High-resolution iron X-ray absorption spectroscopic and computational studies of non-heme diiron peroxo intermediates

George E. Cutsail, Elizabeth J. Blaesi, Christopher J. Pollock, J. Martin Bollinger, Carsten Krebs, Serena DeBeer

Research output: Contribution to journalArticle

Abstract

Ferritin-like carboxylate-bridged non-heme diiron enzymes activate O2 for a variety of difficult reactions throughout nature. These reactions often begin by abstraction of hydrogen from strong C[sbnd]H bonds. The enzymes activate O2 at their diferrous cofactors to form canonical diferric peroxo intermediates, with a range of possible coordination modes. Herein, we explore the ability of high-energy resolution fluorescence detected X-ray absorption spectroscopy (HERFD XAS) to provide insight into the nature of peroxo level intermediates in non-heme diiron proteins. Freeze quenched (FQ) peroxo intermediates from p-aminobenzoate N-oxygenase (AurF), aldehyde-deformylating oxygenase (ADO), and the β subunit of class Ia ribonucleotide reductase from Escherichia coli (Ecβ) are investigated. All three intermediates are proposed to adopt different peroxo binding modes, and each exhibit different Fe Kα HERFD XAS pre-edge features and intensities. As these FQ-trapped samples consist of multiple species, deconvolution of HERFD XAS spectra based on speciation, as determined by Mössbauer spectroscopy, is also necessitated - yielding ‘pure’ diferric peroxo HERFD XAS spectra from dilute protein samples. Finally, the impact of a given peroxo coordination mode on the HERFD XAS pre-edge energy and intensity is evaluated through time-dependent density functional theory (TDDFT) calculations of the XAS spectra on a series of hypothetical model complexes, which span a full range of possible peroxo coordination modes to a diferric core. The utility of HERFD XAS for future studies of enzymatic intermediates is discussed.

Original languageEnglish (US)
Article number110877
JournalJournal of Inorganic Biochemistry
Volume203
DOIs
StatePublished - Feb 2020

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X-Ray Absorption Spectroscopy
X ray absorption spectroscopy
X ray absorption
Iron
Fluorescence
X-Rays
Oxygenases
para-Aminobenzoates
Ribonucleotide Reductases
Deconvolution
Enzymes
Ferritins
Aldehydes
Escherichia coli
Density functional theory
Hydrogen
Spectrum Analysis
Proteins
Spectroscopy

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Inorganic Chemistry

Cite this

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title = "High-resolution iron X-ray absorption spectroscopic and computational studies of non-heme diiron peroxo intermediates",
abstract = "Ferritin-like carboxylate-bridged non-heme diiron enzymes activate O2 for a variety of difficult reactions throughout nature. These reactions often begin by abstraction of hydrogen from strong C[sbnd]H bonds. The enzymes activate O2 at their diferrous cofactors to form canonical diferric peroxo intermediates, with a range of possible coordination modes. Herein, we explore the ability of high-energy resolution fluorescence detected X-ray absorption spectroscopy (HERFD XAS) to provide insight into the nature of peroxo level intermediates in non-heme diiron proteins. Freeze quenched (FQ) peroxo intermediates from p-aminobenzoate N-oxygenase (AurF), aldehyde-deformylating oxygenase (ADO), and the β subunit of class Ia ribonucleotide reductase from Escherichia coli (Ecβ) are investigated. All three intermediates are proposed to adopt different peroxo binding modes, and each exhibit different Fe Kα HERFD XAS pre-edge features and intensities. As these FQ-trapped samples consist of multiple species, deconvolution of HERFD XAS spectra based on speciation, as determined by M{\"o}ssbauer spectroscopy, is also necessitated - yielding ‘pure’ diferric peroxo HERFD XAS spectra from dilute protein samples. Finally, the impact of a given peroxo coordination mode on the HERFD XAS pre-edge energy and intensity is evaluated through time-dependent density functional theory (TDDFT) calculations of the XAS spectra on a series of hypothetical model complexes, which span a full range of possible peroxo coordination modes to a diferric core. The utility of HERFD XAS for future studies of enzymatic intermediates is discussed.",
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High-resolution iron X-ray absorption spectroscopic and computational studies of non-heme diiron peroxo intermediates. / Cutsail, George E.; Blaesi, Elizabeth J.; Pollock, Christopher J.; Bollinger, J. Martin; Krebs, Carsten; DeBeer, Serena.

In: Journal of Inorganic Biochemistry, Vol. 203, 110877, 02.2020.

Research output: Contribution to journalArticle

TY - JOUR

T1 - High-resolution iron X-ray absorption spectroscopic and computational studies of non-heme diiron peroxo intermediates

AU - Cutsail, George E.

AU - Blaesi, Elizabeth J.

AU - Pollock, Christopher J.

AU - Bollinger, J. Martin

AU - Krebs, Carsten

AU - DeBeer, Serena

PY - 2020/2

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