The proposed experiments will investigate conformational changes of the 18kDa translocator protein (TSPO) in a lipid bilayer using neutron reflectometry at the solid-liquid interface. The TSPO will be immobilised to a solid surface and a lipid bilayer formed around the protein layer. Preliminary data indicates that interaction of the protein with its ligand PK11195 induces a conformational change, possibly the formation of a channel. The aim of the proposed experiment is to investigate channel formation by using neutrons to detect increased water content in the protein-lipid bilayer as a result of ligand binding. In addition, there is evidence that TSPO acts as a cholesterol recognition site and transporter. Hence, we will also examine changes associated with cholesterol binding. We hope to contribute to a better understanding of structure-function relationships of the TSPO.