Conventional (9 GHz, 40 K) and high frequency (285 GHz, 4 K; Inset) EPR spectra of the Trp• formed in the CiP triple variant and in the E250Q+E168Q variant of LiP. The 9-GHz EPR spectrum of the Trp is dominated by partially resolved proton hyperfine couplings (Table S1), whereas at higher frequencies, the g values (gx = 2.0035, gy = 2.0027, and gz = 2.0022) were accurately resolved.