bluuebunny/crossref_metadata_2025_split huggingface dataset:
Negative‐ion fast atom bombardment mass spectrometry of N‐phosphoamino acids
Authors: Yin Ying‐Wu , Ma Yuan , Zhao Yu‐Fen , Xin Bing , Wang Guang‐Hui 
Published: May 2005

AbstractThe fragmentation patterns of N‐phosphoamino acids in negative‐ion fast atom bombardment mass spectrometry (FABMS) showed different characteristics to those in positive‐ion FABMS. Six typical N‐diisopropyloxyphorphorylamino acids all had intense [M − 1]− peaks, and they underwent similar fragmentation pathways. In general, the elimination of one alkene molecule followed by the loss of one molecule of alcohol occurred. They also favoured an N → O rearrangement reaction, followed by fragmentation to (RO)2 PO2− and (RO) (HO)PO2−.
Evaluation of the dipole moments of organic ions in the gas phase
Authors: Bortolini O. , Olimpieri L. , Traldi P. 
Published: May 2005

AbstractThe dipole moments of a series of substituted benzene radical cations were evaluated on the basis of mass displacements from the expected instrumental value by ion trap experiments. Mass displacements represent a direct measure of the total polarizability, giving access to both the electronic and dipolar polarizabilities, depending on the characteristics of the analyte under investigation. A linear relationship was found between the dipolar polarizabilities and the dipole moments of the corresponding neutrals.
Electron impact‐induced fragmentation of 2,3‐dihydro‐1,5‐benzothiazepin‐4(5H)‐ones
Authors: Pócsfalvi Gabriella , Lévai Albert , Dinya Zoltán , Somogyi Árpád , Vékey Károly 
Published: May 2005

AbstractThe electron impact‐induced fragmentations of 2,3‐dihydro‐1,5‐benzothiazepin‐4(5H)‐ones and some related compounds were investigated. On the basis of low‐ and high‐resolution measurements, metastable ion studies by means of mass‐analysed ion kinetic energy spectroscopy and collision‐induced dissociation experiments, the main fragmentation pathways were established. The effect of methyl and phenyl substituents at the C(2) and C(3) positions of the heterocyclic ring on the fragmentations was also studied. The (1,3) ring splitting was investigated in some detail, using semi‐empirical molecular orbital calculations.
Mass spectral characterization of 3,4,6‐tri‐O‐benzyl‐β‐C‐glucopyranosides containing XC6H4S substituents of C(2)
Authors: Rozynov B. V. , Liukkonen R. J. , Carlson R. M. , Kuehl D. W. , Smoliakova I. P. , Caple R. , Kuehl C. J. , Smit W. A. 
Published: May 2005

AbstractElectron impact mass spectra (70 eV) were generated for tri‐O‐benzyl‐D‐glucal and six XC6H5S substituted 3,4,6‐tri‐O‐benzyl‐β‐C‐glucosides which had been modified at C(2) by the introduction of an XC6H4S fragment (where X = CH3 or CI) in an effort to understand better fragmentation processes for the structural characterization of this important class of compounds. The model compounds which were synthesized were glucoside derivatives of CH2CHO, C(CH3)2CHO, , C6H5 and CN. For all O‐benzylated compounds, the benzyl moiety was the base ion; however, the molecule ion of each modified glucoside was significantly abundant. A characteristic feature of S‐containing C‐glucosides was an abundant CH3C6H5SCHCHCH2 ion at m/z 163. Fragmentation of these C‐glucosides was interpreted in terms of positive charge localization on the molecule ion according to rules for normal carbohydrates. Knowledge of the fragmentation on the S‐containing C‐glucosides should be useful for the characterization of additional new analogues.
Differentiation and electron ionization‐induced isomerization of 4,5‐Bis(alkylthio)‐1,3‐dithiole‐2‐thiones and 1,2‐dithiole‐3‐thiones
Authors: Andreu R. , Gayán I. , Garín J. , Orduna J. , Savirón M. 
Published: May 2005

AbstractThe electron impact ionization mass spectra of 4,5‐bis(alkylthio)‐1,3‐dithiole‐2‐thiones and their 1,2‐dithiole‐3‐thione isomers were studied by accurate mass measurements and linked scans. The relative abundance of ions formed following the extrusion of S2, CS or CS2 allows an unambiguous isomer differentiation. Isomerization of molecular ions was studied by means of metastable ion analysis and collision‐induced dissociation. The order of reactivity was analogous to that observed in isomerization under photochemical conditions.
Metastable ion studies: Ethyl(methoxy)(chloro)silanes
Authors: Hagen Arnulf P. , Hodge Shelly J. , Randolph Bruce B. , Laing John L. 
Published: May 2005

