Chemistry Commons^™

Preparation And Characterization Of Thiol Based Polymeric Materials, Junghwan Shin

Dissertations

The thiol click-type reaction is one of the most efficient chemical processes that can undergo at room temperature in the benign organic solvent providing excellent opportunity in the fabrication of new materials as well as development of new manufacturing processes. Moreover, the versatility of thiol click-type reactions with many different functional groups such as ene, yne, epoxy, isocyanate, and alkyl halide is the important aspect that should be differentiated from the classic azide-alkyne click chemistry. Although, there are tremendous studies on many areas using thiol click-type reactions, the efficiency and utilities for the material applications have been barely explored. Especially, …

Reactor R&D: Synthesis And Optimization Of Metallic Nitride Fullerenes And The Introduction Of Two New Classes Of Endohedral Metallofullerenes, Metallic Nitride Azafullerenes And Oxo-Metallic Fullerenes, Curtis Earl Coumbe

Dissertations

Metallic nitride fullerenes (MNFs) were discovered in 1999. This class of endohedral fullerenes show promise in a new diverse range of useful applications. Since then, focus has shifted to the selective synthesis of these molecules with yields that would accommodate adequate sample distribution. Using the electric arc method, the traditional yield of these molecules has been very low (i.e. < 5 mg), and only a small percentage of the fullerene products (i.e. < 5%). This dissertation introduces the novel CAPTEAR (Chemically Adjusting Plasma Temperature, Energy, And Reactivity) method that allows the targeted synthesis of MNFs in high purity and yield. This method utilizes a nontraditional oxidizing method for fullerene synthesis that has not only provided optimization of MNFs, but also resulted in the discovery of two new classes of fullerenes: metallic nitride azafullerenes (MNAFs) and oxo-metallic fullerenes (OMFs). Evidence suggests that the nitrogen of the MNAF cage provides stability for the trimetallic nitride clusters, while the OMFs are the first fullerenes to encapsulate oxygen and incorporate a seven atom cluster inside a Cgo cage.

Other efforts to increase yields resulted from scaling up production of fullerenes by using larger quantities of starting materials. These larger quantities required energy (electrical current) beyond the capacity of the traditional electric arc generator. Therefore, a new electric arc generator …

Study Of Thermal Frontal Polymerization Utilizing Reactive And Non-Reactive Additives, Veronika Grace Viner

Dissertations

Thermal frontal polymerization is a process that involves a propagating front travelling through a monomer/initiator solution and converting monomer into polymer. The effects of different reactive and non-reactive additives on front temperature, front velocity, and pot life were studied in a thermal frontal polymerization system of multifunctional acrylates. One issue with thermal frontal polymerization of acrylate monomers is the amount of smoke and fumes produced due to high front temperatures. The effect of thermally-expandable microspheres was studied utilizing a variety of monomers. Solid additives including fillers, inert phase changer materials, and high thermal conductive fillers were investigated. The addition of …

Transcript Analysis Of The Cso Operon And Characterization Of Two Sets Of Conserved Bacterial Microcompartment Genes In The Model Organism Halothiobacillus Neapolitanus, Fei Cai

Dissertations

This study was designed to achieve better understanding of (1) how carboxysome genes are regulated and expressed to yield with precise relative ratios and (2) the in vivo roles of two sets of conserved bacterial microcompartment genes, namely the three csoSl and two csoS4 genes of H. neapolitanus, in the biogenesis and function of the carboxysome. For the first goal, a detailed transcriptional profile of carboxysomal genes in H. neapolitanus was established using absolute quantification real-time RT-PCR and transcript ends analysis. This transcriptional profile revealed that a single promoter, denoted cso promoter, was located upstream from the clustered carboxysomal genes. …

Tuning Pig Liver Esterase Enantioselectivity For The Synthesis Of Unnatural Serine And Tyrosine Analogues, Dale Anthony Rosado Jr.

