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Journal of Lipid Research, Vol. 44, 1940-1945, October 2003
Copyright © 2003 by American Society for Biochemistry and Molecular Biology

The effect of vitamin E on the structure of membrane lipid assemblies

A. Bradford^*, J. Atkinson, N. Fuller^* and R. P. Rand^1,*

^* Departments of Biological Sciences, Brock University, St. Catharines, Ontario, Canada L2S 3A1
Chemistry, Brock University, St. Catharines, Ontario, Canada L2S 3A1

¹ To whom correspondence should be addressed. e-mail: rrand{at}brocku.ca

The effects of vitamin E on the activity of membrane-dependent enzymes suggest that it acts indirectly by modifying some properties of the lipid host. The effects of -tocopherol (-T) and -tocopherol hemisuccinate (-THS) on phospholipid monolayer structure, curvature, and bending elasticity were examined using X-ray diffraction and the osmotic stress method. These ligands were mixed with the hexagonal phase-forming lipid, dioleoylphosphatidylethanolamine (DOPE). Increasing levels up to 50 mol% -T in DOPE in excess water result in a systematic decrease in the lattice dimension. Analysis of the structural changes imposed by -T shows that it contributes a spontaneous radius of curvature of -13.7 Å. This unusually negative value is comparable to diacylglycerols. -T does not affect the bending elasticity of these monolayers. -THS in its charged form decreases membrane curvature, but in its undissociated neutral form has a qualitatively similar but reduced effect on monolayer curvature, as does -T.

We discuss these results in terms of the local stresses such ligands would produce in the vicinity of a membrane protein, and how one might expect proteins to respond to such stress.

Abbreviations: -T, -tocopherol; -THS, -tocopherol hemisuccinate; DAG, diacylglycerol; DCG, dicaprylglycerol; DOG, dioleoylglycerol; DOPC, dioleoylphosphatidylcholine; DOPE, dioleoylphosphatidylethanolamine; H_II, hexagonal phase; K_cp, bending modulus

Supplementary key words -tocopherol • spontaneous curvature • dioleoylphosphatidylethanolamine • -tocopherol hemisuccinate

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