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Ion Trap Mass Spectrometry (ion + trap_mass_spectrometry)
Kinds of Ion Trap Mass Spectrometry Selected AbstractsIn vitro metabolism of , -lapachone (ARQ 501) in mammalian hepatocytes and cultured human cellsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2009Xiu-Sheng Miao ARQ 501 (3,4-dihydro-2,2-dimethyl-2H -naphthol[1,2-b]pyran-5,6-dione, , -lapachone) is an anticancer agent, currently in multiple phase II clinical trials as monotherapy and in combination with other cytotoxic drugs. This study focuses on in vitro metabolism in cryopreserved hepatocytes from mice, rats, dogs and humans using [14C]-labeled ARQ 501. Metabolite profiles were characterized using liquid chromatography/mass spectrometry combined with an accurate radioactivity counter. Ion trap mass spectrometry was employed for further structural elucidation. A total of twelve metabolites were detected in the mammalian hepatocytes studied; all of which but one were generated from phase II conjugation reactions. Ten of the observed metabolites were produced by conjugations occurring at the reduced ortho -quinone carbonyl groups of ARQ 501. The metabolite profiles revealed that glucuronidation was the major biotransformation pathway in mouse and human hepatocytes. Monosulfation was the major pathway in dog, while, in rat, it appears glucuronidation and sulfation pathways contributed equally. Three major metabolites were found in rats: monoglucuronide M1, monosulfate M6, and glucuronide-sulfate M9. Two types of diconjugation metabolites were formed by attachment of the second glycone to an adjacent hydroxyl or to an existing glycone. Of the diconjugation metabolites, glucosylsulfate M10, diglucuronide M5, and glucuronide-glucoside M11 represent rarely observed phase II metabolites in mammals. The only unconjugated metabolite was generated through hydrolysis and was observed in rat, dog and human hepatocytes. ARQ 501 appeared less stable in human hepatocytes than in those of other species. To further elucidate the metabolism of ARQ 501 in extrahepatic sites, its metabolism in human kidney, lung and intestine cells was also studied, and only monoglucuronide M1 was observed in all the cell types examined. Copyright © 2008 John Wiley & Sons, Ltd. [source] Ion trap mass spectrometry in the structural analysis of haemoglobin peptides modified by epichlorohydrin and diepoxybutaneRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2002Nadia Miraglia Ion trap mass spectrometry has been shown to be particularly suitable for the structural analysis of high molecular weight peptides directly fragmented in the mass analyser without needing further sub-digestion reactions. Here we report the advantages of using multi-stage ion trap mass spectrometry in the structural characterisation of haemoglobin alkylated with epichlorohydrin and diepoxybutane. Alkylated globins were digested with trypsin and the peptide mixtures were analysed by MS3. This technique allows the sequential fragmentation of peptides under analysis, giving rise to MS3 product ion spectra with additional information with respect to MS2 mass spectra. The results obtained complete the previously reported structural characterisation of alkylated haemoglobin, demonstrating the potential of ion trap mass spectrometry. Copyright © 2002 John Wiley & Sons, Ltd. [source] Metabolites of an orally active antimicrobial prodrug, 2,5-bis(4-amidinophenyl)furan-bis- O -methylamidoxime, identified by liquid chromatography/tandem mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2004Lian Zhou Abstract DB75 (2,5-bis(4-amidinophenyl)furan) is a promising antimicrobial agent against African trypanosomiasis and Pneumocystis carinii pneumonia. However, it suffers from poor oral activity in rodent models for both infections. In contrast, a novel prodrug of DB75, 2,5-bis(4-amidinophenyl)furan-bis- O -methylamidoxime (DB289), has excellent oral activity. DB289 is currently undergoing clinical investigation as a candidate drug to treat primary stage African trypanosomiasis and Pneumocystis carinii pneumonia. In this study, metabolites of DB289 formed after incubation with freshly isolated rat hepatocytes were characterized using liquid chromatography/ion trap mass spectrometry. Administration of DB289 and octadeuterated DB289 in a 1 : 1 mixture greatly facilitated metabolite identification by providing isotope patterns with twin ions separated by 8 m/z units in the ratio 1 : 1, in the extracted ion chromatograms of molecular ions and in the product ion mass spectra of metabolites. Ten metabolites were identified. Series of O -demethylations and N -dehydroxylations led to the metabolic activation of DB289 to DB75 with the production of four intermediate phase I metabolites. Phase II glucuronidation and sulfation led to the formation of four glucuronide and one sulfate metabolites. Copyright © 2004 John Wiley & Sons, Ltd. [source] First report of non-coloured flavonoids in Echium plantagineum bee pollen: differentiation of isomers by liquid chromatography/ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2010Federico Ferreres Apicultural products have been widely used in diet complements as well as in phytotherapy. Bee pollen from Echium plantagineum was analysed by high-performance liquid chromatography/photodiode-array detection coupled to ion trap mass spectrometry (HPLC-PAD-MSn) with an electrospray ionisation interface. The structures have been determined by the study of the ion mass fragmentation, which characterises the interglycosidic linkage in glycosylated flavonoids and differentiates positional isomers. Twelve non-coloured flavonoids were characterised, being kaempferol-3- O -neohesperidoside the major compound, besides others in trace amounts. These include quercetin, kaempferol and isorhamnetin glycosides, with several of