bluuebunny/crossref_metadata_2025_split huggingface dataset:
3‐aminopicolinic aid as a matrix for laser desorption mass spectrometry of biopolymers
Authors: Taranenko N. I. , Tang K. , Allman S. L. , Ch'ang L. Y. , Chen C. H. 
Published: May 2005

Abstract3‐Aminopicolinic acid (3‐APA) was tested and found to be a useful matrix for matrix‐assisted laser desorption/ionization of DNA and protein. Single‐stranded DNA segments of 150‐mer and double‐stranded DNA of 246 base pairs were successfully detected by using 3‐APA as an ultraviolet‐absorbing matrix in a linear time‐of‐flight mass spectrometer. In the case of the double‐stranded DNA, only parent ions corresponding to single‐stranded DNA were observed. The comparison with 3‐hydroxypicolinic acid and picolinic acid matrices is discussed.
2‐(4‐hydroxyphenylazo)‐benzoic acid: A solid matrix for matrix‐assisted laser desorption/ionization of polystyrene
Authors: Montaudo Giorgio , Montaudo Maurizio S. , Puglisi Concetto , Samperi Filippo , Daolio S. 
Published: May 2005

AbstractLiquid matrices are currently used in matrix assisted laser desorption ionization (MALDI) of non‐polar macromolecules, such as polystyrene. We investigated the possibility of using non‐liquid compounds as matrices. A series of polystyrene samples was analyzed by MALDI using a time‐of‐flight (TOF) analyzer. We found that a solid matrix, namely 2‐(4‐hydroxyphenylazo)‐benzoic acid, yields quality mass spectra. The MALDI‐TOF spectra were used to measure the parameters which characterize the molecular weight distributions of the polystyrene samples. The values obtained by MALDI‐TOF were in good agreement with those obtained by other methods.
Differentiation of bacteria using protein profiles from matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Cain Teresa C. , Lubman David M. , Weber Walter J. 
Published: May 2005

AbstractMatrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry is demonstrated as a means for rapidly differentiating bacteria based upon their water‐soluble‐protein profiles. The procedure involves release of cell contents by breaking cell membranes using a sonication method, and is performed with minimal sample preparation. Minimal purification of cell contents is required for the procedure. Protein profile signals obtained are found to be enhanced greatly by the use of a Nafion substrate.
A new mass spectrometric approach to detect modifications in DNA
Authors: Janning Petra , Schrader Wolfgang , Linscheid Michael , Baillie T. A. 
Published: May 2005

AbstractA new approach is described for the enzymatic digestion of DNA yielding oligonucleotides ranging from dinucleoside monophosphates to octanucleoside heptaphosphates. DNA was digested by means of the benzon nuclease, an unspecific nuclease, and alkaline phosphatase to remove the terminal phosphate. The mixture of oligonucleotides was separated using capillary‐zone electrophoresis with a buffer system, yielding a rather strong electro‐osmotic flow. The oligomers are separated into groups with nucleotides of the same chain length. The separation capillary was used as the innermost capillary of an electrospray spraying system. Negative molecular ions of the nucleotides were recorded using a home‐built interface and ion source for a sector‐field mass spectrometer. This approach allows the facile detection of DNA modifications since they lead not only to differences in mass, but also can possess altered electrophoretic mobility. For modifying reactions which exhibit sequence specificity, the information is retained in the oligomers. Thus, reactions of DNA with electrophiles can be evaluated at different levels, since in longer chains, even complex sequence specificity may be apparent. Results from calf thymus DNA digests and preliminary experiments with DNA adducts with styrene oxide are discussed.
Long‐distance stereochemical effects in deprotonated epimeric androstanediols in tandem mass spectrometry
Authors: Garcia P. , Popot M. A. , Fournier F. , Tabet J.‐C. 
Published: May 2005

AbstractTandem mass spectrometry in negative‐ion mode using ammonia as reagent gas has contributed to the differentiation of polyhydroxysteroids and to the study of stereochemical effects. The present study provides additional examples of sterochemical effects. A first observation of intramolecular OH− catalysis yielding stereospecific H2O elimination is proposed.
Evaluation of glycosylation site heterogeneity and selective identification of glycopeptides in proteolytic digests of bovine α1‐acid glycoprotein by mass spectrometry
Authors: Hunter Ann P. , Games David E. 
Published: May 2005

