bluuebunny/crossref_metadata_2025 huggingface dataset:
Complete Oxidation of Ethylene at Temperatures below 100 °C over a Pt/Ce0.64Zr0.16Bi0.20O1.90/γ-Al2O3 Catalyst
Authors: Imanaka Nobuhito , Masui Toshiyuki , Terada Asako , Imadzu Hayato
Published: December 2007

A Pt/Ce0.64Zr0.16Bi0.20O1.90/γ-Al2O3 catalyst was prepared in order to establish complete oxidation of ethylene at temperatures below 100 °C. Ethylene was completely oxidized over the catalyst as low as at 65 °C, while over Pt/γ-Al2O3, which has been well known as an active oxidation catalyst, complete oxidation was achieved at 145 °C.
Micrometer-scaled Channel Lengths of Organic Field-effect Transistors Patterned by Using PEDOT/PSS Microfibers
Authors: Yan Hu , Kagata Tsubasa , Mori Yusaku , Harashina Yuko , Hara Yusuke , Okuzaki Hidenori
Published: December 2007

We have easily fabricated channel patterns of organic field-effect transistors (OFET), in which channel lengths were ca. 5 μm, by using wet-spun poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) microfibers with diameters of ca. 5 μm. Pentacene-based OFETs with a bottom-contacted configuration, fabricated on the channel patterns, showed a hole mobility of 10−3 cm2 V−1 s−1 simply reflecting FET characteristics of the pentacene, and showed large current of 8 μA (VDS=−50 V; VG=−50 V) reflecting shorter channel length of the devices.
Overall Water Splitting by RuO2-loaded Hexagonal YInO3 with a Distorted Trigonal Bipyramid
Authors: Arai Naoki , Saito Nobuo , Nishiyama Hiroshi , Shimodaira Yoshiki , Kobayashi Hisayoshi , Inoue Yasunobu , Sato Kazunori
Published: December 2007

RuO2-loaded hexagonal YInO3 consisting of a distorted InO5 trigonal bipyramid was found to be photocatalytically active in the water-splitting reaction. The characteristic role of the InO5 structure in the photocatalytic performance is described.
Structural Characterization of Aromatic Polyester Resins by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry
Authors: Laine Olli , Vainiotalo Pirjo , Österholm Heidi , Järvinen Hannele
Published: December 2007

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry was used to characterize average molecular weights and end-groups of synthetic aromatic polyesters and the same characteristics were also determined for acetylated polyester samples. In addition, the progress of a polyesterification reaction was followed by mass spectrometry by investigating samples taken from the reaction mixture at different reaction times. Average molecular weights were compared with those measured by gel-permeation chromatography (GPC) and the results of quantitative end-group analysis were considered with the acid values of the polyesters. MALDI measurements were carried out using two different matrix compounds, 2,5-dihydroxybenzoic acid (DHB) and 2-(4-hydroxyphenylazo) benzoic acid (HABA). Different matrices and derivatization of the polyester influenced the width of the polymer distribution determined by mass spectrometry and further affected the proportions of differently terminated oligomers, in addition to the average molecular weight. The relative amount of the most abundant oligomer species was increased when the polymer distribution width was increased.
Simulation of the Collisional Cooling Effect for Binary and Ternary Buffer Gas Mixtures in a Quadrupole Ion Trap Mass Spectrometer
Authors: Wu Hui-Fen , Chen Li-Wei , Wang Jhen-Chen , Lin Ya-Ping
Published: December 2007

Simulation of the collisional cooling effect using binary and ternary buffer gas mixtures in the ion trap mass spectrometer was performed using the SIMION 6.0 program, in which a 3D collision model was used to describe the ion–buffer gas collisions. Computation of the ion kinetic energy based on the Langevin theory under various conditions was used to account for the effects of mixed buffer gases on ion-collisional cooling. The addition of small amounts (8–9%) of one or two heavier target gases (nitrogen, argon or SF6) to the 1 mtorr helium buffer gas in the ion trap can greatly improve the collisional cooling effects. The kinetic energy of ions can be reduced to close to 0 eV. Although the use of ternary buffer gas mixtures can also effectively improve the collisional cooling effects, the use of binary buffer gas mixtures is the better choice due to convenience and lower cost in real ion trap applications.
Identification of Morphine and Morphine-6-Glucuronide in the Adrenal Medullary Chromaffin PC-12 Cell Line by Nano-Electrospray Ionization Double Quadrupole Orthogonal-Acceleration Time-of-Flight Mass Spectrometry
Authors: Zhu Wei , Goumon Yannick , Stefano George B. , Baggerman Geert , Zenk Meinhart H.
Published: December 2007

Using nano-electrospray ionization double quadrupole orthogonal-acceleration time-of-flight mass spectrometry, we were able to detect sub-nanogram levels of endogenous morphine and its metabolite morphine-6-glucuronide in the rat pheochromocytoma cell line. Furthermore, fragmentation of endogenous morphine-6-glucuronide (462.14 Da) by collision-induced dissociation yields morphine (286.14 Da) obtained from the cell samples and with the authentic material, further demonstrating the presence of endogenous morphine. The incubation medium was devoid of this material. This methodology represents a sensitive and accurate method to detect trace amounts of endogenous opiates at subnanogram levels in biological samples.
Isotopic Deconvolution of Matrix-Assisted Laser Desorption/Ionization Mass Spectra for Substance-Class Specific Analysis of Complex Samples
Authors: Wehofsky Marco , Hoffmann Ralf , Hubert Martin , Spengler Bernhard
Published: December 2007

