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High-resolution Mass Spectrometry (high-resolution + mass_spectrometry)
Selected AbstractsUltra-trace analysis of multiple endocrine-disrupting chemicals in municipal and bleached kraft mill effluents using gas chromatography,high-resolution mass spectrometryENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2008Michael G. Ikonomou Abstract A comprehensive gas chromatographic,high-resolution mass spectrometric (GC-HRMS),based method was developed that permitted the simultaneous determination of 30 estrogenic endocrine-disrupting chemicals (EDCs) and related compounds, including surfactants, biogenic and synthetic steroids, fecal sterols, phytoestrogens, and plasticizers, in wastewater. Features of the method include low sample volume (,40 ml), optimized Florisil® cleanup to minimize matrix interferences and optimized analyte derivatization to improve sensitivity via GC-HRMS. Detection limits were in the low- to mid-ng/L range, and recoveries were greater than 60% for most target analytes. This new method allows for high throughput analysis of many organic wastewater contaminants in a complex matrix with relative standard deviation of less than 15% for most measurable compounds. The applicability of the method was demonstrated by examining wastewater samples from different origins. Compounds such as di(2-ethylhex-yl)phthalate, cholesterol, cholestanol, and other cholesterol derivatives were measured in much higher concentrations in untreated sewage and were reduced substantially in concentration by the treatment process. However, steroidal compounds, particularly estrone (E1), 17,-estradiol (E2), and estriol (E3), as well as plant sterols (except stigmastanol), were greater in the treated municipal wastewater versus the untreated effluent. Plant and fungi sterols, stigmastanol and ergosterol, were found largely associated with bleached kraft mill effluent (BKME) as compared to the municipal effluents. [source] Synthesis, Characterization, and Photophysical Properties of Some Heterodimetallic Bisporphyrins of Ytterbium and Transition Metals , Enhancement and Lifetime Extension of Yb3+ Emission by Transition-Metal Porphyrin SensitizationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2007Feng-Lei Jiang Abstract A series of d-f heterodimetallic bisporphyrin complexes (YbZn, YbPd, and YbPt), in which a YbIII porphyrinate moiety is linked to a transition-metal porphyrinate moiety by a flexible three-carbon chain, were synthesized. They were fully characterized by high-resolution mass spectrometry, 1H and 31P NMR spectroscopy, electronic absorption, andfluorescence methods. Variable-temperature near-infrared photoluminescence studies showed that the transition-metal porphyrinate moiety would enhance the ytterbium(III) emission centered at about 998 nm and extend its emission lifetime. YbPd and YbPt showed large two-photon absorption cross-section values because of the interaction between the porphyrin units, which caused a loss of centrosymmetry. Optical limiting investigation demonstrated that [Yb(TPP)(LOMe)] and YbPt have comparable performance to C60 by virtue of their heavy-metal effect. Our results indicate that these bisporphyrin dimetallic complexes will find valuable applications in the field of nonlinear optics. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Sample Target Substrates with Reduced Spot Size for MALDI-TOF Mass Spectrometry Based on Patterned Self-Assembled MonolayersADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Nicole Herzer Abstract The wetting properties of structured self-assembled monolayers are used to fabricate sample target substrates for MALDI-TOF mass spectrometry. Combining the advantages of a hydrophobic-hydrophilic surface pattern and the possibility of obtaining micrometer patterns allows an increase in the sensitivity of MALDI-TOF mass spectrometry analysis and a reduction in the traceable concentration down to fmol µL,1. This easy, cheap and fast patterning process provides substrates that allow sensitive, high-resolution mass spectrometry of dilute solutions. [source] The Versatility of Helicobacter pylori CagA Effector Protein Functions: The Master Key HypothesisHELICOBACTER, Issue 3 2010Steffen Backert Abstract Several bacterial pathogens inject virulence proteins into host target cells that are substrates of eukaryotic tyrosine kinases. One of the key examples is the Helicobacter pylori CagA effector protein which is translocated by a type-IV secretion system. Injected CagA becomes tyrosine-phosphorylated on EPIYA sequence motifs by Src and Abl family kinases. CagA then binds to and activates/inactivates multiple signaling proteins in a phosphorylation-dependent and phosphorylation-independent manner. A recent proteomic screen systematically identified eukaryotic binding partners of the EPIYA phosphorylation sites of CagA and similar sites in other bacterial effectors by high-resolution mass spectrometry. Individual phosphorylation sites recruited a surprisingly high