Physical Sciences and Mathematics Commons^™

Development And Implementation Of High-Throughput Snpgenotyping In Barley, Serdar Bozdag, Timothy J. Close, Prasanna R. Bhat, Stefano Lonardi, Yonghui Wu, Nils Rostoks, Luke Ramsay, Arnis Druka, Nils Stein, Jan T. Svensson, Steve Wanamaker, Mikeal L. Roose, Matthew J. Moscou, Shiaoman Chao, Rajeev K. Varshney, Peter Szucs, Kazuhiro Sato, Patrick M. Hayes, David E. Matthews, Andris Kleinhofs, Gary J. Muehlbauer, Joseph Deyoung, David F. Marshall, Kavitha Madishetty, Raymond D. Fenton, Pascal Condamine, Andreas Graner, Robbie Waugh

Mathematics, Statistics and Computer Science Faculty Research and Publications

Background

High density genetic maps of plants have, nearly without exception, made use of marker datasets containing missing or questionable genotype calls derived from a variety of genic and non-genic or anonymous markers, and been presented as a single linear order of genetic loci for each linkage group. The consequences of missing or erroneous data include falsely separated markers, expansion of cM distances and incorrect marker order. These imperfections are amplified in consensus maps and problematic when fine resolution is critical including comparative genome analyses and map-based cloning. Here we provide a new paradigm, a high-density consensus genetic map of …

Isolation And X-Ray Structural Characterization Of A Dicationic Homotrimer Of 2,3,6,7-Tetramethoxy-9,10-Dimethylanthracene Cation Radical, Matthew J. Modjewski, Ruchi Shukla, Sergey Lindeman, Rajendra Rathore

Chemistry Faculty Research and Publications

Electrochemical oxidation of 2,3,6,7-tetramethoxy-9,10-dimethylanthracene (1) showed that it undergoes a highly reversible electrochemical oxidation (E_ox = 0.81 V vs SCE) and forms a modestly stable cation-radical salt in solution. X-ray crystallography established that 1⁺SbCl₆^- crystallizes as a (centrosymmetric) dicationic homotrimer via a close cofacial association of a pair of cationic and one neutral molecule of 1 with an interplanar separation of ∼3.2 Å. The structure of the dicationic homotrimer was also reproduced by DFT calculations. Furthermore, the structure of a dicationic spiro adduct, formed by a slow decomposition of a solution of 1^{+ …}

Reactivity Of Phenyldi(2-Thienyl)Phosphine Towards Group 7 Metal Carbonyls: Carbon–Phosphorus Bond Activation, Shishir Ghosh, Alok K. Das, Noorjahan Begum, Daniel T. Haworth, Sergey Lindeman, James R. Gardinier, Tasneem A. Siddiquee, Dennis W. Bennett, Ebbe Nordlander, Graeme Hogarth, Shariff E. Kabir

Chemistry Faculty Research and Publications

Addition of phenyldi(2-thienyl)phosphine (PPhTh₂) to [Re₂(CO)_10−n(NCMe)_n] (n = 1, 2) affords the substitution products [Re₂(CO)_10−n(PhPTh₂)_n] (1, 2) together with small amounts of fac-[ClRe(CO)₃(PPhTh₂)₂] (3) (n = 2). Reaction of [Re₂(CO)₁₀] with PPhTh₂in refluxing xylene affords a mixture which includes 2, [Re₂(CO)₇(PPhTh₂)(μ-PPhTh)(μ-H)] (4), [Re₂(CO)₇(PPhTh₂)(μ-PPhTh)(μ-η¹,κ¹(S)-C₄H₃S)] (5) and …

Inhibitors Of Bacterial N-Succinyl-L,L-Diaminopimelic Acid Desuccinylase (Dape) And Demonstration Of In Vitro Antimicrobial Activity, Danuta Gillner, Nicola Armoush, Richard C. Holz, Daniel P. Becker

Chemistry Faculty Research and Publications

The dapE-encoded N-succinyl-L,L-diaminopimelic acid desuccinylase (DapE) is a critical bacterial enzyme for the construction of the bacterial cell wall. A screen biased toward compounds containing zinc-binding groups (ZBG’s) including thiols, carboxylic acids, boronic acids, phosphonates and hydroxamates has delivered a number of micromolar inhibitors of DapE from Haemophilus influenzae, including the low micromolar inhibitor L-captopril (IC₅₀ = 3.3 μM, K_i = 1.8 μM). In vitro antimicrobial activity was demonstrated for l-captopril against Escherichia coli.

