bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure of underivatized branched oligosaccharides by negative‐ion fast‐atom bombardment mass spectrometry
Authors: Garozzo D. , Impallomeni G. , Mantaudo G. , Spina E. , Daolio Sergio
Published: May 2005

We report here a study by negative‐ion fast‐atom bombardment (FAB) mass spectromatry of branched oligosacharides containing a 3‐O glyesidie linkage. Our result show that discrimination of the monosaccharide unit linked in the 3‐O position is made possible by the analysis of the negative‐ion FAB mass spectra. In the mass spectrum of A‐trisaccharide (α‐Fuc1‐2‐(α‐GalNAc1‐3)‐Gal) the peak at m/z 307 can be explained as elimination of a neutral molecule of GalNAc(221 u) from the molecular ion. Also in the mass spectrum of 3‐fucosyllaactose (α‐Fuc1‐3‐(β‐Gall‐4)‐Glc) an intense peak at m/z 323, corresponding to the elimination of the fucose linked at the 3 position of glucose is present. To investigate further the fragmentations of the 3‐O‐linked sugars, the negative‐ion FAB mass spectra of disaccharides have also been studied.
Cation attachment in the analysis of polystyrene and polyethylene glycol by laser‐desorption time‐of‐flight mass spectrometry
Authors: Llenes Christopher F. , O'Malley Rebecca M. , Cotter R. J.
Published: May 2005

Al+, Cr+ and Cu+ gas‐phase ions have found to attach effciently to two polymers, polystyrene and polyethylene glycol (PEG) in laser‐desorption time‐of‐flight experiment, and are shown to be viable alternatives to be commonly used Na+, K+ and Ag+ ions. At high laser powers, in the range 8.0 × 107 to 2.0 × 108 W/cm2, ions can be attached by desorption from a support made of the apporoptite meal. An alternative method is to add the metal ion in the form of a salt containing the metal in the +1 oxidation state, when such salt are available. This method requires lowe laser powers, in the range 2.0 × 107 to 8.0 × 107 W/cm2. The two desorption/attachment methods are characterized by different optiomal time‐delay values for recording of spectra. Polystyrence has been found to have a hight affinity for attachemnt to Al+, Cr+, and Cu+ than to K+, while PEG has ben found to have a hight affinity for K+ than for Al+, Cr+. These preferential attachments are discussed in terms of the hard and soft acids and bases principle.
Black canyons for ions stored in an ion‐trap mass spectrometer
Authors: Eades Donald M. , Yost Richard A. , Cooks R. G.
Published: May 2005

Effects from higher order non‐linear resonances, ‘black canyons’, have been observed for ions stored within the quadrupole ion‐trap mass spectrometer. At specific qz values, higher‐order field effects were observed to cause decreased intensity of chemical ionization (CI) reagent ions, due to ineffcient storage, as well as collision‐induced dissociation. Efects have been observed, whether or not the CI reagent ions are mass‐selected, and exibit increased severity with longer storage times. Previous reports have shown ‘black holes’ due to inefficient storage of product ions in tandem (MS/MS) spectra, but have reported no such effects in normal mass spectra. Without employing resonant excitation, higher‐order field effects were investigated and found to occur continuously along iso‐βz lines for βz = 1/3, 1/2, and 2/3. Described in this paper are the directs from higher‐order fields on ions stored at specific az values, and indirec effects by those ions. Also described in this paper is new evidence for ‘black canyons’ occurring at βz = 1/3 at negative az values.
Gas phase relative proton affinities from selected‐ion flow tube (SIFT) rate constant measurements
Authors: Dotan I. , Iraqi M. , Petrank A. , Lifshitz C. , Viggiano A. A.
Published: May 2005

A new method of measuring equilibrium constants of proton transfer gas phase reactions is proposed. The method is based on measuring only the endothermic direction. The expression developed is: Kkexp(BR)kc/{(kckexp)k′c}, where kexp is the measured rate constant, BR is the branching ratio of the proton transfer channel, kc and k′c are the forward and reverse collision rates. Two reaction systems were measured: the equilibrium between methanol and chloroacetonitrile and the equilibrium between ethanol and acetaldehyde. Both equilibrium constants were calculated by measuring forward end reverse rate constants and by the new method. There is good agreement between the two methods and with previously published values.
Analysis of organic pollutants in air by thermal desorption/gas chromatography/mass spectrometry using a home‐made cryofocusing device
Authors: Pucci Sergio , Raffaeli Andrea , Lazzaroni Raffaello , Salvadori Piero
Published: May 2005

This paper describes a simple and cheap home‐made cryofocusing device useful in thermal desorption/gas chromatography/mass spectrometry (GC/MS) to achive the refocusing of the substances desorbed, in order to us use different flow rates during the desorption time (higher flow rate) and the GC/MC analysis (lower flow rate). Some preliminary results of the qualitative and quantitave determinatino of organic pollutants present in air are also presented. The combinatin used, comprising dynamic adsorption/thermal desorption/cryofocusing/GC/MS, allowed us to reach detection limits in the upper ng/m3 (that is, the upper part‐per‐trillion range) per single component.
Quantitation by fast‐atom bombardment mass spectrometry: Assay of cytidine 3′, 5′ ‐cyclic monophosphate‐responsive protein kinase
Authors: Newton Russell P. , Khan Jalal A. , Brenton A. Gareth , Langridge James I. , Harris Frank M. , Walton Terence J.
Published: May 2005