number of interaction partners suggesting that each phosphorylation site can interfere with many downstream pathways. We now count 20 reported cellular binding partners of CagA, which represents the highest quantitiy among all yet known virulence-associated effector proteins in the microbial world. This complexity generates a highly remarkable and puzzling scenario. In addition, the first crystal structure of CagA provided us with new information on the function of this important virulence determinant. Here we review the recent advances in characterizing the multiple binding signaling activities of CagA. Injected CagA can act as a ,master key' that evolved the ability to highjack multiple host cell signalling cascades, which include the induction of membrane dynamics, actin-cytoskeletal rearrangements and the disruption of cell-to-cell junctions as well as proliferative, pro-inflammatory and anti-apoptotic nuclear responses. The discovery that different pathogens use this common strategy to subvert host cell functions suggests that more examples will emerge soon. [source] Structures of the Reactive Intermediates in Organocatalysis with Diarylprolinol EthersHELVETICA CHIMICA ACTA, Issue 7 2009Abstract Structures of the reactive intermediates (enamines and iminium ions) of organocatalysis with diarylprolinol derivatives have been determined. To this end, diarylprolinol methyl and silyl ethers, 1, and aldehydes, PhCH2CHO, tBuCH2CHO, PhCH=CHCHO, are condensed to the corresponding enamines, A and 3 (Scheme,2), and cinnamoylidene iminium salts, B and 4 (Scheme,3). These are isolated and fully characterized by melting/decomposition points, [,]D, elemental analysis, IR and NMR spectroscopy, and high-resolution mass spectrometry (HR-MS). Salts with BF4, PF6, SbF6, and the weakly coordinating Al[OC(CF3)3]4 anion were prepared. X-Ray crystal structures of an enamine and of six iminium salts have been obtained and are described herein (Figs.,2 and 4,8, and Tables,2 and 7) and in a previous preliminary communication (Helv. Chim. Acta2008, 91, 1999). According to the NMR spectra (in CDCl3, (D6)DMSO, (D6)acetone, or CD3OD; Table,1), the major isomers 4 of the iminium salts have (E)-configuration of the exocyclic NC(1,) bond, but there are up to 11% of the (Z)-isomer present in these solutions (Fig.,1). In all crystal structures, the iminium ions have (E)-configuration, and the conformation around the exocyclic N-CC-O bond is synclinal-exo (cf.C and L), with one of the phenyl groups over the pyrrolidine ring, and the RO group over the , -system. One of the meta -substituents (Me in 4b, CF3 in 4c and 4e) on a 3,5-disubstituted phenyl group is also located in the space above the , -system. DFT Calculations at various levels of theory (Tables,3,6) confirm that the experimentally determined structures (cf. Fig.,10) are by far (up to 8.3,kcal/mol) the most stable ones. Implications of the results with respect to the mechanism of organocatalysis by diarylprolinol derivatives are discussed. [source] Electrophilic S -Trifluoromethylation of Cysteine Side Chains in , - and , -Peptides: Isolation of Trifluoro-methylated Sandostatin® (Octreotide) DerivativesHELVETICA CHIMICA ACTA, Issue 11 2008Stefania Capone Abstract The new electrophilic trifluoromethylating 1-(trifluoromethyl)-benziodoxole reagents A and B (Scheme,1) have been used to selectively attach CF3 groups to the S-atom of cysteine side chains of , - and , -peptides (up to 13-residues-long; products 7,14). Other functional groups in the substrates (amino, amido, carbamate, carboxylate, hydroxy, phenyl) are not attacked by these soft reagents. Depending on the conditions, the indole ring of a Trp residue may also be trifluoromethylated (in the 2-position). The products are purified by chromatography, and identified by 1H-, 13C-, and 19F-NMR spectroscopy, by CD spectroscopy, and by high-resolution mass spectrometry. The CF3 groups, thus introduced, may be replaced by H (Na/NH3), an overall Cys/Ala conversion. The importance of trifluoromethylations in medicinal chemistry and possible applications of the method (spin-labelling, imaging, PET) are discussed. [source] Synthesis, and Helix or Hairpin-Turn Secondary Structures of ,Mixed' ,/, -Peptides Consisting of Residues with Proteinogenic Side Chains and of 2-Amino-2-methylpropanoic Acid (Aib)HELVETICA CHIMICA ACTA, Issue 9 2006Dieter Seebach Abstract Twelve peptides, 1,12, have been synthesized, which consist of alternating sequences of , - and , -amino acid residues carrying either proteinogenic side chains or geminal dimethyl groups (Aib). Two peptides, 13 and 14, containing 2-methyl-3-aminobutanoic acid residues or a ,random mix' of ,-, ,2 -, and ,3 -amino acid moieties were also prepared. The new compounds were fully characterized by CD (Figs.,1 and 2), and 1H- and 13C-NMR spectroscopy, and high-resolution mass spectrometry (HR-MS). In two cases, 3 and 14, we discovered novel types of turn structures with nine- and ten-membered H-bonded rings forming the actual turns. In two other cases, 8 and 