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Ambient Ionization - Mass Spectrometry: Advances Toward Intrasurgical Cancer Detection, Alan Keith Jarmusch

Open Access Dissertations

My dissertation research has focused on the development of ambient ionization – mass spectrometry (MS) for clinical measurements, specifically intrasurgical cancer detection. The molecular differences between normal and cancerous tissue were detected via direct tissue analysis in vitro by touch spray ionization (TS) or by analyzing sectioned or smeared tissue using desorption electrospray ionization (DESI). The physical form of the tissue, e.g. in vitro sampling, sectioned, or smeared, was inconsequential in differentiating normal from cancerous tissue; however, the spectra acquired by TS and DESI differed due to differences in ionization processes. We envision that TS-MS and DESI-MS could impact diagnostic …

A Framework For The Statistical Analysis Of Mass Spectrometry Imaging Experiments, Kyle Bemis

Open Access Dissertations

Mass spectrometry (MS) imaging is a powerful investigation technique for a wide range of biological applications such as molecular histology of tissue, whole body sections, and bacterial films , and biomedical applications such as cancer diagnosis. MS imaging visualizes the spatial distribution of molecular ions in a sample by repeatedly collecting mass spectra across its surface, resulting in complex, high-dimensional imaging datasets. Two of the primary goals of statistical analysis of MS imaging experiments are classification (for supervised experiments), i.e. assigning pixels to pre-defined classes based on their spectral profiles, and segmentation (for unsupervised experiments), i.e. assigning pixels to newly …

Preparative Mass Spectrometry Applications In Nanomaterials And Organic Synthesis, Michael Wleklinski

Open Access Dissertations

Preparative mass spectrometry was traditionally a vacuum based experiment where mass selected ion beams were deposited onto surfaces; however, recently ions have been manipulated in the open air to perform accelerated synthesis. The work of this dissertation focuses on the generation of charged ions from microdroplets and their use in organic synthesis and the preparation of atomically precise metal nanoclusters. First the mechanism for charging in the zero volt paper spray will be presented. This works builds a computational model based on the statistical fluctuation of positive and negative charges based on the theory of Dodd. It is found through …

Mass Spectrometric Characterization Of Remotely Charged Amino Acids And Peptides, Damodar Koirala

Open Access Dissertations

Ion–molecule reactions in a flowing afterglow are used to examine the electronic structure of 3- and 4-pyridinylnitrene-n-oxide radical anions. Reactions with nitric oxide are generally similar to those reported previously for other aromatic nitrene radical anions. In particular, phenoxide formation by nitrogen–oxygen exchange is observed with both isomers. Oxygen atom abstraction by NO is also observed with both isomers. Very significant differences in the reactivity are observed in the reactions of the two isomers with carbon disulfide. The reactivity of the 3-noxide isomer with CS2 is similar to that observed previously for nitrene radical anions, and reactions of the n-oxide …

Fast-Pyrolysis Of Biomass Related Model Compounds: A Novel Approach To Experimental Study And Modeling, John Charles Degenstein

Open Access Dissertations

Fast pyrolysis is a potentially attractive method for converting biomass to a low energy-density liquid (bio-oil) that can be further upgraded for use as fuel. Currently there is no agreement concerning the reaction pathways and mechanisms for pyrolysis of any individual component of biomass. This information is important for optimization of the fast-pyrolysis process. The work was divided into four areas, 1--development and validation of analytical methods and reactors, 2--the utilization of these methods to study pyrolysis of biomass and related models, 3--use of available biomass conversion pathways to propose potential integration with the existing fuel and chemicals markets, and …

Signal Enhancement And Data Mining For Biological And Chemical Samples Using Mass Spectrometry, Yuezhi Du

Open Access Dissertations

Mass spectrometry has been actively involved in the areas of healthcare, pharmaceutics, environmental analysis, food industry and forensics due to its ability to provide molecular information at trace levels. Recently, because of the complexity of chemical and biological samples, computer-assisted mass spectra analysis, including signal enhancement, statistics and machine learning, has been drawn more and more attention especially for researches in biomarker identification, sample classification and omics-related areas where high volume of data is generated.

Miniature Mass Spectrometer System With A Sampling Probe, Chien-Hsun Chen

Open Access Dissertations

This thesis focuses on the development of miniature mass spectrometry systems and the sampling probes. Mass spectrometers are usually installed and used in the analytical laboratory. It requires complex sample preparation before the analysis. Use of miniature mass spectrometer enables the chemical analysis outside the lab and a sampling probe provides convenience for real-time analysis. Two miniature mass spectrometer systems have been developed in this work.

