PHASE TOPOLOGY AND PERCOLATION IN 2-COMPONENT LIPID BILAYERS - A MONTE-CARLO APPROACH

Monte Carlo simulations of fluorescence recovery after photobleaching (FRAP) experiments on two-component lipid bilayers systems in the soli d-fluid phase coexistence region were carried out to study the geometr y and size of fluid domains in these bilayers. The gel phase was simul ated by superposable elliptical domains, which were either of predeter mined dimensions, increasing in number with increasing gel phase fract ion, or of predetermined number, increasing in dimensions with increas ing gel phase fraction. The simulations were done from two perspective s: 1) a time-independent analysis of fractional fluorescence recovery as a function of fractional fluid phase in the system; and 2) a time-d ependent analysis of fractional fluorescence recovery as a function of time al a given fraction of fluid phase in the system. The time-depen dent simulations result in recovery curves that are directly comparabl e to experimental FRAP curves and provide topological and geometrical models for the coexisting phases that are consistent with the experime ntal result.