Dissertations / Theses on the topic 'Gas-Phase Ion/Ion Reactions'
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1
Wilson, Paul Francis. "Experimental studies of gas-phase ion-molecule reactions." Thesis, University of Canterbury. Department of Science, 1994. http://hdl.handle.net/10092/8318.
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Development on both selected ion flow tube (SIFT) and ion cyclotron resonance (ICR) instruments is described.
Modifications to the SIFT described here include; a new, off-axis ion source, and new hardware and programs to measure the neutral flow and the ion count using a personal computer.
Mechanical, electrical, electronic, and programming modifications to the ICR instrument are described. Several well known ion-molecule reactions are used to calibrate, and monitor the performance of the ICR instrument.
The reactions of t-C₄H₉Cl with a number of protonated bases, BH⁺, are reported. The reactions were studied using both the SIFT and the ICR. The branching ratio of the product channels is reported for each reaction. For some bases, the process,
BH⁺ + t-C₄H₉Cl →’ t- C₄H₉⁺ + B + HCl
appears to be fast, although it is significantly endothermic. The thermochemistry of the system is discussed, and it is suggested that either the tabulated thermochemical values are significantly wrong, or the reaction proceeds via formation of weakly bound complexes which dissociate on focussing in the down stream region of the SIFT.
The chemistry of several srtuctural isomers of protonated ethyl cyanide, C₃H₆N⁺ is examined. Two reactions thought to be routes to interstellar synthesis of ethyl cyanide are shown to be unlikely to yield that ion upon dissociative recombination. The association of HCNH⁺ with C₂H₄ is shown to lead to the protonated ethyl isocyanide isomer. The association of CH₃#x207A; with CH₃CN is reasoned to lead to formation of the CH₃CNCH₃#x207A; structure.
The isomerism observed is rationalised in terms of the potential surface for the system derived from both experimental observation, and several previous ab initio studies.
The reactivity of the methoxymethyl cation with several oxygen and nitrogen bases is reported. The exothermic proton transfer channel is not observed, but competing methyl cation and CH⁺ transfer dominate.
The reactivity in both the SIFT and the ICR is explained in terms of several factors. An activation barrier to proton transfer proceeds from ring closure to form the neutral product, oxirane. The SN2 methyl cation transfer process is sterically hindered and results proceeds via a tight transition state, whereas the alkyl transfer process has a greater density of states at the transition state. Where there is a labile hydrogen on the base, the alkyl transfer process dominates because of its' looser transition state.
The association reactions of acrylonitrile are reported in both the ICR and SIFT instruments. The reaction of CH₂CHCN⁺ shows competition between proton transfer and association. Proton transfer dominates in the ICR and association dominates in the SIFT. The termolecular rate of formation of the proton bound dimer of acrylonitrile is measured at 1.2 x 10⁻²³cm¶ s⁻±.
An RRKM study of the association of CH₃⁺and acetonitrile is reported. The collisional parameters of both helium and acetonitrile bath gases are estimated. The average downward energy transferred per collision, ‹ΔΕdown›, for helium is estimated as 300 cm-⁻±, and for acetonitrile as 950 cm-⁻±. The fall off of the association reaction with pressure is shown in comparison with experimental results.
The ion-molecule reactions of acetylene have been studied, and the results confirm earlier work. The ions C₆H₅⁺, and C₆H₄⁺ are shown to exist as a mixture of two or more isomers of differing reactivity. One isomer reacts with unsaturated hydrocarbons at the collision rate while the other is unreactive. C₆H₄⁺ exists as a mixture of isomers when formed from sequential ion-molecule reactions of acetylene or electron impact or chemical ionisation on halobenzenes. C₆H₄⁺ exists as a mixture of two isomers when formed from sequential ion-molecule reactions of acetylene.
2
Ross, Charles William. "Gas phase ion - molecule reactions studied by Fourier transform ion cyclotron resonance mass spectrometry /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487846885778077.
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Yin, Winnie Weixin. "Fourier transform ion cyclotron resonance mass spectrometric study of gas-phase ion-molecule reactions /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487847309051562.
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Parry, A. J. "Studies of ions and ion-molecule reactions in the gas phase using mass spectrometry." Thesis, Swansea University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638416.
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Ion-molecule equilibrium and kinetic studies in the gas phase have been performed using pulsed high pressure source mass spectrometry, the home-built source being coupled to an updated MS9 mass spectrometer. Bimolecular proton transfer equilibria involving benzene, ethanol, methanol and acetaldehyde were investigated as a function of temperature and values of ΔH and ΔS were derived. An attempt was made to find evidence for high entropies of protonation and hence a 'dynamic' protonated benzene structure. No such evidence was found. Apparently high entropies involving ethanol, were explained in terms of thermal neutral decomposition. The ionic decomposition rate for protonated ethanol was measured as being close to zero, although measurable rates of decomposition were observed for some protonated halotoluenes. Chloride transfer equilibria were also investigated although far less successfully. Problems with the present inlet system led to inconsistent results, possible resolution of these problems, via inlet redesign, is suggested. The mechanism of proton transfer between CH5+ and fluoro and chlorobenzene at low temperatures was successfully identified using B/E linked scanning and was shown to occur via proton-bound complex formation, although the mechanism was too complex to allow extraction of the rates of individual steps from the experimental data. The proton affinity of the Cℓ atom in chlorobenzene was subsequently bracketed between those of water and methanol. The potential energy surfaces of a number of protonated aromatic species C_6H_5XH^+ , were probed using Mass-analysed Ion Kinetic Energy Spectroscopy (MIKES). All were found to be roughly similar, with the exception of F substituted species, these had a barrier to ring-substituent proton migration which exceeded the minimum dissociation threshold for HF loss, resulting in the HF loss peak in the MIKE spectrum being composite. The kinetic energy release associated with HX loss in these species was observed as having a direct correlation with charge distribution in the substituent protonated molecule. An appendix describes extensive semi-empirical molecular orbital calculations as species encountered in this work.
5
Van, Orden Steven Lee. "Mechanistic investigations of gas phase ion-molecule reactions using Fourier transform ion cyclotron resonance mass spectrometry." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186137.
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Studies of the mechanisms and energetics of a variety ion-molecule reactions involving organometallic and organic ions, have been performed using Fourier transform ion cyclotron resonance mass spectrometry (FTMS). The bond activation processes of V⁺, VO⁺, VOH⁺, and VOCH₃⁺ with water and methanol were investigated in detail. All ions are observed to preferentially activate the C-O bond in methanol, however C-H and O-H bond cleavage are also observed. The addition of the oxo, hydroxo, and methoxo ligands is found to significantly effect the intrinsic reactivity of the ions, relative to V⁺. The reactions of V(CO)₅⁻ with a wide variety of molecules have revealed mechanistic details of the oxidative addition and ligand switching reactions. Steric effects are proposed to account for the selective reactivity of V(CO)₅⁻ with alcohols and amines. Studies of ligand substitution reactions support an electron transfer initiated mechanism, implying that V(CO)₅⁻ has a triplet ground state and a trigonal bipyramidal structure. The chlorine atom transfer reactions of V(CO)₅⁻ with chloromethanes display a correlation with C-CI bond strength, suggesting the mechanism is initiated by oxidative addition of the C-C1 bond or involves a direct chlorine atom transfer. The decomposition of metallocarboxylate anions ([M(CO)ₓ₋₁CO₂]⁻) was studied in an effort to understand the production of CO₂ by metal carbonyl compounds, proposed as intermediates in the Water-Gas shift reaction. The nascent [M(CO)ₓ₋₁C0₂]⁻*, formed by nucleophilic addition of 0⁻ to M(CO)ₓ (M=Pe, Cr, V), is observed to undergo exclusive loss of CO₂ without subsequent decomposition of the product metal carbonyl anion (M(CO)ₓ₋₁⁻) The reaction of P AHs with O⁻ and O₂⁻ were studied, to investigate the potential of isomer differentiation by chemical ionization. These reactions are characterized by a number of reactive pathways, demonstrating the ability to distinguish isomers which cannot be differentiated by other ionization techniques. Kinetic energy release measurements of the S(N)2 reactions of F⁻ with CH3CI, C₆H₅CI, and CH₃COCl have been made using KEICR. The F⁻/CH₃Cl reaction results in a non-statistical energy disposal. The reaction is proposed to proceed by a direct mechanism.
6
Parker, Mariah L. "The Investigation of Oxidative Addition Reactions of Metal Complexes in Cross-Coupling Catalytic Cycles Based on a Unique Methodology of Coupled Ion/Ion-Ion/Molecule Reactions." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5651.
