Invited Lecture. Hats and saddles in lipid membranes

Abstract

Extrinsic or intrinsic defects in membranes may produce deformations resembling hats or saddles. It is shown that hats cannot absorb much area without reducing the bending rigidity of the membrane below 10⁻ erg. Estimates indicate that intrinsic saddles are promoted by the stress profile of electrically neutral biological model membranes. The saddle structures might warp the membrane if they cooperate.