Physical Chemistry Commons^™

Alkynal Involved Organocatalytic Reactions, Xinshuai Zhang

Chemistry and Chemical Biology ETDs

During the past twenty years, vast progress has been achieved in the field of organocatalysis. One of the fruitful areas is iminium catalysis using α, β-unsaturated aldehydes as essential reactants. Enals involved enantioselective reactions (including single-step reactions and cascade/tandem reactions) represent an enormous and fruitful research branch. In contrast, the protocols for the corresponding alkynals, even in single-step conjugate addition reactions, are extremely rare. Toward this end, my Ph. D. research work mainly focuses on the development of alkynal involved organocatalytic reactions and expands the scope of organocatalysis by uncovering new activation modes. Unlike enals, ynals with sp hybridized C≡C …

Development Of Novel Organocatalytic Cascade Reactions And Application In Organic Systheses, Xixi Song

Chemistry and Chemical Biology ETDs

The development of new catalytic reactions, particularly synthetically efficient cascade processes for the facile preparation of important molecular architectures, which otherwise are difficult to access via traditional methods, is of considerable significance. Toward this end, my Ph.D. work focuses on developing new organocatalytic reactions and their applications in organic syntheses. A novel direct organocatalytic stereoselective α-arylation methodology has been discovered. The cross-coupling-like products are assembled using simple enals and various brominated aromatic systems, such as p-bromophenols, bromonaphthols and 3-bromoindoles. The products have been applied in the concise photo-syntheses of [α]-annulated carbazoles. Moreover, an unexpected reaction has been identified with aliphatic …

A Proposed Palladium-Catalyzed Cycle For The Epoxidation Of Alkenes, Marie Vernell Parkes

Chemistry and Chemical Biology ETDs

Epoxides are an important chemical functional group, used in a wide variety of processes, from the small-scale production of pharmaceuticals to the large-scale production of propylene oxide. Current methods for production of epoxides require costly multi-step syntheses that use toxic or explosive reagents, result in low yields, and produce co-products that must be removed and often disposed. The development of an atom-efficient general method, preferably catalytic, for converting alkenes to epoxides using safe, cheap, and readily available molecular oxygen as the stoichiometric oxidant would be a great advance in both industrial and academic chemistry. Presented here is a proposed catalytic …

Function Assignment Within The Haloacid Dehalogenase Superfamily, Hua Huang

Chemistry and Chemical Biology ETDs

The HaloacidDehalogenase Enzyme Superfamily (HADSF) is a ubiquitous family of enzymes. Presently, more than 45,000 deposited gene sequences encode proteins of the HADSF, and only a fraction of these have defined structure and/or function. The work described in this thesis focuses on function determination in several members of the HADSF. An integrated bioinformatic-protein structure-enzyme mechanism approach was used to differentiate and track D-glycero-D-manno-heptose-1,7-bisphosphate phosphatase (GHMB) and histidinol phosphatephosphatase (HisB)orthologues; 2-keto-3-deoxynononic acid 9-phosphatephosphatase (KDN9PP) and 2-keto-3-deoxy-D-manno-octulosonic acid 8-phosphatephosphatase (KDO8PP)orthologues; inorganic pyrophosphatase and β-phosphoglucomutase(β-PGM) orthologues. In addition, a structure-function/bioinformatic analysis was carried-out on the bifunctional 1,3-diposphoglycerate acyltransferase/Cys-S-glyceryl-3-phosphate phosphatase (FKBH). Each study began …

Evolution Of Structure And Function Among Hotdog-Fold Thioesterases And Had Family Phosphatases, Wang Min

Chemistry and Chemical Biology ETDs

My doctoral research began with the function assignment to two domains of fusion protein BT4699, from Bacteriodes thetaiotaomicron, BF1314 from Bacteriodes fragilis and PG1653 from Porphyromonas gingivalis. BT4699, however, is insoluble, so its orthologue BF1314 and PG1653 were prepared and studied. The fusion proteins consist of a domain that belong to a large family of phosphatases known as Haloacid Dehalogenase (HAD) superfamily, and a domain belong to the hotdog-fold thioesterase superfamily. The genes encoding the fusion proteins located at an operon that encoding enzymes involved in the menaquinone biosynthetic pathway. So we assumed that the thioesterase domain is connected to …