them being isomers. Acetylated derivatives are also described. This is the first time that non-coloured flavonoids are reported from this pollen, with MS fragmentation proving to be most useful in the elucidation of isomeric structures. Copyright © 2010 John Wiley & Sons, Ltd. [source] Fragmentation study of diastereoisomeric 2-methyltetrols, oxidation products of isoprene, as their trimethylsilyl ethers, using gas chromatography/ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2004Wu Wang The diastereoisomeric 2-methyltetrols, 2-methylthreitol and 2-methylerythritol, were recently reported as major secondary aerosol components in natural forest aerosols and proposed as molecular markers for the photooxidation of isoprene. In this study, we examine the complex electron and methane chemical ionization behaviors of their trimethylsilyl ethers. In order to gain insight into their fragmentation behaviors, threitol and erythritol were studied as model compounds, and deuterium labeling of the trimethylsilyl groups and ion trap MS2 experiments were performed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Determination of atrazine, deethylatrazine and simazine in water at parts-per-trillion levels using solid-phase extraction and gas chromatography/ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2003W. T. Ma Methods for trace analysis of atrazine and simazine in water have been developed by using stable-isotope dilution with detection by gas chromatography/mass spectrometry. D5 -Atrazine was used as the internal standard for the determination of atrazine and deethylatrazine, while 13C3 -simazine was used for simazine analysis. Water samples were fortified with known amounts of the internal standards and submitted to solid-phase extraction with a C18 bonded-silica cartridge. A gas chromatograph coupled with an ion-trap mass spectrometer was used to analyze the water sample extracts. Method detection limits were 38 parts-per-trillion (ppt) for atrazine and deethylatrazine and 75 ppt for simazine. The accuracy of the method, represented by relative analytical errors, was less than 15%, and the method precision was less than 5% (relative standard deviation, n,=,9). The method was successfully applied to analyze surface water samples collected from a reservoir and a river at ppt levels. Copyright © 2003 John Wiley & Sons, Ltd. [source] Characteristic fragmentation of bacteriohopanepolyols during atmospheric pressure chemical ionisation liquid chromatography/ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2003Helen M. Talbot Bacteriohopanepolyols (BHPs) fragment via characteristic pathways during atmospheric pressure chemical ionisation liquid chromatography/ion trap mass spectrometry (APCI-LC/MSn). Comparison of the MS2 spectra of bacteriohopane-32,33,34,35-tetrol (BHT) and 2, -methylbacteriohopane-32,33,34,35-tetrol has confirmed the previously proposed ring-C cleavage occurring between C-9 and 11 and C-8 and 14. This fragmentation, diagnostic of all hopanoids, also occurs in BHPs containing an amino group (-NH2) at C-35 although the higher relative stability of the ion limits this fragmentation to a minor process after protonation of the basic nitrogen function. Studies of a number of cell cultures including a prochlorophyte (Prochlorothrix hollandica) and a cyanobacterium (Chlorogloeopsis LA) demonstrate the power of this technique to detect composite BHPs with a complex biological functionality at C-35. We also report the first observation of intact pentafunctionalised bacteriohopanepolyols using this method. Copyright © 2003 John Wiley & Sons, Ltd. [source] Atmospheric pressure chemical ionisation reversed-phase liquid chromatography/ion trap mass spectrometry of intact bacteriohopanepolyolsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2003Helen M. Talbot Atmospheric pressure chemical ionisation liquid chromatography/multi-stage ion trap mass spectrometry (APCI-LC/MSn) has been applied to the study of intact bacteriohopanepolyols. Spectral characterisation of bacteriohopanepolyols of known structure present in bacterial extracts (Zymomonas mobilis and a fermenter containing methanotrophs including Methylococcus capsulatus) has revealed greater structural detail than previous liquid chromatography/mass spectrometry (LC/MS) methods and identified characteristic fragmentations indicative of numerous biohopanoid structures. Analysis of a Recent sedimentary extract from Lake Druzhby (Antarctica) has demonstrated the power of this technique to detect biohopanoids in complex samples including at least partial characterisation of previously unknown composite structures. Copyright © 2003 John Wiley & Sons, Ltd. [source] Analyses of second-generation ,legal highs' in the UK: Initial findingsDRUG TESTING AND ANALYSIS, Issue 8 2010Simon D. Brandt Abstract In the UK, mephedrone and other so-called ,legal high' derivatives have recently been classified as Class B, Schedule I under the Misuse of Drugs Act 1971. Since then, alternative products have been advertised on a number of websites. In order to obtain an immediate snapshot of the situation, 24 products were purchased online from 18 UK-based websites over a period of 6 weeks following the ban in April 2010. Qualitative analyses were carried out by gas chromatography ion trap mass spectrometry using electron- and chemical ionization modes, nuclear magnetic resonance spectroscopy, and comparison with reference standards. Overall, the purchased products consisted of single cathinones or cathinone mixtures including mephedrone, butylone, 4-methyl- N -ethylcathinone, flephedrone (4-fluoromethcathinone) and MDPV (3,4-methylenedioxypyrovalerone), respectively. Benzocaine, caffeine, lidocaine, and procaine were also detected. The emphasis was placed on ,Energy 1' (NRG-1), a product advertised as a legal replacement for mephedrone-type