Onset of Percolation and Fractal Classification Scheme for Multilamellar Lipid Vesicles

Percolation, like phase transition, expresses a critical property of an assembly. The paper provides a brief description of the onset of percolation and the fractal behavior of clusters formed as a result of spontaneous assembly of multilamellar lipid vesicles (MLVs). The onset of percolation was studied using a series of mixed lipid systems. The percolation threshold showed a strong linear dependence on the net charge of the constituent lipids. Second, the vesicular clusters were characterized using a canonical coordinate frame spanned by the fractal dimension and the porosity of the cluster images. MLVs made of different lipid constituents formed different domains on such representations. The location of the individual domains relative to a simulated random cluster seemed to provide a measure of order-element present in such clusters. The specificity of the domain locations and their sensitivity to alteration in a microenvironment was studied in some detail. Copyright 1999 Academic Press.