A dissipative particle dynamics model is applied to probe the lipidic membrane fusion. This model is verified by reproducing the lipid phase behavior. The classical stalk model has been visited and modified. The tilt deformation of the lipids and the noncircular shape of the stalk are supported. The stalk is shown to undergo asymmetric expansion to form the trans-monolayers contact (TMC). Unlike previous models, an energy barrier between the stalk and the TMC has been identified, implying that the TMC should be a metastable formation. This shows good agreement with the fusion experiments. Two typical elastic continuum models are compared with our result and possible modifications to the two elastic models are suggested. The effect of spontaneous curvature of lipid on selection of fusion pathway is also examined. It is observed that a bent stalk with pore or an inverted micellar intermediate will have more chance to occur than traditional stalk when the spontaneous curvature of the lipid becomes more negative.
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