bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical archaeology of kava, a potent brew
Authors: Hocart Charles H. , Fankhauser Barry , Buckle David W. 
Published: May 2005

AbstractKava lactones, which are present in the intoxicating Pacific Island drink, kava, have now been detected in a number of archaeological artefacts using selected‐ion monitoring techniques in conjunction with gas chromatography/electron impact‐mass spectrometry. Thus it is now possible to link unequivocally kava drinking, a major aspect of the ceremonial culture of many Pacific societies, to the archaeological record. In addition, a new variation of the kava lactone skeleton was tentatively identified in the form of 7,8‐dihydro‐5,6‐dehydrokawain and 7,8‐dihydro‐5,6‐dehydromethysticin.
Charge‐transfer ionspray liquid chromatography/mass spectrometry analyses of fullerenes and related compounds from flame‐generated materials
Authors: Anacleto J. F. , Quilliam M. A. , Boyd R. K. , Howard J. B. , Lafleur A. L. , Yadav T. 
Published: May 2005

AbstractA flame‐generated, fullerene‐rich material (J. B. Howard et al., Nature 352, 139 (1991)) has been characterized by liquid chromatography coupled on‐line to ionspray mass spectrometry. Charge‐transfer complexation, using a post‐column addition of either an electron donor or acceptor, was utilized as a pre‐ionization technique. Analyses in the positive‐ion mode showed that the thermally metastable constituents of the flame‐generated material, tentatively identified previously (J. F. Anacleto et al., Rapid Commun. Mass Spectrom. 6, 214 (1992)) as fullerene isomers on the basis of atmospheric pressure chemical ionization muss spectrometry, yielded mass spectra consistent with their identification as fullerene adducts with highly uiuaturated moieties CnH2n−4 with n = 5, 6, and 7. The molecular radical cations of these adduct species were susceptible to facile fragmentation yielding the molecular ions of the corresponding fullerenes. The negative‐ion mode experiments failed to provide any information regarding the identity of these metastable constituents.
Charge‐remote fragmentation of bile acids derivatized with amino‐sulphonic acids
Authors: Griffiths W. J. , Zhang J. , Sjövall J. 
Published: May 2005

AbstractNegative‐ion fast‐atom bombardment mass spectra of free and conjugated bile acids are dominated by [M  H]− pseudomolecularions. Collision‐induced dissociations of these pseudomolecular ions give charge‐remote fragmentation patterns which are useful for structural identification. Taurine (2‐aminoethanesulrtionic acid)‐conjugated bile acids have a high cross‐section for charge‐remote fragmentation, and give the most informative and intense spectra among the naturally occurring bile acids. In the present study, collision‐induced dissociation spectra of bile acids derivatized with different aliphatic and aromatic aminosulphonates, and with 2‐amlnoethyl hydrogen sulphate have been compared. All show charge‐remote fragmentation patterns. Determination of the intensities of the fragment ions shows that the highest sensitivity is usually obtained with aromatic aininosulpho‐nate derivatives.
Dilithiated fragments of a monolithiated precursor ion? Unraveling linked scan spectra at constant B/E using labeled lithium ions
Authors: Kiplinger Jeffrey P. 
Published: May 2005

AbstractLiquid secondary‐ion mass spectra of the macrocyclic immunosuppressant rapamycin, ionized from a matrix containing lithium chloride, show intense [M + Li]+ peaks and little or no [M + 2Li − H]+. Linked scanning, at constant B/E, of the [M + Li]+ ion proved difficult to interpret, so a labeling experiment using 6LiCl was performed. Several prominent fragments were observed to contain two lithium ions, and precursor ion scans (constant B2/E) confirmed that these were derived from a metastable [M + 2Li − H]+ precursor. Due to poor precursor‐ion resolution in fragment‐ion scans at constant B/E, mono‐ and dilithiated precursors separated by only 6 u may produce fragments observed in each other's spectra. We find that use of labeled 6LiCl quickly and simply alleviates interpretation problems associated with this effect.
Three structural types of carbon cluster anions and the magic numbers
Authors: Jiao Charles Q. , Phelps Donald K. , Lee Samuel , Huang Yongqing , Freiser Ben S. 
Published: May 2005