11, we found 14/15 -helices, which had been previously disclosed in mixed ,/, -peptides containing unusual , -amino acids with non-proteinogenic side chains. The helices are formed by peptides containing the amino acid moiety Aib in every other position, and their backbones are primarily not held together by H-bonds, but by the intrinsic conformations of the containing amino acid building blocks. The structures offer new possibilities of mimicking peptide,protein and protein,protein interactions (PPI). [source] Synthesis, CD Spectra, and Enzymatic Stability of ,2 -Oligoazapeptides Prepared from (S)-2-Hydrazino Carboxylic Acids Carrying the Side Chains of Val, Ala, and LeuHELVETICA CHIMICA ACTA, Issue 12 2003Gérald Lelais , -Peptides offer the unique possibility to incorporate additional heteroatoms into the peptidic backbone (Figs.,1 and 2). We report here the synthesis and spectroscopic investigations of ,2 -peptide analogs consisting of (S)-3-aza- , -amino acids carrying the side chains of Val, Ala, and Leu. The hydrazino carboxylic acids were prepared by a known method: Boc amidation of the corresponding N -benzyl- L - , -amino acids with an oxaziridine (Scheme,1). Couplings and fragment coupling of the 3-benzylaza- ,2 -amino acids and a corresponding tripeptide (N -Boc/C -OMe strategy) with common peptide-coupling reagents in solution led to ,2 -di, ,2 -tri-, and ,2 -hexaazapeptide derivatives, which could be N -debenzylated (4,9; Schemes,2,4). The new compounds were identified by optical rotation, and IR, 1H- and 13C-NMR, and CD spectroscopy (Figs.,4 and 5) and high-resolution mass spectrometry, and, in one case, by X-ray crystallography (Fig.,3). In spite of extensive measurements under various conditions (temperatures, solvents), it was not possible to determine the secondary structure of the ,2 -azapeptides by NMR spectroscopy (overlapping and broad signals, fast exchange between the two types of NH protons!). The CD spectra of the N -Boc and C -OMe terminally protected hexapeptide analog 9 in MeOH and in H2O (at different pH) might arise from a (P)- 314 -helical structure. The N -Boc- ,2 -tri and N -Boc- ,2 -hexaazapeptide esters, 7 and 9, were shown to be stable for 48,h against the following peptidases: pronase, proteinase,K, chymotrypsin, trypsin, carboxypeptidase,A, and 20S proteasome. [source] Mass defect filter technique and its applications to drug metabolite identification by high-resolution mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2009Haiying Zhang Abstract Identification of drug metabolites by liquid chromatography/mass spectrometry (LC/MS) involves metabolite detection in biological matrixes and structural characterization based on product ion spectra. Traditionally, metabolite detection is accomplished primarily on the basis of predicted molecular masses or fragmentation patterns of metabolites using triple-quadrupole and ion trap mass spectrometers. Recently, a novel mass defect filter (MDF) technique has been developed, which enables high-resolution mass spectrometers to be utilized for detecting both predicted and unexpected drug metabolites based on narrow, well-defined mass defect ranges for these metabolites. This is a new approach that is completely different from, but complementary to, traditional molecular mass- or MS/MS fragmentation-based LC/MS approaches. This article reviews the mass defect patterns of various classes of drug metabolites and the basic principles of the MDF approach. Examples are given on the applications of the MDF technique to the detection of stable and chemically reactive metabolites in vitro and in vivo. Advantages, limitations, and future applications are also discussed on MDF and its combinations with other data mining techniques for the detection and identification of drug metabolites. Copyright © 2009 John Wiley & Sons, Ltd. [source] Matrix effects on accurate mass measurements of low-molecular weight compounds using liquid chromatography-electrospray-quadrupole time-of-flight mass spectrometry,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2006F. Calbiani Abstract Liquid chromatography (LC) with high-resolution mass spectrometry (HRMS) represents a powerful technique for the identification and/or confirmation of small molecules, i.e. drugs, metabolites or contaminants, in different matrices. However, reliability of analyte identification by HRMS is being challenged by the uncertainty that affects the exact mass measurement. This parameter, characterized by accuracy and precision, is influenced by sample matrix and interferent compounds so that questions about how to develop and validate reliable LC-HRMS-based methods are being raised. Experimental approaches for studying the effects of various key factors influencing mass accuracy on low-molecular weight compounds (MW < 150 Da) when using a quadrupole-time-of-flight (QTOF) mass analyzer were described. Biogenic amines in human plasma were considered for the purpose and the effects of peak shape, ion abundance, resolution and data processing on accurate