EPR spectra of the N694C: A) Ferric form, 0.1 M Borate, pH 9.2; B) Simulation with 80 ± 8% rhombic and 20 ± 2% axial; Experimental parameters for all spectra: Concentration = 50 μM FeIII, Temperature = 4 K, field set = 4000 G, scan range = 8 kG, time const. = 82 ms, mod. amplitude = 8 G, microwave power = 615 μW, freq. = 9.44 GHz, gain = 60.