Chemistry & Biochemistry Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/2752

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Subject: search.filters.subject.Mass Spectrometry

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    Development of single-neuron proteomics by mass spectrometry for the mammalian brain.
    (2021) Choi, Bok Dong; Nemes, Peter; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Single-neuron proteomics holds the potential to advance our understanding of important biological processes during neuron maturation and development. However, to characterize proteins from single neurons, further technological advances are still required. This dissertation discusses the development and application of single-cell mass spectrometry (MS) technologies to investigate proteins and its role in different neurons. The work presented herein demonstrates the strategies to develop and advance single-neuron analysis using capillary electrophoresis (CE)-MS. In addition, this work features several contributions to our understanding of neuron-to-neuron heterogeneity, providing new information to advance cell biology and neuroscience.
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    Understanding the Relationships Between Architecture, Chemistry, and Energy Release of Energetic Nanocomposites
    (2017) DeLisio, Jeffery Brandon; Zachariah, Michael R; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Energetic nanocomposites are a class of reactive material that incorporate nanosized materials or features in order to enhance reaction kinetics and energy densities. Typically, these systems employ metal nanoparticles as the fuel source and have demonstrated reactivities orders of magnitude larger than more traditionally used micron-sized metal fuels. One drawback of using nanosized metals is that the nascent oxide shell comprises a significant weight percent as the particle size decreases. This shell also complicates the understanding of oxidation mechanisms of nanosized metal fuels. In this dissertation, I apply a two-fold approach to understanding the relationships between architecture, chemistry, and energy release of energetic nanocomposites by 1) investigating alternative metal fuels to develop a deeper understanding of the reaction mechanisms of energetic nanocomposites and 2) creating unique microstructures to tailor macroscopic properties allowing for customizability of energetic performance. In order to accurately study these systems, new analytical techniques capable of high heating rate analysis were developed. The oxidation mechanisms of tantalum nanoparticles was first probed using high heating rate TEM and Temperature-Jump Time-of-Flight Mass Spectrometry (T-Jump TOFMS) and shell crystallization was found to plan an important role in the mechanism. An air-sensitive sample holder was developed and employed to analyze the decomposition and oxidation of molecular aluminum compounds, which theoretically can achieve similar energy release rates to monomolecular explosives in addition to much higher energy densities. In order to obtain simultaneous thermal and speciation data at high heating rates, a nanocalorimeter was integrated into the TOFMS system and measurements were performed on Al/CuO nanolaminates to probe the effect of bilayer thickness on energy release. An electrospray based approach to creating energetic nanocomposites with tunable architectures is also described. An in depth study on the electrospray synthesized nAl/PVDF thin film reaction mechanism was performed using T-Jump TOFMS. The nAl/PVDF system was also studied using a Molecular Beam Sampling Time-of-Flight Mass Spectrometer designed and built primarily to investigate the reaction mechanisms of energetic nanocomposites at 1 atm in both aerobic and anaerobic environments.
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    Lanthanoid Isotopic Composition of Pre and Post-Detonation Nuclear Material
    (2014) Sharp, Nicholas Eugene; Mignerey, Alice C; McDonough, William F; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Analysis of lanthanoid isotopic composition of pre and post-nuclear detonation materials provides information on the type of device, origin of fissile material, and in the case of spent nuclear fuel, the operating history of the reactor. Prior to analysis, the lanthanoids must be separated from bulk materials to reduce exposure to harmful radiation and to remove isobaric interferences. Trinitite and spent nuclear fuel rods are appropriate analogues for post and pre-detonation nuclear materials, respectively. Compositional analysis of trinitite glass, fused silicate material produced by the Trinity test, reveal non-normal Nd isotope composition, with deviations of -1.66 ± 0.48 e; (differences in parts in 104) in 142Nd/144Nd, +2.24 ± 0.32 e; in 145Nd/144Nd, and +1.00 ± 0.66 e; in 148Nd/144Nd (2σ) relative to natural reference materials. Greater isotopic deviations are found in Gd, with enrichments of +4.28 ± 0.72 e; in 155Gd/160Gd, +4.19 ± 0.56 e; in 156Gd/160Gd, and +3.59 ± 0.37 e; in 158Gd/160Gd. The isotopic deviations are consistent with a 239Pu based fission device with additional 235U fission contribution and a thermal neutron fluence between 0.97 and 1.4 x 1015 neutrons/cm2. Separation and analysis of spent nuclear material is a difficult challenge in both logistics and sample handling. Lanthanoids were removed from the bulk spent nuclear fuel at Savannah River National Laboratories, while the separation of Gd, Sm and Nd was carried out at the University of Maryland. The isotopic composition of Nd and Sm were compared to predicted values calculated using two programs that were developed for modeling the burning cycle of traditional power-reactors: Oak Ridge Isotope GENeration (ORIGEN-S) and Monte Carlo N-particle transport code (MONTEBURNS). The isotopic composition of Nd agreed with predicted values within 10% with the exception of 142Nd, while only 150Sm had agreement within 10% of prediction. These results show that the typical calculation codes are not adequately modeling the intense neutron flux present in research reactors, and further work will need to be done before source reactors can be identified using reverse modeling algorithms.
