X-ray diffraction patterns from haemoglobin-free erythrocyte membranes

Abstract

IN a survey¹ of X-ray diffraction patterns from erythrocyte membrane preparations produced by hypotonic lysis within a range of tonicities and pH, we emphasised the lability of the haemoglobin-free membrane preparation which readily degenerated during dehydration to give both lipid and residual membrane (lipoprotein) phases. The lipid was identified with a diffraction periodicity of 5–5.5 nm which was sensitive to temperature changes and which could be eliminated by treatment of the membranes with phospholipase C before dehydration². In electron micrographs of sections prepared from the same samples the lipid phase was identified with regions of very fine layering (4 nm periodicity) scattered irregularly through a mass of closely packed layering of much greater dimension, which undoubtedly represented the condensed erythrocyte ghosts. These closely packed ghosts provided periodicities of 20–30 nm, each period including two apposed thicknesses of membrane which were clearly asymmetrical. The corresponding X-ray diffraction patterns also revealed this higher periodicity. We have since experimented with various conditions which can be used to provide haemoglobin-free membranes and have obtained much-improved X-ray diffraction data which confirm and extend our earlier conclusions.