Cross-Validation of Simulation and EPR Oximetry Approaches: Membrane Cholesterol Reduces Oxygen Flux

Abstract

Prior EPR oximetry work by Subczynski and colleagues has shown that cholesterol increases membrane resistance to oxygen permeation by 3- to 5-fold when present in a 1:1 ratio with phospholipid. In the current study, we use molecular dynamics simulations to investigate the biophysics of oxygen transport in membranes incorporating cholesterol. The simulations enable cross-validation of the EPR oximetry measurements and the simulations. Further, we have been able to observe oxygen transport near the bilayer surface, which has not been accessible to EPR spin-label probes. We find excellent agreement between the simulation and EPR observations. Our simulations affirm that cholesterol reduces oxygen flux when present at a 1:1 ratio with phospholipid. They further indicate that the bilayer surface in the presence or absence of cholesterol presents greater resistance to permeation than previously observed by EPR.