Neurotransmitter transporters recognize biogenic amines dopamine, serotonin, noradrenalin and γ-amino butyric acid (GABA). They all belong to the family of neurotransmitter:sodium symporters (NSS) that are characterized as secondary active transporters using the Na+ gradient across the membrane as driving force for the transport of its substrate against its own chemical gradient. We would like to use NR to gain detailed structural information on the neutrotransmitter in reconstituted lipid bilayers. What parts of the protein constitute the internal and external gates, respectively, and how do they move in order to translocate the ligands? We hope that neutron reflection will help us to identify what is the positioning of the protein within a lipid bilayer and where ligand binding occurs and whether is translocated, as a function of Na+ concentration.