bluuebunny/crossref_metadata_2025_split huggingface dataset:
Negative electrospray ionization mass spectrometry analysis of gangliosides, sulphatides and cholesterol 3‐sulphate
Authors: Ghardashkhani S. , Gustavsson M. L. , Breimer M. E. , Larson G. , Samuelsson B. E. 
Published: May 2005

AbstractNegative electrospray ionization mass spectrometry (NESI‐MS) of a series of native gangliosides containing one, two or three sialic acid groups, sulphatide‐I and cholesterol 3‐sulphate was undertaken, using a magnetic sector instrument. The results show that NESI‐MS of gangliosides leads to the formation of multiple‐charged molecular ions of the type [M  H]−, [M  2H]2− and [M  3H]3−. The number of charges appears to be correlated to the number of sialic acid groups present. NESI‐MS of sulphatide‐I predominantly gave ions of type [M  H]− whilst cholesterol 3‐sulphate gave a more complex ionization pattern. The sensitivity of the NESI‐MS system was enhanced by using water+methanol, 9:1 (v/v) as solvent, containing 300 pmol/μL of NH4HCO3. The application of NESI‐MS to these compounds is discussed.
Fumonisin B1 analysis with capillary electrophoresis–electrospray ionization mass spectrometry
Authors: Hines Harry B , Brueggemann Ernst E. , Holcomb Manuel , Holder Claude L. 
Published: May 2005

AbstractFumonisin B1, a mycotoxin produced by a common fungal contaminant of corn, Fusarium moniliforme, was analyzed by capillary electrophoresis–electrospray ionization mass spectrometry. System performance was maximal with uncoated columns. System efficiencies of approximately 44 000 plates/m and reproducible analysis times of about 13 min were obtained. System efficiency with methyl‐coated columns was approximately 24 000 plates/m. Reproducible analysis times of about 3.5 min were obtained with these columns. With uncoated columns, the concentration limit of detection was 156 ppb with a s/n ratio of approximately 10. The estimated injected mass at 156 ppb was 1.1 pg. Repeated injections of extracts containing constant fumonisin B1 concentrations showed that peak areas were slightly inconsistent, although generally similar to variations encountered with liquid chromatography‐electrospray ionization mass spectrometry. The source of this inconsistency was traced to sample solubility, errors inherent in electrophoresis injections, and electrospray instability. Minimizing these problem areas will produce a technique with peak area reproducibilities comparable to liquid chromatography–electrospray ionization mass spectrometry, but with potentially greater resolving power.
A study of factors influencing the formation of singly charged oligomers and multiply charged monomers by matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Zhong Feng , Zhao Shankai 
Published: May 2005

AbstractThe formation of singly charged oligomers and multiply charged monomers has been studied under different conditions with matrix‐assisted laser desorption/ionization and it has been found that the concentration of analyte in matrix solution, as well as the matrix and substrate used, are factors that influence this process. The concentration of analyte in the matrix solution has a strong influence on the formation of singly charged oligomers. When α‐cyano‐4‐hydroxycinnamic acid is used as matrix, more doubly charged monomeric molecular ions are observed than when sinapinic acid is used. By using a nitrocellulose membrane instead of a silver plate as substrate, we find more multiply charged monomers and dimers in the spectra, especially in the case of high mass proteins, such as albumin. It seems that the formation of multiply charged monomers and oligomers is influenced by the overall amount of charge that the sample carries.
Isotope effects in the elimination of H and D atoms by dissociative charge transfer reactions in systems involving isotopic methanes
Authors: Ardelean Petru , Dunca Firuta , Cuna Cornel , Ioanoviciu Damaschin 
Published: May 2005

AbstractThe charge transfer reactions of H, CH, CH and N+ ions with CH4, CH3D, CH2D2 and CD4 were studied. The measurements were carried out using a tandem type mass spectrometer. The influence of the kinetic and internal energy of the incident ions was observed on the secondary mass spectra and also on the isotope effects expressed through πi(D/H), Ti(H) and Ti(D) factors. The dependence of the isotope effects on kinetic energy could indicate a conversion of kinetic energy into internal energy. Reactions in which momentum transfer resulted in charge transfer were also observed, probably indicating a ‘short‐range interaction’ reaction mechanism.
252Cf‐plasma desorption mass spectrometry analysis of lipids A obtained by an elimination reaction under mild conditions
Authors: Lebbar Souad , Karibian Doris , Haeffner‐Cavaillon Nicole , Beyec Yvon Le , Caroff Martine 
Published: May 2005

