[Calcium-induced changes in bilayer membranes from oxidized cholesterol]

Elastic properties of oxidized cholesterol bilayers in n-octane and membrane solvent free were studied by measuring Young modulus E perpendicular in the direction perpendicular to the membrane plane as a function of concentration of calcium ions. Interaction between calcium ions and solvent free bilayers resulted in a significant increases of Young modulus E perpendicular in the concentration range 20-40 mmol/l Ca2+. It is suggested that the hardening of the membrane is caused by some structural changes in the hydrophobic region of the membrane.