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Electrospray Ionisation Mass Spectrometry (electrospray + ionisation_mass_spectrometry)
Selected AbstractsKinetic and Thermodynamic Studies of the Disproportionation of Hydrogen Peroxide by Dimanganese(ii,ii) and -(ii,iii) Complexes of a Bridging Phenolate LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2005Lionel Dubois Abstract The dimanganese(ii,ii) complexes [Mn2(L)(OAc)2(CH3OH)]-(ClO4) (1a) and [Mn2(L)(OBz)2(H2O)](ClO4) (1b) as well as the dimanganese(ii,iii) complex [Mn2(L)(OAc)2(CH3OH)]-(ClO4)2 (2a), where HL is the asymmetric phenol ligand2-[bis(2-pyridylmethyl)aminomethyl]-6-{[(benzyl)(2-pyridyl-methyl)amino]methyl}-4-methylphenol, react with hydrogen peroxide in acetonitrile solution. The initial reaction rates and their temperature and acid/base dependencies were investigated by monitoring the dioxygen evolution. These studies revealed a first-order dependence on both the catalyst and H2O2 and a strong influence of the carboxylate. Electrospray ionisation mass spectrometry as well as EPR and UV/Vis spectroscopy were used to monitor the reaction catalysed by 2a. The same bis(,-oxo)dimanganese(III,IV) and (,-oxo)dimanganese(ii,iii) active species as found for 1a were detected in the catalytic medium. The EPR spectra recorded during the catalase-like reaction revealed the accumulation of the magnetically uncoupled dimanganese(ii,iii) precursor of the active bis(,-oxo)dimanganese(III,IV) species which dominates the spectra in the case of 1a. This difference can be attributed to the different pH conditions generated by the reaction and reflects differences in the initiation phases for the two catalysts. Overall, the kinetic and thermodynamic studies of H2O2 disproportionation by these dimanganese complexes are fully consistent with the mechanism deduced from our previous extensive spectroscopic studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Rapid and sensitive quantitation of antibiotics in fermentations by electrospray mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2001Janine Morgan Electrospray ionisation mass spectrometry (ESI-MS) has been used for the determination and quantitation of a broad range of 24 antibiotics, from groups including aminoglycosides, ,-lactams, tetracyclines, antifungals and glycopeptides. Spectra have been acquired for all 24 antibiotics derived from pure samples dissolved in acetonitrile/water, along with samples extracted from complex fermentation liquor. Quantitation was carried out by the detection of the protonated molecules, using time-scheduled single-ion monitoring (SIM). ESI-MS was used to detect and quantify to 5-µM levels. A one-step extraction of antibiotics with an organic solvent (methanol) was used for this rapid and simple procedure. Specificity is not matched by other methods and antibiotic analogues (e.g. the five forms of erythromycin) can be determined within minutes. Copyright © 2001 John Wiley & Sons, Ltd. [source] Stability of Anion Binding with Monomers of a Cationic SurfactantCHEMPHYSCHEM, Issue 6 2008Anna Jakubowska Dr. Competitive binding: Electrospray ionisation mass spectrometry is used to probe the binding ability of different anions with a cationic surfactant. Bond strengths are estimated from plots of the intensity of the peak assigned to a given complex ion in the mass spectrum versus the cone voltage applied to induce the abstraction of the counterions from the monomers (see graph). [source] A generic approach to the impurity profiling of drugs using standardised and independent capillary zone electrophoresis methods coupled to electrospray ionisation mass spectrometryELECTROPHORESIS, Issue 9 2005Aurélie Vassort Abstract Three standardised, capillary zone electrophoresis-electrospray ionisation mass spectrometry (CZE-ESI-MS) methods were developed for the analysis of six drug candidates and their respective process-related impurities comprising a total of 22 analytes with a range of functional groups and lipophilicities. The selected backround electrolyte conditions were found to be: 60/40 v/v 10 mM ammonium formate pH 3.5/organic, 60/40 v/v 10 mM ammonium acetate pH 7.0/organic and 10 mM piperidine, pH 10.5, where the organic solvent is 50/50 v/v methanol/acetonitrile. The coaxial sheath flow consisted of either 0.1% v/v formic acid in 50/50 v/v methanol/water, or 10 mM ammonium acetate in 50/50 v/v methanol/water, depending on the mixture being analysed. Factor analysis and informational theory were used to quantify the orthogonality of the methods and predict their complementarities. The three selected CZE-ESI-MS methods allowed the identification of 21 out of 22 of all the drug candidates and their process-related impurities and provided orthogonality with four established high-performance liquid chromatography-mass spectrometry (HPLC-MS) methods. These methodologies therefore form the basis of a generic approach to