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Full-Text Articles in Physics
Mutual Ionization In 200-Kev H⁻+ He Collisions, T. Ferger, Daniel Fischer, Michael Schulz, R. Moshammer, A. B. Voitkiv, B. Najjari, J. Ullrich
Mutual Ionization In 200-Kev H⁻+ He Collisions, T. Ferger, Daniel Fischer, Michael Schulz, R. Moshammer, A. B. Voitkiv, B. Najjari, J. Ullrich
Physics Faculty Research & Creative Works
We studied mutual ionization in 200-keV H-+He collisions in a kinematically complete experiment by measuring the fully momentum-analyzed recoil ions and both active electrons in coincidence. Comparison of the data to our calculations, based on various theoretical models, show that mutual ionization proceeds predominantly through the interaction between both electrons. The post-collision interaction between the outgoing ejected electrons as well as higher order processes involving the interaction between the core of both collision partners are also important.
Spectroscopic And Thermodynamic Characterization Of The E151d And E151a Altered Leucine Aminopeptidases From Aeromonas Proteolytica, Krzysztof P. Bzymek, Sabina I. Swierczek, Brian Bennett, Richard C. Holz
Spectroscopic And Thermodynamic Characterization Of The E151d And E151a Altered Leucine Aminopeptidases From Aeromonas Proteolytica, Krzysztof P. Bzymek, Sabina I. Swierczek, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
Previous kinetic characterization of the glutamate 151 (E151)-substituted forms of the leucine aminopeptidase from Aeromonas proteolytica (Vibrio proteolyticus; AAP) has provided critical evidence that this residue functions as the general acid/base. The close proximity of similar glutamate residues to the bridging water/hydroxide of the dinuclear active sites of metalloenzymes (2.80 and 3.94 Å in carboxypeptidase G2 and 3.30 and 3.63 Å in AAP), suggests it may also be involved in stabilizing the active-site metal ions. Therefore, the structural perturbations of the dinuclear active site of AAP were examined for two E151-substituted forms, namely E151D-AAP and E151A-AAP, by …
Kinetic, Spectroscopic, And X-Ray Crystallographic Characterization Of The Functional E151h Aminopeptidase From Aeromonas Proteolytica, Krzysztof P. Bzymek, Aaron Moulin, Sabina I. Swierczek, Dagmar Ringe, Gregory A. Petsko, Brian Bennett, Richard C. Holz
Kinetic, Spectroscopic, And X-Ray Crystallographic Characterization Of The Functional E151h Aminopeptidase From Aeromonas Proteolytica, Krzysztof P. Bzymek, Aaron Moulin, Sabina I. Swierczek, Dagmar Ringe, Gregory A. Petsko, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
Glutamate151 (E151) has been shown to be catalytically essential for the aminopeptidase from Vibrio proteolyticus (AAP). E151 acts as the general acid/base during the catalytic mechanism of peptide hydrolysis. However, a glutamate residue is not the only residue capable of functioning as a general acid/base during catalysis for dinuclear metallohydrolases. Recent crystallographic characterization of the d-aminopeptidase from Bacillus subtilis (DppA) revealed a histidine residue that resides in an identical position to E151 in AAP. Because the active-site ligands for DppA and AAP are identical, AAP has been used as a model enzyme to understand the mechanistic role of H115 in …
Complete Two-Loop Correction To The Bound-Electron Factor, Krzysztof Pachucki, Andrzej Czarnecki, Ulrich D. Jentschura, Vladimir A. Yerokhin
Complete Two-Loop Correction To The Bound-Electron Factor, Krzysztof Pachucki, Andrzej Czarnecki, Ulrich D. Jentschura, Vladimir A. Yerokhin
Physics Faculty Research & Creative Works
Within a systematic approach based on dimensionally regularized nonrelativistic quantum electrodynamics, we derive a complete result for the two-loop correction to order ( α/ π )2 ( Zα )4 for the g factor of an electron bound in an nS state of a hydrogenlike ion. The results obtained significantly improve the accuracy of the theoretical predictions for the hydrogenlike carbon and oxygen ions and influence the value of the electron mass inferred from g-factor measurements. D
Autoionization Of He Atoms By Partially Stripped Ion Impact, Sebastian Otranto, Ronald E. Olson
Autoionization Of He Atoms By Partially Stripped Ion Impact, Sebastian Otranto, Ronald E. Olson
Physics Faculty Research & Creative Works
A study of the autoionization process induced by partially stripped ion impact is performed. Electron spectra in momentum space are predicted within a classical model for partially stripped ions. The results are compared with those obtained for pure Coulomb-like projectiles. A quantum-mechanical extension of the Barrachina-Macek model is proposed for partially stripped projectiles. Structure on the electron angular distribution arising in quantum and classical treatments is identified and compared. The presence of rainbow scattering interference is observed in the binary ring profile of the outgoing autoionized electrons for positive-ion impact.