The theoretical isotopic pattern and its variance was determined for peptides and other substance classes. The mass-dependent mean pattern was used to isotopically deconvolute matrix-assisted laser desorption/ionization (MALDI) spectra and MALDI post-source decay (PSD) spectra from complex peptide samples. Application of a slightly modified algorithm to electrospray ionization spectra will be described in a later paper. The method was found to be especially useful in suppressing noise and signals from other substance classes, and in separating overlapping isotopic patterns in highly complex samples. The method can be used for automatic determination of monoisotopic masses in, for example, proteomics work and the improvement of graphical quality and clarity in presentation and manual evaluation of mass spectra. A fast computer algorithm was developed to demonstrate the efficiency of the method in data filtering and spectra deconvolution for the case of MHC(major histocompatibility complex) peptide identification and PSD analysis. The method has some advantages over other approaches, especially due to its simplicity, universality and processing speed.
Electron Impact Ionization of Dicyclopentadienyl-Manganese and Cyclopentadienyl-Manganese-Tricarbonyl Compared with Dimanganese-Decacarbonyl: Appearance Energies, Bond Energies and Enthalpies of Formation
Authors: Opitz Joachim
Published: December 2007

Electron impact (EI) ionization mass spectra, metastable-ion decays and appearance energies are reported for the title compounds. Gas-phase formation enthalpies (Δ Hf) and bond energies (as dissociation energies) are derived from these data. Obtained Δ Hf values for the parent compounds are (–15.65 ± 0.2) eV for Mn2(CO)10, (2.85 ± 0.3) eV for Cp2Mn (Cp = C5H5 = cyclopentadienyl ligand) and (–3.91 ± 0.3) eV for CpMn(CO)3. The mean (Mn–CO) bond energy is 0.97 eV for Mn2(CO)10. In cations, the mean (Mn–CO)+ bond energy ranges from 0.75 to 0.80 eV for Mn2(CO)10 and CpMn(CO)3, respectively. In Cp2Mn+ the dissociation energies are 2.14 eV for the first Cp ligand and 3.21 eV for the second. In the neutral Cp2Mn, 2.12 eV is needed for the detachment of a first Cp ligand and 3.00 eV for the second. The results for the second ligand are valid for the elimination of Cp from CpMn(CO)3 as well.
Specific Electron Ionization-Induced Fragmentation of Secondary Alcohol Methoxyacetates
Authors: Zaikin Vladimir G. , Borisov Roman S. , Luzhnov Vladislav V.
Published: December 2007

The electron ionization-induced fragmentations of methoxyacetates derived from various secondary aliphatic alcohols have been studied with the aid of deuteration experiments, high-resolution measurements and metastable ion analysis. It was shown that the formation of the methoxyacetic acid cation-radical or protonated methoxyacetic acid as well as α-cleavages near to the acyloxy group (processes which are characteristic for many esters) do not occur for these compounds. Unexpectedly, the elimination of methoxyacetic acid or the methoxyacetoxy radical from the molecular ions appeared to proceed to a nearly equal extent. The spectra of methoxyacetates of 2-, 3- and 4-alkanols contain peaks at m/z 89, 103 and 117 (and M −71), respectively, of a moderate intensity. Their origin was proved to be due to α-cleavages near to the methoxyacetoxy group followed by skeletal rearrangement and elimination of CO to form resonance-stabilized ions (R–CH=O+–CH2–O–CH3↔R–CH2–O+=CH–O–CH3).
Evaluating the Role of the Ligand in the Fragmentation Reactions of Platinum(II) Complexes of Aliphatic Dipeptides. Electrospray Ionization Tandem Mass Spectrometry of [Pt(L3)M]2+ and [Pt(L3)M — H]+ Ions [L3 = (H3N)3, Diethylenetriamine and Terpyridine; M = Gly-Gly, Ala-Gly and Gly-Ala]†
Authors: Styles Michelle L. , O'Hair Richard A.J. , McFadyen W. David
Published: December 2007

Incubation of simple aliphatic dipeptides (M) with [Pt(L3)Cl]+ complexes (where L3 = terpyridine, diethylenetriamine or triamine) results in the formation of platinated dipeptides as detected by electrospray ionization mass spectrometry. Although the [Pt(L3)M – H]+ and [Pt(L3)M]2+ ions represent less than 1% of the total-ion current, they can readily be mass selected and subjected to collision-induced dissociation in an ion trap mass spectrometer. The nature of the coordinating ligands and the charge state have profound effects on the types of fragmentation reactions observed. Thus, the tridentate ligands terpyridine (terpy) and diethylenetriamine (dien) induce dissociation of the peptide bond and the C-terminal OH bond in the [Pt(L3)M]2+ ions, whereas the complex containing the three unidentate ammonia ligands fragments via neutral and charged ammonia loss. [Pt(terpy)M – H]+ ions fragment via peptide bond cleavage and also through a C-terminal rearrangement reaction for gly-ala and glycyl-N-methylglycine, but not for ala-gly. In contrast, [Pt(dien)M – H]+ ions fragment via loss of the neutral dipeptide while [Pt(NH3)3M – H]+ ions fragment via loss of NH3.
Toward Efficient Analysis of >70 kDa Proteins with 100% Sequence Coverage
Authors: Forbes Andrew J. , Mazur Matthew T. , Kelleher Neil L. , Patel Hiten M. , Walsh Christopher T.
Published: December 2007

