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Effects of polar carotenoids on the shape of the hydrophobic barrier of phospholipid bilayers. Biochim Biophys Acta 1998 Jan 19;1368(2):235-46

Date

02/12/1998

Pubmed ID

9459601

DOI

10.1016/s0005-2736(97)00182-x

Abstract

The value of Az (z-component of the hyperfine interaction tensor) obtained directly from X-band EPR spectra of stearic acid spin labels and tempocholine dipalmitoylphosphatidic acid ester in frozen suspension of phosphatidylcholine (PC) membranes has been used as a hydrophobicity parameter. Using probes with the nitroxide moiety at various depths in the membrane, the shape of the hydrophobic barrier, which is determined by the extent of water penetration into the membrane, has been estimated. Incorporation of 10 mol% polar carotenoids, zeaxanthin, violaxanthin, or lutein into the saturated PC bilayer significantly increases the hydrophobicity of the membrane interior but decreases hydrophobicity (increases water penetration) in the polar headgroup region. Hydrophobicity at the membrane center increases from the level of propanolpentanol, which have dielectric constants of 10-20, to the level of dipropylamine, with a dielectric constant close to 3. Longer alkyl chains decrease the effect of polar carotenoids in the polar headgroup region, but not in the central hydrophobic region. In an unsaturated egg yolk PC membrane, polar carotenoids were found to increase the hydrophobicity of the membrane interior to a higher level than in saturated PC membranes. At the membrane center hydrophobicity reaches the level close to pure hexane (epsilon approximately 2). The above results were confirmed by studying accessibility of Fe(CN)6(3-) ion dissolved in water into dimyristoyl-PC-lutein membranes at 30 degrees C. Obtained hydrophobicity profiles correlate well with permeability data for water in the literature.

Author List

Wisniewska A, Subczynski WK

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

Anions
Carotenoids
Cell Membrane Permeability
Electron Spin Resonance Spectroscopy
Lipid Bilayers
Phosphatidylcholines