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 (t1/2≈ 1 s at pH 7.4, 37 degrees 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 × 10-4cm· 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.