Polymer Nanocomposites Using Zinc Aluminum And Magnesium Aluminum Oleate Layered Double Hydroxides: Effects Of The Polymeric Compatibilizer And Of Composition On The Thermal And Fire Properties Of Pp/Ldh Nanocomposites, Charles Manzi-Nshuti, Ponusa Songtipya, Evangelos Manias, Maria Del Mar Jimenez-Gasco, Jeanne Hossenlopp, Charles A. Wilkie

Chemistry Faculty Research and Publications

A series of five oleate-containing layered double hydroxides with varied ratios of zinc to magnesium, i.e., with the general formula Zn_2−yMg_yAl(OH)₆ [CH₃(CH₂)₇CHCH(CH₂)₇COO]·nH₂O, were synthesized and used to prepare nanocomposites of polypropylene (PP). The nanomaterials were characterized by elemental analysis, attenuated total reflection-infrared spectroscopy (ATR-IR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), while the composites were characterized by XRD, TGA, transmission electron microscopy (TEM) and cone calorimetry. The zinc-containing LDH showed better dispersion in the polymer at the micrometer level …

The Effects Of Intralayer Metal Composition Of Layered Double Hydroxides On Glass Transition, Dispersion, Thermal And Fire Properties Of Their Pmma Nanocomposites, Charles Manzi-Nshuti, Dan Chen, Shengpei Su, Charles A. Wilkie

Chemistry Faculty Research and Publications

A series of aluminum-containing layered double hydroxides (LDHs), containing Mg, Ca, Co, Ni, Cu and Zn as the divalent metals, have been prepared by the co-precipitation method and used to prepare nanocomposites of PMMA by in situ bulk polymerization. The additives were characterized by Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy (XRD) and thermogravimetric analysis while the polymer composites were characterized by XRD, transmission electron microscopy, differential scanning calorimetry and cone calorimetry. Polymerization of methyl methacrylate in the presence of these undecenoate LDHs results in composites with enhanced thermal stability. The glass transition temperatures of the composites and the pristine …

Scope And Mechanistic Investigations On The Solvent-Controlled Regio- And Stereoselective Formation Of Enol Esters From The Ruthenium-Catalyzed Coupling Reaction Of Terminal Alkynes And Carboxylic Acids, Chae S. Yi, Ruili Gao

Chemistry Faculty Research and Publications

The ruthenium-hydride complex (PCy₃)₂(CO)RuHCl was found to be a highly effective catalyst for the alkyne-to-carboxylic acid coupling reaction to give synthetically useful enol ester products. A strong solvent effect was observed for the ruthenium catalyst in modulating the activity and selectivity; the coupling reaction in CH₂Cl₂ led to the regioselective formation of gem-enol ester products, while the stereoselective formation of (Z)-enol esters was obtained in THF. The coupling reaction was found to be strongly inhibited by PCy₃. The coupling reaction of both PhCO₂H/PhC≡CD and PhCO_{2 …}

Design And Implementation Of S-Marks: A Secure Middleware For Pervasive Computing Applications, Sheikh Iqbal Ahamed, Haifeng Li, Nilothpal Talukder, Mehrab Monjur, Chowdhury Sharif Hasan

Mathematics, Statistics and Computer Science Faculty Research and Publications

As portable devices have become a part of our everyday life, more people are unknowingly participating in a pervasive computing environment. People engage with not a single device for a specific purpose but many devices interacting with each other in the course of ordinary activity. With such prevalence of pervasive technology, the interaction between portable devices needs to be continuous and imperceptible to device users. Pervasive computing requires a small, scalable and robust network which relies heavily on the middleware to resolve communication and security issues. In this paper, we present the design and implementation of S-MARKS which incorporates device …

Manipulating Self-Assembly In Silver(I) Complexes Of 1,3-Di-N-Pyrazolylorganyls, Brendan J. Liddle, Daniel Hall, Sergey V. Lindeman, Mark D. Smith, James R. Gardinier

Chemistry Faculty Research and Publications

Three di-N-pyrazolylorganyls with different conformational flexibilities in the three-atom organyl spacers have been prepared, and the self-assembly properties with AgBF₄ have been studied both in solution and in the solid state. All ligands give low-coordinate silver(I) centers that are capable of participating in multiple noncovalent interactions, but only the rigid 1,8-dipyrazolylnaphthalene ligand promotes very short Ag−Ag contacts.