derivatives usually claiming to contain naphyrone (naphthylpyrovalerone, O-2482). It was found that 70% of NRG-1 and NRG-2 products appeared to contain a mixture of cathinones banned in April 2010 and rebranded as ,new' legal highs, rather than legal chemicals such as naphyrone as claimed by the retailers. Only one out of 13 NRG-1 samples appeared to show analytical data consistent with naphyrone. These findings also suggest that both consumers and online sellers (unlike manufacturers and wholesalers) are, most likely unknowingly, confronted with the risk of criminalization and potential harm. Copyright © 2010 John Wiley & Sons, Ltd. [source] Ion chemistry in germane/fluorocompounds gaseous mixtures: a mass spectrometric and theoretical studyJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2008Paola Antoniotti Abstract The ion,molecule reactions occurring in GeH4/NF3, GeH4/SF6, and GeH4/SiF4 gaseous mixtures have been investigated by ion trap mass spectrometry and ab initio calculations. While the NFx+ (x = 1,3) react with GeH4 mainly by the exothermic charge transfer, the open-shell Ge+ and GeH2+ undergo the efficient F-atom abstraction from NF3 and form GeF+ and FGeH2+ as the only ionic products. The mechanisms of these two processes are quite similar and involve the formation of the fluorine-coordinated complexes GeFNF2+ and H2GeFNF2+, their subsequent crossing to the significantly more stable isomers FGeNF2+ and FGeH2NF2+, and the eventual dissociation of these ions into GeF+ (or FGeH2+) and NF2. The closed-shell GeH+ and GeH3+ are instead much less reactive towards NF3, and the only observed process is the less efficient formation of GeF+ from GeH+. The theoretical investigation of this unusual H/F exchange reaction suggests the involvement of vibrationally-hot GeH+. Passing from NF3 to SF6 and SiF4, the average strength of the MF bond increases from 70 to 79 and 142 kcal mol,1, and in fact the only process observed by reacting GeHn+ (n = 0,3) with SF6 and SiF4 is the little efficient F-atom abstraction from SF6 by Ge+. Irrespective of the experimental conditions, we did not observe any ionic product of GeN, GeS, or GeSi connectivity. This is in line with the previously observed exclusive formation of GeF+ from the reaction between Ge+ and CF compounds such as CH3F. Additionally observed processes include in particular the conceivable formation of the elusive thiohypofluorous acid FSH from the reaction between SF+ and GeH4. Copyright © 2008 John Wiley & Sons, Ltd. [source] High-sensitivity analysis of specific peptides in complex samples by selected MS/MS ion monitoring and linear ion trap mass spectrometry: Application to biological studiesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2007Inmaculada Jorge Abstract Mass spectrometry (MS) is a technique of paramount importance in Proteomics, and developments in this field have been possible owing to novel MS instrumentation, experimental strategies, and bioinformatics tools. Today it is possible to identify and determine relative expression levels of thousands of proteins in a biological system by MS analysis of peptides produced by proteolytic digestion. In some situations, however, the precise characterization of a particular peptide species in a very complex peptide mixture is needed. While single-fragment ion-based scanning modes such as selected ion reaction monitoring (SIRM) or consecutive reaction monitoring (CRM) may be highly sensitive, they do not produce MS/MS information and their actual specificity must be determined in advance, a prerequisite that is not usually met in a basic research context. In such cases, the MS detector may be programmed to perform continuous MS/MS spectra on the peptide ion of interest in order to obtain structural information. This selected MS/MS ion monitoring (SMIM) mode has a number of advantages that are fully exploited by MS detectors that, like the linear ion trap, are characterized by high scanning speeds. In this work, we show some applications of this technique in the context of biological studies. These results were obtained by selecting an appropriate combination of scans according to the purpose of each one of these research scenarios. They include highly specific identification of proteins present in low amounts, characterization and relative quantification of post-translational modifications such as phosphorylation and S -nitrosylation and species-specific peptide identification. Copyright © 2007 John Wiley & Sons, Ltd. [source] Characterization of industrial alkylpolyphosphonates by infusion electrospray ionization-ion trap mass spectrometry with identification of the impurities by tandem capillary zone electrophoresisJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2006Silvia Ortega-Gadea Abstract Technical grade diethylene-triaminepentakis(methylenephosphonic acid) (I), dihexamethylene-triaminepentakis(methylenephosphonic acid) (II), ethylene-diaminetetrakis(methylenephosphonic acid) (III), hexamethylene-diaminetetrakis(methylenephosphonic acid) (IV), amino-tris(methylenephosphonic acid) (V), hydroxyethyl-aminobis(methylenephosphonic acid) (VI), 1-hydroxyethylidene-1,1-diphosphonic acid (VII), and 2-phosphonobutane-1,2,4-tricarboxylic acid (VIII) were characterized by ion trap mass spectrometry with electrospray ionization (ESI-ITMS). Using the negative ion mode and acid and alkaline media, peak series corresponding to the nominal compounds and to impurities with a lower number of phosphonate groups were distinguished in I,V. Each series was constituted by [M , nH + (n , 1)Na], peaks and peaks produced from them by losses of water, H3PO3(or water plus HPO2), and combined losses. For each [M , nH + (n , 1)Na], peak, the number of losses coincided with the number of phosphonate groups not bound to sodium ions minus one (the group bearing the charge). Owing to