A protein kinase, stimulated by cytidine 3′, 5′ ‐cyclic monophosphate, is conventionally assayed by monitoring the incorporation of radiolabelled phosphate from adenosine triphosphate into a histone substrate. Here the assay of the protein kinase is carried out by positive‐ion fast‐atom bombardment mass spectrometric analysis of the enzyme incubation mixture after the reaction has been terminated. The data so obtained show good agreement with data obtained by the conventional radiometric assay: the intrinsic advantage of the mass spectrometric assay is the capacity for multiple component monitoring; the ability of the kinase to bind competing cyclic nucleotides togeter with integral adenosine triphosphatase (ATPase) and phosphodiesterase activity can also be assessed.
252Cf plasma‐desorption mass spectrometry of lipid a from Enterobacter agglomerans
Authors: Cole Richard B. , Domelsmith Linda N. , David Connie M. , Laine Roger A. , DeLucca Anthony J. , Promé J. C.
Published: May 2005

Endotoxins from gram‐negative bacteria are believed to be causative agents of byssinosis, an occupational pulmonary disease associated with exposure to cotton dust in textile mills. Lipid A preparations from Enerobacter agglomerans, a gram‐negative bacterium commonly found in cotton and cotton dust, have been analyzed using plasma‐desorption mass spectrometry. Results indicate the existence of at least two lipid A types which differ only by the presence of an additional oxygen atom whose position has been localized to the acyloxyacyl ester‐linked side‐chain of the distal portion of the molecule. The lower molecular weight compound of the two structures has the same molecular weight and presumably the same empirical formula as a well‐characterized lipid A from Salmonella minnesota. The mass spectra of lipid A compounds obtained from S. minnesota and E. agglomerans show strong similarities. Palmitoyl, hydroxymyristoyl, myristoyl, and lauroyl side‐chains which are known to be prest in the former are inferred from spectral evidence to be present in the latter.
C‐terminal sequencing of peptides using electrospray ionization mass spectrometry
Authors: Rosnack Kenneth J. , Stroh Justin G.
Published: May 2005

A low‐flow reactor is described for the on‐line monitoring of peptides digested with carboxypeptidase P by electrospray ionization. Two peptides were analyzed using this technique: glucagon (average MW 3482.8 Da), and apomyoglobin (average MW 16 951.5). Both peptides gave interpretable results. The first 19 amino acids of glucagon were successfully sequenced. Apomyoglobin yielded sequence information to the 30th amino acid with some gaps. At 300 nL/min, 50% of the first 30 amino acids were sequenced and at 1μL/min, 67% of the first 30 amino acids were observed.
Sequence distribution of β‐hydroxyalkanoate units in bacterial copolyesters determined by desorption chemicl ionization mass spectrometry
Authors: Abate Rosaria , Garozzo Domenico , Rapisardi Roberto , Bllistrei Alberto , Montaudo Giorgio
Published: May 2005

The sequence distributions of poly(β‐hydroxyalknoate) copolymers were determined by analyzing oligomers obtaned by the pyrolysis direct‐chemical‐ionization (DCI) mass spectrometry technique. Oligomers up to nonamers were identified and the comparison between the experimental and calculated peak intensities makes it possible to calculate repeating unit compositions and sequence distributions. Comparison with other earlier methods are given.
Disentangling electrospray spectra with maximum entropy
Authors: Ferrige A. G. , Seddon M. J. , Green B. N. , Jarvis S. A. , Skilling J. , Staunton J.
Published: May 2005

Software using maximum entropy (MaxEnt) analysis has been developed, and used to econvolute complete electrospray spectra of protein mixtures. It automatically produces zero‐charge mass spectra on a molecular mass scale, along with probabilistic quantification so that the reliability of features in the spectrum can be ascertained. Because maximum entropy is faithful to the experimental data, the results tend to have improved resolution and signal‐to‐noise ratio. This improved performance, particularly regarding resolution, is demonstrated on a haemoglobin containing two β‐globins separated by 12 Da at m/z 15 867 (0.08%). A separation of 12 Da was previously the closest at which mass measurement of two globins was practicable. Also, two hiherto unresolved β‐globins from a second haemoglobin, separated by 9 Da (0.06%) were resolved by MaxEnt and their masses accurately measured. These are the first results using rigorous MaxEnt analysis in electrospray mass spectrometry.
Capillary column gas chromatography/tandem mass spectrometry verification of chemical warfare agents
Authors: D'Agostino P. A. , Porter C. J.
Published: May 2005

Chemical weapons use, although prohibited by the 1925 Geneva Protocol, has been reported in several armed conflicts including the Iran/Iraq war. The use of these weapons during this conflict and the concern over possible use of chemical warfare (CW) agents during the Persian Gulf war has heightened international awareness and prompted many nations to pursue with incresed vigour the signature of a new Chemical Weapons Convention. The most recent draft of the Chemical Weapons Convention contains a number of provisions aimed at developing a treaty that will enable nations to ensure compliance by all signatory nations. Compliance monitoring will be required in a number of scenarios, including the verification of alleged use, the storage and destruction of chemical weapons stocks and ensuring that industrial sites are not illegally producing CW agents. It follows from this draft treaty that compliance monitoring will require a high level of sophisticated analytical support to ensure the establishment of an enforceable treaty. The United Nations Conference on Disarmament therefore formed a multi‐national Technical Group on Instrumentation to address the analytical challenges confronting signatory nations.
Bimolecular reactions of ˙CH2CH2OCH: A comparison with the chemical properties of CH3CH2OCH and ionized trimethylene oxide
Authors: Kenttämaa Hilkka I. , Kiminkinen L. K. Marjatta , Orlowski Joseph C. , Stirk Krista M.
Published: May 2005

