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- Fire retardancy (8)
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- Oligomerically-modified clay (2)
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- Cytochrome c (1)
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Articles 1 - 30 of 31
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Attachment Of Motile Bacterial Cells To Prealigned Holed Microarrays, Sergey Rozhok, Zhifang Fan, Dorjderem Nyamjav, Chang Liu, Chad A. Mirkin, Richard C. Holz
Attachment Of Motile Bacterial Cells To Prealigned Holed Microarrays, Sergey Rozhok, Zhifang Fan, Dorjderem Nyamjav, Chang Liu, Chad A. Mirkin, Richard C. Holz
Chemistry Faculty Research and Publications
Construction of biomotors is an exciting area of scientific research that holds great promise for the development of new technologies with broad potential applications in areas such as the energy industry and medicine. Herein, we demonstrate the fabrication of prealigned microarrays of motile Escherichia coli bacterial cells on SiOx substrates. To prepare these arrays, holed surfaces with a gold layer on the bottom of the holes were utilized. The attachment of bacteria to the holes was achieved via nonspecific interactions using poly-l-lysine hydrobromide (PLL). Our data suggest that a single motile bacterial cell can be selectively attached to an individual …
The Proteomics Of N-Terminal Methionine Cleavage, Frédéric Frottin, Aude Martinez, Philippe Peynot, Sanghamitra Mitra, Richard C. Holz, Carmela Giglione, Thierry Meinnel
The Proteomics Of N-Terminal Methionine Cleavage, Frédéric Frottin, Aude Martinez, Philippe Peynot, Sanghamitra Mitra, Richard C. Holz, Carmela Giglione, Thierry Meinnel
Chemistry Faculty Research and Publications
Methionine aminopeptidase (MAP) is a ubiquitous, essential enzyme involved in protein N-terminal methionine excision. According to the generally accepted cleavage rules for MAP, this enzyme cleaves all proteins with small side chains on the residue in the second position (P1′), but many exceptions are known. The substrate specificity of Escherichia coli MAP1 was studied in vitro with a large (>120) coherent array of peptides mimicking the natural substrates and kinetically analyzed in detail. Peptides with Val or Thr at P1′ were much less efficiently cleaved than those with Ala, Cys, Gly, Pro, or Ser in this position. Certain residues …
Styrenic Polymer Nanocomposites Based On An Oligomerically-Modified Clay With High Inorganic Content, Jinguo Zhang, David D. Jiang, Dongyan Wang, Charles A. Wilkie
Styrenic Polymer Nanocomposites Based On An Oligomerically-Modified Clay With High Inorganic Content, Jinguo Zhang, David D. Jiang, Dongyan Wang, Charles A. Wilkie
Chemistry Faculty Research and Publications
Clay was modified with an oligomeric surfactant containing styrene and lauryl acrylate units along with a small amount of vinylbenzyl chloride to permit the formation of an ammonium salt so that this can be attached to a clay. The oligomerically-modified clay contains 50% inorganic clay, and styrenic polymer nanocomposites, including those of polystyrene (PS), high-impact polystyrene (HIPS), styrene–acrylonitrile copolymer (SAN) and acrylonitrile–butadiene–styrene (ABS), were prepared by melt blending. The morphologies of the nanocomposites were evaluated by X-ray diffraction and transmission electron microscopy. Mixed intercalated/delaminated nanocomposites were formed for SAN and ABS while largely immiscible nanocomposites were formed for PS and …