I. The Synthesis And Coordination Chemistry Of Novel 6Π-Electron Ligands. Ii. Improvement Of Student Writing Skills In Chemistry Lab Reports Through The Use Of Calibrated Peer Review, Wilson Ngambeki William

Chemistry and Chemical Biology ETDs

ABSTRACT I

The goal of this study was to synthesize and characterize a set of coordination complexes containing 6π-cationic ligands. These compounds could be extremely useful as catalysts for the polymerization of olefins that are widely used in the synthetic polymer industry. The original strategy was to synthesize the 6π-cationic ligands using (Ph₂P)₃CH (1) and (Me₂P)₃CH (10) as precursors; however, both precursors 1 and 10 were found to be highly reactive leading to the fragmentation products (Ph₂P)₂CH₂ and (Me₂P)₂CH₂ respectively. In trying …

Structural Characterization Of Metal Binding In Metallo-Β-Lactamases Using X-Ray Absorption Spectroscopy, Robert M. Breece

Chemistry and Chemical Biology ETDs

In an effort to probe the structure and mechanism of metallo-β-lactamases, the metal-binding behaviors of several enzymes were studied using EXAFS (Extended X-ray Absorption Fine Structure). Three members of the metallo-β-lactamase subclass B1, BcII from Bacillus cereus, Bla2 from Bacillus anthracis and CcrA from Bacillus fragilis, were compared to examine metal-binding behavior within a subclass. Each system exhibits different metal-binding behavior including cooperative binding (BcII), sequential binding (CcrA), and differential binding between zinc(II) and cobalt(II) forms (Bla2). The metal-binding behavior of subclass B3 of L1 from Stenotrophomonas maltophilia was explored with RFQ (rapid-freeze quenched) EXAFS and site selective metal …

Mechanistic Studies On Xanthine Oxidoreductase Enzymes, Abebe Berhane

Chemistry and Chemical Biology ETDs

In humans, the xanthine oxidoreductase enzymes are known to catalyze the final two steps of purine metabolism by converting hypoxanthine successively to xanthine and uric acid. Xanthine oxidoreductase also metabolizes a wide variety of drugs in vivo, and activates a number of antiviral prodrugs of clinical importance. Therefore, understanding the reaction mechanism of this enzyme is of prime importance in furthering our understanding of enzyme-drug interactions. In order to provide a greater understanding on the reaction mechanism, theoretical and enzymatic spectroscopic experimental approaches have been utilized. The theoretical approaches were used to elucidate the electronic structure and geometry of the …

Probing Morphology-Dependent Aggregation And Photocurrent Generation In Polymer/Fullerene Photovoltaic Devices, Yongqian Gao

Chemistry and Chemical Biology ETDs

In this dissertation, new spectroscopic and electrical imaging approaches were developed to map morphology-dependent aggregation properties of polymer chains in model solar cell devices. These techniques reveal new correlations between local structure and material performance on sub-micron size scales which are not accessible by other techniques. Resonance Raman spectroscopic imaging was developed as a physical probe to identify and spatially map morphology-dependent variations of intra- and interchain interactions and order in poly-3-hexylthiophene (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) photovoltaic blend thin films. The C=C band of P3HT backbone was decomposed into aggregated and unaggregated component contribution at ~1450 cm …

Quantitative Structure-Property Relationships For Predicting Chlorine Demand And Disinfection Byproducts Formation In Drinking Water, Gebhard Balthazar Luilo

Chemistry and Chemical Biology ETDs

Models are important tools for designing or redesigning water treatment processes and technologies to minimize disinfection byproducts (DBPs) formation without compromising disinfection efficiency. Empirical models, which are the most common, are based on bulk water quality parameters that vary with time and space. These parameters may not always have linear relationships with chlorine demand and DBPs formation which make structure-based models more attractive to study. In this dissertation, Quantitative Structure-Property Relationship (QSPR) models which make use of structural properties of individual molecules were developed using experimental data obtained from the literature. The amounts are reported in moles of chlorine (HOCl) …

