Flip-flop dynamics in a model lipid bilayer membrane

The transition states associated to the dynamics of a model lipid bilayer membrane have been investigated by means of molecular-dynamics transition path sampling. We have focused on the flip-flop transition of a lipid molecule between the two sides of a flexible membrane. In the transition state, a local collective reorganization is necessary to allow a lipid molecule to move from one interface of the bilayer to the second one. The elapsed time for flip-flop has been estimated to be 0.27 ps, whereas the increase in configurational energy during the flip-flop transition is of about 15 kJ/mol.