Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 15 of 15
Full-Text Articles in Entire DC Network
Mass Spectrometric Characterization Of Peptide Radical Ions And Implication For Radical Chemistry, Lei Tan
Mass Spectrometric Characterization Of Peptide Radical Ions And Implication For Radical Chemistry, Lei Tan
Open Access Dissertations
Gas-phase radical ion chemistry has attracted increasing research interest from the mass spectrometry (MS) society because it provides new capabilities in bio-analysis which often complements traditional MS methods developed from even-electron ions. Fundamental studies of biomolecule related radical species are essential to broadening the scope of radical chemistry and pushing the frontiers of its analytical applications. This dissertation mainly discusses the gas-phase chemistry of peptide sulfinyl radicals (-SO·), which has been rarely studied before. In order to establish an effective research approach, a method that can generate site-specific peptide sulfinyl radical ion has been developed. This method is based on …
Effect Of Maleic Acid On The Selectivity Of Glucose And Fructose Dehydration And Degradation, Ximing Zhang
Effect Of Maleic Acid On The Selectivity Of Glucose And Fructose Dehydration And Degradation, Ximing Zhang
Open Access Dissertations
5-Hydroxymethyfurfural (HMF), a platform chemical can upgrade to a variety of fuels and polymers, can be manufactured from lignocellulose. This study focuses on the Lewis and Brønsted acid effect on hexose dehydration for HMF production. We report the positive effect of maleic acid, a dicarboxylic acid used as Brønsted acid, on the selectivity of hexose dehydration to 5-hydroxymethyfurfural (HMF), and subsequent hydrolysis to levulinic and formic acids. We also describe the kinetic analysis of a Lewis acid (AlCl 3) alone and in combination with HCl or maleic acid to catalyze the isomerization of glucose to fructose, dehydration of fructose …
Studies Of Arctic Halogen Chemistry From The Snowpack To The Gas Phase, Kyle D Custard
Studies Of Arctic Halogen Chemistry From The Snowpack To The Gas Phase, Kyle D Custard
Open Access Dissertations
The temporary depletion of both tropospheric ozone and gaseous mercury during the Arctic springtime has been a focus of active research over the past several decades. Both of these phenomena have been linked to chemical reactions with halogen radicals. In particular, bromine atoms have been shown to act as the primary driver for these chemical depletions, although both chlorine and iodine atoms also contribute. Molecular bromine, along with its oxidation products, have been well studied in the Arctic, yet chlorine has not. Chlorine is known to impact the local oxidation capacity via its high reactivity with volatile organic compounds. Despite …
Novel Methods For Manipulating Ion Types In The Solution And Gas Phases For The Structural Analysis Of Biomolecules Using Mass Spectrometry, Christine M Fisher
Novel Methods For Manipulating Ion Types In The Solution And Gas Phases For The Structural Analysis Of Biomolecules Using Mass Spectrometry, Christine M Fisher
Open Access Dissertations
Mass Spectrometry has become a valuable tool for the analysis of a variety of molecules, making it applicable to many fields. The advent of nanoelectrospray ionization (nESI) as a soft/low energy ionization technique has enabled the analysis of large, intact biomolecules. Most mass spectrometry experiments consist of three main steps: ionization, probe step(s), and mass analysis. The present work focuses on a variety of methods for altering ion types at various stages of the mass spectrometry experiment to affect ion fragmentation. Ion types can be manipulated in the solution/droplet phases using novel nESI emitters, generated from borosilicate theta capillaries. These …
Public Understanding Of Chemistry Research In Print News, Michael D. Hands
Public Understanding Of Chemistry Research In Print News, Michael D. Hands
Open Access Dissertations
Despite numerous calls for improving scientific literacy, many American adults show a lack of understanding of experiments, scientific study, and scientific inquiry. News media is one important avenue for science learning, but previous research investigating health and/or environmental science news has shown that it is inconsistent in the presentation of scientific research limitations, potentially impacting reader understanding. In the first phase of this dissertation, seventeen news articles reporting on a single chemistry research article, along with associated press releases and research articles, were analyzed using move analysis to determine the structure of each type of text. It was found that …
Polarization-Dependent Nonlinear Optical Microscopy Methods For The Analysis Of Crystals And Biological Tissues, Emma L. Kerian
Polarization-Dependent Nonlinear Optical Microscopy Methods For The Analysis Of Crystals And Biological Tissues, Emma L. Kerian
Open Access Dissertations
The ability to solve a high-resolution protein structure is largely dependent on the successful generation and identification of protein crystals prior to X-ray diffraction (XRD). For novel protein targets, high-throughput crystallography often involves generation of multiple targets and thousands of crystallization trials per target to generate diffraction-quality crystals. Second harmonic generation (SHG) imaging has been developed as a fast, non-destructive and sensitive method for the selective identification of protein crystals, even in highly scattering environments. Polarization-dependent SHG microscopy methods were developed to assess the presence of multidomain crystals to provide a handle on crystal quality. In addition, polarization-dependent two-photon excited …
Development Of Experimental And Instrumental Systems To Study Biological Systems, Amanda J Hemphill
Development Of Experimental And Instrumental Systems To Study Biological Systems, Amanda J Hemphill
Open Access Dissertations
Chapters 1-4 of this thesis describes the development of an experimental system to measure diffusion-limited reaction kinetics in a biological environment. About 100 years ago, the relationship between reaction rate and diffusion in homogenous solution, ie water or buffer, was described as a linear relationship by Smoluchowski. Applying this theory naively would suggest that since the diffusion coefficients drop by factors of 4-100 then the rates of reaction would drop by the same amount. However, recent theory and simulations suggest that this does not hold. Even though biological diffusion coefficients drop to 0.1-20% of that in buffer, these recent studies …
Molecular Diagnosis Of Cancer Using Ambient Ionization Mass Spectrometry, Kevin S Kerian
Molecular Diagnosis Of Cancer Using Ambient Ionization Mass Spectrometry, Kevin S Kerian
Open Access Dissertations
My dissertation focuses on advancing the development and application of ambient ionization mass spectrometry methodology and technology to the biomedical field. The primary ambient ionization method used in my studies is desorption electrospray ionization mass spectrometry (DESI-MS) imaging, which has been previously used to analyze and differentiate disease state (i.e. tumor and normal) and in some cases tumor subtype of human liver, kidney, bladder, testicular, prostate, and brain cancers. DESI-MS imaging is an ideal method for disease diagnosis, because it can be used to directly correlate disease state with histopathology to develop and validate MS libraries built using the molecular …
Studies Of The Interaction Of Biogenic Volatile Organic Compounds And Nox In Forest Environments, Kevin M. Mcavey
Studies Of The Interaction Of Biogenic Volatile Organic Compounds And Nox In Forest Environments, Kevin M. Mcavey
Open Access Dissertations
Ozone is a pollutant that causes crop damage, adverse health effects, and is a contributor to global climate change. Ozone concentrations are predicted to rise over the next half-century along with global temperature. Ozone production is controlled by the chemistry between biogenic volatile organic compounds and NOx (NO + NO2), and therefore, a greater understanding of NOx + BVOC chemistry along with their sources and sinks is needed. One large uncertainty in understanding NOx + BVOC chemistry is the production of organic nitrates (RONO2), which act as a radical termination step in the …
Spectroscopic Characterization And Photochemistry Of Nitrogen-Containing Molecules Relevant To Titan's Atmosphere, Deepali N. Mehta-Hurt
Spectroscopic Characterization And Photochemistry Of Nitrogen-Containing Molecules Relevant To Titan's Atmosphere, Deepali N. Mehta-Hurt
Open Access Dissertations
Titan's atmospheric chemistry has been the source of intrigue since the planetary body's discovery. Though there is a growing understanding of the atmospheric chemistry of small molecules on Titan, much less is known about larger molecule formation, and particularly about nitrile chemistry. This dissertation characterizes nitrile/isonitrile intermediates that are postulated to be important in Titan's atmosphere, adding to the necessary foundation for understanding Titan's atmospheric chemistry. The vibronic spectroscopy of para-diisocyanobenzene (pDIB, C≡N-Ph-N≡C) has been characterized as a first step towards photochemical studies that can test the transformation of the isonitrile group to other nitrogen-based functionalities.p …
Quantification Of Molecular Aggregation Equilibria Using Spectroscopic Measurements And Random Mixing Modeling, Blake M. Rankin
Quantification Of Molecular Aggregation Equilibria Using Spectroscopic Measurements And Random Mixing Modeling, Blake M. Rankin
Open Access Dissertations
Molecular aggregation equilibria, such as the binding of ligands to a central solute molecule, are prevalent throughout biological processes and energy storage devices. However, both the sign and magnitude of hydrophobic and ionic interactions remains a subject of theoretical debate, and has yet to be experimentally determined. Here, Raman vibrational spectroscopy is combined with multivariate curve resolution (Raman-MCR) to experimentally quantify both the number of hydrophobic contacts between alcohol molecules in water and the affinity of ions for molecular hydrophobic interfaces. Furthermore, a generalized theoretical model is developed based on random statistics in which it is assumed that the concentration …
Laboratory Studies On The Production Of Alpha-Pinene-Derived Organic Nitrates And Their Atmospheric Fate, Joel David Rindelaub
Laboratory Studies On The Production Of Alpha-Pinene-Derived Organic Nitrates And Their Atmospheric Fate, Joel David Rindelaub
Open Access Dissertations
Currently, the formation yields of organic nitrates from the oxidation of biogenic volatile organic compounds, such as α-pinene, is highly uncertain, negatively impacting our knowledge on tropospheric ozone production and the fate of atmospheric NOx. To lower this uncertainty, we quantified the organic nitrate yield from the OH radical oxidation of α-pinene under high NOx conditions. The α-pinene- derived nitrates created in chamber experiments readily partitioned to the aerosol phase and underwent particle phase hydrolysis, indicating that these processes are likely a sink for atmospheric NOx. The hydrolysis of organic nitrates was found to be …
Homogeneous And Heterogeneous Rhenium Catalysts For Sustainable Transformations Of Polyols, Alcohols, And Amines, Jing Yi
Open Access Dissertations
Biomass-derived molecules, such as sugar polyols and lignin, are promising feedstock for making small and useful organics (SUO) and high value-added organics (HVO). However, the high oxygen to carbon ratio (C:O ≈ 1) prohibits the direct use of biomass-derived molecules as energy carriers and chemicals. Deoxygenation of polyols has become an important challenge in the utilization of biomass resources. Oxorhenium complexes show excellent oxophilicity to transfer oxygen and deoxygenate alcohols. Oxorhenium(VII) complexes can efficiently catalyze the transformation of glycerol to allyl alcohol, acrolein, and propanal. The volatile SUO products were easily separated from the nonvolatile residues via simple distillation. Based …
Structure-Activity Relationships For The Water-Gas Shift Reaction Over Supported Metal Catalysts, Kaiwalya D. Sabnis
Structure-Activity Relationships For The Water-Gas Shift Reaction Over Supported Metal Catalysts, Kaiwalya D. Sabnis
Open Access Dissertations
The Water-Gas Shift (WGS) reaction (CO + H2O → CO2 + H2) is an important chemical process for industrial hydrogen production. The overall goal of this project is to use kinetic experiments and in situ characterization techniques in tandem, in order to derive structure-activity relationships for various catalytic systems. These relationships facilitate the rational catalyst design by identification of catalyst descriptors. In order to establish such relationships, various studies were undertaken, such as (i) effect of transition admetals on the WGS catalysis by molybdenum carbide (ii) effect of residual oxygen content on the performance of …
Instrumentation And Development Of A Mass Spectrometry System For The Study Of Gas-Phase Biomolecular Ion Reactions, Ziqing Lin
Open Access Dissertations
Gas-phase reactions of biomolecular ions are highly relevant to the understanding of structures and functions of the biomolecules. Mass spectrometry is a powerful tool in investigating gas-phase ion chemistry. Various mass spectrometers have been developed to explore ion/molecule reactions, ion/ion reactions, ion/photon reactions, ion/radical reactions etc., both at atmospheric pressure and in vacuum. In-vacuum reactions have an advantage of involving pre-selecting the ions for the reactions using a mass analyzer. Over the decades, a variety of mass analyzers have been employed in the research of ion chemistry. Hybrid configurations, such as quadrupole ion trap with a time-of-flight and or a …