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Full-Text Articles in Chemistry

Reactivity Of Acyclic (Pentadienyl)Iron(1+) Cations: Synthetic Studies Directed Toward The Frondosins, Do W. Lee, Rajesh K. Pandey, Sergey V. Lindeman, William A. Donaldson Nov 2011

Reactivity Of Acyclic (Pentadienyl)Iron(1+) Cations: Synthetic Studies Directed Toward The Frondosins, Do W. Lee, Rajesh K. Pandey, Sergey V. Lindeman, William A. Donaldson

Chemistry Faculty Research and Publications

A short, 4-step route to the scaffold of frondosin A and B is reported. The [1-methoxycarbonyl-5-(2′,5′-dimethoxyphenyl)pentadienyl]Fe(CO)3+ cation was prepared in two steps from (methyl 6-oxo-2,4-hexadienoate)Fe(CO)3. Reaction of this cation with isopropenyl Grignard or cyclohexenyllithium reagents affords (2-alkenyl-5-aryl-1-methoxycarbonyl-3-pentene-1,5-diyl)Fe(CO)3 along with other addition products. Oxidative decomplexation of these (pentenediyl)iron complexes, utilizing CuCl2, affords 6-aryl-3-methoxycarbonyl-1,4-cycloheptadienes via the presumed intermediacy of a cis-divinylcyclopropane.


Removal Of 2,4-Dichlorophenoxyacetic Acid By Calcined Zn–Al–Zr Layered Double Hydroxide, Allen Chaparadza, Jeanne Hossenlopp Nov 2011

Removal Of 2,4-Dichlorophenoxyacetic Acid By Calcined Zn–Al–Zr Layered Double Hydroxide, Allen Chaparadza, Jeanne Hossenlopp

Chemistry Faculty Research and Publications

The adsorption equilibrium, kinetics, and thermodynamics of removal of 2,4-dichlorophenoxy-acetic acid (2,4-D) from aqueous solutions by a calcined Zn–Al layered double hydroxide incorporated with Zr4+ were studied with respect to time, temperature, pH, and initial 2,4-D concentration. Zr4+ incorporation into the LDH was used to enhance 2,4-D uptake by creating higher positive charges and surface/layer modification of the adsorbent. The LDH was capable of removing up to 98% of 2,4-D from 5 to 400 ppm aqueous at adsorbent dosages of 500 and 5000 mg L−1. The adsorption was described by a Langmuir-type isotherm. The percentage 2,4-D …


Analysis Of Binding Site Hot Spots On The Surface Of Ras Gtpase, Greg Buhrman, Casey O'Connor, Brandon Zerbe, Bradley M. Kearney, Raeanne Napoleon, Elizaveta A. Kovrigina, Sandor Vajda, Dima Kozakov, Evgenii L. Kovrigin, Carla Mattos Nov 2011

Analysis Of Binding Site Hot Spots On The Surface Of Ras Gtpase, Greg Buhrman, Casey O'Connor, Brandon Zerbe, Bradley M. Kearney, Raeanne Napoleon, Elizaveta A. Kovrigina, Sandor Vajda, Dima Kozakov, Evgenii L. Kovrigin, Carla Mattos

Chemistry Faculty Research and Publications

We have recently discovered an allosteric switch in Ras, bringing an additional level of complexity to this GTPase whose mutants are involved in nearly 30% of cancers. Upon activation of the allosteric switch, there is a shift in helix 3/loop 7 associated with a disorder to order transition in the active site. Here, we use a combination of multiple solvent crystal structures and computational solvent mapping (FTMap) to determine binding site hot spots in the “off” and “on” allosteric states of the GTP-bound form of H-Ras. Thirteen sites are revealed, expanding possible target sites for ligand binding well beyond the …


Complete Determination Of The Pin1 Catalytic Domain Thermodynamic Cycle By Nmr Lineshape Analysis, Alexander I. Greenwood, Monique J. Rogals, Soumya De, Kun Ping Lu, Evgenii L. Kovrigin, Linda K. Nicholson Sep 2011

