DYNAMIC HETEROGENEITY OF LIPIDS IN A SYST EM DIETHYL ESTER-WATER-LECITIN

The self-diffusion of lipid molecules in a system diethyl ester-water- lecitin at a lecitin concentration 10-90% was studied by NMR with the magnetic field impulse gradient. The diffusion time was 10(-3) -1 s, a nd the temperature was 310K. Depending on lecitin concentration, three regions with different dependence of the mode of diffusion attenuatio n of the spin echo amplitude on diffusion time were observed. In the f irst case (80-90%), the mode of diffusion attenuation depends on diffu sion time. This dependence is typical for the quasi-diffusional regime of self-diffusion. Physically, this regime may arise from the formati on of dynamic associates of lipid molecules. The lifetimes molecules i n the associates were determined. In the second case (60-70%), the mod e of attenuation does not depend on diffusion time, due to stabilizati on of the associates. At lower lecitin concentrations (10-50%),. the c hanges in attenuation are typical of limited self-diffusion. In this c ase, it is impossible to detect reliably the dynamic heterogeneity of lipids.