bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation and decay of doubly charged ions from polycyclic aromatic hydrocarbons and related compounds
Authors: Hagan D. A. , Eland J. H. D. 
Published: May 2005

AbstractCoincidence techniques have been used to investigate double photoionization and subsequent decay of a series of polycyclic aromatic hydrocarbons (PAHs) from benzene to perylene. At fixed photon energy (40.8eV) the total yield of double ionization relative to single photoionization for both PAHs and for aliphatic compounds increases asthe same function of the excess energy above the double ionization energy. The ratio of double to single ionization for a given compound at different photon energies varies linearly with the excess energy. The fraction of dissociative double photoionization falls with increasing size in the PAH series; the ejection of characteristic neutral species (H˙, H2 and C2H2) is the main dissociation pathway in the larger PAHs while charge separation is important for smaller species. Partial hydrogenation or aliphatic substitution results in decreasing stability of the doubly charged ions and increasing dissociation.
Fast‐atom bombardment mass spectrometry of oligomeric dicyanobis(polypyridine) ruthenium (II) complexes
Authors: Bignozzi C. A. , Bortolini O. , Traldi P. 
Published: May 2005

AbstractThe positive‐ion fast‐atom bombardment (FAB) mass spectra of the biniclear [CNRu(L2)CNRu(L'2)CN]+ and trinuclear [CNRu(L2)CNRu(L2CNRu(L2)CN]2+ complexes (L=2,2′‐bipyridine; L' = 2,2′‐bipyridine or 1,10‐phenanthroline) have been investigated and compared with those of the mononuclear NCRu(L'2CN species. The FAB fragmentation patterns of the mononuclear species are interpreted by a combination of simple losses of neutral polypyridine ligands andHCN molecules and provide useful information for the understanding of the gas‐phase decomposition of the oligimeric species.
Measurement of gas‐phase binding energies of crown ethers with metal ions by Fourier‐transform ion cyclotron resonance mass spectrometry
Authors: Katritzky Alan R. , Malhotra N. , Ramanathan R. , Kemerait R. C. , Zimmerman Jaffrey A. , Eyler John R. 
Published: May 2005

AbstractComplexes of the type [crown+M]+ were observed following laser desorption ionization of 18‐crown‐6 molecules ‘doped’ with K+, Cs+, and Ba+. Laser desorption ionization of 15‐crown‐5 and 12‐crown‐4 ‘doped’ with the same metals gave [(crown)]2+[M]+ type sandwich complexes. Binding energies of crown ethers with different metal ions in all such complexes have been estimated from appearance energies obtained in the collisionally‐activated dissociation of the corresponding laster desorbed complexes.
Dissociation of positively‐charged apliphatic epoxides. III. [C4H8O]+˙ eposides and α, β unsaturated ethers
Authors: Berruyer‐Penaud Florence , Bouchoux Guy , Tortajada Jeanine 
Published: May 2005

AbstractUnimolecular dissociation of the molecular cations of 1,2‐expoxybutane (1), 1‐methoxypropene (2), 2,3‐epoxybutane (3), ethyl‐vinyl ether (4), 1,2‐epoxy‐2‐methylpropene (5), and 2‐methoxypropene (6)have been investigated. Different behaviour of pairs of [C4H8O]+˙ isomers (1+˙/2+˙), (3+˙/4+˙) and (5+˙/6+˙) have been demonstrated. Isomerization by epoxide ring opening and 1,4‐hydrogen migration is suggested to explain the similar unimolecular chemistry observed for the two partners of each pair of isomers.
Investigation of singly charged dihalomethanes by collision spectroscopy
Authors: Bortolini O. , Hamadan M. , Traldi P. 
Published: May 2005

AbstractTranslational energy spectrometry (TES) and collision‐induced dissociation (CID) experiments on the singly charged ions, CH2CI2+˙, CH2Br2+˙ and CH2I2+˙ have been performed on a double‐focusing mass spectrometer. No TES peaks could be seen from CH2CI2+˙ due to inadequate sensitivity. The measured energies of a number of non‐dissociative electronic states of the incident ions of CH2ID2+˙ and CH2Br2+˙ are in agreement with energies reported by photoelectron spectroscopy. The latter technique indicates the presence of a weak band in the photoelectron spectrum kof CH2Br2 lying 8.4–9.4eV above its ground state. This band is evident in the TES spectrum of CH2Br2+˙ incident ions. Other electronic ststes are also observed and tentatively assigned.
Are gas‐phase processes really responsible for the ionization of cyclic acetals by fast‐atom bombardment?
Authors: Paul Gary J. C. , Bourg Serge , Bertrand Michel J. 
Published: May 2005