AbstractMetastable ion scanning was used to investigate the fragmentation patterns of ethyl(trimethoxy)silane, ethyl(dimethoxy)chlorosilane and ethyl(methoxy)dichlorosilane, their deuterated counterparts and ethyltrichlorosilane. For these compounds the molecule ion has a low abundance using 70 eV electron impact ionization. In all cases the base peak corresponds to the loss of neutral C2H5. When chemical ionization is employed with isobutane, usable peaks representative of the molecule ions are observed.
Mass spectrometry of N‐substituted amino acids and their derivatives: Correlation of the abundances of the M+. and selected fragment ions of metamers
Authors: Wyrzykiewicz E. , Prukala D. 
Published: May 2005

AbstractThe mass spectral fragmentations of nineteen new metameric N‐(E)‐stilbenyloxyalkylcarbonyl‐ [or (E)‐(4′‐chlorostilbenyloxyalkylcarbonyl)]‐substituted amino acids and their metameric methyl esters and hydrazides were investigated. Fragmentation pathways are proposed on the basis of accurate mass and metastable transition measurements. The correlation between the intensities of M+. and the selected fragment ions of these compounds is discussed. The data obtained create the basis for distinguishing metamers.
Mass spectra of n‐butylboronate ester derivatives of the major metabolite of prostaglandin F
Authors: Ferretti Aldo , Flanagan Vincent P. , Roman John M. 
Published: May 2005

AbstractThe EI mass spectra of six n‐butylboronate ester derivatives of the major metabolite of prostaglandins F1α and F2α (PGF‐M) are presented and discussed. Proposed ion assignments and fragmentation pathways are based on substituent shifts, on data from a deuterium‐labeled methoxime derivative and on the analysis of collision‐induced dissociation spectra of selected ions. Fragment ions suitable for identification and quantification of PGF‐M in a biological matrix and diagnostically valuable ions for structure recognition are proposed.
Evidence for the existence of phosphoazonium (iminophosphenium) and arsenoazonium ions in the gas phase by mass spectrometry
Authors: Curtis Jonathan M. , Burford Neil , Parks Trenton M. 
Published: May 2005

AbstractThe first evidence for the existence of the methylphosphoazonium (methyliminophosphenium) ion CH3NP+ and the methylarsenoazonium ion (named in this work) CH3NAs+ (analogues of the methyldiazonium ion CH3NN+) is provided using electron impact mass spectrometry The ions are formed as fragment ions of some highly air‐sensitive phospholidinium and arsolidinium compounds that contain dicoordinate P and As centres. A combination of high‐resolution mass measurements and high‐ and low‐energy tandem mass spectra (fragment ion scans) suggest that the ions have NC bonds rather than the isomeric azophosphonium (CH3PN+) or azoarsenonium (CH3AsN+) forms.
Accurate mass measurements of positive ions in the desorption chemical ionization mode
Authors: Pergantis S. A. , Emond C. A. , Madilao L. L. , Eigendorf G. K. 
Published: May 2005

AbstractDesorption chemical ionization mass spectrometry employing ammonia as the reagent gas has been extensively used to obtain molecular mass and structural information on a wide variety of compounds. Mass‐deficient reference standards normally used for calibration purposes in mass spectrometry do not provide adequate mass spectra under ammonia chemical ionization conditions. In order to overcome this problem a mixture of ammonia and methane as reagent gases was employed. In high‐resolution accurate mass measurement experiments, this gas mixture allows the simultaneous detection of mass spectra of perfluorokerosene adequate for calibration purposes and spectra containing molecular mass information of the analyte. A needle valve system was used to control the composition of the gas mixture introduced into the ion source. For positive‐ion accurate mass measurements of higher masses (up to m/z = 2300), Fomblin 18/8 oil was successfully used as a reference standard under ammonia, methane and isobutane desorption chemical ionization conditions.
Collision gas effects in the collision‐induced decomposition of protonated and cationized molecules of carbohydrate antibiotics
Authors: Florencio M. Helena , Despeyroux Dominique , Jennings Keith R 
Published: May 2005

