gave small signal intensities of photoionized analyte neutrals. These results suggest that the efficiency of analyte vaporization by matrix‐assisted laser desorption is an intrinsic property of the matrix‐analyte pair, independent of the ion‐formation process.
The potential of pyrolysis—(methylation)/gas chromatography/mass spectrometry in the analysis of wine polyphenolics
Authors: Galletti Guido C. , Antonelli Andrea 
Published: May 2005

AbstractThe phenolic compounds of a red Italian wine were separated by column chromatography into three fractions: (a) monomers, (b) red polymers and (c) yellow and brown polymers (tannins). Polymers were subjected to pyrolysis/gas chromatography/mass spectrometry (PY/GC/MS) using a heated‐filament pyrolyzer coupled to a capillary gas chromatograph and an ion‐trap‐detector mass spectrometer. Samples were pyrolysed as such or mixed with an aqueous solution of tetramethylammonium hydroxide in order to perform a simultaneous pyrolysis‐methylation (SPM). Pyrograms showing diagnostic markers for flavonoids and phenolic acids are reported. Advantages and limitations of both PY/GC/MS and SPM/GC/MS are discussed.
Optimization of a commercial liquid chromatography/mass spectrometry interface by statistical experimental design
Authors: Huang S. K. , Glancy S. B. , Stansbury W. F. 
Published: May 2005

AbstractThe efficiency of delivering 4‐methoxy phenyl acetic acid particle beam emerging from a commercial liquid chromatography/mass spectrometry interface into the ion source of the mass spectrometer was optimized using response surface modeling (RSM) of the statistical experimental design. It was found that the temperature and pressure of the nebulizer, and the temperature of the desolvation chamber are the major factors for the optimization.
Fast‐atom bombardment mass spectrometric analysis of cyclic nucleotide and nucleotide triphosphate analogues used in studies of cyclic nucleotide‐related enzymes
Authors: Langridge James I. , Evans Andrea M. , Walton Terence J. , Harris Frank M. , Brenton A. Gareth , Newton Russell P. 
Published: May 2005

AbstractTwo isomers of adenosine 3′,5′‐cyclic monophosphate, which show agonist and antagonist activity with cyclic AMP‐dependent protein kinase, were found to yield essentially identical positive‐ion fast‐atom bombardment (FAB) mass spectra, but S1 and S2 fragments of differing relative intensities in their collision‐induced dissociations, studied using mass‐analysed ion kinetic energy (CID/MIKE) spectra. Halogen‐substituted cyclic nucleotides, used in differentiating between protein kinase cyclic nucleotide binding sites, produced FAB mass spectra and CID/MIKE spectra with fragmentations generally analogous to those of the parent cyclic nucleotides; the bromo‐derivatives showed a greater propensity for dehalogenation than the chloro‐derivatives. The adenosine triphosphate analogues, adenylyl‐(β,γ‐methylene)‐diphosphate and adenylyl‐imidodiphosphate, alternative substrates for adenylyl cyclase, showed similar fragmentations with the methylene and imido groups blocking cleavage between the β and γ phosphate groups. The fragmentations observed are discussed in the context of the use of these compounds in the assay of protein kinase and adenylyl cyclase activity by quantitative mass spectrometry.
Collision‐induced dissociation and charge‐reversal processes of isomeric C6H4X− (X = F, Cl and Br) anions
Authors: Tomperi Päivi H. , Matimba Henri E. K , Ingemann Steen , Nibbering Nico M. M. 
Published: May 2005

