Simultaneous determination of the elastic properties of the lipid bilayer by atomic force microscopy: bending, tension, and adhesion.

A nanodrum of an unsupported L-α-phosphatidylcholine bilayer on a ∼7 μm pore was studied using a new experimental setup that permits atomic force microscopy (AFM) in conjunction with the electrical determination of trans-bilayer channels, thus checking its unilamellar character. In these nanodrums, the bilayer engulfs the intruding AFM tip with an adhesion similar to the attraction between two mica supported bilayers brought into close contact. Using this response and the finding of a nonlinear behavior of the Canham-Helfrich elastic model allows for the simultaneous determination of the elastic properties of the membrane. A bending modulus (κ = 1.5 ± 0.6 × 10(-19 )J) and a lateral tension (σ = 1.9 ± 0.7 mN/m) were determined for this case. Most importantly, an adhesion constant (w = 4.6 ± 2.2 mJ/m(2)) was determined from a particular response to deformation of large membrane patches.