bluuebunny/crossref_metadata_2025_split huggingface dataset:
Negative‐ion fast atom bombardment and tandem mass spectrometric investigation of phenylpropanoid glycosides isolated from Polygonum pensylvanicum L.
Authors: Sneden A. T. , Zimmermann M. L. , Sumpter T. L. 
Published: May 2005

AbstractInvestigation of the novel phenylpropanoid sucrose esters vanicoside A, vanicoside B and hydropiperoside, derived from Polygonum pensylvanicum L., by negative‐ion fast atom bombardment and tandem mass spectrometry has elucidated collision‐induced decomposition pathways and identified common trends of fragmentation for this class of compounds. The constant neutral loss spectrum of the crude extract of P. pensylvanicum, monitoring the loss of a p‐coumaryl ketene fragment, can be used to identify homologues in the mixture for further investigation. This information can be used to characterize mixtures of this type of compound without the need for derivatization and prior to chromatographic separation, providing a method for guiding the isolation of similar compounds from crude extracts of other plants in the Polygonaceae family.
Gas‐phase nucleophilic displacement reactions
Authors: Olmstead William N. , Brauman John I. 
Published: May 2005

AbstractDisplacement reactions of each of a variety of anionic nucleophiles reacting with each of a variety of neutrals have been studied by pulsed ion cyclotron resonance (ICR) spectroscopy. Rate constants for these reactions are interpreted in terms of a three‐step reaction sequence. RRKM calculations are used to obtain information about the energy of transition states. The origin of the barrier to reaction in solution is discussed.
Assignment of the ions in the electrospray ionization mass spectra of the tryptic digest of the non‐derivatized globin, covering the whole sequence of α‐ and β‐chains: A rapid diagnosis for haemoglobinopathy
Authors: Nakanishi Toyofumi , Kishikawa Masahiko , Shimizu Akira , Hayashi Akira , Inoue Fumio 
Published: May 2005

AbstractFor the rapid and simple identification of haemoglobin variants, tryptic peptides prepared by digestion of the mixture of normal and variant subunits were analysed by electrospray ionization mass spectrometry (ESI‐MS). The globin was not reduced and alkylated. In a single spectrum from the ESI analysis of tryptic digests from normal adult globin, nearly 90 significant peaks were observed. Many of these peaks had the right mass and yielded tandem mass spectra of sufficient quality to define the sequence. Some ion peaks were assigned mainly by mass values with additional indirect evidence. A series of multiply charged ions were observed and these ions were valuable for making the assignments. Ion peaks which were assigned with some degree of certainty covered whole sequence from α‐and β‐subunits. In addition to the normal ion peaks, variant ion peaks were observed in the analysis of tryptic peptides of the non‐derivatized globin mixture from Hb SC double heterozygote and from Hb MBoston heterozygote. This approach will offer routine methods in clinical laboratories.
Simultaneous determination of thromboxane B2, prostaglandin E2 and leukotriene B4 in whole blood by liquid chromatography/mass spectrometry
Authors: Oda Yoshiya , Mano Nariyasu , Asakawa Naoki 
Published: May 2005

AbstractThromboxane B2, prostaglandin E2 and leukotriene B4 were simultaneously extracted from human whole blood without any time‐consuming evaporation or derivatization process, and directly determined by liquid chromatography/ionspray mass spectrometry. In order to obtain high sensitivity and specificity, the chromatographic and mass spectrometric conditions were optimized. Use of the turbo ionspray method plus a microbore column gave excellent sensitivity. A special column‐switching technique allowed the injection of large sample volumes with minimum band broadening. The calibration graphs were linear from a few tens of pg ml−1 to 10 ng ml−1. This simple and rapid method was validated using human whole blood samples to which known amounts of standards had been added. Because the levels of these mediators in biological samples are elevated in some diseases or owing to stimulants, this method is very useful for determining them in such cases.
Site‐specific analysis of the N‐glycans on murine polymeric immunoglobulin A using liquid chromatography/electrospray mass spectrometry
Authors: Kragten Eddy A. , Bergwerff Aldert A. , van Oostrum Jan , Müller Dieter R. , Richter Wilhelm J. 
Published: May 2005