Decarbonylation Reaction Of [Os3(Co)10(Μ-H)(Μ-Sn2C4H5)]: X-Ray Structures Of The Two Isomers Of [Os3(Co)9(Μ-H)(Μ3-Η2-Sn2C4H5)], Shishir Ghosh, Shariff E. Kabir, Mansura Khatun, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett

Chemistry Faculty Research and Publications

The thermal reaction of [Os₃(CO)₁₀(μ-H)(μ-SN₂C₄H₅)] (1) at 110 °C afforded the new compound [Os₃(CO)₉(μ-H)(μ ₃-η ²-SN₂C₄H₅)] (2) in 84% yield. Compound 2 exists as two isomers, which differ in the disposition of the bridging hydride ligand. Both of the isomers of 2 have been characterized by a combination of elemental analysis, infrared and ¹H NMR spectroscopic data together with single crystal X-ray crystallography. The isomers …

Toward Charge-Neutral ‘Soft Scorpionates’: Coordination Chemistry And Lewis Acid Promoted Isomerization Of Tris(1-Organo-Imidazol-2-Ylthio)Methanes, Chengeto Gwengo, Rosalice M. Silva, Mark D. Smith, Sergey V. Lindeman, James R. Gardinier

Chemistry Faculty Research and Publications

Two tris(1-organo-imidazol-2-ylthio)methanes, HC(S-tim^R)₃ (R = organo = methyl, tert-butyl), have been prepared by a triphasic reaction between chloroform, the appropriate heterocycle, and saturated aqueous solutions of Na₂CO₃, in the presence of a phase transfer agent, (NBu₄)(Br). These ligands have been characterized both spectroscopically and by single crystal X-ray diffraction. The reaction chemistry of these potentially N,N,N-tripodal ligands with AgBF₄ was also explored where simple 1:1 coordination complexes could be isolated from reactions performed in THF solution at room temperature. The derivative {Ag[HC(S-tim^Me)₃]}(BF₄) was structurally …

Activation Of Tri(2-Furyl)Phosphine At A Dirhenium Centre: Formation Of Phosphido-Bridged Dirhenium Complexes, Shishir Ghosh, Mansura Khatun, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett, Graeme Hogarth, Ebbe Nordlander, Shariff E. Kabir

Chemistry Faculty Research and Publications

Reaction of tri(2-furyl)phosphine (PFu₃) with [Re₂(CO)_10−n(NCMe)_n] (n = 1, 2) at 40 °C gave the substituted complexes [Re₂(CO)_10−n(PFu₃)_n] (1 and 2), the phosphines occupying axial position in all cases. Heating [Re₂(CO)₁₀] and PFu₃ in refluxing xylene also gives 1 and 2 together with four phosphido-bridged complexes; [Re₂(CO)_8−n(PFu₃)_n(μ-PFu₂)(μ-H)] (n = 0, 1, 2) (3–5) and [Re₂(CO)_{6 …}

Recent Applications Of Acyclic (Diene)Iron Complexes And (Dienyl)Iron Cations In Organic Synthesis, William Donaldson, Subhabrata Chaudhury

Chemistry Faculty Research and Publications

Complexation of (tricarbonyl)iron to an acyclic diene serves to protect the ligand against oxidation, reduction, and cycloaddition reactions, whereas the steric bulk of this adjunct serves to direct the approaches of reagents to unsaturated groups attached to the diene onto the face opposite to iron. Furthermore, the Fe(CO)₃ moiety can serve to stabilize carbocation centers adjacent to the diene (i.e. pentadienyl-iron cations). Recent applications of these reactivities to the synthesis of polyene-, cyclopropane-, cycloheptadiene-, and cyclohexenone-containing natural products or analogues are presented.

