X-band EPR spectra of an anaerobic solution of 300 μM Td FDPred in buffer (black trace) and of the same sample after the addition of 0.5 eq NO, incubation of the mixture for ~5 min at room temperature, and then freezing in liquid N2 (red trace). Spectral collection parameters were: temperature 4 K, modulation frequency 100 kHz, microwave power 21 mW, modulation amplitude 10.5 G, conversion time 81.9 ms, time constant 5.1 ms