AbstractThe collision‐induced decomposition (CID) mass spectra of the protonated and cationized molecules of a number of carbohydrate antibiotics of RMM ranging from 700 to 1500 were studied by means of a four‐sector mass spectrometer with a floated collision cell. Helium and argon were used as collision gases. This work illustrates that cationized rather than protonated carbohydrate antibiotics give an increased yield of high‐mass ions of diagnostic value. Further, when helium is replaced by argon as collision gas, differences in the CID spectra of MH+ ions become apparent only for molecules of RMM > 1400 whereas for [M + Na]+ ions differences are observed for molecules of RMM as low as 1000. These results have been attributed to the deposition of more internal energy in the precursor ion when argon is used, resulting in increased fragmentation.
Differentiation of diastereomeric chlorin derivatives by fast atom bombardment mass spectrometry
Authors: Schulze Peter , Kusch Dirk , Meier Axel , Montforts Franz‐Peter 
Published: May 2005

AbstractThe stereochemistry of six pairs of diastereomeric chlorin derivatives was investigated by electron impact (EI), fast atom bombardment (FAB) and direct chemical ionization DCI mass spectrometry. It was demonstrated that FAB and EI mass spectrometry are convenient and rapid methods for distinguishing between diastereomeric chlorin derivatives due to their different fragmentation patterns.
Collisional‐activated decomposition of benzyloxycarbonyl‐protected tripeptide derivatives containing proline in fast atom bombardment mass spectrometry
Authors: Tsunematsu Hideaki , Yamamoto Magobei , Isobe Ryuichi 
Published: May 2005

AbstractThe effect on the fragmentations of N‐benzyloxycarbonyl‐protected tripeptide ethyl esters due to the existence of L‐proline in the gas phase was examined by the collisional‐activated decomposition of the deprotonated molecule and the fragment ions produced by the cleavage of the tripeptide derivatives containing the neutral amino acids (L‐alanine, L‐leucine and L‐phenylalanine) and L‐proline, in which changes in both the numbers and positions of the prolyl residues were observed, in negative‐ion fast atom bombardment mass spectrometry. The cleavage patterns of these ions in the collisional‐activated decomposition mass spectra were observed to depend on the numbers and positions of prolyl residues in the peptide derivatives. These results indicate that the conformational differences in the peptide derivatives due to the existence of L‐proline affect the decomposition of the ions containing the neutral amino acids in the gas phase.
A mass spectrometric investigation on some 3‐[2‐(Nitroxy)alkyl]‐2H‐1,3‐benzoxazin‐4‐(3H)‐one derivatives
Authors: Rizzi Emanuele , Ferrario Francesco , Sala Alberto , Favretto Donata , Catinella Silvia , Traldi Pietro 
Published: May 2005

AbstractThe electron ionization mass spectrometric behaviour of ten 3‐[2‐(nitroxy)alkyl]‐2H‐1,3‐benzoxazin‐4‐(3H)‐one derivatives has been studied by means of metastable ion studies. By mass‐analysed ion kinetic energy spectrometry of the related molecular ions, clear differences have been evidenced between the 5‐methyl derivative and the other compounds, consisting of a highly favoured loss of NO2 radical. The same methodology has allowed easy characterization of isomeric compounds.
On the gas‐phase reaction of C3O2+. with C3O2
Authors: Pandolfo L. , Paiaro G. , Somogyi À. , Catinella S. , Traldi P. 
Published: May 2005

AbstractThe gas‐phase, ion molecule reaction between C3O2+. and C3O2 has been studied by both double‐focusing and ion trap mass spectrometry, rationalized by the formation of a dimeric, odd electron cation [C6O4]+. which decomposes extensively through sequential CO losses giving rise to [C5O3]+. and [C4O2]+. ions. The thermodynamics of this process have been investigated by means of ab initio calculation performed on the above species using different basis sets (STO‐3G, 3‐21G and 6‐31G*).
Proximity effects in mass spectrometry. Electron impact ionization‐induced cyclization of 1,2‐bis(1,4‐dithiafulven‐6‐yl)benzenes
Authors: Frère P. , Gorgues A. , Garín J. , Orduna J. 
Published: May 2005

AbstractThe electron impact ionization mass spectra of o‐, m‐ and p‐bis(1,4‐dithiafulven‐6‐yl)benzenes were studied by means of accurate mass measurements, metastable analysis and collision‐induced dissociation. Differences observed in the spectra of the ortho isomers are due to a cyclization reaction leading to molecular ions with the same structure as those generated from certain cyclic compounds, as confirmed by comparison of linked scans at constant B/E of metastable and collisionally activated molecular ions. Parallels of this cyclization of molecular ions with their electrochemical or acid‐induced isomerization are also discussed.
Gas chromatographic/mass spectrometric determination of vinyl acetate levels in air
Authors: Sturaro Alberto , Parvoli Giorgio , Doretti Lucio , Bancomina Cristina , Neonato Carlo 
Published: May 2005