The chemical properties of the distonic radical cation ˙CH2CH2OCH are compared with those of its conventional isomer, ionized trimethylene oxide, and its even‐electron analog, the ethoxymethyl cation (CH3CH2OCH). The rate constants and branching rations have been determined for the gas‐phase reactions of the three ions with several neutral reagents in a dual‐cell Fourier‐transform ion cyclotron resonance device. The reactivity of each ion is found to be quite distinct. Fast electron transfer dominates most of the bimolecular reactions of ionized trimethyleene oxide. The ethoxymethyl cation reacts slowly or not at all with the reagents studied, and the only reaction observed is ethyl cation transfer. The distonic ion ˙CH2CH2OCH undergoes vedry fast reactions with all the neutral reagents, and, in sharp contrast to the other two ions, shows remarkably versatile reactivity. This ion rapidly transfers ionized ethylene to most of the neutral molecules studied. Facile electron transfer occurs with some of the neutral reagents while others abstract a pproton from the ion. Abstraction of a radical by the distonic ion‐a reaction reported earlier for dimethyl disulfide—is not observed for any other reagent.
The stretched quadrupole ion trap: Implications for the Mathieu au and qu parameters and experimental mapping of the stability diagram
Authors: Johnson Jodie V. , Peddeer Randall E. , Yost Richard A. , March R. E.
Published: May 2005

The effect of the radial and axial dimensions on the Mathieu stability diagram (in terms of DC and RF voltages) is discussed with relation to the ‘stretched’ geometry employed in the Finningan MAT quardrupole ion‐trap mass spectrometer (ITMS). Equations are presented for the conversion of the Mathieu au and qu parameters to DC voltages and RF voltages, respectively, and vice versa on the ITMS. A TURBOBASIC program is discussed which will provide data for graphing of a stability diagram in (RF, DC) space. Experimentally determined boundaries of the stability diagram are in good agreement with an approximate model for the stretched trap.
Matrix‐assisted laser desorption/ionization mass spectrometry of nucleic acids with wavelengths in the ultraviolet and infrared
Authors: Nordhoff E. , Ingendoh A. , Cramer R. , Overberg A. , Stahl B. , Karas M. , Hillenkamp F. , Crain P. F. , Chait B.
Published: May 2005

A number of different matrices have been tested and compared for ultraviolet and ubfrared (UV and IR) matrix‐assisted lasedr desorption/ionization (MALDI) of oligodeoxyribonucleotides and mixtures thereof, as well as ribonucleic acids (tRNA from yeast and rRNA from Ecoli). A new technique for removing alkali cations from nucleic acid samples during sample preparation on the sample support is demonstrated. The amount of oligonucleotide sample consumed during a typical measurement in IR‐MALDI‐MS was determined.
High resolution accurate mass measurement of product ions formed in an electrospray source on a sector instrument
Authors: Starrett Anne M. , DiDonato Gerald C.
Published: May 2005

The high resolution accurate mass measurement of product ions formed by collisionally activated dissociation in an electrospray source has been achieved using a reversed‐geometry double‐focusing mass spectrometer and accelerating voltage scans. Accurate mass measurements of product ions from angiotensin I, angiotensin II, leucine enkephalinamide, substance P (1–9) and a synthetic compound of pharmaceutical interest were obtained with an average error of <5 ppm.
Matrix‐assisted laser desorption of peptides and proteins using a quadrupole ion trap mass spectrometer
Authors: Schwartz Jae C. , Bier Mark E.
Published: May 2005

The analytical capabilities of the combination of matrix‐assisted laser desorption with a quadrupole ion trap utilizing ion injection are demonstrated using peptides and proteins with molecular weights up to 43 kDa.
Desorption chemical ionization mass spectrometry of arsenic compounds present in the marine and terrestrial environment
Authors: Cullen William R. , Eigendorf Guenter K. , Pergantis Spiros A.
Published: May 2005

The advantages of desorption chemical ionization mass spectrometry (DCI‐MS) for characterizing arsenic compounds that exist in the environment include the presence in the spectra of recognizable molecular ions as well as structurally characteristic fragment ions. Satisfactory spectra can be obtained with 100 ng arsenic on the DCI filament, making the technique eminently suitable for the investigation of environmental samples.
Thermal surface ionization of quaternary ammonium salts in particle‐beam mass spectrometry
Authors: van der Hoeven R. A. M. , Tinke A. P. , Niessen W. M. A. , van der Greef J.
Published: May 2005

The applicability of thermal surface ionization in liquid chromatography/particle‐beam mass spectrometry is investigated for the analysis of quaternary ammonium compounds. The compounds are mass anlyzed in a filament‐off mode of operation with a particle‐beam interface. An intense signal of the molecular cations is observed, while fragmentation can be induced by gas collisions and characterized using tandem mass spectrometry. A significant gain in signal‐to‐noise ratio in thermal surface ionization relative to electron ionization is observed.
Enhanced mass resolution in a quadrupole ion trap
Authors: Londry Frank A. , Wells Georgy J. , March Raymond E.
Published: May 2005

The versatility of the quadrupole ion trap as a mass spectrometer in which the mass resolution may be varied over a wide range has been demonstrated. Mass resolution of 0.8 × 107 and 1.2 × 107 have been obtained for ions of m/z 414 and m/z 614, respectively, well in excess of the normal value of 3m, where m is the mass of ion. At the highest mass resolution, peak‐widths at half‐maximum are but 52 × 10−6 u. While it has been shown previously that enhanced mass reslution in the quadrupole ion trap can be achieved by reduction of the mass scanning rate, the range of mass resolutions reported here were achieved by reducing the mass scanning rate, in stages, by an overall factor of ca 5.5 × 104.
Fast‐atom bombardment mass spectrometric determination of methyl[1‐(butylcarbamoyl)‐1H‐benzimidazol‐2‐yl]carbamate (benomyl) in wettable powder formulations
Authors: Singh Raj P. , Brindle Ian D. , Jones Timothy R. B. , Miller Jack M. , Chiba Mikio
Published: May 2005

