bluuebunny/crossref_metadata_2025_split huggingface dataset:
The ‘apparent’ hydrolysis of alkyl esters during electrospray ionization
Authors: Silvestri Maximilian A. , Miles Deborah , Rothwell Arlene P. , Wood Karl V. , Cushman Mark 
Published: July 2003

AbstractElectrospray ionization (ESI) mass spectrometry was employed to obtain both molecular weight confirmation and structural information for a series of novel alkenyldiarylmethane (ADAM) analogs. The mass spectral data were intended for use during the structure elucidation of ester hydrolysis products formed during an in vitro metabolism study of a series of novel ADAM analogs. The data on the precursor molecules show the presence of the molecular ion peak, [M+H]+, as well as a peak consistent with the hydrolysis product of the original ester ([MH‐ROH+H2O]+). However, chemical ionization mass spectrometry, elemental analysis and 1H NMR data indicated the presence of only the intact diester compounds, suggesting that the formation of the hydrolysis product was an instrumental artifact, i.e., in‐beam hydrolysis during ESI or a result of longer ion residence times of the ion trap mass analyzer. Copyright © 2003 John Wiley & Sons, Ltd.
Workplace monitoring of isocyanates using ion trap liquid chromatography/tandem mass spectrometry
Authors: Vangronsveld Erik , Mandel Friedrich 
Published: July 2003

AbstractA sensitive liquid chromatography/ion trap tandem mass spectrometry method was developed for the qualitative and quantitative detection of isocyanates in air. The method is based on derivatization of isocyanates with 1‐(2‐methoxyphenyl)piperazine during air sampling. The extracts are analyzed using an ion trap LC/MS system equipped with an electrospray (ESI) ion source. The method shows high linearity, specificity, accuracy and precision. The limits of detection are 40× to 55× lower than with UV‐based methods. Copyright © 2003 John Wiley & Sons, Ltd.
Characterization of Ganstigmine metabolites in hepatocytes by low‐ and high‐resolution mass spectrometry coupled with liquid chromatography
Authors: Pelizzi Nicola , Puccini Paola , Riccardi Benedetta , Acerbi Daniela , Catinella Silvia 
Published: July 2003

AbstractIn order to deepen the understanding of the metabolism of Ganstigmine, a new acetylcholinesterase inhibitor under evaluation for the treatment of Alzheimer's disease, samples obtained by incubating the drug with female rat hepatocytes were investigated by low‐resolution liquid chromatography/tandem mass spectrometry (LC/MS/MS). The results confirmed the formation of most of the phase I metabolites already demonstrated, but also three new species. The combination of high‐resolution quadrupole time‐of‐flight (Q‐TOF) LC/MS and LC/MS/MS measurements, and the evaluation of the more reasonable metabolic routes, allowed the identification of the new metabolites as Geneseroline‐glucuronide and oxidized and rearranged Ganstigmine. Analogous investigations were made using hepatocytes from male rat and dog, and both gender monkeys and humans, to compare the metabolic patterns. The results did not indicate substantial differences in terms of numbers and abundances of detected metabolites among the considered species, and also between male and female hepatocytes within each species. Copyright © 2003 John Wiley & Sons, Ltd.
Mass spectrometric studies of cyclopentanol derivatives in the reductive coupling of α,β‐unsaturated ketones assisted by samarium diiodide
Authors: Le Lagadec Ronan , Rubio Laura , Velasco Luis , Pérez‐Flores Javier , Miranda Rene , Cabrera Armando 
Published: July 2003

AbstractThe mass spectrometric fragmentations of a series of cyclopentanol derivatives in positive fast‐atom bombardment (FAB+) mode were investigated. The corresponding pathways proposed were confirmed by MS/MS data obtained using linked scans at constant B/E, high‐resolution accurate mass data, and comparisons with corresponding information for a specifically deuterated molecule. Copyright © 2003 John Wiley & Sons, Ltd.
Electrospray ionization from a droplet deposited on a surface‐modified glass rod
Authors: Jeng Jingyueh , Shiea Jentaie 
Published: July 2003

