Accessibility parameters and immersion depths for R1 side chains in membrane-bound annexin XII at pH 4.0 and in the absence of Ca2+. (A) The accessibility parameters for O2 (circles) and NiEDDA (triangles) as a function of sequence. (B) The immersion depth in the bilayer of lipid-exposed R1 residues with maximal Φ values (residues 139, 143, 147, 151, 154, and 158).