Extended data Figure 8. EPR saturation.

EPR saturation behavior of the MfR2 radical at 103 and 298 K. Saturation curves at different temperatures determine the microwave power at half saturation P_1/2. The temperature dependence of P_1/2 gives information about possible relaxing transition metals in the vicinity of the radical. A fast relaxing metal site will give a higher P_1/2 than for an isolated radical. The microwave saturation behavior of the MfR2 is similar to that for an hv-irradiated tyrosine solution. Here we evaluate P_1/2 ≈ 0.6 mW at 103 K and P_1/2 ≈ 30 mW at 298 K for MfR2. This can be compared to hν Tyr• with P_1/2 ≈ 0.4mW at 93 K and E. coli Tyr• with P_1/2 ≈ 150 mW at 106 K and not possible to saturate at 298K.