the hydroxyethyl group, the spectrum of VI was dominated by the formation of intermolecular esters, with both losses and gains of water according to [nM , H ± mH2O],. A series of [M , nH + (n , 1)Na], peaks were observed for VII and VIII, showing in the latter case that the carboxylate groups may also form adducts with sodium ions. Losses of water and H3PO3were observed in VII, whereas losses of water, CO2, and HPO3 were seen in VIII. The reaction pathways leading to the production of the observed ions are described. The nominal compounds and the impurities were also separated and identified by capillary electrophoresis with ESI-ITMS detection. Copyright © 2005 John Wiley & Sons, Ltd. [source] Study of peptide,sugar non-covalent complexes by infrared atmospheric pressure matrix-assisted laser desorption/ionizationJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2004Christopher E. Von Seggern Abstract Infrared atmospheric pressure matrix-assisted laser desorption/ionization quadrupole ion trap mass spectrometry was applied to the study of siglec binding to oligosaccharide ligands. Peptides were designed to mimic the binding sites of three members of the siglec family: sialoadhesin, MAG and CD22. These peptides were tested for their ability to complex with their carbohydrate ligands 3, -sialyllactose (3,SL) and 6, -sialyllactose (6,SL). All peptides demonstrated the ability to bind to the carbohydrates, with the peptide representing sialoadhesin maintaining its binding specificity for 3,SL in preference to 6,SL. This technique can be used to study other protein,sugar interactions and can be expanded to create high-throughput screening techniques. Copyright © 2004 John Wiley & Sons, Ltd. [source] Gas-phase ion chemistry in the ternary silane,propyne,phosphine systemJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2004Lorenza Operti Abstract The gas-phase ion chemistry of propyne,phosphine and silane,propyne,phosphine mixtures was studied by ion trap mass spectrometry. For the binary mixture, the effect of different partial pressures of the reagents on the yield of C and P-containing ions was evaluated. Reaction sequences and rate constants were determined and reaction efficiencies were calculated from comparison of experimental and collisional rate constants. In the ternary silane,propyne,phosphine systems, the reaction pathways leading to formation of SimCnPpHq+ ions were determined and the rate constants of the most important steps were measured. For some ion species, selected by double isolation procedures (MS/MS), the low ion abundances prevented determination of the reaction rate constants. Si, C and P-containing ions are mainly produced in reactions of SimPpHq+ ions with propyne, while the reactivity of the SimCnHq+ ions towards PH3 and of the CnPpHq+ ions towards SiH4 is very low. The formation of hydrogenated SiCP ions is interesting for their possible role as precursors of amorphous silicon carbides doped with phosphorus, obtained in a single step, by deposition from properly activated silane,propyne,phosphine mixtures. Copyright © 2004 John Wiley & Sons, Ltd. [source] Gas-phase ion chemistry in the ternary SiH4,C3H6,PH3 systemJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2002Stefania Calderan Abstract Propene,phosphine and the silane,propene,phosphine gaseous mixtures were studied by ion trap mass spectrometry. For the binary mixture the variation of ion abundances under different partial pressures and the mechanisms of ion,molecule reactions are reported. Moreover, the rate constants of the main processes were measured and compared with the collisional rate constants to determine the reaction efficiencies. In the ternary silane,propene,phosphine mixture the mechanisms of formation of ion clusters were elucidated, but the complexity of the system and the low abundances of the ions usually isolated by successive steps prevented the determination of rate constants. The hydrogenated ternary ions are mainly formed by reactions of ions with propene, whereas a minor contribution comes from reactions of ions with phosphine. The ions show very low reactivity with silane. The formation processes of these species are discussed in relation to their possible role as precursors of amorphous silicon carbides doped with phosphorus obtained by deposition from properly activated silane,propene,phosphine mixtures. Copyright © 2001 John Wiley & Sons, Ltd. [source] Negative and positive ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and positive ion nano-electrospray ionization quadrupole ion trap mass spectrometry of peptidoglycan fragments isolated from various Bacillus speciesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2001Gerold Bacher Abstract A general approach for the detailed characterization of sodium borohydride-reduced peptidoglycan fragments (syn. muropeptides), produced by muramidase digestion of the purified sacculus isolated from Bacillus subtilis (vegetative cell form of the wild type and a dacA mutant) and Bacillus megaterium (endospore form), is outlined based on UV matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and nano-electrospray ionization (nESI) quadrupole ion trap (QIT) mass spectrometry (MS). After enzymatic digestion and reduction of the resulting muropeptides, the complex glycopeptide mixture was separated and fractionated by reversed-phase high-performance liquid chromatography. Prior to mass spectrometric analysis, the muropeptide samples were subjected to a desalting step and an aliquot was taken for amino acid analysis. Initial molecular mass determination of these peptidoglycan fragments (ranging from monomeric to tetrameric muropeptides) was performed by positive and negative ion MALDI-MS using the thin-layer technique with the matrix ,-cyano-4-hydroxycinnamic acid. The results demonstrated that for the fast molecular mass