Department: College of Arts and Sciences / Department of Chemistry ![[clear]](close-x.png "Remove this limiter")
42 matches in the database.
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1.
Azzam, Sausan.
Protein Profiling Analysis of Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis Brain Tissue.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2011, Kent State University
► Multiple Sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous…
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▼ Multiple Sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system. Although MS seems to be primarily an inflammatory autoimmune disease, it has become evident that axonal loss plays an important role in the pathogenesis of the disease. Mitochondrial dysfunction and oxidative damage have been implicated in the neuropathology associated with MS and other neurodegenerative diseases. Mitochondrial dysfunction may also play a role in disease pathology in the experimental allergic encephalomyelitis (EAE) mouse model of MS. Previous studies have demonstrated defects in mitochondrial electron transport gene expression in normal appearing gray matter (NAGM) in postmortem MS cortex. These studies have identified transcriptional changes in mitochondrial genes, yet translational or post-translational alterations of proteins may also impact mitochondrial function and energy production. To date, few studies have utilized proteomic approaches to investigate the differentially expressed proteins in the MS brain and its animal model. Our lab has recently reported the identification of several mitochondrial proteins that are found to be altered in NAGM of MS as compared to control cortex. In the current study, we have applied several proteomic approaches to mitochondrial fractions derived from EAE and control mice to obtain a more complete understanding of protein expression changes that could contribute to the mechanisms of mitochondrial dysfunction in MS. In order to ascertain that the resulting variation reflects biological differences between diseased and control states, we first investigated the reproducibility of our cell fractionation techniques and Surface Enhanced Laser Desorption Ionization Time-of-Flight Mass Spectrometry (SELDI-TOF-MS) methodology. We then employed SELDI-TOF-MS to analyze MS and control postmortem brain tissue and the brains of EAE and control mice and we observed changes in a number of mitochondrial proteins, as well as increases in the levels of myelin basic protein (MBP) associated with mitochondrial fractions. MBP is released into Cerebrospinal Fluid (CSF) and is found in the blood in MS patients. It has been shown to kill oligodendrocytes in cell culture. Therefore, in this study we further investigated the effect of MBP on other cell types (neurons and neuroblastoma cells). We have shown that MBP is taken up by neuroblastoma cells where it appears to be associated with mitochondria and leads to apoptosis. MBP also leads to a collapse of the mitochondrial membrane potential in neurons. Free MBP may therefore contribute directly to neurodegeneration in MS. These results may eventually lead to a better understanding of the mechanisms underlying the pathogenesis of MS.
Advisors/Committee Members: Gregory, Roger.
Subjects: Biochemistry; Neurosciences
Keywords: Multiple Sclerosis; Protein Profiling Analysis; SELDI-TOF mass spectrometry; Myelin Basic Protein
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2.
Benson, David Ryan.
Laboratory Kinetic Studies On Binary and Ternary Homogenous Nucleation Under Lower Tropospheric Conditions.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2010, Kent State University
► Ternary homogenous nucleation (THN) involving NH3, H2SO4, and H2O is suspected to…
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▼ Ternary homogenous nucleation (THN) involving NH3, H2SO4, and H2O is suspected to play an important role in our atmosphere. Theoretical studies on THN involving NH3 predict much different results with respect to what the particle formation rates should be. Also, only a few laboratory experiments probing THN with NH3 have been performed, and these experiments have not fully characterized the THN nucleation process. The purpose of this study is to look at THN involving NH3 with a more in depth analysis. This proposed research will include: (1) characterization of the nucleation flow reactor; (2) determination of the wall loss for the gas phase species of NH3 and H2SO4; (3) describing the enhancement of nucleation rates when using THN with ammonia as compared to just binary homogenous nucleation (BHN) with just H2SO4 and H2O; (4) determining the number of NH3, H2SO4, and H2O molecules in the critical cluster; (5) determining the [H2SO4] required using THN to see particle formation.
Advisors/Committee Members: Lee, Shan Hu.
Subjects: Chemistry
Keywords: NH3; H2SO4; NUCLEATION; CIMS; THN; NPF; aerosol
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3.
Celer, Ewa B.
Thermal and Hydrothermal Stability of Polymer-Templated Siliceous Mesostructures.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2007, Kent State University
► Two-dimensional (2-D) channel-like hexagonal SBA-15 (P6mm symmetry group) with and without siliceous…
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▼ Two-dimensional (2-D) channel-like hexagonal SBA-15 (P6mm symmetry group) with and without siliceous plugs and 3-D cage-like face-centered cubic FDU-1 materials (Fm3m symmetry group) were synthesized for the study of thermal (heating up to 1000 °C in air) and hydrothermal (boiling at 100 °C in water) stability of polymer-templated ordered mesoporous silicas (OMSs). The main objectives of this study was: (i) identification of the factors governing the thermal and hydrothermal stability of OMSs; (ii) improvement of the aforementioned stability and structural ordering by adjusting synthesis conditions and/or applying an appropriate post-synthesis modification, and (iii) exploration of microwaves for the synthesis of stable OMSs. The study of channel-like materials with and without internal “plugs” showed that the “plugged” OMSs are generally more stable in boiling water and their stability depends greatly on the time and temperature of the hydrothermal synthesis. Among OMSs the cage-like mesostructures such as FDU-1 exhibit exceptional thermal and hydrothermal stability. These materials retain the structural integrity even after harsh treatment (heating for about 6 hours up to 1000 °C in air or boiling up to 32 days in water). This hydrothermal stability can be further enhanced by high temperature calcination or post-synthesis modification such as chemical attachment of hydrophobic groups or deposition of an extra silica layer on the pore walls. The use of microwaves was shown to be beneficial for the hydrothermal synthesis of OMSs. This method assures a significant reduction of the synthesis time (from days to hours) without sacrificing the structural quality of the resulting materials, and more importantly, it permits an easy programming and control of experimental conditions over a wide range of temperatures and time. It is shown that OMSs subjected to the hydrothermal treatment at elevated temperatures (e.g., 160 °C) are well ordered and exhibit higher stability than those prepared under commonly used conditions.
Advisors/Committee Members: Jaroniec, Mietek.
Subjects: Chemistry, Physical
Keywords: thermal and hydrothermal stability; polymer-templated ordered mesoporous silicas; cage-like silicas; channel-like silicas; microwave-assisted synthesis; gas adsorption
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4.
Chumachenko, Nataliya.
b-Acryloyloxysulfonyl Tethers for Intramolecular Diels-Alder Cycloaddition Reactions.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2005, Kent State University
► A new straightforward route to various b-hydroxy sulfones was developed, proceeding via…
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▼ A new straightforward route to various b-hydroxy sulfones was developed, proceeding via opening of ethylene oxide or propylene oxide with readily accessible zinc sulfinates under essentially neutral aqueous conditions. Good isolated yields (63-78%) and excellent regioselectivites were observed in all cases. Opening of epoxides with zinc 1,3-butadienyl sulfinate afforded (E)-butadienyl b-hydroxyalkyl sulfones bearing b-H and b-methyl substituents in 30% yield. (E)-Butadienyl b-hydroxyalkyl sulfones bearing b-phenyl and b-tert-butyl substituents were successfully synthesized in high yields from butadiene sulfone by coupling of silyl (Z)-butadienyl sulfinate with the corresponding a-bromo ketone, reduction of the resulting product to the secondary alcohol and DMAP-induced (Z)/(E)-isomerization. The esterification of synthesized (E)-butadienyl b-hydroxyalkyl sulfones provided a series of b-acryloyloxy sulfones that differed in the bulk of the substituent on the sulfone tether (H, Me, Ph and tert-Bu) and also in the substitution on the acrylate ester residue (methacrylate, acrylate, a-bromoacrylate and crotonate esters), thus providing a variety of possibilities for Diels-Alder studies. Thermally-mediated intramolecular Diels-Alder cycloaddition reactions of these newly synthesized b-acryloyloxy sulfones proceeded with complete regioselectivity, high (10/1) to complete endo/exo-selectivity, and resulted in the preferential formation of one of the two possible endo-cycloadducts. The yields and stereoselectivities were proportional to the bulk of the substituent on the b-acyloxysulfonyl tether. The proclivity toward Diels Alder reaction increased in the order: acrylates < methacrylates < a-bromoacrylates. In the case of R1 = tert-butyl, the major endo-cycloadducts were separated in 71-72% yield. The computational study conducted suggested that the Diels-Alder reaction proceeds as an asynchronous concerted process; no net loss of electron density from the butadienyl fragment to the acrylate dienophile is observed in the TS. The methacrylate Diels-Alder cycloadduct, available in good yield as a single diastereomer via the developed chemistry, was converted to the corresponding a,b-unsaturated ketone which on reaction with isoprene underwent a highly unusual hetero-Diels-Alder reaction at the ketone C=O group to afford a single spiro-diastereomer. To the best of our knowledge, this is the first example of a hetero-Diels-Alder reaction when both the ketone and diene are unactivated.
Advisors/Committee Members: Sampson, Paul.
Subjects: Chemistry, Organic
Keywords: b-hydroxysulfones; epoxide opening; intramolecular Diels-Alder reaction; vinylsulfones
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5.
Conrad, Andrew Ryan.
