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. Author manuscript; available in PMC: 2020 Dec 31.
Published in final edited form as: Biochemistry. 2019 May 15;58(52):5305–5319. doi: 10.1021/acs.biochem.9b00292

Figure 2.

Figure 2.

EPR spectra of S5HH. (A) As-isolated (mononuclear iron reduced, Rieske cluster oxidized) S5HH (470 μM). (B) S5HH (470 μM) stoichiometrically reduced with sodium dithionite and methyl viologen (40 μM). The * indicates a small overlapping derivative signal from reduced methyl viologen, indicating full reduction of S5HH. (C) In a single-turnover reaction, reduced S5HH (470 μM) with salicylate (7.96 mM) was reacted with oxygen (720 μM) in standard buffer at 4 °C and frozen after 30 s (concentrations after mixing). Instrument conditions: microwave power, 200 μW; modulation amplitude, 10 G; microwave frequency, 9.64 GHz; temperature, the g = 4.3 and g = 9.68 signals were detected at 2 K (black) and the Rieske cluster signal (g = 2.01, 1.91, 1.45) was detected at 20 K (red).