Complete Determination Of The Pin1 Catalytic Domain Thermodynamic Cycle By Nmr Lineshape Analysis, Alexander I. Greenwood, Monique J. Rogals, Soumya De, Kun Ping Lu, Evgenii L. Kovrigin, Linda K. Nicholson

Chemistry Faculty Research and Publications

The phosphorylation-specific peptidyl-prolyl isomerase Pin1 catalyzes the isomerization of the peptide bond preceding a proline residue between cis and trans isomers. To best understand the mechanisms of Pin1 regulation, rigorous enzymatic assays of isomerization are required. However, most measures of isomerase activity require significant constraints on substrate sequence and only yield rate constants for the cis isomer, kciscatand apparent Michaelis constants, KAppM . By contrast, NMR lineshape analysis is a powerful tool for determining microscopic rates and populations of each state in a complex binding scheme. The isolated catalytic domain of Pin1 was employed as …


An In Vitro Spectroscopic Analysis To Determine The Chemical Composition Of The Precipitate Formed By Mixing Sodium Hypochlorite And Chlorhexidine, James B. Nowicki, Daniel S. Sem Jul 2011

An In Vitro Spectroscopic Analysis To Determine The Chemical Composition Of The Precipitate Formed By Mixing Sodium Hypochlorite And Chlorhexidine, James B. Nowicki, Daniel S. Sem

Chemistry Faculty Research and Publications

Introduction—The purpose of this in vitro study was to determine the chemical composition of the precipitate formed by mixing sodium hypochlorite (NaOCl) and Chlorhexidine (CHX), and relative molecular weight of the components.

Methods—Using commercially available chlorhexidine gluconate (CHXg), a 2% solution was formed and mixed in a 1:1 ratio with commercially available NaOCl producing a brown precipitate. The precipitate as well as a mixture of precipitate and pure chlorhexidine diacetate (CHXa) was then analyzed using 1D and 2D NMR spectroscopy.

Results—The 1D and 2D NMR spectra were fully assigned, in terms of chemical shifts of all proton …


Calcium Carbonate And Ammonium Polyphosphate-Based Flame Retardant Composition For Polypropylene, Sarang Deodhar, Kadhiravan Shanmuganathan, Qinguo Fan, Charles A. Wilkie, Maurius C. Costache, Nicholas A. Dembsey, Prabir K. Patra May 2011

Calcium Carbonate And Ammonium Polyphosphate-Based Flame Retardant Composition For Polypropylene, Sarang Deodhar, Kadhiravan Shanmuganathan, Qinguo Fan, Charles A. Wilkie, Maurius C. Costache, Nicholas A. Dembsey, Prabir K. Patra

Chemistry Faculty Research and Publications

The chemical mode of action as a flame retardant of calcium carbonate nanoparticles combined with ammonium polyphosphate in polypropylene was investigated. Reduction in burning rates for 0.5 mm thick samples were observed without appreciable char formation up to 30 wt % loading of additives. Thermogravimetric analysis (TGA) of the mixture of CaCO3 and ammonium polyphosphate (APP) showed that calcium carbonate nanoparticles react with ammonium polyphosphate before the degradation of the phosphate chains. TGA–FTIR studies of the polymer composite samples and powder mixtures of the additives confirmed the evolution of ammonia and carbon dioxide due to interaction between the additives. …


Eva-Layered Double Hydroxide (Nano)Composites: Mechanism Of Fire Retardancy, Xiaolan Wang, Rajendra Rathore, Ponusa Songtipya, Maria Del Mar Jimenez-Gasco, Evangelos Manias, Charles A. Wilkie Mar 2011

Eva-Layered Double Hydroxide (Nano)Composites: Mechanism Of Fire Retardancy, Xiaolan Wang, Rajendra Rathore, Ponusa Songtipya, Maria Del Mar Jimenez-Gasco, Evangelos Manias, Charles A. Wilkie

Chemistry Faculty Research and Publications

Composites of ethylene-vinyl acetate copolymer with two different layered double hydroxides have been obtained by melt blending and these have been characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, thermogravimetric analysis connected to mass spectroscopy and cone calorimetry. There is some small difference in dispersion between the zinc-containing and the magnesium-containing layered double hydroxides in EVA, but both these are microcomposites with good dispersion at the micrometer level and relatively poor dispersion at the nanometer level. There is a good reduction in the peak heat release rate at 10% LDH loading. In addition to chain stripping, which involves the …