AbstractGlycosylation sites in bovine α1‐acid glycoprotein (AGP) have been identified, and the inherent heterogeneity evaluated, by capillary electrophoretic and reversed‐phase liquid chromatography/electrospray‐mass spectrometric analyses of proteolytic digests of this glycoprotein. The success of these methods in locating glycopeptides relied on significant heterogeneity within each glycosylation site. In order to rapidly locate sites in glycoproteins of any degree of heterogeneity, a novel mass spectrometric method was applied to selectively identify the glycopeptides in a proteolytic digest of bovine α1‐AGP. The glycopeptides were selectively located by the generation and detection of characteristic oxonium ions from the carbohydrate moieties by collision‐induced dissociation (CID) during liquid chromatography/electrospray‐tandem mass spectrometry, and liquid chromatography/CID mass spectrometry, in which fragmentation was induced in the supersonic expansion region of the electrospray source.
Electron ionization mass spectra and metastable‐ion studies on some dicyanoquinonediimines
Authors: Martin Nazario , Seoane Carlos , Garin Javier , Orduna Jesús 
Published: May 2005

AbstractThe 70 eV mass spectra of dicyanoquinonediimine and several derivatives have been studied by accurate mass measurements and metastable‐ion analysis. Characteristic fragmentations of quinone structures and cleavages involving cyanide rearrangement are responsible for most of the total ion current.
Metal‐ion attachment to non‐polar polymers during laser desorption/ionization at 337 nm
Authors: Mowat Ian A. , Donovan Robert J. 
Published: May 2005

AbstractThe attachment of metal ions to non‐polar polymers is shown to be readily achieved using 337 nm laser desorption and ionization, with time‐of‐flight mass analysis, and could thus prove useful for the analysis of such polymers using commercially available matrix‐assisted laser desorption/ionization instruments. Attachment of Cr+, Cu+ and Ag+ has been used successfully to increase the ion yield of polystyrene and polybutadiene during laser desorption/ionization. The metal ion used may originate from the metal sample holder substrate on which the polystyrene is placed, or from metal salts mixed with the polystyrene either prior to placement on the sample holder or in situ. Results have been obtained which illustrate metal‐ion attachment to the polystyrene from the substrate and from a dopant salt simultaneously and the roles of each of these will be discussed.
Polymer molecular weight distribution: Results from matrix‐assisted laser desorption ionization compared with those from gel‐permeation chromatography
Authors: Lehrle Roy S. , Sarson Deborah S. 
Published: May 2005

AbstractA sample of poly(methyl methacrylate) (PMMA), of which the molecular weight was known from light‐scattering measurements, was subjected to gel‐perrneation‐chromatographic analysis, and the resulting Weight versus log molecular weight (MW) plot was converted by suitable computation to a Number versus linear MW plot. This could then be compared directly with the matrix‐assisted laser desorption ionization MW distribution results obtained for the same sample. The MW distributions obtained by the two methods were significantly different. Two explanations for the discrepancy are offered.
Relationship of Fourier transforms to isotope distribution calculations
Authors: Rockwood Alan L. 
Published: May 2005

AbstractIsotope distributions of molecules are the result of convoluting elemental isotope distributions multiple times. They are usually calculated using a polynomial expansion method. The present paper starts with the polynomial expansion and shows how to cast the problem in terms of Fourier transforms. Because discrete Fourier transforms can be calculated very efficiently, this new way of looking at the problem has significant practical implications. Specifically, it leads to faster ways to calculate isotope distributions.
Investigation of ‘ghost’ peaks caused by non‐linear fields in the ion trap mass spectrometer
Authors: Mo Wenjun , Langford Marian L. , Todd John F. J. 
Published: May 2005

AbstractMass spectral ‘ghost peaks’ are generated with the ion trap by the superposition of higher order multipole fields which originate through deviations from the pure quadrupole field. In data acquisition, when the amplitude of the RF voltage is ramping though a non‐linear resonance point (q*) on the Mathieu stability diagram, some ions (m0) are ejected by the non‐linear field rather than by the quadrupole field at qz=0.908 on the βz=1 boundary. The prematurely ejected ions will be seen as a peak at m1=(q*/0.908)m0, which we have termed a ‘ghost peak’.
AC corona‐discharge aerosol‐neutralization device adapted to liquid chromatography/particle beam/mass spectrometry
Authors: Wilkes Jon G. , Freeman James P. , Heinze Thomas M. , Lay Jackson O. , Vestal Marvin L. 
Published: May 2005

