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A Mechanistic Investigation Of Cytochrome C Nitrite Reductase Catalyzed Reduction Of Nitrite To Ammonia: The Search For Catalytic Intermediates, Shahid Shahid

Theses and Dissertations

Cytochrome c Nitrite Reductase (ccNiR) is a periplasmic homodimeric decaheme enzyme that catalyzes the reduction of nitrite to ammonium in a process that involves six electrons and eight protons. Under standard assay conditions, which use a strong reducing agent as an electron source, catalysis takes place rapidly without producing detectable intermediates. However, intermediates do accumulate when weaker reducing agents are employed, allowing the ccNiR mechanism to be studied. Herein, the early stages of Shewanella oneidensis ccNiR-catalyzed nitrite reduction were investigated in isolation by using the weak reducing agents N,N,N’,N’-tetramethyl-p-phenylenediamine (TMPD) and the 2-electron reduced form of indigo trisulfonate. Experiments were …

Novel Approaches To The Determination Of Toxic Metals In Industrial Waste And Soil Extracts, Garrett Bruce Finn

Theses and Dissertations

Abstract:Because of their environmental impact, the contamination and migration of heavy metals is an important field of study. In this thesis, two novel methods for measuring toxic metals over a broad concentration range in complex matrices were successfully developed and applied to authentic samples. This research focused on toxic metals in two disparate environments: industrial effluent and soil. The primary work reported in this research focused on developing a Sequential Injection Analysis (SIA) process monitor to measure metals in industrial process waste streams in near real-time. Molecular Absorption Spectroscopy was used to determine levels of Zn and several other metals. …

Understanding Mechanochemical Processes On Surfaces Measured In Ultrahigh Vacuum, Resham Rana

Theses and Dissertations

Tribology is the study of friction and wear and of the energy dissipated when two surfaces slide against each other. A recent DOE report shows that improved lubricants could save ~103 exaJoules (1 exaJoule = 10^18 joules) per year, equivalent to 20% of the world’s total energy consumption. The focus of this work is to understand the surface chemistry and tribological reactions of model sulfur-, carbon-, and phosphorus-based lubricant additives to understand the mechanisms by which they operate. Previous work has shown that lubricant additives react by a novel mechanochemical process in which the force acting on the adsorbate accelerates …

Effect Of Force And Confinement On Chemical Reaction Kinetics, Alejandro Boscoboinik

Theses and Dissertations

This work studies model systems that are relevant to understanding the fundamentals of surface chemical processes. A Cu(100) single crystal surface modified by methyl thiolate species, formed from the adsorption of dimethyl disulfide, is used for modeling the effect of an external force in a chemical reaction. Furthermore, 2D-Zeolite is synthesized, characterized and postulated as a model system for studying chemistry in confined space. Furfural adsorption on Pd(111) is studied under different experimental conditions by means of infrared reflection-absorption spectroscopy. Furfural uptake experiments from sub-monolayer to multilayer coverages and sequential heating lead to an analysis of conformational changes and tilting …

Speciation, Transport, And Fate Of Heavy Metals In Soils From A Civil War Battlefield: Development Of A Novel Mae-Gf-Aas Method, Shawn Christopher Salske

Theses and Dissertations

The research herein will describe a novel method to better understand heavy metal contamination over long periods of time by studying soils for which the spatial and temporal dimensions are relatively well-defined. This work is based on the ability to pin-point the initial time and place of contamination on an American Civil War battlefield, where the firearms left distinctive chemical signatures (e.g., dropped and impacted bullets and percussion caps). The abundance and distribution of Copper and Mercury was measured in soil core samples collected at Manassas National Battlefield (Manassas, VA, USA) transecting the line occupied by an infantry regiment, a …

Development Of A Novel Sequential Injection-Proton Nmr Method For Determining Cathinones In Forensic Samples, Malati Thapa

Theses and Dissertations

A novel method was developed for the determination of low levels of Cathinones in authentic samples by interfacing Sequential Injection Analysis (SIA) to Proton Nuclear Magnetic Resonance Spectroscopy (NMR). In the first part of this study, solid phase extraction (SPE) was studied by SIA to preconcentrate the sample and remove matrix interferences. Phenylpropanolamine (PPA), Phenylephrine (PEP), and Methylephedrine (MEP) were studied as simulants for the Cathinones, representing primary, secondary, and tertiary amines, respectively. A variety of stationary, mobile, and eluent phases for several column geometries were examined, and a wide cylindrical column (20 mm6.6 mm) with a bed volume of …

Development Of An Advanced Zinc Air Flow Battery System (Phase 2), Jingyu Si

Theses and Dissertations

A zinc-air battery is the promising energy storage technology for large-scale energy storage applications due to its low cost, environmental friendliness, and high energy density. However, the electrically rechargeable zinc−air batteries suffer from poor energy efficiency and cycle life because of critical problems such as passivation, dendrite growth, and hydrogen evolution reaction. The proliferation of zinc−air batteries is limited.