Additional Evidence For The Migration Of Clay Upon Heating Of Clay–Polypropylene Nanocomposites From X-Ray Photoelectron Spectroscopy (Xps), Jianwei Hao, Menachem Lewin, Charles A. Wilkie, Jiangqi Wang
Additional Evidence For The Migration Of Clay Upon Heating Of Clay–Polypropylene Nanocomposites From X-Ray Photoelectron Spectroscopy (Xps), Jianwei Hao, Menachem Lewin, Charles A. Wilkie, Jiangqi Wang
Chemistry Faculty Research and Publications
The explanation for reduction in the peak heat release rate of polymer–clay nanocomposites which is normally accepted is that clay accumulates at the surface, forming a thermal shield which is also a barrier to mass transport. The process by which this clay arrives at the surface has never been described in print but the common assumption is that pyrolysis is required for clay accumulation to occur. In this work, X-ray photoelectron spectroscopy, a tool much more sensitive in surface analysis than conventional techniques, is used to probe the surface of polypropylene–clay nanocomposites that have been annealed at relatively low temperatures, …
A New Colorimetric Assay For Methionyl Aminopeptidases: Examination Of The Binding Of A New Class Of Pseudopeptide Analog Inhibitors, Sanghamitra Mitra, Anna M. Dygas-Holz, Jiri Jiracek, Miroslava Zertova, Lenka Zakova, Richard C. Holz
A New Colorimetric Assay For Methionyl Aminopeptidases: Examination Of The Binding Of A New Class Of Pseudopeptide Analog Inhibitors, Sanghamitra Mitra, Anna M. Dygas-Holz, Jiri Jiracek, Miroslava Zertova, Lenka Zakova, Richard C. Holz
Chemistry Faculty Research and Publications
A direct and convenient spectrophotometric assay has been developed for methionine aminopeptidases (MetAPs). The method employs the hydrolysis of a substrate that is a methionyl analogue of p-nitroaniline (l-Met-p-NA), which releases the chromogenic product p-nitroaniline. This chromogenic product can be monitored continuously using a UV–Vis spectrophotometer set at 405 nm. The assay was tested with the type I MetAP from Escherichia coli (EcMetAP-I) and the type II MetAP from Pyrococcus furiosus (PfMetAP-II). Using l-Met-p-NA, the kinetic constants kcat and Km were determined for EcMetAP-I and PfMetAP-II …
Crystal And Molecular Structure Of Bis(8-Phenylmenthyl) 2-(2-Methyl-5-Oxo-3-Cyclohexen-1-Yl)Propandioate, C42H54O5• Ch3Cn, Dennis W. Bennett, Tasneem A. Siddiquee, Daniel T. Haworth, Subhabrata Chaudhury, William Donaldson
Crystal And Molecular Structure Of Bis(8-Phenylmenthyl) 2-(2-Methyl-5-Oxo-3-Cyclohexen-1-Yl)Propandioate, C42H54O5• Ch3Cn, Dennis W. Bennett, Tasneem A. Siddiquee, Daniel T. Haworth, Subhabrata Chaudhury, William Donaldson
Chemistry Faculty Research and Publications
The X-ray crystal structure of the title compound, as crystallized from acetonitrile-water was determined. The relative stereochemistry of the cyclohexenone ring with respect to the 8-phenylmenthyl esters was determined. The title compound crystallizes in the noncentrosymmetric space group P21, with a=8.9850(10) Å, b=15.575(3) Å, c=14.478(2) Å, β=94.61(2)°, and D calc=1.118 g cm−3 for Z=2.