AbstractThe NH ion reacts with fluoro‐ and chlorobenzene in the cell of a Fourier‐transform ion cyclotron resonance instrument only by proton abstraction, whereas the reaction with bromobenzene also yields Br− ions. The deprotonation of these halogen‐substituted benzenes occurs the 2‐, 3‐ or 4‐positions as revealed by deuterium labelling in combination with high kinetic energy (8keV) collision‐induced dissociation (CID) experiments performed with a double‐focusing quadrupole hybrid mass spectrometer. The 2‐fluoro‐ and 3‐ fluorophenyl anions eliminate HF following collision with an oxygen molecule. By contrast, the collisions between 4‐fluorophenyl anions and O2 do not yield detectable amounts of negatively charged fragment ions owing to the exclusive occurrence of electrom detachment. Electron detachment is also the only process observed in the 8 keV CID experiments with chlorophenyl anions and 3‐ and 4‐bromophenyl anions, whereas the ion formed by proton abstraction from the 2‐position in bromobenzene dissociates to Br− and 1,2‐dehydrobenzene. The 8 keV collision‐induced charge‐reversal spectra of the anions formed by proton abstraction from the 2‐, 3‐ or 4‐positions in a given halogen‐substituted benzene are virtually identical, indicating that this method does not provide insight into the position of the charge with respect to the halogen atom in the substituted phenyl anions.
Verification of the position of the phosphate group in some synthetic phosphopeptides by fast‐atom bombardment and tandem mass spectrometry
Authors: Nijenhuis A. A. , Fokkens R. H. , Nibbering N. M. M. , van Oijen A. H. , de Bont H. B. A. , Liskamp R. M. J. , van Boom J. H. 
Published: May 2005

AbstractSome synthetically obtained linear and cyclic phosphopeptides of low molecular weight have been studied by fast‐atom bombardment and tandem mass spectrometry to verify the position of the phosphate group in these compounds. Based upon the occurrence/non‐occurrence of loss of phosphoric acid from low abundance fragment ions induced by low‐ and high‐energy collisions with target gases, it is shown that the position of the phosphate group in the phosphopeptides studied can be determined unequivocally.
Double‐electron transfer from Xe to Xe4+ at low energies as observed in the trap of a fourier‐transform ion cyclotron resonance mass spectrometer
Authors: von Köding Holger , Pinkse Frans A. , Nibbering Nico M. M. 
Published: May 2005

AbstractMultiply charged Xen+ ions with n⩽5 were generated by electron impact on xenon gas in the external ion source of a Fourier‐transform ion cyclotron resonance (FT‐ICR) mass spectrometer. These ions were transferred to and trapped in the low pressure FT‐ICR cell. Subsequently, xenon ions with a particular mass and charge state were selected by ejection of all other unwanted ions from the FT‐ICR cell and allowed to react with neutral xenon atoms. It was found that, in the interactions between Xe4+ ions and neutral xenon atoms, not only does a single electron transfer take place, but also a double electron transfer.
Mass spectrometry of some C6F13‐compounds and their C6H13‐analogs
Authors: Napoli M. , Krotz L. , Scipioni A. , Seraglia R. , Traldi P. 
Published: May 2005

AbstractThe 70 eV electron ionization mass spectrometric behaviour of some C6F13‐compounds has been studied in detail by means of mass‐analyzed ion kinetic energy spectroscopy and compared with that of the C6H13‐analogs. As a general trend, the incorporation of fluorine leads to a strengthening of the alkyl chain; in fact the extensive primary fragmentation processes related to the chain cleavages observed for hydrocarbon derivatives are strongly suppressed in the case of the corresponding fluorocarbons. Moreover, the interaction of fluorine with functional groups leads to unexpected decomposition processes. The CH2CF2 bond, often considered in condensed‐phase chemistry as a weak point in the molecule, never undergoes fragmentation.
Enthalpies of formation of the negative ions MnO, MnO and MnO as determined by the ion/molecule equilibrium method
Authors: Rudnyi E. B. , Kaibicheva E. A. , Sidorov L. N. 
Published: May 2005