Spectroscopic And Electronic Structure Studies Of Metalloenzyme Active Sites, Joseph Sempombe

Chemistry and Chemical Biology ETDs

This work reports on the electronic and geometric structural studies of xanthine oxidoreductase (XO), S-ribosylhomocysteinase (LuxS) and inducible nitric oxide synthase (iNOS) active sites resulting from the joint applications of electronic absorption, electron paramagnetic resonance and magnetic circular dichroism spectroscopic methods. XO catalyzes formal oxygen atom insertion into a substrate C-H bond, but differs from monooxygenase enzymes in that the inserted oxygen atom derives from metal activated water and reducing equivalents are generated rather than consumed. Studies on aldehyde inhibited' XO (a paramagnetic form observed during XO catalysis), analyzed in terms of the relationships between the g-, ^95,97Mo hyperfine, …

Spectroscopic And Electronic Structure Studies Of Bis-Metallodithiolenes, Regina Peter Mtei

Chemistry and Chemical Biology ETDs

Dimethylsulfoxide reductase (DMSOR) enzyme family members catalyze oxygen atom transfer to or from organic or inorganic substrate and play important roles in the global cycles of sulfur and nitrogen, as well as the detoxification of arsenite. This enzyme has recently been subject of investigation due to its catalytic nature of oxygen atom transfer. This work reports on the electronic structure and reactivity properties of dimethylsulfoxide reductase enzyme studied using spectroscopic and computational methods. The spectroscopic methods included electronic absorption (EA), electron paramagnetic resonance (EPR), magnetic circular dichroism (MCD) and resonance Raman rRaman). Here, we report full characterization of the DMSOR …

Antibacterial Activity Of Conjugated Electrolytes, Thomas S. Corbitt

Chemistry and Chemical Biology ETDs

A series of water soluble, cationic, anionic and zwitterionic conjugated polyelectrolytes (CPEs) with main chains based on an arylene ethynylene repeat unit structure with tetraalkylammonium and/or alkylsulfonate side groups were found to exhibit significant antibacterial activity. A number of these complexes also showed pronounced light-induced modulation of their effectiveness, with either biocidal enhancement or suppression, depending on such properties as singlet oxygen sensitization potential and lipophilicity. These collected studies examine the biocidal activity of the CPEs, as determined by Confocal Laser Scanning Microscopy (CLSM) and Flow Cytometry, correlating this activity with the photophysical properties of the polymers. We demonstrate biocidal …

Investigations Into Late Transition Metal Pincer Complexes As Possible Direct Partial Oxidation Catalysts, Raymond B. Lansing Jr.

Chemistry and Chemical Biology ETDs

This investigation examined aspects of a potential catalytic route for the partial oxidation of organic substrates using molecular oxygen as the oxidant. The proposed cycle begins with the insertion of molecular oxygen into a metal hydride bond to generate a metal hydroperoxide. The next step involves the transfer of an oxygen atom to an acceptor substrate to generate an oxidized species and a metal hydroxide. The starting metal hydride can then be regenerated in two viable ways, either through use of CO or H₂. The experimental plan involved the syntheses and characterization of new inorganic and organometallic complexes, …

Studies Of A Cyanine-Based Biosensor And Light-Induced Antibacterial Activities Of Oligo(Phenylene Ethynylene)S, Zhijun Zhou

Chemistry and Chemical Biology ETDs

This dissertation has been focusing on two subjects: biosensor development and light-activated antimicrobials. A cyanine-based fluorescent biosensor is developed with high sensitivity to detect the presence and activity of caspase-3/7. We demonstrated that supramolecular self-assembly can be useful for designing biosensors. A series of p-Phenylene Ethynylenes (OPEs) have been synthesized. Further photophysical studies show that these molecules have good singlet oxygen yields. The antimicrobial capability increases dramatically when exposed to UV-365 radiation, though dark biocidal activity can be obtained as well. This phenomenon is probably due to the high yields of singlet oxygen of these OPEs, which oxidizes unsaturated membrane …