Rotational Spectroscopy of Biomolecules.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2011, Kent State University
► The activity and selectivity of a biologically or pharmacologically relevant molecule are…
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▼ The activity and selectivity of a biologically or pharmacologically relevant molecule are dominated by its molecular shape and conformation. Biomolecular processes in which structure affects function include membrane transport, neurotransmission, drug-receptor interactions, protein-ligand binding, and enzyme catalysis. The overwhelming majority of studies on these molecules are in the condensed phase; solvent effects result in the formation of zwitterions for many of these molecules and thus they lose much conformational freedom. Gas-phase spectroscopy removes solvent and intermolecular interactions resulting in greater conformational freedom and allowing study of neutral species in the isolation required to observe the intrinsic molecular properties of biochemical systems. Fourier-transform microwave (FTMW) spectroscopy, a rotational spectroscopy technique, is a powerful tool for unambiguous structural characterization of gas-phase biomolecules with results directly comparable to theoretical predictions and can be used to characterize the structural preferences of pertinent biomolecules such as dipeptides and biomolecular complexes such as water complexes of biomolecules. The incredible resolution afforded by FTMW spectroscopy allows for the assignment of rotational spectra arising from different conformers, isotopomers, and tautomers. This dissertation describes the rotational spectra and structural characterization of a number of biologically relevant molecules. To increase our capabilities to understand the structures of thermally fragile biological species, we have constructed a laser vaporization sample source for a microwave spectrometer. The design and development of a laser vaporization sample source for microwave spectroscopy is described, and the preparation of samples for a number of species for use in the laser vaporization source and resulting rotational spectra are presented. We utilized FTMW spectroscopy to explore the structures of a number of biologically relevant species including glycidol and the glycidol-water complex, the family of cyanophenol molecules, and leucinamide. The experimental structure of glycidol-water indicates that the glycidol monomer undergoes structural changes to accommodate formation of an intermolecular hydrogen bonding network upon water complexation. One conformer of o-cyanophenol and two conformers of m-cyanophenol were observed spectroscopically. The rotational transitions of p-cyanophenol are split due to the internal rotation of the hydroxyl group with respect to the aromatic ring, and the energy barrier to internal rotation is determined from the spectral splitting. Two isotopomers of two conformers of leucinamide, the amino amide derivative of leucine, were observed, and the gas phase structures are significantly different from the crystal phase structures of leucinamide and the gas phase structures of leucine. The rotational spectra of the monosubstituted cyclohexanes silylcyclohexane, germylcyclohexane, ethynylcyclohexane, and cyanocyclohexane are also reported.
Advisors/Committee Members: Tubergen, Michael.
Subjects: Chemistry
Keywords: rotational spectroscopy; FTMW spectroscopy; structural preferences
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6.
Fulvio, Pasquale Fernando.
Synthesis and Characterization of Ordered Mesoporous Inorganic Nanocomposite Materials.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2009, Kent State University
► Ordered mesoporous inorganic nanocomposite materials were synthesized by using soft- and hard-templating…
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▼ Ordered mesoporous inorganic nanocomposite materials were synthesized by using soft- and hard-templating strategies. Ordered mesoporous silicas (OMSs) were obtained by soft templating, whereas ordered mesoporous carbons (OMCs) and mesoporous mixed metal oxides were prepared by hard templating. Also, post-synthesis modification of OMSs was carried out by deposition of mixed metal oxides, carbon and nickel. The resulting materials were characterized by nitrogen and argon adsorption, thermogravimetric analysis, small angle X-ray scattering, powder X-ray diffraction, scanning and transmission electronic microscopy, elemental analysis, temperature programmed desorption and diffuse reflectance Fourier transform infrared spectroscopy. The first part of this dissertation is devoted to the optimization of experimental conditions such as time, temperature, pH and salt addition for the synthesis of several OMSs: SBA-15, SBA-16 and FDU-1. The size of ordered mesopores, surface area and pore volume of the aforementioned OMSs were tailored by adjusting the synthesis time and temperature as well as by combining solvent extraction and calcination for the template removal. A further improvement of SBA-16 and FDU-1 was achieved by using low acid concentration and adding NaCl addition, which resulted in OMSs with large cage diameters and uniform pore openings. Subsequently, the SBA-15 and SBA-16 materials were employed as hard templates for the synthesis of OMCs, using iron chloride as a catalyst for in situ polymerization of pyrrole. After carbonization and silica dissolution, the nitrogen-doped OMCs with tunable mesopores, graphitic domains and magnetic iron-iron carbide nanoparticles were obtained. Also, the pore walls of SBA-15 were modified with 2, 3-dihydroxy naphthalene, which was converted into thin carbon film. The impregnation of the resulting SBA-15-carbon nanocomposites with nickel salts afforded materials with “pea-pod” distribution of nickel nanoparticles. In addition, the pore walls of SBA-15 were modified with metal alkoxides of Al, Ti, and Zr by using a partially hydrolytic sol-gel process, which depending on the experimental conditions resulted in the deposition of thin films and nanoparticles of these oxides. Finally, OMCs were used as hard templates for the synthesis of mesoporous iron-doped alumina-titania mixed oxides, which exhibited high Lewis acidity and partially retained the structural symmetry of the templates used.
Advisors/Committee Members: Jaroniec, Mietek.
Subjects: Chemistry; Materials science
Keywords: SBA-15, SBA-16, FDU-1, ordered mesoporous silicas, ordered mesoporous carbons, mesoporous mixed metal oxides, nitrogen adsorption, ordered mesoporous materials
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7.
Garanin, Evgeny M.
Sulfonated (poly)arenes as low-humidity proton conducting materials for polymer electrolyte fuel cell membrane applications.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2011, Kent State University
► Block-copolymers with highly sulfonated ionomer blocks are considered as the main candidates…
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▼ Block-copolymers with highly sulfonated ionomer blocks are considered as the main candidates for low-humidity high-temperature Polymer Electrolyte Fuel Cell membranes. We present synthetic routes to polyphenylene sulfide (PPS) with a degree of sulfonation (DOS) equal to 1 and to poly(thio-2,5-difluoro-1,4-phenylene). In the future, these polymers can be used as hydrophilic and hydrophobic blocks in polyphenylene sulfide based proton conducting membranes. PPS DOS=1 was synthesized via acid-catalyzed oxidative polymerization of sulfonated 2-(methylsulfinyl)-5-(2-sulfonatophenylthio)benzenesulfonate derivatives. The sulfonated monomers used in this work were prepared from benzenesulfonic acid in 5 to 8 steps. Acid and thermally stable poly(2,5-difluorophenylene sulfide) and poly((((methylsulfonio)-2,5-difluoro-1,4-phenylene)thio)-2,5-difluoro-1,4-phenylene triflate), were successfully derived from 4-(methylsulfinyl)-2,5-difluorophenyl 2,5-difluorophenyl sulfide. The resulting polymers were characterized by FTIR, NMR, TGA and DSC. The number-average molecular weight of poly((((methylsulfonio)-2,5-difluoro-1,4-phenylene)thio)-2,5-difluoro-1,4-phenylene triflate) was studied by 1H NMR spectroscopy and exceeded 20000 Da. 4-(Methylsulfinyl)-2,5-difluorophenyl 2,5-difluorophenyl sulfide was made via an efficient multistep synthesis from 1,4-difluorobenzene. Poly(2,5-difluorophenylene sulfide) is a promising candidate as a non-sulfonated block of future multiblock copolymers. Additionally we report the crystal structures, synthesis, water sorption isotherms, proton conductivity, thermal stabilities and XRD studies, of benzenehexasulfonic acid (BHSA) and benzenetetrasulfonic acid (BTSA), model systems for highly sulfonated polyphenylenes. At comparable humidities and temperatures, BHSA material shows conductivity similar to Nafion which conducts protons via liquid water channels. The conductivity of BTSA is in the range of 108 -104 S/cm. Thermal stability studies on BHSA revealed that it forms unusually stable cyclic benzenehexasulfonic acid-1,2; 4,5-dianhydride and (most likely) benzenehexasulfonic acid-1,2;3,4-dianhydride which, upon prolonged standing in solution, transforms to benzenehexasulfonic acid-1,2-monoanhydride. The mono- and dianhydrides do not hydrolyze readily due to their flatter, more aromatic structures compared to the hydrolysis products. The anhydrides undergo unusual ring-shift isomerization, which is pronounced on the NMR time scale. Additionally, we have disclosed here previously unknown crosslinking that occurs with polyphenylene sulfide with DOS=0.7 at elevated temperatures. Valuable conductivity data are obtained with a novel cell that utilizes a four electrode method for conductivity measurements in powder samples
Advisors/Committee Members: Sampson, Paul.
Subjects: Polymer Chemistry
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8.
Getmanenko, Yulia A.
