Condensed complexes in vesicles containing cholesterol and phospholipids

Arun Radhakrishnan, Harden McConnell

Research output: Contribution to journalArticle

117 Citations (Scopus)

Abstract

Animal cell membranes pose conceptual problems related to the physical chemistry of liquids. An avenue to the solution of some of these problems has been opened by the discovery of liquid-liquid immiscibility in synthetic membranes composed of cholesterol and phospholipids. This discovery has led to the development of a thermodynamic model involving condensed complexes. In this model, the phospholipids with longer fatty-acid chains react reversibly with cholesterol to form complexes. The complexes themselves can have a repulsive interaction with other phospholipids, leading to immiscibility. A striking example of this effect is revealed in the phase diagrams of ternary mixtures of cholesterol, a saturated phosphatidylcholine (or sphingomyelin), and an unsaturated phosphatidylcholine. As found by a number of investigators, all binary pairs are miscible in bilayers, whereas the ternary mixture can form two liquid phases. The model of condensed complexes accounts for this effect. Condensed complexes also have a major effect on the chemical activity of cholesterol and on the ordering of phospholipid acyl chains both in the presence and absence of phase separations. Model calculations of phospholipid order parameters account for several features of the deuterium MMR spectra of labeled phospholipid molecules in bilayer mixtures with cholesterol.

Original languageEnglish (US)
Pages (from-to)12662-12666
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume102
Issue number36
DOIs
StatePublished - Sep 6 2005

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Phospholipids
Cholesterol
Phosphatidylcholines
Physical Chemistry
Sphingomyelins
Deuterium
Thermodynamics
Fatty Acids
Research Personnel
Cell Membrane
Membranes

Keywords

  • Chemical activity
  • Deuterium NMR
  • Membrane
  • Phase diagrams

ASJC Scopus subject areas

  • Genetics
  • General

Cite this

Condensed complexes in vesicles containing cholesterol and phospholipids. / Radhakrishnan, Arun; McConnell, Harden.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 102, No. 36, 06.09.2005, p. 12662-12666.

Research output: Contribution to journalArticle

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