1 research outputs found
Transport and Organization of Cholesterol in a Planar Solid-Supported Lipid Bilayer Depend on the Phospholipid Flip-Flop Rate
Understanding
the transport behavior of the cholesterol molecules
within a cell membrane is a key challenge in cell biology at present.
Here, we have applied sum frequency generation vibrational spectroscopy
to characterize the transport and organization of cholesterol in different
kinds of planar solid-supported lipid bilayers by combining achiral-
and chiral-sensitive polarization measurements. This method allows
us to distinguish the organization of cholesterol in tail-to-tail,
head-to-tail, head-to-head, and side-by-side manners. It is found
that the movement of cholesterol in the lipid bilayer largely depends
on the flip-flop rate of the phospholipid. The flip-flop dynamics
of the phospholipid and cholesterol are synchronous. In the solid-supported
zwitterionic phosphocholine lipid bilayer, the cholesterol molecules
flip quickly from the distal leaflet to the neutral proximal leaflet
of the bilayer and form tail-to-tail organization on both leaflets.
The phosphocholine lipid and cholesterol show the same flip-flop rate.
However, when the proximal leaflet is prepared using negative glycerol
phospholipids, cholesterol organizes itself by mainly forming an α–β
structure on the distal leaflet. Because of the strong interaction
between the glycerol phospholipid and the substrate, no or only partial
cholesterol molecules flip from the distal leaflet to the negatively
charged proximal leaflet. However, the cholesterol molecules undergo
flip-flop in the presence of salt solution because the ions weaken
the interaction between the negative phospholipid and the substrate