AbstractThe distribution of negative carbon clusters, C, is studied in the size range from 4 to 100 atoms using a Smalley compact supersonic source interfaced to a Fourier transform mass spectrometer. Tht mass spectrum of the anion clusters shows three regions which, based on earlier work, can be assigned to three different types of structures: chain, monocyclic and fullerene. The boundaries observed for the three regions in the mass spectrum suggest that the transition from chain to cyclic structure occurs between C and C, and the one from cyclic structure to fullerene occurs in the region of C to C. Magic numbers in the cyclic cluster region are found to be 17, 21, 25, 29 and 33 (n = 4m + l), and in the fullerene region, 60 and 74. Water can react with carbon clusters in the supersonic source to form hydrogenation products followed by electron attachment to give CnH− and CnH (for even n smaller than about 22). With argon as the target gas, only small C (n < 14, except n = 4) are observed to undergo low energy collision‐induced dissociation (CID) yielding mainly C. While CID of CnH− gives C, no product was observed during CID of CnH.
Desorption–ionization and in‐flight fragmentation of monoalkali‐glycine adducts: Plasma‐desorption mass spectrometry and Ab initio calculations
Authors: Bouchonnet Stéphane , Flament Jean Pierre , Hoppilliard Yannik 
Published: May 2005

AbstractInterpretation of 252Cf plasma‐desorption mass spectra of glycine and alkali salt mixtures is correlated to thermochemical values. The interpretation of direct spectra is based on a model considering competitive fragmentations among the ionic bonds involved in the crystalline structure; the desorption yield of Li, Na, K, Rb and Cs alkali‐glycine adduct ions is shown to depend upon the relative lattice energies of the different salts bound in the solid mixture. Ab initio calculations were performed at the 6‐31G*//3‐21G level to evaluate the dissociation energies associated with the in‐flight decomplexation reactions GlyCat+ → Gly + Cat+ (1) for Cat+ = Li+, Na+ and K+ whether we consider that the GlyCal+ desorbed species enter the field‐free area in their ‘preformed geometry’ or that they rearrange during the acceleration step. The experimental metastable transition rates associated with these reactions were determined to be in good agreement with the theoretical values for both GlyCat+ geometries under consideration. We calculated the cation affinities of glycine to be 271 kJ/mol, 188kJ/mol and 127kJ/mol for Li+, Na+ and K+, respectively. The fragmentation of GlyCat+ species into immonium ions, GlyCat+ → [H2N–CH2]+ + CO + HOCat (2), is also experimentally and theoretically investigated. The competition between reactions (1) and (2) is favourable to (2) for Cat+ = H+ and to (1) for Cat+ = Li+, Na+ and K+. From both competitive reactions, the comparison between theoretical values and experimental observations allows one to estimate the average internal energy of the GIyCat+ desorbed species at about 300 kJ/mol in the field‐free area of the mass spectrometer.
Selective elimination of low‐molecular‐weight ions in MALDI‐TOF mass spectrometry using a bipolar pulsed electrostatic particle guide
Authors: Just Craig L. , Hanson Curtiss D. 
Published: May 2005

AbstractThis study addresses a problem inherent in the use of microchannel plates as detectors for matrix‐assisted laser desorption/ionization. We have developed a unique new method of ion transport using fast bipolar pulsing of an electrostatic particle guide to provide ion deflection and enhanced ion transmission. This mode of operation effectively eliminates the intense low‐mass component of the spectrum which normally saturates microchannel ‐plate detectors, while at the same time transporting the higher‐mass component with high efficiency. Enhancement of the resulting signal‐to‐noise ratio has been achieved.
Molecular ion beam method of isotopic analysis: Effect of error propagation, a case study with Li2BO
Authors: Datta B. P. , Khodade P. S. , Parab A. R. , Goyal A. H. , Chitambar S. A. , Jain H. C. 
Published: May 2005

AbstractThe isotopic analysis of boron has been carried out using different pairs of isotopic Li2BO ions as monitors. The precision of the mass spectromctric measurements of different molecular abundance ratios is roughly the same. However, the values of the 10B/11B abundance ratio calculated from the experimental ratios of different pairs of isotopic molecular ions show large variations. These variations are shown to be a logical consequence of the calculation step which leads to the magnification of measurement errors to different extents for different peak ratios. Similar arguments would apply for the isotopic analysis of any element employing the molecular ion beam technique. The effect of isotopic fractionation on the molecular abundances is also discussed. The important implication of the present investigation is that it sets the guidelines for selecting suitable monitor molecules to avoid such errors.
Analysis of taxol and related taxanes from taxus canadensis using liquid chromatography combined with mass spectrometry or tandem mass spectrometry
Authors: Blay P. K. S. , Thibault P. , Thiberge N. , Kiecken B. , Lebrun A. , Mercure C. 
Published: May 2005