AbstractThis paper reports development of a non‐mechanical electrospray ionization (ESI) method to generate electrospray from a droplet deposited on an optical fiber coated with a thin gold or Nafion film. Modification of the surface of the optical fiber in this manner increases its wettability, such that a droplet of the aqueous sample solution can adhere sufficiently strongly to the tip of the fiber. The aqueous sample solution was deposited near the tip of the fiber with a micropipette. When a high voltage (2000 V) was applied to the fiber by electrical connection through the gold film, the sample solution moved and hung at the tip of the fiber. Simultaneously, ESI was generated from the sample droplet. Multiply charged peptide and protein ions were detected by connecting the ESI source to a quadrupole mass analyzer. Copyright © 2003 John Wiley & Sons, Ltd.
Selective solid‐phase isolation of methionine‐containing peptides and subsequent matrix‐assisted laser desorption/ionisation mass spectrometric detection of methionine‐ and of methionine‐sulfoxide‐containing peptides
Authors: Grunert Tom , Pock Katharina , Buchacher Andrea , Allmaier Günter 
Published: July 2003

AbstractMethionine residues and the oxidised forms in proteins are becoming more and more important in view of their biological function. In particular, methionine sulfoxide seems to have a regulatory function. This paper presents a fast strategy for simultaneous determination of methionine‐ and methionine‐sulfoxide‐containing peptides, involving application of methionine‐specific solid‐phase reagent chemistry combined with matrix‐assisted laser desorption/ionisation mass spectrometry (MALDI‐MS). In the first step, methionine‐containing peptides are covalently bound as sulfonium salts to glass beads, whereas methionine‐sulfoxide‐containing peptides and other methionine‐free peptides are not bound and are washed out. The wash solution is used for MALDI‐MS analysis to determine the molecular masses of these peptides and to perform, if necessary, seamless post‐source decay (PSD) fragment ion analysis. Methionine‐sulfoxide‐containing peptides can be identified due to the characteristic metastable loss of methanesulfenic acid from the protonated molecules. In the second step, the bound peptides are cleaved from the matrix of the beads by addition of 2‐mercaptoethanol at pH 8.5–8.8. The resulting peptides, mainly methionine‐containing peptides, are analysed in a straightforward manner by MALDI‐MS and seamless PSD. The strategy allows the fast identification of methionine‐ and methionine‐sulfoxide‐containing peptides even in complex tryptic digests, as demonstrated here for the glycoprotein antithrombin. These results show that sometimes methionine‐containing tryptic peptides are not detected due to steric restrictions (e.g. glycosylation near the methionine residue) on the binding reaction, and that, on the other hand, some methionine‐free peptides can be quite strongly bound non‐covalently to the matrix of the beads. The latter observation indicates the necessity of seamless PSD fragment ion analysis for unambiguous identification. Furthermore, there are indications that oxidation of some methionine residues occurred to a minor extent during the solid‐phase isolation steps. Copyright © 2003 John Wiley & Sons, Ltd.
Determination of a correction to improve mass measurement accuracy of isotopically unresolved polymerase chain reaction amplicons by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry
Authors: Null Allison P. , Muddiman David C. 
Published: July 2003

AbstractThe experimental determination of average mass by mass spectrometry is limited for large molecules due to the negative bias introduced by the natural distribution of isotopic abundances. This results in the measurement of the top‐of‐centroid (ToC) as opposed to the true centroid. We have developed a practical correction factor that is applied to the ToC measurement to largely remove the systematic bias introduced by nature. The correction factor is calculated easily using the average molecular mass (<100 kDa) of the analyte molecule and the full‐width half maximum resolving power (<3500) of the measurement. In addition, an approach to calculating resolving power is described that accurately predicts resolving power achievable for Fourier transform ion cyclotron resonance (FT‐ICR) mass analysis of large molecules. A combination of internal calibration with a dual‐electrospray source and application of the correction factor to average mass measurements improved the mass error from 192.5 to −35.0 ppm for a 44 kDa PCR amplicon. Copyright © 2003 John Wiley & Sons, Ltd.
Preliminary investigation of the simultaneous detection of sugars, ascorbic acid, citric acid, and sodium benzoate in non‐alcoholic beverages by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Ayorinde Folahan O. , Bezabeh Dawit Z. , Delves I. G. 
Published: July 2003

AbstractMatrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) was used for the simultaneous detection of sugars, ascorbic acid, citric acid, sodium and/or potassium benzoate in non‐alcoholic beverages, with meso‐tetrakis(pentafluorophenyl)porphyrin (MW 974) as a matrix. Using potassium hydroxide as dopant, fructose/glucose was detected as the potassiated molecule at m/z 219, whereas potassiated sucrose, [Sucrose · K]+, was detected at m/z 381. Using sodium hydroxide as dopant, the fructose and sucrose ions were detected at m/z 203 and 365, respectively. Citric acid generated multiple ions at m/z 269, 307, and 345, which were assigned to [CitricH+2K]+, [Citric2H+3K]+, and [Citric3H+4K]+, respectively. However, a stored methanolic solution of citric acid produced additional ions at m/z 283, 297, and 321, which were attributed to [Citric2H+CH3+2K]+, [Citric3H+2CH3+2K]+, and [Citric3H+CH3+3K]+, respectively, due to esterification that took place during storage. The limits of detection in water were: ascorbic acid, 0.30 wt%; citric acid, 0.5 wt%; and sodium benzoate, 0.001 wt%. In the beverage formulations, the limits of detection were: ascorbic acid 0.3 wt%, citric acid 0.3 wt%, and sodium benzoate 0.02 wt%. Spiking a water or beverage solution that contained ascorbic and/or citric acid with less than 0.6 wt% of tartaric acid lowered the detection limits of ascorbic and citric acids to 0.2 wt%. This study demonstrates the potential for using MALDI‐TOFMS in the quality control analyses of non‐alcoholic beverages, particularly with regard to the detection of low molecular weight organic acids in commercial beverage formulations. Copyright © 2003 John Wiley & Sons, Ltd.
Matrix‐assisted laser desorption/ionization directed nano‐electrospray ionization tandem mass spectrometric analysis for protein identification
Authors: Kast Juergen , Parker Carol E. , van der Drift Koen , Dial J. Michael , Milgram Sharon L. , Wilm Matthias , Howell Michael , Borchers Christoph H. 
Published: July 2003

AbstractIn those cases where the information obtained by peptide mass fingerprinting or matrix‐assisted laser desorption/ionization tandem mass spectrometry (MALDI‐MS/MS) is not sufficient for unambiguous protein identification, nano‐electrospray ionization (nano‐ESI) and/or electrospray ionization tandem mass spectrometry (ESI‐MS/MS) analysis must be performed. The sensitivity of nano‐ESI/MS, however, is lower than that of MALDI‐MS, especially at very low analyte concentrations and/or in the presence of contaminants, such as salt and detergents. Moreover, to perform ESI‐MS/MS, the peptide masses of the precursor ions must be known. The approach described in this paper, MALDI‐directed nano‐ESI‐MS/MS, makes use of information obtained from the more sensitive MALDI‐MS experiments in order to direct subsequent nano‐ESI‐MS/MS experiments. Peptide molecular ions found in the MALDI‐MS analysis are then selected, as their (+2) precursor ions, for nano‐ESI‐MS/MS sequencing, even though these ions cannot be detected in the ESI‐MS spectra. This method, originally proposed by Tempst et al. (Anal. Chem. 2000, 72: 777–790), has been extended to provide better sensitivity and shorter analysis times; also, a comparison with liquid chromatography/tandem mass spectrometry (LC/MS/MS) has been performed. These experiments, performed using quadrupole time‐of‐flight instruments equipped with commercially available nano‐ESI sources, have allowed the unambiguous identification of in‐gel digested proteins at levels below their ESI‐MS detection limits, even in the presence of salts and detergents. Copyright © 2003 John Wiley & Sons, Ltd.
Reactions between M+ (M = Si, Ge, Sn and Pb) and benzene in the gas phase
Authors: Xing Xiaopeng , Tian Zhixin , Liu Hongtao , Tang Zichao 
Published: July 2003

AbstractUsing a laser ablation/inert buffer gas ion source coupled with a reflectron time‐of‐flight mass spectrometer, the gas‐phase reactions between the IVA group element ions M+ (M = Si, Ge, Sn and Pb) and benzene seeded in argon gas were studied. In addition to the association reaction pathway (forming [M(C6H6)x]+, x = 1, 2, etc.), benzene was dissociated to form complex ions [M(C5H5)]+, [M(C7H5)]+ and [M(C9Hx)]+ (x = 5, 7 and 9), etc. DFT theoretical calculations indicated that, in the association products [M(C6H6)]+, the M atom is close to one carbon atom of benzene, while in most of the dissociation complexes, pentagonal structures (M/cyclopentadienyl derivatives) were formed, with the M atom situated near the fivefold axis of the five‐membered ring. The bond patterns in these complexes are discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Hemoglobin adducts from glycidamide: acetonization of hydrophilic groups for reproducible gas chromatography/tandem mass spectrometric analysis
Authors: Paulsson Birgit , Athanassiadis Ioannis , Rydberg Per , Törnqvist Margareta 
Published: July 2003

