Lipids form the major component of cell membranes, which separate the contents of the cell from the external environment. The oxidation of lipids within biological membranes is implicated in a range of diseases and health effects including cancer and ageing. In this proposal we wish to examine how oxidation of specific lipids changes the structure of lipid membranes. Specifically we prepare lipid monolayers at the air-water interface containing different amounts of deuterium labeled oxidized lipids. Neutron reflection, combined with different contrasts, will be used to interrogate the lipid layers and determine the orientation and positioning of the oxidized lipids within the layer. The results will provide an enhanced understanding of how oxidative damages changes the properties of cell membranes.