Fig. 5.

Relative changes in EPR linewidth of nitroxides 1 and 3 in the mouse brain. Nitroxide 2 or 4 was injected into mice (i.v., 0.4 mmol/kg body weight; n = 5 for each nitroxide). EPR spectra were acquired as mice inhaled different concentrations of O₂ (0, 10, 21 and 95% balance is N₂). Solid lines are least-squares fit of the function, y = (ax + b)/(x + b), to the data. The O₂ concentration required for 50% saturation of the response, [O₂]_1/2, is indicated for each curve.