bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved electrospray ionization of synthetic oligodeoxynucleotides
Authors: Stults John T. , Marsters James C. , Carr Steven A.
Published: May 2005

A method is described for rapid purification of synthetic oligodeoxynucleotides to remove sodium counter ions prior to electrospray ionization mass spectrometry. The oligomers, following purification by gel electrophoresis, are precipitated from ammonium acetate to replace sodium ions by ammonium ions, and dissolved in water. Negative‐ion electrospray spectra are presented for oligomers with up to 48 residues in which the most intense peaks correspond to the [MnH]n− ion. The spectrum of 77‐mer (Mr24039) shows the predominant peak as due to retention of only a single sodium ion. Changes in the spectra are reported for different instrument orifice voltages and different solution pH. The method should permit rapid, accurate analysis of most typical, synthetic oligodeoxynucleotides.
Behaviour of tetrabutylammonium tribromide under fast‐atom bombardment using protic and aprotic matrices
Authors: Lange C. , Benammar Y. , Berthelot J.
Published: May 2005

Tetrabutylammonium tribromide in a protic matrix, under FAB desorptiono, does not provide the tribromide anion as it does in the gas phase. In contrast, using an aprotic matrix it gives a complex tribromide anion.
Maximum entropy deconvolution in electrospray mass spectrometry
Authors: Ferrige A. G. , Seddon M. J. , Jarvis S. , Skilling John , Aplin Robert
Published: May 2005

The maximum entropy (MaxEnt) technique has been well established in image processing for the last decade. In more recent times MaxEnt has been applied to spectroscopic techniques and shows considerable promise. As part of a much wider evaluation of the Cambridge software, specifically MemSys3, the MaxEnt technique has been successfully applied to electrospray mass spectra.
Energetics of gramicidin S after UV laser desorption from a ferulic acid matrix
Authors: Huth‐Fehre T. , Becker C. H. , Beavis Ronald C.
Published: May 2005

Photoionization with coherent 118 nm vacuum ultraviolet light is applied to study kinetic energies of gramicidin S and ferulic acid molecules, laser desorbed from a ferulic acid matrix with 266 nm light. Analysis of the matrix photodecomposition products shows decarboxylation as a main photochemical pathway involved with desorption. Entrainment of the polypeptide by the matrix molecules is found under typical conditions. However, the velocity distributions are not particularly narrow, being at most borderline supersonic.
Charge‐remote fragmentation of taurine‐conjugated bile acids
Authors: Griffiths William James , Egestad Börje , Sjövall Jan
Published: May 2005

Taurine‐conjugated bile acids are an important group of biological metabolites. When investigated by negative‐ion fast‐atom bombardment collision‐induced dissociation mass spectroscopy they show charge‐remote fragmentations of the [MH]− pseudomolecular ion. These fragmentations provide information on the positions of ring substituents remote from the charge site. In the present work we have compared the negative‐ion fast‐atom bombardment collision‐induced dissociation spectra of six different conjugated bile acids.
An ion‐storage time‐of‐flight mass spectrometer for analysis of electrospray ions
Authors: Boyle James G. , Whitehouse Craig M. , Fenn John B. , Cotter Robert J.
Published: May 2005

A preliminary design and implementation of a novel approach to electrospray‐mass spectrometry anr described. Based on a time‐of flight mass analysis, the instrument provides several important advantages for on‐line mass analysis: 1, simplicity, ease of use and low manufacturing cost; 2, rapid scan speed, yielding quasi‐instantaneous full mass scans at repetition rates up to several kHz; 3, soft ionization and accurate mass determination of extremely large analyte molecules; 4, high sensitivity.
Mass spectrometer systems and products. A directory of manufacturers and suppliers
Authors: Lammert S. A. , Cooks R. G.
Published: May 2005

A directory has been compiled of companiesw which supply mass spectrometers, components and services.
Dynamic fast‐atom bombardment mass spectrometry of conjugated metabolites of benzo[a]pyrene
Authors: Yang Yang , Egestad Börje , Jernström Bengt , Sjöovall Jan , Gustafsson Jan‐Åke , Rafter Joseph , Bailli T. A.
Published: May 2005

The N‐acetylcysteine, cysteine and gluathione conjugates of r‐7,t‐8‐dihydroxy‐t‐9,10‐oxy‐7,8,9,10‐tetrahydrobenzo[a]pyrene as well as sulphuric and glucuronic acid conjugates of hydroxybenzo[a]pyrenes have been studied by fast‐atom bombardment mass spectrometry (FABMS). Dynamic FABMS has been shown to be advantageous over conventional static FABMS giving more intense spectra with less material in both positive‐and negative‐ion modes. The spectra show quasmolecular ions and fragment ions indicative of the aglycome and/or the conjugating group.
Pyrolysis/mass spectrometry and pyrolysis/gas chromatography/mas spectrometry analysis of polymers
Authors: Blazsó Marianne , Vékey Kàroly
Published: May 2005

The potential of pyrolysis/gas chromatography/mass spectrometry in the study of the chemical composition and structure of polymers and copolymers is demonstrated, and results obtained on polysilane copolymers, phenol‐formaldehyde polycondensates and diol modified epoxy resins are presented. Temperature/time‐resolved pyrolysis mass spectrometry, carried out in the direct inlet of a mass spectrometer, revealed the presence of monomer and oligomer residues and of volatile additives in epoxy resin samples. Basic information was also obtained on the mechanism of thermal decomposition reactions in polysilane copolymers and diol modified epoxy resins.
On some preparation methods in stable‐isotope mass spectrometry and their geochemical applications
Authors: Demény Attila , Fórizs István
Published: May 2005

