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Mass Spectra (mass + spectrum)
Kinds of Mass Spectra Selected AbstractsReview of: Mass Spectra of Designer Drugs 2005JOURNAL OF FORENSIC SCIENCES, Issue 2 2006Terry A. Dal Cason M.S. [source] Novel temperature- and pH-responsive graft copolymers composed of poly(L -glutamic acid) and poly(N -isopropylacrylamide)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2008Chaoliang He Abstract A series of novel temperature- and pH-responsive graft copolymers, poly(L -glutamic acid)- g -poly(N -isopropylacrylamide), were synthesized by coupling amino-semitelechelic poly(N -isopropylacrylamide) with N -hydroxysuccinimide-activated poly(L -glutamic acid). The graft copolymers and their precursors were characterized, by ESI-FTICR Mass Spectrum, intrinsic viscosity measurements and proton nuclear magnetic resonance (1H NMR). The phase-transition and aggregation behaviors of the graft copolymers in aqueous solutions were investigated by the turbidity measurements and dynamic laser scattering. The solution behavior of the copolymers showed dependence on both temperature and pH. The cloud point (CP) of the copolymer solution at pH 5.0,7.4 was slightly higher than that of the solution of the PNIPAM homopolymer because of the hydrophilic nature of the poly(glutamic acid) (PGA) backbone. The CP markedly decreased when the pH was lowered from 5 to 4.2, caused by the decrease in hydrophilicity of the PGA backbone. At a temperature above the lower critical solution temperature of the PNIPAM chain, the copolymers formed amphiphilic core-shell aggregates at pH 4.5,7.4 and the particle size was reduced with decreasing pH. In contrast, larger hydrophobic aggregates were formed at pH 4.2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4140,4150, 2008 [source] A systematic study on the stability of UV ink photoinitiators in food simulants using GCPACKAGING TECHNOLOGY AND SCIENCE, Issue 3 2009Zhi-Wei Wang Abstract Several studies have been published on the stability of plastic monomers and additives in food simulants. However, there are practically no published results about the stability of ink components in food simulants. In this work, the stability of two ultraviolet (UV) ink photoinitiators (PIs) in one aqueous and in two substitute fat food simulants was studied under various time,temperature conditions. Furthermore, the addition of the stabilizing agent hydroquinone monomethyl ester (HQMME) in the same conditions was considered as a comparative experiment. The PIs tested were 1-hydroxycyclohexyl-1-phenyl ketone (Irgacure-184) and benzyldimethyl ketal (Irgacure-651). The various test conditions included exposure of 10 days to temperatures of 20, 40 and 60°C for 10% ethanol and 95% ethanol simulants, and exposure of 2 days to temperatures of 20, 40 and 60°C for isooctane. Following exposure to these conditions, the additive samples were analysed. The extracts of samples exposed to various temperature conditions as well as unexposed spiked controls and blanks were analysed by gas chromatography (GC) on a non-polar (5%-phenyl)-methylpolysiloxane capillary column. The results showed that the protective effect of HQMME was not obvious in all test conditions under dark conditions. The Irgacure-184 was quite stable under all test conditions whether the stabilizing agent was added or not. Irgacure-651 was stable almost under all test conditions, except in 10% ethanol at 60°C. The mass spectrum of decomposed product of Irgacure-651 was detected by GC-MS (Mass Spectrum), and the structure of the decomposed product was obtained by mass spectrographic analysis. The method of detection and disposal is also applicable for UV ink PI migration testing from several different paper or paperboard-plastic coating layer materials into the food simulants used in the study. Copyright © 2008 John Wiley & Sons, Ltd. 2008 [source] Sponge halogenated natural products found at parts-per-million levels in marine mammalsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2002Walter Vetter Abstract Several unknown, abundant brominated compounds (BCs) were recently detected in the blubber of dolphins and other marine mammals from Queensland (northeast Australia). The BCs were interpreted as potential natural products due to the lack of anthropogenic sources for these compounds. This study investigated whether some of the BCs accumulated by diverse marine mammal species are identical with natural BCs previously isolated from sponges (Dysidea sp.) living in the same habitat. Isolates from sponges and mollusks (Asteronotus cespitosus) were compared with the signals detected in the mammals' tissue. Mass spectra and gas chromatography retention times on four different capillary columns of the isolates from sponges and mammals were identical in all respects. This proves that the chemical name of the compound previously labeled BC-2 is 4,6-dibromo-2-(2,,4,-dibromo)phenoxyanisole and that the chemical name of BC-11 is 3,5-dibromo-2-(3,,5,-dibromo,2,-methoxy)phenoxyanisole. Using a quantitative reference solution of BC-2, we established that the concentrations of the brominated metabolites found in the marine mammals are frequently >1 mg/kg. The highest concentration (3.8 mg/kg), found in a sample of pygmy sperm whale (Kogia breviceps), indicates that BC-2 is a bioaccumulative, natural organohalogen compound. This is supported by the concentrations of the BCs in our samples being equal to the highest