Chemistry Commons^™

The Alpha-Activator Complex, Cellular Maturation, And Catalytic Mechanism Of Iron-Type Nitrile Hydratase, Wasantha Lankathilaka Karunagala Pathiranage

Dissertations (1934 -)

In industry, chemicals are typically synthesized through catalytically accelerated chemical processes. The use of biocatalysts is an increasingly important trend in achieving environmentally friendly chemical production processes. Nitrile Hydratases (NHases) are well-known biocatalysts that are used by several manufacturers such as Mitsubishi Rayon Corporation and Lonza for the conversion of acrylonitrile to acrylamide and 3-cyanopyridine to nicotinamide, respectively. Amides, in general, are used in polymer preparation, adhesive manufacturing, and the paper industry. Refrigeration is needed in the enzymatic hydration process on the industrial scale to maintain a low reaction temperature to stabilize the NHase enzyme. The use of whole cells …

Structure And Mechanisms Of Metalloenzymes For Incorporation Of Water Across Cn And C-Cl Bonds, Xinhang Yang

Dissertations (1934 -)

Metalloenzymes are widely involved in water incorporation across CN and C-Cl bonds.1 In this research, the structure and mechanisms of two novel metalloenzymes that incorporate water across CN and C-Cl bonds were examined by biophysical approaches, computational modeling, and crystallographic methods.In the research of water incorporation across CN bonds, a novel eukaryotic nitrile hydratase (NHase, EC 4.2.1.84) from Monosiga brevicollis (MbNHase) was characterized, and the functional role of a (His)17 section and an insert region in the MbNHase, were examined by gene modifications. Each of these MbNHase enzymes provided an 22 heterotetramer, identical to that observed for prokaryotic NHases …

Investigation Of The Active Site Maturation And Catalytic Mechanism Of Nitrile Hydratases (Nhase, E.C.4.2.1.84), Irene Anyango Ogutu

Dissertations (1934 -)

Nitrile hydratase (NHase, E.C.4.2.1.84) is a metalloenzyme that catalyzes the hydration of nitriles into their corresponding amide under ambient conditions. NHase enzymes contain either a non-heme Fe3+ ion or a non-corrin Co3+ ion in their active site. NHase enzymes have industrial applications as biocatalysts in the large-scale production of acrylamide and nicotinamide, though it’s catalytic and biochemical properties are not fully understood. This research project provides insight into the active site maturation process and catalytic mechanism of NHase using peptide model complexes, site-directed mutagenesis and synthesis of deuterated proteins.Insight into the sequential maturation of the NHase active site has been …

Disinfection By-Products: Method Optimization For Quantification, Unknown Analysis, And Calculated Toxicity, Amy A. Cuthbertson

Theses and Dissertations

Disinfected drinking water contains hundreds of disinfection by-products (DBPs) that are formed by the reaction of disinfectants with natural and anthropogenic organic matter, bromide, and iodide. Understanding what these DBPs are is important because millions of people worldwide consume drinking water every day, and human epidemiologic studies have reported cancer, miscarriage, and birth defects from consuming such waters. While more than 700 DBPs are reported in the literature, very few studies quantify complete classes of chlorinated, brominated, and iodinated DBPs. The following document contains five chapters in the format designated for specific scientific journals on this subject. Chapter 1 describes …

Non-Destructive Determination Of Magnetic Audio Tape Degradation For Various Tape Chemistries Using Spectroscopy And Chemometrics, Alyssa Marie Abraham

Theses and Dissertations

This dissertation focuses on creating a non-destructive method for the identification of degraded magnetic audio tapes using attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR) and chemometrics. The primary recording medium during the second half of the twentieth century was magnetic tapes. These tapes hold some of the world’s modern cultural history. Unfortunately, the majority of these tapes were made with a polyester urethane (PEU) binder, which has shown to degrade through hydrolysis of the ester component, called sticky shed syndrome (SSS). As the name implies, degraded tapes will stick and shed onto player guides and heads during playback. …

Semiconductor Nanowire Doping: Controlling Magnetic And Electronic Properties Of Colloidal Nanowares, Preecha Kittikhunnatham

Theses and Dissertations

Electronic devices have been utilized in a wide range of applications, such as computing, data storage, sensors, lightings, energy production, and energy storage; they are building blocks of computer processors, solid state data storage devices, image sensors in digital cameras, LEDs, and solar cells, etc. These electronic devices operate based on properties of semiconductors, which are their essential components. Not only being fundamental components of electronic devices, semiconductors can be crucial materials for other applications, such as catalysts, battery electrodes, etc. One of the primary current quest on semiconductor research is to develop semiconducting materials that are more compact and …