AbstractLipids A are the hydrophobic domains of bacterial endotoxic lipopolysaccharides. Since they are responsible for most of the biological activities (both pathogenic and beneficial) of endotoxins, the characterization of their structure is crucial to the understanding of their mode of action. However, the inadequacy of existing methods for preparing certain lipids A has prompted us to devise a new, mild procedure which gives intact products. Use was made of the special features of 252Cf‐plasma desorption mass spectrometry for forming molecular ions from these species and giving qualitative and quantitative information from the primary mass spectrum.
Fragmentation of a series of cyclic dipeptides in fast‐atom bombardment mass spectrometry
Authors: Henczi Maria , Weaver Donald F. 
Published: May 2005

AbstractThe positive‐ion mass spectra of a series of cyclic dipeptides have been obtained by fast‐atom bombardment mass spectrometry. The protonated molecules were mass selected and their collision‐induced dissociations were analysed by tandem mass spectrometry. This approach allowed an easy structural characterization of the above mentioned class of compounds for further pharmacological studies.
Chemical ionization and electron impact mass spectra of N‐carbonyldihydrazones of 2,4‐diacetylresorcinol
Authors: Kotali Antigoni 
Published: May 2005

AbstractThe methane chemical ionization mass spectra of N‐carbonyldihdrazones of 2,4‐diacetylresorcinol were recorded. The protonated molecular ion was found to be of variable abundance and was often accompanied by [M + 29]+ and [M + 41]+ ions. Electron impact mass spectra displayed weak molecular ions and were characterized by the scission of a NN bond and subsequent loss of XCONH and XCONHNH2.
Mass spectrometric study on two compounds from Skimmia caureola ssp. multinervia
Authors: He Meiyu , Zhang Hongjie , And Xiaoran He , Zhang Mingzhe 
Published: May 2005

AbstractThe mechanisms of the mass spectrometric fragmentation of two compounds, I (evoxine) and a new compound II (O‐methylcaureolol), were analyzed using mass‐analyzed ion kinetic energy spectrometry, and by verifying the elemental composition and structure of some important fragment ions by high‐resolution data. We discovered that the double bond in position 9,11 of the C ring of II may be diverted to position 7,8 of the B ring and that a typical retro‐Diels–Alder reaction follows.
Conformational properties of Rhodobacter capsulatus cytochrome c2 wild‐type and site‐directed mutants using hydrogen/deuterium exchange monitored by electrospray ionization mass spectrometry
Authors: Jaquinod Michel , Halgand Frederic , Caffrey Michael , Saint‐Pierre Christine , Gagnon Jean , Forest Eric , Fitch John , Cusanovich Michael 
Published: May 2005

AbstractThe conformational properties of Rhodobacter capsulatus cytochrome c2 wild‐type and two site‐directed mutants (glycine 34 replaced by serine and proline 35 replaced by alanine) were characterized by their charge state distributions and hydrogen/deuterium (H/D) exchange properties monitored by electrospray ionization mass spectrometry. The results suggest the presence of structural perturbations in the mutated cytochromes, an observation that is in agreement with their decreased conformational stabilities. In addition, a fast enzymatic procedure was developed to identify regions for which the H‐bonding or solvent accessibility properties were perturbed by the mutations. In this procedure, deuterated peptides were separated and analysed by using liquid chromatography directly coupled to the electrospray ionization source in order to minimize the occurrence of back‐exchange during analysis. In the case of G34S, mutational effects were found for peptides 1–26, 38–51, 52–59 and 109–116, which in the Rb. capsulatus cytochrome c2 structure correspond to extensive regions on the same side of the molecule as the proximal histidine, as well as part of the C‐terminal helix. In the case of P35A, mutational effects were found for peptides 1–26, 27–37, 38–51 and 52–59, which in the Rb. capsulatus cytochrome c2 stucture correspond to extensive regions on the same side of the molecule as the proximal histidine. We show that the present set of mass spectrometric experiments is useful as an initial characterization of mutant conformational properties because the analyses require only nanomole quantities of protein and can be performed rapidly.
Fragmentation reactions of Cu+‐cationated α‐amino acids
Authors: Wen Doreen , Yalcin Talat , Harrison Alex G. 
Published: May 2005

