bluuebunny/crossref_metadata_2025_split huggingface dataset:
Capillary liquid chromatography/atmospheric‐pressure matrix‐assisted laser desorption/ionisation ion trap mass spectrometry: a comparison with liquid chromatography/matrix‐assisted laser desorption/ionisation time‐of‐flight and liquid chromatography/electrospray ionisation quadrupole time‐of‐flight for the identification of tryptic peptides
Authors: Creaser Colin S. , Green Philip S. , Kilby Peter M. , Ratcliffe Lucy 
Published: February 2006

AbstractThe atmospheric‐pressure matrix‐assisted laser desorption/ionisation quadrupole ion trap (AP‐MALDI‐QIT) analysis of tryptic peptides is reported following capillary liquid chromatographic (LC) separation and direct analysis of a protein digest. Peptide fragments were identified by peptide mass fingerprinting from mass spectrometric data and sequence analysis obtained by tandem mass spectrometry of the principal mass spectral peaks using a data‐dependent scanning protocol. These data were compared with those from mass spectrometric analysis using capillary LC/MALDI‐time‐of‐flight (TOF) and capillary LC/electrospray ionisation (ESI)‐quadrupole TOF. For all three configurations the resulting data were searched against the MSDB database, using MASCOT and the sequence coverage compared for each technique. Complementary data were obtained using the three techniques. Copyright © 2006 John Wiley & Sons, Ltd.
Analysis of amitrole by normal‐phase liquid chromatography and tandem mass spectrometry using a sheath liquid electrospray interface
Authors: Girod Marion , Delaurent Corinne , Charles Laurence 
Published: February 2006

AbstractThe coupling of normal‐phase liquid chromatography to tandem mass spectrometry, previously developed in our laboratory, has been applied to the analysis of amitrole. This coupling utilizes an electrospray interface modified to accommodate the introduction of a make‐up solution at the tip of the electrospray probe. A methanolic solution containing 3 mM ammonium acetate delivered at a flow rate of 10 µL · min−1 was found to be the optimal sheath liquid to promote successful ionization of the amitrole. Protonated molecules, arising from in‐source dissociation of ammonium adducts, were subjected to tandem mass spectrometric experiments in a triple‐quadrupole instrument. The main fragmentation reactions were characterized and selected to acquire chromatographic data in the multiple reaction monitoring mode. The limit of detection for amitrole was in the ppm range without any preconcentration step. Enhanced efficiency of ion transmission achievable nowadays in mass spectrometers (this analytical configuration was developed with a 15‐year‐old instrument) is reasonably expected to further improve this detection level. Copyright © 2006 John Wiley & Sons, Ltd.
In vitro metabolism of a new cardioprotective agent, KR‐32570, in human liver microsomes
Authors: Kim Hyojin , Kang Suil , Kim Hyunmi , Yoon Yune‐Jung , Cha Eun‐Young , Lee Hye Suk , Kim Jeong‐Han , Yea Sung Su , Lee Sang‐Seop , Shin Jae‐Gook , Liu Kwang‐Hyeon 
Published: February 2006

AbstractKR‐32570 (5‐(2‐methoxy‐5‐chlorophenyl)furan‐2‐ylcarbonyl)guanidine) is a new reversible Na+/H+ exchanger inhibitor for preventing ischemia‐reperfusion injury. This study was performed to identify the metabolic pathway of KR‐32570 in human liver microsomes. Human liver microsomal incubation of KR‐32570 in the presence of NADPH and UDPGA resulted in the formation of six metabolites, M1–M6. M1 was identified as O‐desmethyl‐KR‐32570, on the basis of liquid chromatography/tandem mass spectrometric (LC/MS/MS) analysis with the synthesized authentic standard. M2 and M3 were suggested to be hydroxy‐KR‐32570 and hydroxy‐O‐desmethyl‐KR‐32570, respectively. M1, M2, and M3 were further metabolized to their glucuronide conjugates, M4, M5, and M6, respectively. In addition, the specific P450 isoforms responsible for KR‐32570 oxidation to two major metabolites, O‐desmethyl‐KR‐32570 and hydroxy‐KR‐32570, were identified using a combination of correlation analysis, chemical inhibition in human liver microsomes and metabolism by expressed recombinant P450 isoforms. The inhibitory potency of KR‐32570 on clinically major P450s was investigated in human liver microsomes. The results show that CYP3A4 contributes to the oxidation of KR‐32570 to hydroxy‐KR‐32570, and CYP1A2 play the predominant role in O‐demethylation of KR‐32570. KR‐32570 was found to inhibit moderately the metabolism of CYP2C8 substrates. Copyright © 2006 John Wiley & Sons, Ltd.
Structural identification of isomers present in technical perfluorooctane sulfonate by tandem mass spectrometry
Authors: Langlois Ingrid , Oehme Michael 
Published: February 2006

