Theoretical modeling of hydroxyl-radical-induced lipid peroxidation reactions

J Phys Chem B. 2007 May 24;111(20):5684-93. doi: 10.1021/jp0650782. Epub 2007 May 2.

Abstract

The OH-radical-induced mechanism of lipid peroxidation, involving hydrogen abstraction followed by O2 addition, is explored using the kinetically corrected hybrid density functional MPWB1K in conjunction with the MG3S basis set and a polarized continuum model to mimic the membrane interior. Using a small nonadiene model of linoleic acid, it is found that hydrogen abstraction preferentially occurs at the mono-allylic methylene groups at the ends of the conjugated segment rather than at the central bis-allylic carbon, in disagreement with experimental data. Using a full linoleic acid, however, abstraction is correctly predicted to occur at the central carbon, giving a pentadienyl radical. The Gibbs free energy for abstraction at the central C11 is approximately 8 kcal/mol, compared to 9 kcal/mol at the end points (giving an allyl radical). Subsequent oxygen addition will occur at one of the terminal atoms of the pentadienyl radical fragment, giving a localized peroxy radical and a conjugated butadiene fragment, but is associated with rather high free energy barriers and low exergonicity at the CPCM-MPWB1K/MG3S level. The ZPE-corrected potential energy surfaces obtained without solvent effects, on the other hand, display considerably lower barriers and more exergonic reactions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Hydroxyl Radical / chemistry*
  • Lipid Peroxidation*
  • Lipids / chemistry*
  • Models, Chemical*
  • Models, Molecular
  • Molecular Structure
  • Oxygen / chemistry
  • Thermodynamics

Substances

  • Lipids
  • Hydroxyl Radical
  • Oxygen