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Marquette University

Series

2010

Articles 1 - 10 of 10

Full-Text Articles in Physics

Low Temperature Photo-Oxidation Of Chloroperoxidase Compound Ii, Xinting Yuan, Xin Sheng, John A. Horner, Brian Bennett, Leslie W. -M. Fung, Martin Newcomb Nov 2010

Low Temperature Photo-Oxidation Of Chloroperoxidase Compound Ii, Xinting Yuan, Xin Sheng, John A. Horner, Brian Bennett, Leslie W. -M. Fung, Martin Newcomb

Physics Faculty Research and Publications

Oxidation of the heme-thiolate enzyme chloroperoxidase (CPO) from Caldariomyces fumago with peroxynitrite (PN) gave the Compound II intermediate, which was photo-oxidized with 365 nm light to give a reactive oxidizing species. Cryo-solvents at pH ≈ 6 were employed, and reactions were conducted at temperatures as low as − 50 °C. The activity of CPO as evaluated by the chlorodimedone assay was unaltered by treatment with PN or by production of the oxidizing transient and subsequent reaction with styrene. EPR spectra at 77 K gave the amount of ferric protein at each stage in the reaction sequence. The PN oxidation step …

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Improved Magnetic Domain-Wall Control With Transverse Fields, Andrew Kunz Sep 2010

Improved Magnetic Domain-Wall Control With Transverse Fields, Andrew Kunz

Physics Faculty Research and Publications

No abstract provided.

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Controlling Individual Domain Walls In Ferromagnetic Nanowires For Memory And Sensor Applications, Andrew Kunz, Sarah C. Reiff, Jonathan D. Priem, Eric W. Rentsch Sep 2010

Controlling Individual Domain Walls In Ferromagnetic Nanowires For Memory And Sensor Applications, Andrew Kunz, Sarah C. Reiff, Jonathan D. Priem, Eric W. Rentsch

Physics Faculty Research and Publications

Controlled motion of 180o and 360o domain walls along planar nanowires is presented. Standard Landau – Lifshitz micromagnetic modeling has been used to simulate the response of the domain walls to the application of an external magnetic field. A 180o wall is quickly and easily moved with the application of an applied. field along the axis of the wire but a 360odomain wall is stationary in the same case. An oscillatory applied field can be used to continually move the wall along the wires axis. The speed at which the 360o domain wall is found to be several times slower …

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Converting Glx2-1 Into An Active Glyoxalase Ii, Pattraranee Limphong, Nicole E. Adams, Matthew F. Rouhier, Ross M. Mckinney, Melissa Naylor, Brian Bennett, Christopher A. Makaroff, Michael W. Crowder Sep 2010

Converting Glx2-1 Into An Active Glyoxalase Ii, Pattraranee Limphong, Nicole E. Adams, Matthew F. Rouhier, Ross M. Mckinney, Melissa Naylor, Brian Bennett, Christopher A. Makaroff, Michael W. Crowder

Physics Faculty Research and Publications

Arabidopsis thaliana glyoxalase 2-1 (GLX2-1) exhibits extensive sequence similarity with GLX2 enzymes but is catalytically inactive with SLG, the GLX2 substrate. In an effort to identify residues essential for GLX2 activity, amino acid residues were altered at positions 219, 246, 248, 325, and 328 in GLX2-1 to be the same as those in catalytically active human GLX2. The resulting enzymes were overexpressed, purified, and characterized using metal analyses, fluorescence spectroscopy, and steady-state kinetics to evaluate how these residues affect metal binding, structure, and catalysis. The R246H/N248Y double mutant exhibited low level S-lactoylglutathione hydrolase activity, while the R246H/N248Y/Q325R/R328K mutant exhibited …

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Injecting, Controlling, And Storing Magnetic Domain Walls In Ferromagnetic Nanowires, Andrew Kunz, Jonathan D. Priem, Sarah C. Reiff Aug 2010

Injecting, Controlling, And Storing Magnetic Domain Walls In Ferromagnetic Nanowires, Andrew Kunz, Jonathan D. Priem, Sarah C. Reiff

Physics Faculty Research and Publications

Domain walls in ferromagnetic nanowires are important for proposed devices in recording, logic, and sensing. The realization of such devices depends in part on the ability to quickly and accurately control the domain wall from creation until placement. Using micromagnetic computer simulation we demonstrate how a combination of externally applied magnetic fields is used to quickly inject, move, and accurately place multiple domain walls within a single wire for potential recording and logical operations. The use of a magnetic field component applied perpendicular to the principle domain wall driving field is found to be critical for increased speed and reliability. …

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Dynamic Notch Pinning Fields For Domain Walls In Ferromagnetic Nanowires, Andrew Kunz, Jonathan D. Priem Jun 2010