Synthesis Of Hydroxy- And Polyhydroxy-Substituted 1,3-Diaminocyclohexanes, Anobick Sar, Sergey V. Lindeman, William A. Donaldson Mar 2011

Synthesis Of Hydroxy- And Polyhydroxy-Substituted 1,3-Diaminocyclohexanes, Anobick Sar, Sergey V. Lindeman, William A. Donaldson

Chemistry Faculty Research and Publications

The synthesis of hydroxy-trans-1,3-diaminocyclo­hexanes based on nitroso-Diels-Alder cycloaddition of (cyclohexadienyl)phthalimide is reported.


Alteration Of Hydrogen Bonding In The Vicinity Of Histidine 48 Disrupts Millisecond Motions In Rnase A, Nicolet Doucet, Gennady Khirich, Evgenii L. Kovrigin, J. Patrick Loria Jan 2011

Alteration Of Hydrogen Bonding In The Vicinity Of Histidine 48 Disrupts Millisecond Motions In Rnase A, Nicolet Doucet, Gennady Khirich, Evgenii L. Kovrigin, J. Patrick Loria

Chemistry Faculty Research and Publications

The motion of amino acid residues on the millisecond (ms) time scale is involved in the tight regulation of catalytic function in numerous enzyme systems. Using a combination of mutational, enzymological, and relaxation-compensated 15N Carr−Purcell−Meiboom−Gill (CPMG) methods, we have previously established the conformational significance of the distant His48 residue and the neighboring loop 1 in RNase A function. These studies suggested that RNase A relies on an intricate network of hydrogen bonding interactions involved in propagating functionally relevant, long-range ms motions to the catalytic site of the enzyme. To further investigate the dynamic importance of this H-bonding network, this …


Direct Patterning Of A Cyclotriveratrylene Derivative For Directed Self-Assembly Of C60, Zachary R. Osner, Dorjderem Nyamjav, Richard C. Holz, Daniel P. Becker Jan 2011

Direct Patterning Of A Cyclotriveratrylene Derivative For Directed Self-Assembly Of C60, Zachary R. Osner, Dorjderem Nyamjav, Richard C. Holz, Daniel P. Becker

Chemistry Faculty Research and Publications

A novel apex-modified cyclotriveratrylene (CTV) derivative with an attached thiolane-containing lipoic acid linker was directly patterned onto gold substrates via dip-pen nanolithography (DPN). The addition of a dithiolane-containing linker to the apex of CTV provides a molecule that can adhere to a gold surface with its bowl-shaped cavity directed away from the surface, thereby providing a surface-bound CTV host that can be used for the directed assembly of guest molecules. Subsequent exposure of these CTV microarrays to C60 in toluene resulted in the directed assembly of predesigned, spatially controlled, high-density microarrays of C60. The molecular recognition capabilities …


Recent Advances In The Synthetic And Mechanistic Aspects Of The Ruthenium-Catalyzed Carbon-Heteroatom Bond Forming Reactions Of Alkenes And Alkynes, Chae S. Yi Jan 2011

Recent Advances In The Synthetic And Mechanistic Aspects Of The Ruthenium-Catalyzed Carbon-Heteroatom Bond Forming Reactions Of Alkenes And Alkynes, Chae S. Yi

Chemistry Faculty Research and Publications

The group’s recent advances in catalytic carbon-to-heteroatom bond forming reactions of alkenes and alkynes are described. For the C–O bond formation reaction, a well-defined bifunctional ruthenium-amido catalyst has been successfully employed for the conjugate addition of alcohols to acrylic compounds. The ruthenium-hydride complex (PCy3)2(CO)RuHCl was found to be a highly effective catalyst for the regioselective alkyne-to-carboxylic acid coupling reaction in yielding synthetically useful enol ester products. Cationic ruthenium-hydride catalyst generated in-situ from (PCy3)2(CO)RuHCl/HBF4·OEt2 was successfully utilized for both the hydroamination and related C–N bond forming reactions of alkenes. For …