In this Communication we report, for the first time, a direct method for the determination of benomyl (methyl [1‐(butylcarbamoyl)‐1H‐benzimidazol‐2‐yl]carbamate) in wettable powder formulations by fast‐atom bombard‐ment mass spectrometry (FAB‐MS). Solutions of desired concentrations of benomyl were prepared in 5 M hydrochloric acid. The matrix compound, glycerol, was added at 10% (v/v) to these solutions for obtaining FAB mass spectra. The results of the analysis of wettable powder samples, carried out by FAB‐MS, compared well (p > 0.05) with those obtained by reversed‐phase high performance liquid chromatography.
Influence of acetylation on the [M + Na]+ ion formation of simple phenol and aniline compounds under fast‐atom bombardment conditions
Authors: Takayama Mitsuo , Tanaka Yoshiaki , Nomura Taro
Published: May 2005

The influence of acetylation on the formation of sodium adduct [M + Na]+ ions, under fast‐atom bombardment conditions, has been investigated using monosubstituted phenol and aniline compounds. The acetylation of o‐isomers, except for the nitrophenols, highly enhanced the [M + Na]+ ion formation, while m‐ and p‐isomers showed little effect on acetylation except for p‐methoxyphenol and aniline. The favorable effect of acetylation on [M + Na]+ ion formation is explained by the conformational flexibility of COAc and GNHAc functions and the carbonyl oxygen as a cation‐accepting site, which are advantageous for the multisite interaction with a Na+ ion.
Liquid chromatography/mass spectrometry analysis of an enkephalin mixture using an autospec dynamic liquid secondary‐ion mass spectrometer interface
Authors: Woolfitt A. R. , Harbach C. A. J.
Published: May 2005

A mixture of four enkephalins was separated by reverse‐phase high‐performance liquid chromatography combined with dynamic liquid secondary‐ion mass spectrometry. A newly developed screen/wick target made the method sensitive and reproducible.
Electron impact mass spectrometry and metastable ion studies on some 2‐(o‐hydroxyphenyl‐2(3H)‐thiazoline‐imine) and 1,3,4‐thiadiazine derivatives
Authors: Hadjieva P. , Kalcheva V. , Tosheva M. , Danieli B. , Catinella S.
Published: May 2005

The electron‐impact induced mass spectrometric behaviour of nine differently substituted 2‐(o‐hydroxyphenyl)‐2(3H)imino‐4‐thiazolines and one 2‐(o‐hydroxyphenyl)‐imino‐l,3,4‐thiadiazinc has been studied in detail with the aid of accurate mass measurements, linked‐scans for metastable‐ion studies and deuterium‐labelling experiments. The related fragmentation pathways are strongly dependent on the presence of a substituent nitrogen atom in pt, ition 3, which can promote a hydrogen rearrangement process on the inline nitrogen and the further cleavage of the iminic bond. In the case of an arylic substituent, specific fragmentation channels are activated, due to the high stability of the resultant product ions.
An investigation of the precision of isotopic abundances determined by secondary ion mass spectrometry
Authors: Testino Samuel A. , Busch Kenneth L.
Published: May 2005

The precision with which the isotopic abundances of palladium and tin can be measured under secondary ion mass spectrometric (SIMS) conditions typically used for organic compound analysis has been determined. The relative abundances of the isotopic peaks, and their associated standard deviations, vary with the number of scans averaged to achieve a spectrum. A representative spectrum is not obtained until more than 40 scans are averaged. In addition, there is a strong correlation between standard deviation and absolute signal intensity. This relationship can allow one to determine the number of scans that need to be averaged to predict true experimental abundances reliably, based on signal intensities.
Fast‐atom bombardment mass spectrometry in the stereochemical characterization of a new group of C30 nuphar alkaloids
Authors: Bortolini O. , Labianco A. , Curcuruto O. , Traldi P. , Wròbel J. T. , Iwanow A.
Published: May 2005

A new group of thio‐C30 nuphar alkaloids has been obtained from the three main stereoisomers by complete oxidation of the sulphur and both the tertiary nitrogen sites. High‐resolution mass spectrometry and metastable‐ion decomposition analysis were used to distinguish and characterize diastereoisomers.
Generation of large radical ions from oligometallocenes by matrix‐assisted laser desorption ionization
Authors: Juhasz Peter , Costello Catherine E.
Published: May 2005

Non‐polar polymers containing ferrocene, ferrocenylnaphthalene, and ruthenocenylnaphthalene groups in their repeating units were studied by matrix‐assisted laser desorption ionization (MALDI) time‐of‐flight mass spectrometry. Sample preparation for these polymers utilized tetrahydrofuran as solvent and several new matrices such as dithranol, 9‐nitroanthracene, and quinizarin (all of these are anthracene derivatives). By comparing the mass spectra of oligometallocenes recorded with different matrices at different wavelengths (337 nm and 2.94 μm) and laser desorption ionization mass spectra recorded without matrix, it could be verified that the major analyte‐related peaks in the MALDI mass spectra corresponded to the radical molecular ions. Radical ions have not been seen in the MALDI mass spectra of biopolymers such as proteins, peptides, and carbohydrates. Radical formation was demonstrated for samples in the mass range (1 kDa–13 kDa). Even in the presence of potential cationization sites such as methyl ester groups in the repeating units of some polyferrocene samples, MALDI mass spectra were dominated by radical ions of the analyte. Two possible mechanisms for radical formation in MALDI are discussed. Comparison of results with different matrices suggested that the distribution of masses observed in the mass spectra and characterized by the polydispersity index was independent of the matrix, but significant differences (5%) in the average molecular weights of the mass distributions were found.
Carbon clusters from coal‐derived materials
Authors: Herod A. A. , Kandiyoti R. , Parker J. E. , Johnson C. A. F. , John P. , Smith G. P. , Li C.‐Z.
Published: May 2005