Dissertations

The synthesis of disubstituted and homologated unnatural amino acids and the development of a mass spectrometry based assay for enantioselectivity are presented here. Disubstituted and homologated unnatural amino acids have proven to be effective for the treatment of diseases and for use as imaging agents. Peptides that contain unnatural amino acids have also proven to be effective treatments for various disease states including cancer. The potential to evaluate such unnatural amino acids for pharmaceutical properties is limited by the available syntheses. No method currently exists that will allow for the synthesis of homochirally similar unnatural amino acids from a common …

Application Of Molecular Modeling In The Noncovalent Dispersion Of Carbon Nanomaterials, Praveen Kumar Madasu

Dissertations

Molecular modeling is a powerful tool to better understand the intermolecular interactions of carbon nanostructures. It provides structures and energies not easily obtainable from experiments and predicts properties that can be tested experimentally. Intermolecular interactions play an important role in the aggregation of various carbon nanomaterials. Three molecular modeling studies of carbon nanomaterial dispersions are presented in this dissertation, with an emphasis on illustrating how effective these theoretical techniques are in providing insight on the selection of dispersion additives. To achieve our goals, we employed molecular mechanics based methods, along with semi-empirical methods, and quantum mechanical methods, such as density …

Design, Synthesis, And Film Formation Of Fluorine Containing Colloidal Dispersions, Anuradha Misra

Dissertations

Fluoropolymers (FPs) have been subject of interest for many years, however due to extreme synthetic and processing conditions their applications have been limited. This dissertation focuses on design and synthesis of fluorine containing colloidal dispersions to advance limited knowledge and to gain further understanding of fluorine containing colloidal dispersions. Fluoroacrylates and fluoro methacrylates consisting of varying chain length of perfluoroalkyl side chain were copolymerized with methylmethacrylate (MMA) and n-butylacrylate (n-BA) under aqueous environment utilizing phospholipids (PLs) as dispersing agent. Morphologies of colloids, coalescence, and film formation processes after water evaporation was investigated using various microscopic probes such as transmission electron …

Influence Of Functional Components On The Film Formation Of Colloidal Dispersions, Kevin Lee Rhudy

Dissertations

A number of colloidal dispersions were synthesized to advance knowledge and gain understanding regarding interactions between individual components and for elucidation of complex processes governing their film formation. These studies show that for methyl methacrylate/n-butyl acrylate (MMA/nBA) colloidal dispersions, the presence of functional components significantly affects film formation. The incorporation of polyvinyl alcohol (PVOH) into pMMA/nBA colloidal dispersions creates competing environments between the copolymer particle surfaces, aqueous phases, and dispersing agents which results in migration with self-induced stratification occuring during coalescence. pMMA/nBA/PVOH films stratify to form sodium dodecyl sulfate (SDS) rich film-air (F-A) interfaces, and the -SO3" moieties exhibit preferential …

Functional Characterization And Assembly Studies Of Carboxysomes In Halothiobacillus Neapolitanus, Zhicheng Dou

Dissertations

Functional characterization and assembly studies of carboxysomes in Halothiobacillus neapolitanus were pursued in order to understand the roles of carboxysomes in the carbon metabolism in H. neapolitanus and the assembly of carboxysomes in vitro and in vivo. Previously, a low abundance H. neapolitanus carboxysomal protein, CsoSCA was identified as a novel carboxysomal shell-bound carbonic anhydrase. The enzyme is thought to dehydrate the cytosolic bicarbonate to CO2, the substrate of the RuBisCO packaged within the carboxysome [14, 21]. In this study, the carboxysomal shell was identified as a diffusion barrier for CO2 and O2 molecules. The shell-bound CsoSCA protein facilitates the …

Magnetic And Dielectric Properties Of Sulfonated (S) Poly[(Styrene)-(Ethylene-Co-Butylene)-(Styrene)] (Sebs) Block Copolymer/Magnetic Metal Oxide Nanocomposites Synthesized Via An In-Situ Precipitation Method, Sateesh Kumar Peddini

