bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fragmentation of the metastable dieckmann ester molecular ion: Loss of carbon monoxide
Authors: Morizur Jean‐Pierre , Martigny Isabelle , Taphanel Marie‐Hélène , Tortajada Jeanine 
Published: May 2005

AbstractThe structure of the ionized enol of methyl 4‐buteneoate ([10]+˙) is proposed for the [M‐CO]+˙ ions from the metastable Dieckmaann ester 2‐oxocyclopentanecarboxylate molecular ion. This proposal is based on a comparison of the metastable‐ion mass spectra and the kinetic energy releases of these ions with the same data of an authentic ion [10]+˙.
Analysis of arachidonic‐acid‐containing molecular species in glycerophospholipid classes from rat kidney by fast‐atom bombardment mass spectrometry
Authors: Chen Su , Mariot Roberta , Kirschner Günther , Favretto Donata , Traldi Pietro 
Published: May 2005

AbstractThe qualitative analysis of the molecular species of phosphatidylinositol, phosphatidylethanolamine, phosphatidylcholine and phosphatidylserine from a rat kidney, by fast‐atom bombardment mass spectrometry after separation and purification by liquid chromatography is described. The present results indicate that a high content of arachidonic‐acid‐containing molecular species within major glycerophospholipid classes is present in this biological sample.
Mass spectral study of 2‐adamantanone
Authors: Srzić Dunja , Vinković Vladimir , Mlinarić‐Majerski Kata 
Published: May 2005

AbstractThe mass spectral fragmentation of 2‐adamantanone has been investigated using its specifically labelled monodeuterated derivatives (in positions 1‐, 4‐exo‐, 4‐endo‐, 5‐ and 6‐) and dideuterated derivatives (in positions 4,4‐ and 6,6‐). The mass spectrum of 2‐adamantanone is generally poor in fragments showing the molecular ion as the base peak, the characteristic m/z 117, 104, 93, 91, 80, 79, 72, 67 and 53 fragments, as well as an unusual loss of water. The mass spectra of deuterated compounds favours the assumption of hydrogen randomization prior to the fragmentation of the molecular ion. In contrast, the formation of [C4H8O]+·, m/z 72 does not involve any major hydrogen scrambling.
Oil/oil correlation based on gas chromatographic/mass spectrometric analysis of polycyclic biomarkers
Authors: Šban M. M. , Jovančićević B. S. , Glumičić T. , Dogović N. 
Published: May 2005

AbstractPolycyclic biomarkers such as steranes, diasteranes and tri‐, tetra‐ and pentacyclic terpanes in the hydrocarbon fraction of oils were studied by gas chromatographic/mass spectrometric (GC/MS) analysis in order to correlate six crude oils. Distribution and abundance of these biomarkers were determined for the samples from the Kikinda, Mokrin (Vojvodina) and Požarevac oil fields (two samples for each oil field). The SIM (single‐ion monitoring) method was used for the analysis of steranes and terpanes. Individual steranes, terpanes and their stereoisomers were identified by the comparison of obtained retention times with those quoted in the literature. On the basis of the results obtained, it can be concluded that the oils from the Kikinda and Mokrin (Vojvodina) fields belong to the same genetic type, while the oil from the Požarevac field belongs to another type. It was also found that the oils from the Kikinda and Mokrin fields were of a higher degree of maturity than the oils from the Požarevac field.
Mass‐analysed temperature‐programmed desorption from glassy carbon
Authors: Laušević M. , Popović A. , Laušević Z. 
Published: May 2005

AbstractThe modification of the glassy carbon surface in contact with AgNO3 solution has been studied using X‐ray diffraction and Brunauer, Emmett and Teller (BET) surface analysis methods. The deposition of metallic silver, confirmed by X‐ray analysis, affected the pore system resulting in a decrease of surface area and pore volume. The thermal decomposition of the surface oxide species resulting in desorption of H2O, CO and CO2 as major gas products has been studied using a temperature‐programmed desorption method combined with a mass spectrometric analysis of the desorbed gases. The desorption energies have been calculated using a peak position method. It has been concluded that the silver deposition on the glassy carbon surface contributes to the increased stability of surface oxide species.
UV‐laser‐induced desorption mass spectrometry of insulin, substance P and A4 amyloid protein fragments from synthetic fibrillary aggregates
Authors: Perera I. K. , Candy J. M. , Håkansson P. , Oakley A. E. , Brinkmalm G. , Sundqvist B. U. R. 
Published: May 2005

