Dissertations / Theses on the topic 'Gas-Phase Ion'
To see the other types of publications on this topic, follow the link: Gas-Phase Ion.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Gas-Phase Ion.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
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.
Full text
2
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.
Full text
3
Cumeras, Olmeda Raquel. "Micro Ion Mobility Spectrometry for Gas-phase Detection." Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/131286.
Full textAbstract:
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).
4
Kullman, Michael John. "Computional chemistry studies of gas-phase ion structures." Thesis, Wichita State University, 2012. http://hdl.handle.net/10057/5412.
Full textAbstract:
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
5
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.
Full textAbstract:
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.
6
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.
Full textAbstract:
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.)
7
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.
Full text
8
Faull, Peter Allen. "Exploring gas-phase protein conformations by ion mobility-mass spectrometry." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3851.
Full textAbstract:
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.
9
Harland, Peter W. "Studies of gas phase electron, ion and atom collision processes." Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/14990.
Full textAbstract:
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.
10
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.
Full text
11
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.
Full text
12
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.
Full text
13
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.
Full textAbstract:
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.
14
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.
Full textAbstract:
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.
15
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.
Full text
16
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.
Full text
17
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.
Full text
18
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.
Full textAbstract:
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.
19
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.
Full text
20
Anupriya, Anupriya. "Gas Phase Structure Characterization Using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6447.
Full textAbstract:
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.
21
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.
Full text
22
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.
Full textAbstract:
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.
23
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.
Full text
24
Rius, i. Riu Jaume. "Gas phase molecular relaxation probed by synchrotron radiation experiments." Doctoral thesis, KTH, Physics, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3411.
Full textAbstract:
This thesis presents experimental studies of gas phasemolecular relaxation after excitation with synchrotron photonsin the 15-35 eV and in the 70-350 eV regions.
In the 15-35 eV region, molecular relaxation by neutraldissociation processes and non
Franck-Condon effects in N2 and O2 molecules have beenstudied by means of dispersed fluorescence and photoelectronspectroscopy experimental techniques, respectively. From thedispersed fluorescence data, excitation functions for themeasured atomic fluorescence spectra have been obtained. Fromthe recorded photoelectron spectra vibrational branching ratioshave been produced. The results obtained reveal that Rydbergseries and singly and doubly excited valence states of theappropriate symmetry energetically accessible in the studiedregion and interactions between themaccount for most of theobserved effects in these two type of experiments.
In the 70-350 eV range, molecular relaxation processesresulting in fragmentation of CD4 and SF6 after absorption ofsynchrotron light have been studied by energy resolved electronion coincidence technique using a multicoincidence experimentalstation developed by our group during the last five years forsuch type of experiments. The coincidence measurements yieldedmass spectra from which information about the kinematics of thedetected fragments has been deduced by means of Monte Carlosimulations of the experimental peak shapes. The obtainedresults show completely different dissociation patternsdepending on the molecular electronic states studied. Thesepatterns reflect the bonding properties of the excited orbitalsand they permit the description and in some cases theidentification of the different molecular relaxation pathwaysobserved. The achievements presented in this thesis exemplifythe potential of the multicoincidence station used in thereported experiments.
25
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.
Full textAbstract:
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+·.
26
Bertier, Paul. "Study of solvated molecular ion stability in the gas-phase : cooling and irradiation." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1207/document.
Full textAbstract:
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
27
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.
Full textAbstract:
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.
28
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.
Full text
29
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.
Full textAbstract:
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.
30
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.
Full text
31
Dong, Qian. "Studies of transport in some oxides by gas phase analysis." Licentiate thesis, Stockholm, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-363.
Full text
32
Mason, Kyle. "Stepwise Solvation of Organic Radical Cations by Ionic Hydrogen and Halogen Bonding in the Gas Phase." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/6024.
Full textAbstract:
The ability to characterize the interactions between ions and solvent molecules plays a critical role in understanding fundamental aspects of thermodynamics in solution chemistry. These interactions are often difficult if not impossible to observe in solution due to the number of solvent molecules far exceeding that of the ions. However, this challenge can be circumvented in the gas phase which enables the isolation and study of reactions between a single ion and single solvent molecule.