Dissertations

Block copolymer/magnetic metal oxide nanocomposites were synthesized by growing metal oxide nanoparticles (cobalt ferrite, CoFe204 and iron oxide, a-Fe203) in sulfonated (s) poly (styrene) (PS) block domains of sulfonated poly [(styrene)-(ethyleneco- butylene)-(styrene)] (SEBS) BCP preformed films via an in-situ precipitation method by dissolving the salts of respective metal chloride (s) in a suitable solvent that selectively swells the sPS regions. Inorganic uptake was determined using thermogravimetric analysis (TGA), and it was observed that none of the samples incorporated more than 5 wt % of the inorganic component. Dynamical mechanical analysis was used to observe the changes in the glass transition …

Molecular Interactions Involved In The Biogenesis Of Bacterial Microcompartments, Balaraj Balaram Menon

Dissertations

This study was undertaken with the goal of gaining better insights into the assembly pathway of carboxysomes and related polyhedra. Aside from their similarity in size and shape, all known microcompartments package enzymes that mediate key reactions of metabolic pathways [1]. It remains unclear whether the sequestered enzymes participate in microcompartment assembly and/or contribute to the overall shape of the polyhedra. Genetic studies in Salmonella enterica have suggested that the shells of organelles involved in propanediol utilization assemble in the absence of encapsulated enzymes [2]. In this study, in vivo yeast two-hybrid screens, involving components of the ethanolamine utilization (Eut) …

Investigation Into Select Isoquinolines As A Putative Causal Agent Of Ethanol Addiction In Mammals, Jacob Christopher Strawbridge

Dissertations

Alcohol is the most abused drug in America today. The neurological root of the problem is still a much debated subject and many differing views exist on the nature of alcoholism, be it a social dysfunction or a neurochemical imbalance. Some researchers have proposed that a skewed metabolism of dopamine that results in the formation of tetrahydroisoquinoline (THIQ) alkaloids plays a major role in the neurochemical acquisition and maintenance of alcohol addiction. In an effort to better understand the relationship of THIQ's to alcohol addiction, a series of experiments have been conducted. The chiral separation via high pressure liquid chromatography …

Raft Synthesis Of Water-Soluble, Stimuli-Responsive (Co)Polymers And Post-Polymerization End Group Modification Via The Thiol-Ene Reaction, Bing Yu

Dissertations

A series of water-soluble, stimuli-responsive (co)polymers was synthesized via the reversible addition-fragmentation chain transfer (RAFT) polymerization. The end group of a RAFT polymer, poly(jV-isopropylacrylamide), was modified to ene or yne function via thiol-ene click chemistry. The ene or yne end group subsequently underwent thiol-ene or thiol-yne addition affording mono- or di-functional end group. First, three methacrylic monomers containing 2 or 3 pendent tertiary amine functional groups, l,3-bis(dimethylamino)propan-2-yl methacrylate (Ml), l-(bis(3-(dimethylamino)propyl)amino)propan-2-yl methacrylate (M2), and 2-((2-(2-(dimethylamino)ethoxy)ethyl)methylamino)ethyl acrylate (M3), were synthesized via an acylation reaction between methacryloyl chloride and the corresponding aminoalcohol. All of these three monomers were successfully homopolymerized under RAFT conditions …

Synthesis And Evaluation Of Structural Analogs Of Escherichia Coli Lipid A For Application Towards Cd14-Targeting Glycotherapeutics, Aileen Fay Galos Bongat

Dissertations

Lipid A is a glucosamine-based phospholipid that anchors carbohydrate molecules to the outer membrane of most Gram-negative bacteria. During severe infection, this amphiphilic macromolecule invoke a strong and acute pro-inflammatory response that leads to sepsis and ultimately to septic shock, organ failure and death. Thus, following the convention that the best antidote is often a derivative of the parent agonistic molecule, researchers have actively pursued the idea of creating an analog of Lipid A that can block the cellular receptor for this molecule and thereby arrest the cascade of events that lead to sepsis. Consequently, we became interested in creating …

Investigation Of The Interactions Of Cationic Polyelectrolytes With Anionic Surfactants: Effects Of Polymer, Surfactant And Solution Properties, Lisa Renee Huisinga

