bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accurate mass measurement of proteins using electrospray ionization on a magnetic sector instrument
Authors: McEwen C. N. , Larsen R. S. 
Published: May 2005

AbstractPeptides and proteins with molecular weights of ca 20 000 have been mass measured with accuracies of ±0.5 Da using electrospray ionization interfaced to a double‐focusing magnetic sector mass spectrometer. Factors affecting mass measurement accuracy such as resolution, peak profiles, calibration, data processing, and mass calculations are discussed.
Studies on the metabolism of omeprazole in the rat using liquid chromatography/ionspray mass spectrometry and the isotope cluster technique with [34S] omeprazole
Authors: Weidof Lars , Covey Thomas R. 
Published: May 2005

AbstractThis paper describes the application of the ionspray (pneumatically‐assisted electrospray) interface for liquid chromatography (LC) and atmospheric‐pressure ionization mass spectrometry (API MS) to samples obtained in a study on the metabolism of omeprazole. In this study [34S]omeprazole was utilized for the stable isotope cluster technique. Over forty metabolites in a sample of partially purified rat urine were resolved by gradient elution LC with ionspray API MS detection, and each of them produced molecular ion 1:1 clusters (MH+ and [MH+2]+). The Chromatographic fidelty of the total‐ion current (TIC) was excellent. The endogenous matrix of the sample was quite low, allowing a background‐substracted averaged mass spectrum of the entire TIC trace to produce a ‘metabolite mass profile’ depicting all the molecular ion 1:1 clusters in the sample. From this mass profile, it was possible to obtain direct information concerning oxygenation an conjugation reactions of the parent compound.
Sample immobilization protocols for matrix‐asssisted laser‐desorption mass spectrometry
Authors: Mock K. K. , Sutton C. W. , Cottrell J. S. 
Published: May 2005

AbstractMethods are described fsor the purification of proteins prior to analusis by matrix‐assisted laser‐desorption mass spectrometry. Contaminated protein sample were immobilized onto the surface of sample targets and rinsed. In general, a layer of electrosprayed nitrocellulose gave better results than the sroughened gold surface of an untreated target. Using this approach, spectra could be obtained from low picomole quantities of protein in the presence of sdcontaminants which did not inhibit the binding of the protein to the substrate.
Synchronized collision‐cell energy ramping. Improving the quality of product‐ion spectra
Authors: Fitton E. M. , Monaghan J. J. , Morden W. E. 
Published: May 2005

AbstractThe design and use of an RF‐only collision‐cell ramp generator is described. The generatio controls the collision energy voltage applied to the RF‐only collision cell in a hybrid mass spectrometer of BEqQ geometry. The generator enables the collision‐cell voltage to be increased or decreased in a linear ramp, over the full 500 V available. The start/stop functions of the ramp are synchronized under data system control to the scan of the quadrupole mass analyser. The collision‐induced dissociation spectra so produced show an increase in the product ion abundance.
Mass spectrometric study of simple olefinic flames: Comparison with laser diagnostics of C2H4/O2/Ar flames at 20 torr
Authors: Howard Stephen L. , Locke Randy J. , Sausa Rosario C. , Miziolek Andrzej W. 
Published: May 2005

AbstractA new research apparatus for characterization of low‐pressure premixed flames has been developed. This instrument incorporates several spectral techniques in one apparatus so that various diagnostic techniques can be quantitatively compared and the usable detection range expanded. Features include detection by mass analysis with a triple quadrupole mass spectrometer and by laser techniques such as laser‐induced fluorescence. Temperature profiles of the flame both with and without the mass spectrometer probe were obtained by thermocople. Concentration profiles of the highly reactive flame species H˙, O, and OH˙ were obtained and compared.
Analysis of a mass‐analyzed ion kinetic energy profile. II. Systematic determination of the kinetic energy release distribution
Authors: Yeh In Chul , Kim Myung Soo 
Published: May 2005

AbstractA systematic method to evaluate the kinetic energy release distribution from the mass‐analyzed ion kinetic energy (MIKE) spectrum of a metastable ion decomposition, namely lunicolecular fragmentation of lpolyatomic ions, has been ceveloped. The analytical expression for a MIKE profile at a single kinetic energy release developed in lthe preceding paper has been utilized. The present method has been applied to the case of unimolicular dissociation of the t‐butylbenzene molecular ion and to the rather extreme case of a charge‐separation reaction of C7H generated form toluene. Excellent agreements between the experimental data and calculated results have been observed.
Exploratory data analysis applied to the interpretation of mass spectra of pyrrolidin‐1‐yloxy radicals
Authors: Jerkovich Gyula , Varmuza Kurt , Werther Wolfgang , Sár Cecília P. , Hideg Kálmán 
Published: May 2005