AbstractThe mass spectral behavior of a series of substituted 2‐phenyl‐1,3‐dioxolanes has been studied by several ionization techniques in order to gain further insight into the basic ionization mechanisms occurring in the fast‐atom bombardment mass spectrometry. The results obtained show that in chemical ionization, ions of the type [M+H]+ are predominant while [MH]+ ions are observed as important species in electron ionization and fast‐atom bombardment. Comparison of the gas‐phase hydride‐ion affinities of thr chemical ionization reagent gases ammonia and isobutane with those of the loquid matrices glycerol and dithiothereitol/dithioerythritol indicates that the predomionant formation of the [MH]+ ion observed in fast‐atom bombardment by hydride abstraction in the gas phase is improbable. Furthermore, comparison of the electron ionization behavior of the cyclic acetals with that observed under fast‐atom bombardment suggests that the origin of [MH]+ in the latter is not related EI gas‐phase processes.
Analysis of saxitixin in urine by continuous‐flow fast‐atom bombardment mass spectromety
Authors: Mirocha Chester J. , Cheong Wonjo , Mirza Urooj , Kim Young Bae 
Published: May 2005

AbstractAn improved method of saxitoxin analysis in urine using continuous‐flow fast‐atom bombardment mass spectrometry was developed. Parameters studied were matrix composition, matrix flow, temperature of probe tip, probe‐tip design and sample extraxtion. Optimal detection was obtained using the following matrix composition: 5% glycerol, 0.5% acetic acid, 0.025% sodium dodecylsulfate, 0.1% polyethylene glycol (PEG) 400 and 0.5% PEG 300; probe‐tip temperature: (∼55°C); flow rate: 5 or 8μL per min.; probe tip: Olson‐Hogge design. The STX standard was detected at 200pg with signal‐to‐noise ratio of 11. The percent recovery of saxitoxin from human urine after clean‐up on a weak cation exchange column was 75%.
Characterization of [C6H7N]+˙ radical cations by tandem mass spectrometry
Authors: Flammang Robert , Thoelen Olivier , Quattrocchi Calogero , Bredas Jean‐Luc 
Published: May 2005

AbstractCollisional Activation, charge‐stripping and neutralization/reionozation mass spectra allow the identification of six [C6H7N]+˙ isomers, namely the molecular ions of the three isomeric picolines, 1+˙–;3+˙, ionized 2‐ and 4‐methylene dihydropyridines, b—c, and ionized pyridinium methylide, a. The implication of the distonic forms a and b in some fragmentation reactions of funct of onalized (position 2) pyyridines is briefly discussed. Molecular orbital calculations indicate the b>a>1+˙ stability sequence.
Negative‐ion chemical ionization—collision‐induced dissociation study of unsubstituted cycloalkanols, alkanones and alkenones at low collisional energy
Authors: Decouzon M. , Géribaldi S. 
Published: May 2005

AbstractThe collision‐induced dissociation reactions of the [M1]− and [M3]− ions of cyclopentanol, cyclohexanol, cyclopentanone, cyclohexanone, cyclopent‐2‐en‐1‐one and cyclohex‐2‐en‐1‐one have been studied under lowenergy collisional activation using a Fourier‐transform ion cyclotron resonance mass spectrometer, and compared to literature data obtained at lhigh‐energy and under single‐collision conditions. Some significant differences appear in these data, which are discussed. Moreover, a general scheme of fragmentations appears between the alcohol, ketone and enone functions.
Dyanmic ion trapping for Fourier‐transform ion cyclotron resonance mass spectrometry: Simultaneous positive‐ and negative‐ion detection
Authors: Gorshkov Michael V. , Guan Shenbeng , Marshall Alan G. 
Published: May 2005