AbstractMatrix‐assisted UV‐laser‐induced desorption has previously enabled the molecular weights of non‐aggregated peptides, polypeptides and proteins to be determined using mass spectrometry. We now report that this technique can be used to disaggregate and determine the molecular weights of peptides, polypeptides and proteins, present as β‐pleated sheet fibrillary polymers. It was found that the molecular weights of the individual fibril constituents could be determined at subpicomolar concentrations and at a high accuracy. The unrivalled sensitivity and ability to disaggregate fibrillary proteins show the potential of this technique for characterizing the proteins associated with pathological features which occur in a number of diverse disease states.
Electrospray mass spectrometry of recombinant growth hormones
Authors: Baczynskyj Lubomir , Bronson George E. 
Published: May 2005

AbstractThe electrospray mass spectra of several standard proteins were recorded and their molecular weights determined. These were compared to Literature values obtained by other laboratories. The agreement was quite good. Seven recombinant growth hormones were then investigated by this technique. The determined molecular weights were in agreement with the theoretical values. Differentiation between six of the seven analogs could be made on the basis of the molecular weight determinations. Two of these analogs differed in molecular weight by only 1 Da and the accuracy of the mass measurements was not sufficient for distinguishing these two homologous proteins. The influence of solvent on the mass accuracy determinations was studied. It appears that solvents form clusters with the proteins in the electrospray ionization method. These clusters broaden the peaks corresponding to the multiply charged ions of the proteins and make the detemination of centroids more difficult.
Microstructure of co‐polymers by fast‐atom bombardment mass spectrometry
Authors: Montaudo Giorgio , Daolio S. 
Published: May 2005

AbstractThe assumption on which both the structural analysis of polymers and the sequential of co‐polymers by fast‐atom bombardment mass spectrometry (FAB‐MS) is based, is that the ion detected in the FAB spectra do originate from species already present in the polymeric samples, and that the bombardment by fast atoms does not produce the fragmentation of macromelecules. FAB spectra do not yield direct structural information on large macromolecules, but such information can be deduced from the structural analysis of relatively low molecular weight species. Therefore, in a series of recent studies, FAB‐MS has been used to identify the oligomers formed in the partial degradation of several co‐polymers, and the results obtained have yieled detailed information on the microstructure of the materials investigated.
Negative‐ion fast‐atom bombardment mass spectra of pyrazolylborates with various matrices
Authors: Aubagnac Jean‐Louis , Claramunt Rosa‐Maria , Lopez Conception , Elguero José 
Published: May 2005

AbstractNegative‐ion fast‐atom bombardment mass spectra of pyrazolylborates with various matrices (glycerol, m‐nitro‐benzyl alcohol, magic bullet, tetraethyleneglycoldiethylether) have been studied and compared. Collisionally‐activated dissociation spectra gave information on ion structure.
Properties of matrix‐assisted laser desorption. Measurements with a time‐to‐digital converter
Authors: Ens W. , Mao Y. , Mayer F. , Standing K. G. 
Published: May 2005

AbstractSome properties of matrix‐assisted laser desorptio have been studied using single‐ion‐counting methods and a time‐to‐digital converter. The methods allow examination of the process for irradiances near the reported threshold for observation with a transient recorder. All measurements were made using bovine insulin as a test compound. We presernt direct evidence that an irradiance threshold near 106 W cm−2 exists for ion production, and that the process in a collective effect, either involving a large number of molecular ions (∼104)in a successful event or none at all. Above the threshold, the yield is found to scale with a high power (4th to 6th) of the irradiance. Measurements of initial velocity distributions indicate an axial velocity spread corresponding to ∼50 eV and a radial velocity spread corresponding to ∼2.4 eV. Thus the ejection or extraction mechanism appears to be strongly asymmetric.
Matrix‐assisted laser desorption of large biomolecules with a TEA‐CO2‐laser
Authors: Overberg A. , Karas M. , Hillenkamp F. , Cotter R. J. 
Published: May 2005

AbstractMatrix‐assisted desorption/ionization of large biomolecules with a TEA‐CO2laser with a warelength of 10.6 μm is demonstrated. TEA‐CO2LDI mass spectra are almost identical to those obtained with the Er‐YAG (2.94 μm) infra‐red (IR) laser and very similar to UV‐LDI spectra. Most of the matrices usable for Er‐YAG IR‐LDI have been tested at 10.6 μm with success, and the main features of IR‐LDI e.g., the tendency towards the formation of higher chargers is shown.
Pulse timing and optical interface between a neodymium: Yttrium aluminum garnet laser and a Fourier transform ion cyclotron resonance mass spectrometer
Authors: Liang Zhenmin , Ricca Tom L. , Marshall Alan G. , Ghaderi Sahba 
Published: May 2005