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Popular catalytic cycles, such as the Heck, Suzuki, and Negishi, utilize metal centers that oscillate between two oxidation states (II/0) during the three main steps of catalysis: reductive elimination, oxidative addition, and transmetallation. There has been a push to use less toxic, cheaper metal centers in catalytic cycles, leading to interest in first-row transition metals, such as nickel and cobalt. With these metals, the cycles can potentially pass through the +1 oxidation state, which acts as reactive intermediates, undergoing oxidative additions to form products, potentially with radical characteristics. The oxidative addition steps of catalytic cycles are critical to determining overall rates and products, however in many cases, these steps have not been amenable to study, in either condensed phase or gas phase, in the past. Through the use of electron transfer dissociation (ETD) technology on a modified Thermo Electron LTQ XLTM mass spectrometer, it is possible to generate intermediates in these catalytic cycles, including those in unusual oxidation states. Using sequentially coupled ion/ion-ion/molecule reactions, the reduced, reactive intermediate can be readily generated, isolated, and studied.As a model set of reactions, the mono- and bis-phenanthroline complexes of Fe(I), Co(I), Ni(I), Cu(I), and Zn(I) were formed by reduction of the corresponding M(II) species in an ion/ion reaction with the fluoranthenyl radical anion. The chemistry of the M(I) species was probed in ion/molecule reactions with allyl iodide. In order to explore ligand effects and the scope of oxidative addition reagents further, bipyridine and terpyridine were studied with these five first-row transition metal complexes while using an acetate series and other substrates for oxidative additions. Through these studies, the roles of the metal and ligand in dictating the product distributions and reaction rates were assessed. Metal electron count, ligand flexibility, and coordination number are critical factors. The overall reactivity is in accord with density functional theory calculations and mirrors that of proposed intermediates in condensed-phase catalytic cycles. In addition, second- and third-row transition metals (Ru(I), Pd(I), and Pt(I)) were explored with bipyridine, mono- and bis-triphenylphosphine, and 1,2-bis(diphenylphosphino)benzene ligation schemes. A variety of oxidative addition reagents were surveyed to determine the scope of reactivity and preference toward metal-carbon bond formation or carbon radical formation.
7
Mahdi, A. M. "A mass spectrometric study of translational energy release in the reactions of gas phase cations." Thesis, University of Essex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379376.
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8
Beelen, Eric Stephan Edmond van. "Proton transfer and ligand exchange induced reactions in the gas phase." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2005. http://dare.uva.nl/document/18421.
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9
Zhong, Meili. "Kinetics, potential energy surfaces, and structure-reactivity relationships of gas phase ion molecule reactions. /." May be available electronically:, 1997. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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10
Hall, Robin Gibson. "The development of a quinquaquadrupole mass spectrometer : the study of ion-molecule reactions in the gas phase using multiple quadrupole instruments." Thesis, University of St Andrews, 1991. http://hdl.handle.net/10023/15506.
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The field of quadrupole mass spectrometry has grown enormously since the early 1980's. The invention of the triple quadrupole mass spectrometer led to the development of tandem quadrupole mass spectrometers of many different configurations. A large number of tandem quadrupole mass spectrometers have also been developed by linking one or more quadrupole mass filters to a traditional magnetic or electric filter. The versatility of multiple quadrupole mass spectrometers along with their potential to rapidly produce a huge amount of data on a particular ion makes them ideal instruments for routine analytical analysis as well as for fundamental research The quinquaquadrupole mass spectrometer has been developed as an extension to the available multiple quadrupole systems. It offers the possibility to obtain even more data on the fragmentation of ions as well as enabling the study of novel ions to be carried out. The development of the quinquaquadrupole mass spectrometer forms the main part of this thesis. Also discussed are the reactions studied to evaluate the instrumental performance. The the ion molecule reactions of some halogen containing cations with saturated and unsaturated hydrocarbons performed on the triple quadrupole mass spectrometer are also discussed.
11
Petrie, Simon Antony Hudson. "A selected-ion flow tube study of some gas-phase ion-molecule reactions of potential relevance to the chemistry of dense interstellar clouds." Thesis, University of Canterbury. Chemistry, 1991. http://hdl.handle.net/10092/7253.
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Results are reported for the studies of several systems of ion-molecule reactions of potential relevance to the chemistry of interstellar clouds. Measurements were obtained using a selected-ion flow tube operated at room temperature (300 ± 5 K) and using helium buffer gas at a pressure of 0.30 ± 0.01 Torr.
The proton affinities of C₄H₂ and C₂N₂ were determined by measurement of the rate coefficients for forward and reverse proton transfer reactions involving compounds of similar proton affinity. The results obtained were P A(C₂N₂) = 674 ± 4 kJ mol-¹ and PA(C₄H₂) = 741 ± 4 kJ mol-¹: this latter quantity is significantly below the literature value, based on an earlier measurement obtained from ICR bracketing.
Isomerism of the ions C₂N⁺, C₃N⁺, CHN⁺ and CH₂N⁺ was investigated, using reactivity with various neutrals to distinguish between isomers. The ions CCN⁺/CNC⁺ and CCCN⁺/c-C₃N⁺ were distinguished on the basis of their reactivity with H₂: in both instances, the isomer featuring a terminal N atom reacted rapidly while the other isomer was unreactive. Identification of the isomers HCN⁺/HNC⁺ was complicated by the occurrence of tautomerisation of HCN⁺ to the more stable isomer HNC⁺ by the mechanism of 'forth and back' proton transfer which occurred with several neutral reagents: reaction with CF₄ was subsequently used to distinguish between these isomers, since HCN⁺ reacted rapidly with CF₄ while HNC⁺ was unreactive. The reactions of all of these isomeric systems were examined with several neutrals abundant in interstellar clouds. The ions HCNH⁺ and CNH₂⁺ could not be distinguished on the basis of reactivity with the neutrals surveyed: we cannot exclude the possibility that only one of these isomers, HCNH⁺, was formed using the ion producing methods used.
The reactivity of several ions C₃HnN⁺ (n = 1 → 4) and C₃HnO⁺ (n = 0 → 3), with various neutrals, was investigated to ascertain the importance of these ions in the interstellar synthesis of acrylonitrile, tricarbon monoxide and propynal. Several ion-molecule reactions of CH₂CHCN were also studied to this end. The results indicate that C₃HnN⁺ (n > 0) and C₃HnO⁺ (n > 0) are unreactive with the most prominent cloud constituents H₂ and CO; thus dissociative recombination of these ions should represent a significant source of the target molecules. Several ion-molecule reactions of the types X⁺ + CH₂HCN, and C₃nN⁺ + X, produce ions which, on dissociative recombination, are expected to yield cyanopolyynes and cyclopropenylidene. Several reactions of the C₃HnO+ ions suggest pathways to higher-order polycarbon monoxides and dioxides.
The reactivity of the molecular ions of C₂N₂, C₄N₂ and C₃0₂ have also been studied, to gauge the likely consequences of reactions of such ions within interstellar clouds.
The thermochemistry of the reaction HCN⁺ + CF4₄ → CF₃⁺ + HF + CN is explored with regard to the proposal that this reaction may be 'entropy-driven'.
The interstellar significance of a novel class of neutral-neutral reactions has been considered.
The reactivity of the ions C₄Hn⁺ (n = 0 → 4), C₃HnN⁺ (n = 0 → 4), and C₃HnO⁺ (n = 0 → 3) with the neutrals H₂, CO, C₂H₂ and HCN is discussed in greater detail.
Previous studies have determined that ions featuring linear carbon-chain skeletons are more reactive with H₂ and with CO if they feature 'bare' (non-hydrogenated) terminal carbon atoms: the present study suggests that ions with bare terminal C atoms are also more reactive than ions where the terminal atom is N or 0 rather than C. This observation may be explained by the degree of carbene character evident in such ions. These results are also discussed with reference to the predominance of very highly unsaturated linear molecules within interstellar clouds.
12
Hayes, Roger Nicholas. "A study of some gas phase nucleophilic substitution reactions of carbon, silicon and boron by ion cyclotron resonance mass spectrometry /." Title page, table of contents and summary only, 1985. http://web4.library.adelaide.edu.au/theses/09PH/09phH418.pdf.
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Svilar, Ljubica. "Structural elucidation of secondary metabolites from Hypoxylon fragiforme, using high resolution mass spectrometry and gas-phase ion-molecule reactions." Paris 6, 2012. http://www.theses.fr/2012PA066468.
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Fungi produce a wide variety of biologically active compounds/metabolites that could be used for medicinal and pharmaceutical purposes. Mitorubrines, members of the family of azaphilones, constitute a particularly interesting set of structurally diverse secondary metabolites, exhibiting a wide range of biological activities (e. G. Antimicrobial, antibacterial, antimalarial). This work describes the development of several mass spectrometry-based approaches to solve the natural structural diversity and complexity of azaphilones extracted from Hypoxylon fragiforme fungus. The first part of this manuscript is dedicated to the development and validation of an analytical methodology involving liquid chromatography coupled to high resolution mass spectrometry for the efficient and accurate detection of trace-level azaphilones in complex fungal extracts. Further collision-induced dissociation and hydrogen/deuterium exchange experiments were performed to fully elucidate and characterize the azaphilones and their nitrogenized analogues from Hypoxylon fragiforme. The second part is devoted to the application of these different analytical strategies to the in-depth characterization of a novel family of secondary metabolites derived from azaphilones, the mitorubramines. Lastly, these different secondary metabolites were further purified to confirm their chemical structures by NMR spectroscopyLes champignons produisent une grande variété de composés/métabolites biologiquement actifs qui peuvent être utilisés à des fins médicinales et pharmaceutiques. Les mitorubrines, membres de la famille des azaphilones, constituent un ensemble particulièrement intéressant de métabolites secondaires, présentant une grande étendue d’activités biologiques (e. G. Antimicrobienne, antibactérienne, antipaludique). Ce travail présente le développement de plusieurs approches de spectrométrie de masse permettant de résoudre la diversité structurelle naturelle et la complexité des azaphilones extraits des champignons Hypoxylon fragiforme. La première partie de ce manuscrit est dédiée au développement et à la validation d’une méthodologie analytique impliquant la chromatographie liquide couplée à la spectrométrie de masse haute résolution pour la détection efficace et précise de traces d’azaphilones dans des extraits fongiques complexes. En outre, des expériences de spectrométrie de masse en mode tandem (par dissociation induite par collision, CID) et d'échange hydrogène/deutérium ont été effectuées pour élucider et caractériser les azaphilones et leurs analogues azotés chez Hypoxylon fragiforme. La deuxième partie est consacrée à l'application de ces différentes stratégies analytiques pour la caractérisation approfondie d'une nouvelle famille de métabolites secondaires dérivés des azaphilones, les mitorubramines. Enfin, ces différents métabolites secondaires ont été purifiés pour confirmer leur structure chimique par spectroscopie RMN
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Betts, Nicholas B. "Laboratory studies of gas phase ion-neutral reaction rate constants relevant to the interstellar medium." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1439438.
