Analysis of substrate positioning in NapI by HYSCORE spectroscopy on its
EPR-active, S = 3/2 iron-nitrosyl
{FeNO}7
complex. A, Comparison of HYSCORE spectra (left)
and simulations (right), collected at 330 mT on samples of
NapI•{FeNO}7•2OG•5,5-d2-L-Arg
(top) and NapI•{FeNO}7•2OG•4,4-d2-L-Arg
(bottom). Spectra were collected with a microwave frequency of 9.77 GHz at a
temperature of 4.0 K. Experimental conditions and simulation parameters are
given in the legends to Figures S10 and S11. B, Comparison of
distances obtained by x-ray crystallography (black) and HYSCORE
spectroscopy (red), and structural models based on these
distances. The transparent C3–C5 segment is based on the HYSCORE
results. Hydrogens are shown as purple spheres.