Within the field of ion-molecule chemistry are two sub-categories of interactions known as ionic hydrogen bonds (IHBs) and ionic halogen bonds (IXBs). In these interactions, the incorporation of a charged species permits ion-dipole interactions which are innately stronger than those found in dipole-dipole interactions among neutral molecules.
This dissertation describes and explains the interactions which take place between halogenated benzenes (F-, Cl-, Br-, and Iodobenzene) and neutral polar molecules (water, acetonitrile, acetone, and methanol). Additional studies on ionic hydrogen bonding involve the exploration of protonated benzonitrile monomer and dimer solvated by methanol. All systems were examined using the mass-selected ion mobility technique using the VCU mass selected ion mobility mass spectrometer. Thermochemical equilibrium measurements, in conjunction with density functional theory (DFT) calculations, were performed, enabling comparison between experimentally and theoretically determined binding energies. Additionally, the DFT calculations were able to validate hypothetical predictions for the lowest energy structures of each interaction. Furthermore, the averaged collision cross sections of the benzonitrile dimer radical cation, protonated benzonitrile dimer, and benzonitrile solvated hydronium ion were elucidated using the technique of ion mobility where experimentally determined cross sections were compared with theoretical collision cross section calculations on predetermined geometries that were optimized using DFT calculations.
33
Sawyer, Holly Ann. "Investigation of the effect of intra-molecular interactions on the gas-phase conformation of peptides as probed by ion mobility-mass spectrometry, gas-phase hydrogen/deuterium exchange, and molecular mechanics." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3093.
Full textAbstract:
Ion mobility-mass spectrometry (IM-MS), gas-phase hydrogen/deuterium (H/D) exchange ion molecule reactions and molecular modeling provide complimentary information and are used here for the characterization of peptide ion structure, including fine structure detail (i.e., cation-π interactions, β-turns, and charge solvation interactions). IM-MS experiments performed on tyrosine containing tripeptides show that the collision cross-sections of sodiated, potassiated and doubly sodiated species of gly-gly-tyr are smaller than that of the protonated species, while the cesiated and doubly cesiated species are larger. Conversely, all of the alkali-adducted species of try-gly-gly have collision cross-sections that are larger than that of the protonated species. The protonated and alkali metal ion adducted (Na+, K+ and Cs+) species of bradykinin and bradykinin fragments 1-5, 1-6, 1-7, 1-8, 2-7, 5-9 and 2-9 were also studied using IM-MS and the alkali metal ion adducts of these species were found to have cross-sections very close to those of the protonated species. Additionally, multiple peak features observed in the ATDs of protonated bradykinin fragments 1-5, 1-6 and 1-7 are conserved upon alkali metal ion adduction. It was observed from gas-phase H/D ion molecule reactions that alkali adducted species exchange slower and to a lesser extent than protonated species in the tyrosine- and arginine-containing peptides. Experimental and computational results are discussed in terms of peptide ion structure, specifically the intra-molecular interactions present how those interactions change upon alkali salt adduction, as well as with the sequence of the peptide.
Additionally, IM-MS data suggests the presence of a compact conformation of bradykinin fragment 1-5 (RPPGF) when starting from organic solvent conditions. As water is added stepwise to methanolic solutions, a more extended conformation is populated. When the starting solution is composed of ≈90% water, two distinct mobility profiles are observed as well as a shoulder, indicating the presence of three gas-phase conformations for RPPGF. Gas-phase H/D exchange of [M+H]+ ions prepared from aqueous solvents show a bi-exponential decay, whereas samples prepared from organic solvents show a single exponential decay. The effect of solvent on gas-phase peptide ion structure, i.e., solution-phase memory effects, is discussed and gas-phase structures are compared to know solution-phase structures.
34
Zhang, Haizhen. "Characterization of Cucurbituril Complex Ions in the Gas Phase Using Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1582.pdf.
Full text
35
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.
Full text
36
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.
Full text
37
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.
Full text
38
Gucinski, Ashley Christine. "Gas Phase Structural Studies of Peptide Fragment Ions: Structural Insights into Mass Spectrometry Fragmentation Mechanisms." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202766.
