As research on apoptosis has gained momentum, the importance of membrane lipids in this crucial cellular process is becoming clear.Previously, we have determined using NR and surface sensitive techniques that the apoptotic protein, cytochrome c (cyt c), binds both differently and to different extents to membranes containing different anionic phospholipids.However interpretation of the data has been impeded due to charge effects of the Si surface on protein binding.The objective of the proposed work is to use the new floating supported bilayer (FSB) system recently developed at ISIS, to provide a model membrane which is more like a natural membrane and is, most importantly, free from charge effects of the substrate.The neutron reflection studies will be complimented by previously done neutron studies and will allow us to establish the location of cyt c in membranes with anionic lipids.