impurity profiling of pharmaceutical drug candidates and can be applied with little or no analytical method development, thereby offering significant resource and time savings. [source] The First Sandwich Complex with an Octa(thioether) Coordination Sphere: Bis(maleonitrile-tetrathia-12-crown-4)silver(I),EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2006Hans-Jürgen Holdt Abstract The new tetrathiacrown ethers maleonitrile-tetrathia-12-crown-4 (mn12S4) and maleonitrile-tetrathia-13-crown-4 (mn13S4) have been prepared and characterised by X-ray crystallographic analysis. These crown ethers form 2:1, 3:2 and 1:1 complexes with AgY (Y = BF4, PF6). The crystal structures of [Ag(mn12S4)2]BF4 (3a), [Ag(mn13S4)2]BF4 (4a) and [Ag2(mn13S4)3](PF6)2 (6b) have been determined. Compound 3a contains the centrosymmetric sandwich complex cation [Ag(mn12S4)2]+ where each mn12S4 ligand is coordinated to the Ag centre in an endo manner through all four S atoms. The 2:1 complex [Ag(mn12S4)2]+ is the first sandwich complex with a tetrathiacrown ether and the first complex with an octa(thioether) coordination sphere. The crystal structure of compound 4a also reveals a 2:1 complex. This complex, [Ag(mn13S4)2]+, exhibits a half-sandwich structure. One mn13S4 ligand coordinates to Ag+ by all four S donor atoms and the other 13S4 crown by only one S atom. Compound 6b contains a dinuclear Ag complex. The Ag complexes 3a,b,8a,b were also studied by electrospray ionisation mass spectrometry. Collision-induced dissociation (CID) was used to compare the relative stability of 2:1 complexes [AgL2]+ and 1:1 complexes [AgL]+ (L = mn12S4, mn13S4). The 13C NMR chemical shifts of 2:1 and 1:1 Ag complexes and their corresponding free ligands were also estimated and compared. The free energy of the barrier of ring inversion (,G,) for [Ag(mn12S4)2]+ was determined to be 64 kJ,mol,1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] A rapid ultra-performance liquid chromatography,electrospray Ionisation mass spectrometric method for the analysis of saponins in the adventitious roots of Panax notoginsengPHYTOCHEMICAL ANALYSIS, Issue 1 2009Mo Dan Abstract Introduction Saponins are bioactive compounds employed in the prevention and treatment of cardiovascular and cerebrovascular diseases. The adventitious roots of Panax notoginseng may offer an alternative source of saponins. Identification and determination of saponins in the crude extract is challenging owing to their similar structures and the lack of standards. Objective To develop a rapid, sensitive and accurate method based on solid-phase extraction followed by ultra-performance liquid chromatography,electrospray ionisation mass spectrometry (UPLC-ESI-MS) for the identification and quantification of saponins in P. notoginseng. Methodology Following extraction using Waters OasisTM HLB cartridges, the analytes were subjected to a UPLC system with a Waters Acquity BEH C18 chromatographic column and a binary mobile phase system consisting of 0.05% formic acid in water and acetonitrile under gradient elution conditions, with final detection by ESI-MS in the positive ion mode. Results The UPLC-ESI-MS method gave limits of detection and quantification within the range 0.015,0.382 and 0.052,1.124 µg/mL, respectively, for 15 studied saponins. The instrumentation/injection precision (RSD) was 4.5% for a low concentration and 3.2% for an intermediate concentration sample. The intra- and inter-day repeatability was less than 2.65% (RSD). The method described was validated using spiked samples with different amounts of saponin standards. Conclusion This UPLC-ESI-MS assay provides a suitable quality control method for the tentative identification and determination of major biological active constituents in adventitious and native roots of P. notoginseng. Copyright © 2008 John Wiley & Sons, Ltd. [source] Characterisation of fungal lanostane-type triterpene acids by electrospray ionisation mass spectrometryPHYTOCHEMICAL ANALYSIS, Issue 6 2007Gabriela M. Cabrera Abstract Lanostane-triterpene acids obtained from the culture of the fungus Coriolellus malicola were studied by electrospray mass spectrometry in the negative ion mode using quadrupole time-of-flight and quadrupole ion trap analysers. Despite the differences observed in the mass spectra recorded with these instruments, a set of fragment ions was found to be characteristic of the family, depending on the ,7,9(11) or ,8 skeleton and the particular functional group at C-3. Copyright © 2007 John Wiley & Sons, Ltd. [source] Reversed-phase HPLC-ESI/MS analysis of birch leaf proanthocyanidins after their acidic degradation in the presence of nucleophilesPHYTOCHEMICAL ANALYSIS, Issue 5 2007Maarit Karonen Abstract Mountain birch leaves contain large amounts of structurally variable polymeric proanthocyanidins. Their isolation procedure was enhanced by the addition of liquid,liquid extractions prior to column