Viscoelasticity of BLM from choline plasmalogen, alkylacyl- and diacyl-glycerophosphocholines

Mechanical characteristics of bilayer lipid membranes (BLM) composed of alkenylacyl-, alkylacyl-, and diacyl-glycerophosphocholines were studied by measuring modulus of elasticity in the direction normal to BLM plane, E perpendicular, and coefficient of dynamic viscosity eta. Alkenylacyl-glycerophosphocholine (choline plasmalogen) BLM typically show larger values of E perpendicular and eta as compared to their analogs, suggesting a tighter packing of their hydrophobic regions. Increasing cholesterol concentrations are associated with monotonically increasing values of parameters E perpendicular and eta of plasmalogen BLM, whereas a nonmonotonic dependence of these parameters with a maximum around c = 66 mol% cholesterol is typical for the diacyl analog POPC. This may be due to the formation of cholesterol clusters at c > 66 mol%.