Thionins are basic, amphiphilic, cysteine-rich and low molecular weight plant defence proteins. These proteins are active against a broad range of phytopathogenic fungi, and can be potentially exploited both in terms of plant fungicides and as future human therapeutic agents. In our current research we aim to investigate the mode of binding of these proteins to model fungal lipid bilayers. We propose to carry out neutron reflectivity experiments at the solid-liquid interface to investigate the influence of lipid bilayer asymmetry on protein binding. The findings from the NR will determine quantitatively the protein-lipid interfacial layer structure and will enable the differences in the proteins' mode of action at membrane surfaces to be investigated.