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Santos, Ivan. "Quantification of gas-phase ion-molecule reactions of complex organic compounds and a study of the factors involved in these determinations by Fourier transform ion cyclotron resonance mass spectrometry /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487335992902583.
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Lopes, Allan. "Réactions ion-molécule en phase gaz pour la chimie des ionosphères planétaires et des plasmas." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS577/document.
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La thèse porte sur des études expérimentales de réactions d’ions positifs et négatifs pour lesquelles on cherche à caractériser l’effet des différentes formes d’énergie : excitation des ions parents et/ou énergie de collision sur la réactivité. Deux buts sont poursuivis. Le premier, fondamental, est de comprendre la dynamique réactionnelle des systèmes étudiés. Le deuxième est plus appliqué. Il s’agit de fournir des données pour la modélisation de la chimie des milieux complexes (ionosphères, plasmas…). Les systèmes étudiés concernent la réactivité de cations excités CH₃⁺ avec des hydrocarbures saturés et insaturés (alc-ane, -ènes et -ynes en C1 à C4) pour sonder la réactivité sur des molécules de fonctionnalité et de tailles variées ainsi que la réactivité de l’anion C₃N⁻ avec l’acétylène C₂H₂. Ces systèmes sont d’intérêt pour l’étude de l’ionosphère de Titan. Nous avons étudié la réactivité de ces systèmes sur le dispositif CERISES en fonction de l’énergie de collision et de l’énergie interne des ions parents. Les anions C₃N⁻ sont produits par attachement dissociatif d’électrons sur le précurseur BrC₃N. Les cations CH₃⁺ peuvent être formés par deux méthodes. Au laboratoire, l’impact électronique conduit, sur le méthane CH₄, à la formation de CH₃⁺ peu excité, et sur le chlorométhane CH₃Cl, à la formation de CH₃⁺ plus excité. Cette observation a permis de préparer les expériences au synchrotron SOLEIL où on utilise la photoionisation des radicaux CH₃ produits par la pyrolyse du nitrométhane CH₃NO₂ pour former les ions CH₃⁺ et contrôler leur excitation. La variation de l’énergie de photon entre 9.8 et 15 eV a permis de faire varier la distribution d’énergie vibrationnelle ou électronique des ions CH₃⁺. Le développement d’un détecteur de photoélectrons adapté à la source de radicaux a permis la réalisation d’expériences TPEPICO (Threshold PhotoElectron PhotoIon Coincidence) où les ions sont extraits de la source en coïncidence avec des électrons de seuil permettant ainsi un contrôle complet de leur énergie. Nous avons observé que l’énergie interne de CH₃⁺ peut jouer un rôle important sur sa réactivité en ouvrant certaines voies de réaction comme la dissociation séquentielle de certains produits (réactions avec le méthane, le propène…) ou bien la voie de transfert de charge endothermique (réactions avec le méthane, l’éthène) que l’énergie de collision ne favorise pas efficacement. L’observation de l’évolution de la section efficace de formation des produits en fonction des deux types d’énergie nous a également permis de discuter les mécanismes de formation de certains produits, comme ceux passant par la décomposition d’un complexe ou par des transferts plus directs. On a pu montrer que la réaction de C₃N⁻ + C₂H₂ produisait des ions C₂H⁻, CN⁻ et C₅N⁻ en faibles quantités et seulement au-dessus de seuils en énergie de collision qui excluent leur formation dans des atmosphères très froides comme celle de Titan, sauf s’il existe des processus formant les anions C₃N⁻ avec de l’énergieThis PhD project is focused on the experimental study of reactions of positive and negative ions for which we want to characterize the effect of different energies: internal energy of parents ions and/or collisional energy on the reactivity. There are two main goals. The first is to understand the reaction dynamics of the studied systems. The second one is to obtain data for modelisation of the chemistry in complex areas (ionosphere, plasmas...). Studied systems will concern the reactivity of excited cations CH₃⁺ with saturated and unsaturated hydrocarbons (alcane, alcene and alcyne from C1 to C4) as well as the reactivity of the C₃N⁻ anion with acetylene C₂H₂. Targets are chosen for theirs different chemical functions and interesting size for theoretical studies of Titan. We have studied the reactivity of these systems on the CERISES setup as a function of internal and collisional energies of the parent ions. C₃N⁻ anions are produced by dissociative electron attachment on BrC₃N. CH₃⁺ cations can be produced by two different methods. At the LCP, electronic impact on methane CH₄ produce CH₃⁺ cations with low internal energy whereas electronic impact on chloromethane CH₃Cl produce CH₃⁺ cations with more internal energy. This observation allowed us to prepare for the experiments at the SOLEIL synchrotron where CH₃⁺ cations are produced with controlled internal energy by photoionisation of CH₃ radicals produced in-situ by pyrolysis of nitromethane CH₃NO₂. Tuning of the photon energy between 9.8 and 15 eV allowed us to change the vibrational or electronic energy distribution of the CH₃⁺ cations. The development of a photoelectron detector fitted to the radical source enabled TPEPICO experiments (Threshold PhotoElectron PhotoIon Coincidence) where ions are extracted from the source in coincidence with threshold electrons which allow a total control of their energy.We saw that the internal energy of CH₃⁺ can have an important role on its reactivity by opening paths of reaction like sequential dissociation of products (seen in reactions with methane, propene…) or endothermic charge transfer (with methane and ethene) which is not efficiently enhanced by collisional energy. From the evolution of the absolute reaction cross section with the two different energies we discussed the mechanisms of formation of the observed products (decomposition of a complex or direct transfer). The reaction C₃N⁻ + C₂H₂ produce C₂H⁻, CN⁻ and C₅N⁻ anions in small quantities and only above collisional energy threshold which exclude their formation in cold atmosphere like Titan’s one unless there is processes leading to the production of C₃N⁻ with energy
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Yahia, Marei Abdelrahim Mohamed. "Bio(molecular) control of selective ion transport, gas separation and catalytic enzyme-based reactions using functionalized membranes." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS251/document.