Design, synthesis and mesomorphic behavior of 2,5-disubstituted pyridine liquid crystals.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2007, Kent State University
► Calamitic (rod-like) 2,5-disubstituted pyridine liquid crystals were synthesized, their mesomorphic properties were…
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▼ Calamitic (rod-like) 2,5-disubstituted pyridine liquid crystals were synthesized, their mesomorphic properties were examined by DSC analysis and polarized optical microscopy, and the charge transport properties of the selected materials were studied by the time-of-flight technique. The Negishi coupling of 2,5-dibromopyridine with alkyl- and arylzinc chlorides resulting in 2-substituted-5-bromopyridine was used as a key step in the construction of the variety of mesogens. Isomeric 2-bromo-5-substituted-pyridines can be prepared by Negishi or Stille coupling of 2-bromo-5-iodopyridine, and in this case the reaction takes place at the C-I site with good selectivity. The literature reaction conditions used for the preparation of 2-substituted-5-methylpyridines were optimized for 3-alkylpyridines with longer tails, and 2-iodo-5-alkylpyridines and 2-tri-n-butylstannyl-5-alkylpyridines were prepared and used as important intermediates for the construction of phenylpyridine, phenyl-bipyridinyl and thiophene-pyridine liquid crystals. A new convenient approach to 2-substituted-5(or 6)-tri-n-butylstannylpyridines was developed using the mild conditions of Negishi coupling of 2-bromo-5(or 6)-tri-n-butylstannylpyridine with organozinc chlorides. Literature conditions (i-PrMgCl, THF, room temperature) used for the synthesis of several 2-bromo-5(or 6)-substituted-pyridines were extended to the preparation of 2-bromo-5(or 6)-tri-n-butylstannylpyridines, and this method is a good alternative to a standard approach which utilized n-BuLi/ -78 °C conditions. The change of the solvent from THF to toluene led to the isomeric 2-tri-n-butylstannyl-5-bromopyridine isolated in good yield. New 2-substituted-5-tri-n-butylstannylpyridines are stable and can be purified by Kugelrohr distillation in most cases or by column chromatography on untreated silica gel. These pyridinylstannanes were exstensively used for the preparation of mesogens constituted of different combinations of 2,5-disubstituted pyridine and thiophene rings. Tetrasubstituted imidazoles were synthesized and their glass forming properties were studied by DSC analysis. Intoduction of N-3-Phenyl-propyl substituent in parent N-H-imidazoles resulted in a substantial reduction of the melting point and formation of stable organic glasses with Tg above room temperature. A series of liquid crystals with dithieno[3,2-b;2’,3’-d]-thiophene core were prepared as potential semiconductors by the Stille coupling with thienylstannanes.
Advisors/Committee Members: Twieg, Robert J.
Subjects: Chemistry, Organic
Keywords: phenylpyridine LCs; thiophene-pyridine LCs; pyridinyl stannanes; selective Negishi coupling; liquid crystal semiconductors; smectic liquid crystals
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9.
Gierszal, Kamil Piotr.
Synthesis, adsorption and structural properties of carbons with uniform and ordered mesopores.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2008, Kent State University
► Various novel carbon mesostructures were explored with respect to their synthesis methods,…
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▼ Various novel carbon mesostructures were explored with respect to their synthesis methods, adsorption properties as well as structural properties. Several important problems were studied including the structural ordering of ordered mesoporous carbons (OMCs), selection of carbon precursors, controlling the pore size, specific surface area and total pore volume of the resulting carbons. Ordered mesoporous silicas (OMSs) and silica colloidal templates were employed as hard templates. The obtained results have been divided into two major chapters dealing with: OMCs synthesized by using OMSs as templates and the mesoporous carbons templated by silica colloidal materials.The first aforementioned chapter presents the following problems. Two different OMSs, SBA-15 and KIT-6, were employed as hard templates and various carbon precursors including mesophase pitches of different softening points were used for the purpose to investigate the relation between the structure of OMCs and their adsorption properties. One of the most important conclusions was that the softening temperature of mesophase pitch clearly affected the structural properties of the resulting OMCs through the formation of different amount of micropores. The other studies involved the synthesis and characterization of OMCs templated by the SBA-16 silica with precisely controlled pore sizes. For this purpose, various carbon precursors were used - sucrose, acenaphthene and furfuryl alcohol. Two types of OMCs were prepared - the fully-filled inverse carbon replicas and the film-type inverse replicas of the SBA-16 silica. The second chapter deals with mesoporous carbons templated by silica colloidal crystals (SCCs) and disordered colloidal silicas. These templates served for the synthesis of mesoporous carbons from mesophase pitch as carbon precursors. The SCC was formed by evaporation method using the aqueous suspension of 46 nm uniform silica colloids, whereas the same method applied to 16 and 31 nm silica nanoparticles afforded only disordered aggregates. Application of these templates showed for the first time that it is possible to achieve the faithful inverse carbon replica of the well-ordered SCC composed of such small colloids. The other problem was devoted to graphitization of SCC-templated OMC. Here, well-graphitizable mesophase pitch as carbon source and SCC formed from 70 nm nanoparticles were employed. Carbonization at 1000 °C and subsequent graphitization of OMC at temperature as high as 2500 °C allowed one to obtain an excellent quality porous carbon ordered at nanoscale and at molecular level. The most important achievement reported in this dissertation was the synthesis of mesoporous carbons with extremely large pore volume and narrow pore size distribution. The structure was synthesized with the use of colloidal silica and resorcinol-crotonaldehyde as template and carbon precursor, respectively. The large pore volume could be obtained by formation of uniform thin carbon film on the pore walls of the aggregates of silica nanoparticles. Such prepared carbons with uniform mesopores reached the highest ever reported value of the total pore volume of ~9 cm3/g. Also, new mathematical relations between basic adsorption parameters were derived. Various measuring techniques were used in order to characterize the adsorption and structural properties of the studied nanoporous materials. Among them were nitrogen adsorption, elemental analysis, powder X-ray diffraction (XRD), small angle X-ray scattering (SAXS), transmission and scanning electron microscopy (TEM/SEM), thermogravimetric analysis (TGA), Raman spectroscopy.
Advisors/Committee Members: Jaroniec, Mietek.
Subjects: Chemistry
Keywords: mesoporous carbons, inverse replication, hard templating, OMC, CMK-3, CMK-5, mesoporous silicas, OMS, SBA-15, MCM-48, KIT-6, colloids, colloidal crystal, nanomaterials, gas adsorption
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10.
Gorka, Joanna.
Polymer-based mesoporous carbons: soft-templating synthesis, adsorption and structural properties.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2010, Kent State University
► The organic-organic self-assembly of phenolic resins and triblock copolymers, under acidic conditions,…
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▼ The organic-organic self-assembly of phenolic resins and triblock copolymers, under acidic conditions, was used to synthesize ordered mesoporous carbons (OMCs) and carbon-based materials. The adsorption and structural properties of these materials were thoroughly studied by nitrogen adsorption, thermogravimetry, XRD and STEM. The first part of this work provides an insight into the self-assembly process under acidic conditions and shows that both the adsorption and structural properties of the polymer-templated OMCs can be easily tuned by varying the synthesis parameters such as the copolymer/carbon precursor ratio, acid concentration, and temperature. The next part covers the organosilane-assisted soft-templating synthesis of OMCs. The effect of the size, structure and concentration of the organosilane used on the mesostructure formation is discussed. In the case of small organosilanes, such as tetraethyl orthosilicate (TEOS), it was possible to obtain uniform silica-carbon mesostructures even with high TEOS loadings. Also, much larger organosilanes such as tris(3-trimethoxysilylpropyl) isocyanurate were used, which resulted in OMCs doped with N and Si heteroatoms. Another chapter of this dissertation is devoted to the incorporation of inorganic nanoparticles into carbon mesostructures. Specifically, metal or metal oxide nanoparticles in the form of colloidal solutions can be added to the synthesis mixture. This strategy was demonstrated for the synthesis of mesostructured carbon-based composites with silica and alumina nanoparticles and crystalline alumina nanosheets. The final part of this dissertation is devoted to the enlargement of the specific surface area of the aforementioned carbons and carbon-based composites. It was shown that the surface area of these materials can be increased by adding TEOS into the synthesis of carbons in order to generate additional microporosity, and/or by post-synthesis activation of the resulting carbons with KOH, carbon dioxide or steam. A combination of this strategy with colloidal templating can be used to obtain hierarchically porous carbons with high surface area, at least two types of mesopores (generated by using block copolymer and colloidal silica templates) and enhanced microporosity (achieved by TEOS-assisted synthesis and/or post-synthesis activation).
Advisors/Committee Members: Jaroniec, Mietek.
Subjects: Chemistry
Keywords: soft-templating synthesis; ordered mesoporous carbons; nitrogen adsorption; hierarchically porous carbons; carbon-inorganic composites; silica-carbon mesostructures
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11.
Grabicka, Bogna E.
Microwave-Assisted Synthesis of Ordered Mesoporous Organosilicas with Surface and Bridging Groups.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2010, Kent State University
► This dissertation reports the synthesis of ordered mesoporous organosilicas, with surface and…
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▼ This dissertation reports the synthesis of ordered mesoporous organosilicas, with surface and bridging groups, obtained under microwave conditions. The study was focused on the usage of microwave irradiation to synthesize high quality organosilica mesostructures, and to monitor their adsorption and surface properties by varying chemical composition as well as time and temperature of hydrothermal synthesis. Specifically, channel-like and cage-like ordered mesoporous organosilicas with various surface and bridging groups were synthesized under microwave conditions. Also, microwave-assisted synthesis of cage-like ordered mesoporous silicas was carried out and improved. For the purpose of comparison, analogous mesostructures were prepared by using conventional heating instead of microwave irradiation. This study shows that the removal of polymeric template from as-synthesized cage-like siliceous mesostructures requires a combination of extraction with acidified ethanol and thermal treatment in flowing nitrogen at about 350 °C. The microwave-assisted synthesis was successfully used to screen a wide range of temperatures and time in order to establish optimal conditions for the preparation of SBA-16. It is noteworthy that this synthesis requires only 8-18 hours instead of the 48 hours normally used. The resulting cage-like materials exhibited high surface area, large pore volume and large pore diameters. The attachment of vinyl, ureidopropyl and mercaptopropyl groups into siliceous pore walls of SBA-15 and SBA-16 mesostructures was successful under microwave conditions. Mono- and bi-functional channel-like and cage-like organosilicas prepared under microwave irradiation showed comparable or improved adsorption properties (for instance, larger pore volume and pore size and higher specific surface area) than those obtained for the corresponding samples synthesized using conventional heating. The microwave-assisted synthesis of periodic mesoporous organosilicas with ethane, isocyanurate and disulfide bridging groups was also explored. Similarly as in the case of organosilicas with pendant groups, the co-condensation synthesis under microwave irradiation afforded ordered mesostructures having organosiliceous framework with high surface area and large pore volume. This work demonstrates the attractiveness of the microwave technique for the synthesis of ordered mesoporous organosilicas.
