X-RAY-DIFFRACTION EVIDENCE FOR THE PRESENCE OF DISCRETE WATER LAYERS ON THE SURFACE OF MEMBRANES

X-ray diffraction spacings in multilayered membranes obtained from frog sciatic nerves were found to increase in discrete steps of approx. 5 angstrom during swelling. These observed jumps in the repeat period suggest that the lipid bilayers exist in distinct states of hydration, and perhaps the swelling occurs by step-wise addition of water layers between the polar head groups. Our analysis and statistical tests of this hypothesis are presented.