For complete characterization of larger proteins, primary structural analysis by mass spectrometry must be made more efficient. A straightforward approach is illustrated here using two proteins of 159 and 199 kDa with five and nine lysine (Lys) residues, respectively. These proteins were degraded by Lys-C to mixtures of peptides ranging in size from 5 to 48 kDa, whose multiply-charged ions (from electrospray ionization) are far more amenable than the intact proteins to direct interrogation in a Fourier-transform mass spectrometer. For the 199 kDa PchF of ∼ 60% purity, an unfractionated Lys-C digest gave 106 isotopic distributions from 71 components (most of which were below 6 kDa); 15% sequence coverage was obtained. For the > 90% pure PchE (159 kDa), complete sequence coverage was obtained from six Lys-C peptides of 5, 8, 26, 32, 40 and 48 kDa, with all but the largest of these measured at isotopic resolution on a 4.7 Tesla instrument. Practical strategies for implementing this characterization strategy on a proteomic scale are considered.
Analysis of Protein Sequences and Protein Complexes by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry
Authors: Belghazi Maya , Bathany Katell , Hountondji Codjo , Grandier-Vazeille Xavier , Manon Stéphen , Schmitter Jean-Marie
Published: December 2007

In the context of proteome analysis, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry can fulfil the two tasks of primary structure verification and protein identification. As an illustration of the first of these tasks, the sequence of E. coli isoleucyl-tRNA synthetase, a protein with 15 reported sequence conflicts, has been established by means of MALDI mass mapping. The identification of mitochondrial proteins participating in a yeast supramolecular complex exhibiting NADH dehydrogenase activity highlights the performance of MALDI mass spectrometry for the second task. The spectral suppression phenomenon occurring for complex peptide mixtures analyzed by MALDI is discussed, as well as the role of post-source decay (PSD) analysis for confident protein identification.
Simplified Sample Preparation Method for Protein Identification by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry: In-Gel Digestion on the Probe Surface
Authors: Stensballe Allan , Jensen Ole Nørregaard
Published: December 2007

Identification and detailed characterization of complex mixtures of proteins separated by polyacrylamide gel electrophoresis (PAGE) require optimized and robust methods for interfacing electrophoretic techniques to mass spectrometry. Peptide mapping by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (TOF MS) is used as the first protein screening method in many laboratories because of its inherent simplicity, mass accuracy, sensitivity and relatively high sample throughput. We present a simplified sample preparation method for MALDI MS that enables in-gel digestion of protein samples directly on the MALDI MS metal probe. Removal of detergent and reagents as well as protein reduction and S-alkylation were performed prior to cutting of protein samples from the polyacrylamide gel slab. The general utility of this approach was demonstrated by on-probe digestion and MALDI MS peptide mapping of femtomole amounts of standard proteins isolated by sodium dodecyl sulfate (SDS) PAGE. A representative set of 47 human proteins obtained from a silver stained two-dimensional electrophoretic gel was analyzed by the new method and resulted in a success rate for protein identification similar to that obtained by the traditional protocols for in-gel digestion and MALDI peptide mass mapping of human proteins, i.e. approximately 60%. The overall performance of the novel on-probe digestion method is comparable with that of the standard in-gel sample preparation protocol while being less labor-intensive and more cost-effective due to minimal consumption of reagents, enzymes and consumables. Preliminary data obtained on a MALDI quadrupole-TOF tandem mass spectrometer demonstrated the utility of the on-probe digestion protocol for peptide mass mapping and peptide sequencing on this instrument. Automation of the on-probe protein digestion procedure and its combination with automated MALDI tandem mass spectrometry should be advantageous in proteomics research aimed at the systematic identification and analysis of large sets of proteins from electrophoretic gels.
Limited Acid Hydrolysis as a Means of Fragmenting Proteins Isolated upon Proteinchip® Array Surfaces
Authors: Lin Shanhua , Tornatore Pete , Weinberger Scot R. , King Daniel , Orlando Ron
Published: December 2007

ProteinChip Array technology enables protein purification, protein profiling and biomarker discovery on a convenient biochip platform. Traditional proteomic approaches towards protein identification rely upon the generation of peptides through the use of specific proteases. However, for a variety of reasons, the digestion of proteins bound to planar arrays using specific proteases, such as trypsin, has proven to be difficult, at times providing little or no protein digestion at all. Additionally, should more than one protein be present on the array surface, the digestion product consists of peptides from different proteins, adding another dimension of complexity to database mining approaches. These factors have driven our group to explore alternative means of on-chip protein digestion. In this article, we describe an approach to generating peptide maps by limited acid hydrolysis. Depending upon the adsorbed protein, this method requires between 500 femtomol to 5 picomol of protein for on-chip hydrolysis. Besides generating several internal peptide fragments, limited acid hydrolysis also has the advantage of generating peptide ladders from the N- or C-terminus of the protein. From these ladders, a partial primary sequence of the protein can be directly derived using analysis by a simple laser desorption/ionization mass spectrometer. Furthermore, tandem mass spectrometry (MS/MS) can be performed on several internal peptide fragments, thus facilitating the identification of several proteins within a mixture. Based upon the preliminary results of this work, we continue to explore the possibility of using limited acid hydrolysis to identify unknown proteins captured on ProteinChip Array surfaces.
Multiple Separations Facilitate Identification of Protein Variants by Mass Spectrometry
Authors: Zhang Zhongli , Smith David L. , Smith Jean B.
Published: December 2007