Nanostructured Layered Copper Hydroxy Dodecyl Sulfate: A Potential Fire Retardant For Poly(Vinyl Ester) (Pve), Everson Kandare, Grace Chigwada, Dongyan Wang, Charles A. Wilkie, Jeanne Hossenlopp
Nanostructured Layered Copper Hydroxy Dodecyl Sulfate: A Potential Fire Retardant For Poly(Vinyl Ester) (Pve), Everson Kandare, Grace Chigwada, Dongyan Wang, Charles A. Wilkie, Jeanne Hossenlopp
Chemistry Faculty Research and Publications
Composites of poly(vinyl ester) (PVE) with copper hydroxy dodecyl sulfate (CHDS) were prepared by thermal curing. The efficiency of the additive, CHDS, in reducing flammability is demonstrated via cone calorimetry and thermogravimetric analysis (TGA). The addition of 1-10% by mass of the CHDS additive resulted in significant increments in char formation (~4-11%) from thermogravimetric analysis (TGA). Incorporation of the CHDS into the polymer matrix at these low concentrations leads to substantial reductions in the total heat release (~20-30%) but no significant change in the peak heat release rate. The composite materials generally ignite more quickly, however, the flame extinguishes faster …
Polyethylene And Polypropylene Nanocomposites Based On Polymerically - Modified Clay Containing Alkylstyrene Units, Jinguo Zhang, Charles A. Wilkie
Polyethylene And Polypropylene Nanocomposites Based On Polymerically - Modified Clay Containing Alkylstyrene Units, Jinguo Zhang, Charles A. Wilkie
Chemistry Faculty Research and Publications
Sodium montmorillonite was modified with a new polymeric surfactant. The high molecular weight of the surfactant appears to have led to incomplete cation exchange of the clays, but did promote nanocomposite formation with polyethylene and polypropylene. X-ray diffraction combined with transmission electron microscopy revealed a mixed nanocomposite morphology. The thermal stability of the nanocomposites was evaluated by thermogravimetric analysis, while flammability of the nanocomposites was evaluated by cone calorimetry. A significant 40% reduction in peak heat release rate was observed at 10% organo-clay (3% inorganic clay) loading with an even higher 50% reduction at a loading level of 16% modified …
Novel Potentiometric And Optical Silver Ion-Selective Sensors With Subnanomolar Detection Limits, Zsófia Szigeti, Adam Malon, Tamás Vigassy, Viktor Csokai, Alajos Grün, Katarzyna Wygladacz, Nan Ye, Chao Xu, Vincent J. Chebny, István Bitter, Rajendra Rathore, Eric Bakker, Ernö Pretsch
Novel Potentiometric And Optical Silver Ion-Selective Sensors With Subnanomolar Detection Limits, Zsófia Szigeti, Adam Malon, Tamás Vigassy, Viktor Csokai, Alajos Grün, Katarzyna Wygladacz, Nan Ye, Chao Xu, Vincent J. Chebny, István Bitter, Rajendra Rathore, Eric Bakker, Ernö Pretsch
Chemistry Faculty Research and Publications
Ten Ag+-selective ionophores have been characterized in terms of their potentiometric selectivities and complex formation constants in solvent polymeric membranes. The compounds with π-coordination show much weaker interactions than those with thioether or thiocarbamate groups as the coordinating sites. Long-term studies with the best ionophores show that the lower detection limit of the best Ag+ sensors can be maintained in the subnanomolar range for at least 1 month. The best ionophores have also been characterized in fluorescent microspheres. The so far best lower detection limits of 3 × 10−11 M (potentiometrically) and 2 × 10−11 …
Probing Synergism, Antagonism, And Additive Effects In Poly(Vinyl Ester) (Pve) Composites With Fire Retardants, Everson Kandare, Grace Chigwada, Dongyan Wang, Charles Wilkie, Jeanne Hossenlopp
Probing Synergism, Antagonism, And Additive Effects In Poly(Vinyl Ester) (Pve) Composites With Fire Retardants, Everson Kandare, Grace Chigwada, Dongyan Wang, Charles Wilkie, Jeanne Hossenlopp
Chemistry Faculty Research and Publications
Potential fire retardants, including copper hydroxy dodecyl sulfate (CHDS), organically-modified montmorillonite (Cloisite 15A), and resorcinol di-phosphate (RDP), were added to pure poly(vinyl ester) (PVE) individually or in combinations at low concentration formulations. Thermogravimetric analysis and cone calorimetry were used to study the thermal stability and fire performance of the composites. Synergistic, antagonistic, and additive effects were observed depending on the specific formulation. Time to self-sustained combustion is greatly reduced, but the flame extinguishes faster, for the composites containing CROS alone or in combination with either RDP or Cloisite 15A compared to the virgin polymer. The presence of copper in PVE …
Faithful Estimation Of Dynamics Parameters From Cpmg Relaxation Dispersion Measurements, Evgueni Kovriguine, James G. Kempf, Michael J. Grey, J. Patrick Loria