Human Mitochondrial Hotdog-Fold Thioesterase: Hthem4 And Hthem5, Hong Zhao

Chemistry and Chemical Biology ETDs

Hotdog-fold acyl-CoA thioesterases (ACOTs) are found in all three kingdoms of life (Archaea, Bacteria and Eukarya). All the hotdog-fold thioesterases share common catalytic scaffold and function: hydrolysis of acyl-CoA or acyl-ACP (acyl carrier protein). However the biological roles that they perform vary greatly, different substrate specificity and catalytic efficiency assign unique set of biological functions to each of them, which is further defined by tissue distribution, cellular location, protein partners and regulators. The focuses of my doctoral studies, described in this dissertation, are two members of the human hotdog-fold thioesterase superfamily: human THEM4 and human THEM5. The genes encoding hTHEM4 …

Studies On Group 10 Pincer Carbene Metal Complexes, Agnes Mrutu

Chemistry and Chemical Biology ETDs

Selective oxidation chemistry is a topic of intense interest worldwide, in particular when using molecular oxygen (O₂) directly as the oxidizing species. The primary reason for using O₂ rather than other oxidants is to take advantage of the inexpensive nature of oxygen; however, the radical ground state of O₂ leads to non-selective reactions with organic substrates. As such, basic knowledge and understanding involving the fundamental reactions of O₂ with organometallic species will be required in order to overcome this lack of selectivity. The work presented in this dissertation has two main research goals to help …

Divergence Of Thioesterase Function: Human Bfit2, Escherichia Coli Enth, And Ydii, Danqi Chen

Chemistry and Chemical Biology ETDs

My doctoral research primarily focuses on two hotdog-fold thioesterases, EntH (also known as YbdB) from E. coli, and BFIT2 from Homo sapiens. The EntH (YbdB) gene is included in a large gene cluster that encodes the enzymes of the biosynthetic pathway leading to enterobactin. Building on the hypothesis that EntH might function in a house-keeping' role by liberating misacylated EntB, two potential pathways to EntB misacylation were identified, one involving the phosphopantetheinyl transferase EntD and the other involving 2,3-DHB-AMP ligase EntE. EntH displays thioesterase activity towards a variety of acyl and aryl-holo EntB adducts. Lastly, It was shown that EntF …

The Nature And Kinetic Analysis Of Carbon-Carbon Bond Fragmentation Reactions Of Cation Radicals Derived From Set-Oxidation Of Lignin Model Compounds, Adam S. Pimentel

Chemistry and Chemical Biology ETDs

The lignin peroxidase promoted α-carbon β-carbon bond cleavage of two diastereomeric pairs of dimeric lignin model compounds were investigated to determine which structural units are more readily cleaved. These model compounds, β-1 (1,2-diaryl-1,3-propanediol) and β-O-4 (1-diaryl-2-aryloxy-1,3-propanediol), represent the most common structural units present in the plant cell wall polymer lignin. The lignin peroxidase catalyzed reaction mechanism was shown to parallel two mechanistically well understood systems, the cerric (IV) ammonium nitrate promoted chemical reacton, and the dicyannoanthracene promoted photochemical reaction, both of which proceed by a SET mechanism. Product profiles and kinetic rate constants were determined and compared for all four …

Quantitative Structure-Property Relationships For Predicting Group Iib Metal Binding By Organic Ligands, Aliyar Mousavi

Chemistry and Chemical Biology ETDs

Mercury (Hg), cadmium (Cd), and zinc (Zn) in the environment are all of toxicological and environmental concern, and the pollution of natural waters by any of these three elements is most serious. Mercury is the most environmentally concerning of the three because of the neurotoxin species monomethylmercury produced in aquatic systems through the methylation of Hg²⁺ by aquatic microorganisms. An important chemical process in natural waters that limits the availability of mercury for methylation is the binding of Hg(II) by natural organic matter (NOM). These associations are exceptionally strong, and as NOM is ubiquitous in aquatic environments, estimating equilibrium …

