Molecular dynamics simulations of water wires in a lipid bilayer and water/octane model systems

A series of classical molecular dynamics simulations of a water wire in a DPPC bilayer yielded lifetimes τ of up to 90 ps, with τ̄=37±8 ps (not including a significant fraction wires that broke during equilibration). This is sufficiently long to conduct protons across the bilayer through a quantum mechanical hopping mechanism, similar to proton conduction in ice. Lifetimes of wires in the octane region of a water/octane/water “sandwich” were qualitatively similar (τ̄=36±3 ps) though wires were rarely lost during equilibration. Hence, the utility of the water/octane system as a membrane surrogate depends on the application.