Direct Patterning Of Silanized-Biomolecules On Semiconductor Surfaces, Dorjderem Nyamjav, Richard C. Holz Dec 2010

Direct Patterning Of Silanized-Biomolecules On Semiconductor Surfaces, Dorjderem Nyamjav, Richard C. Holz

Chemistry Faculty Research and Publications

A novel approach to pattern silanized-biomolecules directly onto glass (SiOx) substrates via Dip-Pen nanolithography (DPN) and microcontact printing (μCP) is presented. Subsequent hybridization reactions of DPN patterned silanized-DNA with its complementary strands provide “proof-of-concept” that the patterned oligonucleotides maintain their biological activities. The fabrication strategy does not require premodification of substrates and offers a cheap and robust way to immobilize molecules on electronically important semiconductor surfaces.


Study On Intumescent Flame Retarded Polystyrene Composites With Improved Flame Retardancy, Hongdian Lu, Charles A. Wilkie Dec 2010

Study On Intumescent Flame Retarded Polystyrene Composites With Improved Flame Retardancy, Hongdian Lu, Charles A. Wilkie

Chemistry Faculty Research and Publications

The flame retardancy and thermal stability of ammonium polyphosphate/tripentaerythritol (APP/TPE) intumescent flame retarded polystyrene composites (PS/IFR) combined with organically-modified layered inorganic materials (montmorillonite clay and zirconium phosphate), nanofiber (multiwall carbon nanotubs), nanoparticle (Fe2O3) and nickel catalyst were evaluated by cone calorimetry, microscale combustion calorimetry (MCC) and thermogravimetric analysis (TGA). Cone calorimetry revealed that a small substitution of IFR by most of these fillers (≤2%) imparted substantial improvement in flammability performance. The montmorillonite clay exhibited the highest efficiency in reducing the peak heat release rate of PS/IFR composite, while zirconium phosphate modified with C21H26 …


Chelate-Assisted Oxidative Coupling Reaction Of Arylamides And Unactivated Alkenes: Mechanistic Evidence For Vinyl C–H Bond Activation Promoted By An Electrophilic Ruthenium-Hydride Catalyst, Ki Hyeok Kwon, Do W. Lee, Chae S. Yi Oct 2010

Chelate-Assisted Oxidative Coupling Reaction Of Arylamides And Unactivated Alkenes: Mechanistic Evidence For Vinyl C–H Bond Activation Promoted By An Electrophilic Ruthenium-Hydride Catalyst, Ki Hyeok Kwon, Do W. Lee, Chae S. Yi

Chemistry Faculty Research and Publications

The cationic ruthenium hydride complex [(η6-C6H6)(PCy3)(CO)RuH]+BF4 was found to be a highly regioselective catalyst for the oxidative C−H coupling reaction of aryl-substituted amides and unactivated alkenes to give o-alkenylamide products. The kinetic and spectroscopic analyses support a mechanism involving a rapid vinyl C−H activation followed by a rate-limiting C−C bond formation step.


The Utility Of Nanocomposites In Fire Retardancy, Linjiang Wang, Xuejun He, Charles A. Wilkie Sep 2010

The Utility Of Nanocomposites In Fire Retardancy, Linjiang Wang, Xuejun He, Charles A. Wilkie

Chemistry Faculty Research and Publications

Nanocomposites have been shown to significantly reduce the peak heat release rate, as measured by cone calorimetry, for many polymers but they typically have no effect on the oxygen index or the UL-94 classification. In this review, we will cover what is known about the processes by which nanocomposite formation may bring this about. Montmorillonite will be the focus in this paper but attention will also be devoted to other materials, including carbon nanotubes and layered double hydroxides. A second section will be devoted to combinations of nanocomposite formation with conventional (and unconventional) fire retardants. The paper will conclude with …


The Effect Of Boron-Containing Layered Hydroxy Salt (Lhs) On The Thermal Stability And Degradation Kinetics Of Poly (Methyl Methacrylate), Stephen Majoni, Shengpei Su, Jeanne Hossenlopp Sep 2010

