The Structure of a Lipid-cytochrome C Membrane

In the preceding paper a theory has been developed for the X-ray diffraction pattern from a lipid bilayer coated with protein molecules. In this paper the validity of the theory is tested. After adding cytochrome c to a preparation of lipid vesicles both vesicles and, in lesser amount, a multilayered structure are found. The expected cross-interference ripple is evident, and a computed profile shows the added protein at the surface of an unchanged lipid bilayer. The results confirm the structure proposed by others on the basis of rather indirect chemical and X-ray data. Protein coating a lipid bilayer is a possible structure for natural membranes. These results demonstrate that globular protein molecules can be detected at the surfaces of a lipid bilayer.