Preparation of samples and their introduction into the mass spectrometer are very important in stable‐isotope mass spectrometry. The authors have found that using the Coleman method for hydrogen gas preparation from water an improved reproducibility can be achieved if the reaction tube containing the zinc and hydrogen gas is kept at >350°C when the hydrogen is collected into the mass spectrometer for measurement. One of the critical conditions for the carbonate preparation is the quality of phosphoric acid. The reproducibility is better if before every preparation series the phosphoric acid is saturated adding phosphoric pentoxide to the acid at 150°C. As an application of stabvle‐isotope mass spectrometry the origin of a certain limestone near Budapest (Hungary) has been determined after a long dispute among geologists.
Mass spectrometry in the study of advanced glycation processes, responsible for long‐term diabetes complications
Authors: Lapolla Annuniziata , Fedele Domenico , Seraglia Roberta , Traldi Pietro , Vékey Kàroly
Published: May 2005

Mass spectrometry has been usefully employed in the study of the products arising from in vitro and in vivo glycation of proteins. In particular, daughter‐ion spectroscopy has led to an easy detection of 2‐(2‐furoyl)4‐(5)2(furanyl)1‐H‐imidazole in HCI‐hydrolysed glycated albumen and polylysine and the method has allowed us to exclude the presence of the same molecule in in vivo glycated proteins. parent‐ion spectroscopy has been successfully employed in the identification of furoyl‐containing compounds, which are possibly responsible for the results obtained with other analytical approaches.
Calibration and mass measurement in negative‐ion fast‐atom bombardment mass spectrometry
Authors: Sim P. G. , Boyd R. K. , Bertrand M. J.
Published: May 2005

The problem of acceptable accuracy in mass calibration for fast‐atom bombardment (FAB) mass spectrometry has recently received some attention (K. Véekey, Rapid Commun. Mass Spectrom., 2, 213 (1988); Idem., Org. Mass Spectrom., 24, 183 (1989). We describe here a calibration method for negative‐ionFAB, using gold cluster ions, which provides facile mass calibration over the range from can 200u to 10000u. Under suitable conditions, it is possible to use these ions as internal standards for accurate mass measurement.
Mass spectrometry of macrocyclic compounds
Authors: Kiremire Bernard , Seraglia Robert , Traldi Pietro
Published: May 2005

The mass spectrometric behaviour of more than 60 different macrocyclic compounds is reviewed in detail with the aim of depicting general fragmentation pathways, well‐related to the different structural classes. In general, the electron‐ionization‐induced decomposition is characterized by the ejection of single molecules characteristic of the macrocycle. [M + H]+ and [M/2 + H]+ ions are always encountered due to the intrinsic basicity of such molecules.
Direct molecular weight determination of resin‐bound oligopeptides using 252Cf plasma‐desorption mass spectrometry
Authors: Van Veelen P. A. , Tjaden U. R. , Van Greef J. Der
Published: May 2005

Plasma‐desorption mass spectrometry is proved to be capable of the direct molecular weight determination of totally protected resin‐bound oligopeptides. The molecular weight measured is the molecualr weight of the fully protected oligopeptide including the molecular weight of the linker, which connects the oligopeptide and the polystyrene resin. This method makes it possible to check the success of (a step in) the synthesis of a peptide before its deprotection or cleaving from the resin. This can made it a strong tool in the analysis of resin‐bound oligopeptides.
Analysis of human pictuitary growth hormone and its charge varriants by fast‐atom bombardment mass spectrometry
Authors: Silberring Jerzy , Brostedt Peter , Ingvast Ander , Nyberg Fred
Published: May 2005

There is evidence that even highly purified preparations of human growth hormone are not homogenous, but contain charge as well as size variants. The charge heterogeneity was suggested to be due to deamidation of the native hormone. To verify this we have applied peptide mapping followed by fast‐atom bombardment mass spectrometry (FAB‐MS), in order to identify fragments containing the altered amino acids. Growth hormone was purfied from human pituitaries and the differently charged forms were separated by column electrophoresis in agarose suspension. The isolated components were treated with trypsin and analysed directly by FAB‐MS without prior separation by reversed‐phase high‐performance liquid chromatography (RP‐HPCL). Using this technique, approximately 80% of the normone structure was recovered and two deamidation sites were found in the fragment T15 (FDTNSHNDDALLK). The results clearly elucidated the potential use of FAB‐MS for the fast secreening of other variants of the growth hormone which are known to exist.
The use of 4‐hydroxybenzenesulfonic acid as a reduction‐inhibiting matrix in liquid secondary‐ion mass spectrometry
Authors: Visentini J. , Nguyen P. M. , Bertrand Michel J.
Published: May 2005

The use 4‐hydroxybenzenesulfonic acid as reduction‐inhibiting and general purpose matrix in fast‐atom bombardment liquid secondary‐ion mass spectrometry (FAB/LSIMS) is discussed. Results obtained in a comparative study using the disulfide‐bridge containing peptide deaminoarginine‐vasopressin and several commonly used matrices indicate that the reduction‐inhibitaing efficiency of 4‐hydroxybenzenesulfonic acid is comparable to that of 3‐nitrobenzyl alcohol while recuction is found to be important in matrices such as thioglycerol and glycerold. Experiments conducted on peptides such as met‐enkephalin and bradykinin, nucleosides and other polar compounds reveal that 4‐hydroxybenzenesulfonic acid is a good solvent and has physical properties which are similar to those of glycerol. This new matrix material is a radical scavenger, surface active, allows persistent secondary‐ion beams and produces a low background signal. The matrix, 4‐hydroxy‐benzenesulfonic acid, generally yields high quality mass spectra which compare well with those obtained in either glycerol or 3‐nitrobenzyl alcohol.
Location of double bonds using the formal addition of CCI2
Authors: Purghart V. , Hocart C. H. , Schlunegger U. P.
Published: May 2005