Advisors/Committee Members: Jaroniec, Mietek.
Subjects: Physical Chemistry
Keywords: ordered mesoporous materials; microwave-assisted synthesis; cage-like mesostructures; channel-like mesostructures; organosilica; nitrogen adsorption; organic surface groups; periodic mesoporous organosilica; co-condensation synthesis
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12.
Grant, Stacy M.
Polymer Templating Synthesis, Adsorption and Structural Properties of Alumina-Based Ordered Mesoporous Materials.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2011, Kent State University
► The main objective of this research was to develop a more complete…
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▼ The main objective of this research was to develop a more complete understanding of underlying chemical processes taking place in the one-pot modified sol-gel synthesis of ordered mesoporous alumina and alumina-based metal oxides. This was accomplished through exploration of the effects of altering synthesis parameters (polymer template, acid concentration, etc.), substitution of constituents (nickel, titanium, etc.) or by the introduction of additives (co-solvent molecules) on the resulting material’s structural properties. In tandem with this approach was the optimization of these alterations in order to produce well ordered mesoporous alumina and alumina-based metal oxides. A secondary goal was in creating general synthesis strategies for tailoring these materials for use in a number of applications. This project resulted in an increased understanding of the cooperative self-assembly process and the effects of various synthesis components and conditions. The most influential variable in the synthesis mixture is the polymer template which determines pore morphology. Variations from optimal resulted in small decreases in both surface area and pore volume. The second most influential variable is acid concentration. Acid concentration is directly proportional to pore width, up to a limiting concentration. Higher acid concentration also led to higher thermal stability and evidence of transitions from the hexagonal to the cubic phase. The addition of co-solvent molecules at low temperature affected the resulting pore volumes and induced microporosity. Unlike their siliceous counterparts, ordered mesoporous alumina did not display the clear relationship between co-solvent concentration and mesopore width. Materials were found to be stable and the synthesis was highly reproducible. A sample preparation method for alumina-based metal oxides was demonstrated. This method was found to be limited by additional metal, it’s suitability for an acidic synthesis and it’s compatibility with the alumina framework. However, it was shown that alumina-based metal oxides (specifically nickel- and titanium-aluminum oxide) result in thermally stable, ordered (up to ~20% additional metal) mesopores with a high degree of thermal stability and crystallinity. Materials were present as a mixed metal phase at the stoichiometric equivalent with excesses of either metal at other equivalents. These materials are currently being used in research labs around the world to determine their suitability for numerous industrial applications.
Advisors/Committee Members: Jaroniec, Mietek.
Subjects: Chemistry; Materials Science
Keywords: ordered mesoporous materials; polymer templated; alumina; aluminum oxide; alumina-based oxides; mesoporous oxides; high surface area catalytic materials
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13.
Grubb, Alan M.
Preparation of Heteroatom-Substituted 1,3-Thiazoles as Building Blocks for Liquid Crystal Synthesis.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2011, Kent State University
► Ferroelectric liquid crystals (FLCs) offer several advantages for display applications, such as…
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▼ Ferroelectric liquid crystals (FLCs) offer several advantages for display applications, such as high resolution and fast switching speeds. However, chevron defects have commonly been observed in FLCs which have hindered their use in displays. In this dissertation, we present synthetic routes to four novel series of 2-alkoxy-, 5-alkoxy-, 5-alkoxy-4-fluoro, and 5-carboxy-1,3-thiazole-based FLCs (compounds 4.12, 2.12, 5.76, and 6.8, respectively), all of which showed smectic C* phases and three of which were free of chevron defects. The first series of FLCs presented (compounds 2.12) utilized a Lawesson’s reagent-mediated cyclization of a corresponding α-benzamido ester to generate the first reported family of 5-alkoxy-1,3-thiazole-based liquid crystals in excellent yield. To facilitate efficient approaches to other alkoxy-substituted 1,3-thiazole-based FLCs, we developed new and improved preparations of two important synthetic building blocks, 2,4- and 2,5-dibromo-1,3-thiazole (compounds 3.11 and 3.3, respectively). These approaches offer significant improvements over the previously reported literature approaches. A second series of FLCs (compounds 4.12) was generated in excellent yield via selective SNAr chemistry on 2,5-dibromo-1,3-thiazole (3.3) to produce the first reported family of 2-alkoxy-1,3-thiazole-based liquid crystals, which are structural analogs of the previously presented 5-alkoxy-1,3-thiazole-based FLCs. In a third study, electrophilic aromatic fluorination was used to generate the first reported series of 5-alkoxy-4-fluoro-1,3-thiazole-based FLCs (compounds 5.76). As part of this study, we developed the first synthetic strategy for the synthesis of a 4-fluoro-1,3-thiazole to be reported outside the patent literature. In a final study, starting from 2,5-dibromo-1,3-thiazole (3.3), we also generated a 5-carboxy-1,3-thiazole-based liquid crystal (compound 6.8) which is a structural isomer of the 2- and 5-alkoxy-1,3-thiazole-based liquid crystals described above, in which the positions of the phenyl and 1,3-thiazole rings are transposed.In addition to reporting phase transition temperatures for all synthesized mesogens, we also present the results of several electro-optical studies for the 2-alkoxy-, 5-alkoxy-, and 5-alkoxy-4-fluoro-1,3-thiazole-based liquid crystals (compounds 4.12, 2.12, and 5.76, respectively), all of which were found to be free of chevron defects.
Advisors/Committee Members: Sampson, Paul.
Subjects: Organic Chemistry
Keywords: synthetic organic chemistry; 1,3-thiazole; 4-fluoro-1,3-thiazole; alkoxy-1,3-thiazole; carboxy-1,3-thiazole; dibromo-1,3-thiazole; liquid crystals
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14.
Grudzien, Rafal M.
Synthesis and characterization of ordered cage-like siliceous mesostructures with organic pendant and bridging groups.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2008, Kent State University
► Ordered cage-like mesoporous materials were synthesized and characterized in terms of their…
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▼ Ordered cage-like mesoporous materials were synthesized and characterized in terms of their surface, structural and adsorption properties. This dissertation covers three major topics devoted to the synthesis of cage-like silicas and organosilicas. The first topic involves the improvement of synthesis conditions of cage-like silicas such as SBA-16 and FDU-1. Special emphasis was given to the study of influence of different synthesis parameters, such as variations of the TEOS/template ratio, inorganic salt, the self-assembly time, and template removal procedure. It was shown that in order to obtain FDU-1 with uniform pore entrances, large cage diameter and high pore volume, optimal triblock copolymer/silica and salt/template ratios should be within 135:1 and 2.5:1, respectively. In addition, the first synthesis step can be shortened to six hours of the original 24 without diminishing the quality of the resulting FDU-1 materials. A two-step template removal method that combines partial extraction and temperature-controlled calcination was demonstrated to be an effective way for complete removal of the template. The second topic includes the fabrication and characterization of cage-like organosilicas with pendant groups, namely, vinyl, mercaptopropyl, ureidopropyl and imidazole. These organosilicas were prepared by co-condensation of desired organosilane and tetraethyl orthosilicate (TEOS) using the optimal synthesis procedures established for pure silicas. The co-condensation synthesis afforded materials with high loadings of organic groups up to 40%, large pore diameters, and narrow pore size distributions (PSDs). Moreover, the structural transformation from cubic to hexagonal was observed under low acidic conditions, double amount of polymer, and the addition of sodium chloride. The third topic involves the incorporation of bulky isocyanurate bridging groups into periodic mesoporous organosilicas (PMOs) using tris[3-(trimethoxysilyl)propyl]isocyanurate and TEOS. The resulting PMOs possess up to 30% of bridging groups, large pore volume and high surface area. The extraction, however, was insufficient to completely remove the template. An additional heating of extracted PMOs, therefore, was carried out to remove the remaining polymer. The aforementioned materials were characterized by nitrogen and argon adsorption, powder X-ray diffraction, transmission electron microscopy, elemental analysis, high resolution thermogravimetry, and Fourier-transform infrared spectroscopy.
Advisors/Committee Members: Jaroniec, Mietek.
Subjects: Chemistry; Materials science
Keywords: mesoporous, FDU-1, SBA-16, organosilicas, pendant groups, bridging groups, adsorption, isocyanurate, template removal, cage-like structures
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15.