AbstractThe Cu+‐cationated species of 12 α‐amino acids have been prepared by fast‐atom bombardment and the unimolecular (metastable ion) fragmentation reactions have been examined by tandem mass spectrometry. The major unimolecular fragmentation reactions observed involve elimination of H2O, elimination of CO2 and elimination of CH2O2. In addition, for Cu+‐cationated asparagine and glutamine, elimination of NH3 is a significant reaction and for Cu+‐cationated proline, elimination of H2 is a major fragmentation reaction. It is concluded that there are three pathways to elimination of (H2, C, O2), direct elimination of CH2O2, direct elimination of (H2O+CO) and elimination of (CO2+H2).
Proton affinity and heat of formation of vinylimine CH2CHCHNH
Authors: Bouchoux Guy , Salpin Jean‐Yves , Leblanc Danielle , Alcaraz Christian , Dutuit Odile , Palm Hartmut 
Published: May 2005

AbstractThe vinylimmonium cation [CH2CHCHNH2]+, [1H]+, originating from cyclopentylamine has been studied by photoionization, ion cyclotron resonance mass spectrometry and ab initio molecular orbital calculations. A heat of formation, ΔH[CH2CHCHNH2]+ of 747±7 kJ/mol has been deduced from photoionization experiments, after correction for the thermal energy of the precursor molecules. The proton affinity of vinylimine, CH2  CHCHNH, 1, (PA(1) = 908±4kJ/mol) has been deduced from proton exchange experiments using the ‘bracketing’ technique. This latter, combined with the previously determined ΔH[CH2CHCHNH2]+ leads to ΔH(CH2CHCHNH)=125kJ/mol with a possible error of ±11 kJ/mol. Molecular orbital calculations, conducted at the MP2/6‐311 ++G**//MP2/6‐31G* + ZPE level, lead to comparable estimates ΔH(CH2  CHCHNH2)+ = 746kJ/mol and ΔH(CH2CHCHNH) = 128–135 (kJ/mol).
Modulation of the gas‐phase reactivity of W+ by carbonyl ligands: Activation of hydrocarbons by W(CO) (x=1–4)
Authors: Mourgues Philippe , Ohanessian Gilles 
Published: May 2005

AbstractThe gas‐phase reactions of W(CO) (x=1–4) with methane, ethane, propane, ethene and propene have been studied in a Fourier transform ion cyclotron resonance mass spectrometer. Virtually all reactions observed involve hydrocarbon dehydrogenation, either single or double, a reactivity similar in type to what is observed with bare W+. The most reactive ion is W(CO) except for this ion, reactivity tends to diminish with increasing number of carbonyl ligands. Whenever there is sufficient internal energy available, CO detachment competes with H2 loss. This is the case for ethene and propene, and in some cases with propane. However, this is strongly dependent upon the number of carbonyl ligands in the reacting ion. In most cases, product ions are themselves reactive with the neutral, leading to reaction sequences of various lengths. These sequences end either because the metal no longer has the appropriate number of non‐bonding electrons for inserting into a CH bond with low activation energy, or because of saturation of the coordination shell around the metal.
Time focusing magnetic wedge‐field sectors for time‐resolved ion momentum spectrometry
Authors: Ioanoviciu Damaschin , Cuna Cornel , Erdélyi BéLa , Yavor Michail I. 
Published: May 2005

AbstractThe time‐of‐flight properties of magnetic wedge‐field sectors have been derived in a second‐order approximation. The following quantities were included: source slit width, radial and axial opening angles of the ion beam and relative energy spread. The transfer matrix elements of the time‐of‐flight (longitudinal) row were derived in terms of the initial and final angles and of K‐parameter dependence on the ion momentum and magnetic field. The longitudinal mass dispersion coefficient required in the time resolution formula was derived. The time‐of‐flight ion optical properties of a 60° symmetric, homogeneous magnetic sector mass spectrometer, already employed for time‐resolved ion momentum spectrometry studies, were compared with those of a wedge‐field, 180° deflecting stigmatic arrangement with K=0.7423. The time‐of‐flight aberrations were calculated from transfer matrix multiplications. The advantages of the wedge‐field geometry are: independence, up to second order, of the ion packet length upon the ion source slit width, independence to first order of the ion energy spread and stigmatic focusing in space. These factors ensure both improved sensitivity and time resolution.
A simple method for differentiating Leu and Ile in peptides. The negative‐ion mass spectra of [M  h]− ions of phenylthiohydantoin Leu and Ile
Authors: Ramsay Steven L. , Steinborner Simon T. , Waugh Russell J. , Dua Suresh , Bowie John H. 
Published: May 2005