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    Methods and Standards for the Analysis and Imaging of Latent Fingerprints and Trace Contraband using Ambient Ionization Mass Spectrometry and Secondary Ion Mass Spectrometry
    (2014) Sisco, Edward; Mignerey, Alice C; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A recent report from the National Academy of Sciences (NAS), evaluating the state of forensic science, identified the need to more rapidly, accurately, and reproducibly provide scientifically validated forensic analyses of evidence to support the criminal justice system. The NAS report also highlighted the need for the forensic science community to collaborate with universities and national laboratories, as well as to forge relationships with the National Institute of Standards and Technology (NIST) to address method development, validation, and evaluation of new analytical techniques of relevance to forensic science. This thesis was completed as part of a unique collaboration between the University of Maryland (UM), the National Institutes of Standards and Technology (NIST) and the Defense Forensic Science Center (DFSC) to address several of the existing research needs in current forensic science practice while meeting the requirements for a Department of Defense (DOD) Science Mathematics and Research for Transformation (SMART) fellowship and supporting NIST efforts in trace contraband detection. Two distinct areas of research were pursued. First, studies were conducted on method development and validation for the detection of explosives using four different ambient ionization mass spectrometry (AI-MS) techniques relevant to routine casework at DFSC and to other federal labs that screen for trace contraband. Additional method validation studies for the detection of adulterants in beverages and the analysis of bank dye are also presented. All methods were developed in accordance with the requirements specified by the International Organization of Standardization (ISO) 17025 guidelines, which is the accreditation standard for practicing forensic laboratories. The second track of this thesis involved exploration of emerging analytical methods, and several novel applications, for mass spectrometry based chemical imaging of both endogenous and exogenous components in latent fingerprints. This work was driven by a recent National Science Foundation (NSF) report that identified mass spectral imaging (MSI) as a key goal for the future development of forensic science. Both AI-MS and secondary ion mass spectrometry (SIMS) techniques were utilized and evaluated for their ability to chemically image fingerprints. To support these studies, a novel standard fingerprint test material was also developed during this research. As a result of this work there are now validated methods for the screening of trace explosives, as well as other types of forensic evidence such as adulterants and bank dye, that can be reliably employed into the casework scheme. Also, there are new applications and capabilities for MSI of fingerprints and an artificial fingerprint material that allows for the reproducible deposition of test fingerprints.
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    EVALUATION OF MASS FILTERED, TIME DILATED, TIME-OF-FLIGHT MASS SPECTROMETRY
    (2010) Demoranville, Leonard Thomas; Mignerey, Alice C; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The Naval Research Laboratory's Trace Element Accelerator Mass Spectrometer (NRL-TEAMS) system offers a unique opportunity to develop a new type of time-of-flight (TOF) SIMS. This opportunity derives from use of a Pretzel magnet as a recombinator and mass filter in the injector to the accelerator. Mass filtering prior to time-of-flight analysis removes extraneous species, shortening the analysis time for a single beam pulse, thereby improving the duty cycle. Using this approach, it is possible to obtain an expanded portion of a narrow segment of the entire time-of-flight spectrum created by a single beam pulse. A longer flight path for greater momenta in the Pretzel magnet introduces time dilation. Potential benefits derived from time dilation and mass filtering include improved duty cycle, shorter analysis time, increased precision, and better resolution. While the NRL-TEAMS system is not designed for TOF work, it has been used as a test bed to prove the theoretical benefit of such a design. Theoretical treatments of the spectrometer have shown improved resolution is possible under certain conditions, when compared to a traditional TOF spectrometer. SIMION 8.0 computer simulations were used to model the system and provide insight to the theoretical capabilities of the Pretzel magnet. As expected, models have shown that as field decreases, and therefore path length increases, mass resolution improves. Generally, the model matched well to experimental results provided by the NRL TEAMS system. These experimental results have predicted fundamental parameters of the system accurately and consistently, and confirmed the validity of the model. This research improved the current system's performance through improved electronics and pulsing and further uses the model to predict the theoretical benefits of a system designed for use with a Pretzel magnet.
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    Mass Spectrometric Analysis of Cytoplasmic Ribosomal Proteins in Drug Resistant and Drug Susceptible Human Cell Lines
    (2006-05-30) Hays, Faith A; Fenselau, Catherine; Biochemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This study examines changes in cytoplasmic ribosomes that accompany drug resistance in MCF-7 breast cancer cells. Differences in ribosomal protein composition between drug susceptible and drug resistant cell lines were examined. Ribosomes were isolated from mitoxantrone susceptible and mitoxantrone resistant MCF-7 cells. The acid extracted ribosomal proteins were subjected to optimized 2DGE using a "zoom" strip (pI 7-11) for the first dimension separation. Further optimization of 2DGE included the use of a 15mM DTT wick at the cathode end of the focusing tray, decreasing the protein loading amount and using large format gels for the second dimension. Forty-nine ribosomal proteins were identified in the drug susceptible cell line. Two novel protein isoforms of the proteins RPS3 and one novel isoform of RPS10 were identified in the drug resistant cell line. Methods for the extraction and detection of ribosomal proteins from the 2D gel were developed. The method of Mirza et.al. was modified and used to extract ribosomal proteins from the gel. The detection of these proteins was optimized by the use of 50% ACN/1.0% TFA to solubilize the MALDI matrix. In addition, the extracted protein solution was mixed 1:1 with 5% Triton X-100. Intact molecular weights were determined for 41 ribosomal proteins using high performance MALDI-TOF mass spectrometry. The average number of ribosomes per cell was determined for the drug susceptible, as well as the drug resistant cell line, and found to be unchanged.