Spectroscopic Studies On Cobalt(Ii)-Substituted Metallo-Β-Lactamase Imis From Aeromonas Veronii Bv. Sobria, Patrick A. Crawford, Ke-Wu Yang, Narayan Sharma, Brian Bennett, Michael W. Crowder
Spectroscopic Studies On Cobalt(Ii)-Substituted Metallo-Β-Lactamase Imis From Aeromonas Veronii Bv. Sobria, Patrick A. Crawford, Ke-Wu Yang, Narayan Sharma, Brian Bennett, Michael W. Crowder
Physics Faculty Research and Publications
In an effort to probe the structure of a group Bb metallo-β-lactamase, Co(II)-substituted ImiS was prepared and characterized by electronic absorption, NMR, and EPR spectroscopies. ImiS containing 1 equiv of Co(II) (Co(II)1-ImiS) was shown to be catalytically active. Electronic absorption studies of Co(II)1-ImiS revealed the presence of two distinct features: (1) an intense sulfur to Co(II) ligand to metal charge transfer band and (2) less intense, Co(II) ligand field transitions that suggest 4-coordinate Co(II) in Co(II)1-ImiS. 1H NMR studies of Co(II)1-ImiS suggest that one histidine, one aspartic acid, and one cysteine …
Both Nucleophile And Substrate Bind To The Catalytic Fe(Ii)-Center In The Type-Ii Methionyl Aminopeptidase From Pyrococcus Furiosus, Alicja J. Copik, Sarah Waterson, Sabina I. Swierczek, Brian Bennett, Richard C. Holz
Both Nucleophile And Substrate Bind To The Catalytic Fe(Ii)-Center In The Type-Ii Methionyl Aminopeptidase From Pyrococcus Furiosus, Alicja J. Copik, Sarah Waterson, Sabina I. Swierczek, Brian Bennett, Richard C. Holz
Physics Faculty Research and Publications
Metalloproteases utilize their active site divalent metal ions to generate a nucleophilic water/hydroxide. For methionine aminopeptidases (MetAPs), the exact location of this nucleophile, as well as of the substrate, with respect to the active site metal ion is unknown. In order to address this issue, we have examined the catalytically competent Fe(II)-loaded form of PfMetAP-II ([Fe(PfMetAP-II)]) in the absence and presence of both nitric oxide (NO) and the substrate-analogue inhibitor butaneboronic acid (BuBA) by kinetic and spectroscopic (EPR, UV−vis) methods. NO binds to [Fe(PfMetAP−II)] with a Kd of 200 μM forming an {FeNO}7 …
Direct Evidence That The Reaction Intermediate Of Metallo-Β-Lactamase L1 Is Metal Bound, James D. Garrity, Brian Bennett, Michael W. Crowder
Direct Evidence That The Reaction Intermediate Of Metallo-Β-Lactamase L1 Is Metal Bound, James D. Garrity, Brian Bennett, Michael W. Crowder
Physics Faculty Research and Publications
In an effort to probe the structure of the reaction intermediate of metallo-β-lactamase L1 when reacted with nitrocefin and other β-lactams, time-dependent absorption and rapid-freeze-quench (RFQ) EPR spectra were obtained using the Co(II)-substituted form of the enzyme. When using nitrocefin as the substrate, time-dependent absorption spectra demonstrate that Co(II)-substituted L1 utilizes a reaction mechanism, similar to that of the native Zn(II) enzyme, in which a short-lived intermediate forms. RFQ-EPR spectra of this intermediate demonstrate that the binding of substrate results in a change in the electronic properties of one or both of the Co(II)'s in the enzyme …