AbstractMethod of multivariate statistical analysis have been applied to the mass spectra of pyrrolidin‐1‐yloxy derivatives. A graphical representation of the results obtained by using fragment‐specific features proides a staightforward method of visualizing mass spectra/structure relationships. The explanatory power of the relatioonships can be assessed by finding linear discriminant components in the space of fragement‐type features. Computer‐generated spectral‐type features, when used as spectral classifiers, show statistilcally comparable performance on the same set of mass spectra.
Ion‐trap mass spectrometry applications in forensic sciences. I. Identification of morphine and cocaine in hair extracts of drug addicts
Authors: Curcuruto O. , Guidugli F. , Traldi P. , Sturaro A. , Tagliaro F. , Marigo M. 
Published: May 2005

AbstractDaughter‐ion spectra obtained by ion‐trap mass spectrometry have been successfully employed in the field of drug abuse investigation. Selection and collison‐induced fragmentation of molecular‐ion species of morphine and cocaine lead to an easy identification of such molecules in hair extracts of heroin and cocaine addicts.
Comparison of the fast‐atom bombardment and electrospray ionization mass spectra of meso‐pyrzolylporphyrins
Authors: Aubagnac Jean‐Louis , Münster Helmut , Elguero José , Meutermans Wim 
Published: May 2005

AbstractFast‐atom bombardment (FAB) and Electrospray ionization (ESI) mass spectra of meso‐pyrazolylporphyrins have been studied. Both types of spectra allow one to determine the molecular weight of each compound studied. ESI mass Spectra show two further nteresting properties. First, there is addition of only one and two protons. Second, the ESI spectra show cluster ions for which the measured and theoretical isotope rations are in good occurrence of reduction phenomena prevents such a calculation from the FAB mass Spectra.
Mass spectral studies of some protoadamantanoid ketones
Authors: Škare Danko , Mlinarić‐Majerski Kata , Švob Valdimir , Milivojevič Dušan 
Published: May 2005

AbstractThe mass spectra of saturated and unsaturated protpadamentanoid ketones wee studied. Remarkable and unusual loss of water in 10 protoadamantanone is explaned by the flesibility of the ethono‐bridge and the ability for intera ction with carbony. three fragmentation paths of protoadamantanoid ketones are disussed.
Computer‐assisted determination of elemental composition of fragments in mass spectra
Authors: Kumar K. , Menon A. G. , Sastry P. S. , Mathur D. 
Published: May 2005

AbstractThis paper presents details of an expert system that infers elemental composition of fragment peaks in a mass spectrum and suggests possible chemical formulae for the molecular ion even when it does not itself appear in the spectrum. The system relies on a knowledge of the natural isotopic abundances of the elements, and exploits the fact that fragments are siblings, with the molecular ion as their parent. The program has been written in PASCAL and runs on any IBM PC‐AT compatible machine.
Electron‐impact induced fragmentation of spiro‐1‐pyrazolines
Authors: Dinya Zoltán , Lipták Miklós , Lévai Albert , Tóth Gábor , Vékey Károly 
Published: May 2005

AbstractThe positive‐ion electron impact mass spectra of twelve spiro‐1‐pyrazolines have been recorded as 70 eV electron energy and the dat analyzed to elucidate their fragmentation pathways. None of these compounds gave abundant molecular ions (M+) due to the instability of the pyrazoline ring. The first step in the decomposition of M+ ions is the elimination of a nitrogen molecule followed by a rearrangement resulting in the formation of the cation radical [M–28]+, the decomposition of which is discussed in detail. The proposed fragmentation pathways and their mechanisms are supported by high‐resolution data, linked‐scan measurements at constant B/E and collision‐induced dissociation‐mass‐analyzed ion kinetic energy spectra.
An electron ionization and fast‐atom bombardment mass spectrometric study of some N(10)‐substituted phenothiazine‐S‐oxides
Authors: Hegedüs‐Vajda Judit , Tamás József , Taulov Ivan G. 
Published: May 2005