The production of carbon clusters (but not fullerenes) from coal‐derived material by the use of laser desorption mass spectrometry is described. Benzo(e)pyrene, a standard polynuclear hydrocarbon found in coal tars, also gave carbon clusters despite using low laser power to avoid pyrolysis of target molecules. Positive‐ and negative‐ion spectra of the standard included carbon clusters. These clusters are formed by the laser energy and can be confused with aromatic hydrocarbons of the same nominal masses. They have no relevance for studies of coal structure.
High‐performance liquid chromatography/mass spectrometry with thermospray lonization of free ecdysteroids
Authors: Evershed Richard P. , Prescott Mark C. , Kabbouh Mohamed , Rees Huw H.
Published: May 2005

High‐performance liquid chromatography/mass spectrometry (HPLC/MS) with thermospray ionization has been applied to the analysis of free ecdysteroids (polyhydroxylated steroids that serve as arthropod moulting hormones). Of a range of analytical conditions that were tested, optimum results were obtained by the use of re versed‐phase HPLC using a methanol + water mixture containing 0.1 M ammonium acetate. The positive‐ion spectra of ecdysteroids showed pseudo‐molecular ions, [M + H]+, and fragment ions corresponding to the sequential losses of hydroxyl groups. The [M + H − H2O]+ and [M + H − H2O]+ ions were the most abundant for all the compounds tested. Ecdysteroids bearing a C‐20 hydroxyl group (e.g. 20‐hydroxyecdysone) showed ions characteristic of cleavage of the side‐chain from the steroid nucleus. This mode of fragmentation was much less obvious in the case of ecdysteroids lacking C‐20 hydroxylation (e.g. ecdysone). Full‐scan mass spectra were readily obtained from 1 μg of free ecdysteroids, while a limit of detection of 5 ng (signal‐to‐noise ratio 3) was attained in the selected‐ion monitoring mode. The application of HPLC/MS to the study of ecdysteroids in biological materials is demonstrated by the analysis of extracts of newly laid eggs of the desert locust (Schistocerca gregaria) and pupae of the cotton leafworm (Spodoptera litoralis).
Gas chromatography/isotope ratio mass spectrometry of leaf wax n‐alkalines from plants of differing carbon dioxide metabolisms
Authors: Rieley Gareth , Collister James W. , Stern Benjamin , Eglinton Geoffrey
Published: May 2005

Individual n‐alkalines isolated from the leaf‐surface waxes of plants utilizings differing photosynthetic pathways were analysed using gas chromatography/isotope mass spectrometry (GC/IRMS), in order to obtain the ratios of 13C to 12 (δ13). Marked differences in the average 13C‐depletion of the n‐alkalines relative to whole leaf tissues were observed (C3 = −7.7‰; C4 = −9.9‰; CAM = −11‰). Additionally, all three metabolic types exhibited considerable differences of 13C‐depletion between n‐alkaline homologues isolated from the same plant.
Resonance ionization mass spectroscopy of atomic products formed by photodissociation of sodium iodide molecules
Authors: Collier J. L. , Telle H. H.
Published: May 2005

The products produced by photofragmentation in a molecular beam of sodium iodide, NaI, are investigated utilizing the technique of resonance ionization spectroscopy for the metal fragment, Na. Time‐of‐flight mass spectra are recorded, as a function of the wavelength of the resonant excitation step, and in dependence of the laser pulse energy. In particular, the appearance of non‐resonantly generated atomic and molecular ions is discussed, highlighting the importance of mass‐selective analysis of the ions formed in the interaction volume of the laser and molecular beams.
A comparative study of theoretical methods for the analysis of high‐resolution double‐charge‐transfer spectra, applied to the ethene molecule
Authors: Andrews S. R. , Parry D. E.
Published: May 2005

The low‐energy electronic states of the ethene dication are investigated theoretically, a comparison being made between the predictions of the ab initio ADC(2) Green's function method and of the recently developed semi‐empirical MSXα method. Both methods provide a consistent unambiguous analysis of the closely‐spaced peak structure recently observed in a high‐resolution double‐charge‐transfer spectrum for the ethene molecule.
Fast‐atom bombardment/mass‐analysed ion kinetic energy spectrometry of inositol phosphates
Authors: Walton Terence J. , Hughes Soraya Y.
Published: May 2005

The application of fast‐atom bombardment mass Spectrometry and collisiorutlly induced dissociation with mass‐analysed ion kinetic energy (CID/MIKE) Spectrometry of representative inositol mono‐, bis‐ and trisphos‐phates is described. Based on their CID/MIKE spectra, inositol polyphosphates containing vicinal phosphate groups could be distinguished from isomers in which adjacent phosphate groups were absent. The potential value of this procedure in studies of the biochemistry of intracellular second messengers is discussed.
New desorption strategies for the mass spectrometric analysis of macromolecules
Authors: Hutchens T. William , Yip Tai‐Tung
Published: May 2005

