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. Author manuscript; available in PMC: 2009 Aug 25.
Published in final edited form as: Biochemistry. 1998 May 19;37(20):7351–7362. doi: 10.1021/bi972864b

Figure 6.

Figure 6

Inversion recovery curves for semiquinone in the reduced N338A (upper) and Y501F/T525A (lower) samples of R. sphaeroides ETF-QO at 50 K. The samples were produced by reductive titration to the potentials that give the maximum SQ-· signal: N338A (-75 mV) and Y501F/T525A (-10 mV). The curves are the sums of contributions from semiquinone with neighboring diamagnetic [4Fe-4S]2+ and paramagnetic [4Fe-4S]+. The difference between the two curves reflects the impact of the paramagnetic [4Fe-4S]+: N338A (70-80%) and Y501F/T525A (0%). The dashed line is a simulated curve calculated with MENOSR. Simulated curves for both FAD site mutants give an average interspin distance of 17.6 ± 0.9 Å.