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Différents travaux de recherche ont été décrits dans cette thèse. Les travaux de recherche peuvent être résumés comme suit. Le premier chapitre a porté sur l'identification d’inhibiteurs puissants efficaces vis-à-vis de de l'isoenzyme anhydrase carbonique humaine I (hCAI). Considérant l'importance pharmacologique de trouver des inhibiteurs (CAIs) et des activateurs (AACs) sélectifs aux isoformes de l’anhydrase carbonique ), l'anhydrase carbonique humaine I (hCAI) a été confrontée en parallèle à diverses bibliothèques dynamiques constitutionnelles (CDL). Dans le deuxième chapitre, des réseaux constitutionnels dynamiques ont été préparés sous forme de systèmes membranaires liquides et solides agissant comme un réseau pour le transport spécifique des ions lanthanides. Le transport est basé sur la capacité de complexation des lanthanides (La + 3, Lu + 3, Eu + 3) avec les groupes polyéther fonctionnels situés dans les matériaux membranaires. Dans le troisième chapitre, l'approche proposée consiste en l'utilisation de membranes liquides ioniques supportées (SILMs) comprenant deux enzymes différentes de l'anhydrase carbonique, l’enzyme thermo-résistante SspCA et l'enzyme bovine-CA, qui catalysent la réaction de conversion réversible du CO2 en bicarbonate en favorisant la force motrice vers le transport de CO2. La stabilité des membrane, leur perméabilité vis-à-vis de CO2 et de N2 ainsi que la sélectivité idéale (CO2 / N2) ont été déterminées pour les membranes développées. Le quatrième chapitre porte sur la synthèse et la caractérisation de membranes polymères denses pour une application en séparation de gaz. Les mesures de perméabilité aux gaz des membranes polymères synthétisées ont montré que la perméabilité de CO2 est supérieure à celle des autres gaz testés (CH4 et N2). Dans le dernier chapitre, des membranes de PVDF ont été fonctionnalisées avec une enzyme, la phosphotriestérase (PTE), selon deux méthodes différentes pour construire un réacteur à membrane biocatalytique (BMR) avec pour finalité la bioconversion et la séparation sélective du substrat paraoxon. La première méthode met en œuvre une dispersion réversible de nanoparticules magnétiques de PTE qui est immobilisée à la surface de la membrane de PVDF sous l’effet d'un champ magnétique externe. A l’inverse, la seconde méthode porte sur le greffage chimique de l'enzyme PTE, après modification de la surface de la membrane de PVDF native (DAMP-GA-enzymatique). Les deux techniques d'immobilisation d'enzymes ont montré une bonne efficacité et une sensibilité à l'égard de la bioconversion du paraoxon dans les différentes conditions appliquées dans un réacteur à membrane biocatalytique (BMR).De façon globale, les concepts développés dans ce travail de thèse permettront d’ouvrir de nouvelles pistes de recherche allant vers le développement d'une membrane polymère sélective au transport d’ions, de gaz mais aussi active dans les réactions catalytiques enzymatiques grâce à un contrôle bio-moléculaire au niveau des matériaux membranairesDifferent research works have been described in this thesis. The research works can be summarized as the following. The first chapter deals with the identification of effective potent inhibitors for the human carbonic anhydrase I (hCAI) isozyme. Considering the pharmacological importance to find selective CA inhibitors (CAIs) and CA activators (CAAs), human carbonic anhydrase I (hCAI) has been subjected to a parallel screening of various constitutional dynamic libraries (CDL). In the second chapter, constitutional dynamic networks have been used in liquid and solid membrane systems as a carrier network for transporting lanthanides. The transport is based on the complexing ability of lanthanides metals (La+3, Lu+3, and Eu+3) with the functional polyether groups in the membrane materials. In the third chapter, the proposed approach consists in using supported ionic liquid membranes (SILMs) comprising two different carbonic anhydrase enzymes, the thermo-resistant SspCA enzyme and the Bovine-CA enzyme, which catalyze the reaction of reversible conversion of CO2 to bicarbonate, enhancing the driving force for CO2 transport. Membrane stability, CO2 and N2 permeability and (CO2/N2) ideal selectivity were determined for the membranes developed. In the fourth chapter, the research work consists in the synthesis and characterization of dense polymeric membranes for gas separation application. The gas permeability measurements for the synthesized polymeric membranes showed that the permeability of CO2 is higher than other used gases (N2 and CH4). In the last chapter, two different methods of PVDF membrane functionalization with a phosphotriesterase (PTE) enzyme have been developed to construct biocatalytic membrane reactor (BMR) for bioconversion and selective separation of paraoxon substrate. The first method employs reversible dispersion of magnetic nanoparticle immobilized with PTE using an external magnetic field on the surface of native PVDF membrane. On the contrary, the second method comprises chemical grafting of the PTE enzyme, after surface modification of the native PVDF membrane (DAMP-GA-Enzyme). Both methods of enzyme immobilization showed good efficiency and sensitivity towards the bioconversion of paraoxon substrate at different conditions applied in a biocatalytic membrane reactor (BMR).In general, the concepts developed in this thesis research work will help bring new tracks on the way to the development of a polymeric membrane for selective ion and gas separation but also for selective catalytic reaction under bio(molecular) control
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Aldajaei, Jamal. "Determination of the factors that affect the gas-phase reactivity of metal-centered cyclopropanation catalysts and examination of the properties of their reaction products." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3393.
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Gas phase studies of organometallic systems have provided deep insight into reaction mechanisms and reaction intermediates. In this thesis, several metal/ligand systems were examined in an effort to form metal carbenes in the gas phase. With cobalt and iron porphyrins, the carbene undergoes metal-ligand insertion. With copper bis-oxazolines, metal carbenes tend to undergo metal-ligand insertion and a Wolff rearrangement. To avoid insertions, we turned to a rigid ligand, 1, 10-phenanthroline. Under ESI conditions, a copper (I) complex with phenanthroline can be formed. When treated with diazoacetate esters, the dominant product results from addition with loss of nitrogen followed by loss of CO. This appears to be the result of a Wolff rearrangement of the metal carbene to give a metal ketene complex that spontaneously loses CO. There is no evidence of any stable metal carbenes in this reaction system. Trimethylsilyldiazomethane was also used as a carbene precursor, and its reaction with the copper phenanthroline complex gives addition with loss of nitrogen; but the product exhibits no carbene reactivity with alkenes. Here computational modeling suggests that the metal carbene undergoes a 1, 2 methyl migration, giving an exceptionally stable sila-alkene complex with the copper. As an alternative path to a metal carbene, we have used ESI to form a complex between the copper (I) phenanthroline and betaine (N, N, N-trimethylglycine). Under CID, this complex wills decarboxylates to give a copper ylide complex. Further CID leads to loss of trimethylamine and the formation of a complex between methylene and the copper phenanthroline. Depending on the CID conditions, two isobaric products are formed. One exhibits no carbene reactivity and the other readily gives carbene behavior with alkenes. The former is likely a metal-ligand insertion product, and the latter is the true metal carbene species. We explored the reactions of the carbene with electron-rich alkenes, such as ethyl vinyl ether and 3, 4-dihydro-2H-pyran, and electron-deficient alkenes, such as trichloroethylene.
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O'Hair, Richard Alfred John. "Studies in gas phase ion chemistry : a thesis presented for the degree of Doctor of Science in the Faculty of Science of the University of Adelaide /." Title page, table of contents and summary only, 2004. http://web4.library.adelaide.edu.au/theses/09SD/09sdo362.pdf.
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Attah, Isaac Kwame. "BINDING ENERGIES AND SOLVATION OF ORGANIC MOLECULAR IONS, REACTIONS OF TRANSITION METAL IONS WITH, AND PLASMA DISCHARGE IONIZATION OF MOLECULAR CLUSTERS." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/525.
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In this dissertation, different approaches have been employed to address the quest of understanding the formation and growth mechanisms of carbon-containing molecular ions with relevance to astrochemistry. Ion mobility mass spectrometry and DFT computations were used to investigate how a second nitrogen in the pyrimidine ring will affect the formation of a covalent bond between the benzene radical cation and the neutral pyrimidine molecule, after it was shown that a stable covalent adduct can be formed between benzene radical cation and the neutral pyridine. Evidence for the formation of a more stable covalent adduct between the benzene radical cation and the pyrimidine is reported here. The effect of substituents on substituted-benzene cations on their solvation by an HCN solvent was also investigated using ion mobility mass spectrometry and DFT computations were also investigated. We looked at the effect of the presence of electron-withdrawing substituents in fluorobenzene, 1,4 di- fluorobenzene, and benzonitrile on their solvation by up to four HCN ligands, and compared it to previous work done to determine the solvation chemistry of benzene and phenylacetylene by HCN. We report here the observed increase in the binding of the HCN molecule to the aromatic ring as the electronegativity of the substituent increased. We also show in this dissertation, DFT calculations that reveal the formation of both hydrogen-bonded and electrostatic isomers, of similar energies for each addition to the ions respectively. The catalytic activity of the 1st and 2nd row TM ions towards the polymerization of acetylene done using the reflectron time of flight mass spectrometry and DFT calculations is also reported in this dissertation. We explain the variation in the observed trend in C-H/C-C activity of these ions. We also report the formation of carbide complexes by Zr+, Nb+, and Mo+, with the acetylene ligands, and show the thermodynamic considerations that influence the formation of these dehydrogenated ion-ligand complexes. Finally, we show in this dissertation, a novel ionization technique that we employed to generate ions that could be relevant to the interstellar and circumstellar media using the reflectron time of flight mass spectrometry.
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Firmino, Thiago Diamond Reis. "Reações de solvólise em fase gasosa do cátion +SiCl3: experimento e teoria." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/46/46132/tde-20072010-201222/.