Faithful Estimation Of Dynamics Parameters From Cpmg Relaxation Dispersion Measurements, Evgueni Kovriguine, James G. Kempf, Michael J. Grey, J. Patrick Loria
Chemistry Faculty Research and Publications
This work examines the robustness of fitting of parameters describing conformational exchange (kex, pa/b, and Δω) processes from CPMG relaxation dispersion data. We have analyzed the equations describing conformational exchange processes for the intrinsic inter-dependence of their parameters that leads to the existence of multiple equivalent solutions, which equally satisfy the experimental data. We have used Monte-Carlo simulations and fitting to the synthetic data sets as well as the direct 3-D mapping of the parameter space of kex, pa/b, and Δω to quantitatively assess …
Characterization Of The Transition State Of Functional Enzyme Dynamics, Evgueni Kovriguine, J. Patrick Loria
Characterization Of The Transition State Of Functional Enzyme Dynamics, Evgueni Kovriguine, J. Patrick Loria
Chemistry Faculty Research and Publications
Through characterization of the solvent isotope effect on protein dynamics, we have examined determinants of the rate limitation to enzyme catalysis. A global conformational change in Ribonuclease A limits the overall rate of catalytic turnover. Here we show that this motion is sensitive to solvent deuterium content; the isotope effect is 2.2, a value equivalent to the isotope effect on the catalytic rate constant. We further demonstrate that the protein motion possesses a linear proton inventory plot, indicating that a single proton is transferred in the transition state. These results provide compelling evidence for close coupling between enzyme dynamics and …
The High-Resolution Structures Of The Neutral And The Low Ph Crystals Of Aminopeptidase From Aeromonas Proteolytica, William Desmarais, David L. Bienvenue, Krzysztof P. Bzymek, Gregory A. Petsko, Dagmar Ringe, Richard C. Holz
The High-Resolution Structures Of The Neutral And The Low Ph Crystals Of Aminopeptidase From Aeromonas Proteolytica, William Desmarais, David L. Bienvenue, Krzysztof P. Bzymek, Gregory A. Petsko, Dagmar Ringe, Richard C. Holz
Chemistry Faculty Research and Publications
The aminopeptidase from Aeromonas proteolytica (AAP) contains two zinc ions in the active site and catalyzes the degradation of peptides. Herein we report the crystal structures of AAP at 0.95-Å resolution at neutral pH and at 1.24-Å resolution at low pH. The combination of these structures allowed the precise modeling of atomic positions, the identification of the metal bridging oxygen species, and insight into the physical properties of the metal ions. On the basis of these structures, a new putative catalytic mechanism is proposed for AAP that is likely relevant to all binuclear metalloproteases.
Styrenic Nanocomposites Prepared Using A Novel Biphenyl-Containing Clay, Grace Chigwada, Dongyan Wang, David D. Jiang, Charles A. Wilkie
Styrenic Nanocomposites Prepared Using A Novel Biphenyl-Containing Clay, Grace Chigwada, Dongyan Wang, David D. Jiang, Charles A. Wilkie
Chemistry Faculty Research and Publications
Montmorillonite was organically modified using an ammonium salt containing 4-acetylbiphenyl. This clay (BPNC16 clay) was used to prepare polystyrene (PS), acrylonitrile butadiene styrene (ABS) and high impact polystyrene (HIPS) nanocomposites. Polystyrene nanocomposites were prepared both by in situ bulk polymerisation and melt blending processes, while the ABS and HIPS nanocomposites were prepared only by melt blending. X-ray diffraction and transmission electron microscopy were used to confirm nanocomposite formation. Thermogravimetric analysis was used to evaluate thermal stability and the flammability properties were evaluated using cone calorimetry. By thermogravimetry, BPNC16 clay was found to show high thermal stability, and by cone calorimetry, …
Polyethylene And Polypropylene Nanocomposites Based On A Three Component Oligomerically-Modified Clay, Jinguo Zhang, David D. Jiang, Charles A. Wilkie
Polyethylene And Polypropylene Nanocomposites Based On A Three Component Oligomerically-Modified Clay, Jinguo Zhang, David D. Jiang, Charles A. Wilkie
Chemistry Faculty Research and Publications
Polyethylene and polypropylene nanocomposites were prepared using a novel oligomerically-modified clay that contains three components, styrene, lauryl acrylate and vinylbenzyl chloride. The nanocomposites were prepared by directly melt blending the polymers with the clay and they were characterized by X-ray diffraction and transmission electron microscopy, to understand their morphology, and their thermal stability, flammability and mechanical properties were evaluated using thermogravimetric analysis, cone calorimetry and mechanical testing, respectively. The reduction in peak heat release rate is about 60% at 5% inorganic clay loading and 70% at 8% inorganic clay loading.
