bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of mass spectra obtained using 252Cf plasma‐desorption and electron‐avalanche‐desorption mass spectrometry
Authors: Zubarev R. A. , Bondrenko P. V. , Knysh A. N. , Rozynov B. V. 
Published: May 2005

AbstractDirect comparision of two ionization techniques, 252Cf plasma‐desorption and electron‐avalanche‐desorption, is given in various aspect. signification differences were observed in the low‐mass region, and in the spectra of volatile compounds and CsI samples, as well as in the fragmentation pattern of alanilnorleucine. On the other hand, a rather high degree of similarity was obtained in spectra of nitrocellulose and some cyclic depsipeptides, both in typical values of peak width and of the high‐mass background character. The conclusion is made, that electron‐avalanche desorption is a rather complex process involving various factors.
Mass spectral characteristics of okadaic acid and simple derivatives
Authors: Bencsath F. Aladar , Dickey Robert W. , Edmonds C. G. 
Published: May 2005

AbstractElectron ionization (EI), chemical ionization (CI) and fast‐atom bombardment (FAB) mass spectra of the marine toxin okadaic acid and its syntheticf methyi, pentafurobenzyl, and trimethylislyl ester and ether derivatives were generated. Several ionization conditions and‐processing methods were used to obtain positive‐ and negative‐ion conventional spectra and tandem (MS/MS) spectra. The EF and the positive‐ion CI spectra provided fragment ions characteristic of the structure, and the negative‐ion CI and FAB spectra provided molecular ions. The addition of alkali salts to the FAB matrix resulted in reduced fragmentation and the formation of intense alkali‐metal‐cationized molecules. Pentafluorbenzyle ester derivatives provided intense carboxylate ions under electron‐captute ionization. Analytically useful MS/MS spectra obtained by low‐energy collision‐induced decomposition of the carboxylate anion produced from the tetrasilylated pentafluorobenzylokadaate.
Structural characterization of isomeric didehydro amino acids using chemical ionization
Authors: Hamdan M. , Scaudola M. , Gaviraghi G. , Tarzia G. , Bedini A. L. , Spadoni G. , Curcuruto O. , Traldi P. 
Published: May 2005

AbstractThe positive‐ion mass spectra of a number of didehydro amino acids (DDAA) obtained by electron ionization (EI) and chemical ionization (CI) using different regent gases as well as the collision‐induced dissociation (CID) of mass‐selected odd‐electron ions and/or protonated molecules have been performed on a multiple quadrupole instrument. The positive‐ion EI/CI mass spectra presented display a number of differences which are expected from different isomeric structures. Furthermore, differences associated with the proton affinities of the reagent gases are clearly evident in the poisitive‐ion chemical ionization mass spectra as well as in some CID spectra of protonated molecules. This investigation demonstrates the suitability of chemical ionization for characterization of isomers of this important class of compounds and underlines the effect of the proton affinity of the reagent gas on the overall character of the positive‐ion chemical ionization spectra.
Metastable dissociation of multiphoton‐ionized xenon clusters
Authors: Yamada Yasuhiro , Takayanagi Toshiyuki , Furukawa Katsutoshi , Ohno Shin‐ichi 
Published: May 2005

AbstractXenon cluster ions (Xe) were produced by multiphoton ionization at 266 nm of neutral clusters resulting from supersonic expansion of xenon gas. Metastable dissociations Xe→Xe + Xe (where n=2−19) were observed by an angular reflectron time‐of‐flight mass spectrometer. Clusters of some particular sizes were found to be especially unstable, the highest dissociation rate obtained being for Xe. Furthermore, the dissociation rate tended to increase with increase of cluster size (n), in agreement with the evaporative ensemble model which has been developed by Klots.
Facile assignment of sequence ions of a peptide labelled with 18O at the carboxyl terminus
Authors: Takao Toshifumi , Hori Hideaki , Okamoto Kazutake , Harada Akira , Kamachi Mikiharu , Shimonishi Yasutsugu , Matsuo Takckiyo 
Published: May 2005

