Department: Chemistry ![[clear]](close-x.png "Remove this limiter")
24 matches in the database.
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1.
Alsulami, Rabah Nafa.
SYNTHETIC APPROACHES TO HETEROCYCLIC BICYCLO[2.1.0]PENTANES.
Degree: MS, Chemistry, 2011, Bowling Green State University
► Thomas H. Kinstle, Advisor Bicyclic systems such as bicyclo[2.1.0]pentanes and 5-oxabicyclo[2.1.0]pentanes are…
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▼ Thomas H. Kinstle, Advisor Bicyclic systems such as bicyclo[2.1.0]pentanes and 5-oxabicyclo[2.1.0]pentanes are known to display a variety of unique chemical properties associated with their high strain energy. To the best of our knowledge, there were no reports regarding synthesis and investigation of 5-azabicyclo[2.1.0]pentanes. Therefore, the initial goal of this research was synthesis of 5-azabicyclo[2.1.0]pentane and investigation of its chemical properties. The cycloaddition reaction of azides (58, 59, 61) to olefins (54, 55) with further elimination of nitrogen was chosen as a synthetic method in order to obtain the compounds of interest. Starting olefins (3,3-dimethyl-1-cyclobutene-1-carboxylic acid (54) and methyl 3,3-dimethyl-1-cyclobutene-1-carboxylate (55) and azides phenyl azide (58), p-toluenesulfonyl azide (59), and picryl azide (61) were successfully synthesized and characterized by NMR spectroscopy and GCMS spectrometry. The addition reaction between azides and olefins was performed under various conditions, such as different solvents and temperature; however, according to NMR spectroscopy and GCMS spectrometry, olefins (54, 55) do not undergo cycloaddition reaction with azides (58, 59, 61). In order to investigate that behavior, cycloaddition reactions of more reactive olefins (66, 68) with azides (58, 59, 61) were performed under a variety of conditions. The reaction of endo-bicycloheptene-2,3-dicarboxylic anhydride (68) with phenyl azide (58) in toluene at 80 0C resulted in successful formation of triazoline. Additionally, triazoline was formed in the reaction between norbornene (66) and picryl azide (61) in chloroform at room temperature.
Advisors/Committee Members: Kinstle, Thomas.
Subjects: Chemistry
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2.
Arutyunyan, Sergey L.
DESIGN OF MULTIFUNCTIONAL MOLECULE FOR TREATMENT OF ACNE SYNTHESIS OF SKIN SOLUBLE BENZOPHENONE PEROXYESTERS.
Degree: MS, Chemistry, 2005, Bowling Green State University
► Acne vulgaris is the most common skin disorder whose pathogenesis appears to…
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▼ Acne vulgaris is the most common skin disorder whose pathogenesis appears to be multifactorial. A synthetic scheme for a new multifunctional peroxyester compound for acne treatment was proposed and successfully completed. This compound (8) contains three parts which are expected to serve different functions. A tert-Bu perester moiety would serve as radical generating part for acne treatment. The benzophenone chromophore would photochemically control radical generation. Finally, the diethyleneglycol methyl ether part is expected to increase the skin affinity of the proposed molecule. Compound (8) shows characteristic absorption of the benzophenone chromophore with maxima at 348 and 256 nm. Combinatorial experiments were performed by reacting eight different alcohols with methyl 4-(4-bromomethylbenzoyl) benzoate (4) as the common substrate.
Advisors/Committee Members: Neckers, Douglas C.
Keywords: acne, peroxyesters, synthesis
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3.
Atoyan, Dina A.
CHARACTERIZATION OF THIN-FILM ZINC TELLURIDE ON GLASS PREPARED BY LOW-TEMPERATURE NANOSECOND PULSED-LASER DEPOSITION.
Degree: MS, Chemistry, 2006, Bowling Green State University
► This thesis employed pulsed-laser deposition (PLD) for the formation of zinc telluride…
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▼ This thesis employed pulsed-laser deposition (PLD) for the formation of zinc telluride (ZnTe) thin films on glass using 1064, 532, and 355 nm laser lines of a pulsed Nd:YAG laser. The thesis studied the influence of the ablation wavelength on morphology, microstructure, angular thickness distribution, and composition of the films. The morphology and microstructure of the films were analyzed by scanning electron microscopy (SEM) and field-emission SEM (FE- SEM). The thickness profiles of the films were studied by transmittance-reflectance measurements, and composition distributions were measured using energy-dispersive x-ray (EDX) analysis. The thickness distributions for the film prepared at 355 nm were fitted with Anisimov model, and three-dimensional (3-D) thickness profiles were simulated for different target-to-substrate distances. In addition, the deposition rates for various laser wavelengths were recorded with quartz crystal monitor, and the emission of the plasma plume was analyzed with in situ optical emission spectroscopy (OES).
Advisors/Committee Members: Ullrich, Bruno.
Subjects: Chemistry, Physical
Keywords: Zinc Telluride thin films, Pulsed-Laser Deposition
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4.
Bludin, Alexey O.
Peptide-Porphyrin Self-Assembled Materials.