AbstractLaser desprption/ionization combined with pulsed (time‐of‐flight or Fourier transform ion cyclotron resonance) mass spectrometric detection is a powerful technique for analysis of involatile compounds and mixtures. Such experiments were originally conducted with pulsed CO2lasers. Although a pulsed CO2laser can be operated in single‐shot mode, Nd: YAG lasers perform best with multiple flashes for warm‐up before the final Q‐switch output light pulse, thus creating the need to synchronize the desired final laser‐output pulse with the event sequence for mass spectrometric analysis. In this paper, we describe a new and simple interface (both optical and electronic components) between a Continuum (formerly Quantel) Model YG 660A Nd: YAG laser and an Extrel FTMS‐2000 mass spectrometer. The optics are modified from a prior pulsed CO2laser interface from Extrel. Synchronization betweem th Nd: YAG laser and the mass spectrometer event sequence is achieved by means of a simple timing circuit that uses an inexpensive pulsing device and is triggered by pulses generated directly from the Extrel 1280 data system and cell controller, in contrast to the only prior published method that required an auxiliary microcomputer. The present interface method is highly flexible, and makes possible complex sequence events involving laser pulses for e.g.: desorption/ionization of solids; photoionization of gaseous neutrals; and photodissociation and photodetachment of gaseous ions.
Retrosynthesis vs ketene loss in electron‐ionization‐induced decompositions of 1,5‐benzodiocapine, 1,5‐benzodiazepine, 1,5‐benzodithiepine, 1,5‐benzoxazepine and 1,5‐benzoxathiepine
Authors: Bopnsignore Leonardo , Loy Giuseppe , Maccioni Elias , Podda Gianni , Seraglia Roberta , Traldi Pietro , Schlunegger Urs 
Published: May 2005

AbstractThe 70 eV electron ionization mass spectrometry of the title compounds has shown the presence of two concurrent primary decomposition pathway, corresponding to the retrosynthetic process and to CH2CO loss. The yields of the two pathways can be related tothe XCO bond strengths: as the XCO bond becomes weaker, [MCH2CO]+˙ ion formation is favoured.
The analysis of thiocarbamides by gas chromatography/negative‐ion chemical‐ionization mass spectrometry
Authors: Watson D. G. , Bates C. D. , Skellern G. G. , Mairs R. , Martin S. , Brooks C. J. W. 
Published: May 2005

AbstractThiocarbamides were converted to their di‐N‐pentafluorobenzyl (PFB) derivaties and analysed by gas chromatography/negative‐ion chemical‐ionization mass spectrometry with methane as reagent gas. The PFB derivatives of the 2‐thiouracils gave mass spectra in which the ion current was carried largely by an ion arising from [MPFB]−. The derivative was used in the determination of the uptake and metabolism of thiocarbamides by cultures of melanoma cells.
Determination of the amino acid sequence of cystine‐containing peptides by tandem mass spectrometry
Authors: Despeyroux Dominique , Bordas‐Nagy Jozsef , Jennings Keith R. 
Published: May 2005

AbstractA method has been developed for the determination of the amino‐acid sequence of a cyclic peptide containing cystine. It is based on the reduction of the peptide in a reductive matrix prior to ionization by fast‐atom bombardment. The amino‐acid sequence of the resulting linear peptide is then determined by tandem mass spectrometry from the spectrum produced by the collision‐induced decomposition of the [M+H]+ ion of the peptide.
Concerning the formation of C3H3O+ and C4H7+ ions from the cyclohexanone molecular ion
Authors: Lebedev Albert T. , Hayes Roger N. , Bowie John H. 
Published: May 2005

AbstractThe base peak (m/z55, C3H3O+) in the mass spectrum of cyclohexanone is shown to be formed by a number of processes, viz from the molecular radical cation, from [MC2H4]+˙ species, and from an [MC3H6]+˙ ion. The ion C4H (the minor contributor to m/z55) is formed by at least five routes from the molecular ion.
Mass spectral fragmentation patterns of deuterated hexanitrobibenzyl and hexanitrostilbene
Authors: Yinon Jehuda , Fraisse Daniel , Dagley Ian J. , Lifshitz Chava 
Published: May 2005