A new method for locating double bonds in olefins and fatty acid is described. The CCI2 moiety, derived form chloroform, was added across the double bonds of a series of compounds using a phase‐transfer reaction. The resulting adducts were then analysed by gas chromatography/positive‐ion electron ionization mass spectrometry. It was found that it is routinely possible to locate a single double bond in a molecule at the microgram level. The method proved, however, to be of no use in locating terminal double bonds or in distinguishing geometrical isomers. It is possible that the method might be extended to di‐olefins.
A matrix‐assisted laser desorption time‐of‐flight mass spectrometer based on a 600ps, 1.2 mJ nitrogen laser
Authors: Chevrier Marc R. , Cotter Robert J. , Roepstorff P.
Published: May 2005

The design and Performance of a short‐pulse UV laser desorption time‐of‐flight mass spectrometer is described. The instrument combines the advantages of a 600 ps, 337 nm Pulsed nitrogen laser with a compact, high‐voltage extraction linear time‐of‐flight analyzer. A number of peptides and proteins have been analyzed to demonstrate senstivity, high mass range, resolution and mixture analysis.
Investigation of products arising from enzymatic digestion of advanced glycated albumin by high‐performance liquid chromatography/mass spectrometry
Authors: Lapolla A. , Gerhardinger C. , Baldo L. , Crepaldi G. , Fedele D. , Porter C. J. , Seraglia R. , Favretto D. , Traldi P.
Published: May 2005

The structural investigation of the products arising from 28 days incubation of albumin with high glucose concentration and further enzymatic hydrolysis has been carried out by means of high‐performance liquid chromatography/mass spectrometry (HPLC/MS) under plasmaspray conditions. By this approach many different compounds have been detected, and for most of them, possible structures have been proposed on the basis of literature data and molecular weight assignments.
Modelling coulomb effects in Fourier‐transform ion cyclotron resonance mass spectrometry by charged disks and charged cylinders
Authors: Chen Shu‐Ping , Comisarow Melvin B.
Published: May 2005

A two‐dimensional charged‐disk model is proposed to explain Coulomb‐induced frequencey shifting in Fourier‐transform ion cyclotron resonance (FT‐ICR) mass spectrometry. This model corresponds more closely to the actual FT‐ICR experiment than does the charged‐point model,1 which we recently developed. The model consists of a uniformly charged disk of ions of mass m1, whose excited cyclotron motion is perturbed by a second uniformly charged disk of ions of mass m2, whose cyclotron motion is also excited. By looking in a rotating coordinate frame which rotates at the cyclotron frequency of the first disk, it is seen that the second disk creates an average radial force on the first disk which lowers the cyclotron frequency of the first disk. This radial force is numerically evaluated and found to be a function of the cyclotron radius, the ration of the cyclotron radius to the disk radius, and the charges of the two disks. Unlike the charged‐point model, which was flawed by having an infinite average radial Coulomb force, the average radial Coulomb force for the charged‐disk model is finite. This average Coulomb force allows the use of formulae which permit characterization of a given set of model parameters in terms of an ‘apparent Coulomb distance’, for which a model consisting of point charges with a fixed location in a rotating frame would give the same frequency shift. It is argued that the same ‘apparent Coulomb distance’ would apply for a charged cylinder model, which accounts for Coulomb‐induced line broadening in addition to Coulomb‐induced frequency shifting. It is suggested that the treatment in this paper, together with the use of elongated cells equipped with trapping screens, could permit absolute mass calibrations of T‐ICR spectra.
Ionspray mass spectrometry of marine toxins. III. Analysis of paralytic shellfish poisoning toxins by flow‐injection analysis, liquid chromatography/mass spectrometry and capillary electrophoresis/mass spectrometry
Authors: Pleasance S. , Ayer S. W. , Laycock M. V. , Thibault P.
Published: May 2005

Ionspray mass spectrometry has been used to monitor the purification of saxitoxin, the parent compound in the family of toxins responsible for paralytic shellfish poisoning (PSP), from a strain of the dinoflagellate Alexandrium excavatum. Quantitative results obtained by flow‐injection analysis are compared to those obtained by high‐performance liquid chromatography with post‐column oxidation and fluorescence detection. The coupling of liquid chromatography and capillary electrophoresis with ionspray mass spectrometry is described for the separation of mixtures of PSP toxins and the highly potent pufferfish toxin tetrodotoxin. Tandem mass spectrometry is used to provide the structural information, and the ability to distinguish isomeric PSP toxins both chromatographically and mass spectrometrically is demonstrated.
Identification of cyclobutane‐type dimers of substituted cinnamic acids by gas chromatography/mass spectrometry
Authors: Stewart D. , Robertson G. W. , Morrison I. M.
Published: May 2005

Substituted cinnamic acids were dimerized, under fluorescent or UV light, as a glassy coating on a vial then subsequently analysed by GC/MS. Mass Spectrometric analysis of the dimers formed by each acid allowed the assignment of the dimer as a truxillic or truxinic structure since these structures had distinctive fragmentation patterns; the breakdown of the truxillic acids involves a McLafferty rearrangment before fragmentation occurs, whereas the truxinic acids, which have both carboxy groups on one side and both aromatic groups on the other, fragment asymmetrically to give characteristic stilbene and dicarboxylate fragments. It is apparent from the results of the dimerization of the lcinnamic acids that, under the conditions used here, if the monomeric acid had the capacity for hydrogen bonding using the ring substituent as well as the carboxy group, the dimerization products would be overshelmingly truxillic in structure. However, if only the carboxy group could hydrogen bond, the products would be almost exclusively traxinic in structure.
Molecular weight determination of ferrocenyl‐aryl‐plumbanes by 252Cf plasma‐desorption combined with a linear and reflecting time‐of‐flight mass spectrometer
Authors: Allmaier G. , Roepstorff P. , Schwarzhans K. E. , Utri G.
Published: May 2005

