Finite Phase-separation FRET I: A quantitative model valid for bilayer nanodomains

Multicomponent lipid mixtures exhibit complex phase behavior, including coexistence of nanoscopic fluid phases in ternary mixtures mimicking the composition of the outer leaflet of mammalian plasma membrane. The physical mechanisms responsible for the small size of phase domains are unknown, due in part to the difficulty of determining the size and lifetime distributions of small, fleeting domains. Steady-state FRET provides information about the spatial distribution of lipid fluorophores in a membrane, and with an appropriate model can be used to determine the size of phase domains. Starting from a radial distribution function for a binary hard disk fluid, we develop a domain size-dependent model for stimulated acceptor emission. We compare the results of the model to two similar, recently published models.