AbstractThe site‐specific distribution of oligosaccharides on murine polymeric immunoglobulin A (pIgA) consisting of two or more immunoglobulin A (IgA) antibodies connected through J‐chain was analysed by liquid chromatography/electrospray mass spectrometry. Glycopeptides from pIgA were localized in a reversed‐phase tryptic peptide chromatogram by collision excitation scanning and their amino acid sequences determined by electrospray tandem mass spectrometry and Edman degradation. Two glycosylation sites on IgA and a single glycosylation site on J‐chain were identified. Using biosynthetic constraints on carbohydrate structures, molecular mass information on the glycan moieties of the glycopeptides was translated into specific carbohydrate structure proposals. The glycopeptide incorporating the single glycosylation site at Asn49 in J‐chain carried fucosylated and non‐fucosylated di‐and triantennary N‐acetyllactosamine type carbohydrate chains terminated by N‐acetyl‐ and/or N‐glycolylneuraminic acid residues. The glycosylation site in the IgA heavy chain at Asn446 contained two oligomannose‐type carbohydrate chains, one carrying five and the other six mannose residues. To the other glycosylation site in the IgA heavy chain at Asn155 one oligomannose structure, hybrid structures with the lactosamine branch terminated by either an additional galactose residue, N‐glycolylneuraminic acid or N‐acetylneuraminic acid, and non‐fucosylated N‐acetyllactosamine‐type structures carrying the same terminating residues were attached. This glycosylation site was present in two separate glycopeptides differing only in their degree of carboxymethylation and yielding identical oligosaccharide distributions, thus providing additional confidence in the assignment method.
A gas chromatographic/electron impact mass spectrometric method for the isolation and derivatization of plasma taurine for use in stable isotope tracer kinetic studies
Authors: Marks L. , Iglicki F. , Rakotoambinina B. , Thuillier F. , Messing B. 
Published: May 2005

AbstractTo aid in the understanding of the human requirement for 2‐aminoethanesulphonic acid (taurine), a method was developed for the analysis of plasma taurine and used for preliminary studies of the kinetics of plasma taurine in three healthy adult volunteers. A gas chromatographic/electron impact mass spectrometric (GC/EIMS) stable isotope ratio method was developed for the measurement of enrichment of the tracer [1,2‐13C2] taurine in plasma. Natural abundance taurine and [1,2‐13C2] taurine were analysed as their N‐pentafluorobenzoyldi‐n‐butylamide (PFB‐dBA) derivatives by GC/EIMS. With the addition of an internal standard, methyltaurine, the taurine concentration could also be measured. After an overnight fast, three healthy adult human subjects were given an intravenous priming dose of [1,2‐13C2] taurine (3 μmol kg−1), which was immediately followed by a continuous infusion of the tracer (3 μmol kg−1 h−1) for 6 h. The mean plasma plateau enrichment was 8.07 ± 0.46 mol% excess (RSD = 5.67%) and a rate of appearance of 34 ± 2.23 μmol kg−1 h−1 was calculated. The plasma taurine concentration was found to be 56 ± 14 μmol l−1. This technique for the assessment of plasma taurine kinetics should enhance the understanding of taurine metabolism as it could be a conditionally essential amino acid in man.
Combined experimental and computational study of the double ionization of ethylamine, propylamine and butylamine to triplet electronic states of their dications
Authors: Andrews Stuart R. , Parry David E. , Harris Frank M. 
Published: May 2005

AbstractVertical double‐ionization energies of ethylamine, propylamine and butylamine molecules to triplet electronic states of their dications were measured by double‐charge‐transfer spectroscopy. The energies to the lowest states of the dications were calculated using an ab initio method with four basis sets. The calculated values predicted fairly well the reduction in the lowest energy observed when the length of the substituted alkyl group increased. Double‐ionization energies to the lowest and higher lying triplet states of the dications were calculated by application of a semi‐empirical form of the multiple scattering Xα method. Even though several spectral peaks may only be identified with transitions to groups of closely lying states, the calculated data gave an insight into the electronic transitions which take place to give the double‐charge‐transfer spectra.
Electron impact‐promoted fragmentation of some substituted 4‐quinazolones
Authors: Badr M. Z. A. , Hammerum Steen , Duffield A. M. 
Published: May 2005

AbstractLow‐resolution mass spectra, and where appropriate complete high‐resolution mass spectra, were recorded for 29 2,3‐disubstituted 4‐quinazolones. Rationalizations are presented for the principal fragmentation modes of this series of aromatic compounds. Four of the 4‐quinazolones which contain a vinyl‐2‐furanyl group attached to C‐2 of the heterocyclic ring exhibited an unusual loss of C3H2O from their respective molecular ions.
Determination of O‐(chloroacetylcarbamoyl)fumagillol (TNP‐470; AGM‐1470) and two metabolites in plasma by high‐performance liquid chromatography/mass spectrometry with atmospheric pressure chemical ionization
Authors: Moore Jeff D. , Sommadossi Jean‐Pierre 
Published: May 2005