concentrations of anthropogenic BCs in any environmental sample. The quantitative determination of BC-2 in blubber of marine mammals from Africa and the Antarctic suggests that BC-2 is widespread. These results are direct proof that marine biota can produce persistent organic chemicals that accumulate to substantial concentrations in higher trophic organisms. [source] Photoionization studies on various quinones by an infrared laser desorption/tunable VUV photoionization TOF mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2008Yang Pan Abstract Photoionization and dissociative photoionization characters of six quinones, including 1,2-naphthoquinone (1,2-NQ), 1,4-naphthoquinone (1,4-NQ), 9,10-phenanthroquinone (PQ), 9,10-anthraquinone (AQ), benz[a]- anthracene-7,12-dione (BAD) and 1,2-acenaphthylenedione (AND) have been studied with an infrared laser desorption/tunable synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (IR LD/VUV PIMS) technique. Mass spectra of these compounds are obtained at different VUV photon energies. Consecutive losses of two carbon monoxide (CO) groups are found to be the main fragmentation pathways for all the quinones. Detailed dissociation processes are discussed with the help of ab initio B3LYP calculations. Ionization energies (IEs) of these quinones and appearance energies (AEs) of major fragments are obtained by measuring the photoionization efficiency (PIE) spectra. The experimental results are in good agreement with the theoretical data. Copyright © 2008 John Wiley & Sons, Ltd. [source] A validated liquid chromatographic/tandem mass spectrometric method for the determination of phencyclidine in microliter samples of rat serumJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2005Howard P. Hendrickson Abstract A liquid chromatographic/tandem mass spectrometric method is described for the determination of phencyclidine (PCP) in small volumes of rat serum (e.g. 50 µl). Samples were extracted using a mixed-mode strong cation-exchange column and then separated isocratically using a narrow-bore (2.1 mm i.d.) 3 µm Hypersil phenyl column and a mobile phase consisting of an ammonium formate buffer (pH 2.7) with 60% (v/v) methanol. Detection was accomplished using positive ion electrospray ionization in the multiple reaction monitoring mode. Mass spectra were obtained and peaks were observed at an m/z (% abundance) of 244 (100), 159 (25), and 86 (89). Tandem mass spectra were also obtained from the m/z 244 precursor ion with peaks observed at m/z 159 (100), 86 (96), and 91 (11). Optimum serum PCP sensitivity and precision were obtained at a transition of m/z 244 , 159. Matrix-associated ion suppression did not significantly affect the accuracy (100,112%) or precision (CV ,8%) of the assay. The lower limit of quantitation was 1 ng ml,1 in 50 µl of serum. The method was used to study the serum pharmacokinetics of PCP in rats after an intravenous bolus dose of PCP. Copyright © 2004 John Wiley & Sons, Ltd. [source] Conservation of the function counts: homologous neurons express sequence-related neuropeptides that originate from different genesJOURNAL OF NEUROCHEMISTRY, Issue 3 2009Susanne Neupert Abstract By means of single-cell matrix assisted laser desorption/ionization time-of-flight mass spectrometry, we analysed neuropeptide expression in all FXPRLamide/pheromone biosynthesis activating neuropeptide synthesizing neurons of the adult tobacco hawk moth, Manduca sexta. Mass spectra clearly suggest a completely identical processing of the pheromone biosynthesis activating neuropeptide-precursor in the mandibular, maxillary and labial neuromeres of the subesophageal ganglion. Only in the pban -neurons of the labial neuromere, products of two neuropeptide genes, namely the pban -gene and the capa -gene, were detected. Both of these genes expressed, amongst others, sequence-related neuropeptides (extended WFGPRLamides). We speculate that the expression of the two neuropeptide genes is a plesiomorph character typical of moths. A detailed examination of the neuroanatomy and the peptidome of the (two) pban -neurons in the labial neuromere of moths with homologous neurons of different insects indicates a strong conservation of the function of this neuroendocrine system. In other insects, however, the labial neurons either express products of the fxprl -gene or products of the capa -gene. The processing of the respective genes is reduced to extended WFGPRLamides in each case and yields a unique peptidome in the labial cells. Thus, sequence-related messenger molecules are always produced in these cells and it seems that the respective neurons recruited different neuropeptide genes for this motif. [source] Proteomic analysis of rabbit tear fluid: Defensin levels after an experimental corneal wound are correlated to wound closurePROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 17 2007Lei Zhou Abstract The cornea is the major refracting optical element of the eye and therefore critical for forming a retinal image. The exposed surface of the eye is protected from pathogens by the innate immune system whose components include defensins, naturally occurring peptides with antimicrobial properties, and the physical barrier formed by the outer epithelial layer of the cornea. The proteomic approach has revealed that tear levels of defensins are correlated with the course of healing of an experimental corneal wound. Tears were collected from New Zealand White rabbits prior to (day 0) and