AbstractAcrylamide (AA) is a reactive compound widely used as an industrial chemical. It is also, as recently shown, present in heated foodstuffs. AA is known to cause tumors in rodents and is classified as probably carcinogenic to humans. The metabolite glycidamide (GA) is assumed to be the predominant genotoxic agent in AA exposure. Therefore, knowledge about in vivo doses of GA is essential for cancer risk assessment of exposure to AA. The in vivo dose of GA could be inferred from the level of the adduct formed by GA with N‐terminal valine (GA‐Val) in hemoglobin (Hb), detached as a pentafluorophenylthiohydantoin (PFPTH) and measured by gas chromatography/tandem mass spectrometric (GC/MS/MS) analysis. However, due to the highly polar character of the GA‐Val‐PFPTH derivative, it was found necessary to modify the method through further derivatization. This paper presents an evaluation of acetonization for derivatization of the adjacent OH and NH2 groups in the adduct formed from GA. Good reproducibility was obtained. Also, acetonization improves the response and thus increases the sensitivity of the GC/MS/MS analysis of the PFPTH derivative of GA‐Val. The sensitivity obtained is sufficient for studies of background adduct levels of GA in animals and in humans. Acetonization as a method for derivatization is robust and simple. Copyright © 2003 John Wiley & Sons, Ltd.
Particle beam glow discharge mass spectrometry: spectral characteristics of nucleobases
Authors: Davis W. Clay , Venzie Jacob L. , Willis Bert , Coffee R. Lane , Arya Dev P. , Marcus R. Kenneth 
Published: July 2003

AbstractUse of a particle beam glow discharge (PB‐GD) source for mass spectrometric determinations of deoxy‐ and ribonucleosides and nucleotides is described. Use of this combination of sample introduction and ion source decouples the vaporization and ionization steps, leading to very simple spectral structure. The mass spectra of these compounds are EI‐like in nature, with clearly identified molecular ions and fragmentation patterns that are easily rationalized. The PB‐GDMS combination can be operated in a flow injection mode wherein the analyte is injected directly into the solvent flow, or can also be coupled to a high‐performance liquid chromatography (HPLC) system allowing LC/MS analysis of mixtures. Mass spectra obtained for nucleic acid bases, nucleosides, and nucleotides are readily obtained with injections of low‐nanomole quantities. Representative PB‐GDMS spectra for deoxy‐ and ribonucleosides, nucleotides, and mixed‐base oligonucleotides are presented to demonstrate the capabilities of the GD source. Characteristic fragmentation peaks from the spectra of adenine, cytosine, guanine, and thymine were identified in 22‐base sequences of single‐stranded DNA. The PB‐GD source is capable of producing spectra that may be used to identify the individual bases present in mixed‐base DNA and RNA fragments. Copyright © 2003 John Wiley & Sons, Ltd.
Combined infrared multiphoton dissociation and electron capture dissociation with a hollow electron beam in Fourier transform ion cyclotron resonance mass spectrometry
Authors: Tsybin Youri O. , Witt Matthias , Baykut Gökhan , Kjeldsen Frank , Håkansson Per 
Published: July 2003

AbstractAn electron injection system based on an indirectly heated ring‐shaped dispenser cathode has been developed and installed in a 7 Tesla Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. This new hardware design allows high‐rate electron capture dissociation (ECD) to be carried out by a hollow electron beam coaxial with the ion cyclotron resonance (ICR) trap. Infrared multiphoton dissociation (IRMPD) can also be performed with an on‐axis IR‐laser beam passing through a hole at the centre of the dispenser cathode. Electron and photon irradiation times of the order of 100 ms are required for efficient ECD and IRMPD, respectively. As ECD and IRMPD generate fragments of different types (mostly c, z and b, y, respectively), complementary structural information that improves the characterization of peptides and proteins by FTICR mass spectrometry can be obtained. The developed technique enables the consecutive or simultaneous use of the ECD and IRMPD methods within a single FTICR experimental sequence and on the same ensemble of trapped ions in multistage tandem (MS/MS/MS or MSn) mass spectrometry. Flexible changing between ECD and IRMPD should present advantages for the analysis of protein digests separated by liquid chromatography prior to FTICRMS. Furthermore, ion activation by either electron or laser irradiation prior to, as well as after, dissociation by IRMPD or ECD increases the efficiency of ion fragmentation, including the w‐type fragment ion formation, and improves sequencing of peptides with multiple disulfide bridges. The developed instrumental configuration is essential for combined ECD and IRMPD on FTICR mass spectrometers with limited access into the ICR trap. Copyright © 2003 John Wiley & Sons, Ltd.
Improved peptide sequencing using isotope information inherent in tandem mass spectra
Authors: Cannon William R. , Jarman Kenneth D. 
Published: July 2003