A study of the analytical potential of 252Cf plasma‐desorption mass spectrometry for the melecular weight determination of metallocene complexes isreported. Two ferrocenyl‐phenyl‐plumbanes were successfully analysed in the positive‐ as well as the negative‐ion mode using this method. The positive‐ion mass spectra in particular provided molecular weight information and gave structurally informative fragment ions of this organometallic material. Salinples were deposited by the classical electrospray technique on aluminized targets. The molecular‐ion regions were recorded both on a liner and a reflecting time‐of‐flight instrument. The isotopic pattern of the molecular ions obtained by the reflecting mass spectrometer was compared with the theoretically calculated values and showed excellent agreement.
Structure interconversion in isomeric guanine derivatives at elevated sample temperature
Authors: Kralj B. , Kramer V. , Žigon D. , Kobe J. , Plavec J.
Published: May 2005

Guanine derivatives were examined using the tandem mass spectrometry (MS/MS) method. Isomeric structure differences were explored by means of the unimolecular decomposition spectra of the common ion m/z 151 having the empirical formula of the guanine molecular ion. An interconversion of the isomeric structures as the sample temperature is gradually raised, was observed.
Peptide sequencing by matrix‐assisted laser‐desorption mass spectrometry
Authors: Spengler Bernhard , Kirsch Dieter , Kaufmann Raimund , Jaeger Ernst
Published: May 2005

A novel method of peptide sequencing by mass spectrometry is described. Metastable decay of laser‐desorbedions, taking place in the first field‐free drift region of a reflectron time‐of‐flight mass spectrometer, has been monitored to get structural information from larger peptides. Fragment ions from metastable decay are mass analysed by adjusting the potentiaals of the ion reflectron according to the kinetic energies of the ions. The features of the technique and its significance for future applications are outlined.
Determination of the acyl moieties of the antibiotic complex A40926 and their relation with the membrane lipids of the producer strain
Authors: Zerilli Luigi F. , Edwards Duncan M. F. , Borghi Angelo , Gallo Gian G. , Selva Enrico , Denaro Maurizio , Lancini Gian C.
Published: May 2005

Structures of the fatty acid characterizing the various components of A40926 were determined by gas chromatography/mass spectrometry on the methyl esters obtained by methanolysis of the complex. The results confirm the residues previously assigned to Factor A (n‐Undecanoic acid) and B (10‐methyl‐undecanoic acid) and establish the residues of Factor A1(9‐methyl‐decanoic acid), B1 (n‐dodecanoic acid), RS1 (8‐methyl‐nonanoic acid), RS2 (n‐decanoic acid), and RS3 (n‐tridecanoic acid). As the actinomadura species contain in their mycelia large quantities of C15‐C17 fatty acid residues as membrane phospholipids, these mycelia were saponified and the fatty acids obtained were analyzed as above. There is a close correlation beterrn the fatty acid content of A40923 complex and that of longer homologues in the producer mycelia.
Direct chemical ionization mass spectrometry of short‐chain polysaccharides
Authors: Metzger J. O. , Bruns‐Weller E.
Published: May 2005

Underivatized short‐chain polysaccharides such as two inulins from different plants containing up to 35‐40 monosaccharide units with molecular weights of up to 6500 Da and dextran T 1.5 containing up to 16‐20 monosaccharide units with molecular weights of up to 3200 Da have been investigated by direct chemical lionization. Under soft ionization conditions such as ammonia chemical ionization and reduced ion‐source temperature, it was possible to obtain spectra of the native polysaccharides showing dominant ion series corresponding to ammonia adduct ions of oligosaccharides, and also ion series corresponding to ammonia adduct ions of anhydro‐oligosaccharides.
Secondary‐ion and electron production from surfaces bombarded by large polyatomic ions
Authors: Martens J. , Ens W. , Standing K. G. , Verentchikov A.
Published: May 2005

Heavy molecular ions with energies in the range 10–20 keV and masses from 276 u to 132 000 u, produced by matrix‐assisted laser desorption, were used as primary projectiles to produce secondary‐ion spectra from a variety of surfaces ina tandem time‐of‐fight mass spectrometer. In the negative mode the ratio of electron emission to secondary‐ion emission was found to decrease rapidly with increasing projectile mass. Ion emission was found to dominate for primary ions larger than ∼ 10 000 u. Positive or negative molecular ions and cations were observed from several organic targets of masses up to 1140 u (gramicidin S) for incident projectiles up to mass 132 000 u, i. e., for projectile speeds down to ∼7000 m/s. Other ions characteristic of the target were also observed for these projectiles. Thus, large polyatomic ions can cause secondary‐ion desorption even at very low velocity. The background ions of both polarities are similar to those found in keV particle bombardment by monatomic projectiles. The same ions are observed for all the projectiles; most can be identified with hydrocarbon background. The relative intensities of the background positive ions are largely independent of projectile, and for both polarities the ratio of the ions characterizing the target to those forming the background is approximately constant for all the projectiles. These results strongly suggest that the background ions come from the usual layer of organic impurities attached to the target surface. No direct evidence for surface‐induced dissociation was observed in this mass and energy range.
Protein structural effects in gas phase ion/molecule reactions with diethylamine
Authors: Loo Rachel R. Ogorzalek , Loo Joseph A. , Udseth Harold R. , Fulton John L. , Smith Richard D.
Published: May 2005

