Browsing by Subject "Ion Mobility"
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Item Development of a maldi − ion mobility− surface-induced dissociation − time-of-flight mass spectrometer with novel collision source configurations for high throughput peptide sequencing(2009-05-15) Sun, WenjianA Matrix-assisted Laser Desorption/Ionization (MALDI) ? Ion Mobility (IM) ? Surface-induced Dissociation (SID) ? Time-of-Flight (TOF) instrument with three different collision source configurations was developed in order to improve the SID performance in high throughput peptide sequencing. The first version of the instrument was equipped with an angle resolved SID source in order to maximize the collection efficiency of the SID scattering ions. An orthogonal TOF was also implemented as the second MS stage in this instrument to increase mass resolution. The second version of the instrument was developed towards simplifying the coupled configuration of the IM, SID and TOF components by using a combined SID/TOF source with a confinement ring electrode as the collision target. The fragmentation efficiency of SID in this configuration was increased up to 50% due to the surface normal impact angle used as compared with the results from a previous experiment using 45 degree impact angle. The third version of the instrument was equipped with a dual-source/dual-detector TOF to facilitate high throughput tandem analysis of peptides through simultaneous separation, fragmentation and mass analysis, while retaining precursor ion identity in the same experimental sequence. A series of small organic molecules, model peptides and tryptic peptides from a protein digest were analyzed to demonstrate the utility of these new designs for enhanced SID performance and peptide sequencing capability. Finally, a new mobility drift cell using a periodic focusing mechanism has been designed and fabricated to replace the previous uniform field drift cell. Improvement in ion transmission has been observed in the periodic focusing drift cell instrument without sacrificing the mobility resolution.Item Development of a variable-temperature ion mobility/ time-of-flight mass spectrometer for separation of electronic isomers(Texas A&M University, 2005-08-29) Verbeck, Guido FridolinThe construction of a liquid nitrogen-cooled ion mobility spectrometer coupled with time-of-flight mass spectrometry was implemented to demonstrate the ability to discriminate between electronic isomers. Ion mobility allows for the separation of ions based on differing cross-sections-to-charge ratio. This allows for the possible discrimination of species with same mass if the ions differ by cross-section. Time-offlight mass spectrometry was added to mass identify the separated peak for proper identification. A liquid nitrogen-cooled mobility cell was employed for a two-fold purpose. First, the low temperatures increase the peak resolution to aid in resolving the separated ions. This is necessary when isomers may have similar cross-sections. Second, low temperature shortens the mean free path and decreases the neutral buffer gas speeds allowing for more interactions between the ions and the drift gas. Kr2+ study was performed to verify instrument performance. The variable-temperature ion mobility spectrometer was utilized to separate the distonic and conventional ion forms of CH3OH, CH3F, and CH3NH2 and to discriminate between the keto and enol forms of the acetone radical cation. Density functional theory and ab initio calculations were employed to aid in proper identification of separating isomers. Monte Carlo integration tools were also developed to predict ion cross-section and resolution within a buffer gas.Item Development of matrix assisted laser desorption ionization-ion mobility-orthogonal time-of-flight mass spectrometry as a tool for proteomics(Texas A&M University, 2005-08-29) Ruotolo, Brandon ThomasSeparations coupled to mass spectrometry (MS) are widely used for large-scale protein identification in order to reduce the adverse effects of analyte ion suppression, increase the dynamic range, and as a deconvolution technique for complex datasets typical of cellular protein complements. In this work, matrix assisted laser desorption-ionization is coupled with ion mobility (IM) separation for the analysis of biological molecules. The utility of liquid-phase separations coupled to MS lies in the orthogonality of the two separation dimensions for all analytes. The data presented in this work illustrates that IM-MS relies on the correlation between separation dimensions for different classes (either structural or chemical) of analyte ions to obtain a useful separation. For example, for a series of peptide ions of increasing mass-to-charge (m/z) a plot drift time in the IM drift cell vs. m/z increases in a near-linear fashion, but DNA or lipids having similar m/z values will have very different IM drift time-m/z relationships, thus drift time vs. m/z can be used as a qualitative tool for compound class identification. In addition, IM-MS is applied to the analysis of large peptide datasets in order to determine the peak capacity of the method for bottom-up experiments in proteomics, and it is found that IM separation increases the peak capacity of an MS-only experiment by a factor of 5-10. The population density of the appearance area for peptides is further characterized in terms of the gas-phase structural propensities for tryptic peptide ions. It is found that a small percentage (~3%) of peptide sequences form extended (i.e., helical or β-sheet type) structures in the gas-phase, thus influencing the overall appearance area for peptide ions. Furthermore, the ability of IM-MS to screen for the presence of phosphopeptides is characterized, and it is found that post translationally modified peptides populate the bottom one-half to one-third of the total appearance area for peptide ions. In general, the data presented in this work indicates that IM-MS offers dynamic range and deconvolution capabilities comparable to liquid-phase separation techniques coupled to MS on a time scale (ms) that is fully compatible to current MS, including TOF-MS, technology.Item Hyphenating Ion Mobility With Mass Spectrometry to Increase the Information Content of Top-Down Analyses(2014-04-25) Zinnel, NathanaelMass spectrometry (MS) has been established as important analytical tool in the characterization of an array of analyte classes, including biological samples. However, without hyphenation with other techniques, the approach has limitations to the information that can be elucidated and the samples that can be analyzed. In an attempt to overcome these limitations, separation is performed prior to MS analysis to aid in alleviating sample complexity while dissociation is incorporated to increase the information content. Here, we employ ion mobility (IM), a gas-phase separation technique, to disperse product ions resulting from collision-induced dissociation (CID), denoted as MS-CID-IM-MS, for top-down analysis for a variety of applications, specifically, primary structure elucidation, disulfide bond identification, secondary structure characterization, and polymer characterization. First, the fundamental attributes of this approach and the resulting information elucidated are investigated. Using this approach CID product ions are dispersed in two-dimensions, specifically size-to-charge (IM) and mass-to-charge (MS), and the resulting 2-D data display greatly facilitates the top-down information contents; (i) charge state specific trand lines, (ii) increased dynamic range, (iii) separation of overlapping ion signals. The increase in peak capacity allows for detection of low abundant fragment ions providing an increase in the primary sequence coverage and the confidence of ion assignments as demonstrated by melittin and ubiquitin. Second, this general approach is applied to the top-down analysis for a variety of applications. MS-CID-IM-MS is used for the structural characterization of disulfide linked protein ions by monitoring the ATD of the ion pre- and post-collisional activation. Similarly, this approach can also be used to distinguish product ion type as well as, in some cases, specific secondary structural elements, viz. extended coils or helices providing rapid identification of the onset and termination of extended coil structure in peptides as demonstrated by insulin B-chain. Detect of low abundant ion signals associated with cross-ring cleavages allows this approach to be extended to determine regiochemistry of glucose derived polymers. As demonstrated, the MS-CID-IM-MS approach is highly versatile owing to the information content gained upon dispersion of ions in two-dimensions, providing an effective increase in experimental dynamic range as well as providing conformational information.