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Influence of phospholipid unsaturation on the cholesterol distribution in membranes. Biochimie 1991 Oct;73(10):1311-6

Date

10/01/1991

Pubmed ID

1664241

DOI

10.1016/0300-9084(91)90094-h

Abstract

Over the last half decade, we have studied saturated and unsaturated phosphatidylcholine (PC)-cholesterol membranes, with special attention paid to fluid-phase immiscibility in cis-unsaturated PC-cholesterol membranes. The investigations were carried out with fatty acid and sterol analogue spin labels for which reorientational diffusion of the nitroxide was measured using conventional ESR technique. We also used saturation recovery ESR technique where dual probes were utilized. Bimolecular collision rates between a membrane-soluble square-planar copper complex,3-ethoxy-2-oxobutyraldehyde bis(N4,N4-dimethylthiosemicarbazonato)copper(II) (CuKTMS2) and one of several nitroxide radical lipid-type spin labels were determined by measuring the nitroxide spin-lattice relaxation time (T1). The results obtained in all these studies can be explained if the following model is assumed: 1) at physiological temperatures, fluid-phase micro-immiscibility takes place in cis-unsaturated PC-cholesterol membranes, which induces cholesterol-rich domains in the membrane due to the steric nonconformability between the rigid fused-ring structure of cholesterol and the 30 degrees bend at the cis double bond of the alkyl chains of unsaturated PC. 2) The cholesterol-rich domains are small and/or of short lifetime (10(-9) s to less than 10(-7) s). Our results also suggest that the extra space that is available for conformational disorder and accommodation of small molecules is created in the central part of the bilayer by intercalation of cholesterol in cis-unsaturated PC membrane due to the mismatch in the hydrophobic length and nonconformability between cis-unsaturated PC alkyl chains and the bulky tetracyclic ring of cholesterol.

Author List

Pasenkiewicz-Gierula M, Subczynski WK, Kusumi A

Author

Witold K. Subczynski PhD Professor in the Biophysics department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Cholesterol
Electron Spin Resonance Spectroscopy
Lipid Bilayers
Liposomes
Membranes, Artificial
Models, Chemical
Molecular Conformation
Phosphatidylcholines
Phospholipids