AbstractThe structures of isomeric by‐products of technical perfluorooctane sulfonate (PFOS, C8F17SO) were characterized by high‐performance liquid chromatography coupled to mass spectrometry. Ion trap (IT) as well as triple quadrupole (TQ) tandem mass spectrometry (MS/MS) identified ten PFOS isomers with best results being achieved by ion trap MS/MS. In addition to the linear isomer, the main by‐products were isomers with geminal diperfluoromethyl groups and perfluoromethyl‐substituted compounds. Purified fractions of the perfluoromethyl isomers allowed the elucidation of structures and the assignment of the retention times of perfluoroisopropyl‐, 5‐perfluoromethyl‐, 4‐perfluoromethyl‐, 3‐perfluoromethyl‐ and 1‐perfluoromethyl‐PFOS. The concentration of 2‐perfluoromethyl‐PFOS was too low in technical PFOS for a proper identification. Retention times of the geminal substituted diperfluoromethyl isomers could not be properly assigned due to co‐elutions. The number and position of the CF3 groups can be derived from the MS/MS spectra, which allow an unequivocal identification of the isomers. TQ‐MS/MS also allowed us to identify most of the isomers. Copyright © 2006 John Wiley & Sons, Ltd.
Ultra‐performance liquid chromatography coupled to time‐of‐flight mass spectrometry for robust, high‐throughput quantitative analysis of an automated metabolic stability assay, with simultaneous determination of metabolic data
Authors: O'Connor Desmond , Mortishire‐Smith Russell , Morrison Denise , Davies Amy , Dominguez Maria 
Published: February 2006

AbstractThe application of ultra‐performance liquid chromatography coupled to time‐of‐flight mass spectrometry (UPLC/TOFMS) for high‐throughput analysis of a 96‐well plate based metabolic stability assay has been investigated. Full‐scan data were acquired, with run times of 2.5–3.5 min, from which narrow window extracted ion chromatograms were generated, producing quantitative data for the test compound equivalent to that obtained by high‐performance liquid chromatography with tandem mass spectrometric detection on a triple quadrupole instrument (HPLC/MS/MS). Sensitivity and mass accuracy were maintained over the analysis of >300 samples. Additionally, the UPLC/TOFMS datasets obtained gave access to metabolic route information, at no cost in terms of sensitivity for the test compound. Copyright © 2006 John Wiley & Sons, Ltd.
From mass to structure: an aromaticity index for high‐resolution mass data of natural organic matter
Authors: Koch B. P. , Dittmar T. 
Published: February 2006

AbstractRecent progress in Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) has provided extensive molecular mass data for complex natural organic matter (NOM). Structural information can be deduced solely from the molecular masses for ions with extreme molecular element ratios, in particular low H/C ratios, which are abundant in thermally altered NOM (e.g. black carbon). In this communication we propose a general aromaticity index (AI) and two threshold values as unequivocal criteria for the existence of either aromatic (AI > 0.5) or condensed aromatic structures (AI ≥ 0.67) in NOM. AI can be calculated from molecular formulae which are derived from exact molecular masses of naturally occurring compounds containing C, H, O, N, S and P, and is especially useful for substances with aromatic cores and few alkylations. In order to test the validity of our model index, AI is applied to FTICRMS data of a NOM deep‐water sample from the Weddell Sea (Antarctica), a fulvic acid standard, and an artificial dataset of all theoretically possible molecular formulae. For graphical evaluation a ternary plot is suggested for four‐dimensional data representation. The proposed aromaticity index is a step towards structural identification of NOM and the molecular identification of polyaromatic hydrocarbons in the environment. Copyright © 2006 John Wiley & Sons, Ltd.
Solid‐phase microextraction for gas chromatographic/mass spectrometric analysis of dimethoate in human biological samples
Authors: Gallardo E. , Barroso M. , Margalho C. , Cruz A. , Vieira D. N. , López‐Rivadulla M. 
Published: February 2006