AbstractThe conventional static electric potential used to trap ions fro fourier‐transform ion cyclotron resonance (FTICR) mass spectrometry has been replaced by a low‐amplitude [as low as Vac≈︁0.5 V for N] alternating (17.5kHz) electric field applied to the end caps of an ICR ion trap. Ionz‐motion is then governed by a Mathieu equation, whose solution leads to az‐stability diagram for which optimal results are obtained atz‐stability parameter, qz= 4qλVac/(mω2)≈︁0.5, in whichm/qis the ion mass‐to‐charge ratio, Ω is the RF frequency, and λ=2.7737/d2for a cubic trap of edge length, d. A triangular waveform appears to be more effective than sinusoidal modulation. We demonstrate experimentally three major additional advantages of RF trapping for FTICR mass spectrometry: (a) both positive and negative ions may be trapped and detected simultaneously; (b) Magnetron motion is eliminated, along with the electrostatic radial field‐induced ICR frequency shift and sidebands; and (c) mass calibration follows a simpler law (m=a/v, in whichais a constant andvis the measured ICR orbital frequency) than for electrostatic trapping (m=a/v+b/v2, in whichaandbare constants). All prior FTICR mass spectrometric capabilities are preserved, except that (as in an RF‐only quadrupole ion trap) optimal sensitivity is observed only for 0.4⩽qz⩽0.7, so that the mass‐to‐charge ratio range for a single FTICR mass spectrum is limited accordingly.
On‐line liquid 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. , Voragen A. G. J. 
Published: May 2005

AbstractThe analysis of intact neutral oligosaccharides by on‐line liquid chromatography/thermospray mass spectrometry is described. Molecular‐weight information on oligomers up to a degree of polymerization of 10 is obtained using an aqueous mobile phase containing 10−4 mol/L sodium acetate, which was found to be compatible with thermospray interfacing and ionization. Ions due to sodiated and disodiated oligosaccharides are observed under these conditions without fragmentation. The aqueous 10−4 mol/L sodium acetate mobile phase is demonstated to be applicable in the separation of mixtures of oligosaccharides on a reversed‐phase octadecyl‐modified silica column.
Matrix‐assisted laser desorption mass spectrometry of oligodeoxythmidylic acids
Authors: Huth‐Fehre T. , Gosine J. N. , Wu K. J. , Becker C. H. 
Published: May 2005

AbstractFerulic acid, sinapinic acid and 2,5‐dihydroxybendoic acid (DHBA) have been tested as matrix materials for matrix‐asserted laser desorption of the pure oligonucleotide pd(T)12 and a mixture of oligonucleotides pd(T)12 through pd(T)18 using pulsed 337 nm radiation combined with reflecting time‐of‐flight mass spectrometry. The three matrix materials are compared with respect to obtainable mass resolution, degree of fragmentation, and adduct formation, as well as the highest mass resolution.
Observation of the fullerene anions C and C by electrospray ionization
Authors: Hiraoka Kenzo , Kudaka Ichiro , Fujimaki Susumu , Shinohara Hisanori 
Published: May 2005

AbstractMass spectsrometric investigation on the fullerence C60 and C70 was performed using electsdrospray ionization. C, C60O, C, and C70O ions were detected by reducing C60 and C70 using Nak amalgam in benzene + dimethoxyethane solvent. C was found to be much more reactive than C in solution.
Evidence for a lysine‐specific fragmentation in fast‐atom bombardment mass spectra of peptides
Authors: Ackermann Bradley L. , Barbuch Robert J. , Coutant John E. , Krstenansky John L. , Owen Thomas J. 
Published: May 2005

AbstractA fragmentation proccess observed for peptides that contain lysine, or other amino acids which possess a free amino group on their sidechain, is reported. The ions generated by this process are found 16 Da below the acylium‐type B ions that result from fragmentation at the C‐terminal side of lysine or other amine‐containing residues in fast‐atom bombardment (FAB) mass spectra. These ions, which are referred to as (B—16) ions, permit differentiation between the isobaric amino acids lysine and glutamine in peptide mass spectra. High resolution measurements indicate that (B—16) ions differ in composition from the corresponding B ions by the removal of one oxygen atom. Formation is believed to occur through a cyclization process initiated by nucleophilic attack by the free amino group of the lysine sidechain at the carbon of the acylium ion (B ion). A similar process initiated derectly from the protonated peptide may also occur. Analogous cyclization processes are restricted for glutamine because this residue is comparatively less nucleophilic than lysine (i.e., amide vs amine). Although (B—16) ions have been detected under high energy collisionally induced dissociation, they are formed less readily than by FAB mass spectrometry. A mechanism consistent jwith this observation as well as other experimental evidence is presented to account for the formation of (B—16) ions.
Electrospray‐ionization mass spectrometry for the detection of discrete peptide/metal‐ion complexes involving multiple cysteine (sulfur) ligands
Authors: Allen Mark H. , Hutchens T. William 
Published: May 2005