Full textAbstract:
This dissertation presents extensive structural studies of gas-phase peptide fragment ions, with a specific focus on b₂⁺ ions. Fragment ion structures can provide important insights into peptide fragmentation mechanisms. Based on the structures formed, information about the preference of competing b ion formation pathways can be obtained. b₂⁺ ion structures are of interest because of their large relative abundances in MS/MS spectra, which are difficult to predict. Prior to this work, only a few b₂⁺ ion structures were determined; these systems featured only aliphatic residues and all formed oxazolones. The work presented herein examines the influence of basic, acidic, and backbone-attached sidechains on peptide fragmentation mechanisms, as revealed by the resulting b₂⁺ fragment ion structure(s) formed. Specifically, the structures of several histidine, aspartic acid, and proline-containing b₂⁺ ions are determined by using action IRMPD spectroscopy, fragment ion HDX, and DFT calculations. The structures of a series of histidine analogue-containing b₂⁺ ions reveal that the location and availability of the pi-nitrogen is essential for diketopiperazine formation. The histidine sidechain bulk or strain interferes with the complete trans-cis isomerization required for diketopiperazine formation, so the oxazolone structure is also present. Xxx- Pro b₂⁺ ions favor oxazolone formation with aliphatic N-terminal residues. HP favors the diketopiperazine, combining the histidine effect and the proline cis conformation propensity. For Xxx-Asp b₂⁺ ions, aspartic acid significantly influences b₂⁺ ion structure only with an N-terminal histidine or lysine; both HD and KD form a mixture of oxazolone, anhydride, and diketopiperazine structures, presenting the first spectroscopic evidence for the anhydride b₂⁺ion structure. The HA and AH b₂⁺ ions feature the same structures, but HP and PH do not, showing that residue position matters. Additionally, while relative intensities and HDX rates featured some fluctuation, peptide precursor composition differences did not alter the mixture of b₂⁺ ion structures formed for a given b₂⁺ ion. To complement existing gas-phase structural methods, the utility of a new technique, QCID-HDX-IRMPD, was applied to m/z 552.28 from YAGFL-OH. Both the standard b₅⁺ fragment ion and an isobaric non-C-terminal water loss ion are present. Without separation of these isomers, MS/MS spectral interpretation would be complicated.
39
Warnke, Stephan [Verfasser]. "A Gas-Phase Approach to Biomolecular Structure: Combining Ion Mobility-Mass Spectrometry with Spectroscopy / Stephan Warnke." Berlin : Freie Universität Berlin, 2015. http://d-nb.info/1080522131/34.
Full text
40
Remes, Philip M. Glish Gary L. "Instrumentation and methods for the characterization of ion structure and internal energy in the gas phase." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1434.
Full textAbstract:
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Apr. 25, 2008). " ... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.
41
Hoffmann, Waldemar [Verfasser]. "Investigation of Biomolecular Assemblies by Ion Mobility-Mass Spectrometry and Gas-Phase Infrared Spectroscopy / Waldemar Hoffmann." Berlin : Freie Universität Berlin, 2018. http://d-nb.info/1176708872/34.
Full text
42
Hall, Zoe Lauren. "Protein complexes in the gas phase : structural insights from ion mobility-mass spectrometry and computational modelling." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:a958f616-e37f-42e2-bf57-a38d58388b0c.
Full textAbstract:
Structure determination of macromolecular protein assemblies remains a challenge for well-established experimental methods. In this thesis, an emerging structural technique, ion mobility-mass spectrometry (IM-MS) is explored. An assessment of collision cross section (CCS) measurement accuracy using travelling-wave IM (TWIMS) instrumentation was carried out (Chapter 3). Through the collation of a protein complex CCS database and the development of a calibration framework for TWIMS, significant improvements to CCS measurement accuracy have been achieved. Next, the advantages and limitations of using IM-MS to generate restraints for structure characterisation were explored. Computational tools designed to exploit IM-MS data for structural modelling were developed and tested on a training set of systems (Chapter 4). These include two heteromeric protein complexes, and an oligomeric intermediate involved in beta-2-microglobulin aggregation. Further structural information can be attained by using gas-phase dissociation techniques, such as collision-induced dissociation (CID). The effects of charge state on CCS and the gas-phase dissociation pathway of complexes were investigated (Chapter 5). This highlighted the possibility of using CID in conjunction with supercharging to manipulate dissociation pathways to achieve more useful structural information. Finally, the gas-phase structures of globular and intrinsically disordered protein complexes were probed by IM-MS and molecular dynamics (MD) simulations (Chapter 6). Experimental observations were recapitulated remarkably closely by simulations, including gas-phase structural collapse and the ejection of monomer subunits when the energy of the system was increased sufficiently. Overall, this research has contributed to the IM-MS field by providing the framework for improved CCS measurements of large protein complexes and the use of restraints from IM-MS for structural modelling. Significantly, IM-MS has been used in combination with charge manipulation, CID and MD simulations to reveal further insights into the gas-phase structures, stabilities and dissociation pathways of multimeric protein complexes.