AbstractAn AC corona‐discharge device was inserted upstream of a thermospray vaporizer tip in a liquid chromatography/particle beam mass spectrometer to neutralize static aerosol charging. Response of a test analyte was measured with or without discharge initiation. If the solvent contained no ammonium acetate buffer, increased analyte signal was associated with the discharge. However, in the presence of ammonium acetate the benefit of AC discharge neutralization was either not observed or was more subtle. This led to the conclusion that the previously observed ammonium acetate “carrier” effect is attributable, at least in part, to neutralization of static electric charges produced spontaneously during the solvent nebulization process. In a second experiment, the pattern of particles issuing from the system momentum separator was examined by aiming the particle beam at a cold target located within a mass spectrometer ion source. Variations in particle density were observed depending on (i) whether or not the aerosol had been neutralized and (ii) the proximity of electron‐beam‐collimating magnets to the particle beam trajectory. These results are consistent with a hypothesis that electrostatic charging occurs spontaneously during the nebulization process in which an aerosol is formed from the high performance liquid chromatography effluent. Such electrostatic charging introduces a factor likely to degrade system performance by at least two modes: through interactions of the charged aerosol particles (i) with the walls of the aerosol transmission pathway, and, after they are accelerated into a particle beam and introduced into the mass spectrometer, (ii) with the magnets used for electron beam collimation in many mass spectrometer ion sources.
Reduction of aromatic fluorine compounds in fast‐atom bombardment mass spectrometry
Authors: Aubagnac J. L. , Gilles I. , Claramunt R. M. , Escolastico C. , Sanz D. , Elguero J. 
Published: May 2005

AbstractThe second example of F/H reduction of a fluorine aromatic derivative in a fast‐atom bombardment mass spectrometric experiment is described. It concerns a tetrafluorophenyl derivative bearing two 3,5‐dimethylpyrazol‐1‐yl substituents.
Unusual cross‐ring SN2 reactions of [MH]− ions of methoxyacetanilides
Authors: Blanksby Stephen J. , Dua Suresh , Bowie John H. 
Published: May 2005

AbstractDeprotonated o, m‐, and p‐methoxyacetanilide show pronounced peaks in their collision‐induced tandem mass spectra (MS/MS) produced by losses of the elements of C2H6. It is proposed that this reaction is a ‘cross‐ring’ internal SN2 reaction involving an incipient methyl anion. For example, p‐CH3OC6H4−COCH3→ [(p‐CH3OC6H4NCO)CH]→−OC6H4NCO+C2H6.
A molecular ion source based on spontaneous desorption
Authors: Schoppmann Christopher , Brandl Dieter , Tomaschko Christoph , Schurr Matthias , Voit Helmut 
Published: May 2005

AbstractA novel molecular ion source based on the spontaneous desorption process has been investigated. The results obtained indicate that it is well suited for the analysis of organic molecules with masses up to 103 u in a time‐of‐flight mass spectrometer.
Gas phase acetylation of C60 and C70 by ion/molecule reactions
Authors: Liu Ziyang , Hao Guolun , Guo Xinghua , Liu Shuying 
Published: May 2005

AbstractGas phase reactions of C60 and C70 with the ion system of acetone under chemical ionization conditions have been studied. C60 and C70 can react with acetyl and oxonium ions, which come from self‐chemical ionization of acetone, to form adduct ions. In addition, C60 and C70 can accept protons to produce protonated ions. C70 is more active in the above reactions than C60 because of its stronger gas‐phase basicity. A σ‐bond between C60 and an acyl carbon atom can be formed to produce stable acetylated C60 ions. The above results may be relevant to the acetylation reactions of C60 in the condensed phase.
A new method for the determination of iron oxidation states by resonant and non‐resonant ionization mass spectrometry
Authors: Maunit B. , Hachimi A. , Calba P. J. , Krier G. , Muller J. F. 
Published: May 2005

AbstractDifferent compositions of micrometric particles of powdered iron oxides (Fe1−xO, Fe3O4 and Fe2O3) are examined by time‐of‐flight laser microprobe mass spectrometry. The positive‐ion cluster distributions show a strong correlation with the stoichiometry of iron in the oxide. This correlation is more striking when the resonant process of iron at 293.7 nm is used. The bond dissociation energy of Fe–‐O in the bulk Fe1−xO also affects the intensity distributions. It is very important to study and to identify the iron oxides because they could play a role in the toxicity of certain molecules which could be removed on the oxides.
Mass spectral fragmentation patterns of some new benzo[b]thiophene‐ and thieno[2,3‐b]thiophene‐2,5‐dicarbonyldichlorides and ‐dicarbonyldianilides and anilidoquinolones
Authors: Karminski‐Zamola Grace , Dogan Jasna , Boykin David W. , Bajić Miro 
Published: May 2005