Dissertations

The intent of this research is to explore and understand the effects that a range of polymer, surfactant and solution parameters have on the interaction of oppositely-charged polymers and surfactants. Cationic polysaccharides were chosen for this research because they are known to interact with anionic surfactants, and they offer a wide range of adjustable polymer properties, including molecular weight, charge substitution, and backbone structure. Cationic poly(vinylpyridinium hydrochloride) polymers were chosen for these studies because they provide the opportunity to explore the effects of charge position on the interaction of cationic polymers with anionic surfactants and how this influences the mechanism …

Examination Of An Aloe Vera Galacturonate Polysaccharide Capable Of In Situ Gelation For The Controlled Release Of Protein Therapeutics, Shawn David Mcconaughy

Dissertations

A therapeutic delivery platform has been investigated with the ultimate goal of designing a sustained protein release matrix utilizing an in-situ gelling, acidic polysaccharide derived from the Aloe vera plant. The Aloe vera polysaccharide (AvP) has been examined in order to determine how chemical composition, structure, molecular weight and solution behavior affect gelation and protein/peptide delivery. Correlations are drawn between structural characteristics and solution behavior in order to determine the impact of polymer conformation and solvation on gel formation under conditions designed to simulate nasal applications. Steady state and dynamic rheology, classic and dynamic light scattering, zeta potential, pulse field …

Dispersion States And Surface Characteristics Of Physically Blended Polyhedral Oligomeric Silsesquioxane/Polymer Hybrid Nanocomposites, Rahul Misra

Dissertations

Control of dispersion and segregation states of nanostructured additives is one of the biggest challenges in realizing the optimum potential of high-performance hybrid polymer nanocomposites. Polyhedral oligomeric silsesquioxane (POSS) nanostructured chemicals, with their hybrid organic-inorganic nature and flexible functionalization with a variety of organic substituents, yield possibilities to control dispersion and tune compatibility in a wide range of polymer systems. The overall goal of this research is to investigate the fundamental parameters that influence the dispersion and segregation states of POSS nanostructured chemicals and to understand chain dynamics and conformations in physically blended POSS hybrid polymer nanocomposites (HPNC's). Multiple structural …

Synthesis, Propagation Kinetics, And Characterization Of D,L-Lactide-Based Polyols And Polyurethanes Therefrom, Scott Joseph Moravek

Dissertations

In order to expand the usefulness of degradable polyesters, degradable polyurethanes were synthesized using a mixed polyol system including poly(D,L-lactideco- glycolide) (PLGA), a well-known degradable polyester. Two isocyanate systems, methyl 2,6-diisocyantocaproate (LDI) and dicyclohexylmethane-4,4'- diisocyanate(Hi2MDI), were studied in order to achieve optimal physical and thermal properties of the thermoplastic polyurethane (TPU) while maintaining degradablity. The LDI based systems had excellent physical properties as well as thermal properties that may make them suitable for biomedical devices. The H12MDI based TPUs also had excellent physical properties as well as a higher melting temperature. The aforementioned TPUs were synthesized in small batches. Another …

Preparation Of Carboxylic Acid Functionalized Glycopolymers Through Raft And Post-Polymerization Modification For Biomedical Application, Husnu Alp Alidedeoglu

Dissertations

The primary theme of this dissertation involves the synthesis of well-defined primary amine functionalized polymers, subsequent modification of the polymers to produce novel carboxylic acid functionalized glycopolymers and surface polymerization of these systems utilizing controlled polymerization techniques. Additionally, the synthesis of new water-based allylic copolymer latexes is described. Carbohydrates are natural polymers which possess unlimited structural variations. They carry a huge density of information, and play major roles in recognition events and complex biological operations. For example, hyaluronic acid (HA), an anionic glycosaminoglycan, provides lubricating and cushioning properties in the extracellular matrix and has been found to be involved in …