daily for 5 days (days 1,5) following a standard unilateral 6,mm diameter corneal epithelial abrasion. Tear protein profiles obtained from wounded and contra-lateral control eyes were compared using SELDI ProteinChip technology. Peptides and proteins of interest were purified by RP-HPLC and characterized by nanoESI-MS/MS. Mass spectra of tears on post-wound day 1, revealed 13,peaks whose level decreased and five that increased. During wound healing the tear protein profile correlated with wound closure. An important finding was that the levels of rabbit defensins (NP-1 and NP-2), which were elevated after wounding returned to normal levels by the time the corneal abrasion healed. Relative quantification of NP-2 in tear fluid prior to (day 0) and after corneal wounding (days 1, 3) was determined using iTRAQ technology. A corneal wound eliminates the barrier function of innate immunity and puts the cornea at risk from microbial attack until the epithelial cells restore the surface barrier. The increased availability of defensins in the tears during healing suggests that these peptides could protect the cornea from microbial attack during a period of increased vulnerability. [source] Characterization of the improvised explosive urea nitrate using electrospray ionization and atmospheric pressure chemical ionizationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2005Tsippy Tamiri Mass spectra of urea nitrate were measured in electrospray ionization and in atmospheric pressure chemical ionization in the negative mode. In both ionization methods two characteristic adduct ions containing the intact molecule [urea nitrate+NO3], and [urea nitrate+HNO3+NO3], are shown. The structure of the two adduct ions was deduced using measurements of isotopically labeled urea nitrate. Collision-induced dissociation measurements of the adduct ions show typical losses enabling the identification of urea nitrate in trace amounts. Using these methods urea nitrate was identified in real cases. Copyright © 2005 John Wiley & Sons, Ltd. [source] Mass spectra of nitro- ,,, -dihalostyrenesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2004Shaw-Tao Lin The electron ionization (EI) fragmentation of nitro- ,,, -dihalostyrenes depends strongly on the specific halogens present as well as on the position of the nitro group. ,,, -Difluorostyrenes yielded mainly fluoroacetylene ions as the base peaks and o -nitro- ,,, -dihalostyrene possibly furnished the ion with a structure similar to that of benzo[a]isoxazole (11). The structural identity of the ion was verified by comparing the collision-induced dissociation (CID) spectra of m/z 119 ions from p - and o -nitro- ,,, -difluorostyrene, o -nitro- ,,, -dibromostyrene and compound 11. Copyright © 2004 John Wiley & Sons, Ltd. [source] Micro-high-performance liquid chromatography/Fourier transform mass spectrometry with electron-capture dissociation for the analysis of protein enzymatic digestsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 10 2002Walter Davidson Electron-capture dissociation (ECD) Fourier transform mass spectrometry (FTMS) employed to generate comprehensive sequence information for the chromatographic analysis of enzymatic protein digests is described. A pepsin digest of cytochrome c was separated by reversed-phase micro-high-performance liquid chromatography (µHPLC) and ionized ,on-line' by electrospray ionization (ESI). The ions thus formed were transferred to and trapped in the FTMS analyzer cell. Typically, no precursor ion isolation was performed. The trapped ions were subjected to a pulse of electrons to induce fragmentation. Mass spectra were acquired continuously to produce a three-dimensional LC/MS data set. The spectra were dominated by c and, to a lesser degree, z ions, which provided near complete sequence coverage. External calibration provided good mass accuracy and resolution, typical of FTMS. Thus,µHPLC/ECD,,,FTMS is shown to be a highly informative method for the analysis of enzymatic protein digests. Copyright © 2002 John Wiley & Sons, Ltd. [source] Identification of key metabolites of tectorigenin in rat urine by HPLC-MSnBIOMEDICAL CHROMATOGRAPHY, Issue 2 2009Wei-Dong Zhang Abstract This is a report about the identification of key metabolites of tectorigenin in rat urine using high-performance liquid chromatography,electrospray ionization ion trap tandem mass spectrometric method (HPLC-ESI-MSn). Six healthy rats were administered a single dose (80 mg/kg) of tectorigenin by oral gavage. Urine was sampled for 0,24 h and centrifuged at 12,000 rpm for 10 min to obtain the supernatants, then the supernatants were purified by solid-phase extraction with a C18 cartridge. The chromatographic separation was carried out on a reversed-phase C18 column with a gradient elution program whereas acetonitrile,0.1% formic acid water was used as mobile phase. Mass spectra were acquired in negative ionization mode and a data-dependant scan was used for the identification of the key metabolites of tectorigenin in the urine samples. As a result, four phase II metabolites and the parent drug tectorigenin were found and identified in rat urine for the first time. Copyright © 2008 John Wiley & Sons, Ltd. [source] P71 Metabolism of delta-3-Carene by human cytochrom 450 enzymesCONTACT DERMATITIS, Issue 3 2004Mike Duisken Occupational exposure to monoterpenes occurs in saw mills, particle-board plants, carpentry shops and other types of wood-treating industries. The bicyclic