Skip to main content
PMC home page
Biophysical Journal logoLink to Biophysical Journal
. 1994 Sep;67(3):1067–1079. doi: 10.1016/S0006-3495(94)80572-7

Solute effects on the colloidal and phase behavior of lipid bilayer membranes: ethanol-dipalmitoylphosphatidylcholine mixtures.

U Vierl 1, L Löbbecke 1, N Nagel 1, G Cevc 1
PMCID: PMC1225459  PMID: 7811917

Abstract

By means of the scanning differential calorimetry, x-ray diffractometry, and the dynamic light scattering, we have systematically studied the phase and packing properties of dipalmitoylphosphatidylcholine vesicles or multibilayers in the presence of ethanol. We have also determined the partial ternary phase diagram of such dipalmitoylphosphatidylcholine/water/ethanol mixtures. The directly measured variability of the structural bilayer parameters implies that ethanol binding to the phospholipid bilayers increases the lateral as well as the transverse repulsion between the lipid molecules. This enlarges the hydrocarbon tilt (by up to 23 degrees) and molecular area (by < or = 40%). Ethanol-phospholid association also broadens the interface and, thus, promotes lipid headgroup solvation. This results in excessive swelling (by 130%) of the phosphatidylcholine bilayers in aqueous ethanol solutions. Lateral bilayer expansion, moreover, provokes a successive interdigitation of the hydrocarbon chains in the systems with bulk ethanol concentrations of 0.4-1.2 M. The hydrocarbon packing density as well as the propensity for the formation of lamellar gel phases simultaneously increase. The pretransition temperature of phosphatidylcholine bilayers is more sensitive to the addition of alcohol (initial shift: delta Tp = 22 degrees C/mol) than the subtransition temperature (delta Ts reversible 5 degrees C/mol), whereas the chain-melting phase transition temperature is even less affected (delta Tm = 1.8 degrees C/mol). After an initial decrease of 3 degrees for the bulk ethanol concentrations below 1.2 M, the Tm value increases by 2.5 degrees above this limiting concentration. The gel-phase phosphatidylcholine membranes below Tm are fully interdigitated above this limiting concentration. The chain tilt on the fringe of full chain interdigitation is zero and increases with higher ethanol concentrations. Above Tm, some of the lipid molecules are solubilized by the bound ethanol molecules. More highly concentrated ethanol solutions (> 7 M) solubilize the phosphatidylcholine bilayers with fluid chains fully and result in the formation of mixed lipid-alcohol micelles.

Full text

PDF
1067

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Blaurock A. E., Worthington C. R. Treatment of low angle x-ray data from planar and concentric multilayered structures. Biophys J. 1966 May;6(3):305–312. doi: 10.1016/S0006-3495(66)86658-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Boni L. T., Minchey S. R., Perkins W. R., Ahl P. L., Slater J. L., Tate M. W., Gruner S. M., Janoff A. S. Curvature dependent induction of the interdigitated gel phase in DPPC vesicles. Biochim Biophys Acta. 1993 Mar 14;1146(2):247–257. doi: 10.1016/0005-2736(93)90363-5. [DOI] [PubMed] [Google Scholar]
  3. Cevc G., Marsh D. Hydration of noncharged lipid bilayer membranes. Theory and experiments with phosphatidylethanolamines. Biophys J. 1985 Jan;47(1):21–31. doi: 10.1016/S0006-3495(85)83872-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Finegold L., Singer M. A. The metastability of saturated phosphatidylcholines depends on the acyl chain length. Biochim Biophys Acta. 1986 Mar 13;855(3):417–420. doi: 10.1016/0005-2736(86)90086-6. [DOI] [PubMed] [Google Scholar]
  5. Komatsu H., Guy P. T., Rowe E. S. Effect of unilamellar vesicle size on ethanol-induced interdigitation in dipalmitoylphosphatidylcholine. Chem Phys Lipids. 1993 Apr;65(1):11–21. doi: 10.1016/0009-3084(93)90077-g. [DOI] [PubMed] [Google Scholar]
  6. Lewis R. N., Mak N., McElhaney R. N. A differential scanning calorimetric study of the thermotropic phase behavior of model membranes composed of phosphatidylcholines containing linear saturated fatty acyl chains. Biochemistry. 1987 Sep 22;26(19):6118–6126. doi: 10.1021/bi00393a026. [DOI] [PubMed] [Google Scholar]
  7. Mattai J., Sripada P. K., Shipley G. G. Mixed-chain phosphatidylcholine bilayers: structure and properties. Biochemistry. 1987 Jun 16;26(12):3287–3297. doi: 10.1021/bi00386a007. [DOI] [PubMed] [Google Scholar]
  8. McIntosh T. J., Magid A. D., Simon S. A. Range of the solvation pressure between lipid membranes: dependence on the packing density of solvent molecules. Biochemistry. 1989 Sep 19;28(19):7904–7912. doi: 10.1021/bi00445a053. [DOI] [PubMed] [Google Scholar]
  9. Nagel N. E., Cevc G., Kirchner S. The mechanism of the solute-induced chain interdigitation in phosphatidylcholine vesicles and characterization of the isothermal phase transitions by means of dynamic light scattering. Biochim Biophys Acta. 1992 Nov 9;1111(2):263–269. doi: 10.1016/0005-2736(92)90319-h. [DOI] [PubMed] [Google Scholar]
  10. Rowe E. S. Induction of lateral phase separations in binary lipid mixtures by alcohol. Biochemistry. 1987 Jan 13;26(1):46–51. doi: 10.1021/bi00375a007. [DOI] [PubMed] [Google Scholar]
  11. Simon S. A., McIntosh T. J. Interdigitated hydrocarbon chain packing causes the biphasic transition behavior in lipid/alcohol suspensions. Biochim Biophys Acta. 1984 Jun 13;773(1):169–172. doi: 10.1016/0005-2736(84)90562-5. [DOI] [PubMed] [Google Scholar]
  12. Slater J. L., Huang C. H. Interdigitated bilayer membranes. Prog Lipid Res. 1988;27(4):325–359. doi: 10.1016/0163-7827(88)90010-0. [DOI] [PubMed] [Google Scholar]
  13. Wiener M. C., Suter R. M., Nagle J. F. Structure of the fully hydrated gel phase of dipalmitoylphosphatidylcholine. Biophys J. 1989 Feb;55(2):315–325. doi: 10.1016/S0006-3495(89)82807-3. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Biophysical Journal are provided here courtesy of The Biophysical Society

RESOURCES