AbstractHigh performance liquid chromatography/mass spectrometry using a heat nebulizer atmospheric pressure chemical ionization interface was investigated as a sensitive and selective technique for the chromatographic separation and quantitation of the anti‐angiogenic drug TNP‐470 and its polar metabolites MII and MIV. Upon extraction from plasma, the analytes were measured using selected‐ion monitoring in the positive ionization mode and single quadrapole mass spectrometric detection. A trideuterated 13C‐labeled analog of TNP‐470 was used as an internal standard. Two plasma extraction procedures were evaluated. An acetonitrile precipitation method resulted in a recovery of 65.9% and 44.4% for MIV and TNP‐470, respectively, and a limit of quantitation of 2.5 ng ml−1 with a limit of detection of 0.63 ng ml−1 for both analytes. In contrast, a solid‐phase extraction method led to a higher recovery of 92.9% and 111.0% for MIV and TNP‐470, respectively, and a limit of quantitation of 0.63 ng ml−1 with a limit of detection of 0.16 ng ml−1 for both analytes. Intra‐day and inter‐day precisions were <10% and <18% for both analytes. The solid‐phase extraction, by decreasing plasma interferences present within the column capacity, also allowed the detection and quantitation of MII, a highly polar metabolite of TNP‐470. The recovery of MII in plasma was 77.4% with a limit of quantitation and detection of 2.5 and 1.25 ng ml−1, respectively. Intra‐day and inter‐day precisions were 6.19% and 2.99%. Quantitative analysis of plasma samples from a patient receiving 10 mg m−2 of TNP‐470 by a 1 h intravenous infusion is reported.
Liquid chromatography/thermospray mass spectrometry of mustard and its metabolites
Authors: Munavalli S. , Jakubowski E. M. , Durst H. D. 
Published: May 2005

AbstractThere is considerable interest in the detection and analysis of chemical warfare agents. Since thermospray provides soft ionization and interesting fragmentation patterns under discharge conditions, the liquid chromatographic/thermospray mass spectrometric behavior of bis(2‐chloroethyl) sulfide and its metabolites was investigated. All of the metabolites except mustard sulfone and thiodiglycol sulfone indicated the presence of a three‐membered cyclic sulfonium ion intermediate or its equivalent in their mass spectra. Other observed reactions of the above substrates include polymerizations and nucleophilic substitution reactions.
Direct analysis by electrospray ionization and matrix‐assisted laser desorption ionization mass spectrometry of standard and urinary acylcarnitines. Comparison with fast atom bombardment and gas chromatography chemical ionization mass spectrometry
Authors: Briand Gilbert , Fontaine Monique , Schubert Ralf , Ricart Guy , Degand Pierre , Vamecq Joseph 
Published: May 2005

AbstractA simple method using matrix‐assisted laser desorption ionization mass spectrometry (MALDI‐MS) is described for the characterization of acylcarnitines in standard solutions and urinary samples from controls and patients with β‐oxidation deficiency disorders. This mass spectrometric approach is compared with other techniques currently utilized for studying acylcarnitines: fast atom bombardment mass spectrometry (FABMS), gas chromatography/chemical ionization mass spectrometry (GC/CIMS) and electrospray ionization mass spectrometry (ESI‐MS). MALDI‐MS was found to compare favourably with the recently described ESI‐MS analysis of acylcarnitines. Both ESI‐MS and MALDI‐MS share the following advantages: (i) non‐requirement of a derivatization step; (ii) easy detection of acylcarnitine esters in standard preparations and urinary samples from human subjects; (iii) detection of fatty acid oxidation disorders from the urinary acylcarnitine profiles in patients suffering from medium‐chain acyl‐CoA dehydrogenase deficiency (MCADD), multiple acyl‐CoA dehydrogenase deficiency (MADD) and mitochondrial carnitine palmitoyltransferase type II (CPT II) deficiency; (iv) sensitivity comparable to FABMS and GC/CIMS, the two reference methods most widely utilized for routine detection of acylcarnitines; and (v) ability (like FABMS but in contrast with GC/CIMS) to detect long‐chain acylcarnitines, suggesting that these esters might have been previously underestimated in body fluids from patients with β‐oxidation deficiency disorders. MALDI‐MS, like ESI‐MS, provides a fast and sensitive method for determining carnitine and its esters, with the potential for routine application in neonatal screening for inherited metabolic disorders involving acylcarnitine metabolism.
Decomposition channels alternative to remote‐charge fragmentations observed in mass spectrometry of alkyltrimethylammonium cations
Authors: Bambagiotti‐Alberti Massimo , Coran Silvia A. , Benvenuti Fabrizio , Lonostro Piero , Catinella Silvia , Favretto Donata , Traldi Pietro 
Published: May 2005