mass measurements of the analytes were evaluated. In addition, the influence of the matrix on the uncertainty associated with their identification and quantitation is discussed. A critical evaluation on the calculation of the limits of detection was carried out, considering the uncertainty associated with exact mass measurement of HRMS-based methods. The minimum concentration level of the analytes that was able to provide a statistical error lower than 5 ppm in terms of precision was 10 times higher than those calculated with S/N = 3, thus suggesting the importance of considering both components of exact mass measurement uncertainty in the evaluation of the limit of detection. Copyright © 2006 John Wiley & Sons, Ltd. [source] Structure investigation of Maltacine C1a, C1b, C2a and C2b,cyclic peptide lactones of the Maltacine complex from Bacillus subtilisJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2005Gunnar Hagelin Abstract A new complex of cyclic peptide lactone antibiotics from Bacillus subtilis, which we named Maltacines, has recently been described. The structure elucidation of four of them is reported in this paper. The amino acid sequences and structures of the peptides were found by MSn of the ring-opened linear peptides, which gave uninterrupted sequences of Bn and Y,n ions. The identities of three unknown residues in the sequences were solved by a combination of derivatisation with phenylisothiocyanate (PITC), high-resolution mass spectrometry and H/D exchange. The nature and position of the cyclic structure was disclosed by a chemo-selective ring opening with Na18OH and was found to be a lactone formed between a hydroxyl of residue number 4 and the C -terminal amino acid number 12. For verification of the structure of the B2+ ion, peptides with different combinations of P/Q and P/K at the N -terminus were synthesised. The structure of the four peptides were found to be: C1a and C2a: cyclo-4,12(P-Q-Y-Adip-V-E-T-Y-Orn-103-Y-I-OH) and C1b/C2b: cyclo-4,12(P-Q-Y-Adip-V-E-T-Y-K-103-Y-I-OH). Adip = aminodihydroxy pentanoic acid. Copyright © 2005 John Wiley & Sons, Ltd. [source] Structure investigation of Maltacine D1a, D1b and D1c,cyclic peptide lactones of the Maltacine complex from Bacillus subtilisJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2005Gunnar Hagelin Abstract A new complex of cyclic peptide lactone antibiotics from Bacillus subtilis, which we named Maltacines has recently been described. The structure elucidation of three of them is reported in this paper. The amino acid sequences and structures of the peptides were found by MSn of the ring-opened linear peptides that gave uninterrupted sequences of Bn and Y,n ions. The identities of four unknown residues in the sequences were solved by a combination of derivatisation with phenylisothiocyanate (PITC), high-resolution mass spectrometry and H/D exchange. The nature and position of the cyclic structure was disclosed by a chemo-selective ring opening with Na18OH and was found to be a lactone formed between a hydroxyl of residue number 4 and the C -terminal amino acid number 12. For verification of the structure of the B2+ ion, peptides with different combinations of P/Q and P/K at the N -terminus were synthesized. The structures of the four peptides is tentatively suggested to be: D1a: cyclo(4,12)-P-Q-Y-Adip-A-E-T-Y-Orn-HGly-Y-I-OH, D1b: cyclo(4,12)-P-Q-Y-Adip-A-E-T-Y-Orn-S-Y-I-OH and D1c: cyclo(4,12)-P-Q-Y-Adip-A-E-T-Y-K-S-Y-I-OH. Adip = aminodihydroxy pentanoic acid and HGly = hydroxyglycine. Copyright © 2005 John Wiley & Sons, Ltd. [source] Differentiation of sulfate and phosphate by H/D exchange mass spectrometry: application to isoflavoneJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2004Akira Kanakubo Abstract Often phosphorylation or sulfation is an important step which occurs in the signal transduction and cascade of metabolic pathways. Some natural products and metabolites contain one or more sulfate or phosphate groups. Isoflavone sulfate has been identified from high-resolution mass spectrometry (HRMS) and enzymatic digestion by sulfatase. We previously reported the new water-soluble isoflavone analogs, daidzein 7- O -phosphate and genistein 7- O -phosphate, which were surprisingly hydrolyzed by sulfatase. In this previous study, we could not determine the phosphate from the results of HRMS and enzymatic digestion, that is, HRMS and enzymatic digestion did not provide clear evidence. In this case, we drew conclusions from NMR analysis. HRMS has been ineffective with a regular fast atom bombardment (FAB) mass spectrometer to distinguish between phosphate and sulfate since the mass difference is only 0.009 mass units. There was, however, no conventional method of microanalysis to distinguish phosphate from sulfate owing to the same nominal mass. It is still very difficult to determine by negative FABMS [OP(O)(OH)2] = 80 and [OS(O)2OH] = 80. In this paper, we report a method to distinguish between these groups by using a popular low-resolution mass instrument; thus, phosphate