Transfer of the Slip Plane in Lipid Bilayer Lubrication

Lipid bilayers are commonly found in articular cartilage and cell membranes, playing a key role in biological lubrication, which is attributed to the hydration lubrication mechanism of the headgroups. In physiological environments, lipid bilayers inevitably interact with ions, but their exact effect on lubrication is currently unclear. Here, through molecular dynamics simulations, we discover an ion-induced slip plane transfer behavior. Ions weaken the hydration lubrication effect at the headgroup-headgroup interface between bilayers, forcing the slip plane to partially shift to the acyl tail-tail interface within the bilayer and increasing friction. However, the above behavior is not observed under high hydration levels. Extensive comparison and analysis show that the transfer of the slip plane is determined by the lubrication state of two types of interfaces, with sliding always occurring at the interface with a lower dissipation at the current moment. This maximizes lubrication efficiency while providing lubrication assurance, even under high load, low hydration, and ion influence, maintaining a good lubrication performance. Our results provide valuable insights into the efficient and robust lubrication of lipid bilayers.