Metastable-State Photoacid: A Comprehensive Theoretical Study Of The Photoreaction, Reverse Reaction, Thermal Isomerization, And Td-Dft Absorption In Solvent, Arwa Wasel Hamed Alharbi

Theses and Dissertations

The main objective of the research is to investigate the fundamentals of novel metastable-state photoacids. These photoacids can reversibly produce a large concentration of protons while undergoing photo-irradiation. This change in proton concentration can induce and catalyze chemical reactions, biological functions, and material properties that do not occur in the dark. (IMAGE) Scheme 1. Energy diagram of the photoreaction. (The red route is the forward photoreaction; the blue route is the reverse reaction; and the process that involves the proton dissociation of the photoacid in the dark is the green route; "t-" means trans- and "c-" means cis-). Scheme 1 …

Metastable-State Photoacids And Polymers With High Photoacidity, Thaaer Khalil

Theses and Dissertations

In recent years, metastable-state photoacids (mPAH) have been utilized to control various chemical processes using visible light and have found many applications in materials, energy, and biomedical areas. An introduction of metastable state photoacid is given in Chapter 1. In chapter 2, to clearly understand the relationship between the structures and the physicochemical properties of mPAHs, a series of mPAHs were designed and synthesized. The reversibility, stability, reverse reaction rate, and photoreaction of the mPAHs were studied in detail using UV/VIS spectroscopy. The results demonstrated that the electron-withdrawing groups on the electron-accepting moiety enhance the overall photoreaction and stability of …

Analysis Of N-Alkanes And N-Alkenes In Chukchi Sea Sediments, Salomey Asantewaa Sasu

Theses and Dissertations

This study determined the concentrations, distribution and sources of n-alkanes in core sediments from four locations: Stations H24, H30, H32 and BarC5 in the Chukchi Sea, which is in the Arctic Ocean. n-Alkanes are valuable tracers of aquatic, terrigenous and petroleum inputs and may give evidence to the extent of climate change. The study of climate change in the Arctic is important since the Arctic is warming faster than any other part of Earth. The increase in temperature is causing enhanced evaporation leading to a higher precipitation rate and hence enhanced erosion. The n-alkanes C12-C35 were analysed and characterized using …

Ph Dependent Reversible Formation Of A Binuclear Ni2 Metal-Center Within A Peptide Scaffold, Breena C. Keegan, Daniel Ocampo, Jason M. Shearer

Chemistry Faculty Research

A disulfide-bridged peptide containing two Ni²⁺ binding sites based on the nickel superoxide dismutase protein, {Ni₂(SOD^mds)} has been prepared. At physiological pH (7.4), it was found that the metal sites are mononuclear with a square planar NOS₂ coordination environment with the two sulfur-based ligands derived from cysteinate residues, the nitrogen ligand derived from the amide backbone, and a water ligand. Furthermore, S K-edge X-ray absorption spectroscopy indicated that the two cysteinate sulfur atoms ligated to nickel are each protonated. Elevation of the pH to 9.6 results in the deprotonation of the cysteinate sulfur atoms, …

Mechanistic Studies Of Atypical Reactions And Uncommon Substrates Native To Bacterial Cytochrome P450 Enzymes OletJe And Nikq, Courtney Elizabeth Wise

Theses and Dissertations

Cytochrome P450 (CYP) enzymes typically perform hydroxylation chemistry on small molecule substrates using atmospheric oxygen and electrons from redox partner proteins. This reactivity is dependent on a thiolate-ligated heme cofactor that also allows for spectroscopic detection of ligation, oxidation, and environmental changes to the iron metal. The onset of the genomics era has resulted in the discovery of CYPs that deviate from this paradigm in terms of reaction performed, cosubstrate requirements, and substrate-scope. This work focuses on two of these unusual P450s – OleT and NikQ. OleT performs an unconventional H2O2-dependent decarboxylation reaction on a standard small molecule fatty acid …

Bimetallic Systems For Heterogeneous Catalysis And Tuning Electronic Properties Of Functional Materials, Amy J. Brandt

Theses and Dissertations

Throughout the past few decades, advancements have been made in altering monometallic materials through addition of a second metal to create a bimetallic material that displays enhanced properties over its monometallic components and optimized attributes toward the intended application. However, a lack of fundamental understanding of the interactions between the two metals and between the metals and their environment can hinder the process of designing enhanced functional materials with desirable properties. In this work, careful analysis of model catalysts and metal-organic frameworks (MOFs) is performed in ultrahigh vacuum, and evaluation of the catalytic activity of the catalysts and electronic properties …