Thermal Degradation Of Acetate-Intercalated Hydroxy Double And Layered Hydroxy Salts, Everson Kandare, Jeanne Hossenlopp
Thermal Degradation Of Acetate-Intercalated Hydroxy Double And Layered Hydroxy Salts, Everson Kandare, Jeanne Hossenlopp
Chemistry Faculty Research and Publications
Two hydroxy double salts (HDSs), zinc copper hydroxy acetate (ZCA) and zinc nickel hydroxy acetate (ZNA), and an analogous layered compound, zinc hydroxy acetate (ZHA), have been prepared by a coprecipitation method. The thermal degradation of these materials was characterized via thermogravimetric analysis (TGA), differential thermal analysis (DTA), and TGA coupled with Fourier transform infrared spectroscopy of gas-phase products, TGA-FTIR. Loss of physisorbed and interlayer H2O was observed between 50 and 150 °C for all compounds. Acetic acid, acetone, water, and CO2 were released at high temperatures with relative acetone yields found to be dependent on precursor identity, with very …
Thermal Stability And Degradation Kinetics Of Poly(Methyl Methacrylate)/Layered Copper Hydroxy Methacrylate Composites, Everson Kandare, Hongmei Deng, Dongyan Wang, Jeanne Hossenlopp
Thermal Stability And Degradation Kinetics Of Poly(Methyl Methacrylate)/Layered Copper Hydroxy Methacrylate Composites, Everson Kandare, Hongmei Deng, Dongyan Wang, Jeanne Hossenlopp
Chemistry Faculty Research and Publications
Poly(methyl methacrylate) (PMMA)/copper hydroxy methacrylate (CHM) composites were prepared via solution blending and bulk polymerization. Addition of 3% by weight of the CHM additive using solution blending resulted in a significant increment (~45°C) in thermogravimetric analysis (TGA) T50, the temperature at which 50% of the original polymeric mass is lost. The value T50 increased by 30°C for a PMMA composite with 4% CHM, synthesized via bulk polymerization. Activation energies, Ea, were calculated as a function of conversion fractions (TGA decomposition profile) for the polymeric materials. Analysis of multiple heating rate data using the Flynn–Wall– Ozawa …
Polystyrene Nanocomposites Based On Quinolinium And Pyridinium Surfactants, Grace Chigwada, Dongyan Wang, Charles A. Wilkie
Polystyrene Nanocomposites Based On Quinolinium And Pyridinium Surfactants, Grace Chigwada, Dongyan Wang, Charles A. Wilkie
Chemistry Faculty Research and Publications
In this paper pyridine and quinoline-containing salts were employed to modify montmorillonite. TGA analysis shows that the quinolinium modified clay has a higher thermal stability than the pyridinium modified clay. Polystyrene nanocomposites were prepared by in situ bulk polymerisation and direct melt blending using both clays. The X-ray diffraction and transmission electron microscopy results show the formation of intercalated structures. The 50% degradation temperature of the nanocomposites is increased and so is the amount of char from TGA analysis compared to the virgin polymer. Cone calorimetric results indicate that clay reduces the peak heat release rate and average mass loss …
Nmr Studies Of Escherichia Coli Acyl Carrier Protein: Dynamic And Structural Differences Of The Apo- And Holo-Forms, Yangmee Kim, Evgueni Kovriguine, Ziad Eletr
Nmr Studies Of Escherichia Coli Acyl Carrier Protein: Dynamic And Structural Differences Of The Apo- And Holo-Forms, Yangmee Kim, Evgueni Kovriguine, Ziad Eletr
