Pathway of membrane fusion with two tension-dependent energy barriers.

Fusion of bilayer membranes is studied via dissipative particle dynamics (DPD) simulations. A new set of DPD parameters is introduced which leads to an energy barrier for flips of lipid molecules between adhering membranes. A large number of fusion events is monitored for a vesicle in contact with a planar membrane. Several time scales of the fusion process are found to depend exponentially on the membrane tension. This implies an energy barrier of about 10k(B)T for intermembrane flips and a second size-dependent barrier for the nucleation of a small hemifused membrane patch.