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Title: Membrane curvature, lipid segregation, and structural transitions for phospholipids under dual-solvent stress

Abstract

Amphiphiles respond both to polar and to nonpolar solvents. In this paper X-ray diffraction and osmotic stress have been used to examine the phase behavior, the structural dimensions, and the work of deforming the monolayer-lined aqueous cavities formed by mixtures of dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC) as a function of the concentration of two solvents, water and tetradecane (td). In the absence of td, most PE/PC mixtures show only lamellar phases in excess water; all of these become single reverse hexagonal (H{sub II}) phases with addition of excess td. The spontaneous radius of curvature R{sub 0} of lipid monolayers, as expressed in these H{sub II} phases, is allowed by the relief of hydrocarbon chain stress by td; R{sub 0} increases with the ratio DOPC/DOPE. Single H{sub II} phases stressed by limited water or td show several responses. (a) the molecular area is compressed at the polar end of the molecule and expanded at the hydrocarbon ends. (b) For circularly symmetrical water cylinders, the degrees of hydrocarbon chain splaying and polar group compression are different for molecules aligned in different directions around the water cylinder. (c) A pivotal position exists along the length of the phospholipid molecule where little area changemore » occurs as the monolayer is bent to increasing curvatures. (d) By defining R{sub 0} at the pivotal position, the authors find that measured energies are well fit by a quadratic bending energy. (e) For lipid mixtures, enforced deviation of the H{sub II} monolayer from R{sub 0} is sufficiently powerful to cause demixing of the phospholipids in a way suggesting that the DOPE/DOPC ratio self-adjusts so that its R{sub 0} matches the amount of td or water available, i.e., that curvature energy is minimized.« less

Authors:
;  [1];  [2];  [3]
  1. (Brock Univ., St. Catharines, Ontario (Canada))
  2. (Princeton Univ., NJ (USA))
  3. (National Institutes of Health, Bethesda, MD (USA))
Publication Date:
OSTI Identifier:
7008608
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemistry; (USA); Journal Volume: 29:1
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; MEMBRANES; MOLECULAR STRUCTURE; PHOSPHOLIPIDS; X-RAY DIFFRACTION; LIPIDS; OSMOSIS; STRUCTURAL CHEMICAL ANALYSIS; COHERENT SCATTERING; DIFFRACTION; DIFFUSION; ESTERS; ORGANIC COMPOUNDS; ORGANIC PHOSPHORUS COMPOUNDS; SCATTERING; 550602* - Medicine- External Radiation in Diagnostics- (1980-)

Citation Formats

Rand, R.P., Fuller, N.L., Gruner, S.M., and Parsegian, V.A. Membrane curvature, lipid segregation, and structural transitions for phospholipids under dual-solvent stress. United States: N. p., 1990. Web. doi:10.1021/bi00453a010.
Rand, R.P., Fuller, N.L., Gruner, S.M., & Parsegian, V.A. Membrane curvature, lipid segregation, and structural transitions for phospholipids under dual-solvent stress. United States. doi:10.1021/bi00453a010.
Rand, R.P., Fuller, N.L., Gruner, S.M., and Parsegian, V.A. Tue . "Membrane curvature, lipid segregation, and structural transitions for phospholipids under dual-solvent stress". United States. doi:10.1021/bi00453a010.
@article{osti_7008608,
title = {Membrane curvature, lipid segregation, and structural transitions for phospholipids under dual-solvent stress},
author = {Rand, R.P. and Fuller, N.L. and Gruner, S.M. and Parsegian, V.A.},
abstractNote = {Amphiphiles respond both to polar and to nonpolar solvents. In this paper X-ray diffraction and osmotic stress have been used to examine the phase behavior, the structural dimensions, and the work of deforming the monolayer-lined aqueous cavities formed by mixtures of dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC) as a function of the concentration of two solvents, water and tetradecane (td). In the absence of td, most PE/PC mixtures show only lamellar phases in excess water; all of these become single reverse hexagonal (H{sub II}) phases with addition of excess td. The spontaneous radius of curvature R{sub 0} of lipid monolayers, as expressed in these H{sub II} phases, is allowed by the relief of hydrocarbon chain stress by td; R{sub 0} increases with the ratio DOPC/DOPE. Single H{sub II} phases stressed by limited water or td show several responses. (a) the molecular area is compressed at the polar end of the molecule and expanded at the hydrocarbon ends. (b) For circularly symmetrical water cylinders, the degrees of hydrocarbon chain splaying and polar group compression are different for molecules aligned in different directions around the water cylinder. (c) A pivotal position exists along the length of the phospholipid molecule where little area change occurs as the monolayer is bent to increasing curvatures. (d) By defining R{sub 0} at the pivotal position, the authors find that measured energies are well fit by a quadratic bending energy. (e) For lipid mixtures, enforced deviation of the H{sub II} monolayer from R{sub 0} is sufficiently powerful to cause demixing of the phospholipids in a way suggesting that the DOPE/DOPC ratio self-adjusts so that its R{sub 0} matches the amount of td or water available, i.e., that curvature energy is minimized.},
doi = {10.1021/bi00453a010},
journal = {Biochemistry; (USA)},
number = ,
volume = 29:1,
place = {United States},
year = {Tue Jan 09 00:00:00 EST 1990},
month = {Tue Jan 09 00:00:00 EST 1990}
}