In situ investigation of the oxidation of a phospholipid monolayer by reactive oxygen species

Abstract

The oxidation of membrane lipids has been widely studied for several decades owing to its significance in biological systems. However, despite its damaging physiological impact and its known role in many diseases, relatively little is understood about the specific structural consequences of oxidative action, particularly in vivo. In this work, a combination of sum-frequency generation spectroscopy, surface tensiometry, and surface-selective infrared spectroscopies are used to gain deeper insight into the oxidation of phospholipids by reactive oxygen species generated in situ. Oxidation is achieved by employing the Fenton reaction to convert physiological levels of H2O2 into OH and HO2 radicals in proximity to the headgroups of lipid monolayers at the air-water interface. By temporally monitoring the surface tension and spectroscopic changes at the interface as the oxidation proceeds, the impact of oxidation on the structure, conformation, and intermolecular interactions within the membrane has been revealed.