Development Of Novel Synthetic Methodologies And Their Use In Approaches For The Preparation Of Lactacystin, Lepadiformine And A Giardia Lamblia Fructose-1,6-Bisphosphate Aldolase Inhibitor, Jiwen Zou

Chemistry and Chemical Biology ETDs

The investigations carried out in my doctoral studies focus on (1) applications of pyridinium salt photochemical and tandem ene-yne-ene metathesis reactions to the synthesis of the natural products (+)-lactacystin and lepadiformine C, and (2) the preparation of a novel inhibitor for the class II Giardia lamblia fructose-1,6-bisphosphate aldolase. New developments in the area of pyridinium salt photochemistry were explored in the context of approaches to the natural product (+)-lactacystin. The results of this effort show that irradiation of a substituted 1,2-cyclopenta-fused pyridinium salt in aqueous solution followed by treatment with sodium bicarbonate leads to selective production of an unusual, structural …

Investigation Of Co2 Insertion Into Lanthanide Amides, Alkoxides, And Mixed Amide/Alkoxides, Leigh Anna M. Ottley

Chemistry and Chemical Biology ETDs

A novel set of lanthanide (Ln) alkoxycarbonates, [Ln(μ-CO₂-DBP)(DBP)₂]₂ where Ln = lanthanide; and DBP = OC₆H₃-2,6-C(CH₃)₃, were isolated from a systematic study of the insertion of CO_2(g) (referred to as CO₂) into the Ln-O bonds of a series of new lanthanide alkoxides, Ln(OR)₃. This study was undertaken to determine if the deleterious metal carbonate [M(CO₃)_y] formation that promotes higher thermal budgets during processing could be avoided. While processing controls can reduce the formation of the M(CO₃) …

Development Of Novel Fluorescent Sensors For The Detection Of Functional And Bio-Interesting Small Molecules And Metal Ions, Wei Jiang

Chemistry and Chemical Biology ETDs

As one important kind of sensitive analytical technology, fluorescence method is widely applied in environmental science, materials, medicine pharmacy and nowadays much popularly in cellular biological science, which requires the development of diverse fluorescent sensors to meet various analytical and researching demands. During my Ph.D. study, my work focuses on the development of novel fluorescent sensors for the detection and specific recognition of functional and bio-interesting small molecules and metal ions, and the contents are described in this dissertation using three sections. In the first part, novel fluorescent sensors for the specific recognition of bio-toxic thiophenols have been developed based …

Characterization Of Dissolved Organic Matter By Separation And Fluorescence Spectroscopy, Yurong Deng

Chemistry and Chemical Biology ETDs

The goal of this work is to evaluate new methods of extracting and fractionating dissolved organic matter (DOM) using liquid-liquid and solid-phase extraction (SPE), monitored by optical spectroscopy. DOM in aquatic systems from different sources was characterized by three-dimension excitation-emission matrix fluorescence spectroscopy (3DEEMS) and UV absorbance spectroscopy. UV and visible humic-like fluorescence were observed in all water samples -- humic acids (HA), fulvic acids (FA), river water, wastewater, and their fractionations. Their fluorescence centers varied with environment in the range of λex/ λem = 220-250 nm/390-460 nm for UV humic-like fluorescence (peak A) and λex/ λem = 300-340 nm/390-460 …

Synthesis And Coordination Chemistry Of New Oxazoline And Benzoxazole Based Ligands With Lanthanides, Edicome Cornel Shirima

Chemistry and Chemical Biology ETDs

In Chapter 1, a brief literature review on the chemistry of lanthanides (Ln) and actinides (An) is described. In addition, the coordination chemistry of lanthanides/actinides with various ligands comprised of organic backbones has also been described. In Chapters 2 and 3 the syntheses of oxazoline and benzoxazole ligands is described. Both ligands contain a hard donor group (P=O) and the nitrogen (N) atom from the heterocycle as a relatively softer donor atom. In Chapter 2 the oxazoline ligand was synthesized in two steps reaction that involves substitution with Ph₂P group and oxidation of the phosphine into P=O by …