AbstractThe electron impact mass spectra of some benzo[b]thiophene‐ and thieno[2,3‐b]thiophene‐2,5‐dicarbonyldichlorides, 2,5‐dicarbonyldianalides, 9‐anilido‐benzo[b]thienyl[2,3‐c]quinolones and 9‐anilido‐thieno[4,5‐b′]thienyl[2,3‐c]quinolones are discussed. Dominant peaks in dianilides are formed by cleavage of the CN bond on one side of the anilido group, as well as on the anilido group itself in anilidoquinolones. These ions fragment further by the cleavage of a CC bond in dianilides and the CONRPh group is lost directly, while the quinolonic part of the molecule in quinolones fragments with low probability. Characteristic fragment ions of dicarbonyldichlorides arise by the cleavage of the CCl bond.
Intra‐ and interannular substituent migration and intramolecular ipso substitution of biphenyl derivatives in mass spectrometry
Authors: Tu Ya‐Ping , Liu Ya‐Qin , Liu Shu‐Ying 
Published: May 2005

AbstractBiphenyl derivatives undergo extensive intraannular substituent migrations and subsequent intramolecular ipso substitutions giving rise to a fluorenyi cation and a biphenylene radical cation as common products in mass spectrometry. For biphenyls bearing an alkyl group, interannular substituent migration resulting in a substituted tropylium ion is also observed. Electron‐withdrawing groups are found to be much more favourable to these reactions than the electron‐donating ones.
Identification of novel nucleotides found in the red seaweed Porphyra umbilicalis
Authors: Newton Russell P. , Kingston Eric E. , Overton Alan 
Published: May 2005

AbstractExtracts of the red seaweed Porphyra umbilicalis are a valuable constituent of herbal medicines. The nucleotide complement of such an extract was purified and compounds identified by chromatographic behaviour, UV absorbance/pH profile, base‐to‐phosphate ratio, acid hydrolysis, and by fast‐atom bombardment mass spectrometry with mass‐analysed ion kinetic energy spectrum scanning. In addition to eighteen common nucleotides, and two cyclic nucleotides, fifteen novel nucleotides were identified, comprising eight deoxynucleotides and two cyclic deoxynucleotides, ten aminoacylnucleotides and two nucleoside trisphosphates together with 2′‐phosphoadenosine‐3′,5′‐cyclic pyrophosphate, 5′‐phosphoadenosine‐2′,3′‐cyclic monophosphate and N6,N6‐dimethyladenosine‐5′‐monophosphate. The possible origin and potential actions of these novel compouds are discussed.
Study of the interactions of intense laser beams and of fast‐ion beams with molecules
Authors: Kumar G. Ravindra , Safvan C. P. , Rajgara F. A. , Mathur D. 
Published: May 2005

AbstractMolecular dynamics in intense, pulsed laser fields is an emerging frontier of research in laser–matter interactions. Mass spectrometric techniques are essential to understanding the behaviour of molecules in such fields. We present some salient features of this activity and review some of our recent experimental observations. Results concerning the roles of dissociation and ionization of simple diatomics and triatomics are presented. Further, comparisons are made between the forces experienced by molecules in intense laser fields and in collisions with fast ion projectiles. The dissociative ionization patterns of CS2 and CH4 in the two situations are discussed and the differences in the intense laser field dissociative ionization are attributed to the polarization property of laser light.
Application of the time‐dependent wavepacket method to mass spectrometric studies of molecular excitation and dissociation
Authors: Krishnamurthy M. , Gross P. , Mathur D. 
Published: May 2005

AbstractA new time‐dependent wavepacket approach has been applied to illustrate a rigorous method of calculating the transition function for bound‐to‐continuum transitions in translational energy spectrometric experiments. The method is numerically exact and fully quantal, and is devoid of any classical or semi‐classical approximations. The validity of the hitherto‐applied reflection approximation is investigated in a comparative study. The method has been applied to two different translational energy spectrometry experiments: collision‐induced dissociation of CO+ and collisional excitation of H2.
Light emission from impacts of energetic proteins on surfaces and a light emission detector for mass spectrometry
Authors: Sullivan Patrick A. , Axelsson Jan , Sundqvist Bo U. R. 
Published: May 2005