and sulfate were measured by H/D exchange mass spectrometry at the picomole level to differentiate [OP(O)(OD)2] = 82 and [OS(O)2OD] = 81, respectively. This method is applicable not only to the isoflavone, but also to other phospho and sulfo compounds. Copyright © 2004 John Wiley & Sons, Ltd. [source] Novel benzyl rearrangements in electrospray ionization multistage tandem mass spectra of benzyl 2,,3, - didehydro-2,,3, -dideoxythymidin-5, -yl H-phosphonateJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2004Yi Chen Abstract Several alkyl 2,,3, -didehydro-2,,3, -dideoxythymidin-5, -yl H-phosphonates were synthesized and analyzed by electrospray ionization multistage tandem mass spectrometry (ESI , MSn). Two kinds of novel benzyl rearrangement reactions were observed in ESI , MS2 of [M + H]+, [M + Na]+ and [M + K]+ of benzyl 2,,3, -didehydro-2,,3, -dideoxythymidin-5, -yl H-phosphonate. Results from tandem mass spectrometry, high-resolution mass spectrometry and control experiments showed that the benzyl migration could undergo a four-membered cyclic rearrangement reaction, and benzyl was essential in the process. Copyright © 2004 John Wiley & Sons, Ltd. [source] Mass spectrometric identification of the trypsin cleavage pathway in lysyl-proline containing oligotuftsin peptidesJOURNAL OF PEPTIDE SCIENCE, Issue 4 2007Marilena Manea Abstract Trypsin cleaves specifically peptide bonds at the C -terminal side of lysine and arginine residues, except for -Arg-Pro- and -Lys-Pro- bonds which are normally resistant to proteolysis. Here we report evidence for a -Lys-Pro- tryptic cleavage in modified oligotuftsin derivatives, Ac-[TKPKG]4 -NH2) (1), using high-resolution mass spectrometry and HPLC as primary methods for analysis of proteolytic reactions. The proteolytic susceptibility of -Lys-Pro- bonds was strongly dependent on flanking residues, and the flexibility of the peptide backbone might be a prerequisite for this unusual cleavage. While -Lys-Gly- bonds in 1 were rapidly cleaved, the modification of these Lys residues by the attachment of a ß-amyloid(4,10) epitope to yield -Lys(X)-Gly derivatives prevented cleavage of this bond, and provided trypsin cleavage of -Lys-Pro- bonds, the pathway of this degradation being independent on the type of Lys- N, -side chains (acetyl group, amino acid, peptide). Substitution of the Lys residues by Ala at the P,2 positions decreased the tryptic cleavage, while replacement of the bulky side chain of Thr at the P2 positions strongly increased the cleavage of -Lys-Pro- bonds. Circular dichroism (CD) data of the modified oligotuftsin derivatives are in accord with enhanced flexibility of the peptide backbone, as a prerequisite for increased susceptibility to cleavage of -Lys-Pro- bonds. These results obtained of oligotuftsin derivatives might have implications for the proteolytic degradation of target peptides that require specific conformational preconditions. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd. [source] Identification of Kaempferol as a Monoamine Oxidase Inhibitor and Potential Neuroprotectant in Extracts of Ginkgo Biloba LeavesJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 4 2000B. D. SLOLEY The effects of Ginkgo biloba leaf extract on rat brain or livermonoamine oxidase (MAO)-A and -B activity, biogenic amine concentration in nervous tissue, N -methyl- d -aspartate (NMDA)- and N -(2-chloroethyl)- N -ethyl-2-bromobenzylamine (DSP-4)-induced neurotoxicity and antioxidant activity was investigated to determine the effects of the extract on monoamine catabolism and neuroprotection. Ginkgo biloba leaf extract was shown to produce in-vitro inhibition of rat brain MAO-A and -B. The Ginkgo biloba extract was chromatographed on a reverse-phase HPLC system and two of the components isolated were shown to be MAO inhibitors (MAOIs). These MAOIs were identified by high-resolution mass spectrometry as kaempferol and isorhamnetin. Pure kaempferol and a number of related flavonoids were examined as MAOIs in-vitro. Kaempferol, apigenin and chrysin proved to be potent MAOIs, but produced more pronounced inhibition of MAO-A than MAO-B. IC50 (50% inhibition concentration) values for the ability of these three flavones to inhibit MAO-A were 7 times 10,7, 1 times 10,6 and 2 times 10,6m, respectively. Ginkgo biloba leaf extract and kaempferol were found to have no effect ex-vivo on rat or mouse brain MAO or on concentrations of dopamine, noradrenaline, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid. Kaempferol was shown to protect against NMDA-induced neuronal toxicity in-vitro in rat cortical cultures, but did not prevent DSP-4-induced noradrenergic neurotoxicity in an in-vivo model. Both Ginkgo biloba extract and kaempferol were demonstrated to be antioxidants in a lipid-peroxidation assay. This data indicates that the MAO-inhibiting activity of Ginkgo biloba extract is primarily due to the presence of kaempferol. Ginkgo biloba extract has properties indicative of potential neuroprotective ability. [source] Ring-opening reactions of 