AbstractA new, simple and rapid procedure for the determination of dimethoate in urine and blood samples was developed using direct immersion solid‐phase microextraction and gas chromatography/mass spectrometry. This technique required only 0.1 mL of sample, and ethion was used as internal standard. Two types of coated fibre were compared (100 µm polydimethylsiloxane, and 65 µm Carbowax™/divinylbenzene). Other parameters, such as extraction temperature, adsorption and desorption time, salt addition, agitation and pH, were optimized to enhance the sensitivity of the method. Limits of detection (LODs) and quantitation (LOQs) were 50 and 100 ng/mL for urine and 200 and 500 ng/mL for blood, respectively. The method was found to be linear between the LOQ and 40 µg/mL for urine, and between the LOQ and 50 µg/mL for blood, with correlation coefficients ranging from 0.9923–0.9996. Precision (intra‐ and interday) and accuracy were in conformity with the criteria normally accepted in bioanalytical method validation. The mean absolute recoveries of dimethoate were 1.24 and 0.50% for urine and blood, respectively. Because of its simplicity and the fact that small volumes of sample are used, the described method can be successfully used in the diagnosis of poisoning by this pesticide, namely in those situations where the sample volume is limited, as frequently occurs in forensic toxicology. Copyright © 2006 John Wiley & Sons, Ltd.
Screening for metabolically stable aryl‐propionamide‐derived selective androgen receptor modulators for doping control purposes
Authors: Thevis Mario , Kamber Matthias , Schänzer Wilhelm 
Published: February 2006

AbstractAnabolic agents have been among the most frequently detected drugs in amateur and professional sport. A novel class of therapeutics presumably complementing anabolic steroids in the near future includes so‐called selective androgen receptor modulators (SARMs) that have been under clinical investigations for several years. Although not yet commercially available, their potential for misuse in sports is high. Four aryl‐propionamide‐derived SARMs were synthesized in order to establish a fast and robust screening procedure using liquid chromatography/electrospray ionization tandem mass spectrometry. Synthesized compounds were characterized by high‐resolution/high‐accuracy mass analysis employing a linear ion trap‐Orbitrap hybrid mass spectrometer while routine analyses were conducted on a triple‐quadrupole mass spectrometer. Characteristic product ions obtained by collision‐induced dissociation were found at m/z 289 and 261 as well as m/z 269 and 241 representing the bisubstituted aniline residues of selected model compounds. Assay validation was performed regarding lower limit of detection (1 ng/mL), recovery (85–105%), intraday precision (7.6–11.6%) and interday precision (9.9–14.4%), and precursor ion scan experiments on diagnostic product ions enabled the detection of a structurally related compound at 50 ng/mL. Copyright © 2006 John Wiley & Sons, Ltd.
Matrix‐assisted laser desorption/ionization in‐source decay combined with tandem time‐of‐flight mass spectrometry of permethylated oligosaccharides: targeted characterization of specific parts of the glycan structure
Authors: Wuhrer Manfred , Deelder André M. 
Published: February 2006

AbstractMatrix‐assisted laser desorption/ionization tandem time‐of‐flight mass spectrometry (MALDI‐TOF/TOF‐MS) has been introduced in recent years as a valuable tool for the structural characterization of permethylated oligosaccharides. In this report, we describe the combination of MALDI in‐source decay (ISD) with the subsequent TOF/TOF‐MS analyses of specific fragments, allowing the detailed characterization of the selected part of the oligosaccharide molecule. Part of the second‐generation fragment ions were different from those observed in conventional MALDI‐TOF/TOF‐MS experiments. Other fragments, which had already been observed in conventional MALDI‐TOF/TOF‐MS and again showed up in second‐generation fragment analysis, could be assigned to specific parts of the molecule. Our approach disclosed different structural features of the oligosaccharides: due to permethylation, the glycosidic linkage fragments allowed the distinction between terminal, monosubstituted and disubstituted monosaccharides and indicated the oligosaccharide sequence. Moreover, substitution positions were deduced based on characteristic cross‐ring fragmentation by high‐energy collision‐induced fragmentation. In conclusion, combination of MALDI‐ISD with TOF/TOF‐MS allows the detailed characterization of specific moieties of permethylated oligosaccharides and is, therefore, a powerful technique for structural glycomics. Copyright © 2006 John Wiley & Sons, Ltd.
Targeted comparative proteomics by liquid chromatography/matrix‐assisted laser desorption/ionization triple‐quadrupole mass spectrometry
Authors: Melanson Jeremy E. , Chisholm Kenneth A. , Pinto Devanand M. 
Published: February 2006