Degree: MS, Chemistry, 2011, Bowling Green State University
► A 30-residue polypeptide AQPal14 that was designed to form a three-stranded coiled…
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▼ A 30-residue polypeptide AQPal14 that was designed to form a three-stranded coiled coil in aqueous solution contains a 4-pyridylalanine residue on its solvent-exposed positions. In the previously reported work, it was shown that the AQPal14 peptide can form directional bonds with the cis-positions of the Pt(ethylenediamine) (Pt(en)) linker and as a result form nanoscale globular and fibrillar assemblies. The current work describes how the reaction of the AQPal14 peptide with a linker having coordination preferences different from Pt(en) can affect the size and morphology of formed nanoassemblies. Specifically, a cobalt (III) protoporphyrin IX (CoPPIX) was chosen for this purpose since it can produces a six-coordinated CoPPIX(AQPal14)2 complex upon binding with AQPal14 in which two trimeric coiled coils of AQPal14 are bound to the axial positions of the porphyrin ring. It was found that conditions at which the AQPal14 peptide reacts with CoPPIX can affect the structure of the formed materials as well. Specifically, the self-assembly of AQPal14 and CoPPIX in unbuffered water leads to the formation of nanoscale globular assemblies having the morphology analogous to the AQPal14-Pt(en) structures. However, when AQPal14 reacts with CoPPIX in 20 mM phosphate buffer, pH 7, the millimeter-scale rod-like structures are formed. Formation of the nanoassemblies with similar morphology after the reaction of AQPal14 with either Pt(en) or CoPPIX suggests that the size and shape of the formed assemblies are not likely dictated by the coordination geometry of the linking compounds, but by the oligomerization state of the peptide. However, it was suggested that the formation of the rod-like structures does not depend on these factors and mostly depends on the crystallization of the phosphate ions in the presence of these compounds. To study the effect of the oligomerization state on the self-assembling properties and structure of the product materials, a new peptide AQPal14N16 whose sequence is based on the sequence of the original AQPal14 peptide was designed and synthesized. It was expected that a single modification in the AQPal14 sequence would not only change the oligomerization state of the new AQPal14N16 peptide from a trimer to a dimer, but also affect the size and shape parameters of the assembled nanostructures as well. As described in this work, it was found that the change in the oligomerization state does affect the morphology of the self-assembled AQPal14N16-CoPPIX nanoassemblies and also enhance the ability of these nanomaterials to further assemble into microscale fibrous systems.
Advisors/Committee Members: Ogawa, Michael Y.
Subjects: Analytical Chemistry; Biochemistry; Biomedical Engineering; Biomedical Research; Biophysics; Chemical Engineering; Chemistry; Inorganic Chemistry; Materials Science; Molecular Chemistry; Molecules; Morphology; Nanoscience; Nanotechnology; Organic Chemistry; Pharmaceutic
Keywords: peptides; proteins; porphyrins; peptide-porphyrin complexes; coiled-coils; self-assembly; circular-dichroism; light-scattering; nanomaterials; biomaterials; supramolecular structures; nanofibers; atomic force microscopy; scanning electron microscopy
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5.
Chakraborty, Saswata.
Mechanistic Study of Photo-bis-Decarbonylation of Alpha-Diketones.
Degree: MS, Chemistry, 2010, Bowling Green State University
► The photo-bis-decarbonylation, the Strating-Zwanenberg reaction, of several α- diketones has been used…
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▼ The photo-bis-decarbonylation, the Strating-Zwanenberg reaction, of several α- diketones has been used to synthesize polyacenes, including heptacene. An effort has been made in this thesis to study the mechanism involved in the photo-bisdecarbonylation process. A range of diketones has been studied. Among these it is believed that Bicyclo[2.2.2]octene-2,3-dione (3) goes through an alleged allylic rearrangement before the decarbonylation resulting from biradical intermediates. The allylic product is highly unstable, and may be characterized only by absorption and IR spectroscopy. Aside from 3, none of the other polyacene precursors have shown this property. 2,3,9,10-Tetrabromo-6,13-dihydro-6,13-ethanopentacene-15,16-dione (14) exhibited dimer formation upon irradiation, and trapping of the biradical of 2,3,9,10- Tetra(2-methylphenyl)-6,13-dihydro-6,13-ethanopentacene-15,16-dione (13) with an acrylate monomer has been shown using MALDI-TOF. Other α-diketones provided no mass spectroscopic evidence when the trapping experiments were performed, explained by the short lifetime of the biradicals produced. The observations and results discussed will give us an insight into the photo-bis-decarbonylation process.
Advisors/Committee Members: Neckers, Dr. Douglas.
Subjects: Chemistry
Keywords: acrylate; biradical; α-diketones; NMR; 1H NMR; NMR Spectra; irradiation
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6.
Dahanayaka, Sudath A.
PROBING THE BINDING OF ESTROGEN AND GLUCOCORTICOID RECEPTORS ON CLASSICAL AND NON-CLASSICAL RESPONSE ELEMENTS AND INFLUENCE OF HMGB-1.
Degree: MS, Chemistry, 2007, Bowling Green State University
► Estrogen receptor (ER) is a ligand-inducible enhancer protein that is a member…
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▼ Estrogen receptor (ER) is a ligand-inducible enhancer protein that is a member of nuclear hormone receptor super family. Estrogen receptors share a highly conserved structure with other members of the steroid receptor super family and a common mechanism, regulating gene transcription. Estrogen receptors reside in the nucleus and in the absence of hormone signal bind to other proteins. However, in the presence of hormone, the receptor dissociates from the other proteins and dimerizes. The dimeric form of estrogen receptor is the active form which binds to a specific DNA sequence, known as the estrogen response element (ERE) in the regulatory region of the target gene. The estrogen response element (ERE) consists of asymmetric or pseudo asymmetric, palindromic repeat of two half-site sequences (cHERE) 5’-AGGTCA-3’, separated by 3bps. HMG domain proteins are architectural proteins involved in chromatin function and have been shown to stabilize the ER/ERE binding. One aims of this thesis is to determine how differences in spacer length between the ERE half-site affect on ER binding affinity in the presence and absence of the coactivator protein, HMGB-1. The binding affinity and selectivity of the two forms of the estrogen receptor (á and â) and glucocorticoid receptor (GR) for cHERE, in three different orientations (direct repeats, inverted repeats and everted repeats) were studied by using the gel mobility shift assay (EMSA). ERs, in contrast to GR, showed a strong cooperativity when interacting with direct repeats, inverted repeats as well as everted repeats.
Advisors/Committee Members: Scovell, William M.
Subjects: Chemistry, Biochemistry
Keywords: HMGB-1; ERα; ERβ; presence of HMGB-1; absence and presence of HMGB-1; cERE; BINDING
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7.
Hong, Jing.
DESIGN, CHARACTERIZATION, AND ELECTRON TRANSFER PROPERTIES OF SYNTHETIC METALLOPROTEINS.