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Íons polihalogenados de Si, X3Si+ (X = F, Cl), são fragmentos facilmente gerados em espectrometria de massas por ionização eletrônica de compostos de silício polihalogenados. Estes cátions possuem um elevado caráter eletrofílico e desempenham um papel importante como intermediários em processos de corrosão auxiliados por plasma utilizados na fabricação de dispositivos em microeletrônica. Esta dissertação apresenta um estudo sobre a reatividade dos íons +SiCl3, em fase gasosa, perante uma série de substratos neutros simples como água, alcoóis, amônia, aminas e algumas bases doadoras de elétrons π. As reações íon-molécula em fase gasosa foram caracterizadas do ponto de vista experimental por espectrometria de massas de ressonância ciclotrônica de íons por transformada de Fourier (FTICR) a pressões da ordem de 10-8 Torr. As reações foram acompanhadas em função do tempo de reação na cela do espectrômetro, o que permitiu a elucidação de uma série de reações sequenciais. O perfil de energia das reações e as estruturas dos íons silicênios formados nestas reações foram também caracterizados por métodos de química computacional, usando métodos ab initio e métodos baseados na teoria do funcional da densidade, a fim de elucidar o mecanismo das reações. Observou-se que o cátion +SiCl3 reage rapidamente em fase gasosa com os diversos substratos neutros através de processos semelhantes a reações de solvólise que resultam na adição do neutro seguida de eliminação de HCl. Em vários dos casos, foi possível observar a solvólise total do cátion com substituição dos três átomos de cloro. Os cálculos revelam que estas reações se processam inicialmente pela adição do eletrófilo aos centros ricos em densidade eletrônica dos substratos neutros e que estes adutos são mais estáveis que os reagentes isolados. O estado de transição destas reações envolve uma migração 1,3 de um hidrogênio e a energia calculada para o estado de transição é consideravelmente menor que a energia dos reagentes, fato este comum para reações rápidas íon/molécula em fase gasosa. Os cálculos para a espécie correspondente +CCl3 revelam que este tipo de reação não é favorável para os cátions metílicos substituídos e experimentalmente reações semelhantes não são observadas para +CCl3. No caso dos íons ClnSi(OH)3-n+ (n=1, 2 e 3), oriundos das reações de hidrólise do íon +SiCl3, observou-se reações secundárias de condensação com SiCl4 que levam a formação de espécies iônicas com ligações tipo siloxanas (-Si-O-Si-). Os cálculos teóricos sugerem que estas reações se processam inicialmente através de um intermediário tipo clorônio, R1-Cl+-R2 seguida de uma transferência formal de um átomo de Cl e rearranjo para uma estrutura tipo siloxana.Polyhalogenated silicenium ions, X3Si+ (X = F, Cl), are common fragment ions in the mass spectra of polyhalogenated silanes obtained by electron ionization. These ions are powerful electrophiles and are believed to play a role in plasma enhanced corrosion processes and plasma enhanced chemical vapour deposition processes. In this dissertation, we present some new results on the gas-phase reactivity of the +SiCl3 ion with a number of simple n electron donor bases such as water, alcohols, ammonia, amines and some π electron donor bases. Ion-molecule reactions were characterized experimentally by Fourier transform ion cyclotron resonance mass spectrometry (FTICR) at pressures in the 10-8 Torr range. Reactions were followed as a function of trapping time of the ions in the cell of the spectrometer and this allowed for the identification of subsequent reactions of the primary product ions. The energy diagram and structure of the different silicenium ions were also characterized by computational chemistry using both ab initio and density functional theory methods in order to understand the mechanism of these reactions. +SiCl3 reacts rapidly in gas phase with various neutral substrates through processes similar to solvolysis in which the neutral substrate adds onto the silicenium ion followed by elimination of HCl. In some cases, complete solvolysis is observed with substitution of all three chlorine atoms. The calculations show that reactions proceed by initial addition of the electrophile onto the electron center of the neutral substrates giving rise to stable adducts. The transition state for these reactions involve a 1,3 hydrogen migration and the calculated energy for these transition states is less than the energy of the isolated reactants, a fact that is common to fast gas-phase ion-molecule reactions. Similar calculations for +CCl3 reveal similar solvolysis reactions to be energetically unfavourable, and in fact these reactions are not observed experimentally. Secondary reactions have been observed for the product ions ClnSi(OH)3-n+ (n = 1, 2 and 3), obtained from successive hydrolysis of +SiCl3, with the parent SiCl4 neutral. These secondary condensation reactions yield ionic species containing a siloxane type linkage (-Si-O-Si-). The theoretical calculations suggest that is that these secondary condensation reactions initially proceed via chloronium ion intermediate, R1-Cl+-R2 , followed by formal Cl transfer and rearrangement to a siloxane type structure.
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Kingston, R. G. "Charge-permutation reactions of gas-phase ions." Thesis, Swansea University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637801.
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Collisions of high translational energy ions with neutral gas targets (N) may result in an alteration in the number or sign of the charge and the internal energy of the ion undergoing reaction. These gas-phase reactions are referred to as charge-permutation reactions. In this thesis several types of charge-permutation reaction have been studied, to glean information on the energetics of the reaction. In particular, for doubly- and triply-charged ions, by measuring translational energy changes of the ion undergoing reaction and from energy release data when the ion undergoes fragmentation. Fragmentation patterns have provided structural information. Charge-stripping reactions of polycyclic aromatic species, Mn+ + N → M^(n+1)++N+e^- have been used to determine ionization energies. Relationships between, the ionization energies of M^2+ and M^3+ and the appearance energy of M^+ have been investigated, the charge-stripping efficiency of the collision gas, the ionization energy, the ion velocity and ion radius, have been derived. Charge-inversion reactions of NO^- leading to NO^+, O^+ and N^+ have revealed the role of neutral species and methods are demonstrated to separate and categorise the consecutive reaction steps. Some fragment ion peaks, of composite nature, have been deconvoluted to show the contributions of the various reactions. Charge-exchange reactions (electron capture) M^n+ + N → M(n-1)+ + N+have been used to assign the electronic states for a series of polycyclic aromatic compounds, where n = 2 or 3. Internal energy distributions of product ions have been measured utilising known breakdown graphs. Empirical relationships between cross-sections for electron capture and the energy balance for the reaction have been formulated. The only reaction studied which occurs unimolecularly is charge separation. M(p+q)+ → Mp+atop a + Mq+atop b From energy release data, intercharge distances have been calculated for multiply-charged polycyclic aromatic ions and structural information inferred. Charge exchange and charge stripping have been used to detect structural differences between three C_6H_6 isomers.
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GROVER, RENAUD. "Etude des reactions ion/molecule en phase gazeuse des melanges silane/ammoniac et silane/phosphine par spectrometrie de masse ft-icr. Etude comparee a la spectrometrie itms au moyen de plans d'experiences." Nice, 1998. http://www.theses.fr/1998NICE5242.
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L'elaboration de materiaux de composition et de structure definies fait souvent appel a des voies de synthese a partir de precurseurs gazeux. C'est le cas pour le nitrure de silicium si#3n#4, utilise comme couche de passivation destinee a proteger les surfaces sensibles contre les agressions exterieures, ou encore le silicium dope au phosphore et ses proprietes semi-conductrices. Aussi, les reactions ion/molecule qui ont lieu apres ionisation des melanges gazeux constitues de silane et d'ammoniac, d'une part, et de silane et de phosphine, d'autre part, ont ete etudiees au moyen de spectrometres de masse a piegeage d'ions : un spectrometre a resonance cyclotron des ions a transformee de fourier (ft-icr), et un ion trap mass spectrometer (itms). Les informations extraites des donnees spectrales, qui concernent a la fois l'aspect mecanistique et l'aspect cinetique, permettent d'identifier les ions responsables de la formation et de la propagation d'especes contenant des liaisons si-n, d'une part, et si-p, d'autre part. Un plan d'experiences a ete elabore en vue d'identifier methodiquement les parametres susceptibles d'influer sur le resultat d'une mesure cinetique en phase gazeuse. Cette etude a montre l'utilite d'une approche statistique des conditions de mesure, a opposer a l'approche habituelle qui fait intervenir plus d'a priori de la part de l'experimentateur.
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Bissonnette, Martine C. "Ion/radical and ion/molecule complexes and ion structure assignments in the gas phase." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7731.
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The fragmentation mechanism of ionized neopentanol, (CH$\sb3$)$\sb3$CCH$\sb2$OH$\sp{+-}$, has been studied in great detail along with other C$\sb5$H$\sb $H$\sp{+-}$ isomers. The use of $\sp $C and D labelling was found an essential tool to establish the relation between the other species involved in the dissociation of neopentanol. The involvement of (CH$\sb3$)$\sb2$C$\sp{\cdot}$CH$\sb2\sp+$(O)HCH$\sb3$, (CH$\sb3$)$\sb3$C$\sp+$(O)HCH$\sb2$ and (CH$\sb3$)$\sb2$($\sp\cdot$CH$\sb2$)CCH$\sb2\sp+$OH$\sb2$ was essential to explain the H/D label exchange occurring upon fragmentation of neopentyl alcohol. An ion-dipole complex between methanol and ionized methyl propene is proposed as the final intermediate which leads directly to the products, methanol and ionized methyl propene. The results of the investigation of C$\sb7$H$\sb5\sp+$ ions from various precursor molecules are also described. The following compounds, which all produce C$\sb7$H$\sb5\sp+$ ions, were studied: benzyl acetate, benzyl formate, benzyl alcohol, 2-bromocyclopropabenzene, 1,6-heptadiyne and 1,5-decadiyne. According to the metastable ion (MI) mass spectra and the He collision induced dissociation (CID) of m/z 89 ions, it is suggested that four structures exist. (Abstract shortened by UMI.)
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Eichinger, Peter Charles Hans. "Negative ion rearrangements in the gas phase." Title page, contents and abstract only, 1991. http://web4.library.adelaide.edu.au/theses/09PH/09phe298.pdf.
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Cumeras, Olmeda Raquel. "Micro Ion Mobility Spectrometry for Gas-phase Detection." Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/131286.