Paramagnetic Resonance Studies Of Bistrispyrazolylborate Cobalt(Ii) And Related Derivatives, William K. Myers

Chemistry and Chemical Biology ETDs

Herein, a systematic frozen solution electron-nuclear double resonance (ENDOR) study of high-spin Co(II) complexes is reported to demonstrate the efficacy of methyl substitutions as a means of separating dipolar and contact coupling, and further, to increase the utility of high-spin Co(II) as a spectroscopic probe for the ubiquitous, but spectroscopically-silent Zn(II) metalloenzymes. High-spin (hs) Co(II) has been subject of paramagnetic resonance studies for over 50 years and has been used as a spectroscopic probe for Zn metalloenzymes for over 35 years. However, as will be seen, the inherent complexity of the electronic properties of the cobaltous ion remains to be …

Methods In Industrial Biotechnology For Chemical Engineers, Florentin Smarandache, W.B. Vasantha Kandasamy

Branch Mathematics and Statistics Faculty and Staff Publications

Industrial Biotechnology is an interdisciplinary topic to which tools of modern biotechnology are applied for finding proper proportion of raw mix of chemicals, determination of set points, finding the flow rates etc., This study is significant as it results in better economy, quality product and control of pollution. The authors in this book have given only methods of industrial biotechnology mainly to help researchers, students and chemical engineers. Since biotechnology concerns practical and diverse applications including production of new drugs, clearing up pollution etc. we have in this book given methods to control pollution in chemical industries as it has …

Multivalued Logic, Neutrosophy And Schrodinger Equation, Florentin Smarandache, Victor Christianto

Branch Mathematics and Statistics Faculty and Staff Publications

This book was intended to discuss some paradoxes in Quantum Mechanics from the viewpoint of Multi-Valued-logic pioneered by Lukasiewicz, and a recent concept Neutrosophic Logic. Essentially, this new concept offers new insights on the idea of ‘identity’, which too often it has been accepted as given. Neutrosophy itself was developed in attempt to generalize Fuzzy-Logic introduced by L. Zadeh. While some aspects of theoretical foundations of logic are discussed, this book is not intended solely for pure mathematicians, but instead for physicists in the hope that some of ideas presented herein will be found useful. The book is motivated by …

The Extraction And Coordination Chemistry Of An Organophosphorus Ligand: The Synthesis And Characterization Of Organophosphorus Ligands And Dendrimers Using The Michael-Type Addition, Evelyn M. Bond

Chemistry and Chemical Biology ETDs

In chapter 1, the liquid/ liquid extraction of americium (III) from nitric and hydrochloric acid solutions with chloroform solutions of 2, 6 bis[(diphenylphosphino)methyl]pyridine N, P, P' trioxide (ENOPOPO) is examined. Americium (III) is efficiently extracted from aqueous solutions at high nitric acid concentrations (D_Am > 3000 at 6 M HNO₃) and can be totally back extracted from the organic phrase at 0.01 M HNO_3. The ligand dependency data suggest that two ligand molecules are coordinated to the americium. From hydrochloric acid solutions, ENPOPO exhibits modest extraction ability for americium (III) (D_Am = 2.2 at 5 M …

Analytical Applications Of Ultrasonic Velocity Using Three-Transducer Phase-Shift Detection, Chuan Chen

Chemistry and Chemical Biology ETDs

A new method for determining ultrasonic velocity and its appli­cation as a high-performance liquid chromatography (H.P.L.C.) detector is developed. The method involves in using a three­transducer phase-shift device where two transducers alternately transmit 1-MHz continuous wave signals to the same receiver. Ultra­sonic velocity can be calculated from the phase-shift difference between the two cell paths. When the device is used as an H.P.L.C. detector, the reciprocal of the phase-shift difference between the two cell paths is converted to an electrical signal and recorded on a chart paper with respect to retention time. The theoretical principles are discussed and the appropriate …