AbstractAdmixture of potassium chromate to manganese oxide has allowed us to generate measurable concentrations of the negative ions MnO, MnO, and MnO in the vapours over manganese oxide at 1300–1500 K. Equilibrium constants with the participation of these ions have been measured and the enthalpies of formation {ΔfH(MnO, 0 K) = (−266±13)kJmol−1, δfH,(MnO, 0 K) = (−538±14) kJmol−1, δfH(MnO, 0 K) = (−669±17)kJ mol−1}, dissociation energies and the electron affinity (EA) of MnO2 {EA = 292kJ mol−1} have been estimated. The use of manganese‐containing negative ions to measure the activity of manganese oxides is discussed.
Radical molecular anions formed from organic molecules under negative‐ion fast‐atom bombardment conditions: An unexpected finding during studies on the metabolism of bis(2‐ethylhexyl) phthalate
Authors: Egestad Börje , Sjöberg Per 
Published: May 2005

AbstractUrinary metabolites of bis(2‐ethylhexyl) phthalate were studied using fast‐atom bombardment mass spectrometry (FAB‐MS). It was found that the ß‐glucosides of mono(2‐ethyl‐5‐hydroxyhexyl) phthalate and mono(2‐ethyl‐5‐oxohexyl) phthalate gave radical molecular unions, M −·, under negative‐ion FAB conditions. This was also shown to occur for the methyl ester of mono(2‐ethylhexyl) phthalate ß‐glucuronide, an artefact formed during the work‐up procedure.
A new method of trapping ions produced by matrix‐assisted laser desorption lonization in a quadrupole ion trap
Authors: Doroshenko Vladimir M. , Cotter Robert J. 
Published: May 2005

AbstractA novel method for trapping ions produced by matrix‐assisted laser desorption ionization (MALDI) using controlled gating of the trapping field is suggested. Because it does not use collisions with helium atoms for reducing ion kinetic energy, trapping can be accomplished at low pressures of the buffet gas. The method has been implemented on an ion‐trap detector, modified for MALDI experiments inside an ion trap with axial introduction of the sample probe. High mass resolution (1 part in 12 000) is reported.
Accurate mass determination of a high molecular weight protein using electrospray lonization with a magnetic sector instrument
Authors: Dobberstein P. , Schroeder E. 
Published: May 2005

AbstractAccurate mass determination on the 13+ ion of myoglobin, MW 16951, has been performed with a magnetic sector mass spectrometer equipped with a newly designed electrospray ion source. At a mass resolution of 20000 a mass deviation of 1 ppm from the expected value has been achieved.
Application of electrospray ionization mass spectrometry with maximum‐entropy analysis to allelic ‘fingerprinting’ of major urinary proteins
Authors: Evershed Richard P. , Robertson Duncan H. L. , Beynon Robert J. , Green Brian N. 
Published: May 2005

AbstractMixtures of a specific group of proteins, the major urinary proteins (MUPs), believed to have a role in odorant binding, have been analysed by electrospray ionization mass spectrometry. The data obtained from conventional transformed electrospray data confirm that the molecular weights of the protein mixtures, deduced from published sequences, lie in the molecular weight range 18600 to 19 000 Da. Application of maximum‐entropy analysis to the raw electrospray data has confirmed a heterogeneity in MUP composition, consistent with allelic similarities (and differences) between the different mouse strains. This work demonstrates the use of maximum entropy in the assessment of protein content and in the subsequent resolution enhancement of naturally occurring protein mixtures containing components of closely similar molecular mass.
Surface chemical changes of mixed‐oxide films in Cl2 anodic production
Authors: Daolio Sergio , Facchin Bruno , Pagura Cesare , Battisti Achille De , Barbieri Andrea 
Published: May 2005