AbstractElectron ionization mass spectral behavior of N R substituted phenothiazine‐S‐oxides (R:CH2CCH3CH2, CH2CCH, CCCH3, COCH3, COC2H5 and COC6H5) has been studied by comparison of normal and daughter‐ion mass spectra. Among several characteristic pathways, formation of [MOR]+, C12H8NS+ ions (m/z 198) was found to result in a common and abundant fragment peak for both N‐alkyl and N‐acyl derivatives. Appearance energy measurements as well as thermochemical considerations revealed this ˙OR loss, to be a single‐step dissciation process and to correspond to the energetically most favoured primary decomposition of M+˙; it seems to involve a transannular rearrangement. The ˙OR elimination also occurred from [MH]+ ions, produced by fast‐atom bombardment.
An investigation of fragmentation mechanisms of doubly protonated tryptic peptides
Authors: Tang Xue‐Jun , Boyd Robert K. , Bertrand M. J. 
Published: May 2005

AbstractPeptides formed as reaction products, of specific hydrolysis of proteins by trypsin, are characterized by a basic residue (Arg or Lys) as the C‐terminus, which facilitates formation of bundant [M+2H]2+ ions under electrospray r ionspry conditions. These doubly charged ions readily dissociate upon collisional activation to y" and b fragment ions which are mass complemens of one another. The suggestion tht these fragments are formed by direct charge‐separation disociatons must contend with the observation that the y" intensities are generaly appreciably larger than those of their b counterparts. However, it is shown that this can be accouned for by a greater susceptibility f the b ions to undergo further dissociaton to smaler fragments such as immonium ions. In addition no evidence could be found to support alternative mechanisms, including dissociative electron capture, for which equal intensities of the two fragment ion series are not obligatory. Initial protonation at the N‐terminus was shown to be required for formation of these [M+2H]2+ ions via its suppression by mono‐acetylation at the N‐terminus. These findings, and others concerning formation of [y"′]2+ fragments from singly protonated peptides, via charge‐site‐induced cleavages and intramolecular proto transfers between nitrogen atoms, respectively.
Characterization of iminopropadienone ions and neutrals in a tandem mass spectrometer
Authors: Flammang Robert , Laurent Sophie , Flammang‐Barbieux Monique , Wentrup Curt 
Published: May 2005

AbstractRadical‐cations of iminopropadienones (RNCCCO+˙) have been generated by dissociative ionization of isoxazle precursors a structurally characterized by collisional activation mass spectrometry; the corresponding neutral cumulenes have also been produced in a tandem mass spectrometer by neutralization and/or flash‐vacuum pyrolysis experiments.
Kinetic energy measurements of molecular ions ejected into an electric field by matrix‐assisted laser desorption
Authors: Zhou J. , Ens W. , Standing K. G. , Verentchikov A. , Sundqvist B. U. R. 
Published: May 2005

AbstractMeasurements of kinetic energy distributions of molecular ions ejected into an extraction field by matrix‐assisted laser desorpton re reported. The measurements were made in a time‐of‐flight mass spectrmeter with an electrostatic mirror by measuring the reflected signal as a function of the difference between the accelerating voltage and the voltage applied t the mirror. The molecular ions ere found to have less kinetic energy than the extraction field alone would normally provide, i.e. we observed an nergy deficit. Under conditons typical for a matrix‐assisted laser desrptio experiment, the deficit is about 24 eV for oleclar ions of insulin. The size of the deficit increases with the intensity of the molecular ion signal, and the molecular weight of the protein; t is also larger for negative molecular ions than for positive molecular ions.
Mass spectrometric studies on some macrocyclic, macrobicyclic and macroacyclic Schiff bases
Authors: Guerriero P. , Tamburini S. , Vigato P. A. , Catinella S. , Traldi P. 
Published: May 2005

AbstractThe mass spectrometric behaviour of four macrocyclic, one macrobicyclic and one macroacyclic Schiff bases, obtained by one‐step multiple condensation reactions of 2,6‐diformyl‐4‐methylpropane, 1,3‐diamino‐ 2,2‐dimethylpropene, 1,5‐diamino‐3‐oxapentane or tris‐(2‐aminoethyl) amine under fast‐atom bombardment conditions, was studied in detail with the aid of mass‐analyzed ion kinetic energy spectrometry. The mass spectrometric behaviour of a mononuclear macrobicy La(III) complex is also described.
Investigation of the evaporation of graphite in high‐voltage vacuum discharge: The formation mechanism of carbon clusters
Authors: Cornides I. , Morvay L. 
Published: May 2005

AbstractThe applications of kinetics calculations to determine the size distribution of Cn clusters formed from the vaprized material of graphite requires aknowlledge of the initial composition of the carbon vapour. By a 13C iisotope tracer experiment it is shown that a considerable part of the Cn molecules in the case of n⩾3 evaporate directly as polyatomic fragments of the crystal structure of graphite, while the other, probably the greater part, is formed in the vapour. A more quantitative evalution of the experimental data is to be attempted later.
Application of fast‐atom bombardment mass spectrometry for sequencing of a hemoglobin fragment, naturally occuring in human cerebrospinal fluid
Authors: Glämsta Eva‐Lena , Nyberg Fred , Silberring Jerzy , Oliver R. W. A. 
Published: May 2005

