Studying Bending Rigidity of Model Vesicles and Cell Plasma Membrane using Lipid Nanotubes

Abstract

Mechanical properties of artificial lipid membranes have been examined by variety of techniques, like X-ray diffraction, NMR, micropipette aspiration or fluctuation analyses. However, new methods able to study membranes in most natural environment and with potential to approach cell membranes directly are desirable.We recently reported a new method for radial sizing of membrane nanotubes. The technique is based on imaging of membrane translocation from a lipid reservoir (multilamellar vesicle or cell with attached plasma membrane bleb) through the nanotube walls to a newly formed expanding vesicle. Since the nanotube radius is defined by the bilayer stiffness, the membrane bending rigidity modulus can be studied with this technique.Here we have observed changes in bending rigidity of model membranes upon varying cholesterol content of the membrane (0, 5, 10 and 20 mol % cholesterol), exchanging type of membrane sterol (10 mol % of cholesterol, lathosterol, sitosterol, 7-dehydrocholesterol or lanosterol) and increasing salt concentration in solution (0, 100, 200 and 500 mM sodium chloride). We also have applied the method to analyze cell plasma membrane and detected changes induced by MβCD extrusion of cholesterol. The method proved to be quite sensitive for both artificial and cell plasma membranes and all obtained results are in agreement with previous studies.