Does α-Tocopherol Flip-Flop Help to Protect Membranes Against Oxidation?

J Phys Chem B. 2018 Nov 15;122(45):10362-10370. doi: 10.1021/acs.jpcb.8b09064. Epub 2018 Nov 6.

Abstract

α-Tocopherols (α-toc) are crucial in protecting biological membranes against oxidation by free radicals. We investigate the behavior of α-toc molecules in lipid bilayers containing oxidized lipids by molecular dynamics (MD) simulations. To verify the approach, the location and orientation of α-toc are first shown to be in agreement with previous experimental results. The simulations further show that α-toc molecules stay inside the lipid bilayer with their hydroxyl groups in contact with the bilayer surface. Interestingly, interbilayer α-toc flip-flop was observed in both oxidized and nonoxidized bilayers with significantly higher frequency in aldehyde lipid bilayer. Free-energy calculations were performed, and estimates of the flip-flop rates across the bilayers were determined. As the main finding, our results show that the presence of oxidized lipids leads to a significant decrease of free-energy barriers and that the flip-flop rates depend on the type of oxidized lipid present. Our results suggest that α-toc molecules could potentially act as high-efficacy scavengers of free radicals to protect membranes from oxidative attack and help stabilize them under oxidative stress.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antioxidants / chemistry*
  • Lipid Bilayers / chemistry*
  • Molecular Dynamics Simulation
  • Oxidation-Reduction
  • Phosphatidylcholines / chemistry
  • Thermodynamics
  • alpha-Tocopherol / chemistry*

Substances

  • Antioxidants
  • Lipid Bilayers
  • Phosphatidylcholines
  • 1-palmitoyl-2-linoleoylphosphatidylcholine
  • alpha-Tocopherol