AbstractMass‐analysed ion kinetic energy (MIKE) spectrometry with collision‐induced dissociation (CID) has been used to study the fragmentation processes of the MH+ ions produced by chemical ionization (CI) of a series of deuterated hexanitrostilbene (HNS) and hexanitrobibenzyl (HNBB) compounds. Typical fragment ions obtained in both groups were due to loss of OR′, 2OR′ and NO2 and due to the cleavage of the CC single bond in HNBB and of the double bond in HNS. In HNS there is a preferential loss of NO. A great similarity was observed between the fragmentation pattern of 2,4,6‐trinitrotoluene (TNT) and that of HNS. In negative‐ion chemical ionization (NCI) the fragment ion which forms the base peak in the mass spectra of the HNS compounds is the [(M/2)+O]− ion, while in the HNBB compounds it is the [M/2]− ion.
Desorption of ions from locust tissues. I. Behaviour of E‐destruxin using positive‐ion fast‐atom bombardment mass spectrometry
Authors: Lange C. , Mulheim C. , Cherton J.‐C. , Cassier P. , Vey A. , Pais M. 
Published: May 2005

AbstractDetoxification of E destruxin in E‐diol‐destruxin in vivo in Locusta migratoria locust is demonstrated using direct fast‐atom bombardment (FAB) mass spectrometry without the need for extraction or purification. Organs and biological fluids are used as biomatrices for the FAB desorption process.
High temperature mass spectrometry in materials research
Authors: Hilpert K. 
Published: May 2005

AbstractVaporization is an important property in materials research since it limits the use of the materials at high temperatures and since valuable thermodynamic data can be determined from vapour pressures. High‐temperature mass spectrometry is the most versatile method for the elucidation of vaporization processes. Numerous results have been obtained. This article describes the fundamentals of the method and gives examples of its application. These examples describe the determination of thermodynamic properties for the gaseous species and condensed phases. The materials considered are salts, alloys and graphitic materials. They are of interest for metal halide lamps, superalloys, and nuclear reactors.
Analysis of bovine β‐casein tryptic digest by continuous‐flow fast‐atom bombardment mass spectrometry
Authors: Jones D. S. , Heerma W. , van Wassenaar P. D. , Haverkamp J. 
Published: May 2005

AbstractLiquid chromatography/fast‐atom bombardment mass spectrometry was used to partially confirm the amino‐acid sequence of the protein, β‐casein. The study demonstrates that the technique is capable of the rapid and accurate identification of peptide fragments from tryptic digests and that chromatograrphic integrity is maintained during the analysis. The power of the technique derives from the ability to determine both the retention time and the molecular weight of the eluting components. Each of the components yields a prominent pseudo‐molecular ion (MH+), the majority exhibiting sufficient fragmentation to confirm their structure unambiguously.
Differentiation of taurochenodeoxycholate from taurodeoxycholate by collision‐induced dissociation of pseudomolecular anions generated by fast‐atom bombardment
Authors: Griffiths William James , Egestad Börje , Sjövall Jan 
Published: May 2005

AbstractThe conjugated bile acids taurochenodeoxycholate and taurodeoxycholate are indistinguishable from analysis of their fast‐atom bombardment spectra. Both the positive‐ and negative‐ion spectra show prominent pseudomolecular ions, but little fragmentation. Collision‐induced dissociation of the negative pseudomolecular ions reveal structural differences between the two isomers which are evident in the resultant daughter‐ion spectra. Thus the two isomers can be differentiated.
An expert system for inferring structures of organic compounds from their mass spectra
Authors: Sridhar M. P. , Menon A. G. , Sastry P. S. , Mathur D. 
Published: May 2005

AbstractDevelopment of an ‘expert system’ for elucidation of structures of acyclic organic compounds is described. An expert system is a computer program that embodies some of the heuristic problem‐solving knowledge of human experts so that it can effectively be used as an aid to decision making. The expert system described in this paper is intended to assist a chemist in arriving at plausible structures, the input data being the mass spectrum, molecular formula and presence (if known) of functional groups. The program generates chemically possible structures for the given molecular formula and can use, where available, the constraints imposed by the mass spectrum of the compound and by any known functional groups. The program makes use of a new algorithm for obtaining a canonical representation of structures and a new heuristic for incorporating constrains of the mass spectrum. This work constitutes a case study of the application of artificial intelligence techniques in chemistry and the material presented highlights this motivation.
Charge‐separation reactions of N2O cations formed by low‐ and high‐energy ionization
Authors: Eland J. H. D. , Murphy V. J. 
Published: May 2005

AbstractTriple and quardruple coincidence charge‐separation spectra of nitrous oxide ionized by single low‐energy photons and by high‐energy electrons are reported. Low‐lying states of the molecular dication, which are populated at all energies, dissociate mainly into ion pairs by two‐body reactions. The reaction producing N++N+O+ is weak at low excitation energy and may occur by a very fast secondary dissociation of intermediate dinitrogen ions. At high energy a major new effect is triple ionization followed by dissociation into three atomic ions. These ion triple produce a significant spurious contribution to the spectrum of ion pairs, and several sorts of pair whih appear at high energy are mainly or entirely artifacts of this type.
Anionic rearrangement in the gas phase. The collision‐induced dissociations of deprotonated 2‐diazo‐2‐cyanoacetamides
Authors: Lebedev Albert T. , Bakulev Vasily A. , Hayes Roger N. , Bowie John H. 
Published: May 2005

