Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Keyword
-
- Domain walls (2)
- Ions (2)
- Magnetic moments (2)
- Metals (2)
- Nanowires (2)
-
- Peptides and proteins (2)
- ATP binding cassette transporter (1)
- Critical fields (1)
- EPR (1)
- EPR spectroscopy (1)
- ETHE1 (1)
- Fe(II) (1)
- Genetics (1)
- Isotope effects (1)
- Kinetics (1)
- Magnetic fields (1)
- Mechanism (1)
- Methionine aminopeptidases (1)
- Mutants (1)
- NMR spectroscopy (1)
- Polarization (1)
- Rotating flows (1)
- Transition metals (1)
- Zinc binding (1)
- Zinc-specific uptake system (1)
- ZnuA (1)
- Β-Lactamase fold (1)
Articles 1 - 11 of 11
Full-Text Articles in Physics
Analyzing The Catalytic Role Of Asp97 In The Methionine Aminopeptidase From Escherichia Coli, Sanghamitra Mitra, Kathleen M. Job, Lu Meng, Brian Bennett, Richard C. Holz
Analyzing The Catalytic Role Of Asp97 In The Methionine Aminopeptidase From Escherichia Coli, Sanghamitra Mitra, Kathleen M. Job, Lu Meng, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
An active site aspartate residue, Asp97, in the methionine aminopeptidase (MetAPs) from Escherichia coli (EcMetAP-I) was mutated to alanine, glutamate, and asparagine. Asp97 is the lone carboxylate residue bound to the crystallographically determined second metal-binding site in EcMetAP-I. These mutant EcMetAP-I enzymes have been kinetically and spectroscopically characterized. Inductively coupled plasma–atomic emission spectroscopy analysis revealed that 1.0 ± 0.1 equivalents of cobalt were associated with each of the Asp97-mutated EcMetAP-Is. The effect on activity after altering Asp97 to alanine, glutamate or asparagine is, in general, due to a ∼ 9000-fold decrease in kca towards …
Kinetic And Spectroscopic Analysis Of The Catalytic Role Of H79 In The Methionine Aminopeptidase From Escherichia Coli, Sarah J. Watterson, Sanghamitra Mitra, Sabina I. Swierczek, Brian Bennett, Richard C. Holz
Kinetic And Spectroscopic Analysis Of The Catalytic Role Of H79 In The Methionine Aminopeptidase From Escherichia Coli, Sarah J. Watterson, Sanghamitra Mitra, Sabina I. Swierczek, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
To gain insight into the role of the strictly conserved histidine residue, H79, in the reaction mechanism of the methionyl aminopeptidase from Escherichia coli (EcMetAP-I), the H79A mutated enzyme was prepared. Co(II)-loaded H79A exhibits an overall >7000-fold decrease in specific activity. The almost complete loss of activity is primarily due to a >6000-fold decrease in kcat. Interestingly, the Km value obtained for Co(II)-loaded H79A was approximately half the value observed for wild-type (WT) EcMetAP-I. Consequently, kcat/Km values decreased only 3000-fold. On the other hand, the observed specific activity of Mn(II)-loaded …
Trapping And Characterization Of A Reaction Intermediate In Carbapenem Hydrolysis By B. Cereus Metallo-Β-Lactamase, Mariana F. Tioni, Leticia L. Llarrull, Andrés A. Poeylaut-Palena, Marcelo A. Martí, Miguel Saggu, Gopal R. Periyannan, Ernesto G. Mata, Brian Bennett, Daniel H. Murgida, Alejandro J. Vila
Trapping And Characterization Of A Reaction Intermediate In Carbapenem Hydrolysis By B. Cereus Metallo-Β-Lactamase, Mariana F. Tioni, Leticia L. Llarrull, Andrés A. Poeylaut-Palena, Marcelo A. Martí, Miguel Saggu, Gopal R. Periyannan, Ernesto G. Mata, Brian Bennett, Daniel H. Murgida, Alejandro J. Vila
Physics Faculty Research and Publications
Metallo-β-lactamases hydrolyze most β-lactam antibiotics. The lack of a successful inhibitor for them is related to the previous failure to characterize a reaction intermediate with a clinically useful substrate. Stopped-flow experiments together with rapid freeze−quench EPR and Raman spectroscopies were used to characterize the reaction of Co(II)−BcII with imipenem. These studies show that Co(II)−BcII is able to hydrolyze imipenem in both the mono- and dinuclear forms. In contrast to the situation met for penicillin, the species that accumulates during turnover is an enzyme−intermediate adduct in which the β-lactam bond has already been cleaved. This intermediate is a metal-bound anionic species …