The relationship between gas‐phase protein structure and ion/molecule reactivity is explored in comparisons between native and disulfide‐reduced aprotinin, lysozyme, and albumin. Reactions are performed in the reactions with equal concentrations of diethylamine, multiply protonated molecules generated by electrospray ionization (ESI) of ‘native’ proteins shifted to lower charge states than did multiply protonated molecules from ESI of the disulfide‐reduced counterparts, suggesting that the disulfide‐reduced protein ions are less reactive than native protein ions of the same charge state. Differences in reactivity may arise from protonation of different amino acid residues and/or differences in the proximites of charge sites in two molecules. These results suggest that the reactivity of multiply charged proteins can be significantly affected by their gas‐phase structure.
Modification of a commercial thermospray interface controller to improve ion‐current stability
Authors: East Philip B. , Eckers Christine , Haskins Neville J. , Hare John F. , James Phillip J.
Published: May 2005

The stability of the ion beam in a thermospray interface is largely dependent on the control of the vaporizer temperature. The original time‐proportional vaporizer control circuit provides inadequate temperature stabilization. Modification of the circuit by repositioning the thermocouple amplifier and replacing the time proportional part of the circuit with a phase‐angle controller greatly improves the temperature stability and hence th ion‐current stability. The improvement in performance was demonstrated using terbutaline as a test substance.
Observation of MH+, MO+, MOH+, MH−, MO− and MOH− Ions (M=C60 and C70) in fast‐atom bombardment mass spectra of fullerenes
Authors: Miller Jack M. , Chem Lin‐Zhi
Published: May 2005

C60 and C70 in 3‐nitrobenzyl alcohol and 2‐nitrophenyloctylether have been investigated using both positive‐ and negative‐ion fast‐atom bombardment spectrometry. In addition to the ions, MH+, MO+ and MOH+, and corresponding MH−, MO− and MOH− ions (MC60, C70) other ions were observed in the positive‐ and negative‐ion mass spectra. Collision‐induced dissociations of the MO+ and MOH+ ions produced the fullerene ions, indicating that the oxygen and hydroxyl were connected to the convex external surface of the fullerenes.
Matrix‐assisted laser desorption with ultra‐short laser pulses
Authors: Demirev P. , Westman A. , Reimann C. T. , Håkansson P. , Barofsky D. , Sundqvist B. U. R. , Cheng Y. D. , Seibt W. , Siegbahn K.
Published: May 2005

An excimer pumped dye laser generating ultra‐short (560 fs full width at half maximum, FWHM) pulses in the ultraviolet (UV, 248 nm) and visible (496 nm) spectral ranges is used to desorb protein ions from different matrices. The effects of laser‐light energy and power density on secondary‐ion yields from insulin are reported. These data are compared to data obtained by employing a nitrogen laser (337 nm, 3 ns FWHM). The existence of a threshold energy density for the matrix‐asisted laser desorbtion (MALD) of insulin ions by the ultra‐short pulses is established. This threshold energy is of the same order of magnitude for the two laser systems employed and does not depend on the laser pulse length (the energy deposition time). Thus we demonstrate that the amount of laser energy deposited into the sample, rather than the laser power, is the important parameter in the MALD process.
C60 and C70 fullerene isomers generated in flames. Detection and verification by liquid chromatography/mass spectrometry analyses
Authors: Anacleto Joseph F. , Perreault Hélène , Boyd Robert K. , Pleasance Stephen , Quilliam Michael A. , Sim P. Greig , Howard Jack B. , Makarvovsky Yakov , Lafleur Arthur L.
Published: May 2005

Fullerenes C60 and C70, generated by combustion, have been shown previously to be produced in controlled laminar flames accompanied by other compounds having fullerene‐like characteristics. Analysis of these additional compounds by hith‐performance liquid chromatography, coupled on‐line with mass spectrometry has identified them as isomers of the C60 and C70 fullerenes. The newly observed isomers have characteristic UV spectra and are thermally unstable, undergoing conversion to the more stable fullerenes with a half‐life of about 1 h in boiling toluene (111°C). Isomers of C60 and C70 fullerenes previously have been studied theoretically, but not observed experimentally. The flame‐generated material also contains C60O and C70O compounds, as well as C76 and higher carbon clusters.
Matrix‐assisted laser desorption/ionization of high‐mass molecules by Fourier‐transform mass spectrometry
Authors: Castro John A. , Köster Claus , Wilkins Charles , Cotter R. J.
Published: May 2005

Following the first demonstrations of high‐mass analysis using time‐of‐flight matriz‐assisted laser desorption/ionization (MALDI) techniques by Hillenkamp,1,2 Tanaka3 and their co‐workers, there have been significant efforts in a number of laboratories to adapt the new methodology to Fourier‐transform mass Spectrometry (FTMS). The motivation fsor this research is obvious. Namely, it would be desirable to couple the unparalleled high mass resolution of FTMS4 with the extended mass range proveded by MALDI, paricularly for analysis of polymers and biomolecules. Unfortuanately, Prior to the presnt work, attempts to mate FTMS and MALDI have met with limited success. The highest mass matrix‐assisted laser‐desorption‐FTMS result previously obtained appears to be the unpublished low resolution spectrum of bovine insulin recently reported by russell co‐workers.5 We,6 Campana and co‐workes,7 and Hettich and Buchanan8,9 have had some sucess with MALDI‐FTMS of biomolecules with masses lower than 3000 Da.9 Fruthermore, with single exception of Campana's report of obtaining mass resolutiojn of 5000 for the moleculer ion of melittin,7 such spectra have not displayed high resolution. Here, we report successful development of MALDI‐FTMS, demonstrated with spectra obtained from a variety of high‐mass polymer and biomolecule samples, using 355nm radiation from an excimer‐pumped dye laser for desorption/ionization and sinapinic acid as matrix, Some of these spectra are of much higher mass resolution than is possible with current time‐of flight mass spectrometers.
Negative‐mode electrospray‐mass spectrometry using nonaqueous solvents
Authors: Hiraoka Kenzo , Kudaka Ichiro
Published: May 2005