determination of large sample numbers in the 0.8,10 pmol range and with a mass accuracy of ±0.07%, negative ion MALDI-MS in the linear TOF mode is the method of choice. After this kind of muropeptide screening often a detailed primary structural analysis is required owing to ambiguous data. Structural data could be obtained from peptidoglycan monomers by post-source decay (PSD) fragment ion analysis, but not from dimers or higher oligomers and not with the necessary sensitivity. Multistage collision-induced dissociation (CID) experiments performed on an nESI-QIT instrument were found to be the superior method for structural characterization of not only monomeric but also of dimeric and trimeric muropeptides. Up to MS4 experiments were sometimes necessary to obtain unambiguous structural information. Three examples are presented: (a) CID MSn (n = 2,4) of a peptidoglycan monomer (disaccharide-tripeptide) isolated from B. subtilis (wild type, vegetative cell form), (b) CID MSn (n = 2,4) of a peptidoglycan dimer (bis-disaccharide-tetrapentapeptide) obtained from a B. subtilis mutant (vegetative cell form) and (c) CID MS2 of a peptidoglycan trimer (a linear hexasaccharide with two peptide side chains) isolated from the spore cortex of B. megaterium. All MSn experiments were performed on singly charged precursor ions and the MS2 spectra were dominated by fragments derived from interglycosidic bond cleavages. MS3 and MS4 spectra exhibited mainly peptide moiety fragment ions. In case of the bis-disaccharide-tetrapentapeptide, the peptide branching point could be determined based on MS3 and MS4 spectra. The results demonstrate the utility of nESI-QIT-MS towards the facile determination of the glycan sequence, the peptide linkage and the peptide sequence and branching of purified muropeptides (monomeric up to trimeric forms). The wealth of structural information generated by nESI-QIT-MSn is unsurpassed by any other individual technique. Copyright © 2001 John Wiley & Sons, Ltd. [source] Analytical characterisation of crude extracts from an african Ancistrocladus species using high-performance liquid chromatography and capillary electrophoresis coupled to ion trap mass spectrometryPHYTOCHEMICAL ANALYSIS, Issue 1 2004Matthias Unger Abstract The analysis by HPLC, CE and CE-MS/MS of root bark extracts of a, so far undescribed, Central-African Ancistrocladus species (family Ancistrocladaceae) is described. Owing to the complexity of the extract, the application of reversed-phase HPLC resulted in a partially incomplete separation of the naphthylisoquinoline alkaloids, whilst CE using a non-aqueous buffer proved to be a very valuable complementary method for a ,rst characterisation of the crude extract. By performing additional CE-MS/MS experiments, in combination with parallel isolation studies and structural elucidation using conventional methods, six alkaloidal substances present in the plant could be identi,ed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Proteome analysis of hepatocellular carcinoma cell strains, MHCC97-H and MHCC97-L, with different metastasis potentialsPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 4 2004Shi-Jian Ding Abstract To better understand the mechanism underlying hepatocellular carcinoma (HCC) metastasis and to search for potential markers for HCC prognosis, differential proteome analysis on two HCC cell strains with high and low metastatic potentials, MHCC97-H and MHCC97-L, was conducted using two-dimensional (2-D) gel electrophoresis followed by matrix-assisted laser desorption/time of flight mass spectrometry and liquid chromatography ion trap mass spectrometry. Image analysis of silver-stained 2-D gels revealed that 56 protein spots showed significant differential expression in MHCC97-H and MHCC97-L cells (Student's t -test, P < 0.05) and 4 protein spots were only detected in MHCC97-H cells. Fourteen protein spots were further identified using in-gel tryptic digestion, peptide mass fingerprinting and tandem mass spectrometry. The expressions of pyruvate kinase M2, ubiquitin carboxy-terminal hydrolase L1, laminin receptor 67 kDa, S100 calcium-binding protein A4, thioredoxin and cytokeratin 19 were elevated in MHCC97-H cells. However, manganese superoxide dismutase, calreticulin precursor, cathepsin D, lactate dehydrogenase B, non-metastatic cell protein 1, cofilin 1 and calumenin precursor were down-regulated in MHCC97-H cells. Intriguingly, most of these identified proteins have been reported to be associated with tumor metastasis. The functional implications of alterations in the levels of these proteins are discussed. [source] Determination of triclosan metabolites by using in-source fragmentation from high-performance liquid chromatography/negative atmospheric pressure chemical ionization ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2010Jian-lin Wu Triclosan is a widely used broad-spectrum antibacterial agent that acts by specifically inhibiting enoyl,acyl carrier protein reductase. An in vitro metabolic study of triclosan was performed by using Sprague-Dawley (SD) rat liver S9 and microsome, while the invivo metabolism was investigated on SD rats. Twelve metabolites were identified by using in-source fragmentation from high-performance liquid chromatography/negative atmospheric pressure chemical ionization ion trap mass spectrometry (HPLC/APCI-ITMS) analysis. Compared to electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS) that gave little fragmentation for triclosan and its metabolites, the in-source fragmentation under APCI provided intensive fragmentations for the structural identifications. The invitro metabolic rate of triclosan was quantitatively determined by using HPLC/ESI-ITMS with the monitoring of the selected triclosan molecular ion. The metabolism results indicated that glucuronidation and sulfonation were the major