Degree: PhD, Chemistry, 2006, Bowling Green State University
► The binding of Cu(I) to the random coil peptide C16C19-GGY produces a…
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▼ The binding of Cu(I) to the random coil peptide C16C19-GGY produces a self-organized metal-peptide assembly which displays an intense room-temperature luminescence at 600 nm. It was shown that this synthetic metalloprotein exists as a 4-helix bundle which contains a cyclic Cu 4 S 4 cofactor in which each Cu(I) atom is bridged by two cysteine residues and has a terminal N/O ligand. The strong luminescence of the Cu(I) protein suggests that it might function as a photoinduced electron-transfer agent. The emission follows biexponential decay kinetics with t 1 = 1.0 µsec and t 2 = 7.5 µsec. These components have approximately equal amplitudes and the results indicate that the Cu 4 S 4 cofactor contains two independent lumophores. Both lifetime components are quenched by a series of [Ru(NH 3 ) 5 L] 3+ (L = chloro, amine, lutidine, pyridine, nicotinamide, and 3,5-dimethyl pyridine dicarboxylate). The quenching mechanism is assigned to a photoinduced electron-transfer event by transient spectroscopy. The results show the occurrence of bimolecular forward electron-transfer in the inverted Marcus regime. Electron-transfer (ET) reactions occur between a negatively charged cyclic metallopeptide [Ru(bpy) 2 (phen-am)-cyclo(Cys-Glu-D-Glu-Glu-Pro-Glu-D-Glu)] 3- = Rucyclic, and ferricytochrome c, in which an acetamido linker was used to attach the ruthenium polypyridyl complex to the cysteine side chain of a head to tail cyclic peptide. In the presence of cyt c, the triplet state of ruthenium metallopeptide decays via parallel pathways that involve two different encounter peptide-protein complexes. That the electron transfer rate constants of both encounter complexes decrease with increasing viscosity demonstrates that the kinetics are gated by rate-limiting configurational changes occurring within the complexes. NMR experiments confirm that two separate conformations exist for Rucyclic. Metallopeptides, 5-Chloro-PhenRuCE5G with a different redox potential but a similar conformation with those of RuCE5G give different driving forces of the excited-state ET reaction. The reorganization energy (λ) and donor-acceptor separation (r) of the preformed complex between metallopeptides and cyt c are determined to be 1.25 eV and 16.4 Å by measuring the actual electron transfer rates of these four metallopeptides at their most stable configurations. These values are comparable with those of some protein-protein systems reported previously.
Advisors/Committee Members: Ogawa, Michael Y,.
Subjects: Chemistry, Inorganic
Keywords: ELECTRON TRANSFER, METALLOPROTEIN
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8.
Katkova, Olga A.
Photochemical Isomerization and Stereoselective Thermal Reactions of Conjugated Nitrones.
Degree: MS, Chemistry, 2005, Bowling Green State University
► Nitrones have been known for some time as quite versatile intermediates in…
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▼ Nitrones have been known for some time as quite versatile intermediates in organic synthesis. They have been employed for stereoselective formation of synthetically useful isoxazolidines by their 1,3-dipolar cycloaddition reactions with alkenes. We have further investigated the behavior of some non-conjugated and conjugated nitrones in cycloaddition reactions. Several α nitrones were synthesized and characterized. New reactions with electron-rich butylvinylethers were studied. All the synthesized nitrones were shown to undergo 1,3 dipolar cycloaddition with formation of 4- and 5-substituted isoxazolidines. We successfully synthesized a trans-chelating tridentate ligand (R,R)-4,6-dibenzofurandiyl-2,2'-bis(4-phenyloxazoline) (DBFOX/Ph) and converted it to the cationic aqua complex Ni(ClO 4 ) 2 *PhDBFOX. This complex was previously described by Kanemasa 47 as the most selective chiral catalyst for the normal electron-demand 1,3-dipolar cycloaddition reaction between nitrones and alkenes. We studied the effect of this catalyst on reactivity of α and α A separate study of the photolysis of these non-conjugated and conjugated nitrones proved the formation of oxaziridines. The structure of these 3-membered ring nitrone isomers was established by NMR analysis. Oxidation of oxaziridines with peroxides was briefly investigated.
Advisors/Committee Members: Kinstle, Thomas H.
Subjects: Chemistry, Organic
Keywords: synthesis of nitrones; ptochemical reactions of nitrones; 1,3 Cycloaddition reactions of nitrones
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9.
Klinkova, Anna.
Cation Exchange Reactions in Semiconductor Nanocrystals.
Degree: MS, Chemistry, 2011, Bowling Green State University
► Chemical transformation of existing inorganic nanostructures from one material into another by…
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▼ Chemical transformation of existing inorganic nanostructures from one material into another by means of cation exchange represents a straightforward, facile, and effective approach to nanomaterial synthesis. This approach has received increasing attention in recent years. The general overview of recent developments in synthesis and chemical modification of nanomaterials with a focus on cation exchange reactions is presented in the chapter I of this work. Subsequently, two projects of our research group, which employ this method for synthetic purposes, are being described. First, a simple strategy for low-temperature processing of colloidal nanocrystals into all-inorganic solid films, deployable for photovoltaic applications, is presented. The method relies on encapsulation of semiconductor nanocrystal arrays with a matrix of a wide-band gap inorganic material, which preserves optoelectronic properties of individual nanoparticles, yet, renders the nanocrystal film highly photoconductive. Second, hot-injection synthesis of colloidal nanocrystals (NCs) in a substrate-bound form is demonstrated. We show that polycrystalline films submerged into hot organic solvents can nucleate the heteroepitaxial growth of semiconductor NCs, for which the ensuing lattice quality and size distribution are on the par with those of isolated colloidal nanoparticles. This strategy is demonstrated by growing lead chalcogenide NCs directly onto solvent-submerged TiO2 substrates. The resulting PbS/TiO2 nanocomposites exhibit heteroepitaxial interfaces between lead chalcogenide and oxide domains and show an efficient separation of photoinduced charges, deployable for light-harvesting applications. The extendibility of the present method to other material systems was demonstrated through the synthesis of CdS/TiO2 and Cu2S/TiO2 heterostructures, fabricated from PbS/TiO2 composite via cation exchange.