Nonaqueous solvents suitable for negative‐mode electrospray‐mass spectrometry were investigated. Mixtures of methanol with benzene and with carbon tetrachloride were found to be the best solvents. Negative ions of 10−9 M concentrations of surface‐active agents in these solutions could be detected.
The implementation and application of precursor‐ion scanning using a four‐sector instrument
Authors: Scrivens J. H. , Rollins K. , Jennings R. C. K. , Bordoli R. S. , Bateman R. H.
Published: May 2005

Precursor‐ion scanning, in which all ions that fragment to form a selected product ion are detected, has been implemented on a four‐sector instrument. The various experimental parameters associated with the experiment i.c., prcursor mass range, product and precursor ion resolution, collision energy and mass‐measurement accuracy have been established via a series of experiments, Brief examples of the use of the technique in the characterization of synthetic polymers, quaternary salts and peptieds are described together with the analysis of a mixture of phthalate esters.
Optimization of sample deposition for plasma‐desorption mass spectrometry of peptidoglycan monomers
Authors: Allmair Günter , Caparros Marta Rodriguez , Pittenauer Ernst
Published: May 2005

Three selected peptidogycan monomers isolated from muramidase‐digested Escherichia coli‐sacculus were characterized by positive‐ and negative‐ion 252Cf plasma‐desorption mass spectrometry (PDMS). Dut to the high affinity of sugar moieties towards alkali cations multiple alkali attachment in PDMS can be a problem. Electrospray, nitrocellulose, nitrocellulose sandwich anthracene‐9‐carboxylic acid 3‐(3‐Pyridyl)acrylic acid deposition techniques were evaluated for the degree of (de)proltonation and cationization of the molecular species by sodium and/or potassium. Electrosprayed and nitrocellulose‐deposited samples mainly exhibited intense cationized molecular ion species whereas anthracene‐9‐caboxylic acid‐deposition sample show a similar pattern but with much lower intensity. An extension of the nitrocellulose deposition technique, the so‐called nitrocellulose sandwich sample preparation reduced the aallkali attachment problem for these hydrophilic compounds. Application of the small molecule matrix 3‐(3‐pyridyl)acrylic acid yielded mass spectra with abundant [M+H]+ and [MH]− ions in the positive‐ and in the negative‐ion modes, respectively.
Matrix‐assisted laser desorption using a fast‐atom bombardment ion source and a magnetic mass spectrometer
Authors: Annan Roland S. , Köchling Heinrich J. , Hill James A. , Biemann Klaus
Published: May 2005

A conventional fast‐atom bombardment (FAB) ion source was used to achieve matrix‐assisted laser desorption (MALD) in a high‐mass, double‐focusing, magnetic mass spectrometer. The pulsed ion signals generated by irradiation of a mixture of sample and matrix (2,5‐dihydroxybenzoic acid) with either a XeF excimer Laser (353 nm) or a nitrogen laser (337 nm) were recorded with a focal‐plane detector. A resolution (full‐width at half maximum) of 4500 was achieved at m/z 1347.7 (the peptide substance P), 2500 for CsI cluster ions at m/z 10005.7, and 1250 for the isotope cluster of the small protein cytochrome c (horse) [M+H]+=m/z 12360 (average). Sensitivity is demonstrated with 11 fmol of substance P. A survey scan is taken to prodluce a better signal‐to‐noise ratio. In addition to higher sensitivity and lower matrix interference, lthe advantage of MALD over FAB is the former's lower susceptibility to the presence of salts, and competition between hydrophobic and bydrophilic components of a mixture. This feature is demonstrated by the complete MALD spectrum of a crude partial tryptic digest of spedrm‐whale apomyoglobin, containing 24 peptides, representing the entire sequence of this protein.
Control of ion kinetic energy in ion cyclotron resonance spectrometry: Very‐low‐energy collision‐induced dissociation
Authors: Boering Krisltie A. , Rolfe Joseph , Brauman John I.
Published: May 2005

A novel means of effecting collision‐induced dissociation of molecular ions for use in conjuction with Fourier‐transform ion cyclotron resonance (FT‐ICR) mass spectrometry is reported. Using an electronic circuit external to the ICR hardware and software, ions are continuously acceperated and decelerated over a period of hundreds of milliseconds by rledpreatedly shifting the phase of the radio frequency excitation driving signal by 180°. At low kinetic energies, a succession of collisions which transfer small amounts of energy favors the lowest energy fragmentation pathway and allows ions with large activation energies to fragmentation of n‐butylbenzene cation and by extremely large secondary isotope effects in the dissociation of t‐butoxide‐d6 anion.
Gas‐phase silane oligomerization by the isovalent rare earth ions Sc+, Y+ and Lu+
Authors: Azzaro M. , Breton S. , Decouzon M. , Geribaldi S.
Published: May 2005