Identification of variant proteins from complex biological samples promises to contribute much to our understanding of the etiology of pathological states. Characterization of variants, due either to genetic mutations in protein sequences or to post-translational modifications, is considerably more difficult than the simple protein identifications typical of most current proteomic investigations. Identification of a few peptides by database retrieval is not adequate when the goal is to have a complete understanding of the modifications of the protein. Although one advantage of mass spectrometry is its ability to obtain specific responses to several components, the complexity of biological samples is often overwhelming, resulting in spectra lacking useful information. For complex mixtures, isolation procedures before mass spectrometric analysis may need to include a variety of chromatographic and electrophoretic separation techniques. In this report, we illustrate how several preparative steps were essential for obtaining information about modified human lens β-crystallins. The preparative techniques prior to mass spectrometry included size-exclusion chromatography, reversed-phase chromatography, two-dimensional gel electrophoresis, in situ digestion of the proteins and peptide trapping and washing before a final reversed-phase high-performance liquid chromatographic separation on-line to the mass spectrometer. This approach for isolation and analysis, when customized for other proteins, should find application in many studies where protein variants of complex mixtures are to be identified.
The Effects of Transcription Regulating Genes PDR1, pdr1-3 and PDR3 in Pleiotropic Drug Resistance
Authors: Nawrocki Arkadiusz , Fey Stephen J. , Larsen Peter Mose , Goffeau André , Roepstorff Peter
Published: December 2007

Mutations in the yeast PDR1 or PDR3 genes lead to acquisition of resistance towards various unrelated cytotoxic compounds. The broad range and different properties of these compounds indicate the existence of mechanisms which protect cellular targets, neutralise or expel the compounds from the cell. In wild type and pdr mutants, 83 proteins, out of 2706 detected by 2D gel electrophoresis, were differentially expressed. 53 of these could be identified by mass spectrometry. The functions of these 53 proteins fall into several metabolic groups demonstrating that drug-resistance phenotype is a mosaic response derived from such diverse functions as stress defence, endocytosis, oxidation and reduction, amino-acid synthesis and mitochondrial biogenesis. The patterns of synthesis of the selected proteins clearly demonstrates the complex interaction between Pdr1p and Pdr3p in exerting their regulatory functions. The data also indicate that, in the Saccharomyces cerevisiae pleiotropic drug resistance (PDR) phenomenon, translational events exert a more decisive effect than transcription in regulating the levels of active forms of the proteins involved.
Structural Modifications of Methanococcus Jannaschii Flagellin Proteins Revealed by Proteome Analysis
Authors: Giometti Carol S. , Tollaksen Sandra L. , Babnigg Gyorgy , Reich Claudia I. , Olsen Gary J. , Lim Hanjo , Yates John R.
Published: December 2007

Methanococcus jannaschii is an autotrophic archaeon originally isolated from an oceanic thermal vent. The primary metabolic pathway for energy production in this hyperthermophilic microbe is methanogenesis from H2 and CO2. As an autotroph, M. jannaschii requires only CO2 as a carbon source for synthesizing all necessary biomolecules. Changes in the environmental availability of these molecules can be expected to activate regulatory mechanisms manifested as the up and down regulation of specific genes and the concomitant increase and decrease in abundance of the corresponding proteins. In our analysis of the proteome of M. jannaschii, we have observed significant changes in the abundance of a common subset of predominant proteins in response to reduced H2 concentration, limited ammonium availability and the stage of cell growth (exponential compared with stationary). The masses of tryptic peptides from these proteins match those predicted by M. jannaschii genome open reading frames annotated as flagellin B1 (MJ0891) and flagellin B2 (MJ0892). Multiple proteins with different isoelectric points and molecular weights match each of these proteins and the abundance of these protein variants changes with growth conditions. These data indicate that structural modifications altering both the isoelectric point and size of the M. jannaschii flagellin B1 and B2 proteins occur in response to growth conditions and growth stage of M. jannaschii and further suggest the regulation of M. jannaschii motility through structural modifications of the building blocks of the flagella.
Dissociation Reactions of Low-Energy Pentenyl Methyl Ether Radical Cations C5H9OCH3•+
Authors: Bowen Richard D. , Trikoupis Moschoula A. , Terlouw Johan K.
Published: December 2007

The dissociation chemistry of the low-energy C5H9OCH3•+ ions generated from the 13 isomeric pentenyl methyl ethers derived from stable alkenols has been studied. This was done by examining their metastable ion characteristics, in conjunction with 2H and 13C-labelling as well as collision-induced dissociation and neutralisation–reionisation experiments. The influence of the position and substitution pattern of the double bond on the chemistry of these C6H12O•+ species is considered. The closely similar reactions of C2H5CH=CHCH2OCH3•+, 3•+, CH2=CH–CH(C2H5)OCH3•+, 4•+, and CH2=C(C2H5)CH2OCH3•+, 13•+, point to a common chemistry, which is rationalised in terms of facile 1,2-H and 1,2-C2H5 shifts via distonic ions. Each of the other isomers displays a distinct, though often related, chemistry. The eight allylic ionised ethers easily lose CH3• to produce C5H9O+ oxonium ions, whose structure was established by CID experiments; ions 3•+ / 4•+ / 13•+ also readily expel C2H5• to give C4H7O+ ions of structure CH2=CH–C+(H)OCH3. Elimination of CH3OH is also significant for 3•+ / 4•+ / 13•+ and for (CH3)2C=CHCH2OCH3•+, 8•+, and CH3CH=C(CH3)CH2OCH3•+, 11•+. Besides expelling CH3• and/or C2H5• and CH3OH, the three homoallylic isomers undergo dissociations which are (almost) absent for their allylic counterparts: thus, both CH3CH=CH(CH2)2OCH3•+, 2•+, and CH2=CH–CH(CH3)CH2OCH3•+, 10•+, lose H• and H2O, whereas CH2=C(CH3)CH2CH2OCH3•+, 7•+, is unique in predominantly losing CH2O. For the losses of CH2O and H2O mechanisms are proposed in which ion–neutral complexes of the type [C5H10•+ / CH2O] and [C6H10•+ / H2O] are key intermediates. The behaviour of the non-(homo)allylic isomer, CH2=CH(CH2)3OCH3•+, 1•+, is similar to that of 2•+ but the reactions occur in different proportions. A mechanism for the facile loss of an alkyl radical from 1+ is proposed in which 1,4-H shifts and distonic ions as well as communication with ionised cyclopentyl methyl ether, 14•+, play an important role.
The Determination of Proton Affinities of Secondary Alcohols from the Dissociation of Proton-Bound Molecular Trios. A New Application of the Kinetic Method
Authors: Cao Jie , Holmes John L.
Published: December 2007