AbstractA liquid chromatography/mass spectrormetry (LC/MS) method using nebulizer‐assisted electrospray (ionspray) is described for the analysis of taxol and related taxane analogs in plant extracts from Taxus canadensis. The method used a reverse‐phase liquid chromatography gradient elution which was entirely compatible with the operation of ionspray ionization. Abundant protonated molecules with limited fragmentation were obtained using this ionization technique, and provided adequate sensitivity for monitoring taxol in crude resin extracts. The LC/MS method was evaluated for the analysis of taxol present at levels of 0.2% in resin extracts. Using selected‐ion monitoring, the method provided detection limits of 50 ng/mL. In addition, other taxane analogs were identified in crude resin extracts using liquid chromatography combined with tandem mass spectrometry. Parent‐ion scans for a fragment ion characteristic of the taxane nucleus provided the necessary selectivity and sensitivity for the identification of potentially active diterpenes in complex extracts.
Pyrolysis/gas chromatography/mass spectrometry of lignin from paper‐industry effluents decolorized by trametes versicolor
Authors: Terrón María C. , Martín Carmen , Manzanares Paloma , Galletti Guido C. , González Aldo E. 
Published: May 2005

AbstractThe pyrolysis/gas chromatography/mass spectrometry (PY/GC/MS) results after fungal treatment of paper‐industry effluents suggested a decrease of the relative amounts of lignin pyrolysis products and of the syringyl/guaiacyl ratio, in addition to some oxidation rate of the C3‐alkyl chain in lignin units. The results obtained pointed to the potential of PY/GC/MS for monitoring the extent of fungal modification of lignins by biological systems based on the use of Trametes versicolor.
Mass spectrometric discrimination between per‐O‐acetylated aldopentoses applied to an oligosaccharide
Authors: Blok‐Tip Leonore , Heerma Wigger , Haverkamp Johan 
Published: May 2005

AbstractUnimolecular decomposition spectra of oxonium ions from peracetylated pentoses can be used for identification purposes. The fast‐atom bombardment mass spectra of an oligosaccharide with a pentose residue at the non‐reducing terminus also contain this oxonium ion, which allows identification of this monosaccharide residue by a tandem mass spectrometry experiment. The applicability of this method is demonstrated using a xylopentaose.
A new reduction process in fast‐atom bombardment mass spectrometry: Transformation of an azido group into an amino group
Authors: Aubagnac J.‐L. , Gilles I. , Gosselin G. , Perigaud C. , Labataille P. , Imbach J.‐L. 
Published: May 2005

AbstractA new example of the reduction phenomenon often observed in fast‐atom bombardment mass spectrometry is described, involving the transformation of an azido group into an amino group. This reaction, noticeable with glycerol as a matrix, does not occur with m‐nitrobenzylalcohol.
Taxoid side‐chain structure determination by electrospray ionization tandem mass spectrometry
Authors: Bitsch Francis , Shackleton Cedric H. L. , Ma Wenwen , Park Gary , Nieder Matthew 
Published: May 2005

AbstractA method to elucidate the side‐chain structure of novel taxoids was developed through use of electrospray ionization tandem mass Spectrometry. The intact side‐chain fragments produced by source fragmentation in the atmosphere‐to‐vacuum interface were further dissociated in the collision cell of a triple quadrupole mass spectrometer. The distinctive collisionally induced dissociation mass spectra were remarkably informative and gave detailed information on the side‐chain functionalities. This technique proved valuable in the characterization of new taxoids produced by yew‐tree cell cultures.
The influence of collisional cooling on boundary‐activated decomposition in an ion‐trap mass spectrometer
Authors: March Raymond E. , Londry Frank A. , Fontana Stefano , Catinella Silvia , Traldi Pietro 
Published: May 2005

