Disturb or stabilize? A molecular dynamics study of the effects of resorcinolic lipids on phospholipid bilayers

Resorcinolic lipids, or resorcinols, are commonly found in plant membranes. They consist of a substituted benzene ring forming the hydrophilic lipid head, attached to an alkyl chain forming the hydrophobic tail. Experimental results show alternative effects of resorcinols on lipid membranes. Depending on whether they are added to lipid solutions before or after the formation of the liposomes, they either stabilize or destabilize these liposomes. Here we use atomistic molecular dynamics simulations to elucidate the molecular nature of this dual effect. Systems composed of either one of three resorcinol homologs, differing in the alkyl tail length, interacting with dimyristoylphosphatidylcholine lipid bilayers were studied. It is shown that resorcinols preincorporated into bilayers induce order within the lipid acyl chains, decrease the hydration of the lipid headgroups, and make the bilayers less permeable to water. In contrast, simulations in which the resorcinols are incorporated from the aqueous solution into a preformed phospholipid bilayer induce local disruption, leading to either transient pore formation or even complete rupture of the membrane. In line with the experimental data, our simulations thus demonstrate that resorcinols can either disturb or stabilize the membrane structure, and offer a detailed view of the underlying molecular mechanism