AbstractHere we report the first application of a matrix‐assisted laser desorption/ionization (MALDI) triple‐quadrupole mass spectrometer for targeted proteomics. Employing an amine‐specific isotopic labelling approach, the technique was validated using five randomly selected bovine serum albumin peptides differentially labelled at known ratios. An indirect benefit of the isotopic labelling technique is a significant enhancement of the a1 ion in tandem mass (MS/MS) spectra of all peptides studied. Therefore, the a1 ion was selected as the fragment ion for multiple reaction monitoring (MRM) in all cases, eliminating tedious method development and optimization. Accurate quantification was achieved with an average relative standard deviation (RSD) of 5% (n = 5) and a detection limit of 14 amol. The technique was then applied to validate an important virulence biomarker of the fungal pathogen Candida albicans, which was not accurately quantified using global proteomics experiment employing two‐dimensional liquid chromatography/electrospray ionization tandem mass spectrometry (2D‐LC/ESI)‐MS/MS. Using LC/MALDI‐MRM analysis of five tryptic peptides, the protein PHR1 was found to be upregulated in the hyphal (pathogenic) form of C. albicans by a factor of 7.7 ± 0.8. Copyright © 2006 John Wiley & Sons, Ltd.
Liquid chromatography/tandem mass spectrometry characterization of oxidized amyloid beta peptides as potential biomarkers of Alzheimer's disease
Authors: Inoue Koichi , Garner Carlos , Ackermann Bradley L. , Oe Tomoyuki , Blair Ian A. 
Published: February 2006

AbstractAlzheimer's disease is characterized by the deposition of senile plaques that consist primarily of amyloid β peptides. There is substantial evidence that amyloid β is oxidized in vivo, which has led to the suggestion that oxidative stress is an important mediator of Alzheimer's disease. Metal‐catalyzed oxidation can mimic in vivo oxidation of amyloid β because the metal ion binds to the amino acid residues at the site of oxidation, which then deliver reactive oxygen species to that site. Based on electrospray mass spectrometry, it has been suggested that metal‐catalyzed oxidation occurs on histidines‐13 and ‐14. Unfortunately, the amyloid β peptides provide complex spectra, so it is difficult to definitively characterize the sites of oxidation. Trypsin digestion of both native and oxidized amyloid β1–16 and amyloid β1–40 resulted in the formation of tryptic peptides corresponding to amyloid β6–16, which could be separated by liquid chromatography (LC). Sites of oxidation were then unequivocally characterized as histidine‐13 and histidine‐14 by LC/tandem mass spectrometric (MS/MS) analysis of the tryptic peptides. The ability to analyze the specific amyloid β6–16 tryptic fragments derived from full‐length amyloid β peptides will make it possible to determine whether oxidation in vivo occurs at specific histidine residues and/or at other amino acid residues such as methionine‐35. Using methodology based on LC/MS/MS it will also be possible to analyze the relative amounts of oxidized peptides and native peptide in cerebrospinal fluid from patients with Alzheimer's disease as biomarkers of oxidative stress. Copyright © 2006 John Wiley & Sons, Ltd.
Matrix‐assisted laser desorption/ionization imaging mass spectrometry for direct measurement of clozapine in rat brain tissue
Authors: Hsieh Yunsheng , Casale Roger , Fukuda Elaine , Chen Jiwen , Knemeyer Ian , Wingate Julia , Morrison Richard , Korfmacher Walter 
Published: February 2006

AbstractMatrix‐assisted laser desorption/ionization hyphenated with quadrupole time‐of‐flight (QTOF) mass spectrometry (MS) has been used to directly determine the distribution of pharmaceuticals in rat brain tissue slices which might unravel their disposition for new drug development. Clozapine, an antipsychotic drug, and norclozapine were used as model compounds to investigate fundamental parameters such as matrix and solvent effects and irradiance dependence on MALDI intensity but also to address the issues with direct tissue imaging MS technique such as (1) uniform coating by the matrix, (2) linearity of MALDI signals, and (3) redistribution of surface analytes. The tissue sections were coated with various matrices on MALDI plates by airspray deposition prior to MS detection. MALDI signals of analytes were detected by monitoring the dissociation of the individual protonated molecules to their predominant MS/MS product ions. The matrices were chosen for tissue applications based on their ability to form a homogeneous coating of dense crystals and to yield greater sensitivity. Images revealing the spatial localization in tissue sections using MALDI‐QTOF following a direct infusion of 3H‐clozapine into rat brain were found to be in good correlation with those using a radioautographic approach. The density of clozapine and its major metabolites from whole brain homogenates was further confirmed using fast high‐performance liquid chromatography/tandem mass spectrometry (HPLC‐MS/MS) procedures. Copyright © 2006 John Wiley & Sons, Ltd.
Analysis of iron(II)/iron(III) phytosiderophore complexes by nano‐electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry
Authors: Weber Günther , von Wirén Nicolaus , Hayen Heiko 
Published: February 2006