Biochemical Investigations Of Proteins Associated With Iron Homeostasis In Escherichia Coli, Matthew Ryan Blahut

Theses and Dissertations

The regulation of transition metals within living organisms is essential to the persistence of life. Of particular interest to our lab is iron due to the prevalence of this metal within the cell in addition to the numerous functions it performs. Fe-S cofactors are a significant prosthetic group consisting of iron that are necessary for the function of various metalloproteins. Generation of Fe-S clusters depends on several biosynthesis pathways varying between organisms with Isc and Suf both utilized in E. coli. While Isc controls Fe- S manufacturing under normal conditions, Suf assumes control when the cell is exposed to …

Fluidic Control System Development For Fluorescence Imaging Photometer, Ergün Kara

Theses and Dissertations

Phytoplankton are the primary autotrophic organisms in the marine food web and they produce nearly half of the global oxygen as a photosynthetic by-product [1]. Through photosynthesis, phytoplankton annually fix between 30 and 50 billion metric tons of atmospheric carbon into the marine systems, which approximately accounts for 40% of total carbon fixation [2]. Furthermore, the phytoplankton population trends are important indicators of the environmental perturbations [3]. Therefore, detection and characterization of the phytoplankton species is an important goal of the science. Several spectrometric, cytometric and microscopic techniques are already employed for characterization and quantification of the phytoplankton communities [4-6]. …

Probing The Relationship Of Cyanobacterial Toxins And Reactive Oxygen Species Within The Natural World, Meagan Lachelle Smith

Theses and Dissertations

The occurrence of harmful algal blooms (HABs) and their impacts on human health and the economy are only expected to worsen in the coming years, mainly due to climate change related factors. In Lake Wateree, SC, a HAB of the species Lyngbya wollei, has been persistent for more than 10 years and is estimated to occupy 60 - 90 km of shoreline. This natural laboratory provided and continues to provide a unique window into the chemistry and microbial ecology of HABs. Work in this dissertation was directed at answering a critical question: are biomass-to-toxin ratios constant in HABs? Initial …

Investigation Of Energy-Related Wastewater Impacts On Disinfection By-Product Formation In Drinking Water, Hannah K. Liberatore

Theses and Dissertations

Elevated bromide and iodide in drinking water sources contribute to the formation of toxic brominated and iodinated disinfection by-products (DBPs) during drinking water treatment. Energy extraction and utilization processes, including hydraulic fracturing (HF) and coal-fired power plants (CFPPs), produce wastewaters with bromide/iodide levels on the order of tens to thousands of mg/L. These wastes have the potential to impact drinking water sources through both intentional (e.g., direct discharge) and accidental (e.g., basin overflow, spill) release pathways. This research focuses on a combination of quantitative and non-targeted approaches to assess DBP formation impacts from HF and CFPP wastewaters, with complementary toxicity …

Model Pt-Re And Pt-Sn Surfaces For Heterogeneous Catalysis, Thathsara Deshani Maddumapatabandi

Theses and Dissertations

The dissertation is focused on understanding the growth, morphology and activity of model heterogeneous catalytic surfaces. Vapor deposited metal clusters on single crystal surfaces are well-defined systems that can be used to understand the growth, composition and activity relationships in commercial catalysts. A fundamental understanding of surface reactions is required in order to provide insight into the development of new catalytic materials. The model catalysts approach allows for systematic investigations due to excellent control over growth, composition and characterization under a carefully controlled ultrahigh vacuum (UHV) environment.

The nucleation, growth and chemical activity of monometallic and bimetallic Pt-Re clusters on …

Lipid Biomarkers Of Bering And Chukchi Sea Euphausiids And Their Application To Diet History, Rachel L. Pleuthner

OES Theses and Dissertations

In the eastern Bering Sea, Thysanoessa raschii are the most abundant krill species and a keystone trophic member that serve as both an important grazer and link to upper level consumers. In this system krill experience large annual variation in food resources, especially during ice advance and retreat; multiple lipid classes are used to temper the effects of those fluctuations, as well as to fuel reproduction and growth. Two shipboard feeding experiments that occurred during late spring and early summer of 2010, respectively, monitored the lipid retention in adult T. raschii and examined the fluctuation of specific lipid biomarkers under …

The Ideal And Real Gas Heat Capacity Of Cesium Atoms At High Temperatures, Louis Biolsi, Michael Biolsi