pathways of phase II metabolism and the hydroxylated products were the major phase I metabolites. Moreover, glucose, mercapturic acid and cysteine conjugates of triclosan were also observed in the urine samples of rats orally administrated with triclosan. Copyright © 2010 John Wiley & Sons, Ltd. [source] First report of non-coloured flavonoids in Echium plantagineum bee pollen: differentiation of isomers by liquid chromatography/ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2010Federico Ferreres Apicultural products have been widely used in diet complements as well as in phytotherapy. Bee pollen from Echium plantagineum was analysed by high-performance liquid chromatography/photodiode-array detection coupled to ion trap mass spectrometry (HPLC-PAD-MSn) with an electrospray ionisation interface. The structures have been determined by the study of the ion mass fragmentation, which characterises the interglycosidic linkage in glycosylated flavonoids and differentiates positional isomers. Twelve non-coloured flavonoids were characterised, being kaempferol-3- O -neohesperidoside the major compound, besides others in trace amounts. These include quercetin, kaempferol and isorhamnetin glycosides, with several of them being isomers. Acetylated derivatives are also described. This is the first time that non-coloured flavonoids are reported from this pollen, with MS fragmentation proving to be most useful in the elucidation of isomeric structures. Copyright © 2010 John Wiley & Sons, Ltd. [source] Electrospray ionization and atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry of antioxidants applied in lubricants,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2009Alexander Kassler The aim of this study was to investigate the utility of ion trap mass spectrometry (ITMS) in combination with the two desorption/ionization methods, electrospray (ESI) and atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI), for the detection of antioxidants which are applied in lubricants. These experiments should form the base for future investigations of antioxidants in tribologically formed thin layers on the surface of frictional systems. Seventeen different antioxidants were selected out of the group of hindered phenolic and aromatic aminic compounds. Practically all antioxidants could be characterized by positive ion ESI- and AP-MALDI-ITMS, forming various types/species of molecular ions (e.g. [M]+., [M+H]+, [M+Na]+ or [M,2H+H]+). A few compounds could be analyzed by negative ion ESI-MS, too, but none by negative ion AP-MALDI-MS. The influence of target materials in AP-MALDI-MS (gold- and titanium nitride (TiN)-covered stainless steel, micro-diamond-covered hard metal, hand-polished and sand-blasted stainless steel targets) with respect to the molecular ion intensity and type of molecular ion of two selected antioxidants was evaluated. The surface properties are of particular interest because in friction tests different materials with different surface characteristics are used. However, the MS results indicate that optimal target surfaces have to be found for individual antioxidants in AP-MALDI-MS but in general smooth surfaces were superior to rough surfaces. Finally the gold-covered stainless steel MALDI target provided the best mass spectra and was selected for all the antioxidants investigated. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of cylindrospermopsin in freshwaters and fish tissue by liquid chromatography coupled to electrospray ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2009Pasquale Gallo Cylindrospermopsin (CYN) is a toxic alkaloid-like compound produced by some strains of cyanobacteria, procariotic organisms occurring in water blooms, observed worldwide in eutrophic lakes and drinking water reservoirs. Methods for determination of CYN in freshwater and fish muscle by liquid chromatography coupled to electrospray ion trap mass spectrometry are herein described. The performances of both methods are reported; ion trap LC/ESI-MS/MS resulted highly selective and reliable in unambiguous identification of CYN, based on monitoring the precursor ion and three product ions. The methods developed showed satisfactory mean recoveries (higher than 63.6%) and relative standard deviations, ranging from 5.8 to 9.8%. The limits of quantification at 0.10,ng/mL in freshwaters and 1.0,ng/g in fish muscle, respectively, allow for determination of CYN also in early contamination stages. Ion trap LC/ESI-MS/MS was successfully applied to the identification and quantification of CYN in water and cyanobacteria extracts from Lake Averno, near Naples, representing the first case of contamination described in southern Italy. Copyright © 2009 John Wiley & Sons, Ltd. [source] Semi-quantitative and structural metabolic phenotyping by direct infusion ion trap mass spectrometry and its application in genetical metabolomicsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2009Albert Koulman The identification of quantitative trait loci (QTL) for plant metabolites requires the quantitation of these metabolites across a large range of progeny. We developed a rapid metabolic profiling method using both untargeted and targeted direct infusion tandem mass spectrometry (DIMSMS) with a linear ion trap mass spectrometer yielding sufficient precision and accuracy for the quantification of a large number of metabolites in a high-throughput environment. The untargeted DIMSMS method uses top-down data-dependent fragmentation yielding MS2 and MS3 spectra. We have developed software tools to assess the structural homogeneity of the MS2 and MS3 spectra hence their utility for phenotyping and genetical metabolomics. In addition we used a targeted DIMS(MS) method for rapid quantitation of specific compounds. This method was compared with targeted LC/MS/MS methods for these compounds. The DIMSMS methods