1 research outputs found
Aescin Incorporation and Nanodomain Formation in DMPC Model Membranes
The
saponin aescin from the horse chestnut tree is a natural surfactant
well-known to self-assemble as oriented-aggregates at fluid interfaces.
Using model membranes in the form of lipid vesicles and Langmuir monolayers,
we study the mixing properties of aescin with the phase-segregating
phospholipid 1,2-dimyristoyl-<i>sn</i>-glycero-phosphocholine
(DMPC). The binary membranes are experimentally studied on different
length scales ranging from the lipid headgroup area to the macroscopic
scale using small-angle X-ray scattering (SAXS), photon correlation
spectroscopy (PCS), and differential scanning calorimetry (DSC) with
binary bilayer vesicles and Langmuir tensiometry (LT) with lipid monolayers
spread on the surface of aescin solutions. The binary interaction
was found to strongly depend on aescin concentration in two well differentiated
concentration regimes. Below 7 mol %, the results reveal phase segregation
of nanometer-sized aescin-rich domains in an aescin-poor continuous
bilayer. Above this concentration, aescin–aescin interactions
dominate, which inhibit vesicle formation but lead to the formation
of new membrane aggregates of smaller sizes. From LT studies in monolayers,
the interaction of aescin with DMPC was shown to be stronger in the
condensed phase than in the liquid expanded phase. Furthermore, a
destructuring role was revealed for aescin on phospholipid membranes,
similar to the fluidizing effect of cholesterol and nonsteroidal anti-inflammatory
drugs (NSAIDs) on lipid bilayers