Experimental tests for protrusion and undulation pressures in phospholipid bilayers.

Published

Journal Article

Theoretical treatments predict that strong entropic pressures between adjacent bilayer membranes can arise from out of plane motions caused by either thermally induced bending undulations of the entire bilayer [Harbich, W., & Helfrich, W. (1984) Chem. Phys. Lipids 36, 39-63; Evans, E. A., & Parsegian, V. A. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 7132-7136] or protrusions of individual lipid molecules from the bilayer surface [Israelachvili, J. N., & Wennerström, H. (1992) J. Phys. Chem. 96, 520-531]. To determine the relative contributions of these motions to the repulsive pressure between phospholipid bilayers, the osmotic stress/X-ray diffraction method was used to measure the range and magnitude of the total repulsive pressure, and micropipet methods were used to measure the bending moduli of phosphatidylcholine bilayers containing lysophosphatidylcholine and polyunsaturated diarachidonoylphosphatidylcholine (DAPC) bilayers. In the gel phase, incorporation of equimolar lysophosphatidylcholine into phosphatidylcholine bilayers caused the hydrocarbon chains from apposing monolayers to interdigitate, but did not appreciably change the equilibrium fluid spacing in excess buffer from its control value of 12 A. In contrast, the incorporation of equimolar lysophosphatidylcholine into liquid-crystalline phase phosphatidylcholine bilayers markedly increased the range of the repulsive pressure so that equilibrium fluid separation increased from 15 to 28 A, and also decreased the bilayer bending modulus from 5.1 x 10(-13) to 1.3 x 10(-13) erg. Liquid-crystalline DAPC bilayers had intermediate values of both equilibrium fluid separation (20 A) and bending modulus (2.8 x 10(-13) erg). Analysis of these data indicates that (1) the relative importance of entropic pressures compared to the hydration pressure depends strongly on the composition and structure of the bilayer, (2) the protrusion pressure may contribute to the total repulsive pressure at large pressures or small fluid spacings, and (3) the repulsive undulation pressure, together with the attractive van der Waals pressure, is a primary factor in determining the fluid spacing at low and/or zero applied pressures in liquid-crystalline bilayers.

Full Text

Duke Authors

Cited Authors

  • McIntosh, TJ; Advani, S; Burton, RE; Zhelev, DV; Needham, D; Simon, SA

Published Date

  • July 11, 1995

Published In

Volume / Issue

  • 34 / 27

Start / End Page

  • 8520 - 8532

PubMed ID

  • 7612594

Pubmed Central ID

  • 7612594

International Standard Serial Number (ISSN)

  • 0006-2960

Digital Object Identifier (DOI)

  • 10.1021/bi00027a002

Language

  • eng

Conference Location

  • United States