The kinetic method for determining proton affinity ( PA) values requires that the competing dissociations of proton-bound pairs of bases, AH+Bn, essentially only lead to AH+ and BnH+ ions. The method fails for secondary alcohols because other reactions, involving rearrangement of the AH+Bn ion, are dominant. It was found that proton-bound trios of bases, A2H+Bn, (which incorporate secondary alcohols Bn with a primary alcohol, A) do not suffer from this disadvantage. The proton-bound trios decomposed cleanly, to yield only A2H+ and AH+Bn ions. Application of the kinetic method to these competing reactions allowed the PA values for the secondary alcohols to be determined using the appropriate molecular-pair proton affinity [ MPPA] values. The MPPA is the negative of the enthalpy change, [–Δ H], accompanying the formation of a proton-bound pair from the component alkanols and a proton. These were readily estimated using known binding energies, D[AH+–Bn] and established PA values for n-alkanols. In the present brief study, PA values for isopropanol, cyclobutanol and cyclopentanol were measured to be 796, 792 and 798, all ± 6 kJ mol−1. The results for the cyclic alcohols relate well with the available data from similar compounds, where the C3–C5 rings display lower PA values than their acyclic analogues. This effect is attributed to restricted charge delocalization in the small rings.
Studies of Unsaturated C-Aryl Glycosides by Fast-Atom Bombardment Mass Spectrometry
Authors: Moineau Christophe , Sinou Denis , Becchi Michel , Bobenrieth Marie Joëlle
Published: December 2007

Fast-atom bombardment (FAB) spectra, FAB mass-analyzed ion kinetic energy (FAB MIKE) spectra and FAB MIKE spectra with collision-activated dissociation (FAB CAD-MIKE) were obtained for some unsaturated anomeric C-aryl glycosides. Although the FAB MIKE and FAB CAD-MIKE spectra of the [M + H]+ ion showed no differences, differentiation of the regioisomers and anomers was possible by analyzing the MIKE and CAD-MIKE spectra of the [M + Li]+ or [M + Na]+ ions.
Characterization of Betidamino Acid-Containing Somatostatin and Gonadotropin-Releasing Hormone Analogs with Electrospray Mass Spectrometry and Tandem Mass Spectrometry
Authors: Craig A. Grey , DeBoard Ryan , Kirby Dean , Jiang Guangcheng , Koerber Steven C. , Rivier Jean E.
Published: December 2007

We report the electrospray mass spectra and tandem mass (MS/MS) spectra of a series of chemically-stable somatostatin (SRIF) and gonadotropin-releasing hormone (GnRH) analogs which incorporate acylated or alkylated/acylated aminoglycine residues (betidamino acids) into their structure . In the case of SRIF, we compare the betidamino acid-containing analogs with the equivalent peptide without the betide-type linkage. We observe significant differences in the fragmentation patterns of each class of compound. We extend this study by comparing a variety of different betidamino acid-containing GnRH analogs to investigate the effects of different acyl groups, chirality and methylation of the side-chain nitrogen of amino glycine on the gas-phase stability of these protonated peptide molecules.
Ion Rearrangement at the Beginning of Cluster Formation: Methyl Substitution Effects on the Internal SN2 Reaction in the Proton-Bound Dimers of Acetonitrile and Alcohols
Authors: Ochran Richard A. , Mayer Paul M.
Published: December 2007

Mass spectrometry and ab initio calculations have been employed to investigate the unimolecular decompositions of proton-bound dimers consisting of acetonitrile with n- and i-propanol. Common to both systems is a competition between dissociation of the hydrogen bond in the proton-bound dimer and isomerization to (CH3CNR)(H2O)+ [R = CH2CH2CH3 and CH(CH3)2]. The minimum-energy-reaction pathways for the isomerization in these two systems, as well as those for the dimers containing methanol and ethanol, are presented and compared. The dominant isomerization pathway for these ions is an internal SN2 reaction that proceeds via a stable intermediate CH3CN•••ROH2+ ion [R = CH3, CH2CH3, CH2CH2CH3 and CH(CH3)2]. The mass spectra for the four butanol-containing dimers ( n-, s-, i- and t-butanol) follow similar behavior.
Gas-Phase Reactivity of Copper Cations with Ketones
Authors: Fordham P. , Deschasse M. , Haldys V. , Tortajada J. , Morizur J.-P.
Published: December 2007

Gas-phase ion–molecule reactions between copper ions and ketones were investigated. Organometallic adducts were prepared using a chemical ionisation/fast-atom bombardment source. Abundant pseudo-molecular ion adducts were observed in the Cu+-chemical ionisation mass spectra and their unimolecular decompositions were studied by tandem mass spectrometry. Mass-analysed ion kinetic energy spectroscopy revealed diagnostic fragmentation patterns. Losses of alkenes, losses of alkanes and dehydrogenation and dehydration reactions were observed, as well as eliminations of CuR (R = C nH2 n + 1). The rich reaction chemistry of the cationised ketones enabled differentiation of the majority of the linear and branched ketone isomers studied. Isotope-labelled derivatives were employed to elucidate fragmentation mechanisms.
Gas-Phase Reactivity of Glycosides and Methyl Glycosides with Cu+, Ag+ and Pb2+ Ions by Fast-Atom Bombardment and Tandem Mass Spectrometry
Authors: Salpin Jean-Yves , Boutreau Laurence , Haldys Violette , Tortajada Jeanine
Published: December 2007