Chemistry Faculty Research and Publications
Two indicators of conformational variability of Escherichia coli acyl carrier protein (ACP) have been investigated, namely backbone dynamics and chemical shift variations of ACP. Hydrophobic interactions between the 4′-PP prosthetic group and the hydrophobic pocket enclosed by the amphipathic helices resulted in chemical shift perturbations in the residues near the prosthetic group binding sites and contact sites in the hydrophobic pockets upon conversion from apo- to holo-forms. At pH 7.9, destabilization of ACP due to negative charge repulsions and the deprotonated state of His 75 resulted in observed chemical shift changes in the C-terminal region. Model-free analysis showed that the …
Flammability Of Styrenic Polymer Clay Nanocomposites Based On A Methyl Methacrylate Oligomerically-Modified Clay, Xiaoxia Zheng, David D. Jiang, Dongyan Wang, Charles A. Wilkie
Flammability Of Styrenic Polymer Clay Nanocomposites Based On A Methyl Methacrylate Oligomerically-Modified Clay, Xiaoxia Zheng, David D. Jiang, Dongyan Wang, Charles A. Wilkie
Chemistry Faculty Research and Publications
Nanocomposites of polystyrene, high impact polystyrene, acrylonitrile–butadiene–styrene terpolymer, polypropylene, and polyethylene were prepared using a methyl methacrylate oligomerically-modified clay by melt blending and the thermal stability and fire retardancy were studied. These nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry. The results show a mixed morphology, depending on the polymer.
Applications Of Acoustic Wave Devices For Sensing In Liquid Environments, Jeanne Hossenlopp
Applications Of Acoustic Wave Devices For Sensing In Liquid Environments, Jeanne Hossenlopp
Chemistry Faculty Research and Publications
Acoustic wave devices such as thickness shear mode (TSM) resonators and shear horizontal surface acoustic wave (SH-SAW) devices can be utilized for characterizing physical properties of liquids and for chemical sensor applications. Basic device configurations are reviewed and the relationships between experimental observables (frequency shifts and attenuation) and physical properties of liquids are presented. Examples of physical property (density and viscosity) determination and also of chemical sensing are presented for a variety of liquid phase applications. Applications of TSMs and polymer-coated guided SH-SAWs for chemical sensing and uncoated SH-SAWs for “electronic tongue” applications are also discussed.
Fire Properties Of Styrenic Polymer–Clay Nanocomposites Based On An Oligomerically-Modified Clay, Jinguo Zhang, David D. Jiang, Charles A. Wilkie
Fire Properties Of Styrenic Polymer–Clay Nanocomposites Based On An Oligomerically-Modified Clay, Jinguo Zhang, David D. Jiang, Charles A. Wilkie
Chemistry Faculty Research and Publications
An oligomerically-modified clay has been used to fabricate nanocomposites with styrenic polymers, such as polystyrene, high-impacted polystyrene, poly(styrene-co-acrylonitrile) and acrylonitrile–butadiene–styrene by melt blending. The clay dispersion was evaluated by X-ray diffraction and bright field transmission electron microscopy. All of the nanocomposites have a mixed delaminated/intercalated structure. The fire properties of nanocomposites were evaluated by cone calorimetry and the mechanical properties were also evaluated.