We present two new desorption strategies for the mass spectrometric analysis of macromolecules. These desorption strategies are based on the molecular design and construction of two general classes of sample ‘probe’ surfaces. The first class of surfaces is designed to enhance the desorption of intact macromolecules presented alone (neat) to the surface; we call this surface‐enhanced neat desorption (SEND). The availability of probe surfaces derivatized with, or composed of, multiple types and defined numbers of energy‐absorbing molecules will facilitate investigations of energy transfer and desorption/ionization mechanisms. The second class of probe surfaces is designed to enhance the desorption of specific macromolecules captured directly from unfractionated biological fluids and extracts; we call this surface‐enhanced affinity capture (SEAC). Use of these new probe surfaces as chemically defined solid‐phase reaction centers will facilitate protein discovery through molecular recognition in situ, and also macromolecular structure analysis through the sequential chemical and/or enzymatic modification of the adsorbed analyte in situ. Specific examples of laser‐assisted SEND and SEAC time‐of‐flight mass spectrometry are presented to illustrate the potential for increased selectivity, analyte detection sensitivity, and mass measurement accuracy.
Comparative study of kinetic energy release distribution in unimolecular and collision‐induced dissociations of molecular ions
Authors: Cho Seung Il , Choe Joong Chul , Kim Myung Soo
Published: May 2005

Even though the kinetic energy release distribution in metastable ion decomposition is known to be useful for the study of ion structure and dissociation mechanism, the same information available from collisionally activated decomposition has not been used widely. One of the main obstacles preventing such a general use is related to the uncertainty in the internal energy content of the parent ion in the latter process. In the present work, a method based on a scaling relation has been developed to circumvent such a difficulty. Validity of the method is tested by applying it to a few well‐known reactions.
Superbases in the gas phase: Amidine and guanidine derivatives with proton affinities larger than 1000 kj mol−1
Authors: Decouzon M. , Gal J.‐F. , Maria P.‐C. , Raczyńska E. D.
Published: May 2005

By building a relative basicity ladder, the current basicity scale (Lias et al., J. Phys. Chem. Ref. Data, 17 Suppl. No. 1 (1988)) has been reexamined in its upper part, and extended for organic compounds (amenable to proton transfer measurements) up to proton affinity, PA = 1050 kJ mol−1. Structural effects involved in superbasicities are briefly discussed and routes to further extension of the gas‐phase basicity scale for organic compounds are proposed.
Investigation of the metabolism of felodipine using on‐line liquid chromatography/UV diode array detection/atmospheric pressure chemical ionization mass spectrometry as a diagnostic tool
Authors: Macrae P. V. , Jones B. C. , Todd J. F. J.
Published: May 2005

The utility of on‐line liquid chromatogaphy coupled to UV diode array detection and atmospheric pressure chemical ionization mass spectrometry for the analysis of microsomal metabolites of felodipine has been investigated. A previously unreported metabolite of felodipine, extracted from male rat microsomes, has been detected using this technique. UV diode array detection has been used to characterize this metabolite as a dihydropyridine metabolite and tandem mass spectrometry data used to assign a structure.
Ionization of C60 (buckminsterfullerene) by electron impact
Authors: Srivastava S. K. , Jong G. , Leifer S. , Saunders W.
Published: May 2005

Utilizing a crosses electron‐beam/molecular‐beam collision geometry, mass spectra of C60 and C70 ions have been obtained for an electron impact energy range of 20 eV to 600 eV. These spectra are dominated by singly and doubly ionized species. The intensity of fragment ions is very weak, which is in agreement with previous observations. Ionization efficiency curves for the formation of C and C have also been obtained near their threshold regions. From these curves, appearance energies (AE) of these ions have been derived. The AE for C is found to be 7.8±0.3 eV, which agrees well with previous measurements. However, our value of 16.4±0.3 eV for the formation of C is much lower than the value of 19.0±0.3 eV obtained by photo‐ionization techniques.
Collision‐induced dissociations of deprotonated peptides. Dipeptides containing methionine or cysteine
Authors: Waugh Russell J. , Bowie J. H. , Gross Michael L.
Published: May 2005

The collisional activation mass spectra of the [M – H]− ions of dipeptides containing Met or Cys show the usual backbone fragmentation allowing the sequence of the peptide to be determined. A methionine residue may be identified by the presence of a pronounced peak resulting from loss of MeSH, while a cysteine residue may be identified by the presence of a peak corresponding to loss of either H2S or (H2S + CO2).
Electron ionization mass spectrometry of spiroepoxides generated from E‐3‐arylideneflavanones
Authors: Lipták Miklós , Dinya Zoltán , Nemes Csaba , Lévai Albert , Patonay Tamás , Vékey Karoly
Published: May 2005

The electron‐impact induced decomposition of some spiroepoxides prepared from E‐3‐arylideneflavanones has been examined by means of low‐ and high‐resolution mass spectrometry, mass‐analysed ion kinetic energy (MIKE) spectrometry and collision‐induced dissociation (CID) experiments. The compounds studied were found to undergo a rearrangement reaction resulting in a very intense odd‐electron ion. The MIKE and CID‐MIKE spectra of this type of ion generated from the unsubstituted epoxide proved to be identical to those of the molecular ion of trans‐stilbene. The isomerization of epoxides to the corresponding carbonyl compounds prior to fragmentation was not observed.
A comparison of the fragmentation patterns of 5‐fluoromethyl‐3,4‐disubstituted isoxazoles and 5‐methyl analogs
Authors: Favretto Donata , Traldi Pietro , Bravo Pierfrancesco , Diliddo Dario , Resnati Giuseppe
Published: May 2005

The influence of fluorine substitution on the fragmentation processes of some substituted isoxazoles has been studied by comparing the electron‐impact‐induced mass spectrometric behaviour of some 5‐monofluoromethyl‐3,4‐disubstituted isoxazoles with that of the corresponding 5‐methyl analogs. Some interesting and unusual cleavages have been detected and a rationale has been developed for them on the basis of metastable ion studies and accurate mass measurements. Evidence has been found of the influence of fluorine in the stabilization of molecular and fragment ions.
Investigation of some thiosulfonate derivatives by means of chemical ionization and tandem mass spectrometry
Authors: Curcuruto O. , Winders J. , Franchi D. , Hamdan M.
Published: May 2005