First-Row Transition-Metal Complexes Of A New Pentadentate Ligand, Α,Α,Α′,Α′-Tetra(Pyrazolyl)Lutidine, Tyler James Morin, Brian Bennett, Sergey V. Lindeman, James R. Gardinier
First-Row Transition-Metal Complexes Of A New Pentadentate Ligand, Α,Α,Α′,Α′-Tetra(Pyrazolyl)Lutidine, Tyler James Morin, Brian Bennett, Sergey V. Lindeman, James R. Gardinier
Physics Faculty Research and Publications
A new pentadentate ligand, α,α,α′,α′-tetra(pyrazolyl)lutidine, pz4lut, has been prepared by a CoCl2-catalyzed rearrangement reaction between 2,6-pyridinedicarboxaldehyde and dipyrazolylthione. The coordination chemistry with some divalent first-row transition metal (Mn, Fe, Co, Ni, Cu, and Zn) chlorides has been explored. The electronic properties indicate that the new κ5N ligand is a slightly stronger-field donor to Ni2+ and Co2+ than a related pentadentate ligand with five pyridyl donors presumably because of greater interaction between the metal and axial pyridyl.
Spectroscopic Studies On Arabidopsis Ethe1, A Glyoxalase Ii-Like Protein, Meghan M. Holdorf, Brian Bennett, Michael W. Crowder, Christopher A. Makaroff
Spectroscopic Studies On Arabidopsis Ethe1, A Glyoxalase Ii-Like Protein, Meghan M. Holdorf, Brian Bennett, Michael W. Crowder, Christopher A. Makaroff
Physics Faculty Research and Publications
ETHE1 (ethylmalonic encephalopathy protein 1) is a β-lactamase fold-containing protein that is essential for the survival of a range of organisms. In spite of the apparent importance of this enzyme, very little is known about its function or biochemical properties. In this study Arabidopsis ETHE1 was over-expressed and purified and shown to bind tightly to 1.2 ± 0.2 equivalents of iron. 1H NMR and EPR studies demonstrate that the predominant oxidation state of Fe in ETHE1 is Fe(II), and NMR studies confirm that two histidines are bound to Fe(II). EPR studies show that there is no antiferromagnetically coupled Fe(III)Fe(II) …
Metal Content Of Metallo-Β-Lactamase L1 Is Determined By The Bioavailability Of Metal Ions, Zhenxin Hu, Thusitha S. Gunasekera, Lauren J. Spadafora, Brian Bennett, Michael W. Crowder
Metal Content Of Metallo-Β-Lactamase L1 Is Determined By The Bioavailability Of Metal Ions, Zhenxin Hu, Thusitha S. Gunasekera, Lauren J. Spadafora, Brian Bennett, Michael W. Crowder
Physics Faculty Research and Publications
In an effort to probe whether the metal content of metallo-β-lactamase L1 is affected by metal ion bioavailability, L1 was overexpressed as mature protein (M-L1) and full-length (FL-L1) analogues, and the analogues were characterized with metal analyses, kinetics, and EPR spectroscopy. FL-L1, containing the putative leader sequence, was localized in the periplasm of Escherichia coli and shown to bind Zn(II) preferentially. The metal content of FL-L1 could be altered if the enzyme was overexpressed in minimal medium containing Fe and Mn, and surprisingly, an Fe-binding analogue was obtained. On the other hand, M-L1, lacking the putative leader sequence, was localized …
Conformational Changes In The Metallo-Β-Lactamase Imis During The Catalytic Reaction: An Epr Spectrokinetic Study Of Co(Ii)-Spin Label Interactions, Narayan Sharma, Zhenxin Hu, Michael W. Crowder, Brian Bennett
Conformational Changes In The Metallo-Β-Lactamase Imis During The Catalytic Reaction: An Epr Spectrokinetic Study Of Co(Ii)-Spin Label Interactions, Narayan Sharma, Zhenxin Hu, Michael W. Crowder, Brian Bennett
Physics Faculty Research and Publications
Metallo-β-lactamases are responsible for conferring antibiotic resistance on certain pathogenic bacteria. In consequence, the search for inhibitors that may be useful in combating antibiotic resistance has fueled much study of the active sites of these enzymes. There exists circumstantial evidence that the binding of substrates and inhibitors to metallo-β-lactamases may involve binding to the organic part of the molecule, in addition to or prior to binding to one or more active site metal ions. It has also been postulated that a conformational change may accompany this putative binding. In the present study, electron paramagnetic resonance spectrokinetic study of a spin-labeled …