AbstractWhen the working point of a precursor ion confined within a quadrupole ion trap is moved to the vicinity of a boundary of the stability diagram, fragmentation of the precursor ion can be induced by virtue of energy gained from the radio‐frequency trapping field. This behaviour is known as the ‘border effect’. When the isolated precursor ion is subjected to a cooling period of variable duration, in the presence of helium buffer gas and prior to experiencing the ‘border effect’, a high degree of control of the fragmentation pattern is achieved. The cooling period causes decreases in both ion kinetic energy and ion axial excursions. From this preliminary study, it is suggested that the deposition of internal energy during the ‘border effect’ can be varied by changing the duration of the cooling period. In addition to a degree of control of internal energy deposition, the amount of energy which can be deposited in this manner, though unknown, appears to exceed those energy levels achievable with resonance excitation and the ‘border effect’ without collisional cooling, in that an additional fragmentation channel is accessed.
Matrix‐assisted laser desorption ionization of oligonucleotides with various matrices
Authors: Tang K. , Allman S. L. , Chen C. H. 
Published: May 2005

AbstractFerulic acid, 3‐hydroxypicolinic acid (3‐HPA), and 2,5‐dihydroxybenzoic acid (2,5‐DHB) were used as matrices in MALDI of various oligonucleotides. It was found that 2,5‐DHB is an excellent matrix for polydeoxyribothymi‐dylic acid. A poly‐T oligonucleotidc with a size of 130 bases was successfully detected. 3‐HPA was found to be a good matrix for MALDI of homo‐oligomeric deoxynucleotides as well as those containing four different bases. Parent ions of pd(A)60, d(T)100 d(G)40, and d(C)40 were observed, and a mixed‐base oligonucleotide of 150‐mer was also detected. Polymer ions of poly‐A as large as 420‐mer were measured; however, the efficiency for detecting poly‐T with 3‐HPA as a matrix was slightly worse than when 2,5‐DHB was used. Comparisons of three matrices for various oligonucleotides is also presented.
Characterization of alkyl‐ and aryl‐tins by means of electrospray mass spectrometry
Authors: Jones Tammy L. , Betowski Leon D. 
Published: May 2005

AbstractThe organotins, mainly the trialkyltins and triphenyltins, have a widespread application as fungicides, anti‐fouling coatings for porous and non‐porous surfaces, herbicides, insecticides, and generic biocides. Traditional environmental monitoring methods can only give limited speciation of the organometallics. The speciation of a wide variety of alkyl‐ and aryl‐tin isomers using liquid chromatography coupled with mass spectrometry under positive‐ionization conditions is reported. Detection of the organotins was enhanced by the use of acetic acid in the methanol mobile phase. There were unexpected high‐mass ions with multiple tin‐isotope patterns present in many of the spectra. These high‐mass species were possibly attributable to tin polymers, whose presence has been observed by others using X‐ray methods.
Application of electrospray ionization to the observation of higher fullerene anions
Authors: Fujimaki Susumu , Kudaka Ichiro , Sato Tetsuya , Hiraoka Kenzo , Shinohara Hisanori , Saito Yahachi , Nojima Kazutetsu 
Published: May 2005

AbstractNegative‐ion electrospray mass spectrcmetry for the detection of higher fullerene anions is discussed. The fullerenes were reduced in dimethoxyethane/aromatic solvent using NaK amalgam and analyzed by electrospray ionization mass spectrometry using a double‐focusing mass spectrometer. All the C ions (n = 2k, and k is an integer) could be detected up to n = 102 except for 60 < n < 70 and n = 72. The detection efficiency of C76 is found to be considerably lower than that for C78, probably because the C ion reacts further in solution and is converted to undetectable reaction products. In addition to the fullerene anions, large peaks due to methoxy‐substituted fullerene anions, Cn(OCH3), are observed. The intensities of these ions grow with time.
Low‐energy ion/molecule products from collisions with ammonia
Authors: Morris Michael , Thibault Pierre , Boyd Robert K. 
Published: May 2005

AbstractMultiple clustering of ammonia molecules to triply protonated bovine insulin B chain has been observed in a novel collision cell incorporated as part of a triple quadrupole mass spectrometer. The nature of the phenomenon was examined as a function of both the collision energy and the collision gas thickness in the cell. Increased clustering was observed with higher collision‐gas thickness and lower collision energy. Initial experiments indicate that the number of ammonia molecules clustering to the precursor ion may be dependent on the number of available acidic sites.
Ion‐trap mass spectrometry with an inductively coupled plasma source
Authors: Barinaga Charles J. , Koppenaal David W. , McLuckey Scott A. 
Published: May 2005