Structure - Property Relationships Of New Polystyrene Nanocomposites Prepared From Initiator-Containing Layered Double Hydroxides Of Zinc Aluminum And Magnesium Aluminum, Charles Manzi-Nshuti, Dan Chen, Shengpei Shu, Charles A. Wilkie

Chemistry Faculty Research and Publications

Polystyrene/layered double hydroxides (PS/LDHs) nanocomposites were prepared by free radical polymerization of styrene monomer in the presence of LDHs intercalated with 4,4′-azobis(4-cyanopentanoate) anions (LDH–ACPA). XRD and ATR-IR are used to confirm that the materials produced are layered and the presence of the azo-initiator anions in these LDHs. These LDHs were used successfully to polymerize styrene and both XRD and TEM images of the composites support the formation of a mixed exfoliated-intercalated nanocomposite for ZnAl–ACPA but a microcomposite for MgAl–ACPA. The magnesium-containing LDHs decreased the glass transition temperature (T_g) of the composites while ZnAl–ACPA did not affect T …

Investigations Of 2-Thiazoline-2-Thiol As A Ligand: Synthesis And X-Ray Structures Of [Mn2(Co)7(Μ-Ns2C3H4)2] And [Mn(Co)3(Pph3)(Κ2-Ns2C3H4)], Shishir Ghosh, Faruque Ahmed, Rafique Al-Mamun, Daniel T. Haworth, Sergey V. Lindeman, Tasneem Siddiquee, Dennis W. Bennett, Shariff E. Kabir

Chemistry Faculty Research and Publications

Treatment of Mn₂(CO)₁₀ with 2-thiazoline-2-thiol in the presence of Me₃NO at room temperature afforded the dimanganese complexes [Mn₂(CO)₇(μ-NS₂C₃H₄)₂] (1) and [Mn₂(CO)₆(μ-NS₂C₃H₄)₂] (2) in 51 and 34% yields, respectively. Compound 1 was quantitatively converted into 2 when reacted with one equiv of Me₃NO. Reaction of 1 with triphenylphosphine at room temperature furnished the mononuclear complex [Mn(CO)₃(PPh₃)(κ ^{2 …}

Regioselective Intermolecular Coupling Reaction Of Arylketones And Alkenes Involving C-H Bond Activation Catalyzed By An In Situ Formed Cationic Ruthenium-Hydride Complex, Chae S. Yi, Do W. Lee

Chemistry Faculty Research and Publications

The cationic ruthenium hydride complex, formed in situ from the treatment of the tetranuclear ruthenium hydride complex {[(PCy₃)(CO)RuH]₄(μ₄-O)(μ₃-OH)(μ₂-OH)} with HBF₄·OEt₂, was found to be a highly effective catalyst for the intermolecular coupling reaction of arylketones and 1-alkenes to give the substituted indene and ortho-C−H insertion products. The formation of the indene products resulted from the initial alkene isomerization followed by regioselective ortho-C−H insertion of 2-alkene and dehydrative cyclization. The preliminary mechanistic studies revealed a rapid and reversible ortho-C−H bond activation followed by the …

Does Organic Modification Of Layered Double Hydroxides Improve The Fire Performance Of Pmma?, Calistor Nyambo, Dan Chen, Shengpei Shu, Charles A. Wilkie

Chemistry Faculty Research and Publications

The effect of modified layered double hydroxides (LDHs) on fire properties of poly(methyl methacrylate) is investigated. Organically-modified LDHs were prepared via rehydration of calcined hydrotalcite in a palmitate solution. Composites consisting of the organo-LDHs, unmodified hydrotalcite and calcined oxides were prepared with poly(methyl methacrylate) using melt blending. Thermal and fire properties of the (nano)composites were studied. The thermogravimetric analyses of the composites show an increase in thermal stability. Fire performance, evaluated using cone calorimetry, show that organically-modified LDHs composites give the best reductions in peak heat release rate, PHRR, i.e., 51% at 10% weight loading. Dispersion of the LDHs was …