Advisors/Committee Members: Kinstle, Thomas.
Subjects: Chemistry
Keywords: nanochemistry; quantum dots
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10.
Leontyev, Alexey E.
Carbazole-Fluorenone Dyes.
Degree: MS, Chemistry, 2009, Bowling Green State University
► Two structures of dyes were designed for dye sensitized solar cells. Both…
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▼ Two structures of dyes were designed for dye sensitized solar cells. Both compounds were synthesized and spectroscopically characterized. It was found that they meet major requirements for devices implication. The role of phenylacetylene bridge linker was studied.
Advisors/Committee Members: Neckers, Douglas.
Subjects: Chemistry
Keywords: carbazole; fluorenone; dye; solar cell
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11.
Nikolaeva, Ekaterina S.
SYNTHESIS AND CHARACTERIZATION OF NEW TETRAALKYLBORATE INITIATORS FOR NOVEL POLYMERIZATION APPLICATIONS.
Degree: MS, Chemistry, 2006, Bowling Green State University
► A system has been developed which carries out the radical polymerization of…
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▼ A system has been developed which carries out the radical polymerization of acrylic esters without direct use of light and/or heat (designated as Remote Cure). This approach may represent a significant innovation in the area of coatings. A novel feature of the proposed system design is to bring the active component of the initiating mixture in a flow of a carrier gas which has unrestricted access to the entire surface of the coating. When brought in contact with the surface, the active ingredient(s) of the curing gas (H2O2 vapor) react with the active coating component(s) (tetraalkyl borate salts) to generate free radicals and initiate the polymerization within the coating. The thesis presents the synthesis and characterization of symmetric and asymmetric tetraalkyl borates used as initiators for remote cure. Some of them are known - NBu4BBu4, NBu4BPhBu3 and NBu4BBuPh3, and some of them have been synthesized for the first time - NBu4BEt4, NBu4B(iPr)4, NBu4BBuEt3 and NBu4B(iPr)Et3. Studies of these borate salts were conducted with the emphasis on their relative reactivity in the Remote Cure process and mechanistic considerations. In Situ studies by FTIR Spectroscopy proved that borate salts, when activated by H2O2 vapors, showed good reactivity in the remote cure process. ATR FTIR studies were made using different peroxides. Only H2O2 showed good remote polymerization activity. From the results of electrochemical experiments, oxidation potentials were determined. These potentials helped to explain the observed reactivity of borate salts in the remote polymerization. In addition, nanosecond laser flash photolysis experiments were conducted to aid our understanding of the remote cure. The mechanism for remote cure process has been proposed. The results of radical trapping experiments obtained using GC, GCMS, and NMR allowed us to confirm the proposed mechanism where tetraalkyl borate is being oxidized by H2O2 to produce alkyl radical and trialkylborane, with the former adding to acrylic double bond to start the chain polymerization.
Advisors/Committee Members: Neckers, Douglas C.
Subjects: Chemistry, Polymer
Keywords: radical polymerization; initiator; remote cure; tetraalkylborate salts
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12.
Novikova, Irina V.
Paranemic and Receptor-Loop RNA Motifs: Versatile Interactions for Biosensing Platforms and Nanotechnology Scaffolds.
Degree: PhD, Chemistry, 2010, Bowling Green State University
► RNA has favorable properties for use as a medium for constructing multivalent,…
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▼ RNA has favorable properties for use as a medium for constructing multivalent, modular nanoparticles to deliver therapeutic agents targeting virus-infected or cancer cells or for serving as scaffolds to organize the matter at nanoscale. RNA nanoparticles possessing diverse functionalities can be engineered to self-associate via interaction motifs to increase their in vivo stability and propensity for cellular uptake or form various materials of fibrous architecture. High affinity and specificity RNA-RNA binding interfaces can be constructed by combining pairs of GNRA loop/loop-receptor interaction motifs. By fusing these RNA interactions and 4-way junction motifs, we have developed tecto-RNA complexes possessing favorable properties for drug delivery applications such as enhanced nuclease protection and hetero-multimerization amenability desirable for multi-functionality aims. We demonstrated that these RNA molecules can be programmed for uncompensated assembly to form closed, ring-shaped complexes of defined and predictable stoichiometries that assemble cooperatively. We provided a step-by-step description how the stoichiometry can be controlled at the RNA monomer level from ring-closed dimeric, trimeric and tetrameric complexes to polymeric structures where ring formation is no longer possible. Structure-probing studies of optimally designed dimer and trimer complexes provided strong experimental evidence that RNA systems self-associate as intended by design. Detailed thermodynamic analysis of tecto-RNA self-assembly allowed us to disclose the binding affinities, to quantify the cooperativity of assembly and to elucidate the energy of four-way junction conformational adjustments for interaction. Alternative interaction motifs such as paranemic crossover (PX) motifs provide specific, programmable and reversible binding interactions between pre-folded nucleic acid molecules. We explored their potential for RNA biosensing and RNA nanotechnology applications. Sequence-specific, label-free RNA biosensors targeting pre-folded internal loop motifs were constructed by coupling paranemic binding motifs to a Malachite Green aptamer. We showed that this binding is sequence-specific as single-basepair mismatches in the paranemic binding motif disrupt the sensor-target interaction. We also explored the use of the paranemic motif as a cohesion tool for engineering linear RNA fibrils and for recognition of asymmetric, artificially-designed and natural internal loops.
Advisors/Committee Members: Leontis, Neocles.
Subjects: Chemistry
Keywords: tecto-RNA; receptor-loop motifs; paranemic motifs; nanotechnology
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13.
Obali, Derya.
Synthetic Approaches To Fluorinated Ten-Membered Enediyne.
