Abstract:
Oxidative stress on cellular membranes induced by reactive oxygen species is implicated in a number of pathological diseases. The functions of cellular membranes include providing protection for the inner contents of the cell providing structure and allowing communication with the environment. Damage to the membrane may be lethal to cells. Reactive Oxidative Species (ROS) such as free radicals or hydrogen peroxides are produced by many natural oxidative metabolic processes in the cells. These can cause a build up of oxidatively modified membrane molecule which leads to changes in of the physical properties of the membrane such as increased membrane permeability, changes in membrane fluidity, membrane thermotropic phase properties and in protein activity. Techniques have been developed to probe oxidative stress on model membranes, looking at the structural and compositional changes as a function of membrane composition and oxidation conditions. Chromatography and reflectance infrared techniques have identified the increase of oxidation products in the membrane, including aldehydes, ketones, hydroperoxides as well as acyl chains being removed from phospholipids. This is complimented with neutron reflection, small-angle neutron scattering, and electrochemical impedance spectroscopy, which show that under oxidative stress the bilayer thickness seems to be decreasing and water penetration of the bilayer increases, due to defect formation. Finally, preliminary measurements of PLA2 shows that the action of the enzyme on membranes is affected by oxidative stress, but further experiments are required to confirm the details of its role.