bluuebunny/crossref_metadata_2025_split huggingface dataset:
The determination of protein, oligonucleotide and peptide molecular weights by ion‐spray mass spectrometry
Authors: Covey Thomas R. , Bonner Ronald F. , Shushan Bori I. , Henion Jack , Boyd R. K. 
Published: May 2005

AbstractThe mass spectra of several compounds with molecular weights in the 2500–20 000 Da range were obtained with a quadrupole mass spectrometer equipped with an atmospheric pressure ion source. Average molecular weight determinations of mellitin (2846.4 Da), a synthetic oligonucleotide (4262.8 Da), myoglobin (16 950.4 Da) and on the subunits of β‐lactoglobulin (18 277.1 Da) requiring as little as 1 pmol of material were achieved with accuracies and precisions of ± 1 Da. An ion‐spray interface was used to produce ions via the ion evaporation process, producing mass spectra containing a series of multiply‐charged molecular species. A simple method for calculating the molecular weight of unknown compounds from the spectra containing multiply‐charged ions is described.
A novel hybrid mass spectrometer
Authors: Suter M. J.‐ F. , Gfeller H. , Schlunegger U. P. 
Published: May 2005

AbstractA new hybrid mass spectrometer of BEQiQu geometry (B, magnetic sector; E, Electric sector; Qi, quistor; Qu, quadrupole mass filter) is described. The high resolution stage (BE) is coupled to a quistor via a series of deceleration lenses, and this is followed by a mass‐analysing quadrupole. This configuration enables the storing of ions, investigation of their gas‐phase chemistry and the subsequent identification of the resulting fragment or product ions.
Precision and accuracy in XQQ measurements: A summary report of the National Institute of Standards and Technology/Environmental Protection Agency International Round Robin
Authors: Martinez Richard I. 
Published: May 2005

AbstractWe describe the kinetics‐based measurement protocol which was used for the National Institute of Standards and Technology/Environmental Protection Agency International Round Robin, and provide an interim summary report of the results. At least 50% of the QQQ instruments currently in the field potentially can provide a dynamically correct (i.e., instrument‐independent) representation of ion/molecule reactions.
Microdetermination of glucose content of plasma and its isotopic enrichment using capillary gas chromatography/ammonia chemical‐ionization mass spectrometry
Authors: Lepetit N. , Rocchiccioli F. 
Published: May 2005

AbstractA new sensitive and precise method for the determination of the isotopic enrichment of [6, 6‐D2] ghicose and concentration of glucose in plasma microsamples (20 μL) has been developed. Glucose was extracted from plasma samples by anion‐cation column‐exchange with absolute ethanol, derivatized as 1,2:3,5‐bis(butylboronate)‐6‐acetyl‐α‐D‐glucofuranose, and analysed by capillary gas chromatography/ammonia chemical‐ionization mass spectrometry. This method gives a better reproducibility and precision (variation coefficient below 1%) than methods using isobutane chemical ionization.Stable isotopes are being used increasingly to investigate energy metabolism in vivo. Recent work has involved the development of methodologies, especially mass spectrometry, to perform tracer experiments using the stable isotopes 2H, 13C, or 15N.1–4 Chemical‐ionization mass spectrometry is extensively used for the analysis of isotopically labelled amino acids.2–6In neonates and chidren, „true”︁ glucose production can be measured by the continuous infusion of the stable isotopically labelled tracer 6,6‐dideutero‐glucose (6,6‐D2‐glucose), and analytical measurement is performed using gas chromatography/electron‐ionization mass spectrometry (GC/EIMS).7Herein, we present a new, simple and sensitive method for the determination of the isotopic enrichment of [6,6‐D2]glucose and measurement of the concentration of glucose in plasma microsamples (20 μL), based on the use of capillary gas‐chromatography/ammonia chemical‐ionization mass spectrometry of 1,2:3,5‐bis(butylboronate)‐6‐acetyl‐α‐D‐glucofuranose.
Orthogonal‐acceleration time‐of‐flight mass spectrometer
Authors: Dawson J. H. J. , Guilhaus M. 
Published: May 2005

AbstractA new time‐of‐flight mass analyser compatible with conventional continuous ionization methods is described. A mass resolution at m/z 2000 of m/Δm>2000 (50% valley) is predicted for the instrument which is presently being prototyped. Sensitivity advantages over scanning instruments are also predicted for this instrument.
Factors affecting the ultraviolet laser desorption of proteins
Authors: Beavis Ronald C. , Chait Brian T. , Standing K. G. 
Published: May 2005

