With the planned experiments we aim at the precise and unambiguous localization by of Grazing-Incidence Neutron Fluorescence (GINF) of proteins bound to solid-supported lipid membranes. The membranes contain lipids with biotinylated headgroups at defined concentrations to which Gd-labelled streptavidin proteins are specifically bound from the aqueous medium. With the experiments we will explore the sensitivity and spatial resolution with which biological interfaces composed of complex biomolecules can be probed by GINF.