Degree: MS, Chemistry, 2010, Bowling Green State University
► Enediynes are the most potent antitumor agents ever discovered. This antibiotic family…
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▼ Enediynes are the most potent antitumor agents ever discovered. This antibiotic family is represented by Calicheamicin, Esperamicin A1, Neocarzinostatin, and Dynemicin A. With the exception of Neocarzinostatin, all of these molecules contain a 1,5-diyne-3-ene unit within a strained ten-membered ring. Apart from their diversity, enediyne compounds share some structural and functional similarities. Their unique mode of biological action is to destroy double-helical DNA by double strand scission, caused by H-atom abstraction from the sugar phosphate backbone of both duplex DNA strands by a 1,4-benzenoid diradical formed as a reactive intermediate in the Bergman cyclization of the enediyne. Unfortunately the DNA cleavage observed is very non-selective so modified enediynes with more controlled Bergman reactivity must be developed. In this thesis, we describe synthetic schemes designed to create uniquely substituted enediyne structures in hopes of developing a more thorough understanding of the Bergman reaction.
Advisors/Committee Members: Kinstle, Thomas H.
Subjects: Chemistry
Keywords: Bergman reaction, enediyne
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14.
Orlov, Alexander G.
Synthesis of Diazirine-Functionalized Organic Semiconductor Materials.
Degree: MS, Chemistry, 2012, Bowling Green State University
► Organic light-emitting diodes (OLEDs) could become the leading technology for fabrication of…
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▼ Organic light-emitting diodes (OLEDs) could become the leading technology for fabrication of next generation displays and solid state lightening in the near future. To meet this goal, cheap and easy methods of OLEDs fabrication have to be developed. Modern OLEDs are generally prepared by multiple layer deposition. Vacuum deposition is the most common method of building such multilayer structure but it is costly and limited to vaporizable low molecular weight materials. By contrast, solution-processing technologies are much easier, less costly, and suitable for flexible display applications. A potential disadvantage of such techniques for fabricating multilayer devices is that preexisting layers could be partially dissolved by the solvent used in one of the following deposition steps. To overcome this problem, the cross-linking concept can be applied. This thesis pursues investigation on diazirine-functionalized semiconductor materials, which can be transformed to insoluble layers by photo- or themo-cross-linking. In particular, it focuses on its synthesis, optical and electrochemical characterization, polymerization, and first application in an OLED device. α-NPD, a commonly used hole-transport material, triphenylamine, diphenyl ether, bromo- and iodo-benzene were functionalized with diazirine groups within this work. Diazirine compounds undergo decomposition reaction (irreversible nitrogen loss) upon UV irradiation or pyrolysis forming highly reactive carbenes, which display high propensity for intermolecular bond insertions to form a polymer. Since the cross-linking is induced by UV light, the organic films become, not only insoluble, but can simultaneously be patterned as a negative photoresist using standard photolithography techniques. Photo patterning capability of diazirine-functionalized compounds may be advantageous for future OLEDs applications.
Advisors/Committee Members: Anzenbacher, Jr., Pavel.
Subjects: Chemistry
Keywords: OLED; cross-linking; photo-patterning; organic semiconductors; diazirine
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15.
Pinnawala Arachchilage, Gayani Wasana Premathilake.
Part I: Design and Synthesis of Organic Materials for Dye Sensitized Solar Cells Part II: Qualitative and Semi-Quantitative Study of the Behavior of Surfactant on Crude Oil Recovery Processes.
Degree: MS, Chemistry, 2010, Bowling Green State University
► The design and synthesis of new π-conjugated organic materials are currently at…
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▼ The design and synthesis of new π-conjugated organic materials are currently at the forefront of research in order to realize stable and efficient organic electronic devices. Linear hydrocarbons and carbazole based materials are examples of π-conjugated organic systems widely studied for electronic applications. Structural modifications increase the stability, improve the solubility, and improve the thin film packing and mobility compared to the parent substances. The electronic, physical, and photophysical properties of carbazole based materials in particular, can be easily modified by changing the substitution pattern on the main carbon skeleton. Carbazole containing compound 1 shows an absorption maxima at 425 nm in dichloromethane and it is weakly soluble in other common organic solvents. This compound shows very weak emission. An alcohol dimerization process known as the Guerbet reaction is used to create large alcohol structures for the production of the corresponding alkoxy sulfate surfactants. In the alcohol industry, Guerbet (dimer) alcohols are considered the “gold” standard for large, branched alcohols. These Guerbet alcohols tend to be more expensive than other alcohols when produced in high purity for various industrial applications. The high cost is mainly due to driving the reaction to completion and/or removing the unreacted monomer alcohol to produce high purity product. However, inexpensive Guerbet alcohols (GA) can be prepared by aiming for less than quantitative conversion during the alcohol dimerization process. The resultant blend of 85-95% GA and 5-15% monomer alcohol is subsequently used in the alkoxylation process to add propylene oxide and/or ethylene oxide, followed by sulfation. Obtaining both ultra-low interfacial tension and low microemulsion viscosity when the equivalent alkane carbon number of the crude oil is high requires surfactants with very large hydrophobes and branched structures. Through the use of this new Guerbet process, these surfactants can be manufactured at low cost when made as sulfates as opposed to sulfonates. For example, a C32 GA can be produced from a C16 alcohol. This is a breakthrough in lowering the cost of surfactant flooding in high-temperature, high-salinity oil reservoirs because such surfactants are very salinity and temperature tolerant and cost much less than alkoxy sulfonates. Numerous microemulsion phase behavior and core flooding experiments at high temperatures carried out using the Guerbet alkoxy sulfates with appropriate co-surfactants show ultra-low interfacial tension, low microemulsion viscosity and high oil recoveries for target reservoir crude oil. This breakthrough in surfactant technology will both greatly increase the number of oil reservoirs where chemical EOR (surfactant-polymer, alkaline-surfactant-polymer and wettability alteration processes) is applicable and greatly improve its performance and robustness.
Advisors/Committee Members: Kinstle, Dr. Thomas.
Subjects: Chemistry
Keywords: Dye Sensitized Solar Cells; Surfactant; Crude Oil Recovery Processes
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16.
