Peroxynitrite rapidly permeates phospholipid membranes

Peroxynitrite (ONOO(−)) is a potent oxidant implicated in a number of pathophysiological processes. The activity of ONOO(−) is related to its accessibility to biological targets before its spontaneous decomposition (t(1/2) ≈ 1 s at pH 7.4, 37°C). Using model phospholipid vesicular systems and manganese porphyrins as reporter molecules, we demonstrated that ONOO(−) freely crosses phospholipid membranes. The calculated permeability coefficient for ONOO(−) is ≈8.0 × 10(−4) cm⋅s(−1), which compares well with that of water and is ≈400 times greater than that of superoxide. We suggest that ONOO(−) is a significant biological effector molecule not only because of its reactivity but also because of its high diffusibility.