Dynamic Notch Pinning Fields For Domain Walls In Ferromagnetic Nanowires, Andrew Kunz, Jonathan D. Priem

Physics Faculty Research and Publications

Artificial defects such as notches and antinotches are often attached to magnetic nanowires to serve as trapping (pinning) sites for domain walls. The magnetic field necessary to release (depin) the trapped domain wall from the notch depends on the type, geometric shape, and dimensions of the defect but is typically quite large. Conversely we show here that for some notches and antinotches there exists a much smaller driving field for which a moving domain wall will travel past the defect without becoming trapped. This dynamic pinning field also depends on the type, geometric shape and defect dimensions. Micromagnetic simulation is …

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Simulations Of Field Driven Domain Wall Interactions In Ferromagnetic Nanowires, Andrew Kunz, Eric W. Rentsch Jun 2010

Simulations Of Field Driven Domain Wall Interactions In Ferromagnetic Nanowires, Andrew Kunz, Eric W. Rentsch

Physics Faculty Research and Publications

The interaction of domain walls in a single ferromagnetic nanowire has been observed with micromagnetic simulation. Domain walls separating domains of opposite magnetization move towards each other when an external field is applied along the long axis of the wire resulting in a collision. The final magnetic state of the wire after the collision will contain either zero (domain wall annihilation) or two (domain wall conservation) domain walls. Here we explore the behavior that determines the final state, showing that it depends on the initial domain wall configuration, the speed the domain walls are moving with before the collision, and …

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Magnetic Response Versus Lift Height Of Thin Ferromagnetic Films, Tanner Schulz, Gabe Burch, Andrew Kunz, E. Dan Dahlberg Jun 2010

Magnetic Response Versus Lift Height Of Thin Ferromagnetic Films, Tanner Schulz, Gabe Burch, Andrew Kunz, E. Dan Dahlberg

Physics Faculty Research and Publications

The interaction between a magnetic force microscope (MFM) tip and ferromagnetic films of Ni, Co90Fe10 and Py with in-plane magnetization has been investigated. The measured interaction, due to the magnetizing of the films by the MFM tip field, was determined by the phase shift of the cantilever response. The tip-film separation or lift height dependent phase shift was found to be independent of the saturation magnetization of the ferromagnetic film. The result is identical for all three films and micromagnetic simulations give similar results. The reason is at a given tip-sample separation the tip induced magnetization of …

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Chemical Switching Behaviour Of Tricarbonylrhenium(I) Complexes Of A New Redox Active ‘Pincer’ Ligand, Sarath Wanniarachchi, Brendan J Liddle, John Toussaint, Sergey Lindeman, Brian Bennett, James R. Gardinier Apr 2010

Chemical Switching Behaviour Of Tricarbonylrhenium(I) Complexes Of A New Redox Active ‘Pincer’ Ligand, Sarath Wanniarachchi, Brendan J Liddle, John Toussaint, Sergey Lindeman, Brian Bennett, James R. Gardinier

Physics Faculty Research and Publications

The structures and optoelectronic properties of tricarbonylrhenium(I) complexes of di(2-pyrazolyl-p-tolyl)amine in its neutral and deprotonated (uninegative amido) form were investigated. Reactions of the complexes with Brønsted acids or bases result in distinctive changes of colour and electrochemical activity owing to the non-innocent nature of the ligand.

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The Metal Ion Requirements Of Arabidopsis Thaliana Glx2-2 For Catalytic Activity, Pattraranee Limphong, Ross M. Mckinney, Nicole E. Adams, Christopher A. Makaroff, Brian Bennett, Michael W. Crowder Feb 2010

The Metal Ion Requirements Of Arabidopsis Thaliana Glx2-2 For Catalytic Activity, Pattraranee Limphong, Ross M. Mckinney, Nicole E. Adams, Christopher A. Makaroff, Brian Bennett, Michael W. Crowder

Physics Faculty Research and Publications

In an effort to better understand the structure, metal content, the nature of the metal centers, and enzyme activity of Arabidopsis thaliana Glx2-2, the enzyme was overexpressed, purified, and characterized using metal analyses, kinetics, and UV–vis, EPR, and 1H NMR spectroscopies. Glx2-2-containing fractions that were purple, yellow, or colorless were separated during purification, and the differently colored fractions were found to contain different amounts of Fe and Zn(II). Spectroscopic analyses of the discrete fractions provided evidence for Fe(II), Fe(III), Fe(III)–Zn(II), and antiferromagnetically coupled Fe(II)–Fe(III) centers distributed among the discrete Glx2-2-containing fractions. The individual steady-state kinetic constants varied among the …

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