AbstractA new mass spectrometry technique using an inductively coupled plasma (ICP) ionization source and an ion‐trap mass spectrometer (ITMS) detector is described and evaluated for elemental and isotopic analysis. Initial results obtained with the ICP‐ITMS technique include sub‐ppb detection of bare ions for, most elements, complete destruction of typical polyatomic matrix ions (e.g., CIO+, ArO+, and ArCl+), and effective neutralization of strong Ar+ ion currents. The latter effects allow observation of clearer mass spectra at m/z < 80 and potentially improved detection of ‘problem’ elements in ICP‐MS (e.g., K, Ca, V, Fe, As, and Se). Formation of poly‐oxide and ‐hydroxide ions of metals with high oxide bond strengths were observed and require system modifications to alleviate.
Determination of substituent effects on the proton affinities of natural nucleosides by the kinetic method
Authors: Liguori Angelo , Napoli Anna , Sindona Giovanni , Cooks R. G. 
Published: May 2005

AbstractThe kinetics of the unimolecular dissociations of proton‐bound dimers produced by fast‐atom bombardment from nucleosides and reference amines enables the evaluation of the proton affinities (PA) of ribonucleosides. The PAs of cytosine, guanosine, adenosine, uridine and deoxyuridine have been thus determined. These values and those already available for the corresponding DNA homologues allow the evaluation of the effect of the hydroxyl group in position 2′ of the sugar moiety, which lowers the PAs of RNA nucleosides by 0.6–1 kcal/mol, and of the methyl group in position 5 of the thymine ring which enhances the basicity of deoxythymidine over deoxyuridine by 0.6 kcal/mol.
First Fourier‐transform ion cyclotron resonance signals of very highly charged atomic ions
Authors: Beiersdorfer P. , Beck B. , Elliott S. , Marrs R. , Schweikhard L. 
Published: May 2005

AbstractWe report on the first application of Fourier‐transform ion cyclotron resonance mass spectrometry to the very highly charged ions produced in the high‐energy electron beam ion trap (SuperEBIT) at the Lawrence Livermore National Laboratory. Initial results are described, and spectra are presented from ions as highly charged as Cs53+.
Probing conformational changes in some proteins by positive‐ion electrospray mass spectrometry
Authors: Hamdan M. , Curcuruto O. 
Published: May 2005

AbstractCharge‐state distributions in the positive‐ion electrospray (ES+) mass spectra of some proteins are monitored at various temperatures of the ion source. The observed shifts in charge‐state profiles favouring higher charge‐states are linked to heat‐induced conformations cited by other research groups. To gain more insight into the origin of the observed shifts, a number of measurements were also performed at different flow rates of the electrospray drying gas, on both aqueous and organic solutions of protein. The flow rate of the drying gas was found to influence the relative intensities of high charge‐states induced by heat or organic solvents to a small extent, but it did not produce substantial shifts in the charge‐state distributions observed in room temperatures ES+ mass spectra of aqueous solutions.
Observation of large multimers in the electrospray ionization mass spectrometry of peptides
Authors: Busman Mark , Knapp Daniel R. , Schey Kevin L. , Smith Richard 
Published: May 2005

AbstractLarge multimeric ions were detected from electrospray ionization (ESI) mass spectrometry of peptides, using a quadrupole mass spectrometer of standard mass range. Multimers, up to heptamers, were seen for angiotensin I; and multimers, up to pentamers, were observed for renin substrate. The appearance of the multimeric species could be controlled by manipulation of sampling conditions in the ESI interface. The relevance of the observation of large multimers to proposed mechanisms of ESI is discussed. Implications of the observation of large multimers to efforts to deduce higher order structure of biomolecules from ESI mass spectrometric experiments are also noted.
Charge‐remote fragmentation of sulphated and glucuronidated bile acids and their 2‐aminoethanesulphonic acid derivatives
Authors: Griffiths William J. , Zhang Jie , Sjövall Jan 
Published: May 2005

AbstractNegative‐ion fast‐atom bombardment mass spectra of bile acids show prominent [M—H]− pseudomolecular ions, and few fragment ions. Collision‐induced dissociation of such pseudomolecular ions gives charge‐remote fragmentations which are useful in structural identifications. It has been shown that bile acids conjugated with taurine (2‐aminoethanesulphonic acid) give more intense and informative collision‐induced dissociation spectra than unconjugated bile acids. In this laboratory, a procedure for the aminosulphation of biological samples, for analysis by tandem mass spectrometry, has been developed. In the present study, a comparison has been made between the collision‐induced dissociation spectra of a series of sulphated and glucuronidated bile acids and their 2‐aminoethanesulphonic acid derivatives.