Lateral diffusion of lipids separated from rotational and translational diffusion of a fluid large unilamellar vesicle

A new method to separate lateral diffusion of lipids in spherical large unilamellar vesicles from the rotational and the translational diffusion of the vesicle as a whole is proposed. The lateral diffusion coefficient DL is obtained as a time-dependent part of the observed diffusion coefficient in vesicles of 800-nm diameters, by systematically changing the diffusion time interval of the high-field-gradient NMR measurement. Although the lipid is in a confined space, the DL of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine is (1.5 ± 0.6) × 10−11 m2 s−1 in the fluid state at 45 °C, more than one order of magnitude faster than the rotational and the translational diffusion coefficients of the vesicle by the hydrodynamic continuum model. The method provides a potential for quantifying the lateral diffusion of lipids and proteins in fluid bilayer vesicles as model cell membranes in a natural manner.

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► High-field-gradient NMR is applied to quantify lipid lateral diffusion in vesicles.
► Lateral diffusion of the lipid is separated from the vesicle motion as a whole.
► Lateral diffusion is analyzed as a time-dependent part of the observed diffusion.
► Lipid mobility is more than one order of magnitude faster than the vesicle motion.
► The method provides a potential for quantifying diffusion motion in biomembranes.