AbstractThe production of high‐mass quasimolecular ions from proteins by matrix‐assisted ultraviolet laser desorption is described. A simple time‐of‐fight system using a Q‐switched frequency‐quadrupled Nd‐YAG laser to desorb protein molecules is shown to have a mass range of up to 116 000 u by the observation of intact, singly charged quasimolecular ions from 700 fmol of β‐galactosidase subunit (mol.wt = 116 336 Da). Both positive‐ and negative‐ion spectra of proteins are shown. Four new matrix materials, with properties as good as or better than nicotinic acid, are described. A mass resolution of approximately 500 (full width at half maximum definition) is demonstrated for proteins with mol.wt < 20 000 Da. Product species, formed by fast photochemical reactions in the matrix, are observed to form adduct ions with protein molecules. These adduct ions are a significant cause of the observed broadness of protein quasimolecular ion peaks. The practical physical considerations in detection of large‐mass quasimolecular ions from laser desorption, such as detector overloading, are discussed.
A novel fragmentation process in the fast‐atom bombardment/tandem mass spectra of peptides cationized with Na+, determining the identity of the C‐terminal amino acid
Authors: Kulik Willem , Heerma Wigger , Terlouw Johan K. 
Published: May 2005

AbstractThe metastable ion spectra of the [M + Na]+ ions generated by fast‐atom bombardment of sodium chloride containing oligopeptide samples are shown to produce an intense sequence ion from which the identity of the C‐terminal amino acid can be readily established.
Determination of linkage position in disaccharides by negative‐ion fast‐atom bombardment mass spectrometry
Authors: Ballistreri Alberto , Montaudo Giorgio , Garozzo Domenico , Giuffrida Mario , Impallomeni Giuseppe , Daolio S. 
Published: May 2005

AbstractNegative‐ion fast‐atom bombardment linked‐scan spectra at constant B/E have been shown to allow differentiation of the linkage position in hexose‐hexose‐disaccharides. Sequence information can also be obtained when there is a molecular weight difference between the monosaccharide units in the carbohydrate molecule.
Performance of a liquid‐junction interface for capillary electrophoresis mass spectrometry using continuous‐flow fast‐atom bombardment
Authors: Reinhoud N. J. , Niessen W. M. A. , Tjaden U. R. , Gramberg L. G. , Verheij E. R. , van der Greef J. 
Published: May 2005

AbstractThe on‐line coupling of capillary electrophoresis and mass spectrometry using a continuous‐flow fast‐atom bombardment system in combination with a liquid‐junction interface is described. The influence of the liquid‐junction coupling on the efficiency and the resolution is investigated. Qualitative analysis of small peptides and quantitative analysis of dextromethorphan is demonstrated with detection limits in the low ng/mL range, indicating the feasibility of the method in bioanalysis.
Effect of trifluoroacetic acid on the reduction of disulfide bridges in peptides analyzed by fast‐atom bombardment mass spectrometry
Authors: Visentini J. , Gauthier J. , Bertrand M. J. 
Published: May 2005

AbstractSome of the factors that influence the reduction of disulfide‐containing peptides under fast‐atom bombardment have been investigated using two neurohormonal peptides that include disulfide bridges in their structures. Deaminoarginine‐vasopressin (DAVP) and arginine‐vasopressin (AVP) have been analyzed as their acetate and trifluoroacetate salts. Results obtained in a thioglycerol matrix indicate that the peptides analyzed as their acetate salts are completely reduced under bombardment, whereas the trifluoroacetate salts show little evidence of reduction. Addition of trifluoroacetic acid to the acetate sample prior to bombardment inhibits reduction whereas addition after bombardment shows no effect on the reduction, thereby indicating the irreversibility of the process. Time‐monitoring experiments conducted with the acetate salts of DAVP and AVP in common matrices such as thioglycerol, dithiothreitol + diethioerythritol, glycerol, hydroxyethyldisulfide and nitrobenzyl‐alcohol demonstrate an important effect of the chemical nature of the matrix on reduction. In matrices containing thiol groups, the reduction is extensive, whereas it is almost suppressed in matrices such as hydroxyethyldisulfide and nitrobenzylalcohol. However, the addition of trifluoroacetic acid to all of these matrices essentially eliminates reduction and provides measured isotopic peak ratios that are in agreement with theoretically calculated values for these peptides.
Cinnamic acid derivatives as matrices for ultraviolet laser desorption mass spectrometry of proteins
Authors: Beavis Ronald C. , Chait Brain T. , Fales H. M. 
Published: May 2005

