Chemistry Commons^™

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 …

Hadron Models And Related New Energy Issues, Florentin Smarandache

Branch Mathematics and Statistics Faculty and Staff Publications

The present book covers a wide-range of issues from alternative hadron models to their likely implications in New Energy research, including alternative interpretation of lowenergy reaction (coldfusion) phenomena. The authors explored some new approaches to describe novel phenomena in particle physics. M Pitkanen introduces his nuclear string hypothesis derived from his Topological Geometrodynamics theory, while E. Goldfain discusses a number of nonlinear dynamics methods, including bifurcation, pattern formation (complex GinzburgLandau equation) to describe elementary particle masses. Fu Yuhua discusses a plausible method for prediction of phenomena related to New Energy development. F. Smarandache discusses his unmatter hypothesis, and A. Yefremov …

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 …

Site Specificity In The Intercalation Of Antitumor Antibiotics With Dna, Martin Bradford Jones

Chemistry and Chemical Biology ETDs

Many planar molecules or molecules with planar moieties have been shown to bind to DNA by intercalation, which can be defined as the insertion of a planar moiety between adjacent bases on the DNA strand, reading in the 3'-5' direction, accompanied by a partial unwinding and elongation of the helix in the immediate vicinity of the intercalation site. Intercalation raises the question of specificity of binding of the drug to DNA, since there are 16 possible intercalation sites in normal double-stranded DNA. The conformational changes (elongation and unwinding) associated with intercalation make circular dichroism (CD) an excellent technique for studying …

The Synthesis Of C₄ And C₅ 13c-Labeled Benzo[A]Pyrene, Benzo[A]Pyrene-4, 5-Oxide And Derivatives. Studies Of The Reactions Of Benzo[A]Pyrene-4, 5-Oxide Using 13cnmr, Mark David Hylarides

Chemistry and Chemical Biology ETDs

Benzo[a]pyrene (BAP), BAP-4,5-oxide, and other derivatives which are 13c-labeled in the 4-and 5-positions were synthesized. The synthetic scheme involves an initial reaction of the lithioenolate of ethyl acetate-1-13c or ethyl acetate-2-13c with l,2-dihydrochrysen4(3H)-one. Subsequent dehydration and dehydrogenation gave ethyl 4-chryseneacetate-1-C (or 2-C). Partial reduction to the aldehyde 13 13 followed by cyclization gave BAP-5-C (and 4-C). Toe synchesis of 13 BAP-4,5-oxide-4-13c (and 5-c) involved saponification of ethyl 4-chryseneacetate-1-13c (and 2-13c), an intermediate in the synthesis of BAP, followed by cyclization of the resultant acid to BAP-5-ol13 s-c (and 4-13c). The crude phenol was oxidized to the o-quinone. Further reduction of …

Kinematics And Thermodynamics Of Nickel(Ii)-Glycine Complexes Using Carbon Magnetic Resonance, Donald Frederick Shepard

Chemistry and Chemical Biology ETDs

1-¹³C glycine was studied in nickel(II) solutions using carbon magnetic resonance (CMR). The carboxy bound nickel(II)-glycine complex and the kinetics of complexation between aquated nickel(II) ion and aquated glycine are described. It has been hypothesized that solutions containing no complexation higher than the chelated mono nickel(II)-glycine complex contain five magnetically different glycine species. The effects of these five magnetically different glycine species on the CMR spectra of the nickel(II)-glycine solutions are discussed. The lifetime of the carboxy bound complex is 7.87 x 10^-4 sec at 272 K with an activation energy of 9.74 kcal/mole, an activation enthalpy …

Synthesis Of Benzo[A]Pyrene And Derivatives: Labelling Of Positions 1, 2, 3, 11 And 12, Richard S. Bodine

Chemistry and Chemical Biology ETDs

The ketone, 3, 4-dihydrobenz[a]anthracen-1(2H)-one (1), was prepared in three steps from anthracene. Condensation of the lithioenolate of ethyl acetate with the ketone(1) in tetrahydrofuran at -78°C afforded ethyl (1-hydroxy-1, 2, 3, 4-tetrahydrobenz[a]anthracen-1-yl)acetate (2). Dehydration and dehydrogenation over palladium/charcoal provided ethyl (benz[a]anthracen-1-yl)acetate (3). Reduction of the ester (3) with diisobutylaluminum hydride in toluene at -75°C gave benz[a]anthracen-1-ylacetaldehyde (4) which was cyclized with methanesulfonic acid to benzo[a]pyrene (5). Saponification of the ester (3) gave benz[a]anthracen-1-ylacetic acid (6) which was cyclized with methanesulfonic acid to benzo[a]pyren-11-o1 (7). Oxidation of the phenol (7) with Fremy's salt afforded the quinone, 11, 12-dihydrobenzo[a]pyrene-11, 12-dione (8). Reduction …