Rodrigo, Udaya Indike.
ULTRAFAST PHOTOEXCITATION STUDIES OF CONCENTRATED SOLUTIONS OF ALKALI METAL HALIDES.
Degree: MS, Chemistry, 2006, Bowling Green State University
► The primary photochemical processes that occur via a two photon mechanism in…
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▼ The primary photochemical processes that occur via a two photon mechanism in pure water during high intensity excitation with a femtosecond pulse at 267 nm were studied by using a white light continuum as probe pulse. Two photon femtosecond laser studies of the excitation and relaxation of pure water showed that, geminate lifetimes were comparable with reported data but the recorded absorption spectrum was blue shifted. Experiments carried out for highly concentrated lithium compounds with different anion indicated that these compounds produced their maximum transient absorption between the wavelengths of 550nm to 700nm. The time profiles of these compounds fell into two major categories. LiI and LiOH showed different kinetic profiles from the others by the initial presence of a short lived species along with longer decay kinetics, where as LiCl, LiBr and LiClO4 shows typical decay kinetics of long lived species only. The fitted experimental data on single exponential function for absorption kinetics of LiCl showed that the absorption rise time falls into same time regime as reported for the purported three body complex of NaCl. This leads to the thought that LiCl may follow the same mechanism. The concentration dependence study of LiCl showed its absorption maxima were red shifted as the concentration was changed from high to low. The kinetic data revealed that rate of absorption for low concentrated solution of LiCl is higher than that of high concentrated LiCl solution. The comparison of LiCl with KCl and NaCl showed that there is a significant contribution from the cation for higher concentrated solution to alter their kinetic and transient absorption. But in the case of low concentrated solutions that effect is not significant.
Advisors/Committee Members: Rodgers, Michael A.J.
Subjects: Chemistry, Radiation
Keywords: LiCl; absorption; transient absorption; Hydrated Electrons; Solvated Electrons
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17.
SARPONG, YAW A.
THE BINDING OF ESTROGEN, PROGESTERONE AND GLUCOCORTICOID RECEPTORS TO THEIR RECOGNITION SITES IN A NUCLEOSOME AND THE EFFECT OF HMGB1 ON THE BINDING AFFINITY.
Degree: MS, Chemistry, 2006, Bowling Green State University
► The eukaryotic genome is packaged in a chain of nucleosomes called chromatin.…
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▼ The eukaryotic genome is packaged in a chain of nucleosomes called chromatin. For transcription to take place in chromatin, RNA polymerase II, transcriptional activators and general transcription factors must interact with their binding sites in the regulatory region of specific genes. When these sites occur in nucleosome, the binding of the transcription factors (TF) is generally reduced drastically and in some cases, may not even bind to these regulatory sites. It therefore follows that, for the TFs to bind, the DNA must be remodeled or moved out of the nucleosome, or the contacts between the histone protein and DNA must be weakened by some mechanism. It has been previously reported that estrogen receptor (ER) binds to its recognition site when in a nucleosome in a dose dependent manner. We find, however, that ER does not bind even at the highest ER concentration of 160 nM. We show that estrogen receptor does not bind to estrogen response element (ERE) when DNA is reconstituted in a nucleosome. However, the ubiquitous protein, high mobility group box-1 (HMGB1) protein relieves ER binding repression and allows ER to bind with a dissociation constant (K¬D) of about 60 nM. We also find that ER binds to 2 different translationally positioned ERE on the nucleosome with the same K¬D values in the presence of HMGB1 protein. We suggest that HMGB1 protein does not strip the nucleosome off the DNA but rather makes the contact between the histone and DNA weaker to allow ER to bind. We show that HMGB1 protein does not form a stable part of the complex formed when ER binds to DNA and (or nucleosome). Our data indicate that glucocorticoid receptor (GR) acts more like a “bubble gum” because it binds to all DNAs and nucleosomes that we tested, with a KD of approximately 2.5 nM. HMGB1 protein does not have any significant effect in enhancing the binding affinities for GR. PR binds to glucocorticoid response element (GRE) with a KD value of 2.5 nM. The binding affinity is enhanced in the presence of HMGB1 protein to a low KD of 0.9 nM. However, when GRE was reconstituted into a nucleosome, PR fails to bind even in the presence of HMGB1 protein.
Advisors/Committee Members: Scovell, William.
Keywords: receptor binding in nucleosomes and effect of HMGB1
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18.
Sun, Yali.
Sensitizer Molecule Engineering: The Development Of Novel Ru(II) Polypyridyl Complexes for Application in Dye Sensitized Solar Cells.
