Figure 1.

Plastic penetration of an AFM tip through a lipid bilayer serves as a fingerprint of the mechanical stability of the membrane. (A) A 5 × 5 μm² AC mode image of a supported lipid bilayer of DPPC in a liquid environment (the section profile enclosed reveals the characteristic thickness of ∼7 nm). (B) Typical force curve of a lipid bilayer. As the AFM tip approaches the surface (red trace, from right to left), the lipid bilayer is deformed until a sudden penetration occurs. (C) Schematics of the system studied. Surface planar bilayers are formed on a hydrophilic surface in the presence of the electrolyte solution. Ions present in solution specifically interact with the zwitterionic headgroups of membranes, altering their compactness and their mechanical stability.