Abstract
We measure the elastic response of a free-standing lipid membrane to a local indentation by using an atomic force microscope. Starting point is a planar gold-coated alumina substrate with a chemisorbed 3-mercaptopropionic acid monolayer displaying circular pores of very well defined and tunable size, over which bilayers composed of N, N,-dimethyl- N, N,-dioctadecylammonium bromide or 1,2-dioleoyl-3-trimethylammonium-propane chloride were spread. Centrally indenting these “nanodrums” with an atomic force microscope tip yields force-indentation curves, which we quantitatively analyze by solving the corresponding shape equations of continuum curvature elasticity. Since the measured response depends in a known way on the system geometry (pore size, tip radius) and on material parameters (bending modulus, lateral tension), this opens the possibility to monitor local elastic properties of lipid membranes in a well-controlled setting.
Highlights
Since the invention of the atomic force microscope (AFM) in 1986, the spatial analysis of soft biological samples has become a major aim in cellular and molecular biophysics [1]
The gold surface was first functionalized with a monolayer of 3-mercaptopropionic acid followed by an incubation for 4 h at T 1⁄4 55°C with large unilamellar vesicles composed of either positively charged N,N,dimethyl-N,N,dioctadecylammonium bromide (DODAB) or 1,2-dioleoyl-3-trimethylammonium-propane chloride (DOTAP) (0.5 mg/ml in 10 mM Tris, pH 8.6)
Two AFM images obtained from contact mode imaging of a DODAB bilayer covering the highly ordered porous alumina with pore radii of Rpore 1⁄4 33 nm using a low (0.9 nN, Fig. 2 A) and high (2.7 nN, Fig. 2 B) load force are shown
Summary
Since the invention of the atomic force microscope (AFM) in 1986, the spatial analysis of soft biological samples has become a major aim in cellular and molecular biophysics [1]. At larger forces (Fig. 2 B), the bilayer-covered pores resemble the uncovered porous substrate due to maximal indentation of the membrane into the pores.
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call