Computer simulation of model membranes was used to evaluate the possib
le mechanism of lipid bilayer fusion. The simplified two dimensional m
odel of the membrane cross section was used as an analog of three dime
nsional reality. Lipid molecules were represented by rodlike structure
s, and forces between them were limited to attraction/repulsion intera
ctions described by a simple energy function with a minimum: 300-400 m
olecules were modeled in every simulation. Using the energy minimizati
on procedure, it was possible to obtain stable linear or circular bila
yer structures (two dimensional analogs of planar membranes and liposo
mes). In response to changes in attraction/repulsion equilibrium betwe
en molecules these bilayers were able to reorganize via cooperative pr
ocess. By increasing the headgroup attraction parameter for contacting
monolayers, it was possible to induce formation of a zone of hemifusi
on in the area of bilayer contact. The possible correlation between co
operative bilayer rearrangement in the model and in real bilayers is d
iscussed.