AbstractThe combination of collision‐induced dissociation (CID) and linked‐scan analysis was used for analysing the sequence ions from the precursor ion of a peptide, which had been labelled with 18O at its carboxyl terminus (C‐terminus) using 40 atom % H218O. The CID and linked‐scan mass spectrum of the labelled peptide gave two series of sequence‐ion signals: the one, originating from the C‐terminus of the labelled peptide, showed a doublet signal due to the part‐incorporation of 18O into the carboxyl group at the C‐terminus, while the other, originating from the amino terminus (N‐terminus), has the natural isotopic ion distribution. From the distribution of the isotopic ions in a single CID spectrum, the sequence ions containing the C‐terminus could be readily differentiated from those containing the N‐terminus, allowing the facile assignment of sequence ions to the amino‐acid sequence of peptide by CID and linked‐scan analysis. This method was successfully applied to determination of the amino‐acid sequence of the light‐chain of mouse anti‐porphyrin monoclonal antibody.
High mass‐resolution using a quadrupole ion‐trap mass spectrometer
Authors: Williams Jon D. , Cox Kathleen A. , Cooks R. Graham , Kaiser Raymond E. , Schwartz Jae C. , Gaskell S. J. 
Published: May 2005

AbstractModifications have been made to the quadrupole ion‐trap mass spectrometer (ITMS) to improve the resolution. An offset‐digital‐to‐analog converter/attenuator network is used to slow down the scan rate in the mass‐selective instability mode of operation with reasonance ejection. Attenuations of the scan rate by 200 to 700 times increase the resolution from 500 (with no attenuation) to 40 000 and 100 000 (full width at half maximum), respectively, for the [M + H]+ peak of substance p (m/z 1348). These improved resolutions are achieved in experiments which use resonance ejection to extend the mass‐to‐charge range.
The electron‐induced fragmentation of large ring cycloalkylamines. Intramolecular reactions between radical and immonium within distonic ions
Authors: Boukobbal B. , Lefèvre O. , Longevialle P. , Bouchoux G. 
Published: May 2005

AbstractThe unimolecular reactivity of molecular radical cations of secondary and tertiary cycloalkylamines in the gas phase is explained by the reactivity of the radical. Two competing reactions are crucial: the displacement of the radical along the hydrocarbon chanin by hydrogen transfers leading to a series of distonic ions, and the reaction of the radical with the immonium group, in each distonic ion, leading to cyclic structures. The resulting rearranged parent ions fragment subsequently by losing homelogous alkyl radicals.
Ethane elimination from C11H isomers. The effect of the position of formation of the neutral in relation to the ionic partner on the competitiveness of ion/neutral complex‐mediated eliminations
Authors: McAdoo David J. , Hudson Charles E. , Longevialle P. 
Published: May 2005

AbstractCompetition between loss of ethyl and ethane elimination through [C2H˙5 C9H] complexes is assessed as a function of the initial location of the two partners relative to each other. Ethyl loss is favored when that species originates from near the end of the chain, but ethane elimination increases steadily in relative importance as the site of cleavage is shifted towards the middle of the chain and is dominant when the ethyl is cleaved from the middle carbon. It is speculated that when the center‐of‐charge and the center‐of‐mass of the complex are substantially away from each other, individual rotation of the partners causes the ethyl group to spend relatively litle time near the hydrogen atoms it can abstract, favoring simple dissociation over ethane elimination. When the two centers approximately coincide, it is supposed that the ethyl group spends much of its time near abstractable hydrogen atoms, favoring ethane elimination.
On the formation of rotationally hot H by dissociation of CH dications
Authors: Krishnamurthi Vidhya , Mathur D. , Evans G. T. , Harris Frank 
Published: May 2005

AbstractDissociation of CH into CH ion pairs results in formation of H ions possessing a degree of rotational excitation which is high enough to enable formation of several rotational resonance states. These resonances give rise to unimolecular dissociation into H+ + H· fragments. Ion translational energy spectrometry has been applied to measure such dissociation spectra, and a number of rotational resonances are observed. Rotational resonances are not observed when H ions are generated from H2 precursors. Two models based upon ideas of impulsive energy release are investigated which attempt to correlate the centre‐of‐mass kinetic energy released upon dissociation of CH with the observation of the rotational resonances. There is good accord between the experimental results and the prediction of our models.
On the structure of [C9H6O]+· ions originating by electron impact induced decomposition of chalcone
Authors: Ardanaz C. E. , Kavka J. , Curcuruto O. , Traldi P. , Guidugli F. , Somogyi Arpad 
Published: May 2005

AbstractThe electron impact induced fragmentations of chalcone have been studied with the aid of high resolution measurements, using metastable decompositions by linked scans and mass‐analysed ion kinetic energy spectroscopy through collisional experiments by ion‐trap mass spectrometry and labellng by 13C deuterium. Based on the data obtained, two different mechanisms for the formation of m/z 130 ions have beenproposed.
Quantitative analysis of the molecular species of monosialogangliosides by continuous‐flow fast‐atom bombardment mass spectrometry
Authors: Chen S. , Pieraccini G. , Moneti G. 
Published: May 2005