Photopolymerization And Characterization Of Thiol-Enes And Thiourethanes, Qin Li

Dissertations

Compared to conventional acrylic monomer systems, thiol-ene photopolymerization, an efficient click process leading to the formation of dense and uniform molecular networks, has several distinct advantages including relative insensitivity to oxygen inhibition, high monomer conversion and low shrinkage. Although there has been a revival of interest in thiol-enes in the past 6 years, the structure-property relationship of these networks has not been explored in detail. For future applications, thiol-enes with higher shelf-life stability and glass transition temperatures need to be used. Sulfur containing urethanes, thiourethanes and dithiourethanes are a class of widely used materials due to their distinct properties such …

The Relationship Betweeen Dynamic And Chemical Factors On The Morphology In Aot-Water-Polymer Systems, Jolanta Elzbieta Marszalek

Dissertations

Photopolymerization of reverse microemulsion demonstrates strong influences from dynamical and chemical factors on morphology of formed polymer systems. Upon polymerization the clear microemulsion with nanoscale structures transforms into opaque films with larger aggregates that scatter light. Studied here were microemulsions based on acrylate and on thiol-ene chemistries. The difference in the two reaction mechanisms results in the phase separation occurring at different stages of the material formation. Consequently, the morphology of the material demonstrates distinct dissimilarities in the two systems. In addition, the chemical structure of the monomers promotes these morphological differences. When the microemulsion is composed of acrylate and …

Switch On And Switch Off Nanosensors For The Detection Of Nerve Gas Agents, Shankar Varaganti

Dissertations

The central hypothesis of this research is the development of novel nanosensors by a bottom-up approach for the detection of nerve gas agents. The nanosensor assembly consists of four main parts; nanoparticles (N), Monomer (M), Complex (C) and Receptor (R). Two novel Ru (II)-bipyridyl and zinc complexes with tryptophan receptors either in 4,4' or 5,5' position of the bipyridyl ring have been synthesized and characterized by using ¹H NMR, ¹³C NMR, mass spectrometry and absorption spectroscopy. Silica nanoparticles or quantum dots are used as a platform for the nanosensors. Highly conjugated stilbene type compounds are used as monomers. …

Evaluation Of Electron Donor Materials Used To Create Subsurface Permeable Reactive Barriers For Enhanced Reductive Dechlorination Of Chlorinated Ethenes, Elizabeth S. Semkiw

Dissertations

Chlorinated ethenes (CEs) are widespread ground water contaminants, apparently due to their extensive migration from numerous contamination source points. In this study, a long-term field investigation and aquifer microcosm experiments were combined to evaluate the effectiveness of electron donor materials used to create and maintain subsurface permeable reactive barriers (PRBs) for the enhanced in-situ biodegradation of CEs. The laboratory component includes the first side-by-side comparison of electron donor materials dairy whey, lactate syrup, and Hydrogen Release Compound® (HRC), in which dechlorination rates, fermentation product distributions, and H₂ production were monitored as measures of substrate efficiency. Field study allowed the …

Reduction Of Toxicity In The Premature Neonate Addociated With Aluminum As A Contaminant Of Total Parenteral Nutrition Solution, Sujittra Srisung

Dissertations

Aluminum (Al) is the third most common element in the Earth?s crust. It is widely consumed in water, foods, and drugs. However, in humans, the uptake of aluminum into the body and its deposition in tissues has been linked to conditions of medical concern, including many neurological disorders such as dialysis dementia, Alzheimer?s disease, Parkinson?s dementia and Down?s syndrome. Premature neonates who receive intravenous feeding (TPN) are at a high risk for Al toxicity because the TPN solutions are contaminated with Al3+, which is not excreted effectively due to poor kidney development in these patients. The FDA has recommended regulations …

Identification Of Two Distinct Glutaminyl Cyclase Isoforms In Drosophila Melanogaster, Amanda Thigpen Parker

Dissertations

Sequence analyses revealed two putative glutaminyl cyclase genes in Drosophila melanogaster with greater than 60% amino acid sequence identity to previously identified glutaminyl cyclase in humans. Expression, purification, and characterization of both putative proteins revealed two enzymatically active glutaminyl cyclase enzymes. Comparison of the Drosophila melanogaster glutaminyl cyclase enzymes to the published human glutaminyl cyclase revealed the enzymes were very similar. The Km values obtained were identical to those of human glutaminyl cyclase for three different substrates tested. However, the Drosophila glutaminyl cyclases demonstrated lower turnover numbers. Both Drosophila glutaminyl cyclase isoforms were inhibited by imidazole, imidazole derivatives, and metal …