43
Alsharaeh, Edreese Housni. "Gas Phase Studies of Molecular Clusters Containing Metal Cations, and the Ion Mobility of Styrene Oligomers." VCU Scholars Compass, 2004. http://scholarscompass.vcu.edu/etd/1200.
Full textAbstract:
This study is divided into three parts. Part I deals with the mechanism of the self-initiated polymerization (or thermal polymerization) of styrene in the gas phase. In this work, we present the first direct evidence for the thermally self-initiated polymerization of styrene in the gas phase. Our approach is based on on-line analysis of the gas phase Oligomers by mass-selected ion mobility. The mobility measurements provide structural information on the ionized oligomers based on their collision cross-sections (Ω) which depend on the geometric shapes of the ions. Theoretical calculations of possible structural candidates of the Oligomers ions are then used to compute angle averaged Ω for comparison with the measured ones. The agreement between the measured and calculated Ω of the candidate structures provides reliable assignments to the structures of the oligomers. Furthermore, collisional-induced dissociations of the mass-selected oligomer ions provide further support for the structures obtained from the mobility measurements. Our results indicate that the gas phase polymerization of styrene proceeds via essentially the same initiation mechanism (the Mayo mechanism) as in condensed phase polymerization. The structural evidence, the mechanism of formation and the observed fragmentation pathway of the growing dimers and trimers in the gas phase are presentedIn Part II the solvation of a variety of metal cations by benzene clusters have been studied using laser vaporization, cluster beam and time-of-flight mass spectrometry techniques. In this work strong magic numbers were observed for clusters containing 10, 13 and 14 benzene molecules depending on the nature of the metal cation involved. The metal cations exhibiting preference solvation by 14 benzene molecules show a strong tendency to form sandwich structures with two benzene molecules. The interpretation of these results in view of the proposed structures and the growth patterns of the clusters are presented. In Part III, the work is focused on the investigation of the intracluster ion molecule reactions following the generation of Mg+ within the polar clusters (water, methanol, ether and acetonitrile).
44
Robinson, Jessica Marie. "Examination of gas-phase conformations of oligonucleotides using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
Full text
45
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.
Full textAbstract:
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.
46
Platt, Sean P. "Interactions of the Naphthalene Radical Cation with Polar and Unsaturated Molecules in the Gas Phase." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4210.
Full textAbstract:
Characterizing the interactions of solvent molecules with ions is fundamental in understanding the thermodynamics of solution chemistry. These interactions are difficult to observe directly in solution because the number of solvent molecules far exceed that of ions. This lend the gas phase to be the ideal medium in the study ion-solvent interactions on a molecular level. Ionized polycyclic aromatic hydrocarbon (PAH) molecules can readily form hydrogen bonds with neutral solvent molecules in aqueous and interstellar medium. Previous research has been done for stepwise solvation of small molecules such as benzene+, pyridine, and phenylacetylene. The similarity in these results show that these organic ions can be considered prototypical model systems for aromatic ion-neutral solvent interactions. The goal of this dissertation is to demonstrate that naphthalene can act as a prototypical model of PAH ions for ion-solvent interactions.
