(A) EPR spectra of as-isolated M-L1 recorded at 5.6 K, 63 mW (filled line), 12 K, 63 mW (dotted line) and 12 K, 10 mW (dashed line). Various regions of the spectrum are shown to highlight the different behaviors as a function of temperature and microwave power. (B) EPR spectrum of as-isolated L1, ‘FeZn-L1’ (dotted line, 12 K, 10 mW), and that of L1 refolded in the presence of iron, ‘Fe-L1’ (filled line; 10 mW, 10 K).