X-Ray Diffraction Analysis of Membrane Structure Changes with Oxidative Stress

Lipid peroxidation alters membrane structure-function relationships by disrupting chemical bonds associated with phospholipid acyl chains (1 ). Fluorescence polarization techniques have been used previously to demonstrate changes in membrane fluidity, one of the consequences of peroxidative modification (2 ). However, these previous studies do not provide direct insights into the molecular structure of the lipid bilayer. Small-angle X-ray diffraction is one technique that has been used successfully to measure the effects of oxidative stress on the molecular parameters of the membrane lipid bilayer. Molecules in the “liquid-crystalline” membrane bilayer have an amphipathic chemical structure consisting of a hydrophilic headgroup that associates with the water phase and hydrophobic acyl chains that interact strongly with neighboring acyl chains. As a result of this biomolecular orientation, the membrane is highly amenable to X-ray diffraction analysis, especially when layered or stacked in a periodic fashion. In this article, we review the protocol for the use of X-ray diffraction analysis to directly characterize structural changes associated with oxidative modification. The results of these analyses provide important insights into mechanisms of cellular injury and death associated with free radical damage at the biomembrane level.