AbstractWe demonstrate here the use of natural isotopic ‘labels’ in peptides to aid in the identification of peptides with a de novo algorithm. Using data from ion trap tandem mass spectrometric (MS/MS) analysis of 102 tryptic peptides, we have analyzed multiple series of peaks within LCQ MS/MS spectra that ‘spell’ peptide sequences. Isotopic peaks from naturally abundant isotopes are particularly prominent even after peak centroiding on y‐ and b‐series ions and lead to increased confidence in the identification of the precursor peptides. Sequence analysis of the MS/MS data is accomplished by finding sequences and subsequences in a hierarchical manner within the spectra. Copyright © 2003 John Wiley & Sons, Ltd.
Electrospray mass spectrometry determination of poly(oxazolidine acetal)
Authors: Maślińska‐Solich J. , Kudrej‐Gibas E. 
Published: July 2003

AbstractThe polycondensation of terephthalaldehyde with 2‐amino‐2‐hydroxymethyl‐1,3‐propanediol (TRIS), or of terephthaldehyde with 2,2′‐(1,4‐phenylene)‐bis‐1,3‐(4,4‐dihydroxymethyl)oxazolidine (bis‐oxazolidine), using acidic catalysts, leads to the formation of linear polymers and macrocyclic compounds. The structure of the polymer was determined by 1H‐, 13C‐NMR spectroscopy and electrospray ionization mass spectrometry (ESI‐MS) analysis. ESI‐MS measurements were used to study the details of the polymer structure and support the alternating nature of equimolar amounts of oxazolidine and the cyclic acetal of terephthaldehyde in these macromolecules. Copyright © 2003 John Wiley & Sons, Ltd.
‘Bubble chamber model’ of fast atom bombardment induced processes
Authors: Kosevich Marina V. , Shelkovsky Vadim S. , Boryak Oleg A. , Orlov Vadim V. 
Published: July 2003

AbstractA hypothesis concerning FAB mechanisms, referred to as a ‘bubble chamber FAB model’, is proposed. This model can provide an answer to the long‐standing question as to how fragile biomolecules and weakly bound clusters can survive under high‐energy particle impact on liquids. The basis of this model is a simple estimation of saturated vapour pressure over the surface of liquids, which shows that all liquids ever tested by fast atom bombardment (FAB) and liquid secondary ion mass spectrometry (SIMS) were in the superheated state under the experimental conditions applied. The result of the interaction of the energetic particles with superheated liquids is known to be qualitatively different from that with equilibrium liquids. It consists of initiation of local boiling, i.e., in formation of vapour bubbles along the track of the energetic particle. This phenomenon has been extensively studied in the framework of nuclear physics and provides the basis for construction of the well‐known bubble chamber detectors. The possibility of occurrence of similar processes under FAB of superheated liquids substantiates a conceptual model of emission of secondary ions suggested by Vestal in 1983, which assumes formation of bubbles beneath the liquid surface, followed by their bursting accompanied by release of microdroplets and clusters as a necessary intermediate step for the creation of molecular ions. The main distinctive feature of the bubble chamber FAB model, proposed here, is that the bubbles are formed not in the space and time‐restricted impact‐excited zone, but in the nearby liquid as a ‘normal’ boiling event, which implies that the temperature both within the bubble and in the droplets emerging on its burst is practically the same as that of the bulk liquid sample. This concept can resolve the paradox of survival of intact biomolecules under FAB, since the part of the sample participating in the liquid–gas transition via the bubble mechanism has an ambient temperature which is not destructive for biomolecules. Another important feature of the model is that the timescale of bubble growth is no longer limited by the relaxation time of the excited zone (∼10−12 s), but rather resembles the timescale characteristic of common boiling, sufficient for multiple interactions of gas molecules and formation of clusters. Further, when the bubbles burst, microdroplets are released, which implies that FAB processes are similar to those in spraying techniques. Thus, two processes contribute to the ion production, namely, release of volatile solvent clusters from bubbles and of non‐volatile solute from sputtered droplets. This view reconciles contradictory views on the dominance of either gas‐phase or liquid‐phase effects in FAB. Some other effects, such as suppression of all other ions by surface‐active compounds, are consistent with the suggested model. Copyright © 2003 John Wiley & Sons, Ltd.