chromatography over Sephadex LH-20. Isolated polymeric proanthocyanidins were depolymerised by acid-catalysis in the presence of benzyl mercaptan or phloroglucinol in order to study their composition. The resulting degradation products, flavan-3-ols and flavan-3-ol adducts, were analysed with reversed-phase high-performance liquid chromatography using UV photodiode array detection for quantification and electrospray ionisation mass spectrometry for identification. The results showed that polymeric proanthocyanidins contained (epi)gallocatechins and (epi)catechins as the extension units and, mainly, (+)-catechin as the terminal unit. The mean degree of polymerisation was found to be 26 based on thiolysis and 31 based on phloroglucinol degradation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Detecting equilibrium cytochrome c folding intermediates by electrospray ionisation mass spectrometry: Two partially folded forms populate the molten-globule statePROTEIN SCIENCE, Issue 3 2002Rita Grandori Abstract Nanoelectrospray ionization mass spectrometry (nano-ESI-MS) is applied to the characterization of ferric cytochromec (cytc) conformational states under different solvent conditions. The methanol-induced molten-globule state in the pH range 2.6,3.0 is found to be populated by two distinct, partially folded conformers IA and IB. The more compact intermediate IB resembles that induced by glycerol in acid-unfolded cytc. The less compact one, IA, also can be induced by destabilization of the native structure by trifluoroethanol. IA and IB can be detected, in the absence of additives, around the midpoint of the acid-induced unfolding transition, providing direct evidence for involvement of equilibrium folding intermediates in cytc conformational transitions at low pH. This study shows that mass spectrometry can contribute to the characterization of molten-globule states of proteins by detection of distinct, although poorly populated, conformations involved in a dynamic equilibrium. [source] Fragmentation pathways of 2,3-dimethyl-2,3-dinitrobutane cations in the gas phaseRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2009Martin R. L. Paine 2,3-Dimethyl-2,3-dinitrobutane (DMNB) is an explosive taggant added to plastic explosives during manufacture making them more susceptible to vapour-phase detection systems. In this study, the formation and detection of gas-phase [M+H]+, [M+Li]+, [M+NH4]+ and [M+Na]+ adducts of DMNB was achieved using electrospray ionisation on a triple quadrupole mass spectrometer. The [M+H]+ ion abundance was found to have a strong dependence on ion source temperature, decreasing markedly at source temperatures above 50°C. In contrast, the [M+Na]+ ion demonstrated increasing ion abundance at source temperatures up to 105°C. The relative susceptibility of DMNB adduct ions toward dissociation was investigated by collision-induced dissociation. Probable structures of product ions and mechanisms for unimolecular dissociation have been inferred based on fragmentation patterns from tandem mass (MS/MS) spectra of source-formed ions of normal and isotopically labelled DMNB, and quantum chemical calculations. Both thermal and collisional activation studies suggest that the [M+Na]+ adduct ions are significantly more stable toward dissociation than their protonated analogues and, as a consequence, the former provide attractive targets for detection by contemporary rapid screening methods such as desorption electrospray ionisation mass spectrometry. Copyright © 2009 Commonwealth of Australia. Published by John Wiley & Sons, Ltd. [source] Investigating the structural properties of amyloid-like fibrils formed in vitro from ,2 -microglobulin using limited proteolysis and electrospray ionisation mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2006Sarah L. Myers The protein ,2 -microglobulin (,2m) aggregates to form classical amyloid fibrils in patients undergoing long-term haemodialysis. Amyloid-like fibrils with a cross- , fold can also be formed from wild-type ,2m under acidic conditions in vitro. The morphology of such fibrils depends critically on the conditions used: incubation of ,2m in low ionic strength buffers at pH 2.5 results in the formation of long (µm), straight fibrils while, at pH 3.6, short (<500,nm) fibrils form. At higher ionic strengths (0.2,0.4,M) at pH 1.5,3.6, the fibrils have a distinct curved and nodular morphology. To determine the conformational properties of ,2m within in vitro fibrils of different morphologies, limited proteolysis of each fibril type using pepsin was performed and the resulting peptide fragments identified by tandem mass spectrometry. For comparison, the proteolytic degradation patterns of monomeric ,2m and seven synthetic peptides spanning the entire sequence of the intact protein were similarly analysed. The results show that fibrils with different morphologies result in distinct digestion patterns. While