Gu, Shihai.
ADSORPTION AND STRUCTURAL PROPERTIES OF POLYMER-TEMPLATED ORDERED MESOPOROUS ORGANOSILICAS SYNTHESIZED BY USING REACTIVE ORGANOSILANES.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2011, Kent State University
► Various organic reactions were explored to develop novel ordered mesoporous organosilicas (OMOs)…
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▼ Various organic reactions were explored to develop novel ordered mesoporous organosilicas (OMOs) by employment of two different synthesis strategies involving: (i) transformation of organic groups in organosilica frameworks, and (ii) formation of new organic groups during the self-assembly process carried out the presence of reactive precursors. An illustration of the first strategy is the synthesis of mesoporous organosilica materials with a hydrophilic bridging group, 1,2-dihydroxyethane, by using triblock copolymer as structure directing agent and ethylene-bridged organosilane as an initial precursor. Cetyl-trimethylammonium permanganate was used to transform ethylene bridge to 1,2-dihydroxyethane and to obtain a new OMO material with high specific surface area (reaching 660 m2/g), large pore size, and significant secondary mesoporosity. The major part of this dissertation is devoted to the development of ordered silica-based mesostructures with different organic groups such as N-hydroxyurea and boron-containing groups, which are relevant to biological and environmental applications. These materials were prepared by the self-assembly of a bridged organosilane (framework building precursor) and a block copolymer (soft template) in the presence of reactive precursors able to form new organic functionalities. This strategy was used to obtain a series of ordered mesoporous ethane-silica samples with N-hydroxyurea groups by using 3-isocyanato-propyltriethoxysilane and hydroxylamine hydrochloride salt as reactive precursors. The latter played a double role: (1) pH adjustor (no acid was used in this synthesis) and (2) reactive precursor needed for the formation of a new pendant organic group, N-hydroxyurea. In addition to N-hydroxyurea group, mercaptopropyl and ureidopropyl groups were introduced too in order to improve the adsorption affinity of the resulting OMOs towards metal ions. In addition, organosilica mesostructures with both basic and acidic groups were studied; namely, one mesoporous organosilica with biologically relevant hanging group, 1-amino-1,1-bisphosphonate, was synthesized and characterized.
Advisors/Committee Members: Jaroniec, Mietek.
Subjects: Materials Science
Keywords: ordered mesoporous organosilicas
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16.
Hoover, Robert R. Jr.
New Method for Coating Nickel with Ultrathin Platinum Films.
Degree: MS, College of Arts and Sciences / Department of Chemistry, 2010, Kent State University
► An atomic layer deposition (ALD) technique for applying very thin platinum…
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▼ An atomic layer deposition (ALD) technique for applying very thin platinum coatings onto nickel substrates is presented. In this research, a removable nickel rotating disk electrode was used as the substrate for a process involving MeCpPtMe3 and H2, both of which were in the gas phase when exposed to the substrate. The substrate was exposed to the two aforementioned compounds sequentially. Ultra pure N2 was used to remove each component before introducing the next one into the chamber. This process of alternately exposing the nickel disk to MeCpPtMe3 and H2 (with N2 in between) was repeated for specified numbers of times in order to produce films of various thicknesses. Electrochemical properties of the coatings were tested using rotating disk electrode geometry. On several occasions, the total amount of Pt applied was determined in order to assess the economic feasibility of potential scale up.
Advisors/Committee Members: Tolmachev, Yuriy.
Subjects: Analytical chemistry; Automotive materials; Chemical engineering; Chemistry; Energy; Environmental engineering; Materials science; Molecules
Keywords: ALD; Pt; oxygen reduction
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17.
Isler, Yasmin Salah Blaih.
Infrared Spectroscopic Characterization of Phosphoinositide Signaling Pathway Components.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2011, Kent State University
► Membrane lipids are asymmetrically distributed between the inner and the outer leaflet…
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▼ Membrane lipids are asymmetrically distributed between the inner and the outer leaflet of the plasma membrane, and this asymmetric distribution of lipids is an important factor for many signaling events. The lipids investigated in this study, phosphoinositides, are found in the inner leaflet of the plasma membrane and have been shown to mediate a wide variety of important physiological processes by affecting the activity and/or localization of membrane associated proteins. Phosphoinositide properties are largely determined by the characteristics of their headgroup, which at physiological pH is highly charged but is also capable of hydrogen bond formation. For phosphoinositide mediated signaling events to occur, it requires the local enrichment of phosphoinositides, which depend on the interchange between attractive and repulsive forces. Factors expected to affect mutual phosphoinositide interaction are pH as well as the presence of cations or positively charged proteins. The primary goal of this study was to gain more insight about the unique physiochemical properties of phosphoinositides and how they organize laterally in the membrane. We hypothesized that the type and concentration of salt in the subphase affect the phase behavior of phosphatidylinositol and phosphatidylinositol monophosphate monolayers at the air/water interface. Additionally, we hypothesized that the position of the phosphate group at the inositol ring of phosphatidylinositol monophosphates has an effect on how the phosphoinositide molecules interact with each other and other molecular entities embedded in the biomembrane. Using surface pressure/area isotherms, Infrared Reflection Absorption Spectroscopy (IRRAS) and epifluorescence microscopy we have shown that: 1) the presence of monovalent and divalent salt affect the phase behavior, acyl chain conformational order, and domain morphology of phosphatidylinositol monolayers. 2) The monovalent salt concentration affects the phase behavior, acyl chain conformational order, molecular tilt angle, and domain formation of phosphatidylinositol monophosphates. 3) The position of the phosphate group at the inositol ring of phosphatidylinositol monophosphates is an important factor for their mutual interaction. The second aim of this study was to investigate the interactions between phosphoinositides and cholesterol. Our goal was to gain further insight into this interaction and to investigate the possibility that cholesterol may enhance phosphoinositide co-localization and subsequent domain formation. We studied lipid monolayer systems in the presence of cholesterol as well as in the presence of cholesterol derivatives to observe changes in phosphoinositide interaction and domain formation and we found that: 1) cholesterol had a condensing effect on the phosphoinositide monolayer films and that an increase in the molar concentration of cholesterol in the lipid system further condensed these monolayers. 2) Each of the investigated phosphoinositide derivatives was not able to form domains without the presence of cholesterol. 3) Modifications of the hydroxyl group position of cholesterol lead to an altered interaction with phosphoinositides. Our results underscored that cholesterol induces phosphoinsitide domain formation and the results highlighted the importance of the hydroxyl group of cholesterol for the putative phosphoinositide/cholesterol interaction.
Advisors/Committee Members: Gericke, Arne.
Subjects: Chemistry
Keywords: monolayers, air/water interface, IRRAS, epifluorescence microscopy, phosphoinositides, phosphoinositide domain formation, cholesterol
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18.
Jiang, Zhiping.
CHARACTERIZATION OF PHOSPHOINOSITIDE AND SPHINGOLIPID DOMAIN FORMATION IN MODEL MEMBRANES.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2010, Kent State University
► Phosphoinositides (PIPs) act as signaling molecules by recruiting critical effectors to specific…
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▼ Phosphoinositides (PIPs) act as signaling molecules by recruiting critical effectors to specific subcellular membranes to regulate cell proliferation, apoptosis and cytoskeletal reorganization. These processes require a tight regulation of PIP generation and turnover as well as a high degree of compartmentalization. In addition to the cell compartment specific accumulation of PIPs, it has been suggested that many of the observed physiological functions require selective enrichment of PIPs in microdomains. However, the mechanisms that lead to the formation of PIP-enriched microdomains are still elusive. Our goal in this study was to detail the physiochemical conditions that lead to the formation of phosphoinositide-enriched domains in model membranes. Some factors that have effects on PIP-enriched microdomain formation such as the concentration of cholesterol, temperature and ionic strength were investigated. The induced PIP-enriched domains by some PIP-interacting proteins were also investigated. We have shown that: 1) the nature of the phosphoinositide headgroups affects cholesterol-independent and cholesterol-dependent domain formation. 2) Cholesterol enhances phosphoinositide domain formation through an active interaction that involves cholesterol hydroxyl group/phosphoinositide headgroup interaction. 3) Phosphoinositide domains are in a fluid phase and they are stabilized by mutual hydrogen bond formation between the headgroups. 4) Different phosphatidylinositol derivatives headgroups exhibit different domain properties. The other aspect of my study was to characterize the biophysical properties of Ceramide 1-phosphate (Cer1P). Ceramide is a well-characterized sphingolipid metabolite and second messenger that participates in numerous biological processes. When ceramide is phosphorylated by ceramide kinase (CERK), Cer1P is obtained. It has recently been proposed that Cer1P is involved in cell survival, cell proliferation, inflammation and phagocytosis. How Cer1P is involved in such a variety of functions hasn’t been fully characterized yet. Therefore knowing the biophysical properties of Cer1P is the first step to understand how the complicated functions involving Cer1P are performed in biological systems. In this study, we have shown that: 1) the order of lipid raft domains is affected by the presence of Cer1P in a manner that is dependent on the ionization state of the lipid. The headgroup of Cer1P might function as an electrostatic switch that drives the lipid in and out of gel phase domains, which is expected to affect the domain morphology and the availability of the lipid for proteins. 2) Cer1P shows some co-localization with PIPs. This co-localization of Cer1P with PIPs may have implications in how Cer1P is involved in the PI3K signaling pathway to promote cell survival and cell proliferation.