The Electrogenerated Chemiluminescence Of Trans-Stilbene Derivatives, James R. Wilson

Chemistry and Chemical Biology ETDs

A group of 15 compounds, all structurally related to trans­stilbene have been studied in systems of electrogenerated chemiluminescence (ECL). The compounds are substituted 2-phenyl indenes, dihydronapthalenes, and dihydrophenanthrenes. Absorption and fluorescence spectra, fluorescence quantum yield, cyclic voltammetry, and ECL were obtained for each compound. The ECL experiments were set up as single and mixed systems which used tri­para-tolylamine as the source of cation radicals. Each mixed system was studied in two different solvents, which were acetonitrile and a 1:1 mixture of acetonitrile and benzene. Single systems were studied only in the acetonitrile-benzene solution. Emissions at wavelengths longer than the fluorescence …

Chemiluminescence Studies Of Silicon Fluoride And Uranium Oxide, Russell A. Armstrong

Chemistry and Chemical Biology ETDs

Spectroscopic studies of the reactions of fluorine with silicon, silane and deuterated silane, and of oxygen with uranium are reported. Chemiluminescence and atomic absorption techniques have been employed to determine the kinetics, photon yields and branching ratios of the chemistry leading to the excited states of the radical SiF. The reaction of silicon vapor with fluorine occurs at nearly a gas kinetic rate (k₂=1.3 x 10^-10 cc molecule^-1 sec^-1). The overall system photon yield from the reaction of silane and fluorine to produce SiF(A➔X) and SiF(a➔X) emission were 5 x 10^-2% and …

Comparative Enzymology Of Glyoxalase I, Christina Margaret Schimandle

Chemistry and Chemical Biology ETDs

The role of the metal ion in rat erythrocyte glyoxalase I was evaluated. The apoenzyme was formed by dialysis against an EDTA-imidazole buffer. Fluorescence studies of the Mg⁺⁺- and Mn⁺⁺-dansylated glyoxalase I's suggest that the metal ion is near the active site of the enzyme and participates in the catalytic reaction. Stereochemical studies of the conversion of methylglyoxal to S-lactoylglutathione with Mg⁺⁺, Mn⁺⁺, Co⁺⁺ and Ni⁺⁺-glyoxalase I's show that the 0-lactate of S-lactoylglutathione (97±1.5%) is formed. This result suggests that the reaction mechanism is the same with a change …

Physical Studies Of Hg(Ii) And Ag(I) Dna Complexes, Dawen Ding

Chemistry and Chemical Biology ETDs

The binding of Hg(II) and Ag(I) to the bases of DNA and polynucleotides induces strong absorption and CD bands. From electric dichroism studies, the transition moment of the difference absorption band at 293 nm is in the plane of the bases and has a huge negative CD band at 285 nm; while the corresponding 293 nm difference absorption band of DNA-Ag(I) complex is relatively CD inactive. A second band at 270 nm in the difference absorption spectrum of the DNA-Ag(I) complex has a large associated CD band at 270 nm. This transition is out of the plane of the bases. …

Synthesis And Studies Of A Carbon-13 Labelled Chemical Carcinogen, Robert E. Royer

Chemistry and Chemical Biology ETDs

Derivatives of 6-methylbenzo[a]pyrene enriched to 90% carbon-13 at the methyl carbon were synthesized. Reactions of the carcinogen, 6-chloromethylbenzo[a]pyrene, with nucleophiles under solvolytic conditions were studied kinetically and, using labelled 6-chloromethylbenzo[a]pyrene, the reaction products were studied by CMR. The purpose was to characterize the selectivity of the benzo[a]pyrenyl- 6-methyl carbonium ion in its reactions with some simple nucleophiles and with nucleosides and other nucleic acid components.

Although the solvolysis of 6-chloromethylbenzo[a]pyrene in aqueous/organic solution is first order, information about the course of the reaction can be obtained, under certain circumstances, from rate constants. Thus, if the rate of solvolysis is slowed …