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En un món ideal, podríem ser capaços de detectar ràpidament i classificar qualsevol tipus de substància química i biològica que es trobés en baixes concentracions, utilitzant instruments petits i de fàcil ús. És en aquest escenari on va aparèixer l'espectrometria de mobilitat iònica (IMS). Es tracta d'una tècnica de mesura i anàlisi, on els analits ionitzats es separen per diferències de mobilitat sota la influència d’un camp elèctric en un flux de gas neutre o d'aire a pressió i temperatura ambient. Els avantatges de l'IMS inclouen instrumentació compacte i portàtil, un temps de separació curt (escala de mili-segons), i uns límits de detecció baixos, i permeten una àmplia gamma d'aplicacions. En aquest sentit, un esforç intens de recerca s'ha enfocat cap a la miniaturització dels dispositius d'IMS disponibles vers als micro- espectròmetres de mobilitat iònica de forma d’ona asimètrica i d’alt camp (FAIMS).
En aquesta tesi es presenten els primers desenvolupaments i contribucions tecnològiques als FAIMS en el IMB-CNM (CSIC). En particular, aquest treball està dedicat a la simulació, disseny, i fabricació d'un micro FAIMS planar (p-FAIMS) per a aplicacions de seguretat. El treball s'organitza en cinc capítols dividits en dues seccions.
La primera secció consta de tres capítols. El primer capítol és introductori i en el segon capítol s'introdueix al lector en l'actual estat de la tècnica de l'espectrometria de mobilitat iònica en general i en particular per als micro- espectròmetres de mobilitat iònica de forma d’ona asimètrica i d’alt camp. El tercer capítol descriu el modelatge d'un tipus de FAIMS planar per a diferents camps elèctrics i condicions de flux.
La segona part consta de dos capítols. El quart capítol presenta un resum dels diferents dissenys i materials considerats per a la implementació del p-FAIMS: estructures Vidre-Si-Vidre i PCB-PMMA-PCB, les tasques tecnològiques fetes per cada un i les estratègies de solució que hi han conduit. La fotoionització UV ha estat l'escollida com a mètode de ionització en tots els casos per raons de seguretat. També es presenta la caracterització amb toluè del nou prototip de p-FAIMS de baix cost fabricat a l'IMB-CNM. El cinquè capítol es presenta un resum de l'estudi de la viabilitat del monitoratge d'un fàrmac analgèsic (remifentanil) en l’alè de pacients sota anestèsia. Un espectròmetre de mobilitat iònica comercial s'utilitza per a aquesta aplicació mèdica en col·laboració amb el KIST-Europe i la Chirurgische Universitätsklinik d'Homburg (Alemanya).In an ideal world, we might be able to rapidly detect and classify any type of chemical and biological that is found in low concentrations, using instruments of small size and easy implementation. Is in that scenario where the Ion mobility spectrometry (IMS) appeared. It is a technique of measurement and analysis, where ionized analytes are separated by mobility differences under electric field in a flow of neutral gas or air at ambient pressure and temperature. The advantages of IMS include compactness and portability of instrumentation, short separation time (milliseconds scale), and low detection limits, and allow a wide range of applications. In this sense, an intense research effort has been focused towards miniaturization from the available IMS’s devices to the micro high-Field Asymmetric waveform Ion Mobility Spectrometers (FAIMS). This thesis presents the first developments and technological contributions to the FAIMS at IMB-CNM (CSIC). Particularly, this work is dedicated to the simulation, design, and fabrication of a micro planar FAIMS (p-FAIMS) for security applications. The work is organized in five chapters divided in two sections. The first section consists of three chapters. Chapter one is introductory, and on Chapter two introduces the lector to the actual state-of-the-art of the Ion Mobility Spectrometry in general and in particular for the micro high-Field Asymmetric waveform Ion Mobility Spectrometry. Chapter three described the modeling of a planar type of FAIMS for different electric fields and flow conditions. The second section consists of two chapters. Chapter four provides a summary of the different designs and materials considered for the p-FAIMS implementation: Glass-Si-Glass and PCB-PMMA-PCB structures; the technological tasks done for each one and the solving strategies that have leaded to it. UV photoionization has been the chosen as ionization method for safety reasons in all cases. It also presents the characterization with toluene of the new low-cost p-FAIMS prototype fabricated in the IMB-CNM. Chapter five provides a summary of the feasibility study of an online-monitoring of an analgesic drug (remifentanil) in patients breath under anesthesia. A commercial Ion Mobility Spectrometer is used for this medical application in collaboration with the KIST-Europe and the Chirurgische Universitätsklinik from Homburg (Germany).
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Kullman, Michael John. "Computional chemistry studies of gas-phase ion structures." Thesis, Wichita State University, 2012. http://hdl.handle.net/10057/5412.
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Computational chemistry and mass spectrometry are two extremely useful tools that when used in conjunction with each other allow detailed knowledge of the gas-phase ions. To that end, computational chemistry, specifically density functional theory is used for theoretical to experimental frequency comparisons. This allows for insight into the reaction pathways and likely structures to be explored in detail.Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry
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Ochran, Richard Acquaah. "Experimental and theoretical studies of unimolecular reactions of gas phase cluster ions." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6141.
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The work presented in the following pages is the culmination of four years of research in the area of gas phase ion chemistry. During this period mass spectrometry and ab initio molecular orbital calculations were employed to investigate the unimolecular decomposition of proton-bound complexes between acetonitrile and methanol, ethanol, n-propanol, i-propanol, n-butanol, s-butanol, i-butanol, and t-butanol. Common to these systems, is a competition between dissociation of the hydrogen bond in the proton-bound dieter and isomerization to (CH3CNR)(H2O)+ (R=CH3, CH2CH3, CH2CH2CH3, CH(CH3)2, butyl). The minimum energy reaction pathways for the isomerization in these systems are presented and compared. The dominant isomerization pathway for these ions is an internal SN2 reaction that proceeds via an intermediate CH3CN &cdots; ROH2+ ion (R=CH3, CH2CH 3, CH2CH2CH3, CH(CH3) 2). The mass spectra for the four butanol containing dimers (n-, s-, i-, and t-butanol) show similar behaviour. The effect of chlorine substitution on the acetonitrile on the four systems methanol, ethanol, n- and i-propanol were also investigated. The theoretical and experimental studies reveal a potential energy surface which is very similar to that obtained for the CH 3CN containing analogues (CH3CN)(CH3OH)H +, (CH3CN)(CH3CH2OH)H+, (CH3CN)(CH3CH2CH2OH)H+ and (CH3CN)((CH3)2CHOH)H +. The effect of chloro-substitution of the acetonitrile does not significantly affect the height of the rate limiting isomerization barrier which governs the water loss channel. The chloro-substitution however, lowers the proton affinity of the chloroacetonitrile and hence where there is competition between simple cleavage and isomerization, the protonated alcohol outcompetes the protonated chloroacetonitrile in the MI mass spectra. The dimer ion of acetonitrile and oxygen exhibit three peaks at m/z 32 (O 2), m/z 41, (CH3CN and ·CH2CNH +) and m/z 56 (-OH) in its MI mass spectrum. When O2 (triplet ground state) encounters a CH3CN+· or ·CH2CNH+ ion, the resulting complex (C2H3N)(O2)+· can take on either a doublet or quartet character. RRKM calculations predict a fast forward isomerization of CH3CN+· to ·CH2CNH+. The fact the dissociation and isomerization compete on the microsecond timescale is an indication that the reactions do not occur statistically and that RRKM theory does not apply.
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Faull, Peter Allen. "Exploring gas-phase protein conformations by ion mobility-mass spectrometry." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3851.
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Analysis and characterisation of biomolecules using mass spectrometry has advanced over the past decade due to improvements in instrument design and capability; relevant use of complementary techniques; and available experimental and in silico data for comparison with cutting-edge research. This thesis presents ion mobility data, collected on an in-house modified QToF mass spectrometer (the MoQTOF), for a number of protein systems. Two haemoproteins, cytochrome c and haemoglobin, have been characterised and rotationally-averaged collision cross-sections for a number of multimeric species are presented. Intact multiply-charged multimers of the form [xCyt c + nH]z+ where x = 1 (monomer), x = 2 (dimer) and x = 3 (trimer) for cytochrome c have been elucidated and for species with x ≥ 2, reported for the first time. Fragment ions possibly attributed to a novel fragmentation mechanism, native electron capture dissociation, are reported with a brief discussion into their possible production from the dissociation of the gas-phase dimer species. Haemoglobin monomer globin subunits, dimers and intact tetramer have been successfully transferred to the gas phase, and their cross-sections elucidated. Comparisons with in silico computational data have been made and a discussion of the biologically-active tetramer association/dissociation technique is presented. Three further proteins have been studied and their gas-phase collision cross-sections calculated. Two regions of the large Factor H (fH) complement glycoprotein, fH 10-15 and fH 19-20, have been characterised for the first time by ion mobility-mass spectrometry. Much work using nuclear magnetic resonance spectroscopy has previously been achieved to produce structural information of these protein regions, however further biophysical characterisation using mass spectrometry may aid in greater understanding of the interactions these two specific regions have with other biomolecules. The DNA-binding core domain of the tumour suppressor p53 has been characterised and cross-sections produced in the presence and absence of the zinc metal ion that may control the domain’s biological activity. Within this core domain, p53 inactivation mutations have been shown to occur in up to 50% of human cancers, therefore the potential exists to further cancer-fighting activity through research on this region. Anterior Gradient-2 (AGR2) protein facilitates downregulation of p53 in an as yet unclear mechanism. Recent work using peptide aptamers has demonstrated that this downregulation can be disrupted and levels of p53 restored. Collision cross-sections for six peptide aptamers have been calculated, as well as cross-sections for multimers of AGR2 protein. A complex between one aptamer with the protein has also been elucidated. Use of the commercially available Synapt HDMS ion mobility-mass spectrometer at Waters MS Technologies Centre (Manchester, UK) allowed data to be collected for both Factor H protein regions and for the DNA-binding core domain of p53. Data are compared in the appropriate chapters with data collected using the MoQTOF.
