The determination of the electron density profile of the human erythrocyte ghost membrane by small-angle x-ray diffraction.
Diffraction patterns of stacked hemolyzed erythrocyte ghosts in the wet state were recorded. Three orders of a surprisingly high first-order periodicity of 600 A were detected. The scattering curves were evaluated by the Q-function method, including lattice distortions of the one-dimensional multilamellar system. The resulting electron density profile of the membrane in the wet state is strongly asymmetric. It consists of an asymmetrical bilayer-type part and an excess of positive relative electron density at the inner, cytoplasmic, side of the membrane. The extension of the whole membrane profile in the wet state is 100--120 A. We suggest that the innermost positive density peak mainly represents the loosely bound protein components spectrin and actin, located at the cytoplasmic side of the membrane and sometimes seen as "fuzzy" material on electron micrographs.