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EPR Spectroscopy: Applications for Metal Sites in Biological Systems—William E. Antholine at 75

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Molecular Biophysics".

Deadline for manuscript submissions: closed (31 May 2019) | Viewed by 14906

Special Issue Editors

Department of Biophysics, Medical College of Wisconsin, 8701 W Watertown Plank Road, Milwaukee, WI 53226, USA
Interests: multi-frequency EPR (electron paramagnetic resonance) of metal complexes; cupric sites; metal complexes of antitumor agents; chromate
Department of Physics, Marquette University, 540 North 15th Street, Milwaukee, WI 53233, USA
Interests: EPR; ENDOR; Co; Cu; nitrile reductase; mitochondrial dysfunction

Special Issue Information

Dear Colleagues,

In my role as the “metal person” at the National Biomedical EPR Center at the Medical College of Wisconsin, I have collaborated with outstanding scientists, nationally and internationally, for more than 40 years. These collaborations have resulted in more than 200 publications of research articles and chapters. As I turned 75 years old, it occurred to me that I would like to publish several of my latest research studies and the research of others, both well known to me and unknown to me, in a Special Issue. The main requirement is that there is at least one EPR spectrum in each article. While I am best known for publications using low frequency EPR of cupric sites including sites in prions, antitumor agents, cytochrome, c oxidase, nitrous oxide reductase, and particulate methane monooxygenase, I intend to submit articles with cobalt and chromium EPR spectra. I encourage authors to submit papers on their main interests and also new interests.

Dr. William E. Antholine
Guest Editor

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Keywords

  • EPR, electron paramagnetic resonance
  • Metal complexes
  • Enzymes
  • Diseases
  • Mitochondrial dysfunction

Published Papers (5 papers)