AbstractNegative‐ion continuous‐flow fast‐atom bombardment mass spectroemtry was evaluated asa means for the quantitative analysis of N‐acetylneuraminyl‐galactosyl‐glucosyl ceramide (NeuAc‐G) and N‐acetylgalactosaminyl‐(N‐acetylneuraminyl)galactosyl‐glucosyl‐ceramide (NeuAc‐G). This study was carried out on a 7070‐EQ mass spectrometer (VG Analytical, Manchester, UK) using a home‐made continuous‐flow fast‐atom bombardment probe with a mixture of methanol +water+triethanolamine (70:27:3, v/v/v)as the mobile phase. Utilizing 100 ng of acetyl‐lysogalactosyl‐N‐acetylgalactosaminyl‐(N‐acetylneuraminyl)galactosyl‐glucosylceramide (acetyl‐lysoG) as an internal standard curves for NeuAc‐GM3 d18:1‐16 0, NeuAc‐G d18:1‐18:0 and Neuac‐G d18:1‐18:0 were found to be linear over the range 5‐250ng, with associated correlation coefficients of 0.990‐0.997. The lower limit of detection was found to be 2.5ng. Satisfactory results could also de obtained when the calibration curves were derived from the deprotonated molecular ions of a mixture of the NeuAc‐ and NeuAc‐G classes. Using this approach, quantitative determination of NeuAc‐G d18:1‐16:0 from rat adrenal gland was performed sing N‐acetylneuraminic acid assay as a test control. We found 278±36 ng of this species in 1 mg of tissue (three replicate experiments). The procedure represents a senstive method for the quantitation of mionosialogangliosides and its capability to give molecular species information.
Fuzzy classificational analysis of continuously scanned mass spectra of binary mixtures of positionally isomeric tetradecnols
Authors: Gu Yuan , Hirano Chisato , Horiike Michio 
Published: May 2005

AbstractBinary mixtures of positionally isomeric tetradecenols were by conventional combined gas chromatography/mass spectrometry without any chemical modification. Each spectrum in repetitive scanning was interpreted in terms of similarity of mass spectral patterns based on a fuzzy classification. This methodology is used for the rapid analysis of chromatographically unresolved isomers in a mixture.
Plotting mass‐peak profiles from selected‐ion recording data
Authors: Grange Andrew H. , Brumley William C. 
Published: May 2005

AbstractPlotting of mass peak profiles at high mass resolution for chromatographic peaks of low ion abundance is possible from single‐ion monitoring data due to the high sensitivity and low cycle time for single‐ion monitoring. The mass profiles provide accurate masses, document mass resolution at a mass as a chromatographic peak elutes and provide relative abundances for two ions at the same nominal mass. A personal computer is used to plot the mass peak profiles.
Fragmentation studies of peptides: The formation of Y ions
Authors: Kenny Peter T. M. , Nomoto Kyosuke , Orlando Ron 
Published: May 2005

AbstractThe mechanism for the formation of y ions in the collision‐induced dissociation (CID) spectra of protonated peptides produced by fast‐atom bombardment was investigated by tandem mass spectrometry and deuterium labelling studies. The results show that a hydrogen atom attached to nitrogen and not to carbon migrates during cleavage of the amide bond. A mechanism based on these results is presented.
Analysis of a mass‐analyzed ion kinetic energy profile. I. Analytical expression for a peak shape at a single kinetic energy release
Authors: Yeh In Chul , Kim Soo 
Published: May 2005

AbstractAn analytical expression has been derived for the mass‐analyzed ion kinetic energy spectral profile resulting from a single kinetic energy release in a metastable ion decopmposition. Effects of the Z and Y discriminations and the site of dissociation on the peak‐shape have been accounted for. In addition an analytical peak‐shape function has been derived for a dissociation occurring in and near the collision cell floated at high voltage. Excellent agreement between the present results and the peak shapes obtained by regorous ion‐optical trajectory calculations support the validity of the present method. More importantly, the present method has the advantage of a tremendous reduction in computing time.
The extent of internal excitation of the protonated molecules of some liquid martices bombarded by keV Cs+ ion beams
Authors: Hamdan M. 
Published: May 2005