Towards Development Of A Fully Synthetic Conjugate Vaccine: Investigation Of Structural Analogs Of Streptococcus Pneumoniae Serogroup 6, Archana R. Parameswar

Dissertations

Involvement of complex glycostructures in a variety of damaging and healing processes has already been acknowledged by development of carbohydrate-based vaccines and therapeutics. The bacteria Streptococcus pneumoniae (SPn) have become one of the most frequent causes of pneumonia, bacteremia, and meningitis in the elderly, immunocompromised, and, especially, in young children. SPn has one of the largest public health and economic impacts amongst all bacterial infectious diseases. Over 2 million children die annually worldwide due to pneumonia, accounting for almost 20% of deaths under age five with more than half of these deaths attributed to SPn. Amongst over ninety elucidated SPn …

Synthesis Of Α-Hydroxy And Fluoro Phosphonates And Cyclic Ether-Containing Natural Products, Nongnuch Sutivisedsak

Dissertations

A number of important classes of natural product (eg. amphidinolide C, (-)-centrolobine, etc) contain common structural features of tetrahydrofurans and tetrahydropyrans. This study involved the development of stereoselective mothods for the synthesis of tetrahydrofurans and tetrahydropyrans including the application of allylic hydroxy phosphonates and their derivatives as chiral, non racemic building blocks for the synthesis of biological active molecules. The enantiomeric excess of non racemic α-hydroxy phosphonates and carbonate derivatives prepared via the asymmetric Pudovik reaction can be improved by kinetic resolution. Both chemical and enzyme catalysts were utilized in the kinetic resolution of phosphonates. Enantioselective acylation of a variety …

The Effect Of Active Site Mutations On The Homodimeric Behavior Of The Pvuii Restriction Endonuclease, Grigorios A. Papadakos

Dissertations

The PvuII restriction endonuclease, a homodimer of two 18 kDa subunits, belongs to the type II family of restriction enzymes. Located in the active site of PvuII, Tyrosine 94 has previously been shown to be involved in the metal ion binding by the enzyme. The profile of the Ca2+ dependence of the DNA binding to the Y94F variant is shown to be clearly biphasic. The application of a sequential binding model yielded a coupling energy (ΔGcoop) at -0.54 for the upper phase and -1.15 kcal/mole for the lower phase. The similar metal binding pattern between the Y94F and the WT …

Mechanistic Studies Of Specific Dna Cleavage By Pvuii Restriction Endonuclease, Xie Fuqian

Dissertations

PvuII restriction endonuclease is a homodimeric protein which recognizes and cleaves the palindromic sequence (CAG?CTG) in the presence of Mg(II) ions. Starting with PvuII as a model system, pKa calculations with crystallographically defined metal ligated water are applied to PD?D/ExK motif metallonucleases in order to investigate the activation of nucleophile in metal dependent DNA hydrolysis. These results establish the electrostatic contributions of the metal ions and the conserved Lys in lowering water pKa. The calculated pKa values of metal ligands have been used to simulate the pH dependence of Mg(II) binding to PvuII. The bell shaped pH-rate profile is dissected …

Exploration Of The Chemical And Biological Processes Through Molecular Dynamics Simulation And Blocklocalized Wavefunction Method, Yuchun Lin

Dissertations

Computer simulation plays a crucial role in interpreting, unifying and guiding experimental observations. In this dissertation, molecular dynamics (MD) simulations and the block-localized wavefunction (BLW) method have been used to explore the chemical and biological processes.

Detailed MD simulations were performed to study the transportation of NH₄⁺, NH₃ and H₂O through the Escherichia coli ammonium transporter (AmtB) membrane protein. A periplasmic recruitment vestibule was identified and the entrance of an NH₄⁺ into this vestibule requires only 3.1 kcal/mol. In the end of this vestibule, the phenyl ring of Phe107 dynamically opens and …