5-(aryl)thianthrenium bromides with aryl thiolatesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 3 2002Ding-Quan Qian Abstract A series of 5-(aryl)thianthrenium bromides (6a,e) with aryl (Ar) groups phenyl (a), p -tolyl (b), p -anisyl (c), p -chlorophenyl (d) and p -bromophenyl (e) was prepared by reaction of thianthrene 5-oxide with the appropriate Grignard reagent ArMgBr. Reactions of 6a,e with aryl thiolates (Ar,SNa, Ar,,=,phenyl, p -tolyl and p -chlorophenyl, 7a,c) were carried out in MeCN at room temperature. Products from 6a,c were a small amount of arene [benzene (8a) and toluene (8b)], and substantial amounts of ArSAr, (9), thianthrene (Th) and a trisulfide, namely a 2-(ArS)-2,-(Ar,S)-diphenyl sulfide (10). Products from reactions of 6d,e were smaller amounts of 9 and 10 but substantial amounts of 1,4-di(Ar,S)benzene (11) and a tetrasulfide (12a,c). The reactions that lead to products 9,12 are attributed to ligand coupling (LC) pathways in sulfuranes formed by attack of Ar,S, at the sulfonium S atom of 6. In the formation of 11 and 12 the halogen atom (Cl, Br) is first displaced from 6d,e by Ar,S,, giving a new thianthrenium ion (14) from which sulfurane formation (15) follows. Products 10 and 12 result from opening of the thianthrenium ring of sulfuranes 13 and 15 through LC. Products were assayed with a combination of GC and isolation with TLC, and were identified with a combination of GC (authentic compounds), x-ray crystallography (10a), elemental analyses and high-resolution mass spectrometry. The reactions of 6 are compared with earlier reactions of 5-(alkoxy)-and 5-(alkyl)thianthrenium salts (1 and 2). Copyright © 2002 John Wiley & Sons, Ltd. [source] Structural and spectral assignment by 2D NMR of a new prenylated benzopyrancarboxylic acid and structural reassignment of a related compoundMAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2003Sharon J. Burke Abstract A new prenylated benzopyrancarboxylic acid, 1a (3,4-dihydro-5-hydroxy-2,7-dimethyl-8-(2-methyl-2-butenyl)- 2-(4-methyl-1, 3-pentadienyl)-2H -1-benzopyran-6-carboxylic acid) was isolated from Peperomia amplexicaulis and fully characterized by 1D and 2D NMR and high-resolution mass spectrometry. In the course of this investigation, the structure of a related compound (minus the carboxylic acid group) which was previously assigned as 2b was corrected to structure 1b. Copyright © 2003 John Wiley & Sons, Ltd. [source] Identification of metabolites of adonifoline, a hepatotoxic pyrrolizidine alkaloid, by liquid chromatography/tandem and high-resolution mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2009Aizhen Xiong Hepatotoxic pyrrolizidine alkaloid (HPA)-containing plants have always been a threat to human and livestock health worldwide. Adonifoline, a main HPA in Senecio scandens Buch.-Ham. ex D. Don (Qianli guang), was used officially as an infusion in cases of oral and pharyngeal infections in China. In this study in vivo metabolism of adonifoline was studied for the first time by identifying the metabolites of adonifoline present in bile, urine and feces of rats using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MSn) (ion trap) as well as liquid chromatography/electrospray ionization high-resolution mass spectrometry (LC/ESI-HRMS) (quadrupole-time of flight). In total 19 metabolites were identified and, among them, retronecine- N -oxides were confirmed by matching their fragmentation patterns with their fully characterized synthetic compounds. These metabolites are all involved in both phase I and phase II metabolic processes and the principal in vivo metabolism pathways of adonifoline were proposed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Photocrosslinking of a novel ,,, -unsaturated copolyamide: mass spectrometric study on model compounds with benzophenone as photoinitiatorRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2009Marion N'Negue Mintsa The aim of this work was to understand the reactions involved in the photocrosslinking processes of a ,,, -unsaturated copolyamide foreseen as a new UV-curable powder coating. The crosslinking reaction was photoinitiated with benzophenone. In this paper, the photochemical reaction between benzophenone and several model compounds was investigated. The model compounds contained functional groups which could be present in copolyamide. The products resulting from UV curing were identified using a combination of high-resolution mass spectrometry and MSn experiments. The characterization of the products allowed localization of the hydrogen abstraction by the type II photoinitiator during UV curing and, consequently, the determination of the reactive sites of the unsaturated polyamide chain which were involved in the photochemical reaction. Copyright © 2009 John Wiley & Sons, Ltd. [source] High-resolution extracted ion chromatography, a new tool for metabolomics and lipidomics using a second-generation orbitrap mass spectrometerRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 10 2009Albert Koulman Most analytical