The Effect Of Boron-Containing Layered Hydroxy Salt (Lhs) On The Thermal Stability And Degradation Kinetics Of Poly (Methyl Methacrylate), Stephen Majoni, Shengpei Su, Jeanne Hossenlopp

Chemistry Faculty Research and Publications

A boron-containing layered hydroxy salt (LHS), ZHTMDBB, was prepared and compounded with a highly flammable synthetic polymer, poly (methyl methacrylate) {PMMA}, via melt blending: the composite structure was intercalated with poor dispersion. The effect of this LHS on the flammability, thermal stability and degradation kinetics of PMMA was investigated via cone calorimetry and thermogravimetric analysis. The addition of 3-10% by mass of ZHTMDBB to PMMA resulted in significant reduction of peak heat release rate (22-48%) of the polymer and improvements in thermal stability were observed in both air and nitrogen. Effective activation energies for the degradation process were evaluated using …


Chain-Selective And Regioselective Ethylene And Styrene Dimerization Reactions Catalyzed By A Well-Defined Cationic Ruthenium-Hydride Complex: New Insights On The Styrene Dimerization Mechanism, Do W. Lee, Chae S. Yi Aug 2010

Chain-Selective And Regioselective Ethylene And Styrene Dimerization Reactions Catalyzed By A Well-Defined Cationic Ruthenium-Hydride Complex: New Insights On The Styrene Dimerization Mechanism, Do W. Lee, Chae S. Yi

Chemistry Faculty Research and Publications

The cationic ruthenium hydride complex [(η6-C6H6)(PCy3)(CO)RuH]+BF4 was found to be a highly regioselective catalyst for the ethylene dimerization reaction to give 2-butene products (TOF = 1910 h−1, >95% selectivity for 2-butenes). The dimerization of styrene exclusively produced the head-to-tail dimer (E)-PhCH(CH3)CH═CHPh at an initial turnover rate of 2300 h−1. A rapid and extensive H/D exchange between the vinyl hydrogens of styrene-d8 and 4-methoxystyrene was observed within 10 min without forming the dimer products at room temperature. The inverse …


X-Ray Structure Of Mer-[Mo(Co)3(Pph3)(Κ2-Dppm)], Shishir Ghosh, Shariff E. Kabir, Faranza K. Camellia, Md. Kamal Hossain, Daniel T. Haworth, Sergey V. Lindeman, Tasneem A. Siddiquee, Dennis W. Bennett Aug 2010

X-Ray Structure Of Mer-[Mo(Co)3(Pph3)(Κ2-Dppm)], Shishir Ghosh, Shariff E. Kabir, Faranza K. Camellia, Md. Kamal Hossain, Daniel T. Haworth, Sergey V. Lindeman, Tasneem A. Siddiquee, Dennis W. Bennett

Chemistry Faculty Research and Publications

Treatment of [Mo(CO)3(NCMe)3] with bis(diphenylphosphino)methane (dppm) and triphenylphosphine (PPh3) at 50 °C afforded mer-[Mo(CO)3(PPh3)(κ2-dppm)] (1) in 55% yield which has been characterized by single crystal X-ray diffraction studies and spectroscopic measurements. Compound 1 crystallizes in the triclinic space group P−1 with a = 10.3449(6), b = 11.1570(6), c = 17.8961(10) Å, β = 80.8400(10)°, Z = 2 and V = 1959.8(2) Å3.


De Novo Synthesis Of Polyhydroxyl Aminocyclohexanes, Anobick Sar, Sergey V. Lindeman, William A. Donaldson Jul 2010

De Novo Synthesis Of Polyhydroxyl Aminocyclohexanes, Anobick Sar, Sergey V. Lindeman, William A. Donaldson

Chemistry Faculty Research and Publications

The syntheses of 12 stereochemically diverse polyhydroxyl aminocyclohexane (“aminocyclitols”) derivatives are described. These short syntheses require 2–5 steps from N-(2,4-cyclohexadien-1-yl)phthalimide, which is prepared in two steps from tricarbonyl(cyclohexadienyl)iron(1+). The relative stereochemistries of the aminocyclitols were assigned by 1H NMR spectroscopy as well as X-ray diffraction analysis.


