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Showing 1 to 20 of 27 for “"oxyanion"”.
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Oxyanion reduction in a non-heme iron system
… of nitrite. Herein, the reduction of other oxyanions, the halogen and selenium oxyanions and chromate, to furnish the iron(III)-oxo complex was explored. In Chapter 2, the reduction of the halogen oxyanions to form the iron(III)-oxo complex and an iron(II)-halide complex is detailed. The …
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Oxyanion Adsorption by Iron and Ruthenium Oxides: A Macroscopic, Spectroscopic, and Kinetic Investigation
The adsorption and desorption behavior of trace element contaminants was evaluated solids—goethite and ruthenium oxide. The importance of anion displacement as a mechanism responsible for arsenic release from iron oxides was investigated on goethite. The adsorption and polymerization of silicate on …
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Genetic relatedness of the family Rhodospirillaceae: Genome plasticity, chromosome heterogeneity, and chalcogenic oxyanion reductase activity in Rhodobacter sphaeroides
… at least fifteen other chalcogenic oxides and oxyanions has been demonstrated in the facultative photoheterotrophic bacterium, Rhodobacter (Rba.) sphaeroides. Detailed analyses have shown that HLR to at least one class of these oxyanions, the ""tellurite class"" (e.g., $\rm TeO\sb4\sp{2-},\ …
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Theoretical and experimental studies of slowly deacylating alpha-chymotrypsin acyl enzymes
… pulls the ester carbonyl group out of the oxyanion binding hole. This distortion of geometry raises the energy of activation for hydrolysis of the acyl enzyme by providing little stabilization of the negative charge that develops during the rate determining process of tetrahedral …
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The Influence of Oxyanions on the EDTA-Promoted Dissolution of Goethite
… silicate and oxide minerals. In natural systems oxyanions can compete with organic ligands for mineral surface sites thereby affecting ligand-promoted dissolution rates. Oxyanions can either enhance or inhibit dissolution depending upon pH. It has been suggested that the type of surface complex …
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Formation and transformation kinetics of iron oxy-hydroxides and effects of adsorbed oxyanions
… environmental contaminants and nutrients (e.g., oxyanions) through adsorption. Ferrihydrite is metastable and eventually transforms to hematite (Hm), goethite (Gt), and lepidocrocite (Lp). Although the Fh formation and transformation and oxyanion adsorption on its surface have been separately …
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Development of a sustainable water treatment technology for oxyanions using palladium-based catalysts: catalyst design, reaction mechanisms, and life cycle assessment
Perchlorate and nitrate are oxyanion contaminants found in many drinking water sources, causing human health risks when consumed even at low concentrations. These oxyanions are not removed via conventional drinking water treatment processes, and require specialized treatment. One emerging …
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Biochemical investigation of the ubiquitin carboxyl-terminal hydrolase family
… I will provide evidence that the putative oxyanion glutamine does function contribute to stabilization of the oxyanion intermediate. Secondly, I will show that evidence that glutamine may also serve another function within the active site by providing a CHO hydrogen bond that was previously …
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Mechanistic characterization of acetic acid resistance enzymes of Acetobacer aceti
… were used to examine the role of the internal oxyanion hole residue Asn347 and the highly conserved elements of the external oxyanion hole.</p> <p>First, a structure of the active mutant AarC-N347A bound to CoA revealed both solvent substitution for the deleted carboxamide and displacement of …
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A Specialized Citric Acid Cycle Requiring Succinyl-Coenzyme A (CoA):Acetate CoA-Transferase (AarC) Confers Acetic Acid Resistance on the Acidophile Acetobacter aceti
… CoA-transferases. Catalysis relies upon a novel oxyanion hole configuration composed partly of the distal amide nitrogen of CoA to stabilize tetrahedral oxyanion intermediates. Structural alignments suggest this mechanism is employed by all class I enzymes. Favorable hydrogen-bonding and …
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Surface complexation modeling of Pb(II), Cd(II) and Se(IV) onto iron hydroxides in single and bisolute systems
… two divalent metals, Cd(II) and Pb(II), and one oxyanion, Se(IV) onto α-FeOOH and ferrihydrite was modeled in single and bi-solute systems using the TLM. Selection of all surface complexes was supported by evidence from extended x-ray absorption fine structure spectroscopy. The fixed surface site …
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Discovery Of Inactive E* Conformations In Thrombin And Other Vitamin K- Dependent Clotting Proteases
… in the formation of a proper active site and oxyanion hole, both of which are required for efficient hydrolysis of peptide bonds. The transition from zymogen to active enzyme, E, thus provides critical temporal and spatial regulatory mechanism of protease function. Catalytic activity of serine …
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Solid-State 17O NMR as a New Probe to Study Acyl-Enzyme Intermediates
… from the protein backbone in the so-called oxyanion hole. This work represents the first use of solid-state 17O NMR spectroscopy to study acyl-enzyme intermediates and demonstrates the great potential of this new technique.
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Arsenic mobilization through bioreduction of iron oxide nanoparticles
… nanoparticles and was not released as a hydrated oxyanion, the arsenic-bearing nanoparticles could be readily mobilized in aquifers. These results have significant implications for understanding arsenic behavior in aquifers with Fe(III) reducing conditions, and may aid in improving remediation of …
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Synthesis, properties, and morphology of lignin based epoxy resins
… at room temperature, using KOH as oxyanion forming reagent. The epoxidized compounds were fractionated by solvent precipitation to remove poly(alkylene oxide) homopolymers and to prepare fractions of narrow molecular weight distributions. The epoxides were cross-linked with meta …
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Evaluation of Leachate Chemistry from Coal Refuse Blended and Layered with Fly Ash
… and a suite of elements with a focus on the oxyanions of As, Cr, Mo, and Se. A sequential extraction procedure revealed a significant portion of the elements in the residual fraction for the refuse/spoil substrates and in metal-oxide bound fractions for the ashes prior to leaching, and a …
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Enzymatic Characterization of N-Acetyl-1-D-myo-inosityl-2-amino-2-deoxy-alpha-D-glucopyranoside Deacetylase (MshB)
… and participates in catalysis by stabilizing the oxyanion intermediate. Molecular docking simulations suggest that the GlcNAc moiety on GlcNAc-Ins is stabilized by hydrogen bonding interactions with active site residues, while a hydrophobic stacking interaction between the inositol ring and Met98 …
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Development of oxorhenium complexes and bimetallic Re-Pd/C catalysts for perchlorate reduction in water
… metal to facilitate reduction of recalcitrant oxyanion contaminants.
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Small molecule activation and reduction using non-heme iron complexes
… of the enzymatic process. In Chapter 4, selenium oxyanion reduction by an iron(II) bis(triflate) complex was revisited. Previous work had shown that this iron system was capable of carrying out the stoichiometric reductions of selenite and selenite, resulting in an iron(III)-oxo species and …
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