AbstractThe paper reports the discovery of three new matrices for the matrix‐assisted laser desorption of proteins. These new matrices (sinapic, ferulic and caffeic acids) are cinnamic acid derivatives that have several pratical advantages over the nicotinic acid matrices previously used. These materials form much less intense photochemically generated adduct peaks in the protein quasimolecular ion signal and the adduct peaks that are present are easier to resolve. These new matrices are produce intense protonated‐molecule ions from all of the proteins (over 50) so far examined. These new matrices are also very stable in a vacuum, allowing for their convenient use in very high vacuum applications (e.g., Fourier transform ion cyclotron resonance mass spectrometry).
Cluster‐ion abundances and geometrical structures of magnesium oxide clusters generated by bombardment with xenon and oxygen ions
Authors: Katakuse I. , Ichihara T. , Ito H. , Hirai M. 
Published: May 2005

AbstractTwo types of magnesium oxide clusters, (MgO) and (MgO)nMg+ have been obtained by the bombardment of magnesium with a mixture of xenon and oxygen ions. Enhanced ion intensity in the cluster mass spectra was observed at certain n values. The correlation between the geometrical structures of the clusters and their abundances is discussed.
Methodological approach to the characterization of diacylphosphatidyl cholines in rabbit lung lavage fluid by fast‐atom bombardment mass spectrometry
Authors: Allmaier G. , Schmid E. R. , Gasser H. , Strohmaier W. , Schlag G. 
Published: May 2005

AbstractStrong evidence exists that the distribution of phospholipids in the lung is a function of the degree of adult respiratory distress syndrome. The capabilities of positive‐ion fast‐atom bombardment (FAB) mass spectrometry for the determination of the relative distribution of intact diacylphosphatidylcholine species in lung lavage fluid were investigated. Two different FAB matrices and two different isolation/purification procedures—extraction/thin layer chromatography—high performance liquid chromatography (TLC‐HPLC)—have been evaluated. In addition the relative fatty acid composition of the diacylphosphatidylcholines was determined by negative‐ion FAB mass spectrometry using the [RCOO]− fragment ion. These results were compared with those obtained by gas chromatographic determination of the fatty acid methylesters.
Collisionally activated dissociation of peptides using a quadrupole ion‐trap mass spectrometer
Authors: Kaiser Raymond E. , Cooks R. Graham , Syka John E. P. , Stafford George C. 
Published: May 2005

AbstractThe ion‐trap mass spectrometer can be used to record mass and multi‐stage tandem mass spectra (MSn) on small peptides. The compounds are ionized by Cs+ surface ionization, injected into the trap, mass selected, activated by collision, resulting in dissociation and mass‐selectively ejected. Tandem mass spectrometric data on sub‐fmol amounts of Gramicidin S are shown, along with tandem mass spectrometric and MSn data on two other peptides. The experiment is distinguished by its very high sensitivity and the high quality of sequence information obtained.
A method based on catalytic hydrogenation for the identification of monohydroxy metabolites of isomeric tetrahydrocannabinols
Authors: Harvey D. J. , Brown N. K. 
Published: May 2005

AbstractIdentification of isomeric monohydroxy metabolites of 6a,10a‐trans‐tetrahydrocannabinols (THCs) by gas chromatography/mass spectrometry as their trimethylsilyl derivatives is aided by catalytic hydrogenation to hydroxyhexahydrocannabinols (hydroxy‐HHCs) in cases where the metabolites themselves give similar spectra. This method gives common products from a range of hydroxy metabolites of isomeric‐THCs which can be compared with reference compounds synthesized from available hydroxy‐THCs from the Δ8 and Δ9‐series. Sufficient of these compounds are available to enable hydroxy‐HHCs to be prepared with hydroxy groups in most positions accessible to metabolic enzymes. This technique provides a simple alternative to a laborious synthesis of each new metabolite for confirmatory purposes and enables all metabolites in a metabolic experiment to be identified in a single sample. Catalytic hydrogenation was achieved using rhodium on alumina in methanol; this gave rapid, quantitative hydrogenation of underivatized metabolites without the elimination of the hydroxy groups inherent with hydrogenation with other common catalysts. The method was validated by an examination of the metabolites of Δ11 THC in rats and comparison of the results with published work.
Use of charge‐separation reactions for sequencing peptides
Authors: Vékey Kàroly , Candido Manuela , Traldi Piero 
Published: May 2005