The zinc-air flow battery combines the advantages of both a zinc-air battery and a redox flow battery. This combination permits the zinc-air flow battery to compete with the current leading battery technologies in the marketplace. A rechargeable Zn-air flow battery with …

Computational Materials Science And Engineering: Model Development And Case Study, Yihan Xu

Theses and Dissertations

This study presents three tailored models for popular problems in energy storage and biological materials which demonstrate the application of computational materials science in material system development in these fields. The modeling methods can be extended for solving similar practical problems and applications.

In the first application, the thermo-mechanical stress concentrated region in planar sodium sulfur (NaS) cells with large diameter and different container materials has been estimated as well as the shear and normal stresses in these regions have been quantified using finite-element analysis (FEA) computation technique. It is demonstrated that the primary failure mechanism in the planar NaS …

Characterization Of Dna Interstrand Cross-Linking Agents By Liquid Chromatograhy-Mass Spectrometry, Anahit Marina Campbell

Theses and Dissertations

This study is to characterize novel reactive oxygen species (ROS)-activated nitrogen mustard analogues and UV-activated alkylating agents by Liquid Chromatography-Mass Spectrometry (LC-MS). First, we optimized the instrument conditions to successfully ionize a few novel binapthalene analogues and methoxybenzene analogues by MS. The highest signal intensity for compounds 3-10 was observed when atmospheric pressure chemical ionization (APCI) with an optimized corona needle position of 5mm or 10 mm was used, which led to successful analysis of compounds 3-10 by MS. Second, we determined pharmacokinetic properties of a drug compound (FAN-NM-CH3), including animal study, assay development, optimization of MS/MS instrumental parameter and …

Intracellular Zinc Trafficking: An Interplay Of Proteome, Metallothioneine And Glutathione, Afsana Mahim

Theses and Dissertations

Zinc is the second most abundant transition metal in living organisms. Typically, a eukaryotic cell contains approximately 3000 zinc binding proteins, in which zinc plays structural or catalytic roles. Recently, zinc has been reported to have signaling functions as a secondary messenger. Considering the diverse cellular functions of zinc, the trafficking pathways that help zinc, following its uptake into cytosol, find the target proteins and generate native Zn-Proteins are not well-understood. For past few decades, metallothionein, a zinc binding protein with large stability constants for Zn2+, has been thought of as a mediator in transferring zinc to apo-Proteins. However, gene …

Zinc Proteomics: Interactions Of Zn2+, Cd2+, And Metal-Binding Ligands With Zn-Binding Sites In The Proteome, Eric Daniel Lund

Theses and Dissertations

Cadmium ion causes toxicity in humans, most prominently in the kidney. This thesis focuses on mechanisms by which Cd2+ harms kidney proximal tubule cells. Previous experiments have shown the time-dependent distribution of Cd2+ and Zn2+ within supernatant of pig kidney, LLC-PK1 cells after exposure to Cd2+ plus the ionophore pyrithione1. The first part of this research describes the trafficking of cadmium within LLC-PK1 proximal tubule cells, including the time dependent distribution, speciation, and quantification of Cd2+ and Zn2+ in cells exposed to Cd2+ and Cd2+ plus pyrithione. The latter treatment introduces Cd2+ into cells at time zero and permits the …

Fundamental Studies Of Trivalent F-Element Separations Using Ionic Liquids And Extraction Chromatography: Toward An Improved Talspeak Process, Charles Smith

Theses and Dissertations

Nuclear power is one of many energy sources needed to meet current world demand. With certain radioisotopes in the waste generated (e.g. actinides) requiring thousands of years to decay, limiting the amount of waste requiring long-term storage is certainly in the interest of public health. By bombarding the long-lived radioisotopes with neutrons, or transmutation, they can be converted into radioisotopes with significantly shorter (several hundred years) half-lives, making storage a realistic solution for nuclear waste. Transmutation, however, can be negatively impacted by the presence of neutron poisons, particularly lanthanide ions, which have a high neutron capture cross section, preventing efficient …