Low temperature EPR spectra as a function of storage time after purification. A, KatG[S315G]; B, wild-type KatG; C, KatG[S315T] (from Ref. 43). Experimental conditions were as follows: temperature, 4 K; microwave power, 1 milliwatt; modulation amplitude, 4 G; frequency, 9.38 GHz. g-value assignments are as follows: for r2, g1 = 6.04, g2 = 5.54, and g3 ∼ 2.00; for r1, g1 = 6.30, g2 = 5.1, and g3 ∼ 2; for r3, g1 = 6.68, g2 = 5.1, and g3 ∼ 2 was present in each case.