Fast two dimensional computer simulation of bilayer hemifusion

Computer simulation of model membranes was used to evaluate the possible mechanism of lipid bilayer fusion. The simplified two dimensional model of the membrane cross section was used as an analog of three dimensional reality. Lipid molecules were represented by rodlike structures, and forces between them were limited to attraction/repulsion interactions described by a simple energy function with a minimum: 300-400 molecules were modeled in every simulation. Using the energy minimization procedure, it was possible to obtain stable linear or circular bilayer structures (two dimensional analogs of planar membranes and liposomes). In response to changes in attraction/repulsion equilibrium between molecules these bilayers were able to reorganize via cooperative process. By increasing the headgroup attraction parameter for contacting monolayers, it was possible to induce formation of a zone of hemifusion in the area of bilayer contact. The possible correlation between cooperative bilayer rearrangement in the model and in real bilayers is discussed.