The analytical potential of the complexation of three isomeric monosaccharides (D-glucose, D-galactose, D-fructose)and two methyl glycosides ( O-methyl-α-D-glucose and O-methyl-β-D-glucose)by three metal ions, Ag+, Cu+ and Pb2+, has been investigated by fast-atom bombardment (FAB)ionization and tandem mass spectrometry. Our results have shown that the unimolecular reactivity of Ag+ complexes allows the characterization of the C(4)stereochemistry of the pyranose ring, whereas a distinction between D-glucose and D-fructose is not achieved. On the other hand, each of the three [Cu + monosaccharide]+ complexes exhibits specific dissociation patterns. We have also observed that Pb2+ ions induce the richest reactivity and are of particular interest for the identification of the three isomers. Finally, this study has demonstrated that the stereochemistry of the anomeric center of O-methyl-D-glucose is easily determined by reaction with Ag+ or Pb2+ ions. Several mechanisms are proposed to account for the main fragmentations of cationized glucose.
Gas-Phase Reaction of Acetaldehyde with Silicon-Containing Ions
Authors: Leblanc D. , Denhez J.P. , Audier H.E.
Published: December 2007

CH2=Si(CH3)OSi(CH3)2+ ions 1 were formed in the external source of a Fourier-transform ion cyclotron resonance (FT-ICR)mass spectrometer by fragmentation of (CH)3SiOSi(CH3)3. In the cell, their reactions with acetaldehyde were studied by using labeled reactants and compared with those with acetone, studied in previous work, which gives a general view of the reactions of ion 1 with carbonyl compounds. In contrast with the behavior of the corresponding carbon-containing ions, the results confirm facile 1,3-methyl group transfers from silicon to silicon. Otherwise, the silicon-containing adducts often eliminate C nH2 n. This process, not observed in (C,O,H)-containing ions, is studied by using selectively deuterated reactants.
Do Thermally-Labile 1,4-Benzodiazepines Rearrange under Electrospray and Particle Bombardment?
Authors: Bourcier Sophie , Hoppilliard Yannik , Kargar-Grisel Taraneh , Pechiné Jean Marie , Perez Felix
Published: December 2007

Nordiazepam (N), diazepam (D), lorazepam (L), oxazepam (O)and temazepam (T)are 1,4-benzodiazepines. L, O and T are substituted in position 3 of the seven-membered ring by a hydroxyl group and are known to be thermally unstable. N and D are unsubstituted in position 3 and are expected to be thermally stable. We have studied the stability of all these molecules under electrospray conditions and under particle bombardment (MeV ions and UV photons). The fragmentations induced by low energy collision-induced dissociation and high energy collision-activated dissociation of molecules protonated by electrospray were compared with the spontaneous fragmentations of these molecules ionized by particle bombardment. The fragmentation mechanisms were determined using labeled compounds and by means of ab initio calculations using 1,4-diazepine and 3-hydroxy-1,4-diazepine as models. The fragmentation is dramatically dependent upon the substitution in position 3 and upon the internal energy of protonated molecules. At low collision energies, the non-hydroxylated benzodiazepines eliminate CO by opening of the diazepine ring whereas 3-hydroxy-1,4-benzodiazepines eliminate water after ring contraction. At high collision energies, all protonated benzodiazepines eliminate a hydrogen atom by simple bond cleavage. Molecular orbital calculations give arguments in favor of an isomerization in the gas phase of the protonated 3-hydroxybenzodiazepines and of a partial thermal decomposition of 1,4-benzodiazepines occurring before protonation under particle bombardment.
Capture and Analysis of Low Molecular Weight Ligands by Surface Plasmon Resonance Combined with Mass Spectrometry
Authors: Sönksen Carsten P. , Roepstorff Peter , Markgren Per-Olof , Danielson U. Helena , Hämäläinen Markku D. , Jansson Östen
Published: December 2007

The combination of biomolecular interaction analysis (BIA)by surface plasmon resonance (SPR)and nano-electrospray ionization ion trap mass spectrometry (nanoESI-Ion Trap MS)as well as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS)is demonstrated for the binding of low molecular weight inhibitors (∼ 600 Da) to HIV-1 protease. Inhibitors were captured on sensor chips of a manual or an automated SPR biosensor, to which HIV-1 protease was immobilized. Compounds and buffer components that bound unspecifically to the sensor surface were removed and the inhibitors were eluted in a minimal volume (3 μL), between air bubbles, in order to prevent dispersion of analyte into buffer eluent. Molecular weights were subsequently determined by mass spectrometry, structural information was obtained by MALDI-ToF post-source decay as well as by electrospray ionization tandem mass spectrometry (MS/MS)analysis. Furthermore, competition experiments, using a mixture of different ligands, demonstrated that the peak intensities in the MALDI-ToF spectrum could be used for relative quantification of the amount of the different ligands bound to the immobilized target. Methodology for automated capture and elution of analytes was developed and evaluated.
Calmodulin-RS20-Ca4 Complex in the Gas Phase: Electrospray Ionisation and Fourier Transform Ion Cyclotron Resonance
Authors: Nousiainen Marjaana , Vainiotalo Pirjo , Feng Xidong , Derrick Peter J.
Published: December 2007