Enzyme Dynamics Along The Reaction Coordinate: Critical Role Of A Conserved Residue, Evgueni Kovriguine, J. Patrick Loria
Enzyme Dynamics Along The Reaction Coordinate: Critical Role Of A Conserved Residue, Evgueni Kovriguine, J. Patrick Loria
Chemistry Faculty Research and Publications
Conformational flexibility of the enzyme architecture is essential for biological function. These structural transitions often encompass significant portions of the enzyme molecule. Here, we present a detailed study of functionally relevant RNase A dynamics in the wild type and a D121A mutant form by NMR spin-relaxation techniques. In the wild-type enzyme, the dynamic properties are largely conserved in the apo, enzyme−substrate, and enzyme−product complexes. In comparison, mutation of aspartic acid 121 to alanine disrupts the timing of active-site dynamics, the product-release step, and global conformational changes, indicating that D121 plays a significant role in coordinating the dynamic events in RNase …
Thermal And Flame Properties Of Polyethylene And Polypropylene Nanocomposites Based On An Oligomerically–Modified Clay, Jinguo Zhang, David D. Jiang, Charles A. Wilkie
Thermal And Flame Properties Of Polyethylene And Polypropylene Nanocomposites Based On An Oligomerically–Modified Clay, Jinguo Zhang, David D. Jiang, Charles A. Wilkie
Chemistry Faculty Research and Publications
An oligomerically-modified clay was made using a surfactant which is the ammonium salt of an oligomer. The newly modified clay contains 37.5% inorganic clay and 62.5% oligomer. Polyethylene and polypropylene nanocomposites were made by melt blending the polymer with the oligomerically-modified clay in a Brabender mixer at various clay loadings. The structure of the nanocomposites was characterized by X-ray diffraction and transmission electron microscopy. Mechanical testing showed that the polyethylene nanocomposites had an enhanced Young's modulus and slightly decreased elongation, while the changes for polypropylene nanocomposites are small compared with the virgin polymers. The thermal stability and flame properties were …
The Redox Couple Of The Cytochrome C Cyanide Complex: The Contribution Of Heme Iron Ligation To The Structural Stability, Chemical Reactivity, And Physiological Behavior Of Horse Cytochrome C, Abel Schejter, Michael D. Ryan, Erica R. Blizzard, Chongyao Zhang, Emanuel Margoliash, Benjamin A. Feinberg
The Redox Couple Of The Cytochrome C Cyanide Complex: The Contribution Of Heme Iron Ligation To The Structural Stability, Chemical Reactivity, And Physiological Behavior Of Horse Cytochrome C, Abel Schejter, Michael D. Ryan, Erica R. Blizzard, Chongyao Zhang, Emanuel Margoliash, Benjamin A. Feinberg
Chemistry Faculty Research and Publications
Contrary to most heme proteins, ferrous cytochrome c does not bind ligands such as cyanide and CO. In order to quantify this observation, the redox potential of the ferric/ferrous cytochrome c–cyanide redox couple was determined for the first time by cyclic voltammetry. Its E0′ was −240 mV versus SHE, equivalent to −23.2 kJ/mol. The entropy of reaction for the reduction of the cyanide complex was also determined. From a thermodynamic cycle that included this new value for the cyt c cyanide complex E0′, the binding constant of cyanide to the reduced protein was estimated to …
Simultaneous Ejection Of Six Electrons At A Constant Potential By Hexakis(4-Ferrocenylphenyl)Benzene, Vincent J. Chebny, Dwairath Dhar, Sergey V. Lindeman, Rajendra Rathore
Simultaneous Ejection Of Six Electrons At A Constant Potential By Hexakis(4-Ferrocenylphenyl)Benzene, Vincent J. Chebny, Dwairath Dhar, Sergey V. Lindeman, Rajendra Rathore
Chemistry Faculty Research and Publications
A simple synthesis of a dendritic hexaferrocenyl electron donor (5) is described in which six ferrocene moieties are connected at the vertices of the propeller of the hexaphenylbenzene core. The molecular structure of 5 is confirmed by X-ray crystallography. An electrochemical analysis along with redox titrations (which are tantamount to coulometry) confirmed that it ejects six electrons at a single potential.
