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. Author manuscript; available in PMC: 2014 Jan 4.
Published in final edited form as: Nature. 2013 Jun 26;499(7456):66–69. doi: 10.1038/nature12239

Figure 3. Continuous wave and pulsed EPR spectra on 1-HydF.

Figure 3

a: X-band EPR spectra recorded at 10K for dithionite-reduced 1-HydF (black line) and HydF (dashed line) in 50 mM Tris-HCl buffer, 150 mM NaCl, 5 mM DT, pH 8. Microwave power = 100 μW, mod. amp. = 1 mT, mwfreq. = 9.39 GHz. The shoulder observed at g = 1.90 in the 1-HydF spectrum, corresponding to a few percent of the total signal intensity, is assigned to a small fraction of HydF lacking 1. b: X-band 2D pulsed ESEEM spectroscopy (CF-NF) of 1-HydF labelled with 13CN– (left) and unlabelled 1-HydF (right). The horizontal ridge seen at (ν2 = 2·ν13C = 7.7 MHz) is attributed to a hyperfine interaction between a 13C nucleus and the paramagnetic [4Fe-4S] cluster. Its extension yields the magnitude of the coupling (Δν1 = 4.1 MHz = a13C). This feature is absent from the unlabelled 1-HydF spectrum.