monoterpene delta-3-Carene, one of the components of turpentine, may irritate the skin and muceous membranes and prolonged exposure may result in allergic contact dermatitis or chronic lung function impairment. The effects of low concentrations of delta-3-Carene on alveolar macrophages in vitro were examined and a dose-dependent relationship between the cell viability and the delta-3-Carene concentration was found. Little is known about the metabolism of delta-3-Carene in mammalians. In order to determine the toxic potential of this monoterpene we studied the human metabolism of delta-3-Carene in vitro. Therefore we used pooled human liver S9 and human liver microsomal cytochrome P450 enzymes. By using GC-MS analysis we found one main metabolite produced at high rates. The structure was identified by its mass spectra. The mass fragmentation indicated hydroxylation in allyl position. After synthesis of the assumed product in a four step reaction, it was characterized as delta-3-Carene-10-ol. There was a clear correlation between the concentration of the metabolite production, incubation time and enzyme concentration, respectively. Kinetic analysis showed that Km and Vmax values for the oxidation of delta-3-Carene by human liver microsomes were 0.39 ,M and 0.2 nmol/min/nmol P450. It is the first time that delta-3-Carene-10-ol is described as human metabolite of delta-3-Carene. [source] Differentiation of structural isomers in a target drug database by LC/Q-TOFMS using fragmentation predictionDRUG TESTING AND ANALYSIS, Issue 6 2010Elli Tyrkkö Abstract Isomers cannot be differentiated from each other solely based on accurate mass measurement of the compound. A liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOFMS) method was used to systematically fragment a large group of different isomers. Two software programs were used to characterize in silico mass fragmentation of compounds in order to identify characteristic fragments. The software programs employed were ACD/MS Fragmenter (ACD Labs Toronto, Canada), which uses general fragmentation rules to generate fragments based on the structure of a compound, and SmartFormula3D (Bruker Daltonics), which assigns fragments from a mass spectra and calculates the molecular formulae for the ions using accurate mass data. From an in-house toxicology database of 874 drug substances, 48 isomer groups comprising 111 compounds, for which a reference standard was available, were found. The product ion spectra were processed with the two software programs and 1,3 fragments were identified for each compound. In 82% of the cases, the fragment could be identified with both software programs. Only 10 isomer pairs could not be differentiated from each other based on their fragments. These compounds were either diastereomers or position isomers undergoing identical fragmentation. Accurate mass data could be utilized with both software programs for structural elucidation of the fragments. Mean mass accuracy and isotopic pattern match values (SigmaFit; Bruker Daltonics Bremen, Germany) were 0.9 mDa and 24.6 mSigma, respectively. The study introduces a practical approach for preliminary compound identification in a large target database by LC/Q-TOFMS without necessarily possessing reference standards. Copyright © 2010 John Wiley & Sons, Ltd. [source] CE coupled to MALDI with novel covalently coated capillariesELECTROPHORESIS, Issue 4 2010Stefan Bachmann Abstract CE offers the advantage of flexibility and method development options. It excels in the area of separation of ions, chiral, polar and biological compounds (especially proteins and peptides). Masking the active sites on the inner surface of a bare fused silica capillary wall is often necessary for CE separations of basic compounds, proteins and peptides. The use of capillary surface coating is one of the approaches to prevent the adsorption phenomena and improve the repeatability of migration times and peak areas of these analytes. In this study, new capillary coatings consisting of (i) derivatized polystyrene nanoparticles and (ii) derivatized fullerenes were investigated for the analysis of peptides and protein digest by CE. The coated capillaries showed excellent run-to-run and batch-to-batch reproducibility (RSD of migration time ,0.5% for run-to-run and ,9.5% for batch-to-batch experiments). Furthermore, the capillaries offer high stability from pH 2.0 to 10.0. The actual potential of the coated capillaries was tested by combining CE with MALDI-MS for analysing complex samples, such as peptides, whereas the overall performance of the CE-MALDI-MS system was investigated by analysing a five-protein digest mixture. Subsequently, the peak list (peptide mass fingerprint) generated from the mass spectra of each fraction was entered into the Swiss-Prot database in order to search for matching tryptic fragments using the MASCOT software. The sequence coverage of analysed proteins was between 36 and 68%. The established technology benefits from the synergism of high separation efficiency and the structure selective identification via MS. [source] A multilayer poly(dimethylsiloxane) electrospray ionization emitter for sample injection and online mass spectrometric detectionELECTROPHORESIS, Issue 24 2005Jamie M. Iannacone Abstract An ESI emitter made of poly(dimethylsiloxane) interfaces on-chip sample preparation with MS detection. The unique multilayer design allows both the analyte and the spray solutions to reside on the