A number of thiosulfonate derivatives have been investigated by means of ammonia chemical ionization (NH3‐CI), electron impact ionization (El) and mass‐selected collision induced dissociation (CID). For most of the compounds investigated, the NH3‐CI positive‐ion mass spectra exhibit the addition ion, [M + NH4]+, as the dominant species, which implies that the proton affinities of the compounds investigated are less than the proton affinity of NH3. Deviation from true chemical ionization conditions resulted in efficient dissociation of the addition ion to yield substantial amounts of the protomated molecule, [M + H]+. The major fragment ions observed in the EI mass spectra and in the CID spectra indicate the cleavage of the sulfur‐sulfur bond to be more efficient than other competing cleavages. This and other experimental observations are discussed.
Collisions of C and C at fluorinated and non‐fluorinated self‐assembled monolayer films
Authors: Callahan J. H. , Somogyi Á. , Wysocki V. H.
Published: May 2005

We report here the spectra that result when singly and doubly charged buckminsterfullerene ions, C· and C, collide with self‐assembled monolayer films at collison energies ranging from 125 to 320 eV. The surfaces were prepared by the spontaneous assembly of octadecanethiol (CH3(CH2)17SH), perdeuteroeicosanethiol (CD3(CD2)19SH), and 2‐(perfluorooctyl)‐ethanethiol (CF3(CF2)7CH17CH2SH) on vapor‐deposited gold. The fluorinated surface causes the greatest conversion of kinetic energy into internal energy, more extensive fragmentation of doubly charged buckminsterfullerene C is detected in collisions with this surface than in collisions with the alkanethiolate surfaces.
Short time‐scale observation of an electrospray current
Authors: Charbonnier Florence , Rolando Christian , Saru Florence , Hapiot Philippe , Pinson Jean
Published: May 2005

The design and use of an experimental device for investigating the time‐dependent structure of an electrospray current is described. Various electrolytes, including aqueous solutions, were submitted to electrospray and the instantaneous current intensities were monitored by means of a fast current measurer. The intensity proved discontinuous and roughly periodic in almost every case. By recording the intensity pattern on a fast oscilloscope, an estimate of the ‘period’ was obtained. A typical structure (obtained from a 10 mM NaBr methanolic solution, ‘reduction mode’) consists of series of groups of peaks. The charge per peak is approximately 10−10C and does not change much with the experimental parameters (electrolyte concentration, nature of the solvent, value of the high voltage). The current variation seems to be mainly related to the number of peaks rather than to the heights of the peaks. These results are consistent with commonly observed averaged spray intensities (0.1 to 1 μA) and suggest a pulsed droplet emission frequency of the order of 300 kHz.
On the kinetic energy released upon collision‐induced dissociation of oriented diatomic ions
Authors: Kumar G. Ravindra , Krishnamurthi Vidhya , Mathur D.
Published: May 2005

The kinetmatics of collision‐induced dissociation of oriented singly and doubly charged diatomic molecular ions have been investigated using computer simulation techniques. Asymmetries are predicted in the translational‐energy spectra of forward‐scattered and backward‐scattered fragment ions when dissociation occurs, in those cases where the internuclear axis of the diatomic molecules is oriented along the direction of the incident ion beam. Simulated translational energy spectra are compared with experimental data obtained for dissociation of oriented CO2+ ions in collision with helium atoms.
Oxidation of peptides during electrospray ionization
Authors: Morand Kenneth , Talbo Gert , Mann Matthias
Published: May 2005

[M+H+16]+ ions were observed in the electrospray ionization mass spectra of several synthetic and maturally occurring peptides. Initial results have shown that the appearance of the modification is dependent on the field strength at the electrospray needle and the flow rate of the solution passing through the capillary. Mass spectrometric experiments on peptides showing the +16 Da modification attributed the change to the selective oxidation of either a methionyl, tryptophanyl, or tyrosyl residue present in the peptide. These results were further confirmed by tandem mass spectrometry experiments on prptides with a methionyl residue at either the N‐ or C‐tgerminus, or within the peptide chain. This effect can occur under normal operating conditions and therefore care must be taken in the analysis of samples containing these oxidizable residues. Conversely, the selectivity of the oxidative process may be used to enhance the information obtained from the mass spectrometric analysis. For example, we show results for the analysis of a tryptic digest of the protein myoglobin where the occurrence of the [M+H+16]+ ion is used, along with the molecular weight data, to correctly identify the tryptic fragment.
Use of an on‐line liquid chromatography trapping column for the purification of protein samples prior to electrospray mass spectrometric analysis
Authors: Kay I. , Mallet A. I.
Published: May 2005

A number of reagents, commonly used in protein chemistry and purification, suppress the electrospray ionization signal response of proteins in a concentration‐dependent manner. An on‐line trapping column device has been developed which enables the purification of protein samples containing these reagents, prior to their introduction into the mass spectrometer ion source.
On the mechanisms of electron‐impact‐induced sulfur dioxide elimination from the molecular ions of 4‐nitro‐ and 6‐nitro‐2,1‐benzisothiazoline 2,2‐dioxide derivatives
Authors: Danikiewicz Witold , Wojciechowski Krzysztof , Fokkens Roel H. , Bibbering Nico M. M.
Published: May 2005