Advisors/Committee Members: Gericke, Arne.
Subjects: Biophysics
Keywords: phosphoinositide, phosphoinositide domain formation, ceramide 1-phosphate
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19.
Jonathan, Tietz I.
Thienothiophene-Based Liquid Crystals: Synthesis and Comparative Evaluation of Mesophase Properties.
Degree: MS, College of Arts and Sciences / Department of Chemistry, 2012, Kent State University
► Sulfur-based heteroaromatic cores often impart advantageous properties to liquid crystals (LCs). One…
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▼ Sulfur-based heteroaromatic cores often impart advantageous properties to liquid crystals (LCs). One little-investigated sulfur-based heterocyclic family is thienothiophene; recently, thienothiophene-based materials have attracted exponentially growing attention in a variety of materials applications. However, thienothiophenes have largely escaped the notice of the LC community. In this thesis, we present an initial exploration into the effect of the thienothiophene core on the mesomorphic properties of LCs. Thus, we have synthesized several families of target LCs: alkyl 5-(4-alkoxyphenyl)thieno[3,2-b]thiophene-2-carboxylate esters (I), alkyl 5-(4-alkoxyphenyl)thieno[2,3-b]thiophene-2-carboxylate esters (II), and two alkoxythienothiophene-based LCs (4-(alkoxycarbonyl)phenyl 5-(alkoxy)thieno[3,2-b]thiophene-2-carboxylate (III) and 4-(alkoxy)phenyl 5-(alkoxy)thieno[3,2-b]thiophene-2-carboxylate (IV)). In the synthesis of I, we elaborated a series of alkyl 2-mercaptoacetates to alkyl thieno[3,2-b]thiophene esters in an efficient and operationally facile tandem nucleophilic substitution and aldol reaction. These thienothiophene esters were regioselectively halogenated at the α-position and submitted to Pd(0)-catalyzed Suzuki-Miyaura cross-coupling with a series of potassium 4-alkoxyphenyltrifluoroborate salts to yield the target LCs. This synthesis was efficient and marks the first use of the trifluoroborate variant of Suzuki-Miyaura coupling in the LC field. Family II was prepared in an analogous manner. For the synthesis of III and IV we developed a strategically novel and facile route to 2-alkoxythiophenes by mild oxidation and Mitsunobu etherification of a series of easily prepared thiophen-2-yltrifluoroborate salts. With these materials in hand, 4-bromo-2-octyloxythiophene was regioselectively formylated by LDA-mediated deprotonation and attack by N-formylpiperidine. The resulting 3-bromo-5-octyloxythiophene-2-carbaldehyde was submitted to similar ring-closing conditions with a mercaptoacetate as in I and II to yield the first long-chain 2-alkoxythieno[3,2-b]thiophene. This ester was then hydrolyzed and submitted to Steglich esterification to give targets III and IV. Most thieno[3,2-b]- and [2,3-b]thiophene-based materials presented in this study were found to exhibit the smectic C (SmC) mesophase. Notably, thienothiophene-based materials gave rise to much wider mesophases than their phenyl analogues. We found that thieno[2,3-b]thiophene, while less often exploited in the design of materials, gave markedly wider SmC mesophases in LCs than their thieno[3,2-b]thiophene analogues. When we incorporated a chiral tail into these molecules, however, the influence of the core on LC properties was destroyed and no significant difference was seen between thieno[2,3-b]- and thieno[3,2-b]thiophene-based LCs. Alkoxythieno[3,2-b]thiophene cores, which are unprecedented in materials applications, gave rise to wider and more diverse mesophases than their phenyl analogues. One target, 4-(octyloxy)phenyl 5-(octyloxy)thieno[3,2-b]thiophene-2-carboxylate, exhibited SmC and N phases both, making it the first nematic material we have reported based on thieno[3,2-b]thiophene. In this thesis we present in detail the synthesis of the above materials, a contextual discussion of the literature, and the results of mesophase evaluation of these novel liquid crystals.
Advisors/Committee Members: Seed, Alexander J.
Subjects: Chemistry; Materials Science; Organic Chemistry
Keywords: thienothiophene; liquid crystals; smectic; trifluoroborates; 2-alkoxythiophene; synthetic organic chemistry; thieno[3,2-b]thiophene; thieno[2,3-b]thiophene; thiophen-2(5H)-one; alkoxythienothiophene
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20.
Kameel, Fathima R.
Optical Properties and Chemical Composition of Secondary Organic Aerosol.
Degree: MS, College of Arts and Sciences / Department of Chemistry, 2009, Kent State University
► Aerosol particles (APs) affect the Earth’s energy balance directly by absorbing and…
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▼ Aerosol particles (APs) affect the Earth’s energy balance directly by absorbing and scattering radiation, and indirectly by altering the reflectance and persistence of clouds. Both parameters are determined by the chemical composition, size and shape of APs. APs consist of complex organic and inorganic mixtures, which include black carbon/soot as well secondary organic matter (SOM) proceeding from the gas-phase. SOM, also known as humic-like substances (HULIS), plays a key role in determining the optical properties of APs due to its ability to absorb radiation in the visible region of the solar spectrum. The chemical characterization of SOM is a daunting task that involves comprehensive chemical analysis, largely via chromatography/high-resolution mass spectrometry (HRMS), one of the most powerful analytical techniques available. However, optical properties are associated with chromophores within specific chemical structures, rather than with molecular formulas. Simpler mixtures can mimic the optical properties of secondary organic aerosol (SOA). Optical properties of mixtures are not linear combinations of the optical properties of its components. Furthermore, optical properties are not intrinsic to APs, but depend on external parameters, such as insolation and relative humidity. Therefore full speciation is neither a necessary nor sufficient condition for characterizing the optical properties of SOA.
Advisors/Committee Members: Lee, Shan-Hu.
Subjects: Atmosphere; Chemistry
Keywords: photolysis; AEROSOL; HULIS; EIC; Atmos; 289-m/z; chromatograms
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21.
Khairuddean, Melati.
Synthesis of Fluorinated Liquid Crystals.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2008, Kent State University
► Research here involves the design and synthesis of liquid crystals with concentration…
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▼ Research here involves the design and synthesis of liquid crystals with concentration on the influence of fluorination on the physical properties in a variety of structures and phases. Fluorine substitution in different positions within the core, the terminal chains or the linking groups produce materials with different physical properties. A variety of liquid crystals with semifluorinated tails including 4-alkoxybenzoic acids, 4-alkoxybenzoyl hydrazines and N,N’-bis(4-alkoxybenzoyl) hydrazines have been synthesized and their properties are compared with their perhydrogenated analogs. We also report the synthesis and mesogenic properties of a new series of 2,5-diaryl-1,3,4-oxadiazoles and 2,5-diaryl-1,3,4-thiadiazoles with semifluorinated alkoxy chains and compare them with their perhydrogenated analogs. To better understand the influence of the different components of the amphiphilic polyhydroxy molecules on their mesophase behavior, we synthesized and characterized a series of some new hydroxylated amides derived from 3,4,5-tris(n-nonyloxy)benzoic acid and some ester versions of these molecules (as opposed to the known amide mesogens). Different mesophases have been observed depending on the identity of the hydrophilic units. We also synthesized and initiated studies of substitution at different positions in 2,5-functionalized-1,3,4-oxadiazole compounds to understand how the 1,3,4-oxadiazole unit influences the mesogenic properties. We have synthesized some biphenyl twin mesogens with different spacers and fluorine content in order to further investigate whether flexoelectricity is somehow related to the stability of these blue phase liquid crystals.
Advisors/Committee Members: Twieg, Robert.
Subjects: Chemistry
Keywords: semifluorinated and fluorinated liquid crystals
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22.
Laubacher, Gretchen.
Rotational Spectra and Structures of Diethanolamine and 2-Aminophenol.
Degree: MS, College of Arts and Sciences / Department of Chemistry, 2011, Kent State University
► Microwave spectroscopy is an important tool for gathering information on the structures…
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▼ Microwave spectroscopy is an important tool for gathering information on the structures of molecules. In my research, I have studied the environmentally relevant molecule diethanolamine using microwave spectroscopy. Diethanolamine, a DOT classified environmentally hazardous substance, is commonly used in the production of soaps and other cosmetics. When in the presence of nitrates, diethanolamine is shown to form an extremely potent carcinogen. The study of diethanolamine using microwave spectroscopy provides further information on the molecule, while the rotational transitions recorded can be used in future databases of environmentally hazardous substances. I have obtained the theoretical structures of diethanolamine, along with the rotational spectra of two conformers of the molecule. In addition, the rotational spectra of several isotopomers of diethanolamine have also been found. In addition to studying the environmentally relevant molecule diethanolamine, I have also obtained the rotational spectrum of 2-aminophenol. 2-aminophenol is an interesting molecule to study; with the addition of water, it is unknown if the conformation of 2-aminophenol will change, as other molecules, such as 2-aminoethanol, previously studied have had conformational changes with the addition of water.
Advisors/Committee Members: Tubergen, Michael.
Subjects: Chemistry
Keywords: microwave spectroscopy; diethanolamine; rotational
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23.
Liu, Na.