AbstractPhenylthiohydantoin (PTH) amino acid derivatives are formed during sequential Edman degradation of peptides and proteins. Isomeric Leu and Ile (which differ only in respectively having iso‐butyl and sec‐butyl chains, and are often difficult to distinguish by conventional mass spectrometric techniques) may be readily identified by the characteristic decompositions of the [M  H]− ions of their PTH derivatives. The Leu spectrum shows major loss of propane, while that of the Ile derivative shows elimination of both methane and ethane. This method may be used routinely with 10 μg quantities of peptide material.
Quantification of 7‐dehydrocholesterol in plasma and amniotic fluid by liquid chromatography/particle beam‐mass spectrometry as a biochemical diagnostic marker for the smith‐lemli‐opitz syndrome
Authors: Sattler Wolfgang , Kostner Gerhard M. , Malle Ernst , Leis Hans‐JÖRg 
Published: May 2005

AbstractThe qualitative and quantitative determination of cholesterol and 7‐dehydrocholesterol (7‐DHC) in plasma as a biochemical diagnostic marker for the Smith‐Lemli‐Opitz syndrome by liquid chromatography/particle beam interface‐mass Spectrometry (LC/PB‐MS) is presented. Baseline separation of cholesterol arid 7‐DHC is achieved on a silica column with hexane + ethanol (99:1 v/v) as mobile phase within a 10 min analysis. Recoveries of cholesterol and 7‐DHC in a simple two‐phase extraction system are nearly 100%. The absolute limit of detection using LC/PB‐MS is ≈10 ng. The method presented allows extraction, analysis and quantification of cholesterol and 7‐DHC within 15 min without the necessity of sample derivatization.
Mass spectrometry of derivatives of dicyclopentadienyltitanium dichloride II. Comparison of chemical ionization and liquid secondary ion mass spectrometric behaviour
Authors: Wang Fu , Fang Ming , Wu Wannian , Chen Xuehua , Huang Jielin 
Published: May 2005

AbstractPositive/negative chemical ionization (PI/NI CI) and liquid secondary ion mass spectrometry (LSIMS) of ten derivatives of dicyclopentadienyltitanium (IV) dichloride were investigated. The major ions detected were M + NHU4, M − CI]+, [M − 2Cl]+, [M − R1CpR3]+ and [M − R2CpR4]+ in PICI (ammonia) mass spectra, M−, [M + CI]−, [M − CI]−, [M + CI − R1CpR3]+ and [M + CI − R1CpR3]+ in NICI (ammonia) mass spectra, and [M − CI]+, [M − 2CI]+, [M − 2CI + (NBA − H)]+ (where NBA = m‐nitrobenzyl alcohol), [M − R1CpR3]+, [M − R2CpR4+, [M − R1CpR3 − HCI]+ and [M − R2CpR4 − HCI]+ (where R1CpR3 and R2CpR4 are both mixed alkyl‐aryl substituted cyclopentadienyl groups) in LSIMS. Although the mass spectrometric behaviours are quite different due to the different ionization mode, adduct ions were observed in all mass spectra and molecular ions were only observed in NICI mass spectra. The cleavage pathways were confirmed using tandem mass spectrometry methods.
Ion dissociation reactions induced in a high‐pressure quadrupole collision cell
Authors: Whalen Kevin , Grossert J. Stuart , Boyd Robert K. 
Published: May 2005

AbstractThis work concerns a new high‐pressure quadrupole collision cell, designed for tripie‐quadrupole mass spectrometers. This new collision cell operates at pressures up to 10 mTorr, an order of magnitude higher than conventional cells of this type. Previous investigations have concentrated upon the significant increases in transmission efficiency and in resolving power for fragment ions which result from the use of this new design. The present work reports an investigation into the nature of the dissociation reactions which can be induced by collisions in this high‐pressure cell. Charge‐site‐remote fragmentations of a simple precursor ion were chosen as a test case, and were found to be observable at laboratory collision energies lower by a factor of 4–5 than those found previously to be necessary when using conventional low‐pressure quadrupole collision cells. It was also shown that the charge‐site‐remote reactions were accompanied by the mixed‐site‐fragmentation reactions described by Tuinman and Cook (J. Am. Soc. Mass Spectrom). Vol. 1, p. 85 (1989). Ionization of collision gas was observed in the case of xenon. Efforts to observe charge‐site‐remote fragmentations of peptide ions were marginally successful. Highly basic peptides, which have been problematic for sequencing by low‐energy tandem mass spectrometry, did not yield useful fragment‐ion spectra in the new cell. The fragmentation behaviour of protonated Leu‐enkephalin, for which fragmentation pathways have been thoroughly studied previously, suggested that the observed spectra reflected integration of the fragmentation kinetics over a considerably longer time, thus involving many more reaction steps. These combined observations are considered in terms of a qualitative model based on a rapid decrease of ion kinetic energy during passage through the cell, with much longer residence times than for conventional quadrupole cells.
An improved method for clenbuterol screening using high resolution selected ion recording
Authors: Kingston R. , Ordsmith N. , Williams E. , Thieme D. 
Published: May 2005