Two types of experiments are considered throughout this dissertation using ion mobility mass spectrometry: (1) ion-neutral equilibrium thermochemistry and (2) mobility measurements. For thermochemistry experiments, the naphthalene radical cation was injected into the drift cell containing helium and/or neutral solvent vapor and the enthalpy and entropy changes were measured by varying the drift cell temperature and measuring the equilibrium constants. The results of these studies showed that small polar molecules bind to naphthalene with similar energy based on the measured by the enthalpy changes. Unsaturated aliphatic molecules behave similarly, but with much lower binding energy. Aromatic ions tend to bind to the naphthalene with lower binding energy than that observed with the benzene ion. The results for small polar molecules were compared to similar studies using the phenyl cation. The second series of experiments required the coexpansion of the naphthalene and benzene or pyridine. Injecting theses dimers into the drift cell allowed the measurement of reduced mobility on the dimers at a series of temperatures. These were used to calculate the average collision cross section and thus give insight in to the structure of these aromatic dimers. Structures were determined by comparing these results to those predicted by DFT calculations.
47
Mabrouki, Ridha Ben Mohsen. "Drift Tube Ion Mobility Measurements for Thermochemistry, Kinetics and Polymerization of Cluster Ions." VCU Scholars Compass, 2007. http://scholarscompass.vcu.edu/etd/1165.
Full textAbstract:
In this work, the Drift Tube Ion Mobility technique is used to study the hydrophobic hydration and solvation of organic ions and measure the thermochemistry and kinetics of ion-molecule reactions. Furthermore, an exploratory study of the intracluster polymerization of isoprene will be presented and discussed. The ion hydration study is focused on the C3H3+ cation1 and Pyridine▪+ radical cation.2 The chemistry of the cyclic C3H3+ cation1 has received considerable attention and continues to be an active area of research.3-7 The binding energies of the first 5 H2O molecules to c-C3H3+ were determined by equilibrium measurements. The measured binding energies of the hydrated clusters of 9-12 kcal/mol are typical of carbon-based CH+X hydrogen bonds. The ion solvation with the more polar CH3CN molecules results in stronger bonds consistent with the increased ion-dipole interaction. Ab initio calculations show that the lowest energy isomer of the c-C3H3+(H2O)4 cluster consists of a cyclic water tetramer interacting with the c-C3H3+ ion, which suggests the presence of orientational restraint of the water molecules consistent with the observed large entropy loss. The c-C3H3+ ion is deprotonated by 3 or more H2O molecules, driven energetically by the association of the solvent molecules to form strongly hydrogen bonded (H2O)nH+ clusters. The kinetics of the associative proton transfer (APT) reaction C3H3+ + nH2O → (H2O)nH+ + C3H2 exhibits an unusually steep negative temperature coefficient of k = cT(sup>63±4 (or activation energy of -32 ± 1 kcal mol-1). The behavior of the C3H3+/water system is exactly analogous to the benzene+ /water system8,9, suggesting that the mechanism, kinetics and large negative temperature coefficients may be general to multibody APT reactions. These reactions can become fast at low temperatures, allowing ionized polycyclic aromatics to initiate ice formation in cold astrochemical environments.The solvation energies of the pyridine+ radical cation by 1- 4 H2O molecules are determined by equilibrium measurements in the drift cell. The binding energies of the pyridine+(H2O)n clusters are similar to the binding energies of protonated pyridineH+(H2O)n clusters that involve NH+∙∙OH2 bonds, and different from those of the solvated radical benzene+(H2O)n ions that involve CHδ+∙∙OH2 bonds. These relations indicate that the observed pyridine+ ions have the distonic C5H4NH+ structure that can form NH+∙∙OH2 bonds. The observed thermochemistry and ab initio calculations show that these bonds are not affected significantly by an unpaired electron at another site of the ion. The distonic structure is also consistent with the reactivity of pyridine+ in H atom transfer, intra-cluster proton transfer and deprotonation reactions. The results present the first measured stepwise solvation energies of distonic ions, and demonstrate that cluster thermochemistry can identify distonic structures.The gas phase clustering of small molecules around the hydronium ion is of fundamental interest and is relevant to important atmospheric and astrophysical processes. In this work, the equilibrium constants for the formation of the H3O+(X)n clusters with X = H2, N2 and CO and n = 1-3 at different temperatures are measured using the drift tube technique10. The arrival time distributions (ATDs) of the injected H3O+ and the H3O+(X)n clusters formed inside the cell are measured under equilibrium conditions. The resulting binding energies for the addition of one and two hydrogen molecules are similar [3.4 and 3.5 kcal/mol, respectively). For the N2 clustering with n = 1-3, the measured binding energies are 7.9, 6.9 and 5.4 kcal/mol, respectively. The clustering of CO on the H3O+ ion exhibits a relatively strong binding energy (11.5 kcal/mol) consistent with the dipole moment and polarizability of the CO molecule. Theoretical calculations of the lowest energy structures are correlated to the experimental results. Finally, intracluster polymerization leading to the formation of covalent bonded oligomer ions has been investigated following the ionization of neutral isoprene clusters. The results indicate that isoprene dimer cation has a structure similar to that of the limonene radical cation. Mass-selected mobility and dissociation studies also indicate that the larger isoprene cluster ions have covalent bonded structures. The conversion of molecular clusters into size-selected oligomers is an important process not only for detailed understanding of the early stages of polymerization but also for practical applications such as the formation of new polymeric materials with controlled and unusual properties.
