Bacterial and fungal infections of cereal crops pose considerable risk to food security. Pathogenic resistance to conventional fungicides and pesticides is becoming widespread and, therefore, research into naturally occurring alternative antimicrobial agents is timely. Puroindolines are found in wheat endosperm and play a role in seed defence. Puroindoline B interacts with lipids via an unstructured arginine- and tryptophan-rich loop and we have shown that naturally occurring point mutations in this region lead to differences in the mode of lipid binding. We aim to use neutron reflectivity to determine the interfacial layer structure of the peptide binding to model bacterial bilayers. The findings will support our NMR and EPR studies which have highlighted differences in lipid head group dynamics as a result of binding of wild type and mutant puroindoline B.