Open Access. Powered by Scholars. Published by Universities.®
- Institution
- Publication
- Publication Type
Articles 1 - 10 of 10
Full-Text Articles in Chemistry
Protein Stability In Solution And In The Gas Phase., Yousef Haidar
Protein Stability In Solution And In The Gas Phase., Yousef Haidar
Electronic Thesis and Dissertation Repository
Electrospray Ionization mass spectrometry (ESI-MS) is widely used for probing proteins, yet many aspects of this technique remain elusive. Using MS, ion mobility spectrometry (IMS), and circular dichroism (CD) spectroscopy, this thesis sheds light on the stability differences of proteins in the gas phase and solution. After a general introduction (Chapter 1), Chapter 2 scrutinizes some aspects of native ESI. Our data highlight the significance of cone voltage in maintaining a native-like fold and show the advantage of using NH4Ac in protein experiments. Chapter 3 focuses on hydrogen/deuterium exchange (HDX)-MS. Several studies have reported that D2O …
Investigating The Rotary Mechanism Of Atp Synthase Using Molecular Dynamics Simulations, Angela Marcela Murcia Rios
Investigating The Rotary Mechanism Of Atp Synthase Using Molecular Dynamics Simulations, Angela Marcela Murcia Rios
Electronic Thesis and Dissertation Repository
F1-ATPase is a motor protein that can use ATP hydrolysis to drive rotation of the central subunit. The γ C-terminal helix constitutes of the rotor tip that is seated in an apical bearing formed by the α3β3 head. It remains uncertain to what extent the γ conformation during rotation differs from that seen in rigid crystal structures. Existing models assume that the entire γ subunit participates in every rotation. Here we develop a molecular dynamics (MD) strategy to model the off-axis forces acting on γ in F1-ATPase. MD runs showed stalling of the …
Roaming Transition States And Highly Accurate Thermochemistry: A Pepico Study Of Two Small Combustion Systems, Kyle John Covert
Roaming Transition States And Highly Accurate Thermochemistry: A Pepico Study Of Two Small Combustion Systems, Kyle John Covert
University of the Pacific Theses and Dissertations
Two small combustion systems, methyl hydroperoxide (CH3OOH) and 2-propanol ((CH3)2CHOH), were studied using imaging photoelectron photoion coincidence spectroscopy (iPEPICO), which combines photoelectron spectroscopy and photoionization mass spectrometry to detect coincident photoelectron-photoion pairs. In the photon energy range of 11.4–14.0 eV, energy selected CH3OOH+ ions dissociate into CH2OOH+, HCO+, CH3+, and H3O+ ions. The lowest-energy dissociation channel is the formation of the cation of the smallest “QOOH” radical, CH2OOH+. A statistical rate model fitted to the …
I3: Isomerization Of Isomer Ions, Krisztián Gabor Torma
I3: Isomerization Of Isomer Ions, Krisztián Gabor Torma
University of the Pacific Theses and Dissertations
Photoelectron Photoion Coincidence (PEPICO) spectroscopy is a robust tool for elucidating complex unimolecular dissociation mechanisms and for determining thermochemical and kinetic data of gas-phase ion dissociations with high accuracy. In this work, the dissociative photoionization of two sets of isomeric systems were analyzed with PEPICO: 1) C7H7+ ions of toluene (Tol) and 1,3,5-cycloheptatriene (CHT), and 2) two butyl alcohol isomers, 1-butanol and isobutanol. Threshold dissociative photoionization data on these four molecules of interest were collected on the imaging PEPICO apparatus at the VUV beamline of the Swiss Light Source. Data analysis was aided by ab initio calculations and Rice-Ramsperger-Kassel-Marcus (RRKM) …
Photofragment Imaging Fast Ion Beams, Michael D. Johnston Jr.
Photofragment Imaging Fast Ion Beams, Michael D. Johnston Jr.