The gas‐phase reactions between silane and three isovalent metal ions Sc+, y+ and Lu+ are investigated using a Fourier‐transform ion cyclotron resonance mass spectrometer. In contrast to its carbon analogue methane, silane exhibits very different behaviour towards these three metal ions. Lu+ is unreactive sdtowards silane even with a translational activation of the metal ion. The reaction is slow and endothermic with Sc+. It leads first to the formation of ScH+, and ScSIH, and then to the formation fo ScSiH. Slow sequential reactions are observed with the ion ScSiH to give ScSinH, ScSinH, ScSinH and ScSi up to a value of n=3. By contrast to Sc+, only the emtal silylene ion YSiH is observed in the tirst step of the rapid and exothermic reaction of Y+ with silane. YSiH then undergoes a rapid sequintial reaction to give YSinH and YSinH, ions up to a value of n=7.
High resolution parent‐ion selection/isolation using a quadrupole ion‐trap mass spectrometer
Authors: Schwartz Jae C. , Jaardine Ian
Published: May 2005

The same techniques used to generate high‐resolution mass spectra on a quadrupole ion trap can be used for selection or storage of a very narrow mass window with nearly 100% efficiency.
Extraction and mass spectroscopic characterization of giant fullerences up to C500
Authors: Shinohara Hisanori , Sato Hiroyasu , Saito Yahachi , Izuoka Akira , Sugawara Tadashi , Ito Hiroyuki , Sakurai Tohru , Matsuo Takekiyo
Published: May 2005

A series of very large all‐carbon molecules has been successfully extracted with quinoline from fullerene‐rich carbon soots produced by the vaporization of graphite in a helium atmosphere using the contact are method. The present extracts (black powder) were found not to be soluble either in benzene or toluene, which are normally used as extraction solvents for C60 and C70. The secondary ion mass spectrum (SIMS) of the extracts reveals that they contain a series of even‐numbered gigantic carbon molecules C70+2n (n⩾1) up to at least C500. The SIMS spectra exhibit a remarkably wide distribution of carbon molecules which has a broad maximum at around C130‐C150. The possibility of the isolation of such large carbon molecules, which are possibly fullerenes, is also presented.
The determination of low d5‐phenylalanine enrichment (0.002–0.09 atom percent excess), after conversion to phenylethylamine, in relation to protein turnover studies by gass chromatography/electron ionization mass spectrometry
Authors: Calder A. G. , Anderson S. E. , Grant I. , McNurlan M. A. , Garlick P. J.
Published: May 2005

A gas chromatography/mass spectrometry (GC/MS) method for measuring very low levels of enrichment of d5‐phenylalanine (0.002–0.09 atom percent excess) is described. This method makes it possible to determine the enrichment of amino acid incorporated into tissue protein during studies of protein synthesis in man. Phenylalamine is enzymatically converted to phenylethylamine and the d5‐enrichment is measured in the heptafluorobutyryl derivative by selective‐ion recording under electron ionization conditions. The coefficients of variation for muscle‐protein hydrolysate samples enriched with d5‐phenylalanine at the 0.005 and 0.05 atom percent excess levels were 6.0 and 1.2%, respectively. This precision at low enrichment and the small amount of contrast to the conventional approach which uses GC/MS for plasma amino acids (typically 2–20 atom percent excess) but gas isotope‐ratio mass spectrometry for protein‐bound amino acids, the enrichment of both plasmafree and protein‐bound d5‐phenylalanine can be measured with a single instrument.
The proton bound association of large multifunctional group molecules: Tartaric acid esters
Authors: Honovich J. P. , Karachevtsev G. V. , Nikolaev E. N.
Published: May 2005

The kinetics fo production of proton‐bound dimers of dimethyl‐ and diisopropyl‐tartrate were analyzed were analyzed by the method of initial slopes. From the pressure dependence of the apparent bimolecular rate constatn, the back‐dissociation rate and radiative stabilization of the intermediate excited collision complex was calculated. The back‐dissociation (10.3 and 2.8 × 10 3s−1) and radiative (8.2 and 7.1 s−1) rates are compared to literature values for functionally similar acetone. In contrast to acetone these dimers exhibit a back‐dissociation reaction to regenerate the monomer species. These results can be taken to imply a lower binding energy in these dimers due to steric effects. Competing reactions to form ions of m/z 145 and 235 were also observed for the dimethyl and diisopropyl ester, respectively.
Identification of phospholipid molecular species containing two fatty acyl chains differing by 2 Da by negative‐ion fast‐atom bombardment with mass‐analyzed ion kinetic energy analysis
Authors: Chen Su , Curcuruto Ornella , Catinella Silvia , Traldi Pietro
Published: May 2005

Isomeric glycerophosphatidylcholine molecular species containing fatty acyl chains differing by 2 Da (1‐stearoyl‐2‐oleoyl‐ and 1‐oleoyl‐2‐stearoyl‐sn‐glycero‐3‐phosphocholine) can be identified by the determination of trhe fatty acid chain esterified to the sn‐1 position in the glycerol backbone based on the electric sector voltage differences of [M‐86‐R2COOH]− anions derived from phosphatidic acid parent ions (M minus choline group) produced by negative‐ion fast‐atom bombardment combined with mass‐analyzed ion kinetic evergy analyses. Three volt differences can be observed in the spectra. The study further demonstrates that this approach is also effective in distinguishing such molecular species as isomers of glycerophosphatidic acid, glycerophosphatidyl‐ethanolamine and glycerophosphatidylserine and in characterizing the molecular species, differing by 2 Da, of the bovine brian glycerophosphatidylserine (1‐stearoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphoserine) and the rabbit kidney glycerophos‐phatidylethanolamine (1‐oleoyl‐2‐linoleoyl‐sn‐glycero‐3‐phosphoethanolamine).
High‐performance anion‐exchange chromatography/thermospray mass spectrometry in the analysis of oligosaccharides
Authors: Niessen W. M. A. , van der Hoeven R. A. M. , van der Greef J. , Schols H. A. , Lucas‐Lokhorst G. , Voragen A. G. J. , Bruggink C.
Published: May 2005