AbstractThe determination of vinyl acetate at parts per 109 by volume (ppbv) levels in air by gas chromatography/mass spectrometry (GC/MS) was achieved by optimizing the GC conditions and choosing specific extraction solvents that are sufficiently pure. The ideal solvent should not give rise to fragment ions at m/z 43, in order to rule out any possible interference during the monitoring of the same vinyl acetate ion. Traces of acetone and butan‐2‐one in solvents suitable for this GC/MS determination may also mislead the detection of vinyl acetate. A 440 μl volume of a mixture of tetrachloroethylene containing 9% acetonitrile allowed the recovery of more than 90% of the ester with a detection limit of 1.5 ppbv in air together with a good linearity of response.
Potential of electrospray mass spectrometry for structural studies of O‐Glycoamino acids and ‐peptides with multiple α2,6‐Sialosyl‐Tn glycosylation
Authors: Peter‐Katalinić J. , Ashcroft A. , Green B. , Hanisch F.‐G. , Nakahara Y. , Ilijima H. , Ogawa T. 
Published: May 2005

AbstractNon‐derivatized O‐glycosylated amino acids and peptides with multiple glycosylation yield molecular and fragment ions on electrospray ionization. Synthetic substrates were used to demonstrate the fragmentation behaviour of the sugar moiety in positive‐ and negative ion electrospray mass spectrometry (ESMS) at low and high skimmer potentials. The ion sensitivity is higher compared than when using fast atom bombardment desorption. The potential of ESMS for the sequencing of O‐glycans is discussed.
Structure determination of phosphoinositol oligosaccharides from parasitic protozoa using fast atom bombardment mass spectrometry
Authors: Wait Robin , Jones Christopher , Routier Françoise H. , Previato José Osvaldo , Mendonça‐Previato Lucia 
Published: May 2005

AbstractGlycosylphosphatidylinositols (GPIs) are widely distributed membrane constituents of protozoa and higher eukaryotes, where they anchor proteins and other macromolecules to the cell surface. Free glycosylinositol phospholipids (i.e. not attached to protein or polysaccharide) have also been detected in some parasitic protozoa, and are thought play a role in the interaction of parasite and host. This paper describes the fast atom bombardment mass spectrometry (FABMS) of glycosylinositol phospholipids from the Trypanosomatid parasites Leptomonas samueli, Endotrypanum schaudinni and Leishmania adleri. FABMS in the positive‐and negative‐ion modes in conjunction with collisional activation permits the rapid determination of the monosaccharide composition, the sequence of residues, the branching pattern and the nature and location of non‐carbohydrate substituents. When supplemented by high‐field NMR, FABMS provides a highly efficient route to the complete structure elucidation of these materials.
Structure analysis of branched oligosaccharides using post‐source decay in matrix‐assisted laser desorption ionization mass spectrometry
Authors: Spengler Bernhard , Kirsch Dieter , Kaufmann Raimund , Lemoine Jérôme 
Published: May 2005

AbstractPost‐source decay matrix‐assisted laser desorption ionization (PSD‐MALDI) of sodium ion‐attached branched oligosaccharides derived from glycoproteins was demonstrated as a method of structure analysis by reflectron time‐of‐flight (TOF) mass spectrometry. Mono‐, di‐ and triantennary structures were investigated. The fragmentation patterns of these (structurally related) substances as obtained in the positive‐ion mode showed characteristic differences correlated with branching sites and linkage positions. Two‐bond ring cleavages as known from fast atom bombardment/collision‐induced dissociation and IR laser desorption mass spectrometry were also observed. Internal fragment ions formed by up to four consecutive cleavages were obtained with high intensity, allowing the branching structure of complex carbohydrates to be identified. PSD‐MALDI of oligosaccharides is characterized by high sensitivity, very good signal‐to‐noise ratios and high reproducibility of fragmentation patterns and signal intensities.
Mechanics of intraply hybrid composites—properties, analysis, and design
Authors: Chamis C. C. , Sinclair J. H. 
Published: May 2005

AbstractA mechanics theory is developed for predicting the physical thermal, hygral, and mechanical properties (including various strengths) of unidirectional intraply hybrid composites (UIHC) based on unidirectional properties of the constituent composites. Procedures are described which can use this theory in conjunction with composite mechanics computer codes and general purpose structural analysis finite element programs for the analysis/design of structural components made from intraply hybrid angleplied laminates (IHAL). Comparisons with limited data show that this theory predicts mechanical properties of UIHC and flexural stiffnesses of IHAL which are in good agreement with experimental data. The theory developed herein makes it possible to design and optimize structural components from IHAL based on a large class of available constituent fibers.
Syntatic foam pultrusion
Authors: Kwok F. T. , Wooddhams R. T. 
Published: May 2005