Highly Cooperative Tetrametallic Ruthenium-Μ-Oxo-Μ-Hydroxo Catalyst For The Alcohol Oxidation Reaction, Chae S. Yi, Tonya N. Zeczycki, Ilia A. Guzei
Highly Cooperative Tetrametallic Ruthenium-Μ-Oxo-Μ-Hydroxo Catalyst For The Alcohol Oxidation Reaction, Chae S. Yi, Tonya N. Zeczycki, Ilia A. Guzei
Chemistry Faculty Research and Publications
The tetrametallic ruthenium-oxo-hydroxo-hydride complex {[(PCy3)(CO)RuH]4(μ4-O)(μ3-OH)(μ2-OH)} (1) was synthesized in two steps from the monomeric complex (PCy3)(CO)RuHCl (2). The tetrameric complex 1 was found to be a highly effective catalyst for the transfer dehydrogenation of alcohols. Complex 1 showed a different catalytic activity pattern toward primary and secondary benzyl alcohols, as indicated by the Hammett correlation for the oxidation reaction of p-X-C6H4CH2OH (ρ = −0.45) and p-X-C6H4CH(OH)CH3 (ρ = +0.22) (X = …
Polystyrene Nanocomposites Based On An Oligomerically-Modified Clay Containing Maleic Anhydride, Xiaoxia Zheng, David D. Jiang, Charles A. Wilkie
Polystyrene Nanocomposites Based On An Oligomerically-Modified Clay Containing Maleic Anhydride, Xiaoxia Zheng, David D. Jiang, Charles A. Wilkie
Chemistry Faculty Research and Publications
An oligomerically-modified clay containing maleic anhydride was used to prepare polystyrene-clay nanocomposites by melt blending and the effect of this modified clay on the thermal stability and fire performance was studied. These nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry. The results show a mixed immiscible/intercalated/delaminated morphology. The maleic anhydride modified clay improved the compatibility between the clay and the polystyrene.
Janus Scorpionates: Supramolecular Tectons For The Directed Assembly Of Hard−Soft Alkali Metallopolymer Chains, Rosalice M. Silva, Chengeto Gwengo, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier
Janus Scorpionates: Supramolecular Tectons For The Directed Assembly Of Hard−Soft Alkali Metallopolymer Chains, Rosalice M. Silva, Chengeto Gwengo, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier
Chemistry Faculty Research and Publications
A new scorpionate ligand [HB(mtda)3-] containing mercaptothiadiazolyl (mtda) heterocyclic rings with both hard nitrogen donors and soft sulfur donors has been prepared. This new ligand, the Janus scorpionate, is a hybrid of a tris(pyrazolyl)borate and a tris(mercaptoimidazolyl)borate. The differential hard/soft character of the dissimilar donor groups in this bridging ligand was exploited for the controlled solid-state organization of homometallic and heterometallic alkali metal coordination polymers. Remarkably, in the case of sodium, coordination polymers with both acentric (with NaS3N3H kernels) and centric (with alternating NaN6 and NaS6H2 kernels) chains are …
Ligand-Promoted Solvent-Dependent Ionization And Conformational Equilibria Of Re(Co)3Br[Ch2(S-Tim)2] (Tim = 1-Methylthioimidazolyl). Crystal Structures Of Re(Co)3Br[Ch2(S-Tim)2] And {Re(Co)3(Ch3Cn)[Ch2(S-Tim)2]}(Pf6), Rosalice M. Silva, Brendan J. Liddle, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier
Ligand-Promoted Solvent-Dependent Ionization And Conformational Equilibria Of Re(Co)3Br[Ch2(S-Tim)2] (Tim = 1-Methylthioimidazolyl). Crystal Structures Of Re(Co)3Br[Ch2(S-Tim)2] And {Re(Co)3(Ch3Cn)[Ch2(S-Tim)2]}(Pf6), Rosalice M. Silva, Brendan J. Liddle, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier
Chemistry Faculty Research and Publications
The compounds Re(CO)3Br[CH2(S-tim)2] (1) and {Re(CO)3(CH3CN)[CH2(S-tim)2]}(PF6) (2), where tim is 1-methylthioimidazolyl, were prepared in high yields and characterized both in the solid state and in solution. The solid-state structures show that the ligand acts in a chelating binding mode where the eight-member chelate ring adopts twist-boat conformations in both compounds. A comparison of both solid-state IR data for CO stretching frequencies and the solution-phase voltammetric measurements for the Re1+/2+ couples between 1, 2, …