device simultaneously in discrete microfluidic environments that are spatially separated by a polycarbonate track-etched, nanocapillary array membrane (NCAM). In direct spray mode, voltage is applied to the microchannel containing a spray solution delivered via a syringe pump. For injection, the spray potential is lowered and a voltage is applied that forward biases the membrane and permits the analyte to enter the spray channel. Once the injection is complete, the bias potential is switched off, and the spray voltage is increased to generate the ESI of the injected analyte plug. Consecutive injections of a 10,,M bovine insulin solution are reproducible and produce sample plugs with limited band broadening and high quality mass spectra. Peptide signals are observed following transport through the NCAM, even when the peptide is dissolved in solutions containing up to 20% seawater. The multilayer emitter shows great potential for performing multidimensional chemical manipulations on-chip, followed by direct ESI with negligible dead volume for online MS analysis. [source] Photophysical and Photochemical Properties of Fluorinated and Nonfluorinated n -Propanol-Substituted Zinc PhthalocyaninesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2010lke Gürol Abstract The synthesis of symmetrical fluorinated and nonfluorinated zinc(II) phthalocyanine derivatives obtained from 4,5-dichlorophthalonitrile, 4-nitrophthalonitrile and 3-nitrophthalonitrile substituted with 2,2,3,3-tetrafluoro-1-propanol and n -propanol are described. The comparison of the photophysicochemical properties of fluorinated and nonfluorinated substituted zinc(II) phthalocyanines is reported for the first time. The new compounds have been characterized by elemental analysis, IR, 1H NMR and 19F NMR spectroscopy, electronic spectroscopy and mass spectra. The photophysical and photochemical properties of the compounds were studied in dimethyl sulfoxide (DMSO). The complexes were quenched with benzoquinone (BQ), and their fluorescence-quenching properties were investigated in the same solvent. The effects of the number of the substitution and the position on the photophysical and photochemical parameters of the zinc(II) phthalocyanines 1a,7a are also reported. Photophysical and photochemical properties of phthalocyanine complexes are very useful for photodynamic therapy (PDT) of cancer applications. In particular, high singlet-oxygen quantum yields are very important for Type II mechanisms. These complexes have good singlet-oxygen quantum yields and show potential as Type-II photosensitizers. [source] A Combined Gas-Phase Electron Diffraction/Mass Spectrometric Study of the Sublimation Processes of TeBr4 and TeI4: The Molecular Structure of Tellurium Dibromide and Tellurium DiiodideEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2008Sergey A. Shlykov Abstract The sublimation processes of TeBr4 at 471(5) K and TeI4 at 373(5) K were studied with a combined gas-phase electron diffraction and mass spectrometric technique (GED/MS). The mass spectra and the analysis of the GED intensities showed that a contribution of 40(3) mol-% TeBr2, 59(3) mol-% Br2, and 1 mol-% TeBr4 was formed in the vapor over TeBr4(s). Solid tellurium tetraiodide decomposes to form I2(g) and Te(s). A very small contribution of 3.3,±,2.1 mol-% of gaseous TeI2 was also determined by both GED and MS. The "metallic" Te accumulated in the solid phase vaporizes at above ca. 670 K as the predominately Te2 molcular species. Refinement of the GED intensities resulted in rg(Te,Br) = 2.480(5) Å and ,gBr,Te,Br = 99.0(6)° for TeBr2 and rg(Te,I) = 2.693(9) Å and ,g(I,Te,I) = 103.1(22)° for TeI2. The small contribution of TeBr4 observed in the mass spectra of the vapor over TeBr4 could not be observed in the GED data. Geometric parameters and vibrational frequencies for the tellurium dihalides TeX2 with X = F, Cl, Br, and I were calculated with B3LYP, MP2, CCSD, and CCSD(T) methods by using aug-cc-pVTZ basis sets and various core potentials for the tellurium atom. Bonding properties in tellurium dihalides are discussed on the basis of natural bond orbital analyses. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Contribution to the Reactivity of N,N, -Diaryl-1,4-diazabutadienes Aryl,N=CH,CH=N,Aryl (Aryl = 2,6-Dimethylphenyl; 2,4,6-Trimethylphenyl) Towards Boron TrichlorideEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2006Lothar Weber Abstract The reaction of Aryl,N=CH,CH=N,Aryl (3a: Aryl = 2,6-Me2C6H3; 3b: Aryl = 2,4,6-Me3C6H2) with 2 equiv. BCl3 in a toluene/hexane mixture at ,50 °C led to an inseparable mixture of borolium salts [Aryl,Na=CH,CH=N(Aryl)BCl2(Na,B)]+BCl4, (4a: Aryl = 2,6-Me2C6H3; 9a: Aryl = 2,4,6-Me3C6H2) and [Aryl,Na=CH,C(Cl)=N(Aryl)BCl2(Na,B)]+BCl4, (4b: Aryl = 2,6-Me2C6H3; 9b: Aryl = 2,4,6-Me3C6H2) and the bicyclic species [HCa=N(Aryl)BCl2N(Aryl),Cb=(Ca,Cb)]2 (5: Aryl = 2,6-Me2C6H3; 10: Aryl = 2,4,6-Me3C6H2). Sodium amalgam reduction of borolium salts 4a,b and 9a,b afforded inseparable mixtures of the diazaboroles 2,6-Me2C6H3NaCH=CR,Nb(2,6-Me2C6H3)BCl(Na,B) (1: R = H; 6: R = Cl) and 2,4,6-Me3C6H2NaCH=CR,Nb(2,4,6-Me3C6H2)BCl(Na,B) (2: R = H; 11: R = Cl). In order to obtain pure 1 and 2, diazabutadienes 3a and 3b were slowly combined with 2 equiv. BCl3 in the same solvents at ,78 °C. The acyclic adducts Cl3BN(Aryl)=CH,CH=N(Aryl)BCl3 (7a: Aryl = 2,6-Me2C6H3; 7b: Aryl = 2,4,6-Me3C6H2) were reduced with sodium amalgam to furnish the aminoboranes Cl2BN(Aryl)CH=CH,N(Aryl)BCl2 (8: Aryl = 2,6-Me2C6H3; 12: Aryl = 2,4,6-Me3C6H2). Stirring solutions of 8 and 12 in the presence of CaH2 cleanly gave the diazaboroles 1 and 2, respectively. The novel compounds were characterized by elemental analyses and 1H-, 11B-, 13C NMR and mass spectra. The molecular structures of 1, 4a, 5 and 8 were elucidated by single X-ray diffraction analyses. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Non-Covalent Aggregation of Discrete Metallo-Supramolecular Helicates into Higher Assemblies by Aromatic Pathways: Structural and Chemical Studies of New Aniline-Based Neutral Metal(II) DihelicatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2005Miguel Vázquez Abstract Neutral manganese(II), iron(II), cobalt(II), nickel(II), zinc(II) and cadmium(II) complexes with an N -tosyl-substituted N4 -donor Schiff base containing a 4,4'-methylenedianiline residue as spacer [H2La: N,N' -bis(2-tosylaminobenzylidene)-4,4'-methylenedianiline], and the zinc(II) complex with an analogous ligand [H2Lb: N,N' -bis(2-tosylaminobenzylidene)-4,4'-oxodianiline] have been prepared by an electrochemical procedure. FAB and ESI mass spectra of the complexes show peaks due to species corresponding to a general formula [M2(La,b)2 + H]+, thereby suggesting their dinuclear nature. A detailed study of the crystal packing in the unit cell of the zinc(II) complex with H2La shows that the helicates aggregate to form discrete prismatic moieties containing three molecules held together by ,,, and ,,, interactions. Moreover, the ZnII neutral dihelicate with H2Lb forms a 3D network in the solid state due to intermolecular ,-stacking interactions. 1H NMR studies of the diamagnetic compounds reported herein have been performed. Finally, the ligand H2La and its ZnII and CdII complexes have been studied by spectrophotometric and spectrofluorimetric techniques in order to get a better understanding of the formation mechanisms of the complexes and of the nature of their fluorescence emission. Emission studies show that the ZnII and CdII dihelicates with H2La display a green fluorescence in acetonitrile solution (, = 473 nm, , = 0.03 and , = 476 nm, , = 0.01, respectively). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Comparative analysis of triacylglycerols from Olea europaea L. fruits using HPLC and MALDI-TOFMSEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 5 2010Faouzi Sakouhi Abstract MALDI-TOFMS and HPLC are two analytical methods that were used to characterize triacylglycerols (TAG) of the Meski, Sayali, and Picholine Tunisian olive varieties. The HPLC chromatograms of the oils showed the presence of 15 TAG species, among which triolein (OOO) was the most abundant (21,48%). In the Sayali cultivar, OOO was the predominant TAG species followed by POO and LOO. However, the minor TAG molecules were represented by LnLO and LnLP. MALDI mass spectra produced sodiated ([M,+,Na]+) and potassiated ([M,+,K]+) TAG molecules; only the major TAG were potassiated [OOO,+,K] ([OOO,+,K]+, [POO,+,K]+, and [LOO,+,K]+). In contrast to the HPLC chromatograms, the MALDI mass spectra showed 13 peaks of TAG. The major peak was detected at m/z,907, which corresponds to OOO with an Na+ adduct. The results from both HPLC and MALDI techniques predict the fatty acid composition and their percentages for each olive variety. Practical applications: TAG are the main components in vegetable oils. These biomolecules determine the physical, chemical, and nutritional properties of the oils. The nutritional benefits of TAG are related to DAG (moderate plasma lipid level) and esterified FA, which are intermediate biosynthetic molecules of TAG. TAG analysis is necessary to discriminate between oils of different origin, since some oils have similar FA profiles. Olive products, oils, and table olives, are the main diet sources of TAG in the Mediterranean countries. In this work, chromatographic and spectrometric methods were used for TAG analysis and characterization of Tunisian olive varieties. [source] Aliphatic Thiocarbonyl Ylides and Thiobenzophenone: Experimental Study of Regiochemistry and Methylene Transfer in CycloadditionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2005Rolf Huisgen Abstract 1,3-Dipolar cycloadditions of aliphatic or alicyclic thiocarbonyl ylides 3A-D , sterically hindered at least at one terminus , with thiobenzophenone produce both regioisomeric 1,3-dithiolanes 4 and 5. According to quantum-chemical calculations (preceding paper), a concerted cycloaddition furnishing 2,4-substituted dithiolanes 4 competes with the formation of an intermediate C,C -biradical 9 which cyclizes to the more crowded 4,5-substituted dithiolanes 5. When steric hindrance of 3 increases, the cycloaddition is superseded by ,methylene transfer', i.e., the transfer of the less hindered terminus of 3E-J to the S-atom of thiobenzophenone. The thiobenzophenone S -alkylide 11, thus formed, rapidly reacts with a second molecule ofthiobenzophenone to generate the 4,4,5,5-tetraphenyl-1,3-dithiolane 12 via the highly stabilized C,C -biradical 10. Methylene transfer occurs when the cyclization of the mixed C,C -biradical 9 requires a higher activation barrier than its dissociation to aliphatic thioketone + 11; the threshold is surprisingly well reproduced by calculations. The structural assignment of sixteen 1,3-dithiolanes is based on their formation from corresponding reactant pairs as well as on 1H and 13C chemical shifts. X-ray diffraction analyses of three spiro-1,3-dithiolanes reveal the van der Waals strain in non-bonded interactions, folding angles, shearing forces, and bond lengths. Comparison of the mass spectra of many 1,3-dithiolanes allows the reconstruction of major fragmentation pathways. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Purification and structure of the major product obtained by reaction of NADPH and NMNH with the myeloperoxidase/hydrogen peroxide/chloride systemFEBS JOURNAL, Issue 10 2001Françoise Auchère The first spectrophotometric study of the reaction of the myeloperoxidase/H2O2/Cl, system with NADPH and NMNH showed that the reaction products were not the corresponding oxidized nucleotides and that modifications would take place on the nicotinamide part of the molecule [Auchère, F. & Capeillère-Blandin, C. (1999) Biochem. J. 343, 603,613]. In this report, in order to obtain more precise information on the structural modifications and mechanism of the reaction, we focus on the purification and isolation of products derived from NADPH and NMNH by RP-HPLC. Electrospray ionization mass spectra indicated that the relative height of the peaks reflected that of the natural isotopic abundance of 35Cl and 37Cl, providing evidence that the products derived from NADPH and NMNH were monochlorinated. Moreover, calculated masses revealed the 1 : 1 addition of HOCl to the molecule. Various 1D and 2D NMR experiments provided data for the assignments of the chemical shifts of protons and carbons and the coupling constants of the protons of the chlorinated nucleotides. Further NOESY experiments allowed the characterization of the spatial structure of the chlorinated product and showed that trans HOCl addition occurred at the C5=C6 carbon double bond of the nicotinamide ring, leading to a chlorohydrin. [source] Phosphorylation and oligomerization states of native pig brain HSP90 studied by mass spectrometryFEBS JOURNAL, Issue 8 2001Cyrille Garnier HSP90 is one of the most abundant proteins in the cytosol of eukaryotic cells. HSP90 forms transient or stable complexes with several key proteins involved in signal transduction including protooncogenic protein kinases and nuclear receptors, it interacts with cellular structural elements such as actin-microfilament, tubulin-microtubule and intermediate filaments, and also exhibits conventional chaperone functions. This protein exists in two isoforms ,-HSP90 and ,-HSP90, and it forms dimers which are crucial species for its biological activity. PAGE, ESI-MS and MALDI-MS were used to study HSP90 purified from pig brain. The two protein isoforms were clearly distinguished by ESI-MS, the , isoform being ,,six times more abundant than the , isoform. ESI-MS in combination with ,,phosphatase treatment provided direct evidence of the existence of four phosphorylated forms of native pig brain ,-HSP90, with the diphosphorylated form being the most abundant. For the , isoform, the di-phosphorylated was also the most abundant. MALDI mass spectra of HSP90 samples after chemical cross-linking showed a high percentage of ,,, homodimers. In addition, evidence for the existence of higher HSP90 oligomers was obtained. [source] Synthesis and GC,MS analysis of angelates and tiglates as an aid to identification of these components in essential oilsFLAVOUR AND FRAGRANCE JOURNAL, Issue 2 2010Robert P. Adams Abstract One-hundred-and-forty-one angelates and tiglates were synthesized and their Kováts retention indices and mass spectra are presented. It is anticipated that the publication of these data will aid in the identification of angelates and tiglates from natural sources. Copyright © 2009 John Wiley & Sons, Ltd. [source] Composition of the essential oil of flowers of Chloranthus spicatus (Thunb.) MakinoFLAVOUR AND FRAGRANCE JOURNAL, Issue 4 2006Hailemichael Tesso Abstract The composition of the essential oil of the flowers of Chloranthus spicatus (Thunb.) Makino (Chloranthaceae) was investigated using capillary GC-GC/MS, preparative GC and NMR techniques. Forty-seven compounds were identified either by comparing their retention indices and mass spectra with a library of authentic samples established under identical experimental conditions or, by isolating the compounds and deriving their structures by one- and two-dimensional NMR investigations. Thus, four minor components, viz. chloranthalactone A (0.5%), isogermafurenolide (0.7%), eudesma-4(15),7(11),9-trien-12-olide (0.5%), and 7, -hydroxyeudesm-4-en-6-one (3.3%), were isolated for the first time as constituents of the essential oil of the flowers of C. spicatus and their structures established. The major components of the oil include (Z)- , -ocimene (6.3%), allo-aromadendrene (6.2%), sarisane (2-allyl-4,5-methylenedioxyanisol, 4.2%) and selina-4(15),7(11)-diene (6.4%). Copyright © 2006 John Wiley & Sons, Ltd. [source] High-Resolution LA-ICP-MS for Accurate Determination of Low Abundances of K, Sc and Other Trace Elements in Geological SamplesGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 1 2010Julia Regnery LA-ICP-MS; haute résolution de masses; matériaux géologiques de référence; verres MPI-DING Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to determine K, Sc, Ti, V, Cr, Mn, Co, Ni and Zn in geological samples. Because the isotopes of these elements and the internal standard element (Ca) often have interferences from molecular ions when determined using quadrupole or sector-field ICP-MS in low mass resolution mode, ion intensities