Novel Dicyanomethylenedihydrofuran (DCDHF) Fluorophores Synthesis.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2008, Kent State University
► This dissertation includes four different subjects: 1) Benzofuran synthesis via α-acylcarbonium ion;…
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▼ This dissertation includes four different subjects: 1) Benzofuran synthesis via α-acylcarbonium ion; 2) Synthesis of partially fluorinated aromatic compounds as organic semiconducting material; 3) Synthesis of polyimide/polyamic acids and their monomers for a study of double layered alignment film (DLAF); 4) Novel DCDHF fluorophores synthesis for single-molecule imaging application. Amongst these four topics, the last one is the main research subject. One pot benzofuran synthesis from the reaction between p,p'-dialkoxy or p,p'-diaryl and even tetra-alkoxy benzoins substituted benzoins with substituted phenols or naphthols in the presence of SOCl2 or PPh3/CCl4 has been examined in a variety of solvents to study the scope of this synthesis method. The original interest to find mesogenic properties on these newly synthesized benzofurans was not found yet, while one or more crystal-to-crystal transitions existed in some of these compounds. The partially fluorinated polynuclear compounds: 1,2,3,4-tetrafluorobenzo[e]pyrene and 1,2,3,4-tetrafluorodibenzo[fg,op]naphthacene were synthesized. Both of their crystal structures display a compact cofacial packing style, which is important for organic semiconducting material to achieve high charge mobility. This study shows the dramatic crystal packing influence of perfluorination of just one of the multiple rings of benzo[e]pyrene since the former compound crystallizes in a herringbone configuration. A novel DLAF to obtain greater control of the alignment characteristics of the liquid crystal director has been studied. The DLAF consists of a thin fluorinated polymer layer on the top of a rubbed non-fluorinated, non-branched polyimide layer. Both polyimide/polyamic acids and their monomers with variable pendant perfluorinated chains to support the DLAF study were synthesized using different chemistry methods. In order to overcome autofluorescence of typical biological systems, DCDHF fluorophores with bathochromic absorption and emission were synthesized by using bisaromatic or trisaromatic units (combination of phenyl or/and thiophene rings) as the conjugation link. DCDHF dimers using a 1,4-cyclohexane as spacer with two rigidly connected DCDHF chromophores with different conjugation cores were synthesized using different synthetic method to study the influence of orientation and spacing of fluorophores on their photophysical property changes. This is a valuable method to detect the change of environment inside of the cells. A new series of fluorogenic DCDHF molecules have also been successfully synthesized. Their fluorescence can be turned on or changed after specific photoactivation or thermoactivation reactions.
Advisors/Committee Members: Twieg, Robert.
Subjects: Organic chemistry
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24.
Luchette, Paul A.
Novel methond for characterizing membrane proteins by NMR.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2006, Kent State University
► We present results from experiments that focused in the following two areas:…
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▼ We present results from experiments that focused in the following two areas: characterization and evaluation of lyotropic liquid crystal matrices as potential model membrane systems and using O2 as a paramagnetic probe of membrane immersion depth by NMR. Lyotropic liquid crystal structural studies focused on characterization of the structure of the isotropic bicelle as either a spheroidal mixed micelle or disc structure. Measurement of the extent of intermixing of the two principle phospholipids components of the system, DMPC and DHPC supported the disc structure of the isotropic bicelle. We also evaluated five materials known to form lyotropic liquid crystals, three dyes cromolyn, blue 20, and violet 27, a metal polymer V2O5, and a biopolymer, 2-isopropyl cellulose for their ability to align in the static field of the spectrometer. Of these materials, the cromolyn LC proved the best candidate as a host liquid crystal matrix for weak alignment studies. O2 was used as a paramagnetic agent to determine membrane immersion depth. The paramagnetic effects of the O2 molecule on nuclear spins are increases in relaxation rates and chemical shift perturbations, both of which are short range in nature. Additionally, O2 molecules assume exhibit an approximately Gaussian distribution across a lipid bilayer, with the highest concentration at the center of the membrane. By measuring changes in chemical shift perturbations and nuclear relaxation rates, we were able to determine the immersion depth of individual atoms of lipids, small peptides (indolicidin), and the large membrane protein diacylglycerol kinase (DAGK). We also determined that a dipolar interaction was responsible paramagnetic relaxation rate enhancement, while chemical shift perturbations were due to a contact interaction. In addition, O2 proved useful for determining which amino acids involved in the binding interaction of two water soluble proteins, the Fc fragment of an immunoglobin protein and its binding ligand, a fragment of protein A from S. aureus.
Advisors/Committee Members: Prosser, R S.
Subjects: Chemistry, Physical
Keywords: membrane, NMR, protein, lovemonkey, lyotropic, liquid crystal, bicelle
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25.
Morris, Mark J.
Translational Regulation of mRNA by G-Quadruplex Structures.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2012, Kent State University
► Structures present within the 5′-untranslated region (5′-UTR) of mRNAs, including cellular mRNAs,…
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▼ Structures present within the 5′-untranslated region (5′-UTR) of mRNAs, including cellular mRNAs, have been shown to regulate translation. Guanine-rich sequences adopt one such structure, the G-quadruplex, which is a four-stranded form made up of two or more G-quartets. The existence of a G-quartet structure consisting of four hydrogen-bonded guanines was suggested more than four decades ago. Although DNA G-quadruplexes have been studied extensively, formation of RNA G-quadruplexes, particularly their regulatory roles in translational control, is just beginning to emerge. It was once thought that the role of RNA G-quadruplex structures located in the 5′-UTR of mRNAs was completely repressive. We show that M3Q, a G-quadruplex forming sequence located in the 5′-UTR of the MT3-MMP gene, forms an unusually stable intramolecular G-quadruplex that inhibits translation in eukaryotic cells. However, we present functional as well as structural evidence that sequence redundancy in a G-rich segment within the 5′-UTR of human VEGF mRNA supports a ‘switchable’ RNA G-quadruplex structure that is essential for cap-independent IRES-mediated translation initiation. Thus, we show that RNA G-quadruplexes can have a dual role as being both repressive as well as necessary for translation and that their functional role is a context dependent phenomenon. Additionally, we show that small molecules can destabilize an ultra stable M3Q RNA G-quadruplex structure and increase translation by alleviating the repressive effect of the quadruplex.
Advisors/Committee Members: Basu, Soumitra.
Subjects: Biochemistry
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26.
Mukherjee, Riya.
Studies on the Coordination Chemistry of Vanadium, Barium and Cobalamins.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2011, Kent State University
► Part 1 of this dissertation concerns studies on polynuclear V(III)/carboxylato complexes (Chapter…
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▼ Part 1 of this dissertation concerns studies on polynuclear V(III)/carboxylato complexes (Chapter 2) and a Ba(II)/thiodiacetato complex (Chapter 3) formed in aqueous solution. The structures of[V3(µ3-O)(µ-OOCCH2Br)6(OH2)3]CF3SO3•H2O and [V3(µ3-O)(µ-OOCCH2CH3)6(OH2)3]Cl•2H2O have been determined by X-ray diffraction in chapter 2. Electrospray mass spectrometry, 1H NMR and UV-vis spectroscopy and diffusion coefficient measurements suggest that trinuclear and tetranuclear V(III)/carboxylato complexes are present in solution. Chapter 3 concerns the synthesis of polymeric {Ba[S(CH2COO)2(H2O)3]•2H2O}n, characterized by X-ray diffraction, elemental analysis, FT-IR spectroscopy, thermogravimetric analysis and 1H and 13C NMR spectroscopy. Ba2+ is ten-coordinate, ligated to four tda (O and S) and three aqua ligands. Bridging of Ba2+ centers via the tda ligand creates an extended 2-D polymeric layered structure. Part 2 of this dissertation is concerned with cobalamin (= vitamin B12) chemistry. The development of vanadate (V(V)) therapeutics as oral insulin enhancing agents substitutes for treating diabetes is an active research field. By coordinating the therapeutic to the β axial site of cobalamin, the absorption and cellular uptake is significantly enhanced. In Chapter 4, the extensive solution characterization of two vanadate/B12 conjugates incorporating a (3-hydroxy-2-methyl-1H-pyridin-4-one)propyl linker is reported. The conjugates are tested in the streptozotocin rat model for Type 1 diabetes. The orally administered therapeutic captopril is widely used for treating hypertension and cardiovascular disease, with undesirable side effects. Chapter 5 reports the synthesis of captoprilcobalamin (CapSCbl). Characterization by 1H NMR spectroscopy and X-ray diffraction shows that CapSCbl exists as two geometric isomers. Kinetic studies on the formation of CapSCbl and its decomposition in acidic solution are also reported. The last two chapters report rate constants and proposed mechanisms for the reactions of peroxynitrite/peroxynitrous acid (ONOO-/ONOOH) with the reduced forms of vitamin B12, cob(II)alamin (Chapter 6) and cob(I)alamin (Chapter 7). ONOO-/ONOOH is implicated in multiple inflammatory and neurodegenerative diseases. ONOOH reacts directly with Cb(II) to give cob(III)alamin and •NO2, followed by a rapid reaction between •NO2 and Cbl(II) to primarily form nitrocobalamin. A mechanism involving rate-determining 1e- oxidation of Cbl(I) by ONOO(H) to yield Cbl(I) and •NO2 followed by multiple fast steps leading ultimately to oxidation of 5Cbl(I) to 5Cbl(II) and N2 formation is proposed.