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Harland, Peter W. "Studies of gas phase electron, ion and atom collision processes." Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/14990.
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The research papers submitted in this thesis describe experimental and theoretical investigations of particle collisions in which the projectiles have been electrons, ions and atoms, and the targets have been atoms and molecules. Non-reactive and reactive collisions have been studied in order to explore the fundamental nature of the collision event, to understand the dynamics, and to facilitate the determination of thermochemical parameters and reaction properties. The formation of positive and negative ions under single collision conditions as a function of electron impact energy has been investigated for small molecules and for molecular clusters. The measurement of accurate ionization efficiency curves and ionization thresholds has been achieved using custom designed near-monochromatic electron sources or analytical deconvolution. In many cases, detailed energy balancing has been attempted through the measurement of the recoil energies of fragment ions using retarding electric fields. Ionization mechanisms for associative and dissociative resonance electron capture and the formation of isomeric positive ions have been deduced. Thermochemical parameters, including electron affinities, ionization potentials, enthalpies of formation and bond dissociation energies, have been determined. Experiments in which the molecular targets were spatially oriented have shown, for the first time, that the mass spectrum and the ionization efficiency are orientation dependent. A theoretical model has been developed which accounts for the experimental measurements. Investigations of ion-molecule chemistry and non-reactive ion-molecule interactions have been carried out using a custom designed drift-tube mass spectrometer. It has been shown that isomeric ions can be distinguished by their ion transport properties and that the isomeric form of an ion-molecule reaction product ion can be directly measured. A theoretical model based on a generalised ion-helium interaction potential was developed which quantitatively accounted for the relative ion mobilities of a wide range of ions according to their physical properties.
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Jones, Chad A. "Ion Structure and Energetics in the Gas Phase Characterized Using Fourier Transfom Ion Cyclotron Resonance Mass Spectrometry." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4253.
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In this dissertation, I use Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) to study the structure and energetics of gas phase ions. Infrared multiphoton dissociation spectroscopy (IRMPD) is a technique for measuring the IR spectrum of gas phase ions in a Penning trap. I use this technique to investigate the conformation of cucurbituril complexes, terminal diamines, and protonated amino acids. Cross sectional areas by Fourier transform ion cyclotron resonance mass spectrometry (CRAFTI) is a technique developed by the Dearden lab to measure the cross section of gas phase ions. In this work, I further develop a fundamental understanding of this technique. I investigate the role that dissociation plays in this and other FTICR-MS techniques. I also show that the principles of the CRAFTI technique can be used to measure the pressure inside the cell of an FTICR-MS. This technique, linewidth pressure measurement (LIPS), allows for a quantitative measurement and comparison of CRAFTI cross sections. To demonstrate the improvements to the technique, I measure the CRAFTI cross sections for the 20 standard amino acids and compare these to literature values measured by ion mobility measurements.
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Newson, Karl Adrian. "The properties of gas-phase multiply charged ions." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324990.
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Villano, Stephanie M. "Gas-phase negative ion chemistry: Photoelectron spectroscopy, reactivity, and thermochemical studies." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3337158.
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Liu, Hao. "Understanding two-phase reaction processes in electrodes for Li-ion batteries." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709262.
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Selbe, Tyler J. "Applications of aluminosilicate and zincosilicate materials: aqueous phase ion exchange and gas phase adsorption." Diss., Kansas State University, 2010. http://hdl.handle.net/2097/7057.
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Doctor of PhilosophyDepartment of Chemical Engineering
Jennifer L. Anthony
Zeolites and zeolite-like materials have well-ordered structures and pores creating varying capacities for molecules based upon size, functional groups, polarity, and intermolecular forces making the materials useful for molecular sensing as well for molecules that are considered hazardous at very low concentrations with reproducible results because of these properties. This study will identify and characterize applications for zeolite and zeolite-like materials in gas and liquid phases based upon the dominating physical and chemical properties of the materials. The properties of interest include liquid phase ion exchange capacities, selectivities, gas/vapor phase adsorption capacity, and initial adsorption uptake rate. Zincosilicates have similar framework structures to aluminosilicate zeolites; however, they have distinct advantages over traditional zeolites. Zincosilicates typically have a higher ion density, lack “cages” in their structure which leads to all the cations being accessible for ion exchange, and have the ability to form three-membered rings which lead to large void spaces in their structure. These features lead to high capture capacities for divalent heavy metal mercury ions. In this work, the potential to use zincosilicates as ion exchangers such as VPI-7, VPI-9 and VPI-10 is presented. Results have shown that zincosilicates have capture capacities greater than traditional zeolites, even greater than those that have been synthesized with functional groups intended to increase metal sorption capacities. The selectivity coefficients in a binary ion exchange system were successfully modeled using the Gibbs-Donnan selectivity model. The selectivities for the zincosilicates were Pb>Na>Hg>K>Ca. Zeolites are also able to adsorb chemical species and therefore can be used as the recognition element in sensing devices. The sorption capacity of 2-chloroethyl ethyl sulfide, dimethyl methanephosphonate, ethanol, and n-butanethiol were examined with zeolites 13X, 4A, MCM-41, VPI-7, VPI-9, and ZSM-5. The zeolites selected provided very different framework composition, countercation, and surface area features for determining the most significant properties in adsorption. Zeolite 13X had the highest equilibrium and initial uptake rate for most compounds tested, whereas the low surface area zincosilicates, VPI-7 and VPI-9, had the lowest capacity. Based on these results, a piezoelectric device with an array of zeolites can be successfully employed as a sensor.
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Gill, Andrew Christopher. "An investigation of the structure of ions in the gas phase by tandem mass spectrometry." Thesis, University of Warwick, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340095.
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Walker, Nicholas R. "Gas-phase studies of multiply-charged transition metal complexes." Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299030.
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Anupriya, Anupriya. "Gas Phase Structure Characterization Using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6447.
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This dissertation investigates Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) based techniques to study the impact of molecular structure on conformation and binding energetics. A novel method to determine collison cross sectional areas using FTICR (CRAFTI), initially developed by the Dearden lab, was applied to study the conformations of molecular systems with unique structural attributes in an attempt to explore the molecular range of CRAFTI. The systems chosen for CRAFTI studies include crown-ether alkylammonium complexes and biogenic amino acids. The results were found to be consistent with expected behavior, and strongly correlated with experimental measurements made using ion mobility spectrometry (IMS) and predictions from computations. The analytical sensitivity of CRAFTI was highlighted by its ability to distinguish the normal and branched structural isomers of butylamine. Besides conformation characterization, quantitative evaluation of binding was undertaken on metal ion-cryptand complexes on the FTICR instrument using sustained off-resonance irradiation-collision-induced dissociation (SORI CID) method. Complex formation and dissociation was found to be a strong function of both guest and host sizes which impacted steric selectivity, and polarizability. The results demonstrate the ability of FTICR to simultaneously determine structure, conformation and binding thereby providing comprehensive molecular characterization.
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Chen, Yuping. "Ion-molecule clustering studies in the gas phase and solution phase by electrospray mass spectrometry." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0026/MQ51314.pdf.
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Ashman, A. S. "Laser spectroscopy of molecular ions in an Ion Cyclotron Resonance apparatus." Thesis, University of Reading, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234408.
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Sirois, Martin. "The assignment of gas phase ion structures and fragmentation mechanisms by mass spectrometry." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/10954.