Chemistry Faculty Research & Creative Works

The Ideal Gas Heat Capacity, C_p, of Cesium Atoms is Calculated to High Temperatures using Statistical Mechanics. There Are a Large Number of Electronic States in the State Sum that Determines the Partition Function: 174 Known Levels for Cesium Atoms Below the First Ionization Potential. Thus, at High Temperatures, C_p Becomes Very Large Unless the Number of Contributing States is Constrained. Two Arguments Are Used to Do This. First, at High Temperatures, the Increased Size of the Atoms Constrains the Sum (Bethe Method). Second, the Existence of Interacting Charged Species at Higher Temperatures, Which Lowers the Ionization …

Descent In Symmetry During Solid State Transitions And Other Anomalies In Mixed Valence Compounds Axmxⅱm1-Xⅲf3 (A = K, Rb, Cs; M = V, Cr; X = 0.0 - 1.0), William O. J. Boo, Daniel L. Mattern, Robert M. Metzger

Faculty and Student Publications

The scope of solid-state transitions, from melting temperatures down to 4.2 K, is described for six systems: K_xVF₃, Rb_xVF₃, Cs_xVF₃, K_xCrF₃, Rb_xCrF₃, and Cs_xCrF₃ (for x = 0.0 to 1.0). Connections are drawn between the compounds’ compositions and structures with the various transitions and ordering events. Upon solidification from the melt and gradual cooling to room temperature, a sequential descent of symmetry appears to occur, from high-symmetry perovskite phases, through possible reconstructive transitions, to phases designated α …

A Simple And Effective Way To Overcome Carbon Monoxide Poisoning Of Platinum Surfaces In Direct Formic Acid Fuel Cells, Yaser M. Asal Mr., Islam M. Al-Akraa Dr, Sohair A. Darwish Ms

Chemical Engineering

A glassy carbon (GC) electrode modified with multi-walled carbon nanotubes (MWCNTs) and platinum nanoparticles (PtNPs), Pt/MWCNTs-GC, has been introduced for formic acid electro-oxidation (FAO). A similar loading of PtNPs has been conserved for a proper comparison between the Pt/MWCNTs-GC and the unmodified Pt/GC electrodes. The modification with MWCNTs could enhance the loading of PtNPs onto the GC electrode in a way that minimizes its agglomeration and increases its dispersion in the CNTs network. This not only increases the surface area exposed to the reaction but also interrupts the contiguity of the Pt active sites minimizing the adsorption of the poisoning …

A Promising Modification Of Pt Surfaces With Cnts For Decreasing Poisoning Impact In Direct Methanol Fuel Cells, Yaser M. Asal Mr., Islam M. Al-Akraa Dr, Aya A. Khalifa Ms.

Chemical Engineering

Direct methanol fuel cells (DMFCs) are clean energy sources that have many applications due to the high energy density of methanol as a fuel. However, this type of fuel cells (FCs) has limitations that are preventing it from being commercialized. One such limitation is the adsorption of intermediates such as CO into the surface of the Platinum (Pt) catalyst during methanol oxidation (MO) which deactivates its active sites, where the reaction is taking place, and leads to poisoning of the electrode over the long term. In this study, multi-walled carbon nanotubes (MWCNTs) have been introduced to the Pt-modified glassy carbon …

Photoswitchable Self-Complementary Hydrogen Bond Arrays, Suendues Noori, James A. Wisner

Western Research Forum

Background: Photochromism is the reversible transformation of a chemical material to another form by the absorption of electromagnetic radiation (light), where the two metastable forms have distinct absorption spectra and other properties. Photochromism in materials allows for the switching of their function solely based on irradiation with light. Polymers are used frequently as the building blocks for materials as they are versatile, multifunctional, can carry charge and be processed by solution-based deposition methods. Supramolecular polymers share the same definition as polymers with the exception that they are held together by reversible and directional non-covalent interactions such as hydrogen bonds. Synthesizing …

Recent Advances In Nanofluidic Electrochemistry For Biochemical Analysis, Zhong-Qiu Li, Zeng-Qiang Wu, Xing-Hua Xia

Journal of Electrochemistry

Nanofluidics, as a young research field, has been receiving more and more attentions. It has been successfully applied in various fields including nanoscale separation, biochemical sensing and energy conversion. The development of nanofluidics is closely related to electrochemistry that can provide a driving force for the study of the material transport characteristics in nanopores/nanochannels. On the other hand, nanopores/nanochannels can creat a microenvironment for study of spatially nanoconfined electrochemistry. The combination of nanofluidics and electrochemistry has given rise to many new theories and technologies for single molecule/particle analysis and nanofluid manipulation. Herein, we provide a review of the recent progresses …

