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Articles 1 - 5 of 5
Full-Text Articles in Physical Sciences and Mathematics
Ph Dependent Reversible Formation Of A Binuclear Ni2 Metal-Center Within A Peptide Scaffold, Breena C. Keegan, Daniel Ocampo, Jason M. Shearer
Ph Dependent Reversible Formation Of A Binuclear Ni2 Metal-Center Within A Peptide Scaffold, Breena C. Keegan, Daniel Ocampo, Jason M. Shearer
Chemistry Faculty Research
A disulfide-bridged peptide containing two Ni2+ binding sites based on the nickel superoxide dismutase protein, {Ni2(SODmds)} has been prepared. At physiological pH (7.4), it was found that the metal sites are mononuclear with a square planar NOS2 coordination environment with the two sulfur-based ligands derived from cysteinate residues, the nitrogen ligand derived from the amide backbone, and a water ligand. Furthermore, S K-edge X-ray absorption spectroscopy indicated that the two cysteinate sulfur atoms ligated to nickel are each protonated. Elevation of the pH to 9.6 results in the deprotonation of the cysteinate sulfur atoms, …
On The Limited Role Of Electronic Support Effects In Selective Alkyne Hydrogenation: A Kinetic Study Of Au/MoX Catalysts Prepared From Oleylamine-Capped Colloidal Nanoparticles, James E. Bruno, K. B. Sravan Kumar, Nicolas S. Dwarica, Alexander Hüther, Zhifeng Chen, Clemente S. Guzman Iv, Emily R. Hand, William C. Moore, Robert M. Rioux, Lars C. Grabow, Bert D. Chandler
On The Limited Role Of Electronic Support Effects In Selective Alkyne Hydrogenation: A Kinetic Study Of Au/MoX Catalysts Prepared From Oleylamine-Capped Colloidal Nanoparticles, James E. Bruno, K. B. Sravan Kumar, Nicolas S. Dwarica, Alexander Hüther, Zhifeng Chen, Clemente S. Guzman Iv, Emily R. Hand, William C. Moore, Robert M. Rioux, Lars C. Grabow, Bert D. Chandler
Chemistry Faculty Research
We report a quantitative kinetic evaluation and study of support effects for partial alkyne hydrogenation using oleylaminecapped Au colloids as catalyst precursors. The amine capping agents can be removed under reducing conditions, generating supported Au nanoparticles of ~2.5 nm in diameter. The catalysts showed high alkene selectivity (>90%) at all conversions during alkyne partial hydrogenation. Catalytic activity, observed rate constants, and apparent activation energies (25– 40 kJ/mol) were similar for all Au catalysts, indicating support effects are relatively small. Alkyne adsorption, probed with FTIR and DFT, showed adsorption on the support was associated with hydrogen-bonding interactions. DFT calculations indicate …
Fluorogenic Atom Transfer Radical Polymerization In Aqueous Media As A Strategy For Detection, Zachary T. Allen, Jemima R. Sackey-Addo, Madeline P. Hopps, Danyal Tahseen, Joseph T. Anderson, Tyler A. Graf, Christina B. Cooley
Fluorogenic Atom Transfer Radical Polymerization In Aqueous Media As A Strategy For Detection, Zachary T. Allen, Jemima R. Sackey-Addo, Madeline P. Hopps, Danyal Tahseen, Joseph T. Anderson, Tyler A. Graf, Christina B. Cooley
Chemistry Faculty Research
The development of novel approaches to signal amplification in aqueous media could enable new diagnostic platforms for the detection of water-soluble analytes, including biomolecules. This paper describes a fluorogenic polymerization approach to amplify initiator signal by the detection of visible fluorescence upon polymerization in real-time. Fluorogenic monomers were synthesized and co-polymerized by atom transfer radical polymerization (ATRP) in water to reveal increasing polymer fluorescence as a function of both reaction time and initiator concentration. Optimization of the fluorogenic ATRP reaction conditions allowed for the quantitative detection of a small-molecule initiator as a model analyte over a broad linear concentration range …
A Biochemical Nickel(I) State Supports Nucleophilic Alkyl Addition: A Roadmap For Methyl Reactivity In Acetyl Coenzyme A Synthase, A. C. Manesis, B. W. Musselman, Breena C. Keegan, Jason M. Shearer, N. Lehnert, H. S. Shafaat
A Biochemical Nickel(I) State Supports Nucleophilic Alkyl Addition: A Roadmap For Methyl Reactivity In Acetyl Coenzyme A Synthase, A. C. Manesis, B. W. Musselman, Breena C. Keegan, Jason M. Shearer, N. Lehnert, H. S. Shafaat
Chemistry Faculty Research
Nickel-containing enzymes such as methyl coenzyme M reductase (MCR) and carbon monoxide dehydrogenase/acetyl coenzyme A synthase (CODH/ACS) play a critical role in global energy conversion reactions, with significant contributions to carbon-centered processes. These enzymes are implied to cycle through a series of nickel-based organometallic intermediates during catalysis, though identification of these intermediates remains challenging. In this work, we have developed and characterized a nickel-containing metalloprotein that models the methyl-bound organometallic intermediates proposed in the native enzymes. Using a nickel(I)-substituted azurin mutant, we demonstrate that alkyl binding occurs via nucleophilic addition of methyl iodide as a methyl donor. The paramagnetic Ni …
Reduction Of Co2 By A Masked Two-Coordinate Cobalt(I) Complex And Characterization Of A Proposed Oxodicobalt(Ii) Intermediate, L. Roy, M. H. Al-Afyouni, D. E. Derosha, B. Mondal, I. M. Dimucci, K. M. Lancaster, Jason M. Shearer, E. Bill, W. W. Brennessel, F. Neese, S. Ye, P. L. Holland
Reduction Of Co2 By A Masked Two-Coordinate Cobalt(I) Complex And Characterization Of A Proposed Oxodicobalt(Ii) Intermediate, L. Roy, M. H. Al-Afyouni, D. E. Derosha, B. Mondal, I. M. Dimucci, K. M. Lancaster, Jason M. Shearer, E. Bill, W. W. Brennessel, F. Neese, S. Ye, P. L. Holland
Chemistry Faculty Research
Fixation and chemical reduction of CO2 are important for utilization of this abundant resource, and understanding the detailed mechanism of C-O cleavage is needed for rational development of CO2 reduction methods. Here, we describe a detailed analysis of the mechanism of the reaction of a masked two-coordinate cobalt(i) complex, LtBuCo (where LtBu = 2,2,6,6-tetramethyl-3,5-bis[(2,6-diisopropylphenyl)imino]hept-4-yl), with CO2, which yields two products of C-O cleavage, the cobalt(i) monocarbonyl complex LtBuCo(CO) and the dicobalt(ii) carbonate complex (LtBuCo)2(μ-CO3). Kinetic studies and computations show that the …