Distribution of the iron-heme displacement as resulting from myoglobin conformational substrates: an AOM approach to the interpretation of the EPR spectra.
The electron paramagnetic resonance (EPR) low-temperature spectra of high spin ferric myoglobin samples in different solvent composition have been analyzed in terms of a distribution of the energy differences delta 1 and delta 2 for the iron low-lying electronic states. The widths of these distributions, which are found to be dependent on the solvent composition, have been correlated to the presence of a frozen ensemble of conformational substrates. A dedicated analysis based on the angular overlap method (AOM) has allowed us to work out a quantitative relationship between the delta 1 and delta 2 distributions and the spread of the iron-heme displacement; this being a structural parameter relevant for the biological functionality of the protein. The observed dependence of the iron-heme displacement distribution on the solvent composition is discussed.
Dipartimento di Fisica dell'Università, Perugia, Italy.
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Bizzarri
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M
Bacci
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Cannistraro
D000818:Animals; D004578:Electron Spin Resonance Spectroscopy; D006418:Heme / Q000737:chemistry*; D006736:Horses; D007501:Iron / Q000737:chemistry*; D009211:Myoglobin / Q000737:chemistry*; D011487:Protein Conformation
D009211:Myoglobin; D006418:Heme; D007501:Iron