It is shown that metastably decomposing molecular ions of the title compounds eliminate sulfur dioxide via two reaction pathways provided that an α‐hydrogen atom adjacent to the heterocyclic ring nitrogen atom is present. One of the channels leads to the initial formation of an o‐azaxylylene ionic species and is associated with the narrow component of the accompanying composite metastable peak. The other channel involvel a multistep pathway which eventually leads to the formation of an aldimine ionic species and which is associated with the broad component of the accompanying composite metastable peak. Collision‐induced dissociation and deuterium‐labelling experiments have provided evidence that the initially generated o‐azaxylylene ionic species, both as long‐lived and as decomposing ions, have rearranged to the aldimine ionic species via a 1,5‐shift of the α‐hydrogen atom adjacent to the heterocyclic ring nitrogen atom.
Recent events
Authors: Favretto Donata
Published: May 2005

Formation of the European Mass Spectrometry Society, Budapest 25 April 1993.
Identification of molecular masses up to 270 000 u in coal and coal‐derived products by matrix‐assisted laser desorption mass spectrometry
Authors: John P. , Johnson C. A. F. , Parker J. E. , Smith G. P. , Herod A. A. , Li C.‐Z. , Kandiyoti R.
Published: May 2005

Molecular masses up to 270 000 u have been observed during matrix‐assisted laser desorption mass spectroscopy on a sample of bituminous coal; the major fraction of desorbed ions appeared between m/z values of 800 and 5000. Similar mass distributions have been found in a coal‐liquefaction extract and a pyrolysis tar. The highest molecular masses identified in this work far exceed previously reported high molecular masses found in coal‐derived products (12 000 u), which were also detected by laser‐desorption mass spectrometry.
A new type of graphite emitter for field ionization/field desorption mass spectrometry
Authors: Kosevich Marina V. , Shelkovsky Vadim S.
Published: May 2005

A new type of field ionization/field desorption (FI/FD) emitter made of graphite is proposed. The method of emitter preparation is based on the observation that, on the fracture‐surface of graphite, fine microcrystallites are exposed, the sharpness of which is sufficient to provide, under conditions of field mass spectrometry, field strength values sufficient for the ionization of molecules by a tunnelling mechanism. The ease of preparation and handling of such graphite emitters is noteworthy. The efficiency of the graphite emitters is illustrated by examples of FI/FD measurements of a number of substances with different physical and chemical parameters, producing M+·, MH+, MCat+, Cat+, MnH+ types of ions. The main advantage of graphite emitters is seen as the possibility of precise control and direct measurement of the emitter temperature, which facilitates the obtaining of mass‐thermograms of thermodegradation and the study of various temperature‐dependent processes. Some specific potentialities of graphite emitters are outlined, namely the feasibility of direct analysis of organic inclusions in emitter material and switching to the surface‐ionization mode.
Electron ionization mass spectra and metastable‐ion studies on some ethylenedithiotetrathiafulvalene derivatives
Authors: Andreu R. , Garín J. , Orduna J. , Savirón M. , Uriel S.
Published: May 2005

Electron ionization mass spectra of ethylenedithiotetrathiafulvalene and some derivatives were studied by accurate mass measurements, metasable analysis and collisional activation. A retro Diels‐Alder reaction involving ethylene extrusion is the most characteristic fragmentation process for these compounds.
Matrix‐assisted laser desorption/ionization Fourier‐transform mass spectrometry of oligodeoxyribonucleotides
Authors: Stemmler E. A. , Hettich R. L. , Hurst G. B. , Buchanan M. V.
Published: May 2005

Conditions for the matrix‐assisted laser desorption/ionization (MALDI) of oligodeoxyribonucleotides at 355 nm, developed using a 3‐Tesla Fourier‐transform ion cyclotron resonance mass spectrometer (FTMS), are reported. Efficient ion trapping and matrix selection are critical to the desorption and detection of oligonucleotides by FTMS. The achievable upper mass limit for the MALDI‐FTMS of bio molecules on our 3‐Tesla system has been extended from approximately 2 kDa to 6 kDa through the use of pulsed‐trapping‐plate ion deceleration techniques. By implementing the deceleration techniques, molecular ions for bovine insulin (MW = 5733.5), an oligodeoxythymidylic acid, pd[T]10(MW = 3060.0), and a mixed‐base 12‐mer (MW = 3611.5) have been measured. For the analysis of oligonucleotides by FTMS, selection of an appropriate MALDI matrix is essential for the generation of [MH]−ions. 3‐Hydroxypicolinic acid provides a significant improvement over 2,5‐dihydroxybenzoic acid for production of deprotonated molecules particularly for mixed‐base oligomers. MALDI studies using FTMS have been duplicated using a newly constructed time‐of‐flight mass spectrometer (TOFMS) and oligonucleotide fragmentation on the TOFMS is reduced relative to that observed by FTMS. This may be a consequence of the longer times (milliseconds) required for FTMS detection.
Solvation of transition‐metal ion complexes in the gas phase
Authors: Wilson Kimber L. , Buckner Steven W.
Published: May 2005

Solvation of the gas‐phase transition‐metal d0 complexes ScO+, YO+, YCHCN+ and NbO with some protic and aprotic solvents has been studied using Fourier‐transform ion cyclotron resonance mass spectrometry. The relative rate constants for formation of the solvated oxides show strong non‐monotonic fluctuations with increasing extent of solvation. For ScO+ and YO+ the third solvent molecule attaches more rapidly than the second, while for NbO the second attaches more rapidly than the first. This behavior suggests that in spite of the formal d0 character of the metal centers in these systems, simple electrostatic binding is not occurring. In contrast, YCHCN+ shows a continuous decrease in the rate for solvation with up to three molecules of CH3CN. The effects of solvation on the subsequent reactions of the metal oxides has been studied. YO+ solvation (with up to three H2O or two NH3 molecules) does not affect its arene CH bond activation reactions. However, solvation of ScO+ and NbO with one or two NH3 or H2O molecules shuts off benzene dehydrogenation.