were measured at a high mass resolution of 4000. We investigated dynamic element fractionation, type and abundance of molecular ions using different geological reference materials. Highly resolved mass spectra were especially important for accurate low-abundance measurements. As a result, maximum "critical" concentration limits for each isotope were obtained, where a mass resolution of 4000 was necessary for reliable LA-ICP-MS analysis. To test the LA-ICP-MS technique, different international reference material glasses and powdered rock reference materials were analysed. Rock powders were fused to glass beads using an Ir-strip heater. Nearly all concentration values for the reference materials agreed with the reference values at the 95% confidence level. To demonstrate routine LA-ICP-MS analysis at a mass resolution of 4000, trace element data for Hawaiian basalts are also presented. La technique de spectrométrie de masse couplée à un plasma inductif et associée à un système d'ablation laser (LA-ICP-MS) a été utilisée pour la détermination des concentrations en K, Sc, Ti, V, Cr, Mn, Co, Ni and Zn dans des échantillons géologiques. Parce que les isotopes de ces éléments et l'élément utilisé comme standard interne (Ca) ont souvent des interférences liées à la formation d'ions moléculaires lorsqu'ils sont analysés par les techniques d'ICP-MS quadripolaire ou à secteur magnétique en mode basse résolution de masses, les intensités des ions ont été mesurées en mode haute résolution de masses de 4000. Nous avons étudié le fractionnement dynamique des éléments, le type et l'abondance des ions moléculaires en utilisant différents matériaux géologiques de référence. Les spectres de masse de haute résolution ont été particulièrement importants pour les mesures précises des faibles abondances. En conséquence, les limites maximales de concentration critique pour chaque isotope ont été obtenues, dans les cas où une résolution de masse de 4000 était nécessaire pour obtenir des analyses LA-ICP-MS fiables. Pour tester la technique LA-ICP-MS proposée, différents verres et poudres de matériaux de référence internationaux ont été analysés. Les poudres de roche ont été transformées en billes de verre par fusion dans un four automatique à chauffage par filament d'iridium. Presque toutes les concentrations obtenues pour les matériaux de référence sont en accord avec les valeurs de référence de la littérature à un niveau de confiance de 95%. Pour démontrer que la méthode présentée de LA-ICP-MS à résolution de masses de 4000 peut s'utiliser en routine, nous présentons également des données d'éléments traces de basaltes Hawaïens. [source] Molecular dynamics in the formation process of single-walled carbon nanotubesHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2003Yasushi Shibuta Abstract The mechanism of the nucleation and formation of single-walled carbon nanotubes (SWNTs) was investigated using molecular dynamics simulations. When the initial state was chosen so that carbon and nickel atoms were randomly distributed in a simulation domain, the formation of a random cage structure made up of carbon atoms, which had a few nickel atoms inside it, was observed by 6 ns. The nickel atoms, which move inside or on the surface of the cage, were seen to be preventing the complete closure of the cage and its anneal into the fullerene structure. Further, in order to observe a longer time-scale growth process, the simulation cell was artificially shrunk by the progress of simulation so that collisions between precursor clusters were promoted to comply with the limitation in the calculation time. Collisions of the imperfect random-cage clusters led to an elongated tubular cage structure, which could be regarded as an initiation of SWNTs. The simulation results were compared with FT-ICR mass spectra of the positive clusters generated by a laser-vaporization supersonic-expansion cluster beam source. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(8): 690,699, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10123 [source] Preparation and (E/Z)-Isomerization of the Diastereoisomers of ViolaxanthinHELVETICA CHIMICA ACTA, Issue 1 2004Péter Molnár Violaxanthin A (=(all- E,3S,5S,6R,3,S,5,S,6,R)-5,6,:,5,,6,-diepoxy-5,6,5,,6,-tetrahydro- ,,, -carotene-3,3,-diol =syn,syn- violaxanthin; 5) and violaxanthin B (=(all- E,3S,5S,6R,3,S,5,R,6,S)-5,6,:,5,,6,-diepoxy-5,6,5,,6,-tetrahydro- ,,, -carotene-3,3,-diol=syn,anti- violaxanthin; 6) were prepared by epoxidation of zeaxanthin diacetate (1) with monoperphthalic acid. Violaxanthins 5 and 6 were submitted to thermal isomerization and I2 -catalyzed photoisomerization. The structure of the main products, i.e., (9Z)- 5, (13Z)- 5, (9Z)- 6, (9,Z)- 6, (13Z)- 6, and (13,Z)- 6, was determined by their UV/VIS, CD, 1H-NMR, 13C-NMR, and mass spectra. [source] Synthesis and biological activity of some triarylantimony dipyrazolecarboxylatesHETEROATOM CHEMISTRY, Issue 4 2002Yong-Qiang Ma A series of triarylantimony dipyrazolecarboxylates was synthesized by the reaction of pyrazolecarboxylic acid with triarylantimony dibromides in the presence of potassium hydroxide. The structures of the title compounds were confirmed by elemental analysis, 1H NMR, IR, and mass spectra. Some of these compounds were found to possess antibacterial activity. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:299,301, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10033 [source] | ||||||||||||||||||||||||||||||||||||||||