X ray diffraction studies of human erythrocyte membrane structure

Abstract

Small angle x ray diffraction patterns were obtained from ordered arrays of hemoglobin free human erythrocyte membranes by use of improved techniques. Diffraction data were recorded to 9 Å resolution on samples whose lattice periodicity was varied (by changing humidity) from 55.5 Å to 69.6 Å. The observed reflections permitted reflections the intensity transform of the membranes. Phases for the rflections were assigned by the minimum wavelength principle. An electron density profile was then obtained by Fourier inversion, and yielded a symmetric membrane about 55 Å in width. This structure can account for the previously reported diffuse scattering observed in other preparations (thus rendering unnecessary the proposed assignment of this scattering to a separated lipoprotein phase) and for the continuous scattering that was recorded from isolated membranes in buffer. Lower resolution data that were obtained from ultracentrifugally prepared lattices in buffer (and therefore without dehydration) are consistent with the present results, and support the view that one is observing diffraction from intact membranes.