AbstractA series of alkyltrimethylammonium cations, generated by fast atom bombardment from 1‐dodecanaminium‐, 1‐tetradecanaminium‐ and 1‐hexadecanaminium‐N,N,N‐trimethyl bromides, were studied by high‐energy collisions and comparison with N,N,N‐trimethyl‐d9 labelled analogues. The results show that, together with remote‐charge fragmentation processes, alkyltrimethylammonium cations exhibit further decomposition pathways which may be explained by interaction between the alkyl chain and the methyl group linked to the nitrogen atom. The sharp interruption of remote‐charge fragmentation at the C‐5 atom was observed for all compounds and explained as due to the formation of an energetically favoured six‐membered cyclic structure.
Regiospecific addition of CH2O at the radical site of the ˙CH2CH2OHCH3+ distonic ion
Authors: Troude V. , Leblanc D. , Mourgues P. , Audier H. E. 
Published: May 2005

AbstractThe reaction of the ˙CH2CH2OHCH3+ distonic ion with CH2O was studied by Fourier transform ion cyclotron resonance spectrometry. The process is induced by an initial regiospecific attack of the carbon CH2O at the radical site of the distonic ion, leading to an intermediate adduct ion which loses water. The mechanism was demonstrated by labelling, by studying the structure of the product ion and by examining independently the behaviour of the putative intermediate radical cation.
Channel noise enhancement in small geometry MOSFET and its influence on phase noise calculation of integrated voltage‐controlled oscillator
Authors: Itoh Nobuyuki , Kojima Kenji , Ohguro Tatsuya 
Published: May 2005

AbstractChannel noise enhancement due to MOSFET scaling and its influence on phase noise estimation of fully integrated VCO have been studied. The channel noise of MOSFET increases due to the hot electron effect of small geometry MOSFET is obvious. The channel noise coefficient,γ, of NMOS is 3.5 for 40‐nm gate length, 2.0 for 90‐nm gate length in spite of being ⅔ for long channels MOSFET. Simultaneously, calculation of phase noise of fully integrated VCO shows large difference usingγ=⅔ because the part of noise performance of VCO gain‐cell depends on channel noise of MOSFET. Calculated phase noise showed good agreement with measured data when the optimum value of channel noise of MOSFET was adopted. Copyright © 2005 John Wiley & Sons, Ltd.
Regulation of microglial behavior by ion channel activity
Authors: Eder Claudia 
Published: May 2005

AbstractMicroglia play an important role in the central nervous system, where these cells, it is believed, have both neuroprotective and neurotoxic effects. In response to acute brain injury or during neurodegenerative and neuroinflammatory diseases, activated microglial cells undergo shape changes, migrate to the affected sites of neuronal damage, proliferate, and release a variety of substances, such as cytokines and reactive oxygen species (ROS). This review summarizes the physiological mechanisms underlying microglial activation and deactivation processes, with particular focus on the involvement of microglial ion channels. Microglial ion channels have been shown to be capable, by regulating membrane potential, cell volume, and intracellular ion concentrations, of modulating or facilitating proliferation, migration, cytokine secretion, shape changes, and the respiratory burst of microglial cells. © 2005 Wiley‐Liss, Inc.
Importance of glutamate‐generating metabolic pathways for memory consolidation in chicks
Authors: Gibbs Marie E. , Hertz Leif 
Published: May 2005