The on‐line coupling of high‐performance anion‐exchange chromatography mass spectrometry is described. The system is applied to the analysis of neutral and acidic oligosaccharides obtained by (enzymic) degradation of plant‐cell‐wall polysaccharides. The features, potential and limitations of the method are discussed and exemplified with the analysis of some glucuronoxylan and xyloglycan digests. The system allows rapid molecular‐mass determination of components in oligomer mixtures with 1–10 μg injected amounts.
An approach to the quantiative study of reduction processes occurring in fast‐atom bombardment/liquid‐assisted secondary‐ion mass spectrometry
Authors: Bertrand Michel J. , Visentini J. , Paul G. J. C. , Zidarov D.
Published: May 2005

An Approach which allows the determination of the specific effects of experimental parameters on the extent of reduction observed in fast‐atom bombardment/liquid‐assisted secondary‐ion mass spectrometry (FAB/LSIMS) has been developed. The methodology is based on the isolation of the different components‐background, reduction extent, and isotopic abundances—which contribute to peak intensities in the molecular‐ion cluster. The individual contributions of reduction and background are calculated by an algorithm SRBC (simulated reduction and background calculations) which utilizes a Monte‐Carlo method to optimize the values obtained for these variables. This approach has been used to examine the effects of analyte concentration, primary‐beam energy and beam density on the extent of reduction in FAB/SIMS experiments. The results obtained indicate that the beam energy has no significant effect on the apparent reduction, as measured by the experimental (A+2)/A isotope peak ratio, while analyte concentration and beam density effects are obseerved. However, background and reduction data generated by SRBC demonstrate that in some cases there is little effect of these parameters on the true reduction of the analyte and that the increase in apparent reduction with the variation in these parameters results mainly from an artefact created by an increase in the background signal at lower concentrations and higher beam densities.
The chemistry of transition‐metal ion interactions with cyclohexylamine in the gas phase
Authors: Chen Lin‐Zhi , Miller Jack M.
Published: May 2005

The formation of transition‐metal ion (M+Fe+, CO+, Ni+ and Mn+) complexes with cyclohexylamine (1) in a modified fast‐atom bombardment (FAB) source, and the reactions of various ion/molecule complexes, have been studied by FAB MASS spectrometry combined with metastable ion and collisional activation techniques. Multiples dehydrogenations to produce [(aniline)·M]+ and consecutive [2H2+NH3] elimination to afford [(benzene)·M]+ from 1 prevail for all the metal ions studied. Furthermore, [(1)·][Ni]+ and [(1)2·Co]+ ions underwent an unusual NH3 loss. Relative reactivities of the metal ions and complicated ligand effects are presented.
Chemical synthesis in mass spectrometry: Some examples in the organic, organometallic and polymer fields
Authors: Traldi P. , Catinella S. , Bortolini O. , Vékey Karoly
Published: May 2005

The Potential of conventional mas spectrometers in the synthesis of chemicals by ion/molecule reactions is demomnstrated by acollection of examples in different chemical fields.
Efficient trapping and collision‐induced dissociation of high‐mass cluster ions using mixed target gases in the quadrupole ion trap
Authors: Morand Kenneth L. , Cox Kathleen A. , Cooks R. Graham
Published: May 2005

Heavy target gases (neon, argon, krypton or xenon), when added in small amounts to the helium buffer gas in the quadruple ion trap, improve both the trapping efficiency of cesium iodide cluster ions of high mass‐to‐charge ratio and the internal energy deposition during collision‐induced dussociation experiments.
Pulsed axial activation in the ion trap: A new method for performing tandem mass spectroscopy (MS/MS)
Authors: Lammert S. A. , Cooks R. G.
Published: May 2005

A short DC voltage pulse is applied to one endcap of a quadrupole ion‐trap mass spectrometer to activate trapped ions. High internal‐energy deposition is achieved as evidenced by 91+/92+ peak ratios in excess of 20 for dissociation of the n‐butylbenzene molecular ion.1 The amount of internal energy can be controlled directly by vaarying the amplitude of the pulse. Dissociation efficiencies are less than those typically observed for collision‐induced dissociation in the ion trap and range from 50% at low internal energy deposition to 5% at maximum internal energy deposition.
Sensitivity of fast‐atom bombardment mass spectrometry to various polymorphic forms of cortisone acetate
Authors: Gubskaya A. V. , Boryak O. A. , Kosevich M. V. , Shelkovsky V. S. , Blagoy Yu. P.
Published: May 2005

The present paper discussses non‐traditional possibilities of the applications of mass spectrometry to the detection and study of differences in crystal polymorphic forms. The parameter of fast‐atom bombardment which is sensitive to different polymorphs, namely the rate of the formation of cluster ions of an analyte with the glycerol matrix, was chosen for study. Using as an example the analysis of four different samples of cortisone acetate, varying in their polymorphic forms, treatment procedures, and dispersion of the crystalinepowder, it is shown that the relative intensity of the cluster ion [MGH]+ (where M repressents the analyte and G a molecule of glycerol) differs for two of the polymorphic forms and is the same for one of these forms, whether it is obtained by recrystallization from chloroform or by cryogrinding. Analysis of the time dependences of the [MGH]+ ion intensity allowewd us to detect finer effects in the samples, associated with cryogrinding, namely differences in solubility and presumably, mechanoactivation.