Fig. 3.

Mössbauer spectra of MauG recorded at 4.2 K in a 53-mT magnetic field. (a) The spectrum of ferric MauG (hashed marks) is overlaid with spin Hamiltonian simulations of a high-spin Fe(III) heme (25% of total Fe, dashed line) and of a low-spin Fe(III) heme (75% of total Fe, solid line) with the following parameters: S = 5/2, g_5/2 = 2, D_5/2 = 10 cm⁻¹ (E/D)_5/2 = 0, δ = 0.50 mm/s, ΔE_Q = 2.0 mm/s, η = 0, A/g_Nβ_N = (−18.0, −18.0, −18.0) T and S = 1/2, g_1/2 = (1.87, 2.19, 2.54), δ = 0.25 mm/s, ΔE_Q = 1.97 mm/s, η = −3, A/g_Nβ_N = (−36.2, +9.3, +30.0) T. (b) Spectrum of di-ferric MauG, which was reacted with H₂O₂ for 45 s (hashed marks). The solid line indicates the contribution of ferric MauG (≈34% of total Fe). Removal of these features yields the reference spectrum of the intermediates (c, in which the x axis scale has been expanded), which can be simulated with two quadrupole doublets: δ₁ = 0.06 mm/s and ΔE_Q1 = 1.70 mm/s (15%, dashed line) and δ₂ = 0.17 mm/s and ΔE_Q2 = 2.54 mm/s (35%, solid line).