Coarse-grained description of monounsaturated peroxidized phospholipid bilayers

Lipid peroxides result from a reaction between cis-unsaturated lipid chains and singlet oxygen molecules leading to the addition of a peroxide OOH side group next to the acyl-chain double bond. It is now established that HP-POPC (hydroperoxidized POPC) molecules form stable, thin, and laterally expanded bilayers. The difference in the structural organization arises from the hydrophilic character of the OOH side group that has a strong affinity with the water interface region, leading to significant reorganization of the bilayer. In this article, we describe a coarse-grained (CG) model of POPC and DOPC lipid peroxides within the framework of the Martini CG force-field (v2.2), derived from experimental data. We then discuss extensively the predicted structure and the influence of hydration and show how shifting the position of the unsaturated bonds along the chain changes the structure. Finally, we provide electron and neutron scattering length density profiles of the simulated bilayers.