MoV Electron Paramagnetic Resonance Of Sulfite Oxidase Revisited: The Low-Ph Chloride Signal, Christian J. Donnan, Heather L. Wilson, Brian Bennett, Roger C. Prince, K. V. Rajagopalan, Graham N. George
MoV Electron Paramagnetic Resonance Of Sulfite Oxidase Revisited: The Low-Ph Chloride Signal, Christian J. Donnan, Heather L. Wilson, Brian Bennett, Roger C. Prince, K. V. Rajagopalan, Graham N. George
Physics Faculty Research and Publications
Valuable information on the active sites of molybdenum enzymes has been provided by MoV electron paramagnetic resonance (EPR) spectroscopy. In recent years, multiple resonance techniques have been extensively used to examine details of the active-site structure, but basic continuous-wave (CW) EPR has not been re-evaluated in several decades. Here, we present a re-examination of the CW EPR spectroscopy of the sulfite oxidase low-pH chloride species and provide evidence for direct coordination of molybdenum by chloride.
Structure And Metal Binding Properties Of Znua, A Periplasmic Zinc Transporter From Escherichia Coli, Liliya A. Yatsunyk, J. Allen Easton, Lydia R. Kim, Stacy A. Sugarbaker, Brian Bennett, Robert M. Breece, Ivan I. Vorontsov, David L. Tierney, Michael W. Crowder, Amy C. Rosenzweig
Structure And Metal Binding Properties Of Znua, A Periplasmic Zinc Transporter From Escherichia Coli, Liliya A. Yatsunyk, J. Allen Easton, Lydia R. Kim, Stacy A. Sugarbaker, Brian Bennett, Robert M. Breece, Ivan I. Vorontsov, David L. Tierney, Michael W. Crowder, Amy C. Rosenzweig
Physics Faculty Research and Publications
ZnuA is the periplasmic Zn2+-binding protein associated with the high-affinity ATP-binding cassette ZnuABC transporter from Escherichia coli. Although several structures of ZnuA and its homologs have been determined, details regarding metal ion stoichiometry, affinity, and specificity as well as the mechanism of metal uptake and transfer remain unclear. The crystal structures of E. coli ZnuA (Eco-ZnuA) in the apo, Zn2+-bound, and Co2+-bound forms have been determined. ZnZnuA binds at least two metal ions. The first, observed previously in other structures, is coordinated tetrahedrally by Glu59, His60, His143, and His207. Replacement of Zn2+ …
Fast Domain Wall Motion In Nanostripes With Out-Of-Plane Fields, Andrew Kunz, Sarah C. Reiff
Fast Domain Wall Motion In Nanostripes With Out-Of-Plane Fields, Andrew Kunz, Sarah C. Reiff
Physics Faculty Research and Publications
Controlling domain wall motion is important due to the impact on the viability of proposed nanowire devices. One hurdle is slow domain wall speed when driven by fields greater than the Walker field due to nucleation of vortices in the wall. We present simulation results detailing the dynamics of these vortices including the nucleation and subsequent fast ejection of the vortex core leading to fast domain wall speeds. The ejection is due to the reversal of the core moments by an out-of-plane field. The technique can be used to produce domain walls of known orientation, independent of the initial state.
Enhancing Domain Wall Speed In Nanowires With Transverse Magnetic Fields, Andrew Kunz, Sarah C. Reiff
Enhancing Domain Wall Speed In Nanowires With Transverse Magnetic Fields, Andrew Kunz, Sarah C. Reiff
Physics Faculty Research and Publications
Dynamic micromagnetic simulation studies have been completed to observe the motion of a domain wall in a magnetic nanowire in an effort to increase the field-driven domain wall speed. Previous studies have shown that the wire dimensions place a cap on the maximum speed attainable by a domain wall when driven by a magnetic field placed along the direction of the nanowire. Here we present data showing a significant increase in the maximum speed of a domain wall due to the addition of a magnetic field placed perpendicular to the longitudinal driving field. The results are expressed in terms of …