AbstractCharge‐separation reactions of the doubly charged molecular ion of bradykinin, generated by fast‐atom bombardment, were studied. The same types of reactions occurred as in singly charged ions, but fragmentations around the middle of the peptide chain were much more abundant. This suggests that charge separation of doubly charged ions may provide more sequence information than fragmentation of singly charged species.
An electrospray‐ionization mass spectrometer with new features
Authors: Chowdhury Swapan K. , Katta Viswanatham , Chait Brian T. 
Published: May 2005

AbstractThe construction and performance of an electrospray‐ionization mass spectrometer with new features are described. The mass spectrometer consists of a newly designed electrospray ion‐source that is plugged directly into a modified commercial quadrupole mass spectrometer with the ions entering the mass analyzer through a long metal capillary tube and three stages of differential pumping. The present ion source differs from previous designs in the combination of techniques employed in the transportation and desolvation of solvated biomolecule ions, prior to mass analysis. Transport of ionized entities between atmospheric pressure and vacuum is carried out through a 203 mm long stainless steel capillary tube with a 0.5 mm bore. Desolvation is effected by the use of controlled heat transfer through the long capillary tube and collisional activation in a region of reduced pressure between the capillary tube exit and the skimmer. Desolvation with this system is convenient and effective and does not involve the strong countercurrent flows of gases that have been used by all previous workers. The effects on the spectra of peptides of capillary tube temperature and desolvation collision energy are investigated. Electrospray‐ionization mass spectrometric results are described for thirteen proteins with molecular masses ranging from 5000 to 77 000 Da. The performance of the present instrument, with respect to mass accuracy and sensitivity, is comparable with previously reported systems. The effect of protein concentration in solution on the electrospray mass spectrometric response and charge‐state distribution is discussed.
Molecular weight determination of underivatized oligodeoxyribonucleotides by positive‐ion matrix‐assisted ultraviolet laser‐desorption mass spectrometry
Authors: Spengler Bernhard , Pan Ying , Cotter Robert J. , Kan Lou‐Sing 
Published: May 2005

AbstractA Wiley‐McLaren type time‐of‐flight mass spectrometer has been used for molecular weight measurements of several unprotected oligodeoxyribonucleotides using matrix‐assisted UV laser desorption. Approximately 10 to 100 pmol of sample was required for recording their positive‐ion mass spectra with a mass resolution in the range of 150 to 300 (Full width at half maximum) (FWHM). Little fragmentation was observed.
The use of dynamically programmed scans to generate parent‐ion tandem mass spectra with the ion‐trap mass spectrometer
Authors: Todd J. F. J. , Penman A. D. , Thorner D. A. , Smith R. D. 
Published: May 2005

AbstractA method is described whereby, under software control, the scan function employed to collisionally excite ions in an ion‐trap mass spectrometer is regulated so as to obtain parent ion (fixed product) tandem mass spectral data. At the same time, constant neutral‐loss information is also provided. Key features are the automatic ‘intelligent’ selection of parent ions from observation of the initial mass spectrum and the scanning of the applied ‘tickle’ frequency in order to locate the precise resonance points for excitation of these ions. Results for the model compounds perfluorotributylamine (‘FC43’) and n‐butylbenzene are reported and complicating effects such as the unimolecular decay of the precursor ion species and charge exchange between product ions and the original sample material are discussed.
The formation of HOS− from deprotonated dimethyl sulphoxide and related species
Authors: Bowie John H. , Stringer Michael B. , Hayes Roger N. 
Published: May 2005

AbstractCollisional activation of MeSOCH and PhCH2SOC̄HPh (but not PhSOCH) yields an ion of m/z 49, identified as HOS−. It is proposed that this ion is formed following proton transfer to oxygen followed by cyclization and elimination.
A fast array detector system
Authors: Brunnée Curt , Pesch Reinhold , Schröder Ernst 
Published: May 2005