methods in metabolomics are based on one of two strategies. The first strategy is aimed at specifically analysing a limited number of known metabolites or compound classes. Alternatively, an unbiased approach can be used for profiling as many features as possible in a given metabolome without prior knowledge of the identity of these features. Using high-resolution mass spectrometry with instruments capable of measuring m/z ratios with sufficiently low mass measurement uncertainties and simultaneous high scan speeds, it is possible to combine these two strategies, allowing unbiased profiling of biological samples and targeted analysis of specific compounds at the same time without compromises. Such high mass accuracy and mass resolving power reduces the number of candidate metabolites occupying the same retention time and m/z ratio space to a minimum. In this study, we demonstrate how targeted analysis of phospholipids as well as unbiased profiling is achievable using a benchtop orbitrap instrument after high-speed reversed-phase chromatography. The ability to apply both strategies in one experiment is an important step forward in comprehensive analysis of the metabolome. Copyright © 2009 John Wiley & Sons, Ltd. [source] Metabolite identification of small interfering RNA duplex by high-resolution accurate mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2008Yan Zou On-line liquid chromatography/electrospray ionization high-resolution mass spectrometry (LC/ESI-HRMS) using an LTQ-Orbitrap mass spectrometer was employed to investigate the metabolite profiles of a model siRNA duplex designated HBV263. The HBV263 duplex was incubated in rat and human serum and liver microsomes in vitro. The siRNA drug and its metabolites were then extracted using a liquid-liquid extraction followed by solid-phase extraction (LLE-SPE), and analyzed by LC/ESI-MS. High-resolution accurate mass data enabled differentiation between two possible metabolite sequences with a monoisotopic molecular mass difference of less than 1,Da. ProMass deconvolution software was used to provide semi-automated data processing. In vitro serum and liver microsome incubation samples afforded different metabolite patterns: the antisense strand of the duplex was degraded preferentially in rat and human serum, while the sense strand of the duplex was less stable in rat and human liver microsomes. Copyright © 2008 John Wiley & Sons, Ltd. [source] Liquid chromatography/mass spectrometry for metabonomics investigation of the biochemical effects induced by aristolochic acid in rats: the use of information-dependent acquisition for biomarker identificationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2008Wan Chan The toxic effects of oral administrations of nephrotoxic and carcinogenic aristolochic acid (AA) to male Sprague-Dawley rats were investigated by using high-performance liquid chromatography coupled with a quadrupole time-of-flight mass spectrometer. Analysis of the urine and plasma samples revealed distinct changes in the biochemical patterns in the AA-dosed rats. After peak finding and alignment, principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) were used for multivariate data analysis. Potential biomarkers were studied by high-resolution mass spectrometry (MS) and tandem mass spectrometry (MS/MS) analyses. The MS/MS spectra of all endogenous metabolites satisfying the pre-defined criteria were acquired in a single information-dependent acquisition (IDA) analysis, demonstrating that IDA was an efficient approach for structural elucidation in metabonomic studies. Citric acid and a glucuronide-containing metabolite were observed as potential biomarkers in rat urine. A significant increase in plasma creatinine concentration was also observed in the AA-dosed rats, which indicated that AA induced an adverse effect on the renal clearance function. Copyright © 2008 John Wiley & Sons, Ltd. [source] High-resolution mass spectrometric mapping of reovirus digestionRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 3 2006Ita Had, isejdi Reovirus is an enteric virus built from eight structural proteins that form a double-layered capsid. During virus entry into cells the reovirus outermost capsid layer (composed of proteins ,3 and µ1C) is proteolytically processed to generate first an infectious subviral particle (ISVP), then the transcriptionally active core particle. Previous studies have demonstrated that protein ,3, the outermost protein in the viral capsid, is removed from virus particles extremely rapidly. Other studies, using the detergent tetradecyl sulfate (14SO4) in combination with the protease chymotrypsin, have shown that µ1C cleavage is not necessary for infectious viral processing. We have recently used mass spectrometry to characterize the cascade of ,3 proteolysis in intact reovirus serotype 1 Lang (T1L) virions (Mendez et al., Virology 2003; 311: 289,304). In the present study, we use high-resolution mass spectrometry to characterize the cascade of outer capsid digestion of both T1L and the