AbstractGlutamatergic and noradrenergic stimulation is essential for formation of memory of single‐trial discriminative avoidance of colored beads in the 1‐day‐old chick. Transmitter glutamate is released soon after training and again before memory consolidation 30 min after training. Memory consolidation is abolished by posttraining injection of iodoacetate, which inhibits glycolysis and thus not only energy metabolism but also pyruvate carboxylase‐dependent glucose conversion to glutamate, needed for consolidation; a similar effect is evoked by the antagonists propranolol acting at β2‐adrenoceptors or SR59230A acting at β3‐adrenoceptors. This paper shows that the effect of these inhibitors can be overcome by central injection of glutamine, providing an alternate source of transmitter glutamate and compensating for the inhibition of glycolysis by iodoacetate or the blockade of adrenergic stimulation of glycogenolysis by propranolol or of glucose uptake by SR59230A. Conversely, inhibition of memory consolidation by methionine sulfoximine (MSO), an inhibitor of glutamine synthetase and thus of the glutamate‐glutamine cycle, essential for neuronal reaccumulation of previously released transmitter glutamate, could be challenged by noradrenaline, stimulating glucose uptake and glycogenolysis and providing glutamate synthesis from glucose to compensate for the lack of return of previously released glutamate. Also, administration of either glutamine or noradrenaline could prevent the spontaneous decay of labile memory 30 min after training on a weakened stimulus, suggesting that direct supply of glutamate from glucose may secure sufficient supplies of transmitter glutamate for release prior to memory consolidation at 30 min. © 2005 Wiley‐Liss, Inc.
Differential regulation of ceramide in lipid‐rich microdomains (rafts): Antagonistic role of palmitoyl:protein thioesterase and neutral sphingomyelinase 2
Authors: Goswami R. , Ahmed M. , Kilkus J. , Han T. , Dawson S.A. , Dawson G. 
Published: May 2005

AbstractCell differentiation and myelination involve a fine balance between stasis and programmed cell death, yet the genes that regulate this have not been clearly defined. We therefore studied two key gene products involved in oligodendrocyte plasma membrane lipid metabolism and their antagonistic role in ceramide‐mediated cell death signaling. Overexpression of palmitoyl:protein thioesterase (PPT1; verified by Western blot of the V5‐tagged protein and increased enzyme activity) resulted in decreased ceramide in the detergent‐resistant microdomain (DRM, or raft) relative to cholesterol and sphingomyelin (SM). This PPT1 overexpression also resulted in protection against cell death induced by either staurosporine or C2‐ceramide. In contrast, overexpression of neutral sphingomyelinase 2 (NSMase2; verified by Western blot of the FLAG‐tagged protein and increased enzyme activity) resulted in increased membrane NSMase and increased ceramide in rafts relative to cholesterol and SM. The difference in SM and ceramide turnover was quantitated by [3H]palmitate pulse‐chase labeling. Furthermore, when NBD‐SM was added to cells, it was hydrolyzed by NSMase‐transfected cells at more than twofold the rate in untransfected cells. NSMase2 overexpression enhanced cell death induced by staurosporine or C2‐ceramide, in contrast to the protective effect of PPT1 overexpression. The presence of a fraction of both PPT1 and NSMase2 in rafts together with their substrates (palmitoylated proteins and SM, respectively) suggests a mechanism for dynamic palmitoylation/depalmitoylation of certain proteins in controlling cell death via NSMase activation. © 2005 Wiley‐Liss, Inc.
Performance, carcass cut‐up and fatty acids deposition in broilers fed different levels of pellet‐processed flaxseed
Authors: Shen Yingran , Feng Dingyuan , Fan Ming Z , Chavez Eduardo R 
Published: May 2005

AbstractThe effects of flaxseed (FS) processing and inclusion levels on broiler performance and fatty acid deposition were examined. FS was provided as whole seed, ground or pellet‐then‐mashed at a dietary level of 0, 12 or 14% during days 1 to 21. These levels represented control, threshold and over‐threshold, respectively. During days 22 to 40, the threshold level was increased to 15%, while the over‐threshold level increased to 17%. After 21 days of feeding, the performance of birds fed a diet with 12% pellet‐then‐mashed FS were comparable (p > 0.05) with those fed mashed control diet, but superior to those fed a diet of whole FS (p < 0.05). There was interaction (p < 0.05) between diet processing and FS level on weight gain, with pellet‐then‐mash processing being more effective at the 12% FS inclusion level than at the 14% level in improving performance. The beneficial processing effect on performance diminished during days 22 to 40. Furthermore, carcass cut‐up percentage was not affected (p > 0.05) by the treatments, except that increased FS level resulted in smaller fat‐pad and larger liver (p < 0.05). Birds deposited omega‐3 (n‐3) fatty acids in breast and thigh muscle the most with higher FS inclusion and pellet‐then‐mash processing. On day 40, the total n‐3 fatty acids made up 22.1 and 24.4% in the muscle lipids of breast and thigh samples from birds fed pellet‐then‐mashed FS at the level of 12% during days 1 to 21 and at the level of 15% during days 22 to 40, respectively. These values were higher (p < 0.05) than those found in birds fed diets of similar FS levels but as whole seed or ground seed. Up to 12% pellet‐processed FS can be incorporated into broiler diets with satisfactory growth, while maximizing n‐3 fatty acid deposition in the tissues. Copyright © 2005 Society of Chemical Industry