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RESEARCH PAPERS: Papers on Cell Biomechanics

Bilayer Membrane Bending Stiffness by Tether Formation From Mixed PC-PS Lipid Vesicles

[+] Author and Article Information
J. Song, R. E. Waugh

Department of Biophysics, University of Rochester, School of Medicine and Dentistry, Rochester, NY 14642

J Biomech Eng 112(3), 235-240 (Aug 01, 1990) (6 pages) doi:10.1115/1.2891178 History: Received December 22, 1989; Revised May 15, 1990; Online March 17, 2008

Abstract

Recently, a new approach to measure the bending stiffness (curvature elastic modulus) of lipid bilayer membrane was developed (Biophys. J., Vol. 55; pp. 509–517, 1989). The method involves the formation of cylindrical membrane strands (tethers) from bilayer vesicles. The bending stiffness (B) can be calculated from measurements of the tether radius (Rt ) as a function of the axial force (f) on the tether: B =f·Rt /2π. In the present report, we apply this method to determine the bending stiffness of bilayer membranes composed of mixtures of SOPC (1-stearoyl-2-oleoyl phosphatidyl choline) and POPS (1-palmitoyl-2-oleoyl phosphatidyl serine). Three different mixtures were tested: pure SOPC, SOPC plus 2 percent (mol/mol) POPS, and SOPC plus 16 percent POPS. The bending stiffness determined for these three different lipid mixtures were not significantly different (1.6–1.8×10-12 ergs). Because POPS carries a net negative charge, these results indicate that changes in the density of the membrane surface charge have no effect on the intrinsic rigidity of the membrane. The values we obtain are consistent with published values for the bending stiffness of other membranes determined by different methods. Measurements of the aspiration pressure, the tether radius and the tether force were used to verify a theoretical relationship among these quantities at equilibrium. The ratio of the theoretical force to the measured force was 1.12 ± 0.17.

Copyright © 1990 by The American Society of Mechanical Engineers
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