AbstractThe recent development of specific and sensitive surface techniques has prompted new studies of electrode properties, in particular of their catalytic activity. Many papers have reported the use of X‐ray photoelectron spectrometry, Rutherford backscattering spectrometry, secondary ion mass spectrometry etc. in the analysis of mixed‐oxide films, and interesting results concerning electrochromic and catalytic properties have been shown. The influence of the method of preparation has also been confirmed, together with the important role of microstructural composition. In previous studies, our group performed composition analyses and depth profiles of RuO2/TiO2 and IrO2/TiO2 mixed‐oxide coatings by secondary ion mass spectrometry (SIMS). Many positive‐and negative‐ion species are of particular interest in characterizing electrodes synthesized by different methods. This paper presents the results obtained by SIMS analysis of IrO2/RuO2/TiO2 films before and after their use in CI2 anodic production. Mass spectra obtained under different experimental conditions are reported and the aspects related to surface compositon modifications induced by Cl2 evolution on electrode films are discussed.
Mass spectral fragmentation patterns of some thieno[3,2‐b]‐ and thieno[2,3‐b]‐thiophene‐2‐carbonylchlorides and ‐2‐carbonylanilides
Authors: Karminski‐Zamola Grace , Cvetko Magda , Švob Vladimir 
Published: May 2005

AbstractThe electron impact mass spectra of some thieno[3,2‐b]‐ and thieno[2,3‐b]‐thiophene‐2‐carbonylchlorides and ‐2‐carbonylanilides are discussed. Dominant peaks in the anilides are formed by cleavage of the C‐N amide bond and these ions fragment further by cleavage of CO. The fragment ion C3HS⌝+˙ m/z 69 is characteristic of carbonylchlorides and also carbonylanilides.
Correlation between the intensity of fragment ions in fast‐atom bombardment and the NMR chemical shift of hydrogen‐bonded hydroxyl protons of 6‐prenylfavonoids
Authors: Fukai Toshio , Nomura Taro 
Published: May 2005

AbstractCorrelation between the relative abundances of fragment ions from fast‐atom bombardment mass spectrometry and the chemical shifts of OH‐5 signals in 1H NMR 6‐prenylated flavonoids is discussed. The correlation may reflect the interaction between 6‐prenylated flavonoid and matrix.
Effects of target identity and collision energy on the fragmentation of some mass‐selected protonated neuropeptides
Authors: Curcuruto Ornella , Hamdan Mahmoud 
Published: May 2005

AbstractA number of protonated neuropetides formed by 10 keV Cs+ ion bombardment are mass selected and their collision‐induced dissociations (CID) with helium, argon, xenon and isobutane are monitored using a collision energy of 200 eV. Data obtained by fixing the collision gas and using translational energies in the range 50–250 eV are also presented. The present data imply that optimzation of the CID spectra presented can be achieved through a judicious choice of both the target gas and the translational energy of the mass‐selected ion. The combined effect of the two experimental parameters on the relative abundances of the major sequence ions and on the loss of side‐chain moieties is discussed.
CF bond cleavage in collisionally activated dissociation of polyfluorinated molecular ions: Empirical structure‐upward‐shift correlation
Authors: Lee Young Jin , Kim Myung Soo 
Published: May 2005

AbstractIn an effort to understand the apparent upward shift in the translational energy of C6F· generated by collisionally activated dissociation (CAD) of the hexafiuorobenzene molecular ion, CADs of various molecular ions have been investigated. An interesting empirical correlation has emerged: namely, the loss of fluorine atoms directly attached to aromatic systems has displayed the upward shift. On the other hand, the F‐loss from polyfluorinated aliphatic molecular ions, either saturated or unsaturated, has shown the usual downward shift.
Peak profiles of ions originating from solid surfaces in time‐of‐flight mass spectrometers incorporating reflectrons
Authors: Loanoviciu D. , Cuna C. , Ardelean P. 
Published: May 2005

AbstractPeak shapes were simulated in time‐of‐Hight mass spectrometers incorporating reflectrons, assuming short‐duration, constant ion‐production rates from plane surfaces. Calculations were performed for various initial velocity distributions: both Maxwell‐Boltzmann and exponential distributions for laser desorption, Gries distribution for secondary ions and Riggi‐Furstenau distribution for plasma‐desorption generated ions. The influence of an exponential decrease of the ion production rate on the peak shape was also illustrated in some cases.