Mass Spectrometric Studies On Petroleum Asphaltenes And Organosulfur Compounds, On Functional-Group Selective Ion-Molecule Reactions And On Gas-Phase Reactivity Of Meta-Benzynes Toward Amino Acids, Weijuan Tang

Open Access Dissertations

Mass spectrometry has found a wide variety of applications in many fields of study, such as fundamental chemistry, biological science, food and fuels, advanced materials, etc. Due to its high sensitivity, selectivity and speed, mass spectrometry provides an invaluable tool for direct mixture analysis. When coupled with separation methods, such as gas chromatography or high performance liquid chromatography, analysis of minor components in complex mixtures is possible. In addition to the molecular weight information, mass spectrometers can provide structural information for the ionized analyte molecules. However, mass spectrometric analysis of complex mixtures is not without challenges, such as suitable evaporation/ionization …

Instrumentation, Applications And Fundamentals Of Plasma Ionization Of Organic Molecules From Surfaces, Joshua Scott Wiley

Open Access Dissertations

Various aspects of the interaction of low-temperature plasma (LTP) ambient ionization with organic molecules and surfaces are discussed. As an application, LTP-MS has been used for the analysis of pesticides directly from fruits and vegetables revealing low parts per billion limits of detection (LODs). Due to low power and gas requirements, a battery-operated and handheld LTP probe was developed for the point-and-shoot MS analyses. Handheld LTP was compared with large-scale LTP on a benchtop and miniature MS revealing similar LODs for both. Long-distance ion transport up to one meter was also demonstrated with flexible tubing for non-proximate sample interrogation. Fundamentals …

Gas-Phase Covalent And Non-Covalent Ion/Ion Chemistry Of Biological Macromolecules, John Robert Stutzman

Open Access Dissertations

Gas-phase ion/ion chemistry involves the interaction of oppositely charged ions inside of the mass spectrometer. During this gas-phase chemistry, particle transfer (i.e., proton and electron) or synthesis can occur at rapid reaction rates. Particle transfer represents a mature area of ion/ion chemistry, while selective covalent modification represents a fairly new area of gas-phase chemistry. Gas-phase covalent chemistry is based on traditional solution phase organic chemistry.

The work demonstrated in this dissertation greatly involves gas-phase covalent and non-covalent Schiff base chemistry on peptide and protein ions. The reagent dianion, 4-formyl 1,3-benzene disulfonic acid, has been used to covalently modify unprotonated primary …

Top-Down Interrogation And Characterization Of Biological Macromolecules, Yang Gao

Open Access Dissertations

Analytical mass spectrometry has been widely applied in the field of biomolecule identification and characterization. It provides fast, accurate and robust information relevant to the molecular mass, composition and structure of the target analytes.

This thesis is focused on the top-down analysis of various macrobiomolecules, nucleic acids and proteins, in the context of ion/ion reaction and gas-phase unimolecular dissociation. The first part of the thesis deals with gas phase fragmentation behavior of chemically modified oligonucleotides. Factors, such as the observation time-scale, the ion type and the energy deposition method, are explored using a quadrupole/time-of-flight mass spectrometer. Novel fragmentation pathway associated …

Mass Spectrometric Studies On The Primary Products Of Fast Pyrolysis Of Carbohydrates And The Molecular Structures Of Asphaltenes, And The Development Of A Rastering Probe For Laser-Induced Acoustic Desorption Into An Atmospheric Pressure Chemical Ionization Source, Matthew Robert Hurt

Open Access Dissertations

Mass spectrometry (MS) has proven invaluable in the field of mixture analysis and structural elucidation. Tandem mass spectrometry (MS/MS) utilizing collision-activated dissociation (CAD) has become the technique of choice for structural elucidation of unknown analytes in mixtures. When coupled with gas chromatography (GC) or high performance liquid chromatography (HPLC), it allows for trace level analysis of mixture components. In spite of the utility of mass spectrometry in complex mixture analysis, it does have limitations. Traditional GC/MS methods used for the analysis of fast pyrolysis products cannot be used to analyze the primary products, thus limiting the knowledge that can be …

Structural Analysis Of Carbohydrates By Mass Spectrometry, Chiharu Konda

Open Access Dissertations

Protein glycosylation is a highly frequent post-translational modification. Glycosylation is actively involved in intermolecular and intercellular binding events that are important to a wide range of biological functions such as immunity and fertility. The unique functions of glycans are directly related to their structures. In order to fully characterize the structure of an unknown glycan, 5 levels of structural information is needed: sugar unit identity, anomeric configuration, linkage types, sequence, and branching location. One of the grand challenges limiting the advance of glycosciences is the lack of sensitive tools for detailed glycan structural analysis. Tandem mass spectrometry (MS/MS) is a …

Development Of A Field-Portable Miniature Mass Spectrometer Designed For In-Situ Analysis And Ion Trap Miniaturization, Paul Isaac Hendricks

Open Access Dissertations

Chemical analysis by mass spectrometry has become the gold standard due to the sensitivity, selectivity, and short analysis times that are afforded by the method. Advances in miniaturized vacuum systems, mass analyzers, electronics, and ionization sources have allowed for the development of field-portable mass spectrometers. The performance of portable instruments has received much attention for their utility in the detection of illicit drugs, explosives, environmental contaminants, therapeutic drugs, and more recently, biological tissues. Furthermore, detection of the aforementioned compounds can be completed at atmospheric pressures and in the presence of complex matrices and sample surfaces when used in conjunction with …