Lipid Diffusion in Giant Unilamellar Vesicles Is More than 2 Times Faster than in Supported Phospholipid Bilayers under Identical Conditions

The lateral diffusion coefficients of a BODIPY tail-labeled lipid in two model systems, namely, free-standing giant unilamellar vesicles (GUVs) and supported phospholipid bilayers (SPBs), were determined by fluorescence correlation spectroscopy (FCS) using the Z-scan approach. For the first time, the performed measurements on 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayers maintain exactly the same experimental conditions for both systems, which allows for a quantitative comparison of lipid diffusion in these two commonly used model membranes. The results obtained revealed that the lipid mobility in free-standing bilayers (D = 7.8 ± 0.8 μm2 s-1) is significantly higher than in the bilayer created on the solid support (mica) (D = 3.1 ± 0.3 μm2 s-1).