Electrocatalytic Nanomaterials For Reduction Of Hydrogen Peroxide As Potential Radioprotectors, Rui-Hong Jia, Jin-Xuan Zhang, Xiao-Dong Zhang, Mei-Xian Li

Journal of Electrochemistry

Nanomaterials have shown many potential application prospects in the biomedical field, such as medical imaging, drug delivery and biosensing due to their unique physical and chemical properties. In this review we focus on nanomaterials that have shown not only abilities of radiation protection, but also good electrocatalytic activities toward reduction reactions of hydrogen peroxide and oxygen. We discuss the abilities of radiation protection of these nanomaterials that are ascribed to their enzyme-like activities because their catalytic properties provide an effective pathway for scavenging free radicals in vivo via rapid reactions with reactive oxygen species. We also provide insights into electrocatalytic …

Electrochemical Biosensors For Wastewater-Based Epidemiology, Yu-Wei Pan, Kang Mao, Franziska Tuerk, Zhu-Gen Yang

Journal of Electrochemistry

Wastewater-based epidemiology (WBE) has been shown to be an innovative approach for evaluation of drug use trends and public health assessment by quantifying drug residues and/or metabolites (so-called biomarkers) in wastewater collected in a local treatment plant. Community sewage sensors have been proposed and demonstrated to be powerful tools for the analysis of sewage biomarkers. In particular, electrochemical biosensors have emerged as a rapid method for the analysis of biomarkers and pathogens in wastewater due to low cost, minimal sample processing and the ability to test in the field. It has been widely used for biomedical diagnosis, environmental monitoring and …

Research Progresses In Structural Modulation And Electrochemiluminescence Of Supertetrahedral Chalcogenide Clusters, Gang Lei, Yang Liu

Journal of Electrochemistry

Electrochemiluminescence (ECL) exhibits a broad application prospect in the field of biological analysis due to its unique performance features, and the exploitation of high efficient ECL reagents offers an important tool for the development of sensors with excellent performance and practical clinical applications. Open-framework supertetrahedral chalcogenide clusters both possess the porous structure of molecular sieve and the excellent optical properties of the semiconductor, so it has attracted more and more attention in ECL analysis. Different from the traditional semiconductor quantum dots, the structure and composition of supertetrahedral chalcogenide clusters can be accurately controlled at the atomic level, and supertetrahedral chalcogenide …

Correlated Optical Imaging And Electrochemical Recording For Studying Single Nanoparticle Collisions, Lin-Lin Sun, Wei Wang, Hong-Yuan Chen

Journal of Electrochemistry

With the development of nano-fabrications in recent years, a novel strategy based on random collisions of single electroactive nanoparticles (NPs) onto an inert ultramicroelectrode (UME) has been emerged in the field of nanoelectrochemistry, and named as single nanoparticles collisions (SNCs). The technique uses a chronoamperometric method to detect transient current generated by random collisions of single NPs onto an UME. By analyzing the current signal, one could study the properties of single NPs. Although this technique can detect electrochemical or electrocatalytic currents of a single NP, the traditional SNCs technology lacks necessary spatial resolution to identify and characterize a specific …

Multiscale Approach For The Optimization Of Ketones Production From Carboxylic Acids By The Decarboxylative Ketonization Reaction, Alexey Ignatchenko

Chemistry Faculty/Staff Publications

A historical perspective on the advancement of the decarboxylative ketonization catalysis research and development in industry and in academia is given with the focus on the past twenty years. Reviewed topics cover results of the most recent computational modeling and isotopic labeling studies, fine details of the reaction mechanism, experimental evidence for the existence of hidden degenerate reactions, explanation of the reaction rate inhibition, and reversibility of the reaction course. For this reaction, characterized strictly as acid-base catalysis, the origin of the misconception about the requirement for metal oxide catalysts being reducible and oxidizable is explained. Technology solutions for the …

Single Particle Impact Electrochemistry: Analyses Of Nanoparticles And Biomolecules, Jian-Hua Zhang, Yi-Ge Zhou

Journal of Electrochemistry

Single particle impact electrochemistry (SPIEC) has grown rapidly in recent years and shown great promise in the analysis of nanoparticle properties as well as the detection of biomolecules including DNA, RNA, protein, enzyme, bacteria, virus, vesicles and others. This minireview summarizes recent advances in electroanalytical applications of SPIEC according to different analytical methods, i.e., direct electrolysis of nanoparticles or labeled nanoparticles, direct electrolysis of soft particles encapsulated redox molecule, indirect electrochemistry of particles, area and diffusion blocking, and changes in current magnitude and collision frequency.