AbstractConditions have been developed to characterize the reversible interaction of one or more Zn(II) ions with cysteine (sulfur) ligands on metal‐binding peptides by electrospray‐ionization (ES) mass sspectrometry. A 71‐residue peptide with two separate clusters of four cysteine residues was selected as a model to optimize both the solution and electrospray variables most likely to affect the detection of stable cysteine (sulfur) ligland/Zn interactions. By infljusing peptide in water alone, stable elelctrospray and ion signals were produced in both the absence and presence of up to 100 uM zinc sulfate. In the absence of Zn(II), the callculated mass of the fully reduced peptide (8248.5 Da) was observed (8248.4±0.4 Da). In the presence of Zn(II), peptides with zero, one and two bound Zn atoms were detected; all three species were prelsent in several different charge states. The overall charge envelope was typically unchanged in the presence of Zn; the chaarge‐state optimum (10+) observed for this peptide dwas apparently unaffected by the dpresence dsof bound Zn. The interaction of Zn(II) ions with sulfur lilgands in this peptide appeared to result in tetracoordinate covalent bonds. In summary, these data suggest that (i) stable electrospray signals can be generated form high conductivity aqueous solutions of meltal ions; (ii) peptides with sulfur ligand/Zn complexas are stable to the ES ionization prolcess; (iii) bound Zn is not the primary source of charge and does not alter the observed charge‐envelope optimum; (iv) the relative distribution of peptide without bound Zn, with one bound Zn, and with two bound Zn atoms can be fully resolved in each of several different charge sltates; and (v) various solution factors affecting peptide/metal‐ion interaction stoichiomeltry can be investiged by ES. In conclusion, we believe dthat ES mass spectrometry is a powerful new method of evaluating a wide variety of specific biomolecular polymer/metal‐ion interactions.
Usefulness of fast‐atom bombardment and collision‐activated dissociation linked scan (B/E) mass spectrometry for structural investigation of indole alkaloids
Authors: Laprévote Olivier , Girard Christian , Das Bhupesh C. , Mukherjee Rabindranath 
Published: May 2005

AbstractPositive‐ion fast‐atom bombardment (FAM) mass sspectrometry was used to ionize two indole alkaloids, namely trinervine and its quaternary metho‐salt venecurine containing a hemiketal ring system. Analysis of collision‐activated dissociation spectra by the technique of linked scanning at consltant B/E gave sturcturally useful information. Addition of concentratedf acid to the glycerol matrix yielded glycoside‐type derivatives from both compounds. These studies Provide further examples of an ‘acid effect’ on the protonation site of polyfunlctional molecules along with the possibility of their undergoing chemical mokification in the FAB matrix.
A method for uniform optimization of quadrupole pre‐filters
Authors: Trajber Csaba , Simon Miklós , Bohátka Sándor 
Published: May 2005

AbstractNovel aspects of utilizing RF‐only pre‐filters in a quadrupole mass spectrometer are presented. Theoretical considerations converning the optimization of the spectrometer by means of the pre‐filter length and the ion entrance velocity are given and are given and are compared with the results of model calculations. Experimental results are shown to illustrate the advantages of the setup constructed according to the proposed optimization method over both the single mass filter and one with a pre‐filter of conventional length range. The most effectively focusing pre‐filters are shown to have integer multiples of an elementary length. The predictions have only been verified experimentally for helium. Apoproximeately 150% improvement was measured for helium transmission with respect to the single analyser with the suggestede parameters. Since the resolution always inporoves with length at a certain ion velocity, it is preferable to make use of some of the higher local minima of the suggestede optimizing function.
The components of the venom of a spider Scodra griseipes. 2. Structural information on biogenic amines using tandem mass spectrometry
Authors: Lange C. , Paris C. , Celerier M.‐L. 
Published: May 2005

AbstractBiogenic amines, which are components of tarantula Scodra griseipes venom, are studied using tandem mass spectrometry. Their heptafluoropropionic (PFP) derivatives are ionized under electron impact and isobutane‐chemical ionization. Daughter‐and parent‐ion mass spectra under collisionally activated dissociation conditions provide a more detailed study of such derivatives. Discrimination of di(PFP)amines and tri and tetra(PFP)amines is possible because of the presence of diagnosis ions induced by collision.
Sequential product‐ion spectra (MS3 and MS4) with array detection and reaction‐intermediate scanning on a four‐sector mass spectrometer
Authors: Ballard Kevin D. , Gaskell Simon J. , Jennings Richard K. C. , Scrivens Jim H. , Vickers Richard G. , Boyd R. K. 
Published: May 2005