showed sufficient precision and accuracy for QTL discovery. We phenotyped 200 individual Loliumperenne genotypes from a mapping population harvested in two consecutive years. Computational and statistical analyses identified 246 nominal m/z bins with sufficient precision and homogeneity for QTL discovery. Comparison of the data for specific metabolites obtained by DIMSMS with the results from targeted LC/MS/MS analysis showed that quantitation by this metabolic profiling method is reasonably accurate. Of the top 100 MS1 bins, 22 ions gave one or more reproducible QTL across the 2 years. Copyright © 2009 John Wiley & Sons, Ltd. [source] Diastereochemical differentiation of bicyclic diols using metal complexation and collision-induced dissociation mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2009Jaana M. H. Pakarinen Metal complex formation was investigated for di- exo -, di- endo - and trans -2,3- and 2,5-disubstituted trinorbornanediols, and di- exo - and di- endo - 2,3-disubstituted camphanediols using different divalent transition metals (Co2+, Ni2+, Cu2+) and electrospray ionization quadrupole ion trap mass spectrometry. Many metal-coordinated complex ions were formed for cobalt and nickel: [2M+Met]2+, [3M+Met]2+, [M,H+Met]+, [2M,H+Met]+, [M+MetX]+, [2M+MetX]+ and [3M,H+Co]+, where M is the diol, Met is the metal used and X is the counter ion (acetate, chloride, nitrate). Copper showed the weakest formation of metal complexes with di- exo -2,3-disubstituted trinorbornanediol yielding only the minor singly charged ions [M,H+Cu]+, [2M,H+Cu]+ and [2M+CuX]+. No clear differences were noted for cobalt complex formation, especially for cis -2,3-disubstituted isomers. However, 2,5-disubstituted trinorbornanediols showed moderate diastereomeric differentiation because of the unidentate nature of the sterically more hindered exo -isomer. trans -Isomers gave rise to abundant [3M,H+Co]+ ion products, which may be considered a characteristic ion for bicyclo[221]heptane trans -2,3- and trans -2,5-diols. To differentiate cis -2,3-isomers, the collision-induced dissociation (CID) products for [3M+Co]2+, [M+CoOAc]+, [2M,H+Co]+ and [2M+CoOAc]+ cobalt complexes were investigated. The results of the CID of the monomeric and dimeric metal adduct complexes [M+CoOAc]+ and [2M,H+Co]+ were stereochemically controlled and could be used for stereochemical differentiation of the compounds investigated. In addition, the structures and relative energies of some complex ions were studied using hybrid density functional theory calculations. Copyright © 2009 John Wiley & Sons, Ltd. [source] Characterization of dihydrostreptomycin-related substances by liquid chromatography coupled to ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2009Murali Pendela Dihydrostreptomycin sulphate (DHS) is a water-soluble, broad-spectrum aminoglycoside antibiotic. For quantitative analysis, the European Pharmacopoeia (Ph. Eur.) prescribes an ion-pairing liquid chromatography/ultraviolet (LC/UV) method using a C18 stationary phase. Several unknown compounds were detected in commercial samples. Hence, for characterization of these unknown peaks in a commercial DHS sample, the Ph. Eur. method was coupled to mass spectrometry (MS). However, since the Ph. Eur. method uses a non-volatile mobile phase, each peak eluted was collected and desalted before introduction into the mass spectrometer. The desalting procedure was applied to remove the non volatile salt, buffer and ion-pairing reagent in the collected fraction. In total, 20 impurities were studied and 14 of them were newly characterized. Five impurities which are already reported in the literature were also traced in this LC/UV method. Copyright © 2009 John Wiley & Sons, Ltd. [source] Identification of organic hydroperoxides and hydroperoxy acids in secondary organic aerosol formed during the ozonolysis of different monoterpenes and sesquiterpenes by on-line analysis using atmospheric pressure chemical ionization ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2009Marc-Christopher Reinnig On-line ion trap mass spectrometry (ITMS) enables the real-time characterization of reaction products of secondary organic aerosol (SOA). The analysis was conducted by directly introducing the aerosol particles into the ion source. Positive-ion chemical ionization at atmospheric pressure (APCI(+)) ITMS was used for the characterization of constituents of biogenic SOA produced in reaction-chamber experiments. APCI in the positive-ion mode usually enables the detection of [M+H]+ ions of the individual SOA components. In this paper the identification of organic peroxides from biogenic volatile organic compounds (VOCs) by on-line APCI-ITMS is presented. Organic peroxides containing a hydroperoxy group, generated by gas-phase ozonolysis of monoterpenes (, -pinene and , -pinene) and sesquiterpenes (, -cedrene and , -copaene), could be detected via on-line APCI(+)-MS/MS experiments. A characteristic neutral loss of 34,Da (hydrogen peroxide, H2O2) in the on-line MS/MS spectra is a clear indication for the existence of an organic peroxide, containing a hydroperoxy functional group. Copyright © 2009 John Wiley & Sons, Ltd. [source] On-chip solid-phase extraction pre-concentration/focusing substrates coupled to atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry for high sensitivity biomolecule analysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2009Arti Navare Atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) has proven a convenient and rapid method for ion production in the mass spectrometric (MS) analysis of biomolecules. AP-MALDI and electrospray ionization (ESI) sources are easily interchangeable in most mass spectrometers. However, AP-MALDI suffers from less-than-optimal sensitivity due to ion losses during transport from the atmosphere into the vacuum of the mass