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Effects of polar carotenoids on dimyristoylphosphatidylcholine membranes: a spin-label study. Biochim Biophys Acta 1992 Mar 23;1105(1):97-108

Date

03/23/1992

Pubmed ID

1314674

DOI

10.1016/0005-2736(92)90167-k

Abstract

Spin labeling methods were used to study the structure and dynamic properties of dimyristoylphosphatidylcholine (DMPC) membranes as a function of temperature and the mole fraction of polar carotenoids. The results in fluid phase membranes are as follows: (1) Dihydroxycarotenoids, zeaxanthin and violaxanthin, increase order, decrease motional freedom and decrease the flexibility gradient of alkyl chains of lipids, as was shown with stearic acid spin labels. The activation energy of rotational diffusion of the 16-doxylstearic acid spin label is about 35% less in the presence of 10 mol% of zeaxanthin. (2) Carotenoids increase the mobility of the polar headgroups of DMPC and increase water accessibility in that region of membrane, as was shown with tempocholine phosphatidic acid ester. (3) Rigid and highly anisotropic molecules dissolved in the DMPC membrane exhibit a bigger order of motion in the presence of polar carotenoids as was shown with cholestane spin label (CSL) and androstane spin label (ASL). Carotenoids decrease the rate of reorientational motion of CSL and do not influence the rate of ASL, probably due to the lack of the isooctyl side chain. The abrupt changes of spin label motion observed at the main phase transition of the DMPC bilayer are broadened and disappear at the presence of 10 mol% of carotenoids. In gel phase membranes, polar carotenoids increase motional freedom of most of the spin labels employed showing a regulatory effect of carotenoids on membrane fluidity. Our results support the hypothesis of Rohmer, M., Bouvier, P. and Ourisson, G. (1979) Proc. Natl. Acad. Sci. USA 76, 847-851, that carotenoids regulate the membrane fluidity in Procaryota as cholesterol does in Eucaryota. A model is proposed to explain these results in which intercalation of the rigid rod-like polar carotenoid molecules into the membrane enhances extended trans-conformation of the alkyl chains, decreases free space in the bilayer center, separate the phosphatidylcholine headgroups and decreases interaction between them.

Author List

Subczynski WK, Markowska E, Gruszecki WI, Sielewiesiuk J

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

Affinity Labels
Carotenoids
Cholesterol
Dimyristoylphosphatidylcholine
Electron Spin Resonance Spectroscopy
Lipid Bilayers
Membrane Fluidity
Molecular Structure
Temperature
Xanthophylls
Zeaxanthins
beta Carotene