AbstractA simple circular pultruded rod was used to evaluate the mechanical and economic performance of four commercially available hollow spherical fillers (microbubbes). The incorporation of such glass or silicate microbubbes in a pultruded rod produced a decrease in density, strength and modulus. However, the loss of strength and modulus was more than compensated for by the decrease in density so that a 50 percent material cost saving was possible without any sacrifice in flexural or torsional properties. Thus for simple profile (rods, bars. Panels) the use of hollow spherical fillers can be economically advantageous in reducing material costs. The syntactic pultrusions posses many of the desirable properties of wood such as toughess, low density, high strength and stiffness plus the ability to accommodate nails and screws. The operating conditions of the pultruder wee normal with the exception that half as much force was needed on the puller and the pultruder would only operate satisfactorily when the resin/glass fiber/microbubble concertrations were within specified boundaries. Pyrex type glass bubbles were found to be less prone to damage during processing and performed better than silicate type microbubbles.
Stress intensity factor measurements in composite laminates with various notch configurations
Authors: Roman I. , Harel H. , Marom G. 
Published: May 2005

AbstractK‐calibration procedures were performed with a glass fiber‐reinforced epoxy angleply plate, a skin a sandwich structure. Different K‐calibration functions were obtained for various notch tip relative locations within the composite. In view of these observations and of the previously seen anisotropy of those functions it was concluded that the selection of an appropriate K‐calibration function depends on both the reinforcement geometry and on the notch tip location.
Evaluation of structural changes in epoxy systems by moisture sorption‐desorption and dynamic mechanical studies
Authors: Mikols W. J. , Seferis J. C. , Apicella A. , Nicolais L. 
Published: May 2005

AbstractThis work forms a basis for relating moisture solubilities and dynamic mechanical properties to the hygrothermal history of epoxy systems. Two different classes of epoxy systems were investigated; a low‐performance epoxy (DGEBA‐TETA) and a high‐performance system (TGDDM‐DDS) commonly used in carbon fiber composites. An increase in the equilibrium moisture content from TGDDM‐DDS epoxy samples having various DDS compositions was observed as a result of thermal cycling in a liquid environment. Interpretation of the experimental results suggest that hygrothermal interactions produce changes in the epoxy network structure and result in the observed moisture sorption behavior.
Elastic properties of intermingled hybrid composites
Authors: Gruber M. B. , Chou T. 
Published: May 2005

AbstractThe combination of different types of fibers in a common matrix, known as a hybrid composite, has the potential of achieving a balance between composite strength and ductility, as well as a more cost‐effective use of expensive fibers, not re‐alized in a single‐fiber compostie. The elastic properties of a continuous Kevlar®/glass intermingled hybrid composite have been investigated. Theoretical predictions utilizing a self‐consistent model and a bound approach are compared to the influence of the relative Kevlar®/glass fiber volume fraction on the elasstic material properties.
Studies of the simulation of silane coupling agent structures on particulate fillers; the pH effect
Authors: Miller James D. , Hoh Ka‐pi , Ishida Hatsuo 
Published: May 2005

AbstractThe molecular structure of γ‐methacryloxypropyltrimethoxysilane (γ‐MPS) deposited on the surfaces of particulate mineral fillers was modeled by adjusting the pH of an aqueous alcoholic solution of the silane in absence of a substrate. Hydrolyzates obtained from the solution were studied by gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FT‐IR) and found to be polymethacryloxypropylsilsesquioxanes whose configuration and molecular‐weight distribution were dependent on the solution pH. In acidic environments (below pH 4) the polycondensation mechanism appeared to proceed in a selective manner to form polycyclic blocks which resemble a beaded chain following condensation between blocks. Under more neutral and basic conditions (at or above pH 4) the polycondensation mechanism, resulted in polymethacryloxypropylsilsesquioxanes with the more equilibrated double chain ladder configuration. The molecular weight distribution of these structures was dependent on the stability of the silanol or the silanolate ion. Extremely high‐molecular‐weight and polydisperse polymethacryloxypropylsilsesquioxanes were generated at near neutral pH due to the formation of the double chain ladder configuration and the high silanol instability in this pH range. The two different polymethacryloxypropylsilsesquioxane configurations were also observed on γ‐MPS modified metal oxide substrates. The structures help explain some of the previously observed trends with respect to γ‐MPS adsorption on particulate mineral fillers. In strongly basic environments the methacrylate function of γ‐MPS partially hydrolyzes to form sodium carboxylate, and carbon dioxide is absorbed from the air and reacts to form sodium carbonate.