AbstractIn an attempt to probe the extent of internal excitation of protonated ions formed by positive fast‐ion bombardment, the protonated molecules of four commonly used liquid matrices are formed by means of the above technique and their respective mass‐selected collision‐induced dissociation (CID) spectra are investigated within the collision energy range, 5‐200 eV (in the laboratory frame of references). These measurements are also repeated for the same four precursor ions formed by means of positive‐ion chemical ionization in two different reagent gases, NH3 and CH4. The observed dissociation channels and the relative peak heights associated with them imply that the internal excitation of protonated molecules formed by fast‐ion bombardment is much higher than that associated with the protonated ions formed in positive‐ion ammonia CI(NH3‐CI+). On the other hand, close resemblance between the CID spectra of ions formed by the first technique, by CH4‐CI+ and by electron ionization is clearly evident.
A compact time‐of‐flight mass spectrometer for the structural analysis of biological molecules using laser desorption
Authors: Cornish Timothy , Cotter Robert J. 
Published: May 2005

AbstractA compact laser‐desorption time‐of‐flight mass spectrometer using a 600 ps nitrogen laser and 1 Gsample/s transient recorder is described. The instrument incorporates two electrically‐isolatable, reflecting flight tubes designed for subsequent configuration of the mass spectrometer as a tandem instrument. In this first report, we compare mass resolution in the laser‐desorption mass spectra of an organic dye, sinapinic and caffeic acid matrices, and sevesral small peptides. For directly desorbed ions, peak widths are generally of the order of 11 to 13 ns, so that mass sesolutiojn increases with increasing mass. For peptide ions in the range of 500 to 1000 u, formed by matrix‐assisted desorption, peak widths range from 9.5 to 17.6 ns and increase with mass. However, better than unit mass resolution (1600 to 2400) is maintained throughout this range. Mass measurement accuracy is better than 0.1 u using a single calibration peak and a prompt start trigger pulse. Prospects for extending mass range and resolution are discussed.
The components of the venom of a spider Scodra griseipes. 1. Analysis of low molecular weight products using gas chromatography/mass spectrometry
Authors: Lange C. , Paris C. , Clerier M.‐L. 
Published: May 2005

AbstractLow molecular weight venom constituents of the spider Scodra griseipes have been derivatized using bis(trimethylsilyl)‐trifluoracetamide and pentafluoropropionic anhydride. Examinatio of these derivatives by coupled gas chromatogrtaphy/mass spectrometry using electron ionization or ammonia‐ or isobutane‐chemical ionization allows their structural identification. Comparisons have also made with retention time and mass spectra of the pure compounds. Four acids: phosphoric, lactic, citric, Y‐aminobutyric (neurotransmitter0 and four basic biogenic amines: putrescine, cadaverine, spermidine and spermine have been found.
Improvements in ion‐trap chemical‐ionization performance
Authors: Cairns Thomas , Chiu Kin S. , Siegmund Emil , Weber Michael 
Published: May 2005

AbstractIon‐trap chemical‐ionization performance has been imporved by application of a modified scan function for the rejection of the undesired electron‐ionization‐like (EI‐like) ions formed at the beginning of the reaction ionization period. The net effect of this software modification to the automatic reaction control is to produce chemical ionization (CI) spectra that are no longer adulterated with conventration‐dependent EI‐like ions. Under such improved conditions, CI spectra from an ion trap can now be dirctly compared with CI spectra produced on conventional quardrupole and magnet‐scanning instruments.
Differences in the conformational state of a zinc‐finger DNA‐binding protein domain occupied by zinc and copper revealed by electrospray ionization mass spectrometry
Authors: Huthens T. William , Allen Mark H. , Lewis I. 
Published: May 2005