AbstractFrangmentation yields during high‐energy collisionally activated decomposition (CAD) tandem mass spectrometie experiments are often low, due in part to the short time‐period available for the fragmentations. Consequently, attempts at multi‐stage mass spectrometry undeer high‐energy CAD conditions can give unsatisfactory result when a conventional point detector is used. Arry detection dramatically improves the detection of ion currents of low abundance; we therefore incorporated arry detection in a variety of sequential product‐ion ‘scanning’ experiments, including MS3 and MS4, using a BEBE instrument. The corresponding experiments were previously established on a BEqQ hybrid instrument. where the final stage of decomposition occurred under low‐energy CAD conditions. The results from the hybrid were used as a basis of comparison for the results under high‐energy CAD with array detection. On the BEBE instrument, the use of the array greatly enhanced the signal‐to background ratio for second‐and third‐generation product‐ion spectra, as compared to the use of the point detector on the instrument in several instances, the use of the array was criticaL to the success of the experiment on the four‐sector instrument. For the peptides analyzed, the fragmentation patterns observed in the sequential product spectra were similar on the four‐sector instrument and on the hybrid instrument, although the relative abundances differed between the high‐and low energy CAD regimes. Reaction‐intermediate scanning, involving two sequential decomposition step occurring on the microsecond high energy time scale, has also been implemented on the BEBE instrument. A New mode of reaction‐intermediate scanning has also been implemented on the BEqQ hybrid instrument, permitting it to access sequential fragmentation when both occur under high‐energy CAD conditions.
Differentiation between isomeric methylated purine derivatives by means of chemical ionization and collision‐induced dissociation
Authors: Curcuruto O. , Tarzia G. , Hamdan M. 
Published: May 2005

AbstractA number of commercially available purine derivatives were investigated by means of chemical ionization in ammonia and methane reagent gases. The protonated molecules of the compounds investigated were mass selected and their collision‐induced dissociated (CID) spectra monitored using 100 eV collision energy. Competition between the protonation and addition reaction channels which yield MH+ and [M + NH4]+ ions and the major fragment ions observed in the CID spectra reflect certain stereochemical differences between the isomeric precusors investigated. The present work is an attempt to contribute to the continuous search for first and effective means of distinguishing between the various isomers of biomedically important classes of compounds.
Thin layer chromatography/mass spectrometry: The advantages of tandem mass spectrometry
Authors: Monaghan J. J. , Morden W. E. , Johnson T. , Wilson I. D. , Martin P. 
Published: May 2005

AbstractThe results of thin layer chromatography/mass spectrometry (TLC/MS) and thin layer chromatography/tandem mass spectrometry (TLC/MS/MS) experiments are described. Spectra from the analytes were obtained directly from the absorbent without the need for extraction prior to analysis by mass spectrometry. These results illustrate the added specificity that the tandem mass spectrometer can afford in the detection and characterization of a range of compounds separated by TLC.
Association of the acylium ion of acids with alcohols as an esterification mechanism in chemical ionization
Authors: Tu Ya‐Ping , Chen Yao‐Zu 
Published: May 2005

AbstractThe reactions between aliphatic acids and alcohols in the gas phase were investigated by chemical ionization (CL) mass spectrometry. The association of the acylium ion of acids with alcohols is suggested as an esterificaion mechanism under CI conditions in addition to the classical nucleophilic addition—elimination pathway.
Charge promotion of low‐energy fragmentations of peptide ions
Authors: Burlet Odile , Orkiszewski Ralph S. , Ballard Kevin D. , Gaskell Simon J. , Bertrand M. J. 
Published: May 2005

AbstractWe have examined the hypothesis that structural features which predispose to localization of charge at a strongly favored site are not conducive to the low‐energy fragmentation of peptide ions via a multiplicity of pathways. Consistent with this proposal, it is demonstrated that the formation of N‐ or C‐terminal pre‐charged derivatives is detrimenal to the formation of sequence‐specific product ions following low‐energy collisional activation. Protonation of pre‐charged derivatives (yielding doubly charged ions) restores favorable fragmentation properties; the effect is attributed to the fragmentation‐directing properties of the proton whih may occupy one of several sites. Similarly, a doubly protonated peptide which incorporates a C‐terminal arginine residue as a single strongly favored site of protonation exhibits favored low‐energy fragmentations attributable to locaton of he second proton at one of several sites remote from the C‐terminus.