Degree: PhD, Chemistry, 2009, Bowling Green State University
► Three series of hydrophobic ruthenium(II) polypyridyl sensitizers for DSSC application with the…
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▼ Three series of hydrophobic ruthenium(II) polypyridyl sensitizers for DSSC application with the molecular structure Ru(N^N)(Hdcbpy)X2, [Ru(N^N^N)(H2dcbpy)X]+/2+ and [Ru(N^N)2(H2dcbpy)]2+ were designed and synthesized in this dissertation. Their absorption maxima and molar extinction coefficients were tuned with the variation of the coordinated polypyridyl ligands. Fundamental photophysical and electrochemical studies were carried out by using a battery of available techniques including absorption, luminescence spectroscopy, lifetime, and cyclic and differential pulse voltammetry to clarify the effect of ligand electronic structure on photophysical properties and redox properties of relevant spectroscopic orbitals of these complexes. Initial photovoltaic performance of their associated solar cells, including the incident photon to current efficiency (IPCE), the short circuit current density (Isc), and the open circuit voltage (Voc), were evaluated upon 514.5 nm illumination (7.3 W/m2). Density functional theory (DFT) calculations were carried out for three particular sensitizers to explore the relationship between the photovoltaic performance and the sensitizers’ molecular structure. From the combination of the theoretical and experimental approaches, the “antenna” in the HOMO, such as NCS- or CN-, is critical to the design of sensitizers for efficient photovoltaic performance in DSSC application. Regardless of their strong absorption in the visible region of the spectrum, the Ru(II)/pyrene chromophores yield low single wavelength conversion efficiency due to postulated competing intramolecular processes such as triplet energy transfer to pyrene. Among the selected promising sensitizers, the synthetically facile heteroleptic ruthenium(II) sensitizer (NBu4)[Ru(4,7-dpp)(Hdcbpy)(NCS)2], coded as YS5-b, produces broad, high extinction coefficient MLCT bands spanning the visible spectrum. In operational liquid junction-based DSSCs under simulated global AM 1.5 sunlight (100 mW/cm2), this sensitizer routinely outperforms all “N719” cells measured in parallel, producing an optimum efficiency of 7.21% with a maximum IPCE value 73% at 540 nm. Furthermore, this dissertation attempts to demonstrate the plausibility of applying scalable, economical, and “green” microwave-assisted chemistry to ruthenium(II) sensitizer synthesis, yielding complexes with high purity which can be prepared in minutes with minimal or no purification required. The efficient and rapid synthetic methodologies under mild microwave irradiation operating at atmospheric pressure were developed for the heteroleptic ruthenium(II) sensitizers or synthons for DSSC applications. These methods remarkably shorten the reaction time and lower the reaction temperature of all procedures investigated. Additionally, the simplified purification procedures and several multi-step reactions proceeding flawlessly in a single pot were also realized. The combined results suggest that microwave-assisted chemistry is indeed a valuable tool as far as ruthenium(II) coordination chemistry is concerned and can likely be applied in the combinatorial pursuit of new dyes bearing sensitive functionalities.
Advisors/Committee Members: Castellano, Felix.
Subjects: Chemistry
Keywords: Dye sensitized solar cells; Ru(II) polypyridyl complexes; Sensitizers; Microwave Synthesis
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19.
Tive, Emmanuel.
Synthetic Approaches to 1,2-bis (3,3,3-trifluoropropynyl) Benzene.
Degree: MS, Chemistry, 2008, Bowling Green State University
► Among the many chemical substances investigated as anticancer chemotherapeutic agents, the enediyne…
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▼ Among the many chemical substances investigated as anticancer chemotherapeutic agents, the enediyne containing anticancer antibiotics, such as calicheamicin, exhibit a unique mechanism of action with a powerful cytotoxicity level. Unfortunately, their selectivity for only cancer cells is not adequate for their clinical application. Much research is underway to develop appropriate analog molecules possessing more useful behavior. This thesis describes a synthetic approach to a group of molecules that will be employed in studies to understand the basic factors which control the rate of Bergman cycloaromatization of conjugated enediynes, the unique reaction which is responsible for the cell killing proprieties of these substances. Specifically, this work describes synthetic pathways employed to provide information of the behavior of 1,2-bis(3,3,3-trifluoropropynyl) benzene.
Advisors/Committee Members: Kinstle, Dr. Thomas H.
Subjects: Chemistry
Keywords: enediyne; Bergman cycloaromatization of conjugated enediynes
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20.
Vahile, Sachin D.
Synthesis, Characterization and Photochemical Study of Potentially Emitting Tetrazine Derivatives.
Degree: MS, Chemistry, 2009, Bowling Green State University
► Tetrazines are aromatic compounds that consist of a six membered ring containing…
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▼ Tetrazines are aromatic compounds that consist of a six membered ring containing four nitrogens. They are not as much explored as light emitting materials as compared to other common organic compounds. Still they are likely to be important for as substrates for HEDM (High Energy Density Materials), sensors (for anions), important chromophoric materials (absorption and emission wavelengths in distinct regions), fluorescent probes (gives color to an organic compound) and possible day to day standard and useful organic molecular reference in photo physical studies. Much research still needs to be done on tetrazines in order to understand comparisons with the benzene ring with regard to reactivity, electron affinity, and photooptical properties as well as reaction mechanisms, as well as different types of reactions.A series of tetrazine derivatives with varying substitution patterns were successfully synthesized, characterized and preliminary photochemical studies were performed using them. Special quantitative 13C NMR techniques were employed in characterizing these compounds. Their emission wavelengths were found to be independent of the excitation wavelength. Longer singlet excited state life times of monosubstituted tetrazines were obtained which may be due to the formation of an intramolecular charge transfer state. A study of solvent effect based on polarity on these life times would be interesting to characterize the nature and stability of the formed charge transfer state.
Advisors/Committee Members: Anzenbacher, Pavel.
Subjects: Organic chemistry
Keywords: Tetrazines, Photochemistry, Substitution
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21.
Wilke, Bryn.
UPCONVERTING LOW POWER PHOTONS THROUGH TRIPLET-TRIPLET ANNIHILATION.