Polymer Nanocomposites Using Zinc Aluminum And Magnesium Aluminum Oleate Layered Double Hydroxides: Effects Of Ldh Divalent Metals On Dispersion, Thermal, Mechanical And Fire Performance In Various Polymers, Charles Manzi-Nshuti, Ponusa Songtipya, Evangelos Manias, Maria Del Mar Jimenez-Gasco, Jeanne Hossenlopp, Charles Wilkie

Chemistry Faculty Research and Publications

Oleate-containing layered double hydroxides of zinc aluminum (ZnAl) and magnesium aluminum (MgAl) were used to prepare nanocomposites of polyethylene, poly(ethylene-co-butyl acrylate) and poly(methyl methacrylate). The additives and/or their polymer composites were characterized by X-ray diffraction, FTIR, elemental analysis, thermogravimetric analysis, mechanical testing, and cone calorimetry. The unusual packing of the monounsaturated oleate anions in the gallery of these LDHs facilitates the dispersion of these nanomaterials. The inorganic LDH protects the polymer from thermal oxidation, shown by enhancement of the thermal and fire properties of the corresponding polymer nanocomposites. There is a qualitative difference in the morphology of the …

Heterologous Expression And Purification Of Vibrio Proteolyticus (Aeromonas Proteolytica) Aminopeptidase: A Rapid Protocol, Mariam Hartley, Brian Bennett

Physics Faculty Research and Publications

Metalloaminopeptidases (mAPs) are enzymes that are involved in HIV infectivity, tumor growth and metastasis, angiogenesis, and bacterial infection. Investigation of structure–function relationships in mAPs is a prerequisite to rational design of anti-mAP chemotherapeutics. The most intensively studied member of the biomedically important dinuclear mAPs is the prototypical secreted Vibrio proteolyticus di-zinc aminopeptidase (VpAP). The wild-type enzyme is readily purified from the supernatant of cultures of V. proteolyticus, but recombinant variants require expression in Escherichia coli. A greatly improved system for the purification of recombinant VpAP is described. A VpAP-(His)₆ polypeptide, containing an N-terminal propeptide, and a C-terminal …

Fire Retardancy Of Bis[2-(Methacryloyloxy)Ethyl] Phosphate Modified Poly(Methyl Methacrylate) Nanocomposites Containing Layered Double Hydroxide And Montmorillonite, Linjiang Wang, Shengpei Shu, Dan Chen, Charles A. Wilkie

Chemistry Faculty Research and Publications

Copolymer nanocomposites were prepared by suspension copolymerization of bis[2-(methacryloyloxy)ethyl] phosphate and methyl methacrylate, together with bis(2-ethylhexyl) phosphate layered double hydroxide and a montmorillonite, Cloisite 93A. X-ray diffraction and transmission electron microscopy were used to characterize the morphology of nanocomposites and the dispersion of additives in the polymer. The thermal stability of the nanocomposites has been assessed by thermogravimetric analysis and cone calorimetry has been used to study the fire properties. Bis[2-(methacryloyloxy)ethyl] phosphate not only copolymerized with MMA, but also aids in the dispersion of additives in PMMA. The copolymer nanocomposites have better dispersion and higher degradation temperature and more char …

X-Ray Structural Characterization Of Charge Delocalization Onto The Three Equivalent Benzenoid Rings In Hexamethoxytriptycene Cation Radical, Vincent J. Chebny, Tushar S. Navale, Ruchi Shukla, Sergey V. Lindeman, Rajendra Rathore

Chemistry Faculty Research and Publications

Definitive X-ray crystallographic evidence is obtained for a single hole (or a polaron) to be uniformly distributed on the three equivalent 1,2-dimethoxybenzenoid (or veratrole) rings in the hexamethoxytriptycene cation radical. This conclusion is further supported by electrochemical analysis and by the observation of an intense near-IR transition in its electronic spectrum, as well as by comparison of the spectral and electrochemical characteristics with the model compounds containing one and two dimethoxybenzene rings.

