FORCES BETWEEN PHOSPHOLIPID-BILAYERS AND RELATIONSHIP TO MEMBRANE-FUSION

The adhesion and fusion of model membranes—that is, surfactant and lipid bilayers of known composition, can be quite complex because they interact with each other through a number of different forces. Various models of fusion have been suggested, mainly based on electron micrographs of small vesicles or membranes. The principal problems of conventional freeze-fracture electron microscopy (and rapid freezing techniques in general) are the rapidity of the fusion process and the very small area over which it occurs. It is very difficult to trap or freeze the various stages of fusion as the whole process appears to be over within 0.1–l msec. Thus, the precise molecular rearrangements accompanying the fusion process are still unknown. The chapter explains how the surface forces apparatus technique can be used for measuring interbilayer forces while monitoring the deformations of fusing bilayers supported on solid surfaces. The technique allows following the molecular rearrangements in real time during the fusion process and highlights the most important forces involved. © 1993, Elsevier Inc. All rights reserved.