EFFECTS OF SIZE OF MACROCYCLIC POLYAMIDES ON THEIR RATE OF DIFFUSION IN MODEL MEMBRANES

A series of homologous amphiphilic molecules with surface areas in the range of 0.3 nm(2) to 3.0 nm(2) were prepared and used to investigate the diffusion in model dimyristoylphosphatidylcholine membranes as a function of temperature. The diffusion behavior of smaller molecules c an be described by the interfacial viscosity limited free area theory promoted by Vaz and his co-workers, and that of the larger molecules c an best be modeled by a recent interpretation of the theoretical descr iption proposed by Evans and Sackmann, The experimental data show that the rate of diffusion is controlled by the size of the molecules at t he interface of the lipid membrane, and provide evidence for a view of the membrane as a hydrodynamic triple layer with a low-viscosity cent ral layer encased by two more viscous, yet fluid, layers.