other commonly used reovirus strain (serotype 3 Dearing [T3D]), with the protease trypsin, both in the presence and absence of 14SO4. These studies indicate that digestion kinetics and specificities are determined both by virus type and by presence or absence of detergent. Presence of detergent accelerated digestion of both outer capsid proteins. In contrast to chymotrypsin digestion, which segregated ,3 digestion from µ1 digestion, both proteins were rapidly digested by trypsin in the presence of detergent. Copyright © 2006 John Wiley & Sons, Ltd. [source] Mass spectrometric investigation of Maltacines E1a and E1b,two members of the Maltacine family of peptide antibioticsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2005Gunnar Hagelin We have recently described the discovery of the Maltacines,a new family of cyclic peptide antibiotics from Bacillus subtilis. In this paper the mass spectrometric characterisation of two of the members is reported. A chemoselective ring opening with base to give the linear peptides was necessary before mass spectrometric characterisation could be performed. MSn of the singly and doubly charged protonated molecules gave uninterrupted series of Bn and Y,n ions that allowed determination of the amino acid sequence. By using a combination of derivatisation with phenylisothiocyanate (PITC), high-resolution mass spectrometry and H/D exchange, the identities of three unknown residues were determined. The nature and position of the cyclic structure were disclosed by a chemoselective ring opening with Na18OH and it was found to be a lactone formed between a hydroxyl of residue number 4 and the C-terminal amino acid number 12. Peptides with different combinations of P/Q and P/K at the N-terminus were synthesised to verify the sequence of the N-terminal B2 ion. The structure of the two peptides is proposed to be: E1a: cyclo-4,12(P-Q-Y-Adip-V-E-T-Y-Orn-S-Y-I-OH) and E1b: cyclo-4,12(P-Q-Y-Adip-V-E-T-Y-K-S-Y-I-OH). Adip,=,(2-amino-4,5-dihydroxypentanoic acid). Copyright © 2005 John Wiley & Sons, Ltd. [source] Characterization of Ganstigmine metabolites in hepatocytes by low- and high-resolution mass spectrometry coupled with liquid chromatographyRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2003Nicola Pelizzi In order to deepen the understanding of the metabolism of Ganstigmine, a new acetylcholinesterase inhibitor under evaluation for the treatment of Alzheimer's disease, samples obtained by incubating the drug with female rat hepatocytes were investigated by low-resolution liquid chromatography/tandem mass spectrometry (LC/MS/MS). The results confirmed the formation of most of the phase I metabolites already demonstrated, but also three new species. The combination of high-resolution quadrupole time-of-flight (Q-TOF) LC/MS and LC/MS/MS measurements, and the evaluation of the more reasonable metabolic routes, allowed the identification of the new metabolites as Geneseroline-glucuronide and oxidized and rearranged Ganstigmine. Analogous investigations were made using hepatocytes from male rat and dog, and both gender monkeys and humans, to compare the metabolic patterns. The results did not indicate substantial differences in terms of numbers and abundances of detected metabolites among the considered species, and also between male and female hepatocytes within each species. Copyright © 2003 John Wiley & Sons, Ltd. [source] Characterisation of combinatorial libraries of mucin-2 antigen peptides by high-resolution mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2002Emöke Windberg An epitope motif, TX1TX2T, of mucin-2 glycoprotein was identified by means of a mucin-2-specific monoclonal antibody, mAb 994, raised against a synthetic mucin-derived 15-mer peptide conjugate. For determination of the epitope sequence recognised with highest affinity by mAb 994, a combinatorial approach was applied using the portioning-mixing technique excluding Cys. Antibody binding of libraries was most profound when Gln was at the X1 position. Analytical characterisation of the TQTX2T library was conducted by amino acid analysis and matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) and electrospray ionisation Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometric methods. Control libraries were prepared by mixing 19 individual peptides corresponding to the TQTX2T sequence. Thus, mixtures of 6, 10 and 19 pentapeptides were analysed and compared with the combinatorial mixture. MALDI-TOFMS was able to detect only partially the components in the 6- and 10-member mixtures, but failed to characterise a more complex 19-member mixture. In contrast, ESI-FTICRMS resolved all mixtures of higher complexity and provided direct identification at monoisotopic resolution, such as for a peptide library containing ,isobaric' lysine and glutamine (,m,=,0.0364,Da). The results of this study suggest that ESI-FTICRMS is a powerful tool for characterisation of combinatorial peptide libraries of higher complexity. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||||||||