AbstractPeak‐width measurements and product‐ion studies show that deprotonated 2‐diazo‐2‐cyanoacetamides and the isomeric 4‐cyano‐5‐hydroxy‐1,2,3‐triazoles fragment through a common intermediate to form (OC3N)− as base peak.
Charge stripping C
Authors: Lifshitz C. , Iraqi M. , Peres T. , Fischer J. E. 
Published: May 2005

AbstractMeasurements of the translational energy loss accompanying the charge‐stripping reactions M++N→M2++N+e− and M2++N→M3++N+e− have been performed for C, C and C, C respectively. The energy nesessary to remove the second electron from Buckminsterfullerene was determined, Q=IE(C→C=12.25±0.5 eV.
Collisional spectroscopy approaches in the characterization of 7‐α‐ and 7‐β‐hydroxycholesterol
Authors: Favretto Donata , Guidugli Federico , Seraglia Roberta , Traldi Pietro , Ursini Fulvio , Sevanian Alex 
Published: May 2005

AbstractHigh‐ and low‐energy collision experiments, by means of double‐focusing and ion‐trap mass spectrometers, respecstively, performed on the M+˙ and [MH2O]+˙ ions of 7‐α‐ and 7‐β‐hydroxycholesterol lead to a clear structural characterization of the two stereoisomers. In particular, the β isomer shows peculiar fragmentation pathways due to interaction between the hydroxyl group in position 7‐β and the hydrogen atom on C(15).
Direct evidence for degradation of esperamicin A1 with thiol confirmed by fast‐atom bombardment mass spectrometry
Authors: Takayama Mitsuo , Nomura Taro , Konishi Masataka 
Published: May 2005

AbstractA degradation of esperamicin A1, which is a potent antitumor antibiotic having DNA‐cleaving activity, was studied by fast‐atom bombardment (FAB) mass spectrometry. It was proved that the degradation easily occurs via the thiol group(s) in the matrix solution and not by a FAB‐induced reaction. It was concluded that from the FAB mass spectra of all non‐volatile compounds, the molecular weight should be determined by using at least two chemically different matrices.
Collision‐induced liquid secondary‐ion mass spectra of oxytocin derivatives. A study of the influence of modifications in the disulfide bond on the adjacent peptide bond cleavage
Authors: Malát Jan , Ubik Karel , Lebl Michal 
Published: May 2005

AbstractThe influence of the inductive effect of modifications in the disulfide bridge in oxytocin analogs on the cleavage of the neighboring peptidic bond was studied. A correlation between the inductive constant of the group in the disulfide bridge and the particular fragment ion abundance was observed.
Fast protein sequence determination with matrix‐assisted laser desorption and ionization mass spectrometry
Authors: Schär Martin , Börnsen K. Olaf , Gassmann Ernst 
Published: May 2005

AbstractMeasurement and identification of digested peptides by matrix‐assisted laser desorption and ionization mass spectrometry (LDI‐MS) is demonstrated. Synthetic human parathyroid hormone, pTH (1–34), with molecular mass of 4117.8 Da was digested with carboxypeptidases Y and B and the seqence of 14 amino acids from the C‐terminus of the peptide was determined by analyzing the molecular mass of the truncated peptides. Furthermore, a tryptic digestion of PTH (1–34) was carried out and a molecular mass map of pTH (1–34) was obtained. With the results of the proteolytic digestion a rapid confirmation of the amino‐acid sequence of the protein was possible. It is shown that the results of the trypitc digestion can be used for the unambiguous identification of the amino acid residues Lys and Arg, which cannot be distinguished with a mass spectrometer because of their equal norminal masses. Several advantages of amino acid sequence determination by the combination of digestion and LDI‐MS are obvious: high sensitivity in the low pmol range, fast digestin time due to high enzyme/substrate rations, quantification is unnecessary because the amino acids are identified by their molecular mass differences, the low chemical expenditure for the digestions and the accuracy of the sequence determination. Measurements with LDI‐MS are fast: sample preparation and the measurement take only a few min. The mass determination and amino acid sequence is completely unimpaired by amino acid contaminations or impurities in the sample. The sensitivity of the method is in the low pmol to fmol range and thus comparable to other analytical methods.