The separation of particular lipids in cell membranes into liquid ordered and liquid disorder regions is thought to have a major influence of the functioning of membrane proteins. In this proposal we will examine changes to the ordering of lipids following oxidation events. Small angle neutron scattering will be used in combination with contrast variation as a non-invasive method to detect changes to the size of the lipid rafts (microdomains) as lipid vesicles are oxidized in situ. The vesicles will be prepared from a ternary mixture of lipids known to form rafts at low temperatures but not high temperatures, DPPC:DOPC:chol in ratios of 2:2:1 and 1:1:1.