While peripheral membrane protein-lipid interactions were originally considered to be solely electrostatic in nature, it is now accepted that they encompass more complicated, hydrophobic aspects. One such interaction involves the binding of the peripheral membrane protein, cytochrome c (cyt c) to phosphatidylserine (PS) on the inner side of the plasma membrane, shown to be a crucial step in programmed cell clearance. We have previously shown that unsaturated anionic lipids preferentially disrupt the folding structure of the cyt c. The aim of the study proposed is to utilise SANS to determine the effect of both the nature of the head group and the degree of unsaturation of the anionic phospholipid chain on the extent of binding of cyt c to vesicles.