Dissociation of the complex between calmodulin, four calcium ions and the synthetic peptide RS20 derived from the phosphorylation site of smooth-muscle myosin light-chain kinase was studied by sustained off-resonance irradiation/collision-induced dissociation (SORI-CID)and electrospray ionisation (ESI)Fourier transform ion cyclotron resonance (FT-ICR)mass spectrometry. Gas-phase dissociation of isolated ions of calmodulin-RS20-Ca4 in the 8+ charge state yielded fragments via two parallel pathways; calmodulin-Ca4 complex ions in 5+ and 6+ charge states and RS20 ions in 2+ and 3+ charge states were detected at high resolution. The results are interpreted as indicating that RS20 binding to calmodulin in this complex is specific, involving particular non-covalent interactions that decompose readily during collision-induced dissociation. More specifically, it is proposed that the gas-phase dissociation of calmodulin-RS20-Ca4 complex reflects the existence in vacuo of salt bridges.
Analysis of Oligomeric and Polymeric Tannins of Grape Berries by Liquid Chromatography/Electrospray Ionization Multiple-Stage Tandem Mass Spectrometry
Authors: Perret Camille , Tabacchi Raphael , Pezet Roger
Published: December 2007

Tannins are highly polar, water-soluble and thermally-labile compounds which are difficult to ionize. Mass spectrometry is very useful for the structural determination of such compounds. In this article, we describe a sensitive method for the identification of tannic composition in grape berries (var. Gamaret). An ion trap, equipped with an electrospray ionization (ESI) interface, allowed us to develop multiple-stage fragmentation (MS n), which provided useful structural information. This technique was applied to a mixture of proanthocyanidins and proanthocyanidin gallate oligomers (B-type) generating identical ion sequences for each parent ion.
Mean Charge State and Charge State Distribution of Proteins as Structural Probes. An Electrospray Ionisation Mass Spectrometry Study of Lysozyme and Ribonuclease A
Authors: Halgand F. , Laprévote O.
Published: December 2007

Analysis by electrospray mass spectrometry of lysozyme and ribonuclease A showed that the presence of triethylammonium cations leads to a spectacular decrease of the protein charge state compared with this obtained with ammonium cations, thus confirming the role played by the presence of bases (ammonia or triethylamine) in the solvent phase. However, despite their very different compositions in basic amino acid residues, these proteins gave rise to identical charge states and charge state distributions under non-denaturing solvent conditions. Unexpectedly, the main difference between the two investigated proteins corresponded to their behaviour under denaturing solvent conditions, with lysozyme leading to narrower charge state distributions than ribonuclease A. The use of the mean charge state values and charge state distributions for structure investigation of native proteins is discussed.
Intramolecular Electron-Transfer-Induced Cleavage of Dioxetanes Observed in Fast-Atom Bombardment Tandem Mass Spectrometry
Authors: Ohashi Mamoru , Takanashi Masakazu , Watanabe Nobuko , Matsumoto Masakatsu , Saisu Takumi , Niwa Haruki
Published: December 2007

Phenolic spiroadamantyl-substituted dioxetanes are well known base-induced chemiluminescent compounds. Fast-atom bombardment collision-induced dissociation tandem mass spectrometry (FAB CID-MS/MS) of five phenolic spiroadamantyl-substituted dioxetanes in the negative-ion mode clearly showed that a highly efficient cleavage of the dioxetane rings took place to produce the corresponding phenolate ion almost exclusively. The mass spectrometric behavior of these compounds reflects the highly efficient intramolecular electron-transfer-induced cleavage of dioxetane rings, which participates in the highly efficient base-triggered chemiluminescent reactions of these compounds in solution.
Gas-Phase Ion—molecule Reactions of C60 with the Plasma of Methyl Acrylate
Authors: Liu Ziyang , Guo Tan , Guo Xinghua , Liu Shuying , Przybylski Michael , Ma Li
Published: December 2007

The gas-phase ion–molecule reactions of C60 with the plasma generated from methyl acrylate under self-chemical ionization conditions were studied by use of a triple-quadrupole mass spectrometer. The adduct cation [C60C3H3O]+ and protonated molecular ion [C60H]+ were observed as the major product ions. The former adduct ion is formed by electrophilic reaction of C60 with the ion [CH2=CHCO]+, a main fragment ion resulting from the methyl acrylate molecular ion [CH2=CHCOOCH3]+ through alpha cleavage. The latter ion is generated by proton transfer from protonated methyl acrylate to C60. Semi-empirical quantum chemical calculations have been performed for the eight possible isomers of [C60C3H3O]+ at the Hartree–Fock level by use of the AM1 method. The results show three types of cycloadducts as the most stable structures among the possible isomers.
Studies of Complex Formation between Anthraquinones and Metal Ions by Electrospray Ionization Mass Spectrometry
Authors: Arakawa Ryuichi , Sasao Ai , Abura Tsutomu , Suzuki Takeshi , Fujitake Nobuhide
Published: December 2007

The metal complexation of the hydroxyanthraquinones, chrysotalunin, chrysophanol and their derivatives, with Al3+, Ni2+ and Zn2+ was studied by electrospray ionization mass spectrometry (ESI-MS). The results showed that chrysophanol and its derivatives form metal complexes with Al3+, Ni2+ and Zn2+ ions, but chrysotalunin does not. Among the metal ions, Al3+ was found to form the complexes most easily.
Structural Investigations of 5-Methylchromone Glycosides from Aloe Species by Liquid Chromatography/Electrospray Tandem Mass Spectrometry
Authors: Schmidt Jürgen , Blitzke Torsten , Masaoud Mohamed
Published: December 2007