AbstractNano‐electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (nano‐ESI‐FTICRMS) was employed for the analysis of the phytosiderophore 2′‐deoxymugineic acid (DMA) and the candidate ligand for the intracellular iron transport in plants nicotianamine (NA). Due to the zwitterionic nature of NA and DMA, complementary mass spectra were obtained in positive and negative ionization modes. The technique was also used for speciation of their complexes with Fe(II) and Fe(III), respectively. The species observed at pH 7.3 are the 1:1 Fe‐ligand complexes and no evidence for the existence of dimeric complexes was observed. NA and DMA differ only by one mass unit. Consequently, in the system NA + DMA + Fe(II)/Fe(III), there are pairs of iron species (i.e. NA‐Fe(II) and DMA‐Fe(III)) with the same nominal mass, which differ only by ∼0.02 mass units. It is shown that high‐resolution MS accompanied by accurate mass data analysis allows the unequivocal identification of all four iron species (NA‐Fe(II), NA‐Fe(III), DMA‐Fe(II), DMA‐Fe(III)) in one solution without separation. We also addressed the possible alteration of the oxidation state of chelated iron under nano‐ESI conditions, but no redox reactions were observed under optimized conditions. Copyright © 2006 John Wiley & Sons, Ltd.
Contextualizing practices across epistemic levels in the chemistry laboratory
Authors: Jiménez‐Aleixandre María‐Pilar , Reigosa Carlos 
Published: February 2006

AbstractThe process of construction of meanings for the concepts of concentration and neutralization is explored in terms of contextualizing practices (Lemke, 1990, Talking Science. Language, Learning and Values, Norwood, NJ: Ablex) creation of meanings through connections established among actions and their context. This notion is expanded to include the connections established among concepts and their context of use, a solving problem task in a laboratory. The purpose is to document the process of meaning construction for these concepts and their transformation from mere terms into decisions and practical actions in a chemistry laboratory. We sought to combine this analysis with an epistemological focus, examining the relative epistemic status of the contextualizing practices. The conversations and actions of four grade 10 students and their teacher (second author) were recorded while solving an open task: to find the concentration of an HCl solution. The results show a progression in the process of contextualization, from an initial inability to use the concepts as part of the resources to complete the titration task, to the transformation of definitions into shared meaningful concepts that allow to take actions, combining theoretical resources with physical ones to solve the problem. A frame for categorizing contextualizing practices across epistemic levels is proposed and applied to the data. © 2006 Wiley Periodicals, Inc. Sci Ed 90:707–733, 2006
Polyoxometalate catalysts: toward the development of green H2O2‐based epoxidation systems
Authors: Mizuno Noritaka , Yamaguchi Kazuya 
Published: February 2006

AbstractThis paper describes the development of green, efficient H2O2‐based epoxidation systems with three kinds of polyoxometalates: (i) a dinuclear peroxotungstate [W2O3(O2)4(H2O)2]2− (I), (ii) a divacant lacunary polyoxotungstate [γ‐SiW10O34(H2O)2]4 (II), (iii) and a divanadium‐substituted polyoxotungstate [γ‐1,2‐H2SiV2W10O40]4− (III). The highly chemo‐, regio‐, and diastereoselective epoxidation of various allylic alcohols with only 1 equiv H2O2 in water can be efficiently catalyzed by potassium salt of I (K‐I). The catalyst K‐I can be recycled with the retention of the catalytic performance. Protonation of a divacant lacunary polyoxotungstate [γ‐SiW10O36]8− gives [γ‐SiW10O34(H2O)2]4− (II) with two aquo ligands. The tetra‐n‐butylammonium salt of II (TBA‐II) catalyzes epoxidation of common olefins including propylene with ≥99% selectivity to epoxide and ≥99% efficiency of H2O2 utilization. The bis(μ‐hydroxo)bridged dioxovanadium site in [γ‐1,2‐H2SiV2W10O40]4− (III) can also efficiently catalyze epoxidation of a variety of olefins with 1 equiv H2O2. Notably, the system with III shows unique stereospecificity, diastereoselectivity, and regioselectivity for the epoxidation of cis/trans olefins, 3‐substituted cyclohexenes, and nonconjugated dienes, respectively, which are quite different from those reported for epoxidation systems up to now. Furthermore, the heterogenization of the mentioned polyoxometalates can be achieved by using ionic liquid‐modified SiO2 as a support without loss of catalytic performance. © 2006 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 6: 12–22; 2006: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20067