A Model of Coagulation Kinetics Between two Deformable Bilayers. Application to the Membrane Fusion

Starting from the classical DLVO theory describing the interaction between adjacent charged objects imbedded in an electrolyte solution, we developed a model to calculate the coagulation kinetics for large deformable bodies. We considered two flexible lamellae (e.g. lipid bilayers) interacting with each other through a double well potential. We postulated that a possible mechanism to overcome the energy barrier between the two minima requires a local deformation leading to the formation of adhering patches stabilized by short-range forces (Dispersion forces or bridged bonds formed by divalent ions) but hampered by the lamellae deformation work. These patches can either grow or re-dissolve in a fashion similar to the classical mechanism of nucleation theory. When the locally adhering zone reaches a critical diameter, its size rapidly grows causing the complete adhesion of the lamellae (transition from the secondary to the primary minimum). bining the DLVO, ion binding and elasticity theories within the conceptual framework of the Transition State approximation, we derived a model to simulate fluctuation-induced coagulation kinetics. The model requires the knowledge of some parameters such as the bending elastic constant and the energy difference between the primary and secondary minima. A comparison with the classical DLVO results for rigid bodies and with experimental data on fusion kinetics of lipid vesicles is discussed.