A NOVEL MICROPIPET METHOD FOR MEASURING THE BENDING MODULUS OF VESICLE MEMBRANES

A theoretical model and an experiment are presented for determining th e bending modulus of a bilayer vesicle membrane. The vesicle is held w ith a pipet having a radius between 1 and 2 mu m, and the tension in t he membrane is changed by changing the suction pressure. Then the vesi cle membrane is deformed by aspirating it into a smaller pipet having a radius on the order of 0.5 mu m. The relationship between the suctio n pressures in the two pipets is found to be linear, as predicted by t he theoretical model. The curvature of the vesicle membrane at the pip et orifice and the bending modulus are found with the help of the mode l from the slope and the intercept of the linear experimental relation ship between the suction pressures in the two pipets. The bending modu lus for the two SOPC membranes studied in these experiments was found to be either 0.6 or 1.15 x 10(-19) J, which is similar to the values m easured previously.