Lipoproteins are the main carriers of lipids in the body. HDL is believed to favor cholesterol removal and decrease the risk to develop atherosclerosis and related cardiovascular diseases. Impact of the results. We have developed protocols to understand lipid exchange between lipoproteins and model membranes using neutron reflection. We have studied the exchange processes between HDL and saturated lipids as well as a natural extract, in the presence and absence of cholesterol. Surprisingly, the presence of cholesterol has little effect on lipid exchange but the natural extract behaves significantly different than the saturated lipids. Here we plan to clarify whether this effect is due to the presence of unsaturations, the presence of cyclic structures or the complexity of the lipid mixture in the dPC extract.