Linking Conformation Change To Hemoglobin Activation Via Chain-Selective Time-Resolved Resonance Raman Spectroscopy On Protoheme/Mesoheme Hybrids, Gurusamy Balakrishnan, Mohammed Ibrahim, Piotr J. Mak, Jessica Hata, James R. Kincaid, Thomas G. Spiro

Chemistry Faculty Research and Publications

Time-resolved Resonance Raman spectra are reported for Hb tetramers, in which the αand β chains are selectively substituted with mesoheme. The Soret absorption band shift in meso- relative to protoheme permits chain-selective excitation of heme RR spectra. The evolution of these spectra following HbCO photolysis show that geminate recombination rates and yields are the same for the two chains, consistent with recent results on 15N-heme isotopomer hybrids. The spectra also reveal systematic shifts in the deoxy-heme ν4 and νFe-His) RR bands, which are anti-correlated. These shifts are resolved for the successive intermediates in the protein structure, which have previously been …

Human Glyoxalase Ii Contains An Fe(Ii)Zn(Ii) Center But Is Active As A Mononuclear Zn(Ii) Enzyme, Pattraranee Limphong, Ross M. Mckinney, Nicole E. Adams, Brian Bennett, Christopher A. Makaroff, Thusitha Gunasekera, Michael W. Crowder

Physics Faculty Research and Publications

Human glyoxalase II (Glx2) was overexpressed in rich medium and in minimal medium containing zinc, iron, or cobalt, and the resulting Glx2 analogues were characterized using metal analyses, steady-state and pre-steady-state kinetics, and NMR and EPR spectroscopies to determine the nature of the metal center in the enzyme. Recombinant human Glx2 tightly binds nearly 1 equiv each of Zn(II) and Fe. In contrast to previous reports, this study demonstrates that an analogue containing 2 equiv of Zn(II) cannot be prepared. EPR studies suggest that most of the iron in recombinant Glx2 is Fe(II). NMR studies show that Fe(II) binds to …

Analyzing The Binding Of Co(Ii)-Specific Inhibitors To The Methionyl Aminopeptidases From Escherichia Coli And Pyrococcus Furiosus, Sanghamitra Mitra, George Sheppard, Jieyi Wang, Brian Bennett, Richard C. Holz

Physics Faculty Research and Publications

Methionine aminopeptidases (MetAPs) represent a unique class of protease that is capable of the hydrolytic removal of an N-terminal methionine residue from nascent polypeptide chains. MetAPs are physiologically important enzymes; hence, there is considerable interest in developing inhibitors that can be used as antiangiogenic and antimicrobial agents. A detailed kinetic and spectroscopic study has been performed to probe the binding of a triazole-based inhibitor and a bestatin-based inhibitor to both Mn(II)- and Co(II)-loaded type-I (Escherichia coli) and type-II (Pyrococcus furiosus) MetAPs. Both inhibitors were found to be moderate competitive inhibitors. The triazole-type inhibitor was found to …

Variation Of Anions In Layered Double Hydroxides: Effects On Dispersion And Fire Properties, Linjiang Wang, Shengpei Shu, Dan Chen, Charles A. Wilkie

Chemistry Faculty Research and Publications

Layered double hydroxides (LDHs) are interesting materials for nanocomposite formation because one can vary the identity of the metals, the anions and the stoichiometry to see the effect of these on the ability of the nano-material to disperse in a polymer and to see what effect dispersion has on the properties of the polymer. In this study, the anions 2-ethylhexyl sulfate (SEHS), bis(2-ethylhexyl) phosphate (HDEHP) and dodecyl benzenesulfonate (SDBS) have been utilized as the charge balancing anions to synthesize organo-LDHs. Nanocomposites of poly(methyl methacrylate) (PMMA) and polystyrene (PS) with organo-LDHs were prepared both by melt blending and bulk polymerization. X-ray …

Comparative Study On The Flammability Of Polyethylene Modified With Commercial Fire Retardants And A Zinc Aluminum Oleate Layered Double Hydroxide, Charles Manzi-Nshuti, Jeanne Hossenlopp, Charles A. Wilkie