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9 pages, 1115 KiB  
Article
Spectroscopic Characterisation of the Naphthalene Dioxygenase from Rhodococcus sp. Strain NCIMB12038
by Maria Camilla Baratto, David A. Lipscomb, Michael J. Larkin, Riccardo Basosi, Christopher C. R. Allen and Rebecca Pogni
Int. J. Mol. Sci. 2019, 20(14), 3402; https://doi.org/10.3390/ijms20143402 - 11 Jul 2019
Cited by 5 | Viewed by 2660
Abstract
Polycyclic aromatic hydrocarbons (PAHs), such as naphthalene, are potential health risks due to their carcinogenic and mutagenic effects. Bacteria from the genus Rhodococcus are able to metabolise a wide variety of pollutants such as alkanes, aromatic compounds and halogenated hydrocarbons. A naphthalene dioxygenase [...] Read more.
Polycyclic aromatic hydrocarbons (PAHs), such as naphthalene, are potential health risks due to their carcinogenic and mutagenic effects. Bacteria from the genus Rhodococcus are able to metabolise a wide variety of pollutants such as alkanes, aromatic compounds and halogenated hydrocarbons. A naphthalene dioxygenase from Rhodococcus sp. strain NCIMB12038 has been characterised for the first time, using electron paramagnetic resonance (EPR) spectroscopy and UV-Vis spectrophotometry. In the native state, the EPR spectrum of naphthalene 1,2-dioxygenase (NDO) is formed of the mononuclear high spin Fe(III) state contribution and the oxidised Rieske cluster is not visible as EPR-silent. In the presence of the reducing agent dithionite a signal derived from the reduction of the [2Fe-2S] unit is visible. The oxidation of the reduced NDO in the presence of O2-saturated naphthalene increased the intensity of the mononuclear contribution. A study of the “peroxide shunt”, an alternative mechanism for the oxidation of substrate in the presence of H2O2, showed catalysis via the oxidation of mononuclear centre while the Rieske-type cluster is not involved in the process. Therefore, the ability of these enzymes to degrade recalcitrant aromatic compounds makes them suitable for bioremediative applications and synthetic purposes. Full article
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10 pages, 2887 KiB  
Article
Resolved Hyperfine at L-band for High-Spin CoEDTA, A Model for Co Sites in Proteins
by William E. Antholine
Int. J. Mol. Sci. 2019, 20(10), 2385; https://doi.org/10.3390/ijms20102385 - 14 May 2019
Cited by 4 | Viewed by 2158
Abstract
Low-frequency electron paramagnetic resonance (EPR) spectra were obtained for the Co complex of ethylene diamine tetraacetic acid (CoEDTA). It was found that the cobalt hyperfine at geff-mid is better resolved at a low frequency, L-band (1.37 GHz), and not resolved at [...] Read more.
Low-frequency electron paramagnetic resonance (EPR) spectra were obtained for the Co complex of ethylene diamine tetraacetic acid (CoEDTA). It was found that the cobalt hyperfine at geff-mid is better resolved at a low frequency, L-band (1.37 GHz), and not resolved at X-band (9.631 GHz), which is the conventional frequency used for most spectra for metal complexes. Resolved cobalt hyperfine lines lead to additional EPR parameters like A-mid for cobalt and a more-accurate determination of g-mid. Resolved hyperfine lines in the L-band, but not the S-band, spectra were obtained at a concentration of 1 mM. Knowing these additional EPR parameters provides a means to better determine the electron density in the ground state orbital for each cobalt complex, as well as to determine differences upon a change of ligation. If zinc sites can be replaced by cobalt, the cobalt spectra for these sites will enhance the characterization of the zinc sites. Full article
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16 pages, 2001 KiB  
Article
Treatment of Cells and Tissues with Chromate Maximizes Mitochondrial 2Fe2S EPR Signals
by William E. Antholine, Jeannette Vasquez-Vivar, Brendan J. Quirk, Harry T. Whelan, Pui Kei Wu, Jong-In Park and Charles R. Myers
Int. J. Mol. Sci. 2019, 20(5), 1143; https://doi.org/10.3390/ijms20051143 - 06 Mar 2019
Cited by 5 | Viewed by 3365
Abstract
In a previous study on chromate toxicity, an increase in the 2Fe2S electron paramagnetic resonance (EPR) signal from mitochondria was found upon addition of chromate to human bronchial epithelial cells and bovine airway tissue ex vivo. This study was undertaken to show that [...] Read more.
In a previous study on chromate toxicity, an increase in the 2Fe2S electron paramagnetic resonance (EPR) signal from mitochondria was found upon addition of chromate to human bronchial epithelial cells and bovine airway tissue ex vivo. This study was undertaken to show that a chromate-induced increase in the 2Fe2S EPR signal is a general phenomenon that can be used as a low-temperature EPR method to determine the maximum concentration of 2Fe2S centers in mitochondria. First, the low-temperature EPR method to determine the concentration of 2Fe2S clusters in cells and tissues is fully developed for other cells and tissues. The EPR signal for the 2Fe2S clusters N1b in Complex I and/or S1 in Complex II and the 2Fe2S cluster in xanthine oxidoreductase in rat liver tissue do not change in intensity because these clusters are already reduced; however, the EPR signals for N2, the terminal cluster in Complex I, and N4, the cluster preceding the terminal cluster, decrease upon adding chromate. More surprising to us, the EPR signals for N3, the cluster preceding the 2Fe2S cluster in Complex I, also decrease upon adding chromate. Moreover, this method is used to obtain the concentration of the 2Fe2S clusters in white blood cells where the 2Fe2S signal is mostly oxidized before treatment with chromate and becomes reduced and EPR detectable after treatment with chromate. The increase of the g = 1.94 2Fe2S EPR signal upon the addition of chromate can thus be used to obtain the relative steady-state concentration of the 2Fe2S clusters and steady-state concentration of Complex I and/or Complex II in mitochondria. Full article
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7 pages, 1071 KiB  
Communication
Better Resolution of High-Spin Cobalt Hyperfine at Low Frequency: Co-Doped Ba(Zn1/3Ta2/3)O3 as a Model Complex
by William E. Antholine, Shengke Zhang, Justin Gonzales and Nathan Newman
Int. J. Mol. Sci. 2018, 19(11), 3532; https://doi.org/10.3390/ijms19113532 - 09 Nov 2018
Cited by 4 | Viewed by 3832
Abstract
Low-frequency electron paramagnetic resonance (EPR) is used to extract the EPR parameter A-mid and support the approximate X-band value of g-mid for Ba(CoyZn1/3−yTa2/3)O3. Although the cobalt hyperfine structure for the |±1/2⟩ state is [...] Read more.
Low-frequency electron paramagnetic resonance (EPR) is used to extract the EPR parameter A-mid and support the approximate X-band value of g-mid for Ba(CoyZn1/3−yTa2/3)O3. Although the cobalt hyperfine structure for the |±1/2⟩ state is often unresolved at X-band or S-band, it is resolved in measurements on this compound. This allows for detailed analysis of the molecular orbital for the |±1/2⟩ state, which is often the ground state. Moreover, this work shows that the EPR parameters for Co substituted into Zn compounds give important insight into the properties of zinc binding sites. Full article
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8 pages, 7781 KiB  
Opinion
Concentration of Fe(3+)-Triapine in BEAS-2B Cells
by William E. Antholine and Charles R. Myers
Int. J. Mol. Sci. 2019, 20(12), 3062; https://doi.org/10.3390/ijms20123062 - 22 Jun 2019
Cited by 1 | Viewed by 2329
Abstract
An electron paramagnetic resonance (EPR) method was used to determine the concentration of the antitumor agent Triapine in BEAS-2B cells when Triapine was bound to iron (Fe). Knowledge of the concentration of Fe-Triapine in tumor cells may be useful to adjust the administration [...] Read more.
An electron paramagnetic resonance (EPR) method was used to determine the concentration of the antitumor agent Triapine in BEAS-2B cells when Triapine was bound to iron (Fe). Knowledge of the concentration of Fe-Triapine in tumor cells may be useful to adjust the administration of the drug or to adjust iron uptake in tumor cells. An EPR spectrum is obtained for Fe(3+)-Triapine, Fe(3+)(Tp)2+, in BEAS-2B cells after addition of Fe(3+)(Tp)2+. Detection of the low spin signal for Fe(3+)(Tp)2+ shows that the Fe(3+)(Tp)2+ complex is intact in these cells. It is proposed that Triapine acquires iron from transferrin in cells including tumor cells. Here, it is shown that iron from purified Fe-transferrin is transferred to Triapine after the addition of ascorbate. To our knowledge, this is the first time that the EPR method has been used to determine the concentration of an iron antitumor agent in cells. Full article
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