Regioselective Formation Of Α-Vinylpyrroles From The Ruthenium-Catalyzed Coupling Reaction Of Pyrroles And Terminal Alkynes Involving C–H Bond Activation, Ruili Gao, Chae S. Yi May 2010

Regioselective Formation Of Α-Vinylpyrroles From The Ruthenium-Catalyzed Coupling Reaction Of Pyrroles And Terminal Alkynes Involving C–H Bond Activation, Ruili Gao, Chae S. Yi

Chemistry Faculty Research and Publications

The cationic ruthenium catalyst Ru3(CO)12/NH4PF6 was found to be highly effective for the intermolecular coupling reaction of pyrroles and terminal alkynes to give gem-selective α-vinylpyrroles. The carbon isotope effect on the α-pyrrole carbon and the Hammett correlation from a series of para-substituted N-arylpyrroles (ρ = −0.90) indicate a rate-limiting C−C bond formation step of the coupling reaction.


Mixed-Metal Cluster Synthesis: [Re(Co)3(Μ-S2Nc7H4)]2 As A Precursor For Tri- And Tetranuclear 2-Mercaptobenzothiolato Capped Clusters, Shishir Ghosh, Kamrun N. Khanam, Md. Kamal Hossain, G. M. Golzar Hossain, Daniel T. Haworth, Sergey V. Lindeman, Graeme Hogarth, Shariff E. Kabir Apr 2010

Mixed-Metal Cluster Synthesis: [Re(Co)3(Μ-S2Nc7H4)]2 As A Precursor For Tri- And Tetranuclear 2-Mercaptobenzothiolato Capped Clusters, Shishir Ghosh, Kamrun N. Khanam, Md. Kamal Hossain, G. M. Golzar Hossain, Daniel T. Haworth, Sergey V. Lindeman, Graeme Hogarth, Shariff E. Kabir

Chemistry Faculty Research and Publications

The readily prepared [Re2(CO)6(μ-S2NC7H4)2] (1) reacts with Group 8 trimetallic carbonyl clusters to yield new mixed-metal tri- and tetranuclear clusters. With [Os3(CO)10(NCMe)2] at 80 °C the tetranuclear mixed-metal cluster [Os3Re(CO)133-C7H4NS2)] (2) is the only isolated product. With Ru3(CO)12 products are dependent upon the reaction temperature. At 80 °C, a mixture of tetranuclear mixed-metal [Ru3Re(CO)133-C7H4NS2)] (5) …


Structural Basis For Catalysis By The Mono- And Dimetalated Forms Of The Dape-Encoded N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase, Boguslaw P. Nocek, Danuta Gillner, Yao Fan, Richard C. Holz, Andzrej Joachimiak Apr 2010

Structural Basis For Catalysis By The Mono- And Dimetalated Forms Of The Dape-Encoded N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase, Boguslaw P. Nocek, Danuta Gillner, Yao Fan, Richard C. Holz, Andzrej Joachimiak

Chemistry Faculty Research and Publications

Biosynthesis of lysine and meso-diaminopimelic acid in bacteria provides essential components for protein synthesis and construction of the bacterial peptidoglycan cell wall. The dapE operon enzymes synthesize both meso-diaminopimelic acid and lysine and, therefore, represent potential targets for novel antibacterials. The dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase functions in a late step of the pathway and converts N-succinyl-l,l-diaminopimelic acid to l,l-diaminopimelic acid and succinate. Deletion of the dapE gene is lethal to Helicobacter pylori and Mycobacterium smegmatis, indicating that DapE's are essential for cell growth and proliferation. Since there are no similar pathways in humans, inhibitors …


Inhibitors Of NΑ-Acetyl-L-Ornithine Deacetylase: Synthesis, Characterization And Analysis Of Their Inhibitory Potency, J. Hlavacek, J. Picha, V. Vanek, J. Jiracek, J. Slaninova, V. Fucik, M. Budesinsky, Danuta M. Gillner, Richard C. Holz Apr 2010