the curved, worm-like fibrils are relatively weakly protected from proteolysis, the long, straight fibrils formed at pH 2.5 at low ionic strength show only a single cut-site at Val9, demonstrating that substantial refolding of the initially acid-denatured and unprotected state of ,2m occurs during assembly. The data demonstrate that the organisation of the polypeptide chain in fibrils with different morphological features differs considerably, despite the fact that the fibrils possess a common cross- , architecture. Copyright © 2006 John Wiley & Sons, Ltd. [source] Characterisation via electrospray ionisation multistage mass spectrometry of three related series of nitrido technetium complexes containing phosphinothiolate and dithiocarbamate ligandsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2005Michela Tubaro Nine nitrido technetium compounds comprising bis-substituted Tc(N)(PS)2 (1,4) (PS,=,bidentate phosphinothiolate ligands) and Tc(N)(dtc)2 (5, 6) derivatives (dtc,=,bidentate dithiocarbamate), and mixed-ligand Tc(N)(PS)(dtc) (7,9) species, were subjected to electrospray ionisation mass spectrometry and MSn experiments. Bis-substituted phosphinothiolato complexes 1,4 lead to the straightforward formation of dinuclear species reasonably originating from proton bound dimers. These dinuclear species do not show, under collisionally induced fragmentation processes, the formation of monomeric units but cleavages related to the ligand framework, thereby proving the high stability of the [TcH+Tc] bond. Bis-dithiocarbamate compounds 5 and 6 show, instead, abundant [M+H]+, [M+Na]+ and [2M+Na]+ ions, and their collisionally induced fragmentations are highly favoured with cleavages related to the CN and CS bonds. During these processes, the coordination of a water molecule to [MH,L]+ product ions is observed, as proved by the collisionally induced H2O loss detected for this species. Mixed-ligand compounds 7 and 8 show the protonated molecules and Na+ -cationised ions with fragmentation processes related to the dithiocarbamate moiety. This behaviour indicates that coordination of ether- and ester-substituted dithiocarbamates to the [Tc,,N] group is weaker than that of phosphinothiolates. Conversely, diethyldithiocarbamate inserted in mixed complex 9 enhances both CN and TcS bonds, and fragmentation processes suggest that metal-phosphinothiolate and metal-dithiocarbamate show comparable strength. Copyright © 2005 John Wiley & Sons, Ltd. [source] High-performance liquid chromatography with electrospray ionisation mass spectrometry and diode array detection in the identification and quantification of the degradation products of calix[4]arene crown-6 under radiolysisRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2004C. Lamouroux The extraction of 135Cs from high-activity liquid waste, arising from reprocessing of spent nuclear fuel, can be achieved by using calix[4]arene crown-6 compounds. The radiolytic degradation of di(n-octyloxy)calix[4]arene crown-6 (octMC6), in aliphatic or aromatic solvent in contact with 3 M nitric acid, was studied by high-performance liquid chromatography directly coupled to electrospray ionisation mass spectrometry (LC/ESI-MS). More than 50 distinct degradation products were observed, and about 30 of these were identified. These compounds can be assigned to three categories, namely, products of reactions involving radical cleavage or addition, of oxidation reactions, or of aromatic substitution reactions. The major product, corresponding to substitution by an NO2 group, was quantified by external standard calibration using a purified synthetic sample. Despite the observation of all these degradation compounds, octMC6 appears to be remarkably stable under these drastic conditions, combining hydrolysis (HNO3 3,M) and an extreme exposure to radiolysis (106,Gy). Less than 35% degradation of octMC6 was observed in aromatic solvent under these conditions. Copyright © 2004 John Wiley & Sons, Ltd. [source] Electrospray ionisation mass spectrometric study of degradation products of quercetin, quercetin-3-glucoside and quercetin-3-rhamnoglucoside, produced by in vitro fermentation with human faecal floraRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2001Ulla Justesen Eight phenolic compounds, obtained by in vitro fermentation of quercetin, quercetin-3-glucoside and quercetin-3-rhamnoglucoside were analysed by electrospray ionisation mass spectrometry (ESI-MS). Low-energy collision-induced dissociation tandem mass spectrometry (CID-MS/MS) was performed on the [M,,,H], precursor ions to obtain specific fragmentation. Typical fragmentation of the phenolic acids was loss of 44 (CO2) and 18 (H2O),u. Production of m/z 108 by loss of neutral radicals, e.g. HCO2, CH3 or HCO, was also favoured. Structures of the compounds, numbered 1,8, were suggested based on the fragmentation patterns. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||