48
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.
Full textAbstract:
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.
49
Wang, Xian. "Experimental and theoretical studies of ion-molecule complexes and of some ionized diketones in the gas-phase." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/29323.
Full textAbstract:
This thesis describes some research in gas-phase ion chemistry, using mass spectrometry techniques combined with theoretical calculations. Metastable ion and collision-induced dissociation mass spectra, kinetic energy release and isotopic labelling were used to characterize and identify precursor and fragment ions and to predict reasonable reaction mechanisms which were then further elucidated by calculations. MP2, B3-LYP and G3 levels of theory were employed to obtain the structures corresponding to energy minima and transition states and thus to obtain a complete potential energy surface for each system.
A major focus of this work was to investigate the unimolecular reactions of some ion-molecule complexes, especially the isomerizations that take place within them and then to discover the mechanisms by which such reactions take place. Particular attention was devoted to ion-molecule complexes that comprise ketones (including aldehydes), enols and distonic ions of alcohols.
The first two systems studied were acetaldehyde associated with the distonic methanol cation (•CH2OH2 +), [CH3CHO/H+O(H)CH2 •], and with its conventional isomer (CH3OH +•), [CH3CHO/+•HOCH3]. The isomerization barrier for ionized acetaldehyde to rearrange to its enol isomer, vinyl alcohol CH2CHOH+•, was lowered significantly (by 133 kJ/mol) by its association with •CH 2OH2+. This reaction resulted from a H +/H• transfer mechanism, involving a transition state of low energy requirement. In contrast, the CH3OH +• ion did not facilitate the rearrangement of acetaldehyde to its enol ion. Similar observations were obtained for ion-molecule complexes of acetone and methanol, [(CH3)2C=O/H+O(H)CH 2•] and [(CH3)2C=O/ +•HOCH3]. One metastable ion dissociation of the latter involved the loss of a methyl radical, producing a new [C3H 7O2]+ isomer, [CH3C+···(H)OCH 3], whose structure was assigned by calculations.
A water molecule is one of the smallest species that have been used as a catalyst within an ion-molecule complex, thus the gas-phase reactions of the ion [CH3CHO/H2O]+• were also investigated in this thesis. The metastable ion (MI) mass spectrum revealed that this ion-molecule complex decomposed spontaneously by the losses of H 2O, CO and •CH3. Hydrogen-bridged water complexes were found to be the major products of the losses of CO and •CH3. The CO loss produced the [•CH 3···H3O+] ion and involved a backside displacement mechanism. The product ions arising from • CH3 loss (via two different reaction channels) were assigned by theory to be the isomers, [OC···H3O +] and [CO···H3O+], and their 298 K enthalpy values, calculated at the G3 level of theory are Delta fH[OC···H3O+] = 420 kJ/mol and DeltafH[CO···H3O+ ] = 448 kJ/mol. (Abstract shortened by UMI.)
50
Soldi-Lose, Héloïse. "Gas phase ion and radical chemistry of CO2 adducts with possible relevance in the atmosphere of Mars." Aachen Shaker, 2008. http://d-nb.info/991820215/04.
Full text