Inhibitors Of NΑ-Acetyl-L-Ornithine Deacetylase: Synthesis, Characterization And Analysis Of Their Inhibitory Potency, J. Hlavacek, J. Picha, V. Vanek, J. Jiracek, J. Slaninova, V. Fucik, M. Budesinsky, Danuta M. Gillner, Richard C. Holz

Chemistry Faculty Research and Publications

A series of N α-acyl (alkyl)- and N α-alkoxycarbonyl-derivatives of l- and d-ornithine were prepared, characterized, and analyzed for their potency toward the bacterial enzyme N α-acetyl-l-ornithine deacetylase (ArgE). ArgE catalyzes the conversion of N α-acetyl-l-ornithine to l-ornithine in the fifth step of the biosynthetic pathway for arginine, a necessary step for bacterial growth. Most of the compounds tested provided IC50 values in the μM range toward ArgE, indicating that they are moderately strong inhibitors. N α-chloroacetyl-l-ornithine (1g) was the best inhibitor tested toward ArgE providing an IC50 value of 85 …


Synergistic Effect Of Carbon Nanotubes And Decabromodiphenyl Oxide/Sb2O3 In Improving The Flame Retardancy Of Polystyrene, Hongdian Lu, Charles A. Wilkie Apr 2010

Synergistic Effect Of Carbon Nanotubes And Decabromodiphenyl Oxide/Sb2O3 In Improving The Flame Retardancy Of Polystyrene, Hongdian Lu, Charles A. Wilkie

Chemistry Faculty Research and Publications

Brominated flame retardant polystyrene composites were prepared by melt blending polystyrene, decabromodiphenyl oxide, antimony oxide, multi-wall carbon nanotubes and montmorillonite clay. Synergy between carbon nanotubes and clay and the brominated fire retardant was studied by thermogravimetric analysis, microscale combustion calorimetry and cone calorimetry. Nanotubes are more efficient than clay in improving the flame retardancy of the materials and promoting carbonization in the polystyrene matrix. Comparison of the results from the microscale combustion calorimeter and the cone calorimeter indicate that the rate of change of the peak heat release rate reduction in the microscale combustion calorimeter was slower than that in …


Investigation Of The Thermal Degradation Of Polyurea: The Effect Of Ammonium Polyphosphate And Expandable Graphite, Walid Awad, Charles A. Wilkie Mar 2010

Investigation Of The Thermal Degradation Of Polyurea: The Effect Of Ammonium Polyphosphate And Expandable Graphite, Walid Awad, Charles A. Wilkie

Chemistry Faculty Research and Publications

Polyurea was compounded with ammonium polyphosphate and expandable graphite and the morphology was studied by atomic force microscopy. The thermal degradation of polyurea and polyurea compounded with the additives has been investigated using thermogravimetry coupled with Fourier Transform infrared spectroscopy and mass spectrometry. The study of the thermal degradation and the parameters affecting the thermal stability of PU is essential in order to effectively design flame retarded polyurea. In general, thermal decomposition of polyurea occurs in two steps assigned to the degradation of the hard segment and soft segment, respectively. Adding these additives accelerates the decomposition reaction of polyurea. However, …


Intermolecular Dehydrative Coupling Reaction Of Arylketones With Cyclic Alkenes Catalyzed By A Well-Defined Cationic Ruthenium-Hydride Complex: A Novel Ketone Olefination Method Via Vinyl C–H Bond Activation, Chae S. Yi, Do W. Lee Mar 2010

Intermolecular Dehydrative Coupling Reaction Of Arylketones With Cyclic Alkenes Catalyzed By A Well-Defined Cationic Ruthenium-Hydride Complex: A Novel Ketone Olefination Method Via Vinyl C–H Bond Activation, Chae S. Yi, Do W. Lee

Chemistry Faculty Research and Publications

The cationic ruthenium−hydride complex [(η6-C6H6)(PCy3)(CO)RuH]+BF4 was found to be a highly effective catalyst for the intermolecular olefination reaction of aryl ketones with cycloalkenes. The preliminary mechanistic analysis revealed that an electrophilic ruthenium−vinyl complex is the key species for mediating both vinyl C−H bond activation and the dehydrative olefination steps of the coupling reaction.