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The interpretation of mass spectra has made great progress over the past decade, as experimental methods have been developed for assigning structures to organic ions in the gas phase. This thesis describes the important experiments in gas phase ion chemistry whose correct interpretation can lead to the assignment of structures, and the elucidation of fragmentation mechanisms of organic positive ions. The low energy fragmentations of five isomeric [H3,C,N,O 2]+· ions. The low energy fragmentation characteristics of the [H3,C,N,O2]+· isomers, H3CNO2+·, 1, H2C=N(O)OH+·, 2, H3CONO +·, 3, HC(O)NHOH+·, 4, and HC(OH)=NOH+·, 5, were studied in detail by metastable ion mass spectrometry. Appearance energy measurements established the potential energy surface of the isomers 1, 2 and 3 showing the intricate interrelation between them. For isomers 4 and 5, it was concluded that they do not intercommunicate with ions 1, 2 and 3 prior to fragmentation. Neutralization-reionization mass spectrometry indicated that the enol form of formohydroxamic acid structures as well as the keto analogue are stable in the gas phase. The neutral counterparts of the C2H7O + isomers. The neutral counterparts of the C2H 7O+ isomers, CH3O+(H)CH 3, CH3CH2OH2+ and C 2H4···H-OH2+ have been studied by means of neutralization-reionization mass spectrometry. It was observed that the internal energy of protonated dimethyl ether ions is directly related to the stability of the neutrals generated by electron transfer, and on their dissociation. With regard to CH3CH 2OH2+ and C2H4···H-OH 2+, it was concluded that the former ion can be obtained as a neutral species in the gas phase, whereas the latter isomer could not be produced as a neutral species. Classical and non-classical forms of the ethyl cation and their participation in the ions RO+(C2H5)R'. Oxonium ions formed via ion/molecule reactions between several oxygen centered molecules and the ethyl cation were studied. Significant H/D mixing in these oxonium ions was observed only when a labeled ethyl cation was reacted with a non-labeled ROR' molecule. The degree of H/D mixing depends only on the size of R and R', being independent of the observational timeframe from 1-30 mus. When non-labeled ethyl cations were reacted with labeled ROR' molecules, H/D mixing was not observed. The results were interpreted as arising from the classical and non-classical forms of the ethyl cation having different reactivities with ethers of different sizes. Homologous hydrogen-bridged intermediates R1R 2O···H···C(O)R3 from ionized beta-hydroxyethers. The unimolecular dissociations of several beta-hydroxyethers and some of their isotopomers were studied by metastable ion and collision induced dissociation mass spectrometry. It was found that molecular ions of the form R1OCH(R2)CH(OH)R 3 yield protonated ethers, R1O+(H)R2 , via intermediates of the type R1R2O···H···C(O)R 3+·.
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Bertier, Paul. "Study of solvated molecular ion stability in the gas-phase : cooling and irradiation." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1207/document.
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Les radiations peuvent endommager notre environnement biologique mais elles peuvent aussi être bienfaisantes si elles sont contrôlées. L'action initiale des radiations à l'échelle microscopique consiste en une excitation électronique dans une molécule. L'observation de la redistribution de l'énergie dans l'environnement de cette molécule excitée est primordiale à la compréhension et à la description de l'effet des rayonnements dans les systèmes biomoléculaires. Les agrégats de molécules isolés en phase gazeuse constituent des systèmes modèles prometteurs pour étudier les interactions entre molécules sous irradiation. La première partie de ce travail décrit la construction et la validation d'une ligne de faisceau permettant la production de paquets d'agrégats moléculaires froid injectables dans l'anneau de stockage RICE à RIKEN. La ligne de faisceau est composée d'une source electrospray, d'un filtre en masse quadripolaire, de guides d'ions d'un tube d'accélération, la pièce centrale étant un piège à ions cryogénique refroidi à 4 K. Le paquet d'ions froids, dont les ions ont été sélectionnés en masse et accélérés jusqu'à 20 keV, a été sondé avec un laser. La ligne a été validée par la mesure d'un spectre d'action du bleu de méthylène. La seconde partie de ce travail s'appuie sur les expériences réalisées auprès du dispositif d'irradiation d'agrégats moléculaires (DIAM-IPNL). La méthode COINTOF-VMI permet la mesure de la distribution de vitesse des molécules d'eau évaporées à partir d'un agrégat après collision à haute vitesse avec un atome d'argon. Les distributions de vitesse mesurées pour des agrégats mixtes pyridine protonée et eau présentent deux composantes : une partie à basse vitesse qui correspond à une évaporation après redistribution de l'énergie dans l'agrégat, et une partie à haute vitesse où la molécule d'eau est évaporée avant redistribution de l'énergie. La comparaison des résultats avec les distributions calculées par dynamique moléculaire statistique montre que la partie basse vitesse peut être interprétée comme la contribution des deux possibilités d'excitation induites par la collision : l'excitation de la pyridine protonée ou l'excitation d'une des molécules d'eauRadiation can damage our biological environment, but it can also be beneficial under certain controlled conditions. Initial action at microscopic scale consists of electronic excitation in molecules. The redistribution of this excitation energy to the environment is the primary process to be understood to describe the radiation effect on biomolecular system. Isolated molecular clusters in gas-phase are a promising model system to study the molecular interaction under radiation.The first part of this work describes the construction and the validation of a beamline which can produce bunches of cold molecular cluster ions to be injected in the RIKEN cryogenic electrostatic (RICE} storage ring. The beamline is composed of an electrospray ion source, a quadrupole mass filter, ion guides and an acceleration tube; with the main part being a cryogenic ion trap cool down to SK. The cold ion bunches, in which the ions have been mass selected and accelerated to 20keV, was probed with a laser. The beamline was successfully taken into operation and a measurement of the methylene blue action spectrum in gas-phase was carried out. The second part of this work rely on experiment realized with the dispositif d'irradiation d'agrégats moléculaires (DIAM-IPNL}. The COINTOF-VMI method allows the measurement of the velocity distributions of evaporated molecules from a cluster after high velocity collisions with an argon atom. The velocity distribution measured for mixed clusters protonated pyridine and water has two components: a low velocity part which corresponds to the evaporation of a water molecule after energy redistribution in the cluster, and a high velocity part in which the molecule is evaporated before total energy redistribution. Comparison with the distribution calculated by statistic molecular dynamic simulation shows that the low velocity part can be interpreted as the contribution of two possible excitations induced by collision: excitation on protonated pyridine and excitation on a water molecule
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Hopper, Jonathan T. S. "Studying protein-ligand complexes in the gas-phase using ion mobility-mass spectrometry." Thesis, University of Nottingham, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.576159.
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This thesis presents studies which investigate the application of electrospray ionisation-mass spectrometry (ESI-MS) to non-covalent protein-ligand complexes. The structural effect of desolvation on protein-ligand (P-L) complexes has been a hotly debated issue in this field and has been examined in this work. Single point mutagenesis has allowed specific non-covalent interactions to be probed as well as their contribution to gas-phase protein- ligand stability. Results suggest that these specific interactions are preserved in the gas-phase using ESI. Other solution based effects that result from ligand binding, such as increased protein structural stability, was also confirmed in the gas-phase. A combination of collisional activation and ion mobility spectrometry is presented as an approach capable of probing such subtle stability differences. Some discrepancies between the behaviour of protein- ligand complexes in solution and the gas-phase are also presented and highlight potential areas of caution in certain biological systems. Common alkali metal adducts have been shown to severely decrease the stability of protein-ligand complexes in the gas-phase, possibly by a Coulomb assisted dissociation mechanism. Novel approaches to allow greater control of charge state distributions, without the requirement of instrumental modifications, are also presented. Reducing the charge state of protein complexes in the gas-phase allows weak interactions to be more readily preserved and more accurate affinity measurements to be made. The approach is also confirmed to reduce the amount of alkali metal adduction observed in protein ions generated by ESI.
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Luo, Zhaohui. "GC/FT-ICR Mass Spectral Analysis of Complex Mixtures: A Multidimensional Approach for Online Gas Phase Basicity Measurements." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/LuoZX2006.pdf.
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Ricketts, Claire Louise. "The reactions of gas phase doubly-charged ions with neutral molecules of relevance to planetary ionospheres." Thesis, University of London, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497500.
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Odeneye, Michael Adetunji. "Infrared photodissociation of gas phase ions : single photon and multiphoton events." Thesis, University of Sussex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311414.
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McCullough, Bryan John. "Development of an ion mobility mass spectrometer to study gas phase conformations of biomolecules." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/15325.
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Design, development and implementation of a new Ion Mobility capable Mass Spectrometer – the MoQToF – are presented. The instrument is a Micromass Q-ToF modified to include a temperature regulated drift cell. Initial testing of the instrument to measure cross sections of well characterised proteins (cytochrome C, ubiquitin and lysozyme) in a range of charge states is described, showing the apparatus to perform well in comparison with values reported by others on analogous instruments. Ion mobility data is presented on a number of novel systems from small peptides to large proteins. The largest volume of work focuses on the study of β-defensins and related peptides. Β-defensins are small anti-microbial peptides that form a vital part of the innate immune system of all mammals, they are characterised by the presence of six conserved cysteine residues connected via disulphide bonds. Characterisation of these bonds (number and topology) using mass spectrometry based techniques is presented. The ion mobility data presented here probes the influence of these disulphide bonds on conformational flexibility. The mode of action of β-defensins is not known, two techniques designed to further understanding of this are described here. Firstly, a mass spectrometry based technique in which the interaction between a defensin, DEFB107, and an artificial membrane is studied using hydrogen deuterium exchange revealing the N-terminal section of the peptide to interact favourably with the lipid bilayer. Secondly, a heparin binding assay is described revealing a relationship between heparin binding strength and anti-microbial activity. This interaction is further studied using the MoQToF and molecular modelling.
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Ridal, Jeffrey J. "An analysis of the gas phase (benzyl radical)(+) ion populations generated from simple aromatic molecules." Thesis, University of Ottawa (Canada), 1987. http://hdl.handle.net/10393/5324.
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Fagiani, Matias Ruben [Verfasser]. "Cryogenetic ion vibrational spectroscopy of gas-phase clusters : Structure, Anharmonicity and Fluxionality / Matias Ruben Fagiani." Berlin : Freie Universität Berlin, 2017. http://d-nb.info/113162937X/34.
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Uechi, Guy Takeo. "Infrared photophysics of gas phase ions in a Fourier transform ion cyclotron resonance mass spectrometer." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1056650065.
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