Advisors/Committee Members: Brasch, Nicola E.
Subjects: Inorganic Chemistry
Keywords: cobalamins, peroxynitrite, bioconjugates, vanadium, barium, captopril
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27.
Novikov, Yehor.
1-Bromo-1-lithioethene as a building block for organic synthesis.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2005, Kent State University
► 1-Bromo-1-lithioethene has proven to be a useful practical reagent for the selective…
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▼ 1-Bromo-1-lithioethene has proven to be a useful practical reagent for the selective introduction of the 1-bromoethenyl group into various organic and organometallic substrates. The conditions for 1-bromo-1-lithioethene synthesis were optimized and reasons for published erratic yields of 1-halo-1-lithioethenes were revealed. An inexpensive all glass low temperature reactor was designed to allow a reproducible synthesis of 1-bromo-1-lithioethene and perform routine chemical transformations at -100 to -125 °C. Experimental observations along with computational evidence suggest that 1-bromo-1-lithioethene exists in a crystalline form while its bromine atom remains non-chelated. At -110 to -115 °C, 1-bromo-1-lithioethene affords clean 1,2-addition to carbonyl compounds. It possesses low basicity and is compatible with acetate, allyl ether and tosylate protecting groups. Several dichlorosilanes, tributyltin chloride and iodine proved to be efficient electrophiles for trapping 1-bromo-1-lithioethene providing one-step access to potentially useful small 1,1-difunctionalized ethene building blocks. Esters of a-bromoallylic alcohols undergo Ireland-Claisen rearrangement under mildly basic enolization conditions. Esters of tertiary bis-allylic alcohols (originating from trapping of 1-bromo-1-lithioethene with a,b-unsaturated ketones) provided the best yields of rearranged products under Li(NSiMe3)2 / MnCl2 conditions with preparatively useful levels (ca 1:10) of alkene E/Z selectivity and good regioselectivities. According to ab initio calculations and the experimentally observed trends, the rearrangement of (Z)-silyl ketene acetals of these tertiary a-bromoallylic esters is faster and much more selective than the rearrangement of the corresponding (E)-silylketene acetals. For other substrates, trialkylsilyl triflate / triethylamine enolization conditions proved to be optimal but, in some cases, observed alkene E/Z selectivities were lower (1 : 4 to 2 : 3) and no regioselectivity was observed for secondary bis-allylic alcohols (originating from trapping of 1-bromo-1-lithioethene with a,b-unsaturated aldehydes). 1-Bromo-1-lithioethene was successfully applied in partially developed synthetic approaches toward Physalin and VM55599, showing its potential as a building block in natural products syntheses.
Advisors/Committee Members: Sampson, Paul.
Keywords: organolithiums; Felkin-Anh diastereoselectivity; low temperatures; cryogenic reactor; carbohydrates; building blocks
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28.
Quainoo, Emmanuel W0bil.
METHOD DEVELOPMENT AND INVESTIGATION OF FLUORESCENT PHOSPHOINOSITIDE CELL SIGNALING PROPERTIES BY CAPILLARY ELECTROPHORESIS.
Degree: MS, College of Arts and Sciences / Department of Chemistry, 2010, Kent State University
► Phosphatidyl inositides (PIs) are important regulators of cell signaling. Phosphoinositide 3-kinase (PI3-K)-activated…
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▼ Phosphatidyl inositides (PIs) are important regulators of cell signaling. Phosphoinositide 3-kinase (PI3-K)-activated signaling plays a key role in the development of cancer. Therefore various anticancer treatments target this pathway. The aim of this work was to develop an optimized method to separate fluorescent PIPs quickly and efficiently at room temperature using CE-LIF. The reason for the development of a method capable of separating the PIPs at room temperature was that, it could be used for single cell studies. In this regard, the effect of various cations on the separation of the PIs and their seven PIP derivatives was investigated. The effect of pH, temperature, voltage, as well as other buffer mixtures were also studied. Based on this developed method, the activity of PI3-K and PTEN enzymes in NIH 3T3 cells and MDA-MB 231 cells was also studied. The bioactivity of PIPs in these cells was investigated to ascertain whether preliminary CE studies would prove that they were able to be converted inside the cells into other phosphorylated derivatives. Lipid kinases and phosphatases play active roles in cell signaling. These have serious implications in many disease states. For example, accumulation of PIP3 leads to metastatic cancers. Therefore, inhibition studies were also performed to find out whether PI3-K inhibitors were able to block the conversion of PIP2 to PIP3. This is of particular interest in cell-based assays and research involving cancer drug development.
Advisors/Committee Members: Mwongela, Simon M.
Subjects: Biochemistry
Keywords: phosphoinositides, capillary electrophoresis, phosphatidyl inositol, phosphatidyl inositol phosphates, micellar electrokinetic chromatography, metal cations, inhibitors,phosphatases, cell signaling, lipids, PTEN,PI3-K, PIPS
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29.
Redfern, Roberta E.
Characterization of Binding of PTEN and its Disease Related Mutants to Phospholipid Model Membranes.
Degree: PhD, College of Arts and Sciences / Department of Chemistry, 2008, Kent State University
► PTEN, phosphatase and tensin homologue deleted on chromosome 10, is a tumor…
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▼ PTEN, phosphatase and tensin homologue deleted on chromosome 10, is a tumor suppressor that is commonly lost or mutated in many different diseases, including cancer, Bannayan Zonana syndrome, heart disease and cancer. The mechanism of the effects of the loss or mutation of PTEN is not known, other than the effects on the regulation of downstream effector molecules. While many other research groups have studied the effects of PTEN loss or mutation on tumor formation in mouse models, no group has undergone the daunting task of characterizing the protein biophysically, in order to determine how these mutations affect the actual action of the protein. In this study, we have shown that PTEN binds specifically to PI(4,5)P2 over all other phosphoinositides, including its substrate, PI(3,4,5)P3. This binding event is also associated with a conformational change, which is believed to activate the protein and increase its rate of turnover of PI(3,4,5)P3. Additionally, we shown in these studies that the binding specificity of PTEN is dependent on the presence and identity of the N-terminus, which contains a PI(4,5)P2 binding domain. Removal or mutation of the protein's N-terminus abrogates the binding and thus activity of the protein. One particular amino acid which is often mutated in many forms of cancer, the lysine in position 13, has been shown to be extremely important in the interaction of PTEN with PI(4,5)P2 containing membranes. We show that even while maintaining overall charge of the N-terminus and even overall identity, mutation of the lysine in this position results in a loss of binding specificity. We have also studied the binding of an autism related mutation of PTEN, which results in an increased binding to phosphatidylserine, which may play a role in the ability of the protein to turnover its substrate in vivo. We have also studied the effects of cholesterol on the binding of proteins to phosphoinositide containing membranes, which has proven to have different effects on the binding of different proteins. Finally, we show that phosphoinositides form domains in model membranes in the absence of proteins and the presence of cholesterol appears to enhance these formations.
Advisors/Committee Members: Gericke, Arne.
Subjects: Biochemistry
Keywords: PTEN, phosphoinositides, PI3K pathway, cholesterol
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30.
Schonhoft, Joseph.
Biochemical and Biophysical Study of the Polymorphic G-Quadruplexes Formed by the Insulin Linked Polymorphic Region.
Degree: MS, College of Arts and Sciences / Department of Chemistry, 2009, Kent State University
► The Insulin Linked Polymorphic Region (ILPR) is a VNTR region located upstream…
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▼ The Insulin Linked Polymorphic Region (ILPR) is a VNTR region located upstream of the Insulin (INS) gene that consists of the repeat 5′-ACAGGGGTGTGGGG (repeat a) and several less abundant sequence repeats (repeats b-n). Repeats in the ILPR have been shown to have the ability to adopt a non B-DNA conformation known as a G-quadruplex, consisting of planar stacks of Hoogsteen hydrogen bonded guanine nucleotides. Here, we have investigated the structural polymorphism of G-quadruplexes formed from the most common repeat sequences and have discovered several unique thermodynamic and kinetic properties. Specifically, the repeats can adopt many different G-quadruplex topologies and the predominant repeat ‘a’ can form two distinct conformations that coexist in solution. We have also shown that tandem G-quadruplexes can interact to form a quadruplex inspired higher order structure, which is one of the first of such observations, and strongly suggests that conformations adopted by multiple G-quadruplexes in tandem cannot always be predicted from the structure of a single unit. Additionally, previous research has shown that the protein Insulin can bind the ILPR G-quadruplex formed from the repeat ‘a’, raising the intriguing possibility that Insulin may be directly involved in its own self-regulation. Here we have shown that the protein Insulin can interact specifically with the predominant G-quadruplex formed from the repeat ‘a’ over other ILPR G-quadruplexes, and that the loop nucleotides of the G-quadruplex play a decisive role in the G-quadruplex conformation, which directly determines Insulin affinity. Collectively, this study will aid in learning more about the ILPR’s mechanism of sequence polymorphism as well as lay the ground work towards explaining its effect on Insulin transcription and the ILPR’s role in type I diabetes. Furthermore, the work here provides additional evidence to the understanding of G-quadruplex polymorphism in general, which will be essential in reaching a more complete understanding of the complexities of biological regulation by these unique DNA structures.
Advisors/Committee Members: Basu, Soumitra.
Subjects: Biochemistry
Keywords: G-quadruplex, ILPR
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