AbstractPhoton emission from impacts of electrosprayed protein ions onto Au, Ta, Si and CsI surfaces was studied. Mass spectra of insulin, lysozyme and apo‐myoglobin were acquired by scanning the mass‐to‐charge ratio of a quadrupole mass filter while simultaneously detecting the photon and secondary electron signals. These spectra were very similar, but spectra acquired using photons displayed a somewhat better signal‐to‐noise ratio. The estimated photon emission yield is of the order of 0.5 photons per ion impact, a quantity which is not strongly dependent on target material. A higher yield of photons per incident ion was observed for apo‐myoglobin and lysozyme ions than for insulin ions.
Mass spectral fragmentation patterns of some new 3,7‐dichloro‐benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐dicarboxylic acid dianilides and 3,5‐dichloro‐dithieno[3,2‐b:2′,3′‐d]thiophene‐2,6‐dicarboxylic acid dianilides. II
Authors: Karminski‐Zamola Grace , Malešević Miro , Blažević Nikola , Bajić Miro , Boykin David W. 
Published: May 2005

AbstractThe electron impact mass spectra of some benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐dicarboxylic acid dianilides and dithieno[3,2‐b:2′,3′‐d]thiophene‐2,6‐dicarboxylk acid dianilides are discussed. Dominant peaks in these dianilides are formed by the cleavage of a CN bond on one side of an anilino group. These ions fragment further by the cleavage of a CC bond on the other side of an anilino group and a CONRPhR′ group may be lost directly. After loss of CO, the characteristic benzodithiophene radical cation, C10H2S2Cl, at m/z 256 and the dithienothiophene radical cation, C8S3Cl, at m/z 262 are formed from their respective precursor compounds.
Fragmentation rules in plasma desorption mass spectrometry
Authors: Kargar Taraneh , Bourcier S. , Hoppilliard Y. 
Published: May 2005

AbstractSeveral studies concerning the analysis and quantification of biological and pharmaceutical compounds have been effected during the past 20–30 years using different techniques of desorption‐ionization. In most cases, however, the authors have not been interested in the mass spectrometric fragmentation mechanisms of these products. Plasma desorption mass spectrometry (PDMS) is a powerful technique for analysing, without matrix interferences, solid biological and pharmaceutical compounds. In this work, we use PDMS in order to study the influence of the amine (amide) function on the fragmentation processes of nitrogen‐containing compounds. For this work, quaternary ammonium salts, trisubstituted amines, disubstituted amines and a compound with an amide function were chosen. Classical PD mass spectra, accurate mass measurements, transitions in the field free region (FFR), labelled compound spectra and thermodynamical data are reported for the structural study of these compounds. Our results allow us to propose fragmentation rules for positively charged nonfunctional biological nitrogen compounds. These rules relate to a class of structurally informative decomposition reactions that can be applied to the determination and of identification of structural unknowns.
Translational energy spectroscopy. Spin‐conservation studies in collisional excitation processes
Authors: Enos C. S. , Lee A. R. , Brenton A. G. 
Published: May 2005

AbstractHigh‐resolution translational energy spectroscopy is an effective means of obtaining detailed state‐selective information, permitting systematic investigation of spin conservation in collisional processes. In this paper, we examine collisional excitation of one selected singlet (N2) and one non‐singlet (O2) target by a variety of projectile ions, providing a kaleidoscope of assorted effects.
Characterization of polymers by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry: Molecular weight estimates in samples of varying polydispersity
Authors: Montaudo Giorgio , Montaudo Maurizio S. , Puglisi Concetto , Samperi Filippo 
Published: May 2005

AbstractMatrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) allows the detection of large molecules such as those present in synthetic and natural macromolecules. Synthetic polymers may show a wide range of molecular weight distributions (MWD), according to the synthetic method used in their preparation. We have studied several poly(methylmethacrylate) (PMMA), poly(styrene) (PS) and poly(ethyleneglycol) (PEG) samples with varying MWD, and also a number of condensation polymers such as Nylon‐6, poly(carbonate) and poly(ester). Measurements of MALDI‐TOF spectra in the linear mode were used in our work to estimate the molecular weight (MW) and MWD of the polymer samples. Our results show that the molecular weight estimates provided by MALDI‐TOF measurements agree with the values obtained by conventional techniques, such as gel‐permeation chromatography (GPC), only in the case of polymer samples with very narrow molecular weight distribution. However, when the polydispersity reaches values around 1.10 the difference between the MW measured by GPC and measured by MALDI may amount to up to about 20%. At higher dispersions, the MALDI spectra fail to yield reliable MW values.