Lipid peroxidation is an important part of the pathological pathway of membrane damage in membranes that have high levels of polyunsaturated fatty acids such as linoleic, linolenic, arachidonic, and docosahexaenoic acids. Neural membranes are particularly rich in polyunsaturated acids and such damage is implicated in neurological diseases, such as Alzheimer's disease. To obtain a bilayer model that represents the property of susceptibility to lipid peroxidation, we carried out molecular dynamics (MD) simulations of a bilayer of 1-palmitoyl-2-linoleyl-sn-glycero-3-phosphatidylcholine (PLPC). Parameters for the torsional potentials of the cis,cis-Delta(9,12) bis-allylic region of the linoleate chain were fitted to the results of high-level ab initio calculations on model compounds. The MD simulations of the bilayer provided the structural properties of the system and show that the unsaturation induces disorder and affects the physical properties of the membrane.