Nmr Dynamics Investigation Of Ligand-Induced Changes Of Main And Side-Chain Arginine N-H’S In Human Phosphomevalonate Kinase, Andrew L. Olson, Sheng Cai, Timothy J. Herdendorf, Henry M. Miziorko, Daniel S. Sem Feb 2010

Nmr Dynamics Investigation Of Ligand-Induced Changes Of Main And Side-Chain Arginine N-H’S In Human Phosphomevalonate Kinase, Andrew L. Olson, Sheng Cai, Timothy J. Herdendorf, Henry M. Miziorko, Daniel S. Sem

Chemistry Faculty Research and Publications

Phosphomevalonate kinase (PMK) catalyzes phosphoryl transfer from adenosine triphosphate (ATP) to mevalonate 5-phosphate (M5P) on the pathway for synthesizing cholesterol and other isoprenoids. To permit this reaction, its substrates must be brought proximal, which would result in a significant and repulsive buildup of negative charge. To facilitate this difficult task, PMK contains 17 arginines and eight lysines. However, the way in which this charge neutralization and binding is achieved, from a structural and dynamics perspective, is not known. More broadly, the role of arginine side-chain dynamics in binding of charged substrates has not been experimentally defined for any protein to …


Thermal Degradation Of High-Temperature Fluorinated Polyimide And Its Carbon Fiber Composite, Andrea D. Adamczak, Adam A. Spriggs, Danielle M. Fitch, Walid Awad, Charles A. Wilkie, Jaime C. Grunlan Feb 2010

Thermal Degradation Of High-Temperature Fluorinated Polyimide And Its Carbon Fiber Composite, Andrea D. Adamczak, Adam A. Spriggs, Danielle M. Fitch, Walid Awad, Charles A. Wilkie, Jaime C. Grunlan

Chemistry Faculty Research and Publications

No abstract provided.


An In Vitro Spectroscopic Analysis To Determine Whether Para-Chloroaniline Is Produced From Mixing Sodium Hypochlorite And Chlorhexidine, John Thomas, Daniel S. Sem Feb 2010

An In Vitro Spectroscopic Analysis To Determine Whether Para-Chloroaniline Is Produced From Mixing Sodium Hypochlorite And Chlorhexidine, John Thomas, Daniel S. Sem

Chemistry Faculty Research and Publications

Introduction: The purpose of this in vitro study was to determine whether para-chloroaniline (PCA) is formed through the reaction of mixing sodium hypochlorite (NaOCl) and chlorhexidine (CHX).

Methods: Initially, commercially available samples of chlorhexidine acetate (CHXa) and PCA were analyzed with 1H nuclear magnetic resonance (NMR) spectroscopy. Two solutions, NaOCl and CHXa, were warmed to 37ºC, and when mixed they produced a brown precipitate. This precipitate was separated in half, and pure PCA was added to 1 of the samples for comparison before they were each analyzed with 1H NMR spectroscopy.

Results: The peaks in …


Immobilization Of The Aminopeptidase From Aeromonas Proteolytica On Mg2+/Al3+ Layered Double Hydroxide Particles, Steven T. Frey, Stephanie L. Guilmet, Richard G. Egan Iii, Alyssa Bennett, Sarah R. Soltau, Richard C. Holz Jan 2010

Immobilization Of The Aminopeptidase From Aeromonas Proteolytica On Mg2+/Al3+ Layered Double Hydroxide Particles, Steven T. Frey, Stephanie L. Guilmet, Richard G. Egan Iii, Alyssa Bennett, Sarah R. Soltau, Richard C. Holz

Chemistry Faculty Research and Publications

A novel biomaterial formed by the immobilization of the Aminopeptidase from Aeromonas proteolytica (AAP) on synthetic Mg2+ and Al3+ ion-containing layered double hydroxide (LDH) particles was prepared. Immobilization of AAP on the LDH particles in a buffered, aqueous mixture is rapid such that the maximum loading capacity, 1 × 10−9 moles of AAP/mg LDH, is achieved in a few minutes. X-ray powder diffraction of LDH samples before and after treatment with AAP indicates that the enzyme does not intercalate between the layers of LDH, but instead binds to the surface. Treatment of AAP/LDH with various amounts of …