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Low-frequency EPR of ferrimyoglobin fluoride and ferrimyoglobin cyanide

a case study on the applicability of broadband analysis to high-spin hemoproteins and to HALS hemoproteins

Journal Article (2022)
Author(s)

Wilfred R. Hagen (TU Delft - BT/Biocatalysis)

Research Group
BT/Biocatalysis
Copyright
© 2022 W.R. Hagen
DOI related publication
https://doi.org/10.1007/s00775-022-01948-1
More Info
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Publication Year
2022
Language
English
Copyright
© 2022 W.R. Hagen
Research Group
BT/Biocatalysis
Issue number
4-5
Volume number
27
Pages (from-to)
497-507
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Abstract

An EPR spectrometer has been developed that can be tuned to many frequencies in the range of ca 0.1–15 GHz. Applicability has been tested on ferrimyoglobin fluoride (MbF) and ferrimyoglobin cyanide (MbCN). MbF has a high-spin (S = 5/2) spectrum with 19F superhyperfine splitting that is only resolved in X-band along the heme normal. Low-frequency EPR also resolves the splitting in the heme plane. Measurement of linewidth as a function of frequency provides the basis for an analysis of inhomogeneous broadening in terms of g-strain, zero-field distribution, unresolved superhyperfine splittings and dipolar interaction. Rhombicity in the g tensor is found to be absent. MbCN (S = 1/2) has a highly anisotropic low spin (HALS) spectrum for which gx cannot be determined unequivocally in X-band. Low-frequency EPR allows for measurement of the complete spectrum and determination of the g-tensor. Graphical abstract: [Figure not available: see fulltext.]