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Physical Sciences and Mathematics Commons™

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Physics

Marquette University

Series

2014

Articles 1 - 5 of 5

Full-Text Articles in Physical Sciences and Mathematics

Dilution Of Dipolar Interactions In A Spin-Labeled, Multimeric Metalloenzyme For Deer Studies, Mahesh Aitha, Timothy K. Richmond, Zhenxin Hu, Alyssa Hetrick, Raquel Reese, Althea Gunther, Robert Mccarrick, Brian Bennett, Michael W. Crowder Jul 2014

Dilution Of Dipolar Interactions In A Spin-Labeled, Multimeric Metalloenzyme For Deer Studies, Mahesh Aitha, Timothy K. Richmond, Zhenxin Hu, Alyssa Hetrick, Raquel Reese, Althea Gunther, Robert Mccarrick, Brian Bennett, Michael W. Crowder

Physics Faculty Research and Publications

The metallo-β-lactamases (MβLs), which require one or two Zn(II) ions in their active sites for activity, hydrolyze the amide bond in β-lactam-containing antibiotics, and render the antibiotics inactive. All known MβLs contain a mobile element near their active sites, and these mobile elements have been implicated in the catalytic mechanisms of these enzymes. However little is known about the dynamics of these elements. In this study, we prepared a site-specific, double spin-labeled analog of homotetrameric MβL L1 with spin labels at positions 163 and 286 and analyzed the sample with DEER (double electron electron resonance) spectroscopy. Four unique distances were …

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A Deep Chandra Acis Survey Of M83, Knox S. Long, Kip D. Kuntz, William P. Blair, Leith Godfrey, Paul P. Plucinsky, Roberto Soria, Christopher Stockdale, P. Frank Winkler Jun 2014

A Deep Chandra Acis Survey Of M83, Knox S. Long, Kip D. Kuntz, William P. Blair, Leith Godfrey, Paul P. Plucinsky, Roberto Soria, Christopher Stockdale, P. Frank Winkler

Physics Faculty Research and Publications

We have obtained a series of deep X-ray images of the nearby galaxy M83 using Chandra, with a total exposure of 729 ks. Combining the new data with earlier archival observations totaling 61 ks, we find 378 point sources within the D25 contour of the galaxy. We find 80 more sources, mostly background active galactic nuclei (AGNs), outside of the D25 contour. Of the X-ray sources, 47 have been detected in a new radio survey of M83 obtained using the Australia Telescope Compact Array. Of the X-ray sources, at least 87 seem likely to be supernova remnants …

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Shewanella Oneidensis Cytochrome C Nitrite Reductase (Ccnir) Does Not Disproportionate Hydroxylamine To Ammonia And Nitrite, Despite A Strongly Favorable Driving Force, Matthew Youngblut, Daniel J. Pauly, Natalia Stein, Daniel Walters, John A. Conrad, Graham R. Moran, Brian Bennett, A. Andrew Pacheco Apr 2014

Shewanella Oneidensis Cytochrome C Nitrite Reductase (Ccnir) Does Not Disproportionate Hydroxylamine To Ammonia And Nitrite, Despite A Strongly Favorable Driving Force, Matthew Youngblut, Daniel J. Pauly, Natalia Stein, Daniel Walters, John A. Conrad, Graham R. Moran, Brian Bennett, A. Andrew Pacheco

Physics Faculty Research and Publications

Cytochrome c nitrite reductase (ccNiR) from Shewanella oneidensis, which catalyzes the six-electron reduction of nitrite to ammonia in vivo, was shown to oxidize hydroxylamine in the presence of large quantities of this substrate, yielding nitrite as the sole free nitrogenous product. UV–visible stopped-flow and rapid-freeze-quench electron paramagnetic resonance data, along with product analysis, showed that the equilibrium between hydroxylamine and nitrite is fairly rapidly established in the presence of high initial concentrations of hydroxylamine, despite said equilibrium lying far to the left. By contrast, reduction of hydroxylamine to ammonia did not occur, even though disproportionation of hydroxylamine to …

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Electron Cooling In A Young Radio Supernova: Sn 2012aw, Naveen Yadav, Alak Ray, Christopher Stockdale, Poonam Chandrasiri, Randall Smith, Rupak Roy, Vikram Dwarkadas, Firoza Sutaria, David Pooley Feb 2014

Electron Cooling In A Young Radio Supernova: Sn 2012aw, Naveen Yadav, Alak Ray, Christopher Stockdale, Poonam Chandrasiri, Randall Smith, Rupak Roy, Vikram Dwarkadas, Firoza Sutaria, David Pooley

Physics Faculty Research and Publications

We present the radio observations and modeling of an optically bright Type II-P supernova (SN), SN 2012aw which exploded in the nearby galaxy Messier 95 (M95) at a distance of 10 Mpc. The spectral index values calculated using C, X, and K bands are smaller than the expected values for the optically thin regime. During this time, the optical bolometric light curve stays in the plateau phase. We interpret the low spectral-index values to be a result of electron cooling. On the basis of comparison between the Compton cooling timescale and the synchrotron cooling timescale, we find that …

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Homoleptic Nickel(Ii) Complexes Of Redox-Tunable Pincer-Type Ligands, Jeewantha S. Hewage, Sarath Wanniarachchi, Tyler James Morin, Brendan J Liddle, Megan Banaszynski, Sergey V. Lindeman, Brian Bennett, James R. Gardinier Jan 2014

Homoleptic Nickel(Ii) Complexes Of Redox-Tunable Pincer-Type Ligands, Jeewantha S. Hewage, Sarath Wanniarachchi, Tyler James Morin, Brendan J Liddle, Megan Banaszynski, Sergey V. Lindeman, Brian Bennett, James R. Gardinier

Physics Faculty Research and Publications

Different synthetic methods have been developed to prepare eight new redox-active pincer-type ligands, H(X,Y), that have pyrazol-1-yl flanking donors attached to an ortho-position of each ring of a diarylamine anchor and that have different groups, X and Y, at the para-aryl positions. Together with four previously known H(X,Y) ligands, a series of 12 Ni(X,Y)2 complexes were prepared in high yields by a simple one-pot reaction. Six of the 12 derivatives were characterized by single-crystal X-ray diffraction, which showed tetragonally distorted hexacoordinate nickel(II) centers. The nickel(II) complexes exhibit two quasi-reversible one-electron oxidation waves in their cyclic voltammograms, with …

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