Chemistry Faculty Research and Publications

Polyethylene (PE) was modified by the addition of a layered hydroxide of zinc aluminum oleate (ZnAl) and/or commercial fire retardants. Commercial additives included: melamine polyphosphate (MPP), ammonium polyphosphate (APP), triphenol phosphate (TPP), resorcinol diphosphate (RDP), decabromophenyl oxide (DECA) and antimony oxide (AO). The thermal stability and the combustion behaviors of the new composite polymeric materials are evaluated in TGA experiments and cone calorimetry. At 20% total additive loading, APP and LDH enhance the thermal stability of the PE composites and favor char formation. ZnAl leads to the best reduction in the peak of heat release rate (PHRR), 72%, while the …

Analyzing The Binding Of Co(Ii)-Specific Inhibitors To The Methionyl Aminopeptidases From Escherichia Coli And Pyrococcus Furiosus, Sanghamitra Mitra, George Sheppard, Jieyi Wang, Brian Bennett, Richard C. Holz

Chemistry Faculty Research and Publications

Methionine aminopeptidases (MetAPs) represent a unique class of protease that is capable of the hydrolytic removal of an N-terminal methionine residue from nascent polypeptide chains. MetAPs are physiologically important enzymes; hence, there is considerable interest in developing inhibitors that can be used as antiangiogenic and antimicrobial agents. A detailed kinetic and spectroscopic study has been performed to probe the binding of a triazole-based inhibitor and a bestatin-based inhibitor to both Mn(II)- and Co(II)-loaded type-I (Escherichia coli) and type-II (Pyrococcus furiosus) MetAPs. Both inhibitors were found to be moderate competitive inhibitors. The triazole-type inhibitor was found to …

Subunit-Selective Interrogation Of Co Recombination In Carbonmonoxy Hemoglobin By Isotope-Edited Time-Resolved Resonance Raman Spectroscopy, Gurusamy Balakrishnan, Xiaojie Zhao, Edyta Podstawska, Leonard M. Proniewicz, James R. Kincaid, Thomas G. Spiro

Chemistry Faculty Research and Publications

Hemoglobin (Hb) is an allosteric tetrameric protein made up of αβ heterodimers. The α and β chains are similar, but are chemically and structurally distinct. To investigate dynamical differences between the chains, we have prepared tetramers in which the chains are isotopically distinguishable, via reconstitution with ¹⁵N-heme. Ligand recombination and heme structural evolution, following HbCO dissociation, was monitored with chain selectivity by resonance Raman (RR) spectroscopy. For α but not for β chains, the frequency of the ν₄ porphyrin breathing mode increased on the microsecond time scale. This increase is a manifestation of proximal tension in the Hb …

Material Properties Of Nanoclay Pvc Composites, Walid Awad, Gunter Beyer, Daphne Benderly, Wouter L. Ijdo, Ponusa Songtipya, Maria Del Mar Jimenez-Gasco, Evangelos Manias, Charles A. Wilkie

Chemistry Faculty Research and Publications

Nanocomposites of poly(vinyl chloride) have been prepared using both hectorite- and bentonite-based organically-modified clays. The organic modification used is tallow-triethanol-ammonium ion. The morphology of the systems was investigated using X-ray diffraction and transmission electron microscopy and these systems show that true nanocomposites, both intercalated and exfoliated systems, are produced. The mechanical properties have been evaluated and the modulus increases upon nanocomposite formation without a significant decrease in tensile strength or elongation at break. Thermal analysis studies using thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis were conducted. Thermal stability of the PVC systems was assessed using a standard thermal …

Aqueous Phase C-H Bond Oxidation Reaction Of Arylalkanes Catalyzed By A Water-Soluble Cationic Ru(Iii) Complex [(Pymox-Me2)2Rucl2]+Bf4-, Chae S. Yi, Ki Hyeok Kwon, Do W. Lee

Chemistry Faculty Research and Publications

The cationic complex [(pymox-Me₂)RuCl₂]⁺BF₄⁻ was found to be a highly effective catalyst for the C−H bond oxidation reaction of arylalkanes in water. For example, the treatment of ethylbenzene (1.0 mmol) with t-BuOOH (3.0 mmol) and 1.0 mol % of the Ru catalyst in water (3 mL) cleanly produced PhCOCH₃ at room temperature. Both a large kinetic isotope effect (k_H/k_D = 14) and a relatively large Hammett value (ρ = −1.1) suggest a solvent-caged oxygen rebounding mechanism via a Ru(IV)-oxo intermediate species.