The mass spectral behavior of a series of 5-methylchromone glycosides isolated from two Aloe species was investigated by liquid chromatography/positive-ion electrospray (ES) mass spectrometry using collision-induced dissociation (CID) mass spectrometry. The CID mass spectra of the [M + H]+ ions show a typical fragmentation pattern reflecting the several substructures (substitution at C-7, C-9 and C-10, position and nature of the ester moiety at C-2) of the 5-methylchromone glycosides. Besides a series of known 5-methylchromone glycosides, nine new compounds of this type were identified by LC/ES-CIDMS from Aloe rubroviolacea and Aloe perryi (Aloeaceae).
Mass Spectrometric Identification of Novel Polychlorinated Phenyl Salicylates in Sediments of a River Contaminated by Industrial Wastes
Authors: Sinkkonen Seija , Lahtiperä Mirja , Paasivirta Jaakko , Takhistov Viatcheslav V. , Viktorovskii Igor V.
Published: December 2007

Analyses of chlorinated aromatic contaminants in industrially polluted sediments of the Kymijoki River, South-East Finland, were extended to the search of previously unknown pollutants by gas chromatography/mass spectrometry. In the fraction of persistent organochlorines, a series of substances were identified as octa- to tetra-chlorinated phenyl esters of 2-hydroxybenzoic acids (most probably all polychlorinated phenyl salicylates). All their mass spectra were previously unknown and interpreted by fragmentation rules, appearance energy calculations and simulation.
Electron Impact-Induced Fragmentation of the Sesquiterpene Germacrene D
Authors: Steliopoulos Panagiotis , Mosandl Armin
Published: December 2007

The sesquiterpene germacrene D and two deuterium-labeled isotopomers were analyzed by enantio-multidimensional gas chromatography with tandem mass spectrometry in order to investigate mass spectral fragmentation mechanisms. The deuterated analogues were derived from in vivo feeding experiments with 1-[5,5-D2]deoxy-D-xylulose-5-phosphate using intact plant material of Solidago canadensis and were formed by biosynthesis via the methylerythritol phosphate pathway.
The New Generation of Resonant Laser Ionization Mass Spectrometers: Becoming Competitive for Selective Atomic Ultra-Trace Determination?
Authors: Wendt Klaus D.A.
Published: December 2007

A critical assessment of the present status of resonant laser ionization mass spectrometry (RIMS) as a specialized analytical technique for the field of atomic ultra-trace determination is attempted and a comparison with established mass spectrometric methods is made. Within the last years RIMS on atomic species has rapidly developed towards becoming a versatile experimental technique, in particular addressing those applications that require high selectivity in respect of isobaric or isotopic interferences. This progress is mainly based on the advent of easy-to-handle tunable solid-state laser systems for both pulsed and continuous operation, which are used in combination with modern compact mass spectrometers. The general basics, analytical potential and the wide range of applicability of these modern RIMS instruments are outlined and investigations on stable and radioactive ultra-trace isotopes are discussed as illustrative examples. These examples concern a variety of analytical applications in alkali, alkaline earth or noble gas elements as well as in lanthanides, actinides and technetium, covering fields of fundamental as well as applied research in environmental protection, geology and geochronology, biomedical and life sciences.
Rapid Estimation of the Composition of Animal Manure Compost by near Infrared Reflectance Spectroscopy
Authors: Huang Guangqun , Han Lujia , Liu Xian
Published: December 2007

Composting of animal manure is an effective method of managing organic waste in agriculture and reducing environmental and human health risks. Rapid determination of composition of animal manure compost could facilitate the composting process and improve the quality of compost products. This study aimed to explore the feasibility of analysing the composition of animal manure compost based on a dried and fresh weight basis using near infrared (NIR) reflectance spectroscopy. A total of 120 animal manure compost samples, collected from 22 provinces in China, were scanned (4000–10,000 cm−1) and NIR calibrations were developed by partial least-square regression. Results showed that for dried and milled animal manure compost samples, the NIR method could accurately predict the contents of volatile solid (VS), total organic carbon (TOC) and total nitrogen (TN). The validation coefficient of determination ( r 2) and the ratio of the standard deviation of the reference data in the validation set to the standard error of prediction ( RPD) were 0.85 (2.60), 0.85 (2.56) and 0.97 (6.95), respectively. For fresh animal manure compost samples, the NIR method could provide accurate predictions of moisture, electriconic conductivity, VS, TOC and TN content with r2 and RPD of 0.98 (7.48), 0.90 (3.10), 0.94 (4.05) 0.91 (3.17), and 0.97 (6.11), respectively. Poorer calibrations were obtained for pH, carbon to nitrogen ratio and total phosphorus using either dry or fresh samples. Overall, the results indicated that NIR analysis could be very useful for the rapid quality evaluation of animal manure compost.
Capabilities of near Infrared Spectroscopy for the Determination of Petroleum Macromolecule Content in Aromatic Solutions
Authors: Balabin Roman M. , Safieva Ravilya Z.
Published: December 2007

In this paper the application of near infrared (NIR) spectroscopy for the determination of petroleum macromolecules content in model systems is reported. Eighty (80) solutions of three main types of oil macromolecules (asphaltenes, resins, and paraffins) in toluene were studied. NIR spectra within the range 8,000–14,000 cm−1 were used to construct calibration models using the partial least squares method. The low prediction error of the models (0.43, 0.79 and 0.39% w/w for asphaltenes, resins and paraffins, respectively) indicate that NIR spectroscopy can be applied to analyse the petroleum macromolecule content in natural systems (crude oil and its refined products).
Visible/Near Infrared Hyperspectral Imaging via Spatial Illumination Source Modulation
Authors: Streeter L. , Burling-Claridge G.R. , Cree M.J. , Künnemeyer R.
Published: December 2007

A spatially-modulated light encoding system for hyperspectral imaging is presented. A digital micromirror array was used for the optical switching in an illumination system that otherwise resembled a traditional slide projector. The Hadamard encoding scheme was employed in a purely spatial, non wavelength dispersive manner. A single point linear diode array spectrometer measured the spectral dimension. To demonstrate the principle two simple samples were imaged.