spectrometer. Here, we study the signal-to-noise ratio (S/N) gains observed when an on-chip dynamic pre-concentration/focusing approach is coupled to AP-MALDI for the MS analysis of neuropeptides and protein digests. It was found that, in comparison with conventional AP-MALDI targets, focusing targets showed (1) a sensitivity enhancement of approximately two orders of magnitude with S/N gains of 200,900 for hydrophobic substrates, and 150,400 for weak cation-exchange (WCX) substrates; (2) improved detection limits as low as 5,fmol/µL for standard peptides; (3) significantly reduced matrix background; and (4) higher inter-day reproducibility. The improved sensitivity allowed successful tandem mass spectrometric (MS/MS) sequencing of dilute solutions of a derivatized tryptic digest of a protein standard, and enabled the first reported AP-MALDI MS detection of neuropeptides from Aedes aegypti mosquito heads. Copyright © 2009 John Wiley & Sons, Ltd. [source] Applications of silver nanoparticles capped with different functional groups as the matrix and affinity probes in surface-assisted laser desorption/ionization time-of-flight and atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry for rapid analysis of sulfur drugs and biothiols in human urineRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2008Kamlesh Shrivas A strategy is presented for the analysis of sulfur drugs and biothiols using silver nanoparticles (AgNPs) capped with different functional groups as the matrix and affinity probes in surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS) and atmospheric pressure-matrix assisted laser desorption/ionization ion trap mass spectrometry (AP-MALDI-ITMS). Biothiols adsorbed on the surface of AgNPs through covalent bonding were subjected to ultraviolet (UV) radiation that enabled desorption and ionization due to the excellent photochemical property of NPs. The proposed method has been successfully applied for the determination of cysteine and homocysteine in human urine samples using an internal standard. The limit of detection (LOD) and limit of quantification (LOQ) for cysteine and homocysteine in urine sample are 7 and 22,nM, respectively, with a relative standard deviation (RSD) of <10%. The advantages of the present method compared with the methods reported in the literature for biothiol analysis are simplicity, rapidity and sensitivity without the need for time-consuming separation and tedious preconcentration processes. Additionally, we also found that the bare AgNPs can be directly used as the matrix in MALDI-TOF MS for the analysis of sulfur drugs without the addition of an extra proton source. Copyright © 2008 John Wiley & Sons, Ltd. [source] Atmospheric pressure desorption/ionization on silicon ion trap mass spectrometry applied to the quantitation of midazolam in rat plasma and determination of midazolam 1,-hydroxylation kinetics in human liver microsomesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2006Rick C. Steenwyk The application of atmospheric pressure desorption/ionization on silicon (AP-DIOS) coupled with ion trap mass spectrometry (ITMS) was investigated for the quantification of midazolam in rat plasma, and determination of midazolam 1,-hydroxylation kinetics in pooled human liver microsomes. Results indicate good sensitivity with absolute detection limits for midazolam in rat plasma of approximately 300 femtograms. A linear dynamic range from approximately 10,5000,ng/mL was obtained in rat plasma with analysis times of 1,min per sample. Kinetic constants for midazolam 1,-hydroxylation in human liver microsomes yielded an apparent Km of 10.0,µM and Vmax of 6.4,nmol/min/mg. Studies investigating the inhibition of 1,-hydroxymidazolam formation by the cytochrome P450 3A4 model inhibitor ketoconazole yielded an IC50 of 0.03,µM. Quantitative precision for replicate analysis of rat plasma and human liver microsomal samples was variable with relative standard deviation (RSD) values ranging from a low of approximately 3% to over 50%, with the highest variability observed in data from human liver microsomal incubations. While preliminary studies investigating the application of AP-DIOS-ITMS suggested feasibility of this technique to typical pharmacokinetic applications, further work is required to understand the underlying causes for the high variability observed in these investigations. Copyright © 2006 John Wiley & Sons, Ltd. [source] The metabolism and excretion of 2-methylaminoethoxycarbonyl-4,4,-dimethoxy-5,6,5,,6,-dimethylenedioxybiphenyl-2,-carboxylic acid (DDB-S) in rats and humanRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2006Hye Hyun Yoo The metabolism and excretion of 2-methylaminoethoxycarbonyl-4,4,-dimethoxy-5,6,5,,6,-dimethylenedioxybiphenyl-2,-carboxylic acid (DDB-S) were investigated in both rats and humans using liquid chromatography/electrospray ion trap mass spectrometry (LC/ESI-MS/MS). In rats, DDB-S was rapidly eliminated from the body after a single 50,mg/kg intravenous injection, with urine being a major excretion route. DDB-S was metabolically stable; approximately 96% of the administered dose was recovered in the form of the parent compound. Nevertheless, 12 metabolites were detected in the urine and feces collected from DDB-S-treated rats. The structural characterizations of the metabolites were elucidated from the MSn spectral analysis. Because DDB-S has a pseudo-symmetrical methylenedioxy biphenyl structure, regioselective deuterium-substituted DDB-S (d5 -DDB-S) was used to assign the metabolic modification. The major metabolic pathways of DDB-S were identified as demethylenation of the methylenedioxy moiety, O-demethylation of the methoxy moiety and glucuronidation. In addition, N-demethylation of the methylaminoethyl group was also detected as a minor reaction. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||