AbstractTransition metal ions are important in biological regulation partly because they can bind to and stabilize protein surface domain structures in specific conformations that are involved in key molecular recognition events. There are twso C2‐C2 type zinc‐finger sequences within the highly conserved DNA‐binding domain of the estrogen receptor protein (ERDBD). Electrospray ionization (ESI) mass spectrometry has been used to demonstrate that the metal‐binding sites within the 71‐residue ERDBD can bind either Zn (up to 2) or Cu (up to 4). Evidence for the induction and /or stabilization of a different conformational state with bound Cu is revealed by a characteristic shift in the ESI charge envelope. The 10+ charge state is most abundant for the fully reduced ERDBD apopeptide and the ERDBD‐Zn holopeptide (bound Zn does not alter the charge envelope. In contrast, the 8+ charge state is typically the optimjum charge state observed for the ERDBD‐Cu holopeptide; indeed, the entire charge envelope is frame‐shifted to lower charge states with bound Cu. Interpretation of the altered charge states is simplified because (i) a single type of metal‐binding ligand (sulfur) is involved in the case of both Zn and Cu binding, and (ii) the two different metal cations are both divaalent. Thus, it is likely that the dissimilar charge envelopes represent different peptide conformers, each of which is stabilized by a different type of bound metal ion. The covalent bridging or adjacent Cys residues within a peptide is similar to the formation of intramolecular disulfide bonds, a process that we also found to decrease both the optimum and mumber of ERDBD charge states observed by ESI. The existence of distinct conformational states for the ERDBD‐Zn and ERDBD‐Cu is consistent with the differences in apparent coordinate covalent geometry and stoichiometry for the two bound metal ions. Our findings are aslo consistent with prevous investigations of globular proteins that reveal an increase both in the number of charge states and a shift in the optimum charge state when structure is disrupted by reduction of intramolecular disulfide bonds.
Atmospheric‐pressure ionization interface for a bench‐top quadrupole ion trap
Authors: Mordehai Alex V. , Hopfgartner Gerard , Huggins Tom G. , Henton Jack. D. 
Published: May 2005

AbstractA novel interface is described that effects the sampling and mass analysis of ions formed at atmospheric pressure into a Saturn II bench‐top quadrupole ion‐trap mass spectrometer. The standard high‐vacuum pumping system of the system is unchanged, bit a 960L/min rotary pump is incorporated to pump the first vacuum stage of the atmospheric‐pressure ion sampling interface. An ‘Electric skimmer’ ion focusing region in the first vacuum turbomolecular pump of the Sasturn II maintains high vaccuum at 4×10−4 Torr in the analyzer region while helium damping gas is introduced. By vaarying the potential difference between selected lenses in the first vacuum region the ‘declustering’ energy may be varied to decluster effectively ion/molecule dissociation mass spectra. The on‐line analysis of quaternary ammonium drugs by liquid chromatography of 5 ng and 150 pg, respectively.
Charge‐state distributuion and electric‐discharge suppression in negative‐ion electrospray mass spectrometry using/chlorinated solvents
Authors: Cole Richard B. , Harrata A. Kamel 
Published: May 2005

AbstractSolvent effects in electrospray mass spectrometry performed in the negaative‐ion mode have been examined, for a series of low‐nucleophilicity chlorinated solvents. The charge‐state distribution of a test analyte was observed to change radically with the nature of the solvent. Formation of anions of higher charge stae was favored in solvents of higher polarity. The shift in the charge‐state distribution has been largely attributed to improved solvation of chaarge sites by increasingly polar solvents. Evidence suggests that valence electrons of the chlorine atoms do not contribute significantly to solvation of acidic protons. Highly chlorinated solvents in teh electrospray bath gas serve to suppress electrical (corona) discharge phenomena. The latter effect was magnified with increasing percent weight of chlorine in the solvent. The observed discharge suppression has been attributed to electron‐capture preocesses. This solvent effect was muted when a highly efficient electron seavenger(i. e., SF6) comprised the elctrospray high gas.
Determination of 15N enrichment of taurine in cat urine by high resolution fast‐atom bombardment mass spectrometry
Authors: Stämpfli Andress A. , Ballèvre Olivier , Fay Laurent B. 
Published: May 2005

AbstractA method is described for measuring the stable isotopic enrichment of taurine in cat urine samples by high resolution fast‐arom bombardment mass spectrometry, after 15N labelled taurine was given to cats for the purpose of investigation taurine metabolism. The 15N enrichemnt of taurine was measurd after hydrolysis and purification of taurine by anion/cation exchange chromatography. The isotopic ratio of taurine was detemined by measuring the [M+H]+ ion peaks in the spectra of the unlabelled and labelled compounds under multiple ion scan conditions. The overall standard deviation of the measurement is beter than 4%. This method requires no derivation and uses only 500 μL of urine samples.
Data transfer from a DEC PDP‐11 based mass spectrometry data station to an MS‐DOS personal computer
Authors: Raffaelli Andrea , Bruins Andries P. 
Published: May 2005

AbstractThis paper describes a simple procedure for obtaining better quality graphic output for mass spectrometry data from data systems equipped with poor quality printing devices. The procedure uses KERMIT, a low cost public domain software, to transfer ASCII tables to a MS‐DOS personal computer where they can be elaborated and customized using one of the powerful graphic tools available. The final result can be sent to a high quality laser printer or pen plotter or incorporated in a document generated with a word processor.