Degree: MS, Chemistry, 2012, Bowling Green State University
► One mechanism to achieve photon upconversion, the frequency conversion of low energy…
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▼ One mechanism to achieve photon upconversion, the frequency conversion of low energy photons to those of higher energy, is sensitized triplet-triplet annihilation, a non-coherent (lasers not required) process. In this scheme, a triplet sensitizer is selectively excited at long wavelengths, eventually transferring its triplet energy to an appropriate acceptor molecule in a bimolecular energy transfer reaction. Finally, a second bimolecular energy transfer reaction occurring between two excited triplet acceptors pools the combined energy onto one molecule, producing the fluorescent excited singlet state of the acceptor molecule. This energized molecule radiatively decays back to its ground state releasing photon energies in excess of that of the excitation source, i.e. upconverted with respect to the incident light. This phenomenon has become realized in various combinations of chromophores resulting in wavelength shifting properties that range from the UV to the near-IR. Recently, the upconversion process has become a viable solution to drive fuel-forming chemistry in photoelectrochemical cells and for display applications in polymer host films. The concepts and experiments related to photon upconversion are facile and readily present an opportunity to educate young chemists in this field. Related to established green-to-blue upconversion systems, [Ru(bpy)3](PF6)2 and 9,10-diphenylanthracene (DPA) in deoxygenated dichloromethane is demonstrated here to be a suitable composition for an undergraduate laboratory experiment in physical and/or inorganic chemistry using a conventional fluorimeter. Quadratic incident light power dependence is displayed from the singlet fluorescence of DPA (λem max = 430 nm) resulting from selective excitation of [Ru(bpy)3]2+ at 500 nm using a conventional single photon counting fluorimeter equipped with a 75 W Xe arc lamp. This is easily justified by the fact that two sensitized triplets must be formed in order to ultimately generate the singlet fluorescence. The nonlinearity of the power dependence establishes that the photon upconversion was indeed produced from sensitized TTA. Notably, this experiment can be further developed using higher light excitation intensities or sensitizer concentrations or vacuum degassing conditions to gain access to the linear incident power regime. Some of these aspects were also explored in this thesis. In the quadratic incident power regime, the kinetics illustrates a process where the pseudo-first order decay pathways for the triplet state of the acceptor dominate over the bimolecular triplet-triplet annihilation rate whereas a linear power dependence on the upconversion signal is observed when the pseudo-first order decay pathways are rendered slower with respect to the annihilation rate. The efficiency of the triplet sensitization (quenching) reaction can be determined at any quencher concentration and was analyzed and optimized using the Stern-Volmer relation. This thesis builds upon previous research to formulate an experiment in photon upconversion suitable for an undergraduate laboratory and presents new research supporting the weak and strong annihilation limits displayed through incident light power dependence exclusively using non-coherent photons.
Advisors/Committee Members: Castellano, Felix.
Subjects: Chemistry
Keywords: Inorganic Chemistry; Physical Chemistry; Laboratory Instruction; Photochemistry; Fluorescence Spectroscopy; Fluorescence Quenching; Chemical Kinetics; Quantitative Analysis; Photon Upconversion
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22.
Yarnell, James E.
Exploring the Photophysics of [Re(PNI-Phen)(CO)3Cl].
Degree: MS, Chemistry, 2010, Bowling Green State University
► This thesis describes the synthesis and photophysics of a new Re(I)-carbonyl diimine…
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▼ This thesis describes the synthesis and photophysics of a new Re(I)-carbonyl diimine complex, [Re(PNI-phen)(CO)3Cl], where the PNI-phen is N-(1,10-phenanthroline)-4-nitronaphthalene-1,8-dicarboximide. The PNI chromophore effectively sensitizes the metal-to-ligand charge transfer (MLCT) state through efficient Förster-type singlet energy transfer. This complex exhibits extended MLCT emission lifetimes as a result of having triplet ligand-centered (3LC) states nearly isoenergetic to the 3MLCT states. Once the excited-state is in the triplet manifold, a thermal equilibrium is achieved between the 3LC and the 3MLCT states. This equilibrium increases the MLCT emission lifetime approximately 3000-fold at room temperature relative to the MLCT model complex, [Re(phen)(CO)3Cl]. Thermal equilibrium is lost at 77 K since the emission decays independently from both the 3LC and 3MLCT states. Temperature dependent photoluminescence experiments estimate the energy gap between the two triplet excited states to be about 1500 to 1600 cm-1 at room temperature. The evolution of excited-states formed following the original Frank-Condon state excitation are studied using a number of techniques including transient absorption, time-resolved infrared, and time-resolved photoluminescence spectroscopy. These instrumental techniques allow us to monitor the excited-state dynamics ranging from the femtosecond to the millisecond time domain.
Advisors/Committee Members: Castellano, Felix.
Subjects: Chemistry; Physics
Keywords: Rhenium(I) carbonyl; thermal equilibrium; photophysics; transient absorption; infrared; Re(I)
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23.
Zamyatin, Andrey V.
A Photophysical Investigation of Nickel Tetrapyrrole Macrocycles.
Degree: MS, Chemistry, 2006, Bowling Green State University
► The porphyrins are an important class of chromophores with high stability and…
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▼ The porphyrins are an important class of chromophores with high stability and efficient light absorption ability in the visible and near-infrared regions of the optical spectrum. They find uses in optoelectronics, magnetic materials, photoconductive materials, non-linear optical materials and photo tumor therapeutic drugs. Porphyrins have a set of highly delocalized ð-orbitals situated on the carbon-nitrogen framework. When such a ligand is coordinated to a centrally-located metal atom of the transition series, having incompletely filled d-orbitals (Ni, Co, Fe, Cu, etc.), the ð- and d-manifolds can interact. As a result the excited state deactivation dynamics becomes very dependent on the electronic nature of the central metal.
Advisors/Committee Members: Rodgers, Michael A J.
Keywords: femtosecond, photophysics, two pump one probe, porphyrins, benzoporphyrins
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24.
Zubricky, James R III.
Physical Models of Biochemicallly Important Molecules Using Rapid Prototyping Techniques.
Degree: MS, Chemistry, 2006, Bowling Green State University
► The application of rapid prototyping (RP) to the field of molecular modeling…
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▼ The application of rapid prototyping (RP) to the field of molecular modeling is growing due to the availability of computer programs and RP machines at major research institutions. Two RP techniques that are applicable to the study are powder-binder printing and Fused Deposition Modeling (FDM). Both of these technologies are available at BGSU and can be used in order to study the basepair interactions in many different types of RNA motifs. I have determined that the powder-binder technique is preferred when the tertiary structure of RNA is desired; conversely, FDM is better when the primary and secondary structures of RNA motifs are desired. By using FDM modeling, you can see the orientation of non-canonical basepairs, hydrogen bonds between atoms, the phosphate- sugar backbone, as well as structural motifs in RNA. I then applied our knowledge of RP technology by creating physical models of the C-loop motif, RNase P RNA, the kink-turn, the sarcin-ricin loop, and the SARS virus genome.
Advisors/Committee Members: Leontis, Neocles B.
Keywords: Rapid prototyping; tectoRNA; ribosomal RNA; stereolithography; selective laser sintering; powder-binder printing; fused deposition modeling; RNA structure; van der waals radius; covalent radius; Z-Corporation; Stratasys Corporation; RNA motifs; C-loop
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