AbstractThe performance of a novel array detector system which can be operated during scanning of the magnetic field of a sector mass spectrometer is investigated. The increase in sensitivity as compared to a standard secondary‐electron multiplier slit detector is about 100 times. It is shown that the product of the mass window of the array detector and the resolution is constant. The maximum resolution which can be achieved with the array detector is 7500 full width at half maximum. The solid secondary‐ion mass spectrum of 12 attomol of gramicidin S demonstrates the extreme sensitivity of the system.
Mass spectrometric characterization of different norandrosterone derivatives by low‐cost mass spectrometric detectors using electron ionization and chemical ionization
Authors: de Boer D. , de Jong E. G. , Maes R. A. A. 
Published: May 2005

AbstractThe abuse of nortestosterone in sport is an important problem in doping‐control analysis. In order to detect the main urinary metabolite of nortestosterone, norandrosterone (NA), sensitive and specific methodology is necessary. In this context the use of a low‐cost mass spectrometric detector such as the Finnigan MAT ion‐trap detector (ITD) was studied. The electron ionization (EI) and positive‐ion chemical ionization (PICI) mass spectra of the methoxime‐trimethylsilyi, trimethylsilyl‐enol trimethylsilyl ether and pentafluoropropionic ester derivatives of NA are described. The limits of detection of these derivatives are compared with those obtained by the Hewlett‐Packard mass selective detector (MSD), another low‐cost mass spectrometric detector and operating only in the EI mode. For the derivatives of the reference standard of NA the ITD has in the EI mode the same limit of detection, in the range of 0.5 to 1 ng injected on the column, as the MSD. However, under these conditions the ITD provides more spectrometric information, because it gives full scan data. Moreover, with the same or even improved limits of detection the ITD can operate in the PICI mode. On the other hand, for the analysis of NA isolated from urine samples, the performance of the MSD was better than that of the ITD. The ion trapping technique is probably limited when the chemical background is high.
Computer modelling of fragmentation processes in radio frequency multipole collision cells
Authors: Davis Stephen C. , Wright Barry 
Published: May 2005

AbstractTo date, methods for calculating the trajectories of ions in radio frequency (RF) multipole fields have involved solving, analytically or numerically, the appropriate equations of motion. Another method is presented here whereby a non‐ideal distribution of field may be modelled and the position of an ion can be tracked, as it traverses the multipole. The validity of the calculations is discussed and some of the properties of collision cells are explained. Fragmentation processes within the cell are modelled showing that the focusing properties within the cell have a striking effect on parent‐ and daughter‐ion transmission.
Particle beam liquid chromatography/mass spectrometry on a double‐focusing high resolution mass spectrometer
Authors: Baczynskyj Lubomir 
Published: May 2005

AbstractThe particle beam liquid chromatography/mass spectrometry (LC/MS) interface has been adapted to a double‐focusing sector instrument of reversed geometry. Electron ionizaition (EI) mass spectra of single components injected through a loop or of mixtures separated via a reversed‐phase LC column have been recorded. These are superimposable with EI mass spectra obtained via a direct‐insertion probe. Sensitivity tests show that high picogram and low nanogram amounts of samples can be detected. Complete high‐resolution mass spectra on standards (single components and mixtures) were recorded. Good accuracy (better than 5 mmu) was obtained in most cases on 5 μg samples. To illustrate the versatility of the system, mass‐analysed ion kinetic energy scans and linked scans at constant B/E were obtained on the molecular ion of cholesterol (2.5 μg and 500 pg). Parameters relating to various parts of a commercial interface are briefly reported.
Homogeneous bottleneck model of matrix‐assisted ultraviolet laser desorption of large molecules
Authors: Vertes Akos , Gijbels R. , Levine R. D. 
Published: May 2005

AbstractThe factors affecting the yield of high‐mass molecules by matrix‐assisted ultraviolet laser volatilization are examined in a simple model. The key material factors appear to be a low heat of sublimation, subcritical concentration of the guest molecules and a high irradiance input in a short time compared to the sublimation induction period. The model is homogeneous in that the energy density is taken to be uniform within the ‘hot region’ of the matrix. The two competing effects are the rates of energy transfer from the matrix to the guest molecules and the desorption by sublimation. It is the bottleneck for energy transfer to the embedded guest molecules that makes their energy content lag behind that of the matrix. This is particularly the case for an initially cold sample. When a sufficiently high rate of sublimation can be achieved (e.g., using a high‐power laser), the guest molecules (or adduct ions) will desorb internally cold and will thus not fragment. Numerical simulations of the sublimation kinetics using realistic laser and material parameters support the conclusions and delineate the ranges of the critical factors.