AbstractRecent studies have reveallled the presence of a new group of opioid peptides, the hemorphins, in the human pituitary as well as in human cerebrospinal fluid. The hemorphins are structurally related to sequence segments residing in the β, δ,γ or ϵ‐chains of hemoglobin. In this study we have applied fast‐atom bombardment mass spectrometry (FAB‐MS) to elucidate the sequence of a hemorphin fragment isolated from the cerebrospinal fluid of patients with cerebrovascular bleedings. The FAB‐MS was used in conjunction with carboxypeptidase Y degestion and results indicated that this procedure proved to be a powerful tool for rapid sequence determination. The recovered peptide was thus found to be identical with the sequence 32–41 of the above mentioned hemoglobin chainss.
Determination on the microscale of plasmatic lactic acid as its t‐butyldimethylsilyl derivative by stable‐isotope dilution using capillary gas chrommatography/mass spectrometry
Authors: Rocchiccioli F. , Sanière M. 
Published: May 2005

AbstractA new sensitive and precise method for the determination of lactic acid in plasmatic microsamples (50 μL) has been developed. Lactic acid was directly extracted from plasma by ethyl acetate in acidic conditions, and analysed as its di‐t‐butyldimethylsilyl derivative by capillary gas chromatography/electron‐impact mass spectrometry (GC/MS). The internal pstandard was a previously synthesized deuterated compound, 3‐[2H]‐(2R)‐lactic acid. The method gives good reproductibility and precision, the ovedrall standard deviation being better than 3%. The GC/MS assay was in good agreement with the enzymatic determination.
Matrix‐assisted laser desorption of peptides and proteins on a quadrupole ion trap mass spectrometer
Authors: Jonscher Karen , Currie Graeme , McCormack Ashley L. , Yates John R. 
Published: May 2005

AbstractThe use of ultraviolet matrix‐assisted laser desorption (MALD) to ionize peptides for analysis in a quadrupole ion trap is described. An ion source was modified to accommodate a fiber optic to transmit laser radiation from a notrogen laser (337 nm) to the tip of the sample probe containing peptide of protein samples in a matrix of 2,5‐dihydroxybenzoic acid (DHB) or 3,4‐dimethoxy‐4‐hydrexy‐cinnamic acid. Detection limits are demonstrated with 10 fmol of sperm‐whale‐myoglobin. The dimer of sperm‐whale myoglobin was also observed at m/z 34, 430. A. comparison is made of the tandem mass spectrum of (MS/MS) of human angiotensin I desorbed by MALD to that of the peptide desorbed by liquid secondary‐ion mass spectrometry. Both spectra were found to contain abundant structural information.
Au+, Ag+ and Cu+ attachment to polybutadiene in laser desorption at 1064 nm
Authors: Dean Patricia A. , O'Malley Rebecca M. 
Published: May 2005

AbstractCu+, Ag+ and Au+ gas‐phase ions have been found, in laser desorption time‐of flight experiments, to attach efficiently to polybutadiene, a polymer containing no polar groups. The desorption and cation attachment were accomplished using the fundamental frequency of Nd:YAG laser, at a wavelength of 1064 nm, and supporting the samples on probe tips made of the appropriate metal. laser powers were in the range of 1.0–2.0 × 108 W/cm2. Time delays between the application of the laser pulse and the sampling of the resultant ion population were in the range 30–80 μs. The Au+ attachment is contrary to the reported findings from a laser desorption charge‐exchange spectrum obtained from a gold surface by Kahr and Wilkins. The differences in the spectra are discussed in terms of the differences in the two experimental methods. Attachment by these ions could be useful in the laser desorption analysis of other polymer molecules, particularly those containing no polar groups.
Flow injection Thermospray® mass spectrometry for the automated analysis of potential agricultural chemicals
Authors: Hayward Mark J. , Snodgrass Joseph T. , Thomson Michael L. 
Published: May 2005

