The behavior of alpha-tocopherol and cholesterol in the oxidized PLPC lipid bilayers a molecular dynamics study

Name: Phansiri Boonnoy

LCSH: Kasetsart University -- Dissertations. Ph.D. (Physics) 2021

Classification :.LCCS: QC173

LCSH: Kasetsart University. -- Department of Physics -- Dissertations

LCSH: Molecular dynamics

LCSH: Membrane lipids

LCSH: Bilayer lipid membranes

LCSH: Vitamin E

LCSH: Cholesterol

Abstract: Membrane lipids are particularly susceptible to oxidative attack by free radicals due to their high content of polyunsaturated phospholipids. Alphatocopherols (α-toc; vitamin E) and cholesterol (Chol) are two antioxidant molecules that effectively protect membranes lipids from free radical oxidative damage. Although the interactions of α-toc/Chol with lipid membranes have been shown, the roles by which it stabilizes membranes under oxidative stress are debated. In this research, the activity of α-toc and Chol in non-oxidized and oxidized lipid bilayers was investigated. Using molecular dynamics (MD) simulations of a PLPC lipid bilayer and a binary combination of PLPC and its oxidation products were done in this work. Two hydroperoxide lipids and two aldehyde lipids were considered as the primary and secondary oxidation products of PLPCs, respectively. α-toc at concentrations of 0-11.1% or Chol at concentrations of 0-50% were applied to the lipid bilayer. The effects of α -toc and Chol on lipid bilayer physical characteristics, as well as their positions and behaviors within the bilayers, were investigated. The result showed that pore development was seen in the aldehyde-containing oxidized lipid bilayers without α-toc and Chol. Pore in aldehyde bilayers is inhibited by the presence of α-toc or Chol at concentrations more than 11%. At either α-toc and Chol concentration, no pores were seen in the PLPC bilayer and the hydroperoxidecontaining oxidized lipid bilayer. Furthermore, increasing cholesterol concentration in the lipid bilayer studies led to a change of the phase state from the liquiddisordered to the liquid-ordered phase for all systems. The free energy profiles were calculated using the umbrella sampling approach to obtain the free energy barrier and to calculate the rate for α-toc/Chol flip-flop within the bilayers. The results demonstrated that in the presence of oxidized lipids, the free energy barrier for both α-toc and Chol flip-flop decreases significantly. The flip-flop rate varies depending on the lipid bilayer type, with the highest rate reported in aldehyde bilayers. The oxidized lipid bilayer is stabilized by α-toc and Chol, which reduces water permeability across the bilayer by restricting the distribution of the oxidized functional groups.

Kasetsart University. Office of the University Library

Address: Bangkok

Email: tdckulib@ku.ac.th

Name: Jirasak Wong-Ekkabut

Role: Thesis Advisor

Created: 2021

Modified: 2025-07-26

Issued: 2025-07-26

วิทยานิพนธ์/Thesis

application/pdf

URL: https://www.lib.ku.ac.th/KUthesis/2564/phansiri-boo-all.pdf

CallNumber: QC173 .P43

eng

DegreeName: Doctor of Philosophy

Level: Doctoral Degraee

Descipline: Physics

Grantor: Kasetsart University

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