AbstractA method has been developed using reliable GC derivatization techniques interfaced with a high resolution mass spectrometer. The method has proved successful for the detection of low levels (less than 1 ppm) of clenbuterol in complex biological matrices. Selected ion recording of two characteristic isotopic fragment ions provides a specific mode of detection by verifying the GC retention time of these ions and also by comparing their relative abundance. Analysis of urine samples demands higher mass spectrometric resolution, and 40000 (10% valley) was found to be a prerequisite for accurate integration of the drug‐related chromatographic peaks. The method developed is suitable for adaptation to a completely unattended automated routine incorporating sample injection, storage and retrieval of source tuning parameters, and data processing.
The characterization of the metabolites of ranolazine in man by liquid chromatography mass spectrometry
Authors: Penman A. D. , Eadie J. , Herron W. J. , Reilly M. A. , Rush W. R. , Liu Y. 
Published: May 2005

AbstractThe metabolism of ranolazine (RS‐43285) or (+)N‐(2,6‐dimethylphenyl)‐4‐[2‐hydroxy‐3‐(2‐methoxyphenoxy)‐propyl]‐1‐piperazine acetamide dihydrochloride was investigated in man using plasma samples obtained from four different clinical studies. The metabolite profiles following single and multiple doses of 342 mg instant release (IR) ranolazine, following multiple doses of 1000 mg sustained release (SR) ranolazine and following dosing with both ranolazine (IR) and a potentially co‐administered drug, diltiazem, were compared. Metabolism of ranolazine in man was shown by LC/MS analysis to be extensive with up to seven primary routes of metabolism identified. N‐dealkylation by hydrolysis at the piperazine ring produced three metabolites whilst O‐demethylation and O‐dearylation at the methoxyphenoxy moiety produced a further two compounds. Additionally, hydrolysis of the amide group formed one other species. Oxygenation at various points in the molecule produced a further four metabolites. Direct conjugation of ranolazine with glucuronic acid and with an uncharacterized adduct were also identified as a route of elimination. Ten other biotransformation products were formed as a result of multiple metabolic steps. Conjugation was also associated with the desmethyl metabolite (glucuronide and unidentified conjugates) of hydroxylated ranolazine. In a previous publication (Journal of Chromatography, 1995, accepted for publication) semi‐quantitative analyses of pooled plasma from the study where ranolazine was dosed at 1000 mg twice daily showed that of the twelve metabolites studied only four accounted for AUC's in excess of 10% of the ranolazine AUC.
A reconciliation of mass ranges from matrix‐assisted laser desorption/ionization mass spectrometry and size exclusion chromatography for coal‐derived materials
Authors: Herod Alan A. , Kandiyoti Rafael , Johnson Barry R. , Bartle Keith D. , Carter David M. , Cocksedge Mike J. , Domin Mark 
Published: May 2005

AbstractSize exclusion chromatography (SEC) has been used extensively in the characterization of coal‐derived liquids to estimate molecular masses (MM), indicating the presence of considerably greater upper mass ranges compared to mass spectrometric methods based on heated probes and field ionization. In the present study, the use of tetrahydrofuran (THF), a solvent commonly used in SEC, has been shown to lead to partial loss of sample on column packings and to allow some separation by an adsorption mechanism rather than by size exclusion. In this paper, we have compared these results with data from SEC, where 1‐methyl 2‐pyrrolidinone was used as the mobile phase, indicating that the largest molecules (not observed in THF‐based work) appear at the exclusion limit, with a continuum of material down to the total permeation limit of the column. In terms of polystyrene standard masses, this is equivalent to a range from 100 u, at the lower limit, up to in excess of 30–40 000 u and possibly over 2 000 000 u. Our results from SEC in NMP suggest that limitations exist in much solution‐based work attempting to identify distributions of MMs in coal‐derived liquids. Matrix‐assisted laser desorption/ionization (MALDI) spectra of the fractions show similar features to those seen by SEC in NMP, with a continuum from high to low mass, and a significant shift to higher mass in the insoluble fraction compared with the soluble fraction. The new data are in line with observations by laser desorption mass spectrometry (LD‐MS) and MALDI‐MS, which have shown much greater upper‐MM limits than either SEC (in THF) or mass spectrometric techniques relying on thermal evaporation of coal‐derived materials from heated probes. The work would appear to have implications for other polydispersed natural polymer systems.