AbstractFlow injection Thermospray mass spectrometry (TSP‐MS) has been developed and utilized for molecular weight and structural confirmation for thousands of potential new agricultural chemicals. Initially, it was necessary to find TSP conditions which provide an optimal compromise between providing reproducible, informative mass spectra and being sufficiently universal and rugged for a wide variety of compound types. By acquiring both positive‐ and negative‐ion spectra for each sample, the range of compounds that can be analyzed successfully is greatly expanded. The method developed is sufficiently universal that flow injection TSP‐MS now provides the required information in approximately 70% of the mass spectrometric structural confirmations performed at the Agricultural Research Division of American Cyanamid. The success in using flow injection TSP‐MS led to the development of instrumentation to fully automate these analyses. An IBM PC/AT® compatible computer is used to control sample delivery, data acquisition and data output. The PC performs the functions of both terminal and operator for a Finnigan® TSQ 46 triple quadrupole mass spectrometer and its Data General Nova® 4X data system, while simultaneously controlling a Micromeritics® 725 (Alcott®) autosampler and its Reodyne® 8126 pneumatically actuated 6‐port sampling valve. Furthermore, the need to document analyses in a manner that is consistent with Good Laboratory Practices has led to automated documentation for the instrument analysis log, as well as for the headers of the electronic data files and the printed spectral output. The new automated flow injection TSP‐MS system described here was constructed using only commercially available equipment and has notably improved efficiency by reducing the instrument time required to record spectra and by minimizing analyst intervention.
The confirmation and quantitation of LSD in urine using gas chromatography/mass spectrometry
Authors: Bukowski N. , Eaton A. N. 
Published: May 2005

AbstractConfirmation and quantitation of LSD, as its trimethyI silyI derivative, is carried out using a commercial gas chromatography/mass spectrometry system. The method uses 4 times less sample than previous methods, extends column life by reducing the amount of derivatizing agent used and can detect and quantify LSD at the 10 pg mL−1 level.
Matrix‐assisted laser desorption time‐of‐flight mass spectrometry of oligonucleotides using 3‐hydroxypicolinic acid as an ultraviolet‐sensitive matrix
Authors: Wu Kuang Jen , Steding Anna , Becker Christopher H. 
Published: May 2005

AbstractMatrix‐assisted laser desorption time‐of‐flight mass spectrometry has been used to produce quasimolecular ion signals from underivatized mixed‐base single‐stranded DNA oligomers ranging from 10 to 67 nucleotides in length. These results were obtained with a new matrix material, 3‐hydroxypicolinic acid (3‐hydroxypyridine‐2‐carboxylic acid)which showed significant improvement over many previously reported matrices studied in terms of mass range available, signal‐to‐noise ratio, and the ability to analyze mixed base oligomers. The desorption and simultaneous ionization was by pulsed laser light at 10 to 50 mJ/cm2, studied at 266, 308, and 355 nm. Spectra taken at 266 nm provided the smallest amounts of doubly charged and dimer ions—characteristics desirable for DNA sequencing by this technology. Negative‐ion spectra were uniformly superior to positive‐ion spectra. This new matrix also is quite effective for molecular weight determinations of peptides and proteins in both positive‐ and negative‐ion modes.
Laser mass spectrometry of dibenzodioxin, dibenzofuran and two isomers of dichlorodibenzodioxins: Selective ionization
Authors: Weickhardt C. , Zimmermann R. , Boesl U. , Schlag E. W. 
Published: May 2005

AbstractLaser‐induced mass spectra and UV spectra of dibenzodioxin, dibenzofuran, and two isomers of dichlorodibenzodioxin measured by means of resonance‐enhanced multiphoton ionization in a supersonic molecular beam are presented. The UV spectra show sharp bands and large wavelength shifts both being specific to the number and position of the chlorine atoms. The mass spectra are free of fragments. Therefore the prerequisites for isomer selective ionization and detection of these substances are fulfilled. This encourages further work on polychlorinated dibenzodioxins and dibenzofurans.
Observation of intact (heme‐bound) myoglobin by electrospray ionization on a double‐focusing mass spectrometer
Authors: Loo Joseph A. , Giordani Anne B. , Muenster Helmut 
Published: May 2005

AbstractA noncovalently bound complex, the heme‐apomyoglobin protein system (Mr 17 568), was detected using electrospray ionization on a double‐focusing mass spectrometer with an array detector. The kilovolt energy conditions used for ion transmission and focusing did not cause significant amounts of fragmentation of the weakly‐bound complex. With a high‐performance array detector, femtomolar sensitivity was achieved for myoglobin in water.
Enlarging the stability domain for ion trap tandem mass spectrometry (MS/MS)
Authors: Gordon D. B. , Woods M. D. 
Published: May 2005

AbstractThe low‐ mass cut‐off in ion trap tandem mass spectrometry (MS/MS) is significantly improved by employing a sawtooth driving function on the ring electrode in place of the usual sinusoidal AC potential. The theory is explained with examples involving both the ‘tickle’ and ‘boundary‐effect’ MS/MS methods.