Doctoral Dissertations
Metal-containing ions have been the subject of much research due to their roles in catalytic activation and small cluster chemistries. However, they can be difficult to study both experimentally and theoretically, and new approaches are needed. The goal of the research described here is to characterize the electronic structures and thermodynamics of metal-containing ions using gas-phase spectroscopy experiments performed on a powerful new instrument. Presented in the following chapters are the details of a recently built velocity map imaging mass spectrometer that is capable of imaging the photofragments of trap-cooled (≥7K) ions produced in a versatile ion source. This instrument …
Using In Situ Liquid Single Photon Ionization Mass Spectrometry (Spi-Ms) To Probe Lithium Polysulfide Electrolyte In Motion, Aala M. Al Hasan, Jiachao Yu, Juan Yao, Vijayakumar Murugesan, Manjula Nandasiri, Xiao-Ying Yu
Using In Situ Liquid Single Photon Ionization Mass Spectrometry (Spi-Ms) To Probe Lithium Polysulfide Electrolyte In Motion, Aala M. Al Hasan, Jiachao Yu, Juan Yao, Vijayakumar Murugesan, Manjula Nandasiri, Xiao-Ying Yu
STAR Program Research Presentations
The solid-liquid (s-l) interface is the most common interface encountered in electrochemical systems. The s-l interface has wide applications in energy storage, catalysis, and material sciences. In situ studies of chemical reactions taking place on the s-l interfaces can further our understanding of electron transfer and link to real-world device functions under challenging conditions. Direct probing of the solid electrode and liquid electrolyte interface has been realized using a vacuum compatible electrochemical microfluidic reactor, system for analysis at the liquid vacuum interface (SALVI) with time-of-flight secondary ion mass spectrometry (ToF-SIMS). Most recently, the electrochemical version of SALVI was integrated to …
Interactions Of The Naphthalene Radical Cation With Polar And Unsaturated Molecules In The Gas Phase, Sean P. Platt
Interactions Of The Naphthalene Radical Cation With Polar And Unsaturated Molecules In The Gas Phase, Sean P. Platt
Theses and Dissertations
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 …
From Solution Into The Gas Phase: Studying Protein Hydrogen Exchange And Electrospray Ionization Using Molecular Dynamics Simulation, Robert G. Mcallister
From Solution Into The Gas Phase: Studying Protein Hydrogen Exchange And Electrospray Ionization Using Molecular Dynamics Simulation, Robert G. Mcallister
Electronic Thesis and Dissertation Repository
Here, we apply Molecular Dynamics (MD) simulations to investigate fundamental aspects of structural mass spectrometry (MS). We first examine microscopic phenomena underlying Hydrogen/Deuterium exchange (HDX). HDX interrogates structural dynamics of proteins by measuring the rate of Deuterium uptake into backbone amides. We perform microsecond MD simulations on ubiquitin to investigate this process. We find that HDX protection often cannot be explained by H‑bonding or solvent accessibility considerations. These findings caution against non-critical use of HDX data in structural contexts. We next use MD to examine the Electrospray ionization (ESI) mechanism of proteins. ESI is a soft ionization technique resulting in …
Noncovalent Interactions Between Alkali Metal Cation And Aza/Thia-Crown Macrocycles: Mass Spectrometric Techniques And Theoretical Studies, Calvin A. Austin
Noncovalent Interactions Between Alkali Metal Cation And Aza/Thia-Crown Macrocycles: Mass Spectrometric Techniques And Theoretical Studies, Calvin A. Austin
Wayne State University Dissertations
Macrocyclic complexes have been useful in understanding many systems encountered in biology, along with having widespread use in analytical, pharmaceutical, and synthetic chemistry. My goal was to provide a quantitative experimental and theoretical description of cation-aza-crown and thia-crown ether interactions with alkali metal cations. Infrared multiple photon dissociation (IRMPD) action spectroscopy and energy-resolved collision-induced dissociation (CID) techniques were used in conjunction with theoretical electronic structure calculations to characterize the structures, binding interactions, and stability of cation-aza-crown ether interactions. Quantum chemical calculations at several levels of theory were employed to characterize the structures and stabilities of the isolated cations and aza-crown …
Synthesis And Characterization Of Fullerene-Based Hydrogen Storage Materials, Patrick Alan Ward
Synthesis And Characterization Of Fullerene-Based Hydrogen Storage Materials, Patrick Alan Ward
Doctoral Dissertations
Storing hydrogen safely and efficiently is an area of great interest for the utilization of hydrogen as an energy carrier in transportation applications. The feasibility of using fullerenes in hydrogen storage materials was investigated. Alkali decorated fullerenes LixC60 [LixC60] and NaxC60 [NaxC60] were found to enhance the hydrogen chemisorption and physisorption properties of fullerenes. Although the